sprout: measure xen and dom0 payloads and cmdlines into PCRs 9/11/12

Extend PCR 9 with the initrd, PCR 11 with the dom0 kernel,
and PCR 12 with the Xen options and dom0 cmdline.

Signed-off-by: Luca Di Maio <luca.dimaio1@gmail.com>

Author: 89luca89

crates/boot/src/actions/edera.rs

@@ -1,6 +1,6 @@
 use crate::{actions, context::SproutContext};
 use alloc::rc::Rc;
-use alloc::string::String;
+use alloc::vec::Vec;
 use alloc::{format, vec};
 use anyhow::{Context, Result};
 use edera_sprout_config::actions::chainload::ChainloadConfiguration;
@@ -12,74 +12,96 @@ use eficore::media_loader::{
         XEN_EFI_CONFIG_MEDIA_GUID, XEN_EFI_KERNEL_MEDIA_GUID, XEN_EFI_RAMDISK_MEDIA_GUID,
     },
 };
+use eficore::platform::tpm::PlatformTpm;
 use uefi::Guid;
 
-/// Builds a configuration string for the Xen EFI stub using the specified `configuration`.
-fn make_xen_config(context: Rc<SproutContext>, configuration: &EderaConfiguration) -> String {
-    let xen_options = combine_options(context.stamp_iter(configuration.xen_options.iter()));
-    let kernel_options = combine_options(context.stamp_iter(configuration.kernel_options.iter()));
-    build_xen_config(&xen_options, &kernel_options)
-}
-
-/// Register a media loader for some `text` with the vendor `guid`.
-/// `what` should indicate some identifying value for error messages
-/// like `config` or `kernel`.
-/// Provides a [MediaLoaderHandle] that can be used to unregister the media loader.
-fn register_media_loader_text(guid: Guid, what: &str, text: String) -> Result<MediaLoaderHandle> {
-    MediaLoaderHandle::register(guid, text.as_bytes().to_vec().into_boxed_slice())
-        .context(format!("unable to register {} media loader", what)) /*  */
-}
-
-/// Register a media loader for the file `path` with the vendor `guid`.
+/// Register a media loader for the provided `bytes` with the vendor `guid`.
 /// `what` should indicate some identifying value for error messages
 /// like `config` or `kernel`.
 /// Provides a [MediaLoaderHandle] that can be used to unregister the media loader.
-fn register_media_loader_file(
-    context: &Rc<SproutContext>,
+fn register_media_loader_bytes(
     guid: Guid,
     what: &str,
-    path: &str,
+    bytes: Vec<u8>,
 ) -> Result<MediaLoaderHandle> {
-    // Stamp the path to the file.
+    MediaLoaderHandle::register(guid, bytes.into_boxed_slice())
+        .context(format!("unable to register {} media loader", what))
+}
+
+/// Read the contents of the loader payload at `path` relative to the sprout image.
+/// `what` should indicate some identifying value for error messages
+/// like `kernel` or `initrd`.
+fn read_loader_payload(context: &Rc<SproutContext>, what: &str, path: &str) -> Result<Vec<u8>> {
     let path = context.stamp(path);
-    // Read the file contents.
-    let content =
-        eficore::path::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())
-        .context(format!("unable to register {} media loader", what))?;
-    Ok(handle)
+    eficore::path::read_file_contents(Some(context.root().loaded_image_path()?), &path)
+        .context(format!("unable to read {} file", what))
 }
 
