sprout: version 0.0.17

feat(boot): basic support for secure boot via shim

Cargo.lock

@@ -116,9 +116,10 @@ dependencies = [
 
 [[package]]
 name = "edera-sprout"
-version = "0.0.15"
+version = "0.0.17"
 dependencies = [
  "anyhow",
+ "bitflags",
  "image",
  "log",
  "serde",

Cargo.toml

@@ -2,13 +2,14 @@
 name = "edera-sprout"
 description = "Modern UEFI bootloader"
 license = "Apache-2.0"
-version = "0.0.15"
+version = "0.0.17"
 homepage = "https://sprout.edera.dev"
 repository = "https://github.com/edera-dev/sprout"
 edition = "2024"
 
 [dependencies]
 anyhow = "1.0.100"
+bitflags = "2.10.0"
 toml = "0.9.8"
 log = "0.4.28"
 

README.md

@@ -6,11 +6,11 @@
 
 </div>
 
-Sprout is an **EXPERIMENTAL** programmable UEFI bootloader written in Rust.
+Sprout is a programmable UEFI bootloader written in Rust.
 
-Sprout is in use at Edera today in development environments and is intended to ship to production soon.
+It is in use at Edera today in development environments and is intended to ship to production soon.
 
-The name "sprout" is derived from our company name "Edera" which means "ivy."
+The name "Sprout" is derived from our company name "Edera" which means "ivy."
 Given that Sprout is the first thing intended to start on an Edera system, the name was apt.
 
 It supports `x86_64` and `ARM64` EFI-capable systems. It is designed to require UEFI and can be chainloaded from an
@@ -18,16 +18,13 @@ existing UEFI bootloader or booted by the hardware directly.
 
 Sprout is licensed under Apache 2.0 and is open to modifications and contributions.
 
-**IMPORTANT WARNING**: Sprout does not support UEFI Secure Boot yet.
-See [this issue](https://github.com/edera-dev/sprout/issues/20) for updates.
-
 ## Background
 
 At [Edera] we make compute isolation technology for a wide variety of environments, often ones we do not fully control.
-Our technology utilizes a hypervisor to boot the host system to provide a new isolation mechanism that works
-with or without hardware virtualization support. To do this we need to inject our hypervisor at boot time.
+Our technology uses a hypervisor to boot the host system to provide a new isolation mechanism that works
+with or without hardware virtualization support. To do this, we need to inject our hypervisor at boot time.
 
-Unfortunately, GRUB, the most common bootloader on Linux systems today, utilizes a shell-script like
+Unfortunately, GRUB, the most common bootloader on Linux systems today, uses a shell-script like
 configuration system. Both the code that runs to generate a GRUB config and the GRUB config
 itself is fully turing complete. This makes modifying boot configuration difficult and error-prone.
 
@@ -52,8 +49,7 @@ simplify installation and usage.
 
 ## Features
 
-NOTE: Currently, Sprout is experimental and is not intended for production use.
-The boot menu mechanism is very rudimentary.
+**NOTE**: Sprout is still in beta.
 
 ### Current
 
@@ -65,13 +61,13 @@ The boot menu mechanism is very rudimentary.
 - [x] Load Linux initrd from disk
 - [x] Basic boot menu
 - [x] BLS autoconfiguration support
+- [x] [Secure Boot support](https://github.com/edera-dev/sprout/issues/20): partial
 
 ### Roadmap
 
 - [ ] [Bootloader interface support](https://github.com/edera-dev/sprout/issues/21)
 - [ ] [BLS specification conformance](https://github.com/edera-dev/sprout/issues/2)
 - [ ] [Full-featured boot menu](https://github.com/edera-dev/sprout/issues/1)
-- [ ] [Secure Boot support](https://github.com/edera-dev/sprout/issues/20): work in progress
 - [ ] [UKI support](https://github.com/edera-dev/sprout/issues/6): partial
 - [ ] [multiboot2 support](https://github.com/edera-dev/sprout/issues/7)
 - [ ] [Linux boot protocol (boot without EFI stub)](https://github.com/edera-dev/sprout/issues/7)

build.rs

@@ -0,0 +1,57 @@
+use std::path::PathBuf;
+use std::{env, fs};
+
+/// The size of the sbat.csv file.
+const SBAT_SIZE: usize = 512;
+
+/// Generate the sbat.csv for the .sbat link section.
+///
+/// We intake a sbat.template.tsv and output a sbat.csv which is included by src/sbat.rs
+fn generate_sbat_csv() {
+    // Notify Cargo that if the Sprout version changes, we need to regenerate the sbat.csv.
+    println!("cargo:rerun-if-env-changed=CARGO_PKG_VERSION");
+
+    // The version of the sprout crate.
+    let sprout_version = env::var("CARGO_PKG_VERSION").expect("CARGO_PKG_VERSION not set");
+
+    // The output directory to place the sbat.csv into.
+    let output_dir = PathBuf::from(env::var("OUT_DIR").expect("OUT_DIR not set"));
+
+    // The output path to the sbat.csv.
+    let output_file = output_dir.join("sbat.csv");
+
+    // The path to the root of the sprout crate.
+    let sprout_root =
+        PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR not set"));
+
+    // The path to the sbat.template.tsv file is in the source directory of the sprout crate.
+    let template_path = sprout_root.join("src/sbat.template.csv");
+
+    // Read the sbat.csv template file.
+    let template = fs::read_to_string(&template_path).expect("unable to read template file");
+
+    // Replace the version placeholder in the template with the actual version.
+    let sbat = template.replace("{version}", &sprout_version);
+
+    // Encode the sbat.csv as bytes.
+    let mut encoded = sbat.as_bytes().to_vec();
+
+    if encoded.len() > SBAT_SIZE {
+        panic!("sbat.csv is too large");
+    }
+
+    // Pad the sbat.csv to the required size.
+    while encoded.len() < SBAT_SIZE {
+        encoded.push(0);
+    }
+
+    // Write the sbat.csv to the output directory.
+    fs::write(&output_file, encoded).expect("unable to write sbat.csv");
+}
+
+/// Build script entry point.
+/// Right now, all we need to do is generate the sbat.csv file.
+fn main() {
+    // Generate the sbat.csv file.
+    generate_sbat_csv();
+}

docs/windows-setup.md

@@ -2,7 +2,7 @@
 
 ## Prerequisites
 
-- Secure Boot disabled
+- Secure Boot is disabled or configured to allow Sprout
 - UEFI Windows installation
 
 ## Step 1: Base Installation

hack/dev/boot/Dockerfile

@@ -7,7 +7,7 @@ RUN export DEBIAN_FRONTEND=noninteractive && apt-get update && apt-get install -
 WORKDIR /work
 COPY sprout.efi /work/${EFI_NAME}.EFI
 COPY sprout.toml /work/SPROUT.TOML
-COPY kernel.efi /work/KERNEL.EFI
+COPY kernel.efi /work/VMLINUZ
 COPY shell.efi /work/SHELL.EFI
 COPY xen.efi /work/XEN.EFI
 COPY xen.cfg /work/XEN.CFG
@@ -24,7 +24,7 @@ RUN truncate -s128MiB sprout.img && \
     mmd -i sprout.img ::/LOADER && \
     mmd -i sprout.img ::/LOADER/ENTRIES && \
     mcopy -i sprout.img ${EFI_NAME}.EFI ::/EFI/BOOT/ && \
-    mcopy -i sprout.img KERNEL.EFI ::/EFI/BOOT/ && \
+    mcopy -i sprout.img VMLINUZ ::/VMLINUZ && \
     mcopy -i sprout.img SHELL.EFI ::/EFI/BOOT/ && \
     mcopy -i sprout.img XEN.EFI ::/EFI/BOOT/ && \
     mcopy -i sprout.img XEN.CFG ::/EFI/BOOT/ && \

hack/dev/configs/all.sprout.toml

@@ -4,10 +4,10 @@ version = 1
 default-entry = "kernel"
 
 [extractors.boot.filesystem-device-match]
-has-item = "\\EFI\\BOOT\\kernel.efi"
+has-item = "\\vmlinuz"
 
 [actions.chainload-kernel]
-chainload.path = "$boot\\EFI\\BOOT\\kernel.efi"
+chainload.path = "$boot\\vmlinuz"
 chainload.options = ["console=hvc0"]
 chainload.linux-initrd = "$boot\\initramfs"
 

hack/dev/configs/bls.conf

@@ -1,4 +1,4 @@
 title Boot Linux
-linux /efi/boot/kernel.efi
+linux /vmlinuz
 options console=hvc0
 initrd /initramfs

hack/dev/configs/kernel.sprout.toml

@@ -5,10 +5,10 @@ default-entry = "kernel"
 menu-timeout = 0
 
 [extractors.boot.filesystem-device-match]
-has-item = "\\EFI\\BOOT\\kernel.efi"
+has-item = "\\vmlinuz"
 
 [actions.chainload-kernel]
-chainload.path = "$boot\\EFI\\BOOT\\kernel.efi"
+chainload.path = "$boot\\vmlinuz"
 chainload.options = ["console=hvc0"]
 chainload.linux-initrd = "$boot\\initramfs"
 

src/actions/chainload.rs

@@ -1,5 +1,6 @@
 use crate::context::SproutContext;
 use crate::integrations::bootloader_interface::BootloaderInterface;
+use crate::integrations::shim::{ShimInput, ShimSupport};
 use crate::utils;
 use crate::utils::media_loader::MediaLoaderHandle;
 use crate::utils::media_loader::constants::linux::LINUX_EFI_INITRD_MEDIA_GUID;
@@ -35,20 +36,14 @@ pub fn chainload(context: Rc<SproutContext>, configuration: &ChainloadConfigurat
 
     // Resolve the path to the image to chainload.
     let resolved = utils::resolve_path(
-        context.root().loaded_image_path()?,
+        Some(context.root().loaded_image_path()?),
         &context.stamp(&configuration.path),
     )
     .context("unable to resolve chainload path")?;
 
-    // Load the image to chainload.
-    let image = uefi::boot::load_image(
-        sprout_image,
-        uefi::boot::LoadImageSource::FromDevicePath {
-            device_path: &resolved.full_path,
-            boot_policy: uefi::proto::BootPolicy::ExactMatch,
-        },
-    )
-    .context("unable to load image")?;
+    // Load the image to chainload using the shim support integration.
+    // It will determine if the image needs to be loaded via the shim or can be loaded directly.
+    let image = ShimSupport::load(sprout_image, ShimInput::ResolvedPath(&resolved))?;
 
     // Open the LoadedImage protocol of the image to chainload.
     let mut loaded_image_protocol = uefi::boot::open_protocol_exclusive::<LoadedImage>(image)
@@ -95,8 +90,9 @@ pub fn chainload(context: Rc<SproutContext>, configuration: &ChainloadConfigurat
     // If an initrd is provided, register it with the EFI stack.
     let mut initrd_handle = None;
     if let Some(linux_initrd) = initrd {
-        let content = utils::read_file_contents(context.root().loaded_image_path()?, &linux_initrd)
-            .context("unable to read linux initrd")?;
+        let content =
+            utils::read_file_contents(Some(context.root().loaded_image_path()?), &linux_initrd)
+                .context("unable to read linux initrd")?;
         let handle =
             MediaLoaderHandle::register(LINUX_EFI_INITRD_MEDIA_GUID, content.into_boxed_slice())
                 .context("unable to register linux initrd")?;

src/actions/edera.rs

@@ -98,7 +98,7 @@ fn register_media_loader_file(
     // Stamp the path to the file.
     let path = context.stamp(path);
     // Read the file contents.
-    let content = utils::read_file_contents(context.root().loaded_image_path()?, &path)
+    let content = utils::read_file_contents(Some(context.root().loaded_image_path()?), &path)
         .context(format!("unable to read {} file", what))?;
     // Register the media loader.
     let handle = MediaLoaderHandle::register(guid, content.into_boxed_slice())

src/actions/splash.rs

@@ -1,7 +1,7 @@
 use crate::context::SproutContext;
 use crate::utils::framebuffer::Framebuffer;
 use crate::utils::read_file_contents;
-use anyhow::{Context, Result};
+use anyhow::{Context, Result, bail};
 use image::imageops::{FilterType, resize};
 use image::math::Rect;
 use image::{DynamicImage, ImageBuffer, ImageFormat, ImageReader, Rgba};
@@ -12,6 +12,8 @@ use std::time::Duration;
 use uefi::boot::ScopedProtocol;
 use uefi::proto::console::gop::GraphicsOutput;
 
+/// We set the default splash time to zero, as this makes it so any logging shows up
+/// on top of the splash and does not hold up the boot process.
 const DEFAULT_SPLASH_TIME: u32 = 0;
 
 /// The configuration of the splash action.
@@ -116,6 +118,11 @@ fn draw(image: DynamicImage) -> Result<()> {
     // Fit the image to the display frame.
     let fit = fit_to_frame(&image, display_frame);
 
+    // If the image is zero-sized, then we should bail with an error.
+    if fit.width == 0 || fit.height == 0 {
+        bail!("calculated frame size is zero");
+    }
+
     // Resize the image to fit the display frame.
     let image = resize_to_fit(&image, fit);
 
@@ -143,7 +150,7 @@ pub fn splash(context: Rc<SproutContext>, configuration: &SplashConfiguration) -
     // Stamp the image path value.
     let image = context.stamp(&configuration.image);
     // Read the image contents.
-    let image = read_file_contents(context.root().loaded_image_path()?, &image)?;
+    let image = read_file_contents(Some(context.root().loaded_image_path()?), &image)?;
     // Decode the image as a PNG.
     let image = ImageReader::with_format(Cursor::new(image), ImageFormat::Png)
         .decode()

src/autoconfigure/bls.rs

@@ -72,7 +72,7 @@ pub fn scan(
 
     // Generate a unique name for the BLS generator and insert the generator into the configuration.
     config.generators.insert(
-        format!("autoconfigure-bls-{}", root_unique_hash),
+        format!("auto-bls-{}", root_unique_hash),
         GeneratorDeclaration {
             bls: Some(generator),
             ..Default::default()

src/autoconfigure/linux.rs

@@ -5,10 +5,11 @@ use crate::entries::EntryDeclaration;
 use crate::generators::GeneratorDeclaration;
 use crate::generators::list::ListConfiguration;
 use crate::utils;
+use crate::utils::vercmp;
 use anyhow::{Context, Result};
 use std::collections::BTreeMap;
 use uefi::CString16;
-use uefi::fs::{FileSystem, Path};
+use uefi::fs::{FileSystem, Path, PathBuf};
 use uefi::proto::device_path::DevicePath;
 use uefi::proto::device_path::text::{AllowShortcuts, DisplayOnly};
 
