chore(eficore): decouple the shim support from the image load callsites

crates/boot/src/actions/chainload.rs

@@ -5,9 +5,10 @@ use alloc::rc::Rc;
 use anyhow::{Context, Result, bail};
 use edera_sprout_config::actions::chainload::ChainloadConfiguration;
 use eficore::bootloader_interface::BootloaderInterface;
+use eficore::loader::source::ImageSource;
+use eficore::loader::{ImageLoadRequest, ImageLoader};
 use eficore::media_loader::MediaLoaderHandle;
 use eficore::media_loader::constants::linux::LINUX_EFI_INITRD_MEDIA_GUID;
-use eficore::shim::{ShimInput, ShimSupport};
 use log::error;
 use uefi::CString16;
 use uefi::proto::loaded_image::LoadedImage;
@@ -24,13 +25,17 @@ pub fn chainload(context: Rc<SproutContext>, configuration: &ChainloadConfigurat
     )
     .context("unable to resolve chainload path")?;
 
-    // Load the image to chainload using the shim support integration.
+    // Create a new image load request with the current image and the resolved path.
+    let request = ImageLoadRequest::new(sprout_image, ImageSource::ResolvedPath(&resolved));
+
+    // Load the image to chainload using the image loader support module.
     // 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))?;
+    let image = ImageLoader::load(request)?;
 
     // Open the LoadedImage protocol of the image to chainload.
-    let mut loaded_image_protocol = uefi::boot::open_protocol_exclusive::<LoadedImage>(image)
+    let mut loaded_image_protocol =
-        .context("unable to open loaded image protocol")?;
+        uefi::boot::open_protocol_exclusive::<LoadedImage>(*image.handle())
+            .context("unable to open loaded image protocol")?;
 
     // Stamp and combine the options to pass to the image.
     let options =
@@ -87,7 +92,7 @@ pub fn chainload(context: Rc<SproutContext>, configuration: &ChainloadConfigurat
     // This call might return, or it may pass full control to another image that will never return.
     // Capture the result to ensure we can return an error if the image fails to start, but only
     // after the optional initrd has been unregistered.
-    let result = uefi::boot::start_image(image);
+    let result = uefi::boot::start_image(*image.handle());
 
     // Unregister the initrd if it was registered.
     if let Some(initrd_handle) = initrd_handle

crates/boot/src/drivers.rs

@@ -5,7 +5,8 @@ use alloc::rc::Rc;
 use alloc::string::String;
 use anyhow::{Context, Result};
 use edera_sprout_config::drivers::DriverDeclaration;
-use eficore::shim::{ShimInput, ShimSupport};
+use eficore::loader::source::ImageSource;
+use eficore::loader::{ImageLoadRequest, ImageLoader};
 use log::info;
 use uefi::boot::SearchType;
 
@@ -21,14 +22,17 @@ fn load_driver(context: Rc<SproutContext>, driver: &DriverDeclaration) -> Result
     )
     .context("unable to resolve path to driver")?;
 
-    // Load the driver image using the shim support integration.
+    // Create an image load request with the current image and the resolved path.
+    let request = ImageLoadRequest::new(sprout_image, ImageSource::ResolvedPath(&resolved));
+
+    // Load the driver image using the image loader support module.
     // 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))?;
+    let image = ImageLoader::load(request)?;
 
     // 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
     // just a standard EFI image.
-    uefi::boot::start_image(image).context("unable to start driver image")?;
+    uefi::boot::start_image(*image.handle()).context("unable to start driver image")?;
 
     Ok(())
 }

crates/eficore/src/lib.rs

@@ -6,6 +6,9 @@ extern crate alloc;
 /// EFI handle helpers.
 pub mod handle;
 