 /// Executes the edera action which will boot the Edera hypervisor with the specified
 /// `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 = make_xen_config(context.clone(), configuration);
+    // Only register the initrd media loader if the user actually configured one.
+    let xen_opts = combine_options(context.stamp_iter(configuration.xen_options.iter()));
+    let dom0_args = combine_options(context.stamp_iter(configuration.kernel_options.iter()));
+
+    // Measure xen options and dom0 cmdline into PCR 12 in a fixed order.
+    PlatformTpm::log_event(
+        PlatformTpm::PCR_KERNEL_PARAMETERS,
+        xen_opts.as_bytes(),
+        "sprout: xen options",
+    )
+    .context("unable to measure xen options into the TPM")?;
+    PlatformTpm::log_event(
+        PlatformTpm::PCR_KERNEL_PARAMETERS,
+        dom0_args.as_bytes(),
+        "sprout: dom0 cmdline",
+    )
+    .context("unable to measure dom0 cmdline into the TPM")?;
+
+    // Build the Xen config text and register it as the config media loader. The
+    // assembled text is a derived artifact, intentionally not measured.
+    let config_handle = register_media_loader_bytes(
+        XEN_EFI_CONFIG_MEDIA_GUID,
+        "config",
+        build_xen_config(&xen_opts, &dom0_args).into_bytes(),
+    )
+    .context("unable to register config media loader")?;
 
-    // Register the media loader for the config.
-    let config = register_media_loader_text(XEN_EFI_CONFIG_MEDIA_GUID, "config", config)
-        .context("unable to register config media loader")?;
+    // Read the dom0 kernel, measure it into PCR 11, then register the kernel
+    // media loader.
+    let kernel_bytes = read_loader_payload(&context, "kernel", &configuration.kernel)?;
+    PlatformTpm::log_event(
+        PlatformTpm::PCR_KERNEL,
+        &kernel_bytes,
+        "sprout: dom0 kernel",
+    )
+    .context("unable to measure dom0 kernel into the TPM")?;
+    let kernel_handle =
+        register_media_loader_bytes(XEN_EFI_KERNEL_MEDIA_GUID, "kernel", kernel_bytes)
+            .context("unable to register kernel media loader")?;
 
-    // Register the media loaders for the kernel.
-    let kernel = register_media_loader_file(
-        &context,
-        XEN_EFI_KERNEL_MEDIA_GUID,
-        "kernel",
-        &configuration.kernel,
+    // Extend PCR 9 with the initrd bytes (empty when no initrd is
+    // configured).
+    let initrd_bytes = match empty_is_none(configuration.initrd.as_ref()) {
+        Some(p) => read_loader_payload(&context, "initrd", p)?,
+        None => Vec::new(),
+    };
+    PlatformTpm::log_event(
+        PlatformTpm::PCR_INITRD,
+        &initrd_bytes,
+        "sprout: dom0 initrd",
     )
-    .context("unable to register kernel media loader")?;
+    .context("unable to measure dom0 initrd into the TPM")?;
 
     // Create a vector of media loaders to drop them only after this function completes.
-    let mut media_loaders = vec![config, kernel];
+    let mut media_loaders = vec![config_handle, kernel_handle];
 
     // Register the initrd if it is provided.
-    if let Some(initrd) = empty_is_none(configuration.initrd.as_ref()) {
-        let initrd =
-            register_media_loader_file(&context, XEN_EFI_RAMDISK_MEDIA_GUID, "initrd", initrd)
+    if !initrd_bytes.is_empty() {
+        let initrd_handle =
+            register_media_loader_bytes(XEN_EFI_RAMDISK_MEDIA_GUID, "initrd", initrd_bytes)
                 .context("unable to register initrd media loader")?;
-        media_loaders.push(initrd);
+        media_loaders.push(initrd_handle);
     }
 
     // Chainload to the Xen EFI stub.

crates/eficore/src/platform/tpm.rs

@@ -38,6 +38,15 @@ impl PlatformTpm {
     /// The PCR for measuring the bootloader configuration into.
     pub const PCR_BOOT_LOADER_CONFIG: PcrIndex = PcrIndex(5);
 
+    /// The PCR for measuring the dom0 initrd payload into.
+    pub const PCR_INITRD: PcrIndex = PcrIndex(9);
+
+    /// The PCR for measuring the dom0 kernel payload into.
+    pub const PCR_KERNEL: PcrIndex = PcrIndex(11);
+
+    /// The PCR for measuring kernel command line and xen options into.
+    pub const PCR_KERNEL_PARAMETERS: PcrIndex = PcrIndex(12);
+
     /// Acquire access to the TPM protocol handle, if possible.
     /// Returns None if TPM is not available.
     fn protocol() -> Result<Option<TpmProtocolHandle>> {