@@ -17,7 +18,8 @@ const LINUX_CHAINLOAD_ACTION_PREFIX: &str = "linux-chainload-";
 
 /// The locations to scan for kernel pairs.
 /// We will check for symlinks and if this directory is a symlink, we will skip it.
-const SCAN_LOCATIONS: &[&str] = &["/boot", "/"];
+/// The empty string represents the root of the filesystem.
+const SCAN_LOCATIONS: &[&str] = &["\\boot", "\\"];
 
 /// Prefixes of kernel files to scan for.
 const KERNEL_PREFIXES: &[&str] = &["vmlinuz"];
@@ -39,6 +41,9 @@ fn scan_directory(filesystem: &mut FileSystem, path: &str) -> Result<Vec<KernelP
     // All the discovered kernel pairs.
     let mut pairs = Vec::new();
 
+    // We have to special-case the root directory due to path logic in the uefi crate.
+    let is_root = path.is_empty() || path == "\\";
+
     // Construct a filesystem path from the path string.
     let path = CString16::try_from(path).context("unable to convert path to CString16")?;
     let path = Path::new(&path);
@@ -62,6 +67,16 @@ fn scan_directory(filesystem: &mut FileSystem, path: &str) -> Result<Vec<KernelP
         return Ok(pairs);
     };
 
+    // Create a new path used for joining file names below.
+    // All attempts to derive paths for the files in the directory should use this instead.
+    // The uefi crate does not handle push correctly for the root directory.
+    // It will add a second slash, which will cause our path logic to fail.
+    let path_for_join = if is_root {
+        PathBuf::new()
+    } else {
+        path.clone()
+    };
+
     // For each item in the directory, find a kernel.
     for item in directory {
         let item = item.context("unable to read directory item")?;
@@ -74,11 +89,14 @@ fn scan_directory(filesystem: &mut FileSystem, path: &str) -> Result<Vec<KernelP
         // Convert the name from a CString16 to a String.
         let name = item.file_name().to_string();
 
+        // Convert the name to lowercase to make all of this case-insensitive.
+        let name_for_match = name.to_lowercase();
+
         // Find a kernel prefix that matches, if any.
-        let Some(prefix) = KERNEL_PREFIXES
-            .iter()
-            .find(|prefix| name == **prefix || name.starts_with(&format!("{}-", prefix)))
-        else {
+        // This is case-insensitive to ensure we pick up all possibilities.
+        let Some(prefix) = KERNEL_PREFIXES.iter().find(|prefix| {
+            name_for_match == **prefix || name_for_match.starts_with(&format!("{}-", prefix))
+        }) else {
             // Skip over anything that doesn't match a kernel prefix.
             continue;
         };
@@ -96,8 +114,9 @@ fn scan_directory(filesystem: &mut FileSystem, path: &str) -> Result<Vec<KernelP
             let initramfs = format!("{}{}", prefix, suffix);
             let initramfs = CString16::try_from(initramfs.as_str())
                 .context("unable to convert initramfs name to CString16")?;
-            let mut initramfs_path = path.clone();
+            let mut initramfs_path = path_for_join.clone();
             initramfs_path.push(Path::new(&initramfs));
+
             // Check if the initramfs path exists, if it does, break out of the loop.
             if filesystem
                 .try_exists(&initramfs_path)
@@ -108,7 +127,7 @@ fn scan_directory(filesystem: &mut FileSystem, path: &str) -> Result<Vec<KernelP
         };
 
         // Construct a kernel path from the kernel name.
-        let mut kernel = path.clone();
+        let mut kernel = path_for_join.clone();
         kernel.push(Path::new(&item.file_name()));
         let kernel = kernel.to_string();
         let initramfs = matched_initramfs_path.map(|initramfs_path| initramfs_path.to_string());
@@ -152,6 +171,9 @@ pub fn scan(
         return Ok(false);
     }
 
+    // Sort the kernel pairs by kernel version, if it has one, newer kernels first.
+    pairs.sort_by(|a, b| vercmp::compare_versions(&a.kernel, &b.kernel).reverse());
+
     // Generate a unique name for the linux chainload action.
     let chainload_action_name = format!("{}{}", LINUX_CHAINLOAD_ACTION_PREFIX, root_unique_hash,);
 
@@ -181,7 +203,7 @@ pub fn scan(
 
     // Generate a unique name for the Linux generator and insert the generator into the configuration.
     config.generators.insert(
-        format!("autoconfigure-linux-{}", root_unique_hash),
+        format!("auto-linux-{}", root_unique_hash),
         GeneratorDeclaration {
             list: Some(generator),
             ..Default::default()

src/autoconfigure/windows.rs

@@ -49,7 +49,7 @@ pub fn scan(
     let chainload_action_name = format!("{}{}", WINDOWS_CHAINLOAD_ACTION_PREFIX, root_unique_hash,);
 
     // Generate an entry name for Windows.
-    let entry_name = format!("autoconfigure-windows-{}", root_unique_hash,);
+    let entry_name = format!("auto-windows-{}", root_unique_hash,);
 
     // Create an entry for Windows and insert it into the configuration.
     let entry = EntryDeclaration {

src/config/loader.rs

@@ -1,5 +1,6 @@
 use crate::config::{RootConfiguration, latest_version};
 use crate::options::SproutOptions;
+use crate::platform::tpm::PlatformTpm;
 use crate::utils;
 use anyhow::{Context, Result, bail};
 use log::info;
@@ -19,8 +20,17 @@ fn load_raw_config(options: &SproutOptions) -> Result<Vec<u8>> {
     info!("configuration file: {}", options.config);
 
     // Read the contents of the sprout config file.
-    let content = utils::read_file_contents(&path, &options.config)
+    let content = utils::read_file_contents(Some(&path), &options.config)
         .context("unable to read sprout config file")?;
+
+    // Measure the sprout.toml into the TPM, if needed and possible.
+    PlatformTpm::log_event(
+        PlatformTpm::PCR_BOOT_LOADER_CONFIG,
+        &content,
+        "sprout: configuration file",
+    )
+    .context("unable to measure the sprout.toml file into the TPM")?;
+
     // Return the contents of the sprout config file.
     Ok(content)
 }

src/context.rs

@@ -219,6 +219,14 @@ impl SproutContext {
 
     /// Stamps the `text` value with the specified `values` map. The returned value indicates
     /// whether the `text` has been changed and the value that was stamped and changed.
+    ///
+    /// Stamping works like this:
+    /// - Start with the input text.
+    /// - Sort all the keys in reverse length order (longest keys first)
+    /// - For each key, if the key is not empty, replace $KEY in the text.
+    /// - Each follow-up iteration acts upon the last iterations result.
+    /// - We keep track if the text changes during the replacement.
+    /// - We return both whether the text changed during any iteration and the final result.
     fn stamp_values(values: &BTreeMap<String, String>, text: impl AsRef<str>) -> (bool, String) {
         let mut result = text.as_ref().to_string();
         let mut did_change = false;

src/drivers.rs

@@ -1,4 +1,5 @@
 use crate::context::SproutContext;
+use crate::integrations::shim::{ShimInput, ShimSupport};
 use crate::utils;
 use anyhow::{Context, Result};
 use log::info;
@@ -6,7 +7,6 @@ use serde::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::rc::Rc;
 use uefi::boot::SearchType;
-use uefi::proto::device_path::LoadedImageDevicePath;
 
 /// Declares a driver configuration.
 /// Drivers allow extending the functionality of Sprout.
@@ -23,28 +23,17 @@ pub struct DriverDeclaration {
 fn load_driver(context: Rc<SproutContext>, driver: &DriverDeclaration) -> Result<()> {
     // Acquire the handle and device path of the loaded image.
     let sprout_image = uefi::boot::image_handle();
-    let image_device_path_protocol =
-        uefi::boot::open_protocol_exclusive::<LoadedImageDevicePath>(sprout_image)
-            .context("unable to open loaded image device path protocol")?;
 
-    // Get the device path root of the sprout image.
-    let mut full_path = utils::device_path_root(&image_device_path_protocol)?;
-
-    // Push the path of the driver from the root.
-    full_path.push_str(&context.stamp(&driver.path));
-
-    // Convert the path to a device path.
-    let device_path = utils::text_to_device_path(&full_path)?;
-
-    // Load the driver image.
-    let image = uefi::boot::load_image(
-        sprout_image,
-        uefi::boot::LoadImageSource::FromDevicePath {
-            device_path: &device_path,
-            boot_policy: uefi::proto::BootPolicy::ExactMatch,
-        },
+    // Resolve the path to the driver image.
+    let resolved = utils::resolve_path(
+        Some(context.root().loaded_image_path()?),
+        &context.stamp(&driver.path),
     )
-    .context("unable to load image")?;
+    .context("unable to resolve path to driver")?;
+
+    // Load the driver image using the shim support integration.
+    // It will determine if the image needs to be loaded via the shim or can be loaded directly.
+    let image = ShimSupport::load(sprout_image, ShimInput::ResolvedPath(&resolved))?;
 
     // Start the driver image, this is expected to return control to sprout.
     // There is no guarantee that the driver will actually return control as it is

src/entries.rs

@@ -94,6 +94,11 @@ impl BootableEntry {
         self.default = true;
     }
 
+    // Unmark this entry as the default entry.
+    pub fn unmark_default(&mut self) {
+        self.default = false;
+    }
+
     /// Mark this entry as being pinned, which prevents prefixing.
     pub fn mark_pin_name(&mut self) {
         self.pin_name = true;

src/extractors/filesystem_device_match.rs

@@ -98,9 +98,9 @@ pub fn extract(
                 .deref()
                 .to_boxed();
 
-            // Fetch the partition uuid for this filesystem.
+            // Fetch the partition type uuid for this filesystem.
             let partition_type_uuid =
-                utils::partition_guid(&root, utils::PartitionGuidForm::Partition)
+                utils::partition_guid(&root, utils::PartitionGuidForm::PartitionType)
                     .context("unable to fetch the partition uuid of the filesystem")?;
             // Compare the partition type uuid to the parsed uuid.
             // If it does not match, continue to the next filesystem.
@@ -138,14 +138,11 @@ pub fn extract(
             let mut filesystem = FileSystem::new(filesystem);
 
             // Check the metadata of the item.
-            let metadata = filesystem.metadata(Path::new(&want_item));
-
             // Ignore filesystem errors as we can't do anything useful with the error.
-            if metadata.is_err() {
+            let Some(metadata) = filesystem.metadata(Path::new(&want_item)).ok() else {
                 continue;
-            }
+            };
 
-            let metadata = metadata?;
             // Only check directories and files.
             if !(metadata.is_directory() || metadata.is_regular_file()) {
                 continue;

src/generators/bls.rs

@@ -2,8 +2,10 @@ use crate::context::SproutContext;
 use crate::entries::{BootableEntry, EntryDeclaration};
 use crate::generators::bls::entry::BlsEntry;
 use crate::utils;
+use crate::utils::vercmp;
 use anyhow::{Context, Result};
 use serde::{Deserialize, Serialize};
+use std::cmp::Ordering;
 use std::rc::Rc;
 use std::str::FromStr;
 use uefi::cstr16;
@@ -40,6 +42,60 @@ fn quirk_initrd_remove_tuned(input: String) -> String {
     input.replace("$tuned_initrd", "").trim().to_string()
 }
 
+/// Sorts two entries according to the BLS sort system.
+/// Reference: https://uapi-group.org/specifications/specs/boot_loader_specification/#sorting
+fn sort_entries(a: &(BlsEntry, BootableEntry), b: &(BlsEntry, BootableEntry)) -> Ordering {
+    // Grab the components of both entries.
+    let (a_bls, a_boot) = a;
+    let (b_bls, b_boot) = b;
+
+    // Grab the sort keys from both entries.
+    let a_sort_key = a_bls.sort_key();
+    let b_sort_key = b_bls.sort_key();
+
+    // Compare the sort keys of both entries.
+    match a_sort_key.cmp(&b_sort_key) {
+        // If A and B sort keys are equal, sort by machine-id.
+        Ordering::Equal => {
+            // Grab the machine-id from both entries.
+            let a_machine_id = a_bls.machine_id();
+            let b_machine_id = b_bls.machine_id();
+
+            // Compare the machine-id of both entries.
+            match a_machine_id.cmp(&b_machine_id) {
+                // If both machine-id values are equal, sort by version.
+                Ordering::Equal => {
+                    // Grab the version from both entries.
+                    let a_version = a_bls.version();
+                    let b_version = b_bls.version();
+
+                    // Compare the version of both entries, sorting newer versions first.
+                    match vercmp::compare_versions_optional(
+                        a_version.as_deref(),
+                        b_version.as_deref(),
+                    )
+                    .reverse()
+                    {
+                        // If both versions are equal, sort by file name in reverse order.
+                        Ordering::Equal => {
+                            // Grab the file name from both entries.
+                            let a_name = a_boot.name();
+                            let b_name = b_boot.name();
+
+                            // Compare the file names of both entries, sorting newer entries first.
+                            vercmp::compare_versions(a_name, b_name).reverse()
+                        }
+                        other => other,
+                    }
+                }
+                other => other,
+            }
+        }
+
+        other => other,
+    }
+}
+
 /// Generates entries from the BLS entries directory using the specified `bls` configuration and
 /// `context`. The BLS conversion is best-effort and will ignore any unsupported entries.
 pub fn generate(context: Rc<SproutContext>, bls: &BlsConfiguration) -> Result<Vec<BootableEntry>> {
@@ -49,7 +105,7 @@ pub fn generate(context: Rc<SproutContext>, bls: &BlsConfiguration) -> Result<Ve
     let path = context.stamp(&bls.path);
 
     // Resolve the path to the BLS directory.
-    let bls_resolved = utils::resolve_path(context.root().loaded_image_path()?, &path)
+    let bls_resolved = utils::resolve_path(Some(context.root().loaded_image_path()?), &path)
         .context("unable to resolve bls path")?;
 
     // Construct a filesystem path to the BLS entries directory.
@@ -93,6 +149,11 @@ pub fn generate(context: Rc<SproutContext>, bls: &BlsConfiguration) -> Result<Ve
         // Remove the .conf extension.
         name.truncate(name.len() - 5);
 
