fix(options): stamp initrd and combine options safely by ignoring empty strings

src/actions/chainload.rs

@@ -53,13 +53,9 @@ pub fn chainload(context: Rc<SproutContext>, configuration: &ChainloadConfigurat
     let mut loaded_image_protocol = uefi::boot::open_protocol_exclusive::<LoadedImage>(image)
         .context("unable to open loaded image protocol")?;
 
-    // Stamp and concatenate the options to pass to the image.
-    let options = configuration
-        .options
-        .iter()
-        .map(|item| context.stamp(item))
-        .collect::<Vec<_>>()
-        .join(" ");
+    // Stamp and combine the options to pass to the image.
+    let options =
+        utils::combine_options(configuration.options.iter().map(|item| context.stamp(item)));
 
     // Pass the options to the image, if any are provided.
     // The holder must drop at the end of this function to ensure the options are not leaked,
@@ -90,16 +86,14 @@ pub fn chainload(context: Rc<SproutContext>, configuration: &ChainloadConfigurat
     }
 
     // The initrd can be None or empty, so we need to collapse that into a single Option.
-    let initrd = configuration
-        .linux_initrd
-        .as_ref()
-        .map(|path| context.stamp(path))
-        .and_then(|path| if path.is_empty() { None } else { Some(path) });
+    let initrd = utils::empty_is_none(configuration.linux_initrd.as_ref());
 
     // If an initrd is provided, register it with the EFI stack.
     let mut initrd_handle = None;
-    if let Some(ref linux_initrd) = initrd {
-        let content = utils::read_file_contents(context.root().loaded_image_path()?, linux_initrd)
+    if let Some(linux_initrd) = initrd {
+        // Stamp the path to the initrd.
+        let linux_initrd = context.stamp(linux_initrd);
+        let content = utils::read_file_contents(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())

src/actions/edera.rs

@@ -40,7 +40,23 @@ pub struct EderaConfiguration {
 }
 
 /// Builds a configuration string for the Xen EFI stub using the specified `configuration`.
-fn build_xen_config(configuration: &EderaConfiguration) -> String {
+fn build_xen_config(context: Rc<SproutContext>, configuration: &EderaConfiguration) -> String {
+    // Stamp xen options and combine them.
+    let xen_options = utils::combine_options(
+        configuration
+            .xen_options
+            .iter()
+            .map(|item| context.stamp(item)),
+    );
+
+    // Stamp kernel options and combine them.
+    let kernel_options = utils::combine_options(
+        configuration
+            .kernel_options
+            .iter()
+            .map(|item| context.stamp(item)),
+    );
+
     // xen config file format is ini-like
     [
         // global section
@@ -50,10 +66,10 @@ fn build_xen_config(configuration: &EderaConfiguration) -> String {
         // configuration section for sprout
         "[sprout]".to_string(),
         // xen options
-        format!("options={}", configuration.xen_options.join(" ")),
+        format!("options={}", xen_options),
         // kernel options, stub replaces the kernel path
         // the kernel is provided via media loader
-        format!("kernel=stub {}", configuration.kernel_options.join(" ")),
+        format!("kernel=stub {}", kernel_options),
         // required or else the last line will be ignored
         "".to_string(),
     ]
@@ -94,7 +110,7 @@ fn register_media_loader_file(
 /// `configuration` and `context`. This action uses Edera-specific Xen EFI stub functionality.
 pub fn edera(context: Rc<SproutContext>, configuration: &EderaConfiguration) -> Result<()> {
     // Build the Xen config file content for this configuration.
-    let config = build_xen_config(configuration);
+    let config = build_xen_config(context.clone(), configuration);
 
     // Register the media loader for the config.
     let config = register_media_loader_text(XEN_EFI_CONFIG_MEDIA_GUID, "config", config)
@@ -113,7 +129,7 @@ pub fn edera(context: Rc<SproutContext>, configuration: &EderaConfiguration) ->
     let mut media_loaders = vec![config, kernel];
 
     // Register the initrd if it is provided.
-    if let Some(ref initrd) = configuration.initrd {
+    if let Some(initrd) = utils::empty_is_none(configuration.initrd.as_ref()) {
         let initrd =
             register_media_loader_file(&context, XEN_EFI_RAMDISK_MEDIA_GUID, "initrd", initrd)
                 .context("unable to register initrd media loader")?;
@@ -131,7 +147,7 @@ pub fn edera(context: Rc<SproutContext>, configuration: &EderaConfiguration) ->
     )
     .context("unable to chainload to xen");
 
-    // Unregister the media loaders on error.
+    // Unregister the media loaders when an error happens.
     for media_loader in media_loaders {
         if let Err(error) = media_loader.unregister() {
             error!("unable to unregister media loader: {}", error);

src/utils.rs

@@ -161,3 +161,17 @@ pub fn read_file_contents(default_root_path: &DevicePath, input: &str) -> Result
     let content = fs.read(Path::new(&path));
     content.context("unable to read file contents")
 }
+
+/// Filter a string-like Option `input` such that an empty string is [None].
+pub fn empty_is_none<T: AsRef<str>>(input: Option<T>) -> Option<T> {
+    input.filter(|input| !input.as_ref().is_empty())
+}
+
+/// Combine a sequence of strings into a single string, separated by spaces, ignoring empty strings.
+pub fn combine_options<T: AsRef<str>>(options: impl Iterator<Item = T>) -> String {
+    options
+        .flat_map(|item| empty_is_none(Some(item)))
+        .map(|item| item.as_ref().to_string())
+        .collect::<Vec<_>>()
+        .join(" ")
+}