+/// Load and start EFI images.
+pub mod loader;
+
 /// Logging support for EFI applications.
 pub mod logger;
 

crates/eficore/src/loader.rs

@@ -0,0 +1,141 @@
+use crate::loader::source::ImageSource;
+use crate::secure::SecureBoot;
+use crate::shim::hook::SecurityHook;
+use crate::shim::{ShimInput, ShimSupport};
+use anyhow::{Context, Result, bail};
+use log::warn;
+use uefi::Handle;
+use uefi::boot::LoadImageSource;
+
+/// Represents EFI image sources generically.
+pub mod source;
+
+/// Handle to a loaded EFI image.
+pub struct ImageHandle {
+    /// Handle to the loaded image.
+    handle: Handle,
+}
+
+impl ImageHandle {
+    /// Create a new image handle based on a handle from the UEFI stack.
+    pub fn new(handle: Handle) -> Self {
+        Self { handle }
+    }
+
+    /// Retrieve the underlying handle.
+    pub fn handle(&self) -> &Handle {
+        &self.handle
+    }
+}
+
+/// Request to load an image from a source, with support for additional validation features.
+pub struct ImageLoadRequest<'source> {
+    /// Handle to the current image.
+    current_image: Handle,
+    /// Source of the image to load.
+    source: ImageSource<'source>,
+}
+
+impl<'source> ImageLoadRequest<'source> {
+    /// Create a new image load request with a current image and a source.
+    pub fn new(current_image: Handle, source: ImageSource<'source>) -> Self {
+        Self {
+            current_image,
+            source,
+        }
+    }
+
+    /// Retrieve the current image.
+    pub fn current_image(&self) -> &Handle {
+        &self.current_image
+    }
+
+    /// Retrieve the source of the image to load.
+    pub fn source(&'source self) -> &'source ImageSource<'source> {
+        &self.source
+    }
+
+    /// Convert the request into a source.
+    pub fn into_source(self) -> ImageSource<'source> {
+        self.source
+    }
+}
+
+/// EFI image loader.
+pub struct ImageLoader;
+
+impl ImageLoader {
+    /// Load an image using the image `request` which allows
+    pub fn load(request: ImageLoadRequest) -> Result<ImageHandle> {
+        // 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 = ShimSupport::loaded().context("unable to determine if shim is loaded")?;
+
+        // Determine whether the shim loader is available.
+        let shim_loader_available = ShimSupport::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.
+            ShimSupport::retain()?;
+        }
+
+        // Clone the current image handle to use for loading the image.
+        let current_image = *request.current_image();
+
+        // Converts the source to a shim input with an owned data buffer.
+        let input = ShimInput::from(request.into_source())
+            .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 = crate::shim::hook::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?;
+            }
+        }
+
+        // Assert the result and grab the handle.
+        let handle = result?;
+
+        // Retrieve the handle from the result and make a new image handle.
+        Ok(ImageHandle::new(handle))
+    }
+}

crates/eficore/src/loader/source.rs

@@ -0,0 +1,25 @@
+use crate::path::ResolvedPath;
+use crate::shim::ShimInput;
+
+/// Represents a source of an EFI image.
+pub enum ImageSource<'source> {
+    /// The image is located at the specified path that has been resolved.
+    ResolvedPath(&'source ResolvedPath),
+    /// The image is located in a buffer.
+    DataBuffer {
+        /// Optional path to the image.
+        path: Option<&'source ResolvedPath>,
+        /// Buffer containing the image.
+        buffer: &'source [u8],
+    },
+}
+
+/// Implement conversion from `ImageSource` to `ShimInput`, which is used by the shim support code.
+impl<'source> From<ImageSource<'source>> for ShimInput<'source> {
+    fn from(value: ImageSource<'source>) -> Self {
+        match value {
+            ImageSource::ResolvedPath(path) => ShimInput::ResolvedPath(path),
+            ImageSource::DataBuffer { path, buffer } => ShimInput::DataBuffer(path, buffer),
+        }
+    }
+}

crates/eficore/src/shim.rs

@@ -1,6 +1,4 @@
 use crate::path::ResolvedPath;
-use crate::secure::SecureBoot;
-use crate::shim::hook::SecurityHook;
 use crate::variables::{VariableClass, VariableController};
 use alloc::boxed::Box;
 use alloc::string::ToString;
@@ -8,9 +6,6 @@ use alloc::vec::Vec;
 use anyhow::{Context, Result, anyhow, bail};
 use core::ffi::c_void;
 use core::pin::Pin;
-use log::warn;
-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;
@@ -18,7 +13,7 @@ use uefi_raw::table::runtime::VariableVendor;
 use uefi_raw::{Guid, Status, guid};
 
 /// Security hook support.
-mod hook;
+pub mod hook;
 
 /// Support for the shim loader application for Secure Boot.
 pub struct ShimSupport;
@@ -237,72 +232,6 @@ impl ShimSupport {
             .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<()> {