+        // Skip over files that are named just ".conf" as they are not valid entry files.
+        if name.is_empty() {
+            continue;
+        }
+
         // Create a mutable path so we can append the file name to produce the full path.
         let mut full_entry_path = entries_path.to_path_buf();
         full_entry_path.push(entry.file_name());
@@ -116,20 +177,33 @@ pub fn generate(context: Rc<SproutContext>, bls: &BlsConfiguration) -> Result<Ve
         // Produce a new sprout context for the entry with the extracted values.
         let mut context = context.fork();
 
-        let title = entry.title().unwrap_or_else(|| name.clone());
+        let title_base = entry.title().unwrap_or_else(|| name.clone());
         let chainload = entry.chainload_path().unwrap_or_default();
         let options = entry.options().unwrap_or_default();
+        let version = entry.version().unwrap_or_default();
+        let machine_id = entry.machine_id().unwrap_or_default();
 
         // Put the initrd through a quirk modifier to support Fedora.
         let initrd = quirk_initrd_remove_tuned(entry.initrd_path().unwrap_or_default());
 
-        context.set("title", title);
+        // Combine the title with the version if a version is present, except if it already contains it.
+        // Sometimes BLS will have a version in the title already, and this makes it unique.
+        let title_full = if !version.is_empty() && !title_base.contains(&version) {
+            format!("{} {}", title_base, version)
+        } else {
+            title_base.clone()
+        };
+
+        context.set("title-base", title_base);
+        context.set("title", title_full);
         context.set("chainload", chainload);
         context.set("options", options);
         context.set("initrd", initrd);
+        context.set("version", version);
+        context.set("machine-id", machine_id);
 
         // Produce a new bootable entry.
-        let mut entry = BootableEntry::new(
+        let mut boot = BootableEntry::new(
             name,
             bls.entry.title.clone(),
             context.freeze(),
@@ -139,11 +213,15 @@ pub fn generate(context: Rc<SproutContext>, bls: &BlsConfiguration) -> Result<Ve
         // Pin the entry name to prevent prefixing.
         // This is needed as the bootloader interface requires the name to be
         // the same as the entry file name, minus the .conf extension.
-        entry.mark_pin_name();
+        boot.mark_pin_name();
 
-        // Add the entry to the list with a frozen context.
-        entries.push(entry);
+        // Add the BLS entry to the list, along with the bootable entry.
+        entries.push((entry, boot));
     }
 
-    Ok(entries)
+    // Sort all the entries according to the BLS sort system.
+    entries.sort_by(sort_entries);
+
+    // Collect all the bootable entries and return them.
+    Ok(entries.into_iter().map(|(_, boot)| boot).collect())
 }

src/generators/bls/entry.rs

@@ -15,6 +15,12 @@ pub struct BlsEntry {
     pub initrd: Option<String>,
     /// The path to an EFI image.
     pub efi: Option<String>,
+    /// The sort key for the entry.
+    pub sort_key: Option<String>,
+    /// The version of the entry.
+    pub version: Option<String>,
+    /// The machine id of the entry.
+    pub machine_id: Option<String>,
 }
 
 /// Parser for a BLS entry.
@@ -30,6 +36,9 @@ impl FromStr for BlsEntry {
         let mut linux: Option<String> = None;
         let mut initrd: Option<String> = None;
         let mut efi: Option<String> = None;
+        let mut sort_key: Option<String> = None;
+        let mut version: Option<String> = None;
+        let mut machine_id: Option<String> = None;
 
         // Iterate over each line in the input and parse it.
         for line in input.lines() {
@@ -74,6 +83,18 @@ impl FromStr for BlsEntry {
                     efi = Some(value.trim().to_string());
                 }
 
+                "sort-key" => {
+                    sort_key = Some(value.trim().to_string());
+                }
+
+                "version" => {
+                    version = Some(value.trim().to_string());
+                }
+
+                "machine-id" => {
+                    machine_id = Some(value.trim().to_string());
+                }
+
                 // Ignore any other key.
                 _ => {
                     continue;
@@ -88,6 +109,9 @@ impl FromStr for BlsEntry {
             linux,
             initrd,
             efi,
+            sort_key,
+            version,
+            machine_id,
         })
     }
 }
@@ -125,4 +149,19 @@ impl BlsEntry {
     pub fn title(&self) -> Option<String> {
         self.title.clone()
     }
+
+    /// Fetches the sort key of the entry, if any.
+    pub fn sort_key(&self) -> Option<String> {
+        self.sort_key.clone()
+    }
+
+    /// Fetches the version of the entry, if any.
+    pub fn version(&self) -> Option<String> {
+        self.version.clone()
+    }
+
+    /// Fetches the machine id of the entry, if any.
+    pub fn machine_id(&self) -> Option<String> {
+        self.machine_id.clone()
+    }
 }

src/generators/list.rs

@@ -18,7 +18,7 @@ pub struct ListConfiguration {
     pub values: Vec<BTreeMap<String, String>>,
 }
 
-/// Generates a set of entries using the specified `matrix` configuration in the `context`.
+/// Generates a set of entries using the specified `list` configuration in the `context`.
 pub fn generate(
     context: Rc<SproutContext>,
     list: &ListConfiguration,

src/integrations.rs

@@ -1,2 +1,4 @@
 /// Implements support for the bootloader interface specification.
 pub mod bootloader_interface;
+/// Implements support for the shim loader application for Secure Boot.
+pub mod shim;

src/integrations/bootloader_interface.rs

@@ -1,19 +1,53 @@
+use crate::integrations::bootloader_interface::bitflags::LoaderFeatures;
 use crate::platform::timer::PlatformTimer;
 use crate::utils::device_path_subpath;
+use crate::utils::variables::{VariableClass, VariableController};
 use anyhow::{Context, Result};
 use uefi::proto::device_path::DevicePath;
-use uefi::{CString16, Guid, guid};
-use uefi_raw::table::runtime::{VariableAttributes, VariableVendor};
+use uefi::{Guid, guid};
+use uefi_raw::table::runtime::VariableVendor;
+
+/// bitflags: LoaderFeatures bitflags.
+mod bitflags;
 
 /// The name of the bootloader to tell the system.
 const LOADER_NAME: &str = "Sprout";
 
+/// Represents the configured timeout for the bootloader interface.
+pub enum BootloaderInterfaceTimeout {
+    /// Force the menu to be shown.
+    MenuForce,
+    /// Hide the menu.
+    MenuHidden,
+    /// Disable the menu.
+    MenuDisabled,
+    /// Set a timeout for the menu.
+    Timeout(u64),
+    /// Timeout is unspecified.
+    Unspecified,
+}
+
 /// Bootloader Interface support.
 pub struct BootloaderInterface;
 
 impl BootloaderInterface {
     /// Bootloader Interface GUID from https://systemd.io/BOOT_LOADER_INTERFACE
-    const VENDOR: VariableVendor = VariableVendor(guid!("4a67b082-0a4c-41cf-b6c7-440b29bb8c4f"));
+    const VENDOR: VariableController = VariableController::new(VariableVendor(guid!(
+        "4a67b082-0a4c-41cf-b6c7-440b29bb8c4f"
+    )));
+
+    /// The feature we support in Sprout.
+    fn features() -> LoaderFeatures {
+        LoaderFeatures::Xbootldr
+            | LoaderFeatures::LoadDriver
+            | LoaderFeatures::Tpm2ActivePcrBanks
+            | LoaderFeatures::RetainShim
+            | LoaderFeatures::ConfigTimeout
+            | LoaderFeatures::ConfigTimeoutOneShot
+            | LoaderFeatures::MenuDisable
+            | LoaderFeatures::EntryDefault
+            | LoaderFeatures::EntryOneShot
+    }
 
     /// Tell the system that Sprout was initialized at the current time.
     pub fn mark_init(timer: &PlatformTimer) -> Result<()> {
@@ -27,7 +61,7 @@ impl BootloaderInterface {
 
     /// Tell the system that Sprout is about to display the menu.
     pub fn mark_menu(timer: &PlatformTimer) -> Result<()> {
-        Self::mark_time("LoaderTimeMenuUsec", timer)
+        Self::mark_time("LoaderTimeMenuUSec", timer)
     }
 
     /// Tell the system about the current time as measured by the platform timer.
@@ -35,23 +69,52 @@ impl BootloaderInterface {
     fn mark_time(key: &str, timer: &PlatformTimer) -> Result<()> {
         // Measure the elapsed time since the hardware timer was started.
         let elapsed = timer.elapsed_since_lifetime();
-        Self::set_cstr16(key, &elapsed.as_micros().to_string())
+        Self::VENDOR.set_cstr16(
+            key,
+            &elapsed.as_micros().to_string(),
+            VariableClass::BootAndRuntimeTemporary,
+        )
     }
 
-    /// Tell the system what loader is being used.
+    /// Tell the system what loader is being used and our features.
     pub fn set_loader_info() -> Result<()> {
-        Self::set_cstr16("LoaderInfo", LOADER_NAME)
+        // Set the LoaderInfo variable with the name of the loader.
+        Self::VENDOR
+            .set_cstr16(
+                "LoaderInfo",
+                LOADER_NAME,
+                VariableClass::BootAndRuntimeTemporary,
+            )
+            .context("unable to set loader info variable")?;
+
+        // Set the LoaderFeatures variable with the features we support.
+        Self::VENDOR
+            .set_u64le(
+                "LoaderFeatures",
+                Self::features().bits(),
+                VariableClass::BootAndRuntimeTemporary,
+            )
+            .context("unable to set loader features variable")?;
+        Ok(())
     }
 
     /// Tell the system the relative path to the partition root of the current bootloader.
     pub fn set_loader_path(path: &DevicePath) -> Result<()> {
         let subpath = device_path_subpath(path).context("unable to get loader path subpath")?;
-        Self::set_cstr16("LoaderImageIdentifier", &subpath)
+        Self::VENDOR.set_cstr16(
+            "LoaderImageIdentifier",
+            &subpath,
+            VariableClass::BootAndRuntimeTemporary,
+        )
     }
 
     /// Tell the system what the partition GUID of the ESP Sprout was booted from is.
     pub fn set_partition_guid(guid: &Guid) -> Result<()> {
-        Self::set_cstr16("LoaderDevicePartUUID", &guid.to_string())
+        Self::VENDOR.set_cstr16(
+            "LoaderDevicePartUUID",
+            &guid.to_string(),
+            VariableClass::BootAndRuntimeTemporary,
+        )
     }
 
     /// Tell the system what boot entries are available.
@@ -66,60 +129,186 @@ impl BootloaderInterface {
                 .encode_utf16()
                 .flat_map(|c| c.to_le_bytes())
                 .collect::<Vec<u8>>();
-            // Write the bytes (including the null terminator) into the data buffer.
+            // Write the bytes into the data buffer.
             data.extend_from_slice(&encoded);
+            // Add a null terminator to the end of the entry.
+            data.extend_from_slice(&[0, 0]);
         }
-        Self::set("LoaderEntries", &data)
-    }
 
-    /// Tell the system what the default boot entry is.
-    pub fn set_default_entry(entry: String) -> Result<()> {
-        Self::set_cstr16("LoaderEntryDefault", &entry)
+        // If no data was generated, we will do nothing.
+        if data.is_empty() {
+            return Ok(());
+        }
+
+        Self::VENDOR.set(
+            "LoaderEntries",
+            &data,
+            VariableClass::BootAndRuntimeTemporary,
+        )
     }
 
     /// Tell the system what the selected boot entry is.
     pub fn set_selected_entry(entry: String) -> Result<()> {
-        Self::set_cstr16("LoaderEntrySelected", &entry)
+        Self::VENDOR.set_cstr16(
+            "LoaderEntrySelected",
+            &entry,
+            VariableClass::BootAndRuntimeTemporary,
+        )
     }
 
     /// Tell the system about the UEFI firmware we are running on.
     pub fn set_firmware_info() -> Result<()> {
+        // Access the firmware revision.
+        let firmware_revision = uefi::system::firmware_revision();
+
+        // Access the UEFI revision.
+        let uefi_revision = uefi::system::uefi_revision();
+
         // Format the firmware information string into something human-readable.
         let firmware_info = format!(
             "{} {}.{:02}",
             uefi::system::firmware_vendor(),
-            uefi::system::firmware_revision() >> 16,
-            uefi::system::firmware_revision() & 0xFFFFF,
+            firmware_revision >> 16,
+            firmware_revision & 0xffff,
         );
-        Self::set_cstr16("LoaderFirmwareInfo", &firmware_info)?;
+        Self::VENDOR.set_cstr16(
+            "LoaderFirmwareInfo",
+            &firmware_info,
+            VariableClass::BootAndRuntimeTemporary,
+        )?;
 
         // Format the firmware revision into something human-readable.
-        let firmware_type = format!("UEFI {:02}", uefi::system::firmware_revision());
-        Self::set_cstr16("LoaderFirmwareType", &firmware_type)
+        let firmware_type = format!(
+            "UEFI {}.{:02}",
+            uefi_revision.major(),
+            uefi_revision.minor()
+        );
+        Self::VENDOR.set_cstr16(
+            "LoaderFirmwareType",
+            &firmware_type,
+            VariableClass::BootAndRuntimeTemporary,
+        )
     }
 
-    /// The [VariableAttributes] for bootloader interface variables.
-    fn attributes() -> VariableAttributes {
-        VariableAttributes::BOOTSERVICE_ACCESS | VariableAttributes::RUNTIME_ACCESS
+    /// Tell the system what the number of active PCR banks is.
+    /// If this is zero, that is okay.
+    pub fn set_tpm2_active_pcr_banks(value: u32) -> Result<()> {
+        // Format the value into the specification format.
+        let value = format!("0x{:08x}", value);
+        Self::VENDOR.set_cstr16(
+            "LoaderTpm2ActivePcrBanks",
+            &value,
+            VariableClass::BootAndRuntimeTemporary,
+        )
     }
 
-    /// Set a bootloader interface variable specified by `key` to `value`.
-    fn set(key: &str, value: &[u8]) -> Result<()> {
-        let name =
-            CString16::try_from(key).context("unable to convert variable name to CString16")?;
-        uefi::runtime::set_variable(&name, &Self::VENDOR, Self::attributes(), value)
-            .with_context(|| format!("unable to set efi variable {}", key))?;
-        Ok(())
+    /// Retrieve the timeout value from the bootloader interface, using the specified `key`.
+    /// `remove` indicates whether, when found, we remove the variable.
+    fn get_timeout_value(key: &str, remove: bool) -> Result<Option<BootloaderInterfaceTimeout>> {
+        // Retrieve the timeout value from the bootloader interface.
+        let Some(value) = Self::VENDOR
+            .get_cstr16(key)
+            .context("unable to get timeout value")?
+        else {
+            return Ok(None);
+        };
+
+        // If we reach here, we know the value was specified.
+        // If `remove` is true, remove the variable.
+        if remove {
+            Self::VENDOR
+                .remove(key)
+                .context("unable to remove timeout variable")?;
+        }
+
+        // If the value is empty, return Unspecified.
+        if value.is_empty() {
+            return Ok(Some(BootloaderInterfaceTimeout::Unspecified));
+        }
+
+        // If the value is "menu-force", return MenuForce.
+        if value == "menu-force" {
+            return Ok(Some(BootloaderInterfaceTimeout::MenuForce));
+        }
+
+        // If the value is "menu-hidden", return MenuHidden.
+        if value == "menu-hidden" {
+            return Ok(Some(BootloaderInterfaceTimeout::MenuHidden));
+        }
+
+        // If the value is "menu-disabled", return MenuDisabled.
+        if value == "menu-disabled" {
+            return Ok(Some(BootloaderInterfaceTimeout::MenuDisabled));
+        }
+
+        // Parse the value as a u64 to decode an numeric value.
+        let value = value
+            .parse::<u64>()
+            .context("unable to parse timeout value")?;
+
+        // The specification says that a value of 0 means that the menu should be hidden.
+        if value == 0 {
+            return Ok(Some(BootloaderInterfaceTimeout::MenuHidden));
+        }
+
+        // If we reach here, we know it must be a real timeout value.
+        Ok(Some(BootloaderInterfaceTimeout::Timeout(value)))
     }
 
-    /// Set a bootloader interface variable specified by `key` to `value`, converting the value to
-    /// a [CString16].
-    fn set_cstr16(key: &str, value: &str) -> Result<()> {
-        // Encode the value as a CString16 little endian.
-        let encoded = value
-            .encode_utf16()
-            .flat_map(|c| c.to_le_bytes())
-            .collect::<Vec<u8>>();
-        Self::set(key, &encoded)
+    /// Get the timeout from the bootloader interface.
+    /// This indicates how the menu should behave.
+    /// If no values are set, Unspecified is returned.
+    pub fn get_timeout() -> Result<BootloaderInterfaceTimeout> {
+        // Attempt to acquire the value of the LoaderConfigTimeoutOneShot variable.
+        // This should take precedence over the LoaderConfigTimeout variable.
+        let oneshot = Self::get_timeout_value("LoaderConfigTimeoutOneShot", true)
+            .context("unable to check for LoaderConfigTimeoutOneShot variable")?;
+
+        // If oneshot was found, return it.
+        if let Some(oneshot) = oneshot {
+            return Ok(oneshot);
+        }
+
+        // Attempt to acquire the value of the LoaderConfigTimeout variable.
+        // This will be used if the LoaderConfigTimeoutOneShot variable is not set.
+        let direct = Self::get_timeout_value("LoaderConfigTimeout", false)
+            .context("unable to check for LoaderConfigTimeout variable")?;
+
+        // If direct was found, return it.
+        if let Some(direct) = direct {
+            return Ok(direct);
+        }
+
+        // If we reach here, we know that neither variable was set.
+        // We provide the unspecified value instead.
+        Ok(BootloaderInterfaceTimeout::Unspecified)
+    }
+
+    /// Get the default entry set by the bootloader interface.
+    pub fn get_default_entry() -> Result<Option<String>> {
+        Self::VENDOR
+            .get_cstr16("LoaderEntryDefault")
+            .context("unable to get default entry from bootloader interface")
+    }
+
+    /// Get the oneshot entry set by the bootloader interface.
+    /// This should be the entry we boot.
+    pub fn get_oneshot_entry() -> Result<Option<String>> {
+        // Acquire the value of the LoaderEntryOneShot variable.
+        // If it is not set, return None.
+        let Some(value) = Self::VENDOR
+            .get_cstr16("LoaderEntryOneShot")
+            .context("unable to get oneshot entry from bootloader interface")?
+        else {
+            return Ok(None);
+        };
+
+        // Remove the oneshot entry from the bootloader interface.
+        Self::VENDOR
+            .remove("LoaderEntryOneShot")
+            .context("unable to remove oneshot entry")?;
+
+        // Return the oneshot value.
+        Ok(Some(value))
     }
 }

src/integrations/bootloader_interface/bitflags.rs

@@ -0,0 +1,46 @@
+use bitflags::bitflags;
+
+bitflags! {
+    /// Feature bitflags for the bootloader interface.
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+    pub struct LoaderFeatures: u64 {
+        /// Bootloader supports LoaderConfigTimeout.
+        const ConfigTimeout = 1 << 0;
+        /// Bootloader supports LoaderConfigTimeoutOneShot.
+        const ConfigTimeoutOneShot = 1 << 1;
+        /// Bootloader supports LoaderEntryDefault.
+        const EntryDefault = 1 << 2;
+        /// Bootloader supports LoaderEntryOneShot.
+        const EntryOneShot = 1 << 3;
+        /// Bootloader supports boot counting.
+        const BootCounting = 1 << 4;
+        /// Bootloader supports detection from XBOOTLDR partitions.
+        const Xbootldr = 1 << 5;
+        /// Bootloader supports the handling of random seeds.
+        const RandomSeed = 1 << 6;
+        /// Bootloader supports loading drivers.
+        const LoadDriver = 1 << 7;
+        /// Bootloader supports sort keys.
+        const SortKey = 1 << 8;
+        /// Bootloader supports saved entries.
+        const SavedEntry = 1 << 9;
+        /// Bootloader supports device trees.
+        const DeviceTree = 1 << 10;
+        /// Bootloader supports secure boot enroll.
+        const SecureBootEnroll = 1 << 11;
+        /// Bootloader retains the shim.
+        const RetainShim = 1 << 12;
+        /// Bootloader supports disabling the menu via the menu timeout variable.
+        const MenuDisable = 1 << 13;
+        /// Bootloader supports multi-profile UKI.
+        const MultiProfileUki = 1 << 14;
+        /// Bootloader reports URLs.
+        const ReportUrl = 1 << 15;
+        /// Bootloader supports type-1 UKIs.
+        const Type1Uki = 1 << 16;
+        /// Bootloader supports type-1 UKI urls.
+        const Type1UkiUrl = 1 << 17;
+        /// Bootloader indicates TPM2 active PCR banks.
+        const Tpm2ActivePcrBanks = 1 << 18;
+    }
+}

src/integrations/shim.rs

@@ -0,0 +1,316 @@
+use crate::integrations::shim::hook::SecurityHook;
+use crate::secure::SecureBoot;
+use crate::utils;
+use crate::utils::ResolvedPath;
+use crate::utils::variables::{VariableClass, VariableController};
+use anyhow::{Context, Result, anyhow, bail};
+use log::warn;
+use std::ffi::c_void;
+use std::pin::Pin;
+use uefi::Handle;
+use uefi::boot::LoadImageSource;
+use uefi::proto::device_path::text::{AllowShortcuts, DisplayOnly};
+use uefi::proto::device_path::{DevicePath, FfiDevicePath};
+use uefi::proto::unsafe_protocol;
+use uefi_raw::table::runtime::VariableVendor;
+use uefi_raw::{Guid, Status, guid};
+
+/// Security hook support.
+mod hook;
+
+/// Support for the shim loader application for Secure Boot.
+pub struct ShimSupport;
+
+/// Input to the shim mechanisms.
+pub enum ShimInput<'a> {
+    /// Data loaded into a buffer and ready to be verified, owned.
+    OwnedDataBuffer(Option<&'a ResolvedPath>, Pin<Box<[u8]>>),
+    /// Data loaded into a buffer and ready to be verified.
+    DataBuffer(Option<&'a ResolvedPath>, &'a [u8]),
+    /// Low-level data buffer provided by the security hook.
+    SecurityHookBuffer(Option<*const FfiDevicePath>, &'a [u8]),
+    /// Low-level owned data buffer provided by the security hook.
+    SecurityHookOwnedBuffer(Option<*const FfiDevicePath>, Pin<Box<[u8]>>),
+    /// Low-level path provided by the security hook.
+    SecurityHookPath(*const FfiDevicePath),
+    /// Data is provided as a resolved path. We will need to load the data to verify it.
+    /// The output will them return the loaded data.
+    ResolvedPath(&'a ResolvedPath),
+}
+
+impl<'a> ShimInput<'a> {
+    /// Accesses the buffer behind the shim input, if available.
+    pub fn buffer(&self) -> Option<&[u8]> {
+        match self {
+            ShimInput::OwnedDataBuffer(_, data) => Some(data),
+            ShimInput::SecurityHookOwnedBuffer(_, data) => Some(data),
+            ShimInput::SecurityHookBuffer(_, data) => Some(data),
+            ShimInput::SecurityHookPath(_) => None,
+            ShimInput::DataBuffer(_, data) => Some(data),
+            ShimInput::ResolvedPath(_) => None,
+        }
+    }
+
+    /// Accesses the full device path to the input.
+    pub fn file_path(&self) -> Option<&DevicePath> {
+        match self {
+            ShimInput::OwnedDataBuffer(path, _) => path.as_ref().map(|it| it.full_path.as_ref()),
+            ShimInput::DataBuffer(path, _) => path.as_ref().map(|it| it.full_path.as_ref()),
+            ShimInput::SecurityHookBuffer(path, _) => {
+                path.map(|it| unsafe { DevicePath::from_ffi_ptr(it) })
+            }
+            ShimInput::SecurityHookPath(path) => unsafe { Some(DevicePath::from_ffi_ptr(*path)) },
+            ShimInput::ResolvedPath(path) => Some(path.full_path.as_ref()),
+            ShimInput::SecurityHookOwnedBuffer(path, _) => {
+                path.map(|it| unsafe { DevicePath::from_ffi_ptr(it) })
+            }
+        }
+    }
+
+    /// Converts this input into an owned data buffer, where the data is loaded.
+    /// For ResolvedPath, this will read the file.
+    pub fn into_owned_data_buffer(self) -> Result<ShimInput<'a>> {
+        match self {
+            ShimInput::OwnedDataBuffer(root, data) => Ok(ShimInput::OwnedDataBuffer(root, data)),
+
+            ShimInput::DataBuffer(root, data) => Ok(ShimInput::OwnedDataBuffer(
+                root,
+                Box::into_pin(data.to_vec().into_boxed_slice()),
+            )),
+
+            ShimInput::SecurityHookPath(ffi_path) => {
+                // Acquire the file path.
+                let Some(path) = self.file_path() else {
+                    bail!("unable to convert security hook path to device path");
+                };
+                // Convert the underlying path to a string.
+                let path = path
+                    .to_string(DisplayOnly(false), AllowShortcuts(false))
+                    .context("unable to convert device path to string")?;
+                let path = utils::resolve_path(None, &path.to_string())
+                    .context("unable to resolve path")?;
+                // Read the file path.
+                let data = path.read_file()?;
+                Ok(ShimInput::SecurityHookOwnedBuffer(
+                    Some(ffi_path),
+                    Box::into_pin(data.to_vec().into_boxed_slice()),
+                ))
+            }
+
+            ShimInput::SecurityHookBuffer(_, _) => {
+                bail!("unable to convert security hook buffer to owned data buffer")
+            }
+
+            ShimInput::ResolvedPath(path) => {
+                // Read the file path.
+                let data = path.read_file()?;
+                Ok(ShimInput::OwnedDataBuffer(
+                    Some(path),
+                    Box::into_pin(data.to_vec().into_boxed_slice()),
+                ))
+            }
+
+            ShimInput::SecurityHookOwnedBuffer(path, data) => {
+                Ok(ShimInput::SecurityHookOwnedBuffer(path, data))
+            }
+        }
+    }
+}
+
+/// Output of the shim verification function.
+/// Since the shim needs to load the data from disk, we will optimize by using that as the data
+/// to actually boot.
+pub enum ShimVerificationOutput {
+    /// The verification failed.
+    VerificationFailed(Status),
+    /// The data provided to the verifier was already a buffer.
+    VerifiedDataNotLoaded,
+    /// Verifying the data resulted in loading the data from the source.
+    /// This contains the data that was loaded, so it won't need to be loaded again.
+    VerifiedDataBuffer(Vec<u8>),
+}
+
+/// The shim lock protocol as defined by the shim loader application.
+#[unsafe_protocol(ShimSupport::SHIM_LOCK_GUID)]
+struct ShimLockProtocol {
+    /// Verify the data in `buffer` with the size `buffer_size` to determine if it is valid.
+    /// NOTE: On x86_64, this function uses SYSV calling conventions. On aarch64 it uses the
+    /// efiapi calling convention. This is truly wild, but you can verify it yourself by
+    /// looking at: https://github.com/rhboot/shim/blob/15.8/shim.h#L207-L212
+    /// There is no calling convention declared like there should be.
+    #[cfg(target_arch = "x86_64")]
+    pub shim_verify: unsafe extern "sysv64" fn(buffer: *const c_void, buffer_size: u32) -> Status,
+    #[cfg(target_arch = "aarch64")]
+    pub shim_verify: unsafe extern "efiapi" fn(buffer: *const c_void, buffer_size: u32) -> Status,
+    /// Unused function that is defined by the shim.
+    _generate_header: *mut c_void,
+    /// Unused function that is defined by the shim.
+    _read_header: *mut c_void,
+}
+
+impl ShimSupport {
+    /// Variable controller for the shim lock.
+    const SHIM_LOCK_VARIABLES: VariableController =
+        VariableController::new(VariableVendor(Self::SHIM_LOCK_GUID));
+
+    /// GUID for the shim lock protocol.
+    const SHIM_LOCK_GUID: Guid = guid!("605dab50-e046-4300-abb6-3dd810dd8b23");
+    /// GUID for the shim image loader protocol.
+    const SHIM_IMAGE_LOADER_GUID: Guid = guid!("1f492041-fadb-4e59-9e57-7cafe73a55ab");
+
+    /// Determines whether the shim is loaded.
+    pub fn loaded() -> Result<bool> {
+        Ok(utils::find_handle(&Self::SHIM_LOCK_GUID)
+            .context("unable to find shim lock protocol")?
+            .is_some())
+    }
+
+    /// Determines whether the shim loader is available.
+    pub fn loader_available() -> Result<bool> {
+        Ok(utils::find_handle(&Self::SHIM_IMAGE_LOADER_GUID)
+            .context("unable to find shim image loader protocol")?
+            .is_some())
+    }
+
+    /// Use the shim to validate the `input`, returning [ShimVerificationOutput] when complete.
+    pub fn verify(input: ShimInput) -> Result<ShimVerificationOutput> {
+        // Acquire the handle to the shim lock protocol.
+        let handle = utils::find_handle(&Self::SHIM_LOCK_GUID)
+            .context("unable to find shim lock protocol")?
+            .ok_or_else(|| anyhow!("unable to find shim lock protocol"))?;
+        // Acquire the protocol exclusively to the shim lock.
+        let protocol = uefi::boot::open_protocol_exclusive::<ShimLockProtocol>(handle)
+            .context("unable to open shim lock protocol")?;
+
+        // If the input type is a device path, we need to load the data.
+        let maybe_loaded_data = match input {
+            ShimInput::OwnedDataBuffer(_, _data) => {
+                bail!("owned data buffer is not supported in the verification function");
+            }
+            ShimInput::SecurityHookBuffer(_, _) => None,
+            ShimInput::SecurityHookOwnedBuffer(_, _) => None,
+            ShimInput::DataBuffer(_, _) => None,
+            ShimInput::ResolvedPath(path) => Some(path.read_file()?),
+            ShimInput::SecurityHookPath(_) => None,
+        };
+
+        // Convert the input to a buffer.
+        // If the input provides the data buffer, we will use that.
+        // Otherwise, we will use the data loaded by this function.
+        let buffer = match &input {
+            ShimInput::OwnedDataBuffer(_root, data) => data,
+            ShimInput::DataBuffer(_root, data) => *data,
+            ShimInput::ResolvedPath(_path) => maybe_loaded_data
+                .as_deref()
+                .context("expected data buffer to be loaded already")?,
+            ShimInput::SecurityHookBuffer(_, data) => data,
+            ShimInput::SecurityHookOwnedBuffer(_, data) => data,
+            ShimInput::SecurityHookPath(_) => {
+                bail!("security hook path input not supported in the verification function")
+            }
+        };
+
+        // Check if the buffer is too large to verify.
+        if buffer.len() > u32::MAX as usize {
+            bail!("buffer is too large to verify with shim lock protocol");
+        }
+
+        // Call the shim verify function.
+        // SAFETY: The shim verify function is specified by the shim lock protocol.
+        // Calling this function is considered safe because the shim verify function is
+        // guaranteed to be defined by the environment if we are able to acquire the protocol.
+        let status = unsafe {
+            (protocol.shim_verify)(buffer.as_ptr() as *const c_void, buffer.len() as u32)
+        };
+
+        // If the verification failed, return the verification failure output.
+        if !status.is_success() {
+            return Ok(ShimVerificationOutput::VerificationFailed(status));
+        }
+
+        // If verification succeeded, return the validation output,
+        // which might include the loaded data.
+        Ok(maybe_loaded_data
+            .map(ShimVerificationOutput::VerifiedDataBuffer)
+            .unwrap_or(ShimVerificationOutput::VerifiedDataNotLoaded))
+    }
+
+    /// Load the image specified by the `input` and returns an image handle.
+    pub fn load(current_image: Handle, input: ShimInput) -> Result<Handle> {
+        // Determine whether Secure Boot is enabled.
+        let secure_boot =
+            SecureBoot::enabled().context("unable to determine if secure boot is enabled")?;
+
+        // Determine whether the shim is loaded.
+        let shim_loaded = Self::loaded().context("unable to determine if shim is loaded")?;
+
+        // Determine whether the shim loader is available.
+        let shim_loader_available =
+            Self::loader_available().context("unable to determine if shim loader is available")?;
+
+        // Determines whether LoadImage in Boot Services must be patched.
+        // Version 16 of the shim doesn't require extra effort to load Secure Boot binaries.
+        // If the image loader is installed, we can skip over the security hook.
+        let requires_security_hook = secure_boot && shim_loaded && !shim_loader_available;
+
+        // If the security hook is required, we will bail for now.
+        if requires_security_hook {
+            // Install the security hook, if possible. If it's not, this is necessary to continue,
+            // so we should bail.
+            let installed = SecurityHook::install().context("unable to install security hook")?;
+            if !installed {
+                bail!("unable to install security hook required for this platform");
+            }
+        }
+
+        // If the shim is loaded, we will need to retain the shim protocol to allow
+        // loading multiple images.
+        if shim_loaded {
+            // Retain the shim protocol after loading the image.
+            Self::retain()?;
+        }
+
+        // Converts the shim input to an owned data buffer.
+        let input = input
+            .into_owned_data_buffer()
+            .context("unable to convert input to loaded data buffer")?;
+
+        // Constructs a LoadImageSource from the input.
+        let source = LoadImageSource::FromBuffer {
+            buffer: input.buffer().context("unable to get buffer from input")?,
+            file_path: input.file_path(),
+        };
+
+        // Loads the image using Boot Services LoadImage function.
+        let result = uefi::boot::load_image(current_image, source).context("unable to load image");
+
+        // If the security override is required, we will uninstall the security hook.
+        if requires_security_hook {
+            let uninstall_result = SecurityHook::uninstall();
+            // Ensure we don't mask load image errors if uninstalling fails.
+            if result.is_err()
+                && let Err(uninstall_error) = &uninstall_result
+            {
+                // Warn on the error since the load image error is more important.
+                warn!("unable to uninstall security hook: {}", uninstall_error);
+            } else {
+                // Otherwise, ensure we handle the original uninstallation result.
+                uninstall_result?;
+            }
+        }
+        result
+    }
+
+    /// Set the ShimRetainProtocol variable to indicate that shim should retain the protocols
+    /// for the full lifetime of boot services.
+    pub fn retain() -> Result<()> {
+        Self::SHIM_LOCK_VARIABLES
+            .set_bool(
+                "ShimRetainProtocol",
+                true,
+                VariableClass::BootAndRuntimeTemporary,
+            )
+            .context("unable to retain shim protocol")?;
+        Ok(())
+    }
+}

src/integrations/shim/hook.rs

@@ -0,0 +1,293 @@
+use crate::integrations::shim::{ShimInput, ShimSupport, ShimVerificationOutput};
+use crate::utils;
+use anyhow::{Context, Result, bail};
+use log::warn;
+use std::sync::{LazyLock, Mutex};
+use uefi::proto::device_path::FfiDevicePath;
+use uefi::proto::unsafe_protocol;
+use uefi::{Guid, guid};
+use uefi_raw::Status;
+
+/// GUID for the EFI_SECURITY_ARCH protocol.
+const SECURITY_ARCH_GUID: Guid = guid!("a46423e3-4617-49f1-b9ff-d1bfa9115839");
+/// GUID for the EFI_SECURITY_ARCH2 protocol.
+const SECURITY_ARCH2_GUID: Guid = guid!("94ab2f58-1438-4ef1-9152-18941a3a0e68");
+
+/// EFI_SECURITY_ARCH protocol definition.
+#[unsafe_protocol(SECURITY_ARCH_GUID)]
+pub struct SecurityArchProtocol {
+    /// Determines the file authentication state.
+    pub file_authentication_state: unsafe extern "efiapi" fn(
+        this: *const SecurityArchProtocol,
+        status: u32,
+        path: *const FfiDevicePath,
+    ) -> Status,
+}
+
+/// EFI_SECURITY_ARCH2 protocol definition.
+#[unsafe_protocol(SECURITY_ARCH2_GUID)]
+pub struct SecurityArch2Protocol {
+    /// Determines the file authentication.
+    pub file_authentication: unsafe extern "efiapi" fn(
+        this: *const SecurityArch2Protocol,
+        path: *const FfiDevicePath,
+        file_buffer: *const u8,
+        file_size: usize,
+        boot_policy: bool,
+    ) -> Status,
+}
+
+/// Global state for the security hook.
+struct SecurityHookState {
+    original_hook: SecurityArchProtocol,
+    original_hook2: SecurityArch2Protocol,
+}
+
+/// Global state for the security hook.
+/// This is messy, but it is safe given the mutex.
+static GLOBAL_HOOK_STATE: LazyLock<Mutex<Option<SecurityHookState>>> =
+    LazyLock::new(|| Mutex::new(None));
+
+/// Security hook helper.
+pub struct SecurityHook;
+
+impl SecurityHook {
+    /// Shared verifier logic for both hook types.
+    #[must_use]
+    fn verify(input: ShimInput) -> bool {
+        // Verify the input and convert the result to a status.
+        let status = match ShimSupport::verify(input) {
+            Ok(output) => match output {
+                // If the verification failed, return the access-denied status.
+                ShimVerificationOutput::VerificationFailed(status) => status,
+                // If the verification succeeded, return the success status.
+                ShimVerificationOutput::VerifiedDataNotLoaded => Status::SUCCESS,
+                ShimVerificationOutput::VerifiedDataBuffer(_) => Status::SUCCESS,
+            },
+
+            // If an error occurs, log the error since we can't return a better error.
+            // Then return the access-denied status.
+            Err(error) => {
+                warn!("unable to verify image: {}", error);
+                Status::ACCESS_DENIED
+            }
+        };
+
+        // If the status is not a success, log the status.
+        if !status.is_success() {
+            warn!("shim verification failed: {}", status);
+        }
+        // Return whether the status is a success.
+        // If it's not a success, the original hook should be called.
+        status.is_success()
+    }
+
+    /// File authentication state verifier for the EFI_SECURITY_ARCH protocol.
+    /// Takes the `path` and determines the verification.
+    unsafe extern "efiapi" fn arch_file_authentication_state(
+        this: *const SecurityArchProtocol,
+        status: u32,
+        path: *const FfiDevicePath,
+    ) -> Status {
+        // Verify the path is not null.
+        if path.is_null() {
+            return Status::INVALID_PARAMETER;
+        }
+
+        // Construct a shim input from the path.
+        let input = ShimInput::SecurityHookPath(path);
+
+        // Convert the input to an owned data buffer.
+        let input = match input.into_owned_data_buffer() {
+            Ok(input) => input,
+            // If an error occurs, log the error and return the not found status.
+            Err(error) => {
+                warn!("unable to read data to be authenticated: {}", error);
+                return Status::NOT_FOUND;
+            }
+        };
+
+        // Verify the input, if it fails, call the original hook.
+        if !Self::verify(input) {
+            // Acquire the global hook state to grab the original hook.
+            let function = match GLOBAL_HOOK_STATE.lock() {
+                // We have acquired the lock, so we can find the original hook.
+                Ok(state) => match state.as_ref() {
+                    // The hook state is available, so we can acquire the original hook.
+                    Some(state) => state.original_hook.file_authentication_state,
+
+                    // The hook state is not available, so we can't call the original hook.
+                    None => {
+                        warn!("global hook state is not available, unable to call original hook");
+                        return Status::LOAD_ERROR;
+                    }
+                },
+
+                Err(error) => {
+                    warn!(
+                        "unable to acquire global hook state lock to call original hook: {}",
+                        error,
+                    );
+                    return Status::LOAD_ERROR;
+                }
+            };
+
+            // Call the original hook function to see what it reports.
+            // SAFETY: This function is safe to call as it is stored by us and is required
+            // in the UEFI specification.
+            unsafe { function(this, status, path) }
+        } else {
+            Status::SUCCESS
+        }
+    }
+
+    /// File authentication verifier for the EFI_SECURITY_ARCH2 protocol.
+    /// Takes the `path` and a file buffer to determine the verification.
+    unsafe extern "efiapi" fn arch2_file_authentication(
+        this: *const SecurityArch2Protocol,
+        path: *const FfiDevicePath,
+        file_buffer: *const u8,
+        file_size: usize,
+        boot_policy: bool,
+    ) -> Status {
+        // Verify the path and file buffer are not null.
+        if path.is_null() || file_buffer.is_null() {
+            return Status::INVALID_PARAMETER;
+        }
+
+        // If the boot policy is true, we can't continue as we don't support that.
+        if boot_policy {
+            return Status::INVALID_PARAMETER;
+        }
+
+        // Construct a slice out of the file buffer and size.
+        let buffer = unsafe { std::slice::from_raw_parts(file_buffer, file_size) };
+
+        // Construct a shim input from the path.
+        let input = ShimInput::SecurityHookBuffer(Some(path), buffer);
+
+        // Verify the input, if it fails, call the original hook.
+        if !Self::verify(input) {
+            // Acquire the global hook state to grab the original hook.
+            let function = match GLOBAL_HOOK_STATE.lock() {
+                // We have acquired the lock, so we can find the original hook.
+                Ok(state) => match state.as_ref() {
+                    // The hook state is available, so we can acquire the original hook.
+                    Some(state) => state.original_hook2.file_authentication,
+
+                    // The hook state is not available, so we can't call the original hook.
+                    None => {
+                        warn!("global hook state is not available, unable to call original hook");
+                        return Status::LOAD_ERROR;
+                    }
+                },
+
+                Err(error) => {
+                    warn!(
+                        "unable to acquire global hook state lock to call original hook: {}",
+                        error
+                    );
+                    return Status::LOAD_ERROR;
+                }
+            };
+
+            // Call the original hook function to see what it reports.
+            // SAFETY: This function is safe to call as it is stored by us and is required
+            // in the UEFI specification.
+            unsafe { function(this, path, file_buffer, file_size, boot_policy) }
+        } else {
+            Status::SUCCESS
+        }
+    }
+
+    /// Install the security hook if needed.
+    pub fn install() -> Result<bool> {
+        // Find the security arch protocol. If we can't find it, we will return false.
+        let Some(hook_arch) = utils::find_handle(&SECURITY_ARCH_GUID)
+            .context("unable to check security arch existence")?
+        else {
+            return Ok(false);
+        };
+
+        // Find the security arch2 protocol. If we can't find it, we will return false.
+        let Some(hook_arch2) = utils::find_handle(&SECURITY_ARCH2_GUID)
+            .context("unable to check security arch2 existence")?
+        else {
+            return Ok(false);
+        };
+
+        // Open the security arch protocol.
+        let mut arch_protocol =
+            uefi::boot::open_protocol_exclusive::<SecurityArchProtocol>(hook_arch)
+                .context("unable to open security arch protocol")?;
+
+        // Open the security arch2 protocol.
+        let mut arch_protocol2 =
+            uefi::boot::open_protocol_exclusive::<SecurityArch2Protocol>(hook_arch2)
+                .context("unable to open security arch2 protocol")?;
+
+        // Construct the global state to store.
+        let state = SecurityHookState {
+            original_hook: SecurityArchProtocol {
+                file_authentication_state: arch_protocol.file_authentication_state,
+            },
+            original_hook2: SecurityArch2Protocol {
+                file_authentication: arch_protocol2.file_authentication,
+            },
+        };
+
+        // Acquire the lock to the global state and replace it.
+        let Ok(mut global_state) = GLOBAL_HOOK_STATE.lock() else {
+            bail!("unable to acquire global hook state lock");
+        };
+        global_state.replace(state);
+
+        // Install the hooks into the UEFI stack.
+        arch_protocol.file_authentication_state = Self::arch_file_authentication_state;
+        arch_protocol2.file_authentication = Self::arch2_file_authentication;
+
+        Ok(true)
+    }
+
+    /// Uninstalls the global security hook, if installed.
+    pub fn uninstall() -> Result<()> {
+        // Find the security arch protocol. If we can't find it, we will do nothing.
+        let Some(hook_arch) = utils::find_handle(&SECURITY_ARCH_GUID)
+            .context("unable to check security arch existence")?
+        else {
+            return Ok(());
+        };
+
+        // Find the security arch2 protocol. If we can't find it, we will do nothing.
+        let Some(hook_arch2) = utils::find_handle(&SECURITY_ARCH2_GUID)
+            .context("unable to check security arch2 existence")?
+        else {
+            return Ok(());
+        };
+
+        // Open the security arch protocol.
+        let mut arch_protocol =
+            uefi::boot::open_protocol_exclusive::<SecurityArchProtocol>(hook_arch)
+                .context("unable to open security arch protocol")?;
+
+        // Open the security arch2 protocol.
+        let mut arch_protocol2 =
+            uefi::boot::open_protocol_exclusive::<SecurityArch2Protocol>(hook_arch2)
+                .context("unable to open security arch2 protocol")?;
+
+        // Acquire the lock to the global state.
+        let Ok(mut global_state) = GLOBAL_HOOK_STATE.lock() else {
+            bail!("unable to acquire global hook state lock");
+        };
+
+        // Take the state and replace the original functions.
+        let Some(state) = global_state.take() else {
+            return Ok(());
+        };
+
+        // Reinstall the original functions.
+        arch_protocol.file_authentication_state = state.original_hook.file_authentication_state;
+        arch_protocol2.file_authentication = state.original_hook2.file_authentication;
+        Ok(())
+    }
+}

src/main.rs

@@ -1,18 +1,22 @@
 #![doc = include_str!("../README.md")]
 #![feature(uefi_std)]
-extern crate core;
+
+/// The delay to wait for when an error occurs in Sprout.
+const DELAY_ON_ERROR: Duration = Duration::from_secs(10);
 
 use crate::config::RootConfiguration;
 use crate::context::{RootContext, SproutContext};
 use crate::entries::BootableEntry;
-use crate::integrations::bootloader_interface::BootloaderInterface;
+use crate::integrations::bootloader_interface::{BootloaderInterface, BootloaderInterfaceTimeout};
 use crate::options::SproutOptions;
 use crate::options::parser::OptionsRepresentable;
 use crate::phases::phase;
 use crate::platform::timer::PlatformTimer;
+use crate::platform::tpm::PlatformTpm;
+use crate::secure::SecureBoot;
 use crate::utils::PartitionGuidForm;
 use anyhow::{Context, Result, bail};
-use log::{error, info};
+use log::{error, info, warn};
 use std::collections::BTreeMap;
 use std::ops::Deref;
 use std::time::Duration;
@@ -54,6 +58,12 @@ pub mod integrations;
 /// phases: Hooks into specific parts of the boot process.
 pub mod phases;
 
+/// sbat: Secure Boot Attestation section.
+pub mod sbat;
+
+/// secure: Secure Boot support.
+pub mod secure;
+
 /// setup: Code that initializes the UEFI environment for Sprout.
 pub mod setup;
 
@@ -65,6 +75,11 @@ pub mod utils;
 
 /// Run Sprout, returning an error if one occurs.
 fn run() -> Result<()> {
+    // For safety reasons, we will note that Secure Boot is in beta on Sprout.
+    if SecureBoot::enabled().context("unable to determine Secure Boot status")? {
+        warn!("Secure Boot is enabled. Sprout Secure Boot is in beta.");
+    }
+
     // Start the platform timer.
     let timer = PlatformTimer::start();
 
@@ -80,6 +95,13 @@ fn run() -> Result<()> {
     BootloaderInterface::set_loader_info()
         .context("unable to set loader info in bootloader interface")?;
 
+    // Acquire the number of active PCR banks on the TPM.
+    // If no TPM is available, this will return zero.
+    let active_pcr_banks = PlatformTpm::active_pcr_banks()?;
+    // Tell the bootloader interface what the number of active PCR banks is.
+    BootloaderInterface::set_tpm2_active_pcr_banks(active_pcr_banks)
+        .context("unable to set tpm2 active PCR banks in bootloader interface")?;
+
     // Parse the options to the sprout executable.
     let options = SproutOptions::parse().context("unable to parse options")?;
 
@@ -240,24 +262,6 @@ fn run() -> Result<()> {
         }
     }
 
-    // If no entries were the default, pick the first entry as the default entry.
-    if entries.iter().all(|entry| !entry.is_default())
-        && let Some(entry) = entries.first_mut()
-    {
-        entry.mark_default();
-    }
-
-    // Iterate over all the entries and tell the bootloader interface what the entries are.
-    for entry in &entries {
-        // If the entry is the default entry, tell the bootloader interface it is the default.
-        if entry.is_default() {
-            // Tell the bootloader interface what the default entry is.
-            BootloaderInterface::set_default_entry(entry.name().to_string())
-                .context("unable to set default entry in bootloader interface")?;
-            break;
-        }
-    }
-
     // Tell the bootloader interface what entries are available.
     BootloaderInterface::set_entries(entries.iter().map(|entry| entry.name()))
         .context("unable to set entries in bootloader interface")?;
@@ -265,18 +269,81 @@ fn run() -> Result<()> {
     // Execute the late phase.
     phase(context.clone(), &config.phases.late).context("unable to execute late phase")?;
 
+    // Acquire the timeout setting from the bootloader interface.
+    let bootloader_interface_timeout =
+        BootloaderInterface::get_timeout().context("unable to get bootloader interface timeout")?;
+
+    // Acquire the default entry from the bootloader interface.
+    let bootloader_interface_default_entry = BootloaderInterface::get_default_entry()
+        .context("unable to get bootloader interface default entry")?;
+
+    // Acquire the oneshot entry from the bootloader interface.
+    let bootloader_interface_oneshot_entry = BootloaderInterface::get_oneshot_entry()
+        .context("unable to get bootloader interface oneshot entry")?;
+
     // If --boot is specified, boot that entry immediately.
-    let force_boot_entry = context.root().options().boot.as_ref();
+    let mut force_boot_entry = context.root().options().boot.clone();
     // If --force-menu is specified, show the boot menu regardless of the value of --boot.
-    let force_boot_menu = context.root().options().force_menu;
+    let mut force_boot_menu = context.root().options().force_menu;
 
     // Determine the menu timeout in seconds based on the options or configuration.
     // We prefer the options over the configuration to allow for overriding.
-    let menu_timeout = context
+    let mut menu_timeout = context
         .root()
         .options()
         .menu_timeout
         .unwrap_or(config.options.menu_timeout);
+
+    // Apply bootloader interface timeout settings.
+    match bootloader_interface_timeout {
+        BootloaderInterfaceTimeout::MenuForce => {
+            // Force the boot menu.
+            force_boot_menu = true;
+        }
+
+        BootloaderInterfaceTimeout::MenuHidden | BootloaderInterfaceTimeout::MenuDisabled => {
+            // Hide the boot menu by setting the timeout to zero.
+            menu_timeout = 0;
+        }
+
+        BootloaderInterfaceTimeout::Timeout(timeout) => {
+            // Configure the timeout to the specified value.
+            menu_timeout = timeout;
+        }
+
+        BootloaderInterfaceTimeout::Unspecified => {
+            // Do nothing.
+        }
+    }
+
+    // Apply bootloader interface default entry settings.
+    if let Some(ref bootloader_interface_default_entry) = bootloader_interface_default_entry {
+        // Iterate over all the entries and mark the default entry as the one specified.
+        for entry in &mut entries {
+            // Mark the entry as the default entry if it matches the specified entry.
+            // If the entry does not match the specified entry, unmark it as the default entry.
+            if entry.is_match(bootloader_interface_default_entry) {
+                entry.mark_default();
+            } else {
+                entry.unmark_default();
+            }
+        }
+    }
+
+    // Apply bootloader interface oneshot entry settings.
+    // If set, we will force booting the oneshot entry.
+    if let Some(ref bootloader_interface_oneshot_entry) = bootloader_interface_oneshot_entry {
+        force_boot_entry = Some(bootloader_interface_oneshot_entry.clone());
+    }
+
+    // If no entries were the default, pick the first entry as the default entry.
+    if entries.iter().all(|entry| !entry.is_default())
+        && let Some(entry) = entries.first_mut()
+    {
+        entry.mark_default();
+    }
+
+    // Convert the menu timeout to a duration.
     let menu_timeout = Duration::from_secs(menu_timeout);
 
     // Use the forced boot entry if possible, otherwise pick the first entry using a boot menu.
@@ -318,8 +385,8 @@ fn main() -> Result<()> {
         for (index, stack) in error.chain().enumerate() {
             error!("[{}]: {}", index, stack);
         }
-        // Sleep for 10 seconds to allow the user to read the error.
-        uefi::boot::stall(Duration::from_secs(10));
+        // Sleep to allow the user to read the error.
+        uefi::boot::stall(DELAY_ON_ERROR);
     }
 
     // Sprout doesn't necessarily guarantee anything was booted.

src/menu.rs

@@ -2,7 +2,7 @@ use crate::entries::BootableEntry;
 use crate::integrations::bootloader_interface::BootloaderInterface;
 use crate::platform::timer::PlatformTimer;
 use anyhow::{Context, Result, bail};
-use log::info;
+use log::{info, warn};
 use std::time::Duration;
 use uefi::ResultExt;
 use uefi::boot::TimerTrigger;
@@ -56,16 +56,35 @@ fn read(input: &mut Input, timeout: &Duration) -> Result<MenuOperation> {
     uefi::boot::set_timer(&timer_event, trigger).context("unable to set timeout timer")?;
 
     let mut events = vec![timer_event, key_event];
-    let event = uefi::boot::wait_for_event(&mut events)
+
+    // Wait for either the timer event or the key event to trigger.
+    // Store the result so that we can free the timer event.
+    let event_result = uefi::boot::wait_for_event(&mut events)
         .discard_errdata()
-        .context("unable to wait for event")?;
+        .context("unable to wait for event");
 
     // Close the timer event that we acquired.
     // We don't need to close the key event because it is owned globally.
     if let Some(timer_event) = events.into_iter().next() {
-        uefi::boot::close_event(timer_event).context("unable to close timer event")?;
+        // Store the result of the close event so we can determine if we can safely assert it.
+        let close_event_result =
+            uefi::boot::close_event(timer_event).context("unable to close timer event");
+        if event_result.is_err()
+            && let Err(ref close_event_error) = close_event_result
+        {
+            // Log a warning if we failed to close the timer event.
+            // This is done to ensure we don't mask the wait_for_event error.
+            warn!("unable to close timer event: {}", close_event_error);
+        } else {
+            // If we reach here, we can safely assert that the close event succeeded without
+            // masking the wait_for_event error.
+            close_event_result?;
+        }
     }
 
+    // Acquire the event that triggered.
+    let event = event_result?;
+
     // The first event is the timer event.
     // If it has triggered, the user did not select a numbered entry.
     if event == 0 {
@@ -114,7 +133,7 @@ fn select_with_input<'a>(
             info!("Boot Menu:");
             for (index, entry) in entries.iter().enumerate() {
                 let title = entry.context().stamp(&entry.declaration().title);
-                info!("  [{}] {} ({})", index, title, entry.name());
+                info!("  [{}] {}", index, title);
             }
         }
 

src/options.rs

@@ -44,6 +44,13 @@ impl OptionsRepresentable for SproutOptions {
     /// All the Sprout options that are defined.
     fn options() -> &'static [(&'static str, OptionDescription<'static>)] {
         &[
+            (
+                "autoconfigure",
+                OptionDescription {
+                    description: "Enable Sprout Autoconfiguration",
+                    form: OptionForm::Flag,
+                },
+            ),
             (
                 "config",
                 OptionDescription {

src/options/parser.rs

@@ -46,8 +46,24 @@ pub trait OptionsRepresentable {
         let configured: BTreeMap<_, _> = BTreeMap::from_iter(Self::options().to_vec());
 
         // Collect all the arguments to Sprout.
-        // Skip the first argument which is the path to our executable.
-        let args = std::env::args().skip(1).collect::<Vec<_>>();
+        // Skip the first argument, which is the path to our executable.
+        let mut args = std::env::args().skip(1).collect::<Vec<_>>();
+
+        // Correct firmware that may add invalid arguments at the start.
+        // Witnessed this on a Dell Precision 5690 when direct booting.
+        loop {
+            // Grab the first argument or break.
+            let Some(arg) = args.first() else {
+                break;
+            };
+
+            // If the argument starts with a tilde, remove it.
+            if arg.starts_with("`") {
+                args.remove(0);
+                continue;
+            }
+            break;
+        }
 
         // Represent options as key-value pairs.
         let mut options = BTreeMap::new();
@@ -96,7 +112,7 @@ pub trait OptionsRepresentable {
                 let maybe_next = iterator.peek();
 
                 // If the next value isn't another option, set the value to the next value.
-                // Otherwise, it is an empty string.
+                // Otherwise, it is None.
                 value = if let Some(next) = maybe_next
                     && !next.starts_with("--")
                 {

src/platform.rs

@@ -1,2 +1,4 @@
 /// timer: Platform timer support.
 pub mod timer;
+/// tpm: Platform TPM support.
+pub mod tpm;

src/platform/timer.rs

@@ -53,9 +53,14 @@ fn arch_ticks() -> u64 {
 /// Acquire the tick frequency reported by the platform.
 fn arch_frequency() -> TickFrequency {
     #[cfg(target_arch = "aarch64")]
-    return aarch64::frequency();
+    let frequency = aarch64::frequency();
     #[cfg(target_arch = "x86_64")]
-    return x86_64::frequency();
+    let frequency = x86_64::frequency();
+    // If the frequency is 0, then something went very wrong and we should panic.
+    if frequency.ticks() == 0 {
+        panic!("timer frequency is zero");
+    }
+    frequency
 }
 
 /// Platform timer that allows measurement of the elapsed time.
@@ -83,7 +88,7 @@ impl PlatformTimer {
 
     /// Measure the elapsed duration since the timer was started.
     pub fn elapsed_since_start(&self) -> Duration {
-        let duration = arch_ticks() - self.start;
+        let duration = arch_ticks().wrapping_sub(self.start);
         self.frequency.duration(duration)
     }
 }

src/platform/timer/x86_64.rs

@@ -50,17 +50,17 @@ pub fn stop() -> u64 {
 }
 
 /// Measure the frequency of the platform timer.
-fn measure_frequency(duration: &Duration) -> u64 {
+fn measure_frequency() -> u64 {
     let start = start();
-    uefi::boot::stall(*duration);
+    uefi::boot::stall(MEASURE_FREQUENCY_DURATION);
     let stop = stop();
-    let elapsed = (stop - start) as f64;
-    (elapsed / duration.as_secs_f64()) as u64
+    let elapsed = stop.wrapping_sub(start) as f64;
+    (elapsed / MEASURE_FREQUENCY_DURATION.as_secs_f64()) as u64
 }
 
 /// Acquire the platform timer frequency.
 /// On x86_64, this is slightly expensive, so it should be done once.
 pub fn frequency() -> TickFrequency {
-    let frequency = measure_frequency(&MEASURE_FREQUENCY_DURATION);
+    let frequency = measure_frequency();
     TickFrequency::Measured(frequency, MEASURE_FREQUENCY_DURATION)
 }

src/platform/tpm.rs

@@ -0,0 +1,128 @@
+use crate::utils;
+use anyhow::{Context, Result};
+use uefi::ResultExt;
+use uefi::boot::ScopedProtocol;
+use uefi::proto::tcg::PcrIndex;
+use uefi::proto::tcg::v2::{PcrEventInputs, Tcg};
+use uefi_raw::protocol::tcg::EventType;
+use uefi_raw::protocol::tcg::v2::{Tcg2HashLogExtendEventFlags, Tcg2Protocol, Tcg2Version};
+
+/// Represents the platform TPM.
+pub struct PlatformTpm;
+
+/// Represents an open TPM handle.
+pub struct TpmProtocolHandle {
+    /// The version of the TPM protocol.
+    version: Tcg2Version,
+    /// The protocol itself.
+    protocol: ScopedProtocol<Tcg>,
+}
+
+impl TpmProtocolHandle {
+    /// Construct a new [TpmProtocolHandle] from the `version` and `protocol`.
+    pub fn new(version: Tcg2Version, protocol: ScopedProtocol<Tcg>) -> Self {
+        Self { version, protocol }
+    }
+
+    /// Access the version provided by the tcg2 protocol.
+    pub fn version(&self) -> Tcg2Version {
+        self.version
+    }
+
+    /// Access the protocol interface for tcg2.
+    pub fn protocol(&mut self) -> &mut ScopedProtocol<Tcg> {
+        &mut self.protocol
+    }
+}
+
+impl PlatformTpm {
+    /// The PCR for measuring the bootloader configuration into.
+    pub const PCR_BOOT_LOADER_CONFIG: PcrIndex = PcrIndex(5);
+
+    /// Acquire access to the TPM protocol handle, if possible.
+    /// Returns None if TPM is not available.
+    fn protocol() -> Result<Option<TpmProtocolHandle>> {
+        // Attempt to acquire the TCG2 protocol handle. If it's not available, return None.
+        let Some(handle) =
+            utils::find_handle(&Tcg2Protocol::GUID).context("unable to determine tpm presence")?
+        else {
+            return Ok(None);
+        };
+
+        // If we reach here, we've already validated that the handle
+        // implements the TCG2 protocol.
+        let mut protocol = uefi::boot::open_protocol_exclusive::<Tcg>(handle)
+            .context("unable to open tcg2 protocol")?;
+
+        // Acquire the capabilities of the TPM.
+        let capability = protocol
+            .get_capability()
+            .context("unable to get tcg2 boot service capability")?;
+
+        // If the TPM is not present, return None.
+        if !capability.tpm_present() {
+            return Ok(None);
+        }
+
+        // If the TPM is present, we need to determine the version of the TPM.
+        let version = capability.protocol_version;
+
+        // We have a TPM, so return the protocol version and the protocol handle.
+        Ok(Some(TpmProtocolHandle::new(version, protocol)))
+    }
+
+    /// Determines whether the platform TPM is present.
+    pub fn present() -> Result<bool> {
+        Ok(PlatformTpm::protocol()?.is_some())
+    }
+
+    /// Determine the number of active PCR banks on the TPM.
+    /// If no TPM is available, this will return zero.
+    pub fn active_pcr_banks() -> Result<u32> {
+        // Acquire access to the TPM protocol handle.
+        let Some(mut handle) = PlatformTpm::protocol()? else {
+            return Ok(0);
+        };
+
+        // Check if the TPM supports `GetActivePcrBanks`, and if it doesn't return zero.
+        if handle.version().major < 1 || handle.version().major == 1 && handle.version().minor < 1 {
+            return Ok(0);
+        }
+
+        // The safe wrapper for this function will decode the bitmap.
+        // Strictly speaking, it's not future-proof to re-encode that, but in practice it will work.
+        let banks = handle
+            .protocol()
+            .get_active_pcr_banks()
+            .context("unable to get active pcr banks")?;
+
+        // Return the number of active PCR banks.
+        Ok(banks.bits())
+    }
+
+    /// Log an event into the TPM pcr `pcr_index` with `buffer` as data. The `description`
+    /// is used to describe what the event is.
+    ///
+    /// If a TPM is not available, this will do nothing.
+    pub fn log_event(pcr_index: PcrIndex, buffer: &[u8], description: &str) -> Result<()> {
+        // Acquire access to the TPM protocol handle.
+        let Some(mut handle) = PlatformTpm::protocol()? else {
+            return Ok(());
+        };
+
+        // Encode the description as UTF-8.
+        let description = description.as_bytes().to_vec();
+
+        // Construct an event input for the TPM.
+        let event = PcrEventInputs::new_in_box(pcr_index, EventType::IPL, &description)
+            .discard_errdata()
+            .context("unable to construct pcr event inputs")?;
+
+        // Log the event into the TPM.
+        handle
+            .protocol()
+            .hash_log_extend_event(Tcg2HashLogExtendEventFlags::empty(), buffer, &event)
+            .context("unable to log event to tpm")?;
+        Ok(())
+    }
+}

src/sbat.rs

@@ -0,0 +1,11 @@
+/// SBAT must be aligned by 512 bytes.
+const SBAT_SIZE: usize = 512;
+
+/// Define the SBAT attestation by including the sbat.csv file.
+/// See this document for more details: https://github.com/rhboot/shim/blob/main/SBAT.md
+/// NOTE: Alignment can't be enforced by an attribute, so instead the alignment is currently
+/// enforced by the SBAT_SIZE being 512. The build.rs will ensure that the sbat.csv is padded.
+/// This code will not compile if the sbat.csv is a different size than SBAT_SIZE.
+#[used]
+#[unsafe(link_section = ".sbat")]
+static SBAT: [u8; SBAT_SIZE] = *include_bytes!(concat!(env!("OUT_DIR"), "/sbat.csv"));

src/sbat.template.csv

@@ -0,0 +1,2 @@
+sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
+sprout,1,Edera,sprout,{version},https://sprout.edera.dev

src/secure.rs

@@ -0,0 +1,14 @@
+use crate::utils::variables::VariableController;
+use anyhow::Result;
+
+/// Secure boot services.
+pub struct SecureBoot;
+
+impl SecureBoot {
+    /// Checks if Secure Boot is enabled on the system.
+    /// This might fail if retrieving the variable fails in an irrecoverable way.
+    pub fn enabled() -> Result<bool> {
+        // The SecureBoot variable will tell us whether Secure Boot is enabled at all.
+        VariableController::GLOBAL.get_bool("SecureBoot")
+    }
+}

src/utils.rs

@@ -1,5 +1,6 @@
-use anyhow::{Context, Result};
+use anyhow::{Context, Result, bail};
 use std::ops::Deref;
+use uefi::boot::SearchType;
 use uefi::fs::{FileSystem, Path};
 use uefi::proto::device_path::text::{AllowShortcuts, DevicePathFromText, DisplayOnly};
 use uefi::proto::device_path::{DevicePath, PoolDevicePath};
@@ -14,6 +15,12 @@ pub mod framebuffer;
 /// Support code for the media loader protocol.
 pub mod media_loader;
 
+/// Support code for EFI variables.
+pub mod variables;
+
+/// Implements a version comparison algorithm according to the BLS specification.
+pub mod vercmp;
+
 /// Parses the input `path` as a [DevicePath].
 /// Uses the [DevicePathFromText] protocol exclusively, and will fail if it cannot acquire the protocol.
 pub fn text_to_device_path(path: &str) -> Result<PoolDevicePath> {
@@ -100,10 +107,24 @@ pub struct ResolvedPath {
     pub filesystem_handle: Handle,
 }
 
+impl ResolvedPath {
+    /// Read the file specified by this path into a buffer and return it.
+    pub fn read_file(&self) -> Result<Vec<u8>> {
+        let fs = uefi::boot::open_protocol_exclusive::<SimpleFileSystem>(self.filesystem_handle)
+            .context("unable to open filesystem protocol")?;
+        let mut fs = FileSystem::new(fs);
+        let path = self
+            .sub_path
+            .to_string(DisplayOnly(false), AllowShortcuts(false))?;
+        let content = fs.read(Path::new(&path));
+        content.context("unable to read file contents")
+    }
+}
+
 /// Resolve a path specified by `input` to its various components.
 /// Uses `default_root_path` as the base root if one is not specified in the path.
 /// Returns [ResolvedPath] which contains the resolved components.
-pub fn resolve_path(default_root_path: &DevicePath, input: &str) -> Result<ResolvedPath> {
+pub fn resolve_path(default_root_path: Option<&DevicePath>, input: &str) -> Result<ResolvedPath> {
     let mut path = text_to_device_path(input).context("unable to convert text to path")?;
     let path_has_device = path
         .node_iter()
@@ -119,6 +140,9 @@ pub fn resolve_path(default_root_path: &DevicePath, input: &str) -> Result<Resol
         if !input.starts_with('\\') {
             input.insert(0, '\\');
         }
+
+        let default_root_path = default_root_path.context("unable to get default root path")?;
+
         input.insert_str(
             0,
             device_path_root(default_root_path)
@@ -133,8 +157,11 @@ pub fn resolve_path(default_root_path: &DevicePath, input: &str) -> Result<Resol
     let root_path = text_to_device_path(root.as_str())
         .context("unable to convert root to path")?
         .to_boxed();
-    let mut root_path = root_path.as_ref();
-    let handle = uefi::boot::locate_device_path::<SimpleFileSystem>(&mut root_path)
+    let root_path = root_path.as_ref();
+
+    // locate_device_path modifies the path, so we need to clone it.
+    let root_path_modifiable = root_path.to_owned();
+    let handle = uefi::boot::locate_device_path::<SimpleFileSystem>(&mut &*root_path_modifiable)
         .context("unable to locate filesystem device path")?;
     let subpath = device_path_subpath(path.deref()).context("unable to get device subpath")?;
     Ok(ResolvedPath {
@@ -152,16 +179,9 @@ pub fn resolve_path(default_root_path: &DevicePath, input: &str) -> Result<Resol
 /// This acquires exclusive protocol access to the [SimpleFileSystem] protocol of the resolved
 /// filesystem handle, so care must be taken to call this function outside a scope with
 /// the filesystem handle protocol acquired.
-pub fn read_file_contents(default_root_path: &DevicePath, input: &str) -> Result<Vec<u8>> {
+pub fn read_file_contents(default_root_path: Option<&DevicePath>, input: &str) -> Result<Vec<u8>> {
     let resolved = resolve_path(default_root_path, input)?;
-    let fs = uefi::boot::open_protocol_exclusive::<SimpleFileSystem>(resolved.filesystem_handle)
-        .context("unable to open filesystem protocol")?;
-    let mut fs = FileSystem::new(fs);
-    let path = resolved
-        .sub_path
-        .to_string(DisplayOnly(false), AllowShortcuts(false))?;
-    let content = fs.read(Path::new(&path));
-    content.context("unable to read file contents")
+    resolved.read_file()
 }
 
 /// Filter a string-like Option `input` such that an empty string is [None].
@@ -187,12 +207,15 @@ pub fn unique_hash(input: &str) -> String {
 /// Represents the type of partition GUID that can be retrieved.
 #[derive(PartialEq, Eq)]
 pub enum PartitionGuidForm {
+    /// The partition GUID is the unique partition GUID.
     Partition,
+    /// The partition GUID is the partition type GUID.
     PartitionType,
 }
 
 /// Retrieve the partition / partition type GUID of the device root `path`.
 /// This only works on GPT partitions. If the root is not a GPT partition, None is returned.
+/// If the GUID is all zeros, this will return None.
 pub fn partition_guid(path: &DevicePath, form: PartitionGuidForm) -> Result<Option<Guid>> {
     // Clone the path so we can pass it to the UEFI stack.
     let path = path.to_boxed();
@@ -224,8 +247,50 @@ pub fn partition_guid(path: &DevicePath, form: PartitionGuidForm) -> Result<Opti
                 // Match the form of the partition GUID.
                 PartitionGuidForm::Partition => entry.unique_partition_guid,
                 PartitionGuidForm::PartitionType => entry.partition_type_guid.0,
-            }))
+            })
+            .filter(|guid| !guid.is_zero()))
     } else {
         Ok(None)
     }
 }
+
+/// Find a handle that provides the specified `protocol`.
+pub fn find_handle(protocol: &Guid) -> Result<Option<Handle>> {
+    // Locate the requested protocol handle.
+    match uefi::boot::locate_handle_buffer(SearchType::ByProtocol(protocol)) {
+        // If a handle is found, the protocol is available.
+        Ok(handles) => Ok(if handles.is_empty() {
+            None
+        } else {
+            Some(handles[0])
+        }),
+        // If an error occurs, check if it is because the protocol is not available.
+        // If so, return false. Otherwise, return the error.
+        Err(error) => {
+            if error.status() == Status::NOT_FOUND {
+                Ok(None)
+            } else {
+                Err(error).context("unable to determine if the protocol is available")
+            }
+        }
+    }
+}
+
+/// Convert a byte slice into a CString16.
+pub fn utf16_bytes_to_cstring16(bytes: &[u8]) -> Result<CString16> {
+    // Validate the input bytes are the right length.
+    if !bytes.len().is_multiple_of(2) {
+        bail!("utf16 bytes must be a multiple of 2");
+    }
+
+    // Convert the bytes to UTF-16 data.
+    let data = bytes
+        // Chunk everything into two bytes.
+        .chunks_exact(2)
+        // Reinterpret the bytes as u16 little-endian.
+        .map(|chunk| u16::from_le_bytes([chunk[0], chunk[1]]))
+        // Collect the result into a vector.
+        .collect::<Vec<_>>();
+
+    CString16::try_from(data).context("unable to convert utf16 bytes to CString16")
+}

src/utils/media_loader.rs

@@ -33,8 +33,6 @@ struct MediaLoaderProtocol {
 /// You MUST call [MediaLoaderHandle::unregister] when ready to unregister.
 /// [Drop] is not implemented for this type.
 pub struct MediaLoaderHandle {
-    /// The vendor GUID of the media loader.
-    guid: Guid,
     /// The handle of the media loader in the UEFI stack.
     handle: Handle,
     /// The protocol interface pointer.
@@ -229,7 +227,6 @@ impl MediaLoaderHandle {
 
         // Return a handle to the media loader.
         Ok(Self {
-            guid,
             handle: primary_handle,
             protocol,
             path,
@@ -239,13 +236,8 @@ impl MediaLoaderHandle {
     /// Unregisters a media loader from the UEFI stack.
     /// This will free the memory allocated by the passed data.
     pub fn unregister(self) -> Result<()> {
-        // Check if the media loader is registered.
-        // If it is not, we don't need to do anything.
-        if !Self::already_registered(self.guid)? {
-            return Ok(());
-        }
-
-        // SAFETY: We know that the media loader is registered, so we can safely uninstall it.
+        // SAFETY: We know that the media loader is registered if the handle is valid,
+        // so we can safely uninstall it.
         // We should have allocated the pointers involved, so we can safely free them.
         unsafe {
             // Uninstall the protocol interface for the device path protocol.

src/utils/variables.rs

@@ -0,0 +1,152 @@
+use crate::utils;
+use anyhow::{Context, Result};
+use log::warn;
+use uefi::{CString16, guid};
+use uefi_raw::Status;
+use uefi_raw::table::runtime::{VariableAttributes, VariableVendor};
+
+/// The classification of a variable.
+/// This is an abstraction over various variable attributes.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum VariableClass {
+    /// The variable is available in Boot Services and Runtime Services and is not persistent.
+    BootAndRuntimeTemporary,
+}
+
+impl VariableClass {
+    /// The [VariableAttributes] for this classification.
+    fn attributes(&self) -> VariableAttributes {
+        match self {
+            VariableClass::BootAndRuntimeTemporary => {
+                VariableAttributes::BOOTSERVICE_ACCESS | VariableAttributes::RUNTIME_ACCESS
+            }
+        }
+    }
+}
+
+/// Provides access to a particular set of vendor variables.
+pub struct VariableController {
+    /// The GUID of the vendor.
+    vendor: VariableVendor,
+}
+
+impl VariableController {
+    /// Global variables.
+    pub const GLOBAL: VariableController = VariableController::new(VariableVendor(guid!(
+        "8be4df61-93ca-11d2-aa0d-00e098032b8c"
+    )));
+
+    /// Create a new [VariableController] for the `vendor`.
+    pub const fn new(vendor: VariableVendor) -> Self {
+        Self { vendor }
+    }
+
+    /// Convert `key` to a variable name as a CString16.
+    fn name(key: &str) -> Result<CString16> {
+        CString16::try_from(key).context("unable to convert variable name to CString16")
+    }
+
+    /// Retrieve the cstr16 value specified by the `key`.
+    /// Returns None if the value isn't set.
+    /// If the value is not decodable, we will return None and log a warning.
+    pub fn get_cstr16(&self, key: &str) -> Result<Option<String>> {
+        let name = Self::name(key)?;
+
+        // Retrieve the variable data, handling variable not existing as None.
+        match uefi::runtime::get_variable_boxed(&name, &self.vendor) {
+            Ok((data, _)) => {
+                // Try to decode UTF-16 bytes to a CString16.
+                match utils::utf16_bytes_to_cstring16(&data) {
+                    Ok(value) => {
+                        // We have a value, so return the UTF-8 value.
+                        Ok(Some(value.to_string()))
+                    }
+
+                    Err(error) => {
+                        // We encountered an error, so warn and return None.
+                        warn!("efi variable '{}' is not valid UTF-16: {}", key, error);
+                        Ok(None)
+                    }
+                }
+            }
+
+            Err(error) => {
+                // If the variable does not exist, we will return None.
+                if error.status() == Status::NOT_FOUND {
+                    Ok(None)
+                } else {
+                    Err(error).with_context(|| format!("unable to get efi variable {}", key))
+                }
+            }
+        }
+    }
+
+    /// Retrieve a boolean value specified by the `key`.
+    pub fn get_bool(&self, key: &str) -> Result<bool> {
+        let name = Self::name(key)?;
+
+        // Retrieve the variable data, handling variable not existing as false.
+        match uefi::runtime::get_variable_boxed(&name, &self.vendor) {
+            Ok((data, _)) => {
+                // If the variable is zero-length, we treat it as false.
+                if data.is_empty() {
+                    Ok(false)
+                } else {
+                    // We treat the variable as true if the first byte is non-zero.
+                    Ok(data[0] > 0)
+                }
+            }
+
+            Err(error) => {
+                // If the variable does not exist, we treat it as false.
+                if error.status() == Status::NOT_FOUND {
+                    Ok(false)
+                } else {
+                    Err(error).with_context(|| format!("unable to get efi variable {}", key))
+                }
+            }
+        }
+    }
+
+    /// Set a variable specified by `key` to `value`.
+    /// The variable `class` controls the attributes for the variable.
+    pub fn set(&self, key: &str, value: &[u8], class: VariableClass) -> Result<()> {
+        let name = Self::name(key)?;
+        uefi::runtime::set_variable(&name, &self.vendor, class.attributes(), value)
+            .with_context(|| format!("unable to set efi variable {}", key))?;
+        Ok(())
+    }
+
+    /// Set a variable specified by `key` to `value`, converting the value to
+    /// a [CString16]. The variable `class` controls the attributes for the variable.
+    pub fn set_cstr16(&self, key: &str, value: &str, class: VariableClass) -> Result<()> {
+        // Encode the value as a CString16 little endian.
+        let mut encoded = value
+            .encode_utf16()
+            .flat_map(|c| c.to_le_bytes())
+            .collect::<Vec<u8>>();
+        // Add a null terminator to the end of the value.
+        encoded.extend_from_slice(&[0, 0]);
+        self.set(key, &encoded, class)
+    }
+
+    /// Set a boolean variable specified by `key` to `value`, converting the value.
+    /// The variable `class` controls the attributes for the variable.
+    pub fn set_bool(&self, key: &str, value: bool, class: VariableClass) -> Result<()> {
+        self.set(key, &[value as u8], class)
+    }
+
+    /// Set the u64 little-endian variable specified by `key` to `value`.
+    /// The variable `class` controls the attributes for the variable.
+    pub fn set_u64le(&self, key: &str, value: u64, class: VariableClass) -> Result<()> {
+        self.set(key, &value.to_le_bytes(), class)
+    }
+
+    pub fn remove(&self, key: &str) -> Result<()> {
+        let name = Self::name(key)?;
+
+        // Delete the variable from UEFI.
+        uefi::runtime::delete_variable(&name, &self.vendor)
+            .with_context(|| format!("unable to remove efi variable {}", key))
+    }
+}

src/utils/vercmp.rs

@@ -0,0 +1,184 @@
+use std::cmp::Ordering;
+use std::iter::Peekable;
+
+/// Handles single character advancement and comparison.
+macro_rules! handle_single_char {
+    ($ca: expr, $cb:expr, $a_chars:expr, $b_chars:expr, $c:expr) => {
+        match ($ca == $c, $cb == $c) {
+            (true, false) => return Ordering::Less,
+            (false, true) => return Ordering::Greater,
+            (true, true) => {
+                $a_chars.next();
+                $b_chars.next();
+                continue;
+            }
+            _ => {}
+        }
+    };
+}
+
+/// Compares two strings using the BLS version comparison specification.
+/// Handles optional values as well by comparing only if both are specified.
+pub fn compare_versions_optional(a: Option<&str>, b: Option<&str>) -> Ordering {
+    match (a, b) {
+        // If both have values, compare them.
+        (Some(a), Some(b)) => compare_versions(a, b),
+        // If the second value is None, return that it is less than the first.
+        (Some(_a), None) => Ordering::Less,
+        // If the first value is None, return that it is greater than the second.
+        (None, Some(_b)) => Ordering::Greater,
+        // If both values are None, return that they are equal.
+        (None, None) => Ordering::Equal,
+    }
+}
+
+/// Compares two strings using the BLS version comparison specification.
+/// See: https://uapi-group.org/specifications/specs/version_format_specification/
+pub fn compare_versions(a: &str, b: &str) -> Ordering {
+    // Acquire a peekable iterator for each string.
+    let mut a_chars = a.chars().peekable();
+    let mut b_chars = b.chars().peekable();
+
+    // Loop until we have reached the end of one of the strings.
+    loop {
+        // Skip invalid characters in both strings.
+        skip_invalid(&mut a_chars);
+        skip_invalid(&mut b_chars);
+
+        // Check if either string has ended.
+        match (a_chars.peek(), b_chars.peek()) {
+            // No more characters in either string.
+            (None, None) => return Ordering::Equal,
+            // One string has ended, the other hasn't.
+            (None, Some(_)) => return Ordering::Less,
+            (Some(_), None) => return Ordering::Greater,
+            // Both strings have characters left.
+            (Some(&ca), Some(&cb)) => {
+                // Handle the ~ character.
+                handle_single_char!(ca, cb, a_chars, b_chars, '~');
+
+                // Handle '-' character.
+                handle_single_char!(ca, cb, a_chars, b_chars, '-');
+
+                // Handle the '^' character.
+                handle_single_char!(ca, cb, a_chars, b_chars, '^');
+
+                // Handle the '.' character.
+                handle_single_char!(ca, cb, a_chars, b_chars, '.');
+
+                // Handle digits with numerical comparison.
+                // We key off of the A character being a digit intentionally as we presume
+                // this indicates it will be the same at this position.
+                if ca.is_ascii_digit() || cb.is_ascii_digit() {
+                    let result = compare_numeric(&mut a_chars, &mut b_chars);
+                    if result != Ordering::Equal {
+                        return result;
+                    }
+                    continue;
+                }
+
+                // Handle letters with alphabetical comparison.
+                // We key off of the A character being alphabetical intentionally as we presume
+                // this indicates it will be the same at this position.
+                if ca.is_ascii_alphabetic() || cb.is_ascii_alphabetic() {
+                    let result = compare_alphabetic(&mut a_chars, &mut b_chars);
+                    if result != Ordering::Equal {
+                        return result;
+                    }
+                    continue;
+                }
+            }
+        }
+    }
+}
+
+/// Skips characters that are not in the valid character set.
+fn skip_invalid<I: Iterator<Item = char>>(iter: &mut Peekable<I>) {
+    while let Some(&c) = iter.peek() {
+        if is_valid_char(c) {
+            break;
+        }
+        iter.next();
+    }
+}
+
+/// Checks if a character is in the valid character set for comparison.
+fn is_valid_char(c: char) -> bool {
+    matches!(c, 'a'..='z' | 'A'..='Z' | '0'..='9' | '-' | '.' | '~' | '^')
+}
+
+/// Compares numerical prefixes by extracting numbers.
+fn compare_numeric<I: Iterator<Item = char>>(
+    iter_a: &mut Peekable<I>,
+    iter_b: &mut Peekable<I>,
+) -> Ordering {
+    let num_a = extract_number(iter_a);
+    let num_b = extract_number(iter_b);
+
+    num_a.cmp(&num_b)
+}
+
+/// Extracts a number from the iterator, skipping leading zeros.
+fn extract_number<I: Iterator<Item = char>>(iter: &mut Peekable<I>) -> u64 {
+    // Skip leading zeros
+    while let Some(&'0') = iter.peek() {
+        iter.next();
+    }
+
+    let mut num = 0u64;
+    while let Some(&c) = iter.peek() {
+        if c.is_ascii_digit() {
+            iter.next();
+            num = num.saturating_mul(10).saturating_add(c as u64 - '0' as u64);
+        } else {
+            break;
+        }
+    }
+
+    num
+}
+
+/// Compares alphabetical prefixes
+/// Capital letters compare lower than lowercase letters (B < a)
+fn compare_alphabetic<I: Iterator<Item = char>>(
+    iter_a: &mut Peekable<I>,
+    iter_b: &mut Peekable<I>,
+) -> Ordering {
+    loop {
+        return match (iter_a.peek(), iter_b.peek()) {
+            (Some(&ca), Some(&cb)) if ca.is_ascii_alphabetic() && cb.is_ascii_alphabetic() => {
+                if ca == cb {
+                    // Same character, we should continue.
+                    iter_a.next();
+                    iter_b.next();
+                    continue;
+                }
+
+                // Different characters found.
+                // All capital letters compare lower than lowercase letters.
+                match (ca.is_ascii_uppercase(), cb.is_ascii_uppercase()) {
+                    (true, false) => Ordering::Less,    // uppercase < lowercase
+                    (false, true) => Ordering::Greater, // lowercase > uppercase
+                    (true, true) => ca.cmp(&cb),        // both are uppercase
+                    (false, false) => ca.cmp(&cb),      // both are lowercase
+                }
+            }
+
+            (Some(&ca), Some(_)) if ca.is_ascii_alphabetic() => {
+                // a has letters, b doesn't
+                Ordering::Greater
+            }
+
+            (Some(_), Some(&cb)) if cb.is_ascii_alphabetic() => {
+                // b has letters, a doesn't
+                Ordering::Less
+            }
+
+            (Some(&ca), None) if ca.is_ascii_alphabetic() => Ordering::Greater,
+
+            (None, Some(&cb)) if cb.is_ascii_alphabetic() => Ordering::Less,
+
+            _ => Ordering::Equal,
+        };
+    }
+}