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fix(sev): verify firmware's SEV metadata signature #408

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Merged
Lencerf merged 1 commit into from
Feb 24, 2026
+10 −0
Merged

fix(sev): verify firmware's SEV metadata signature #408

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3 changes: 3 additions & 0 deletions alioth/src/firmware/firmware.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ use snafu::Snafu;

use crate::errors::{DebugTrace, trace_error};

use self::ovmf::x86_64::sev::SEV_SIGNATURE;
use self::ovmf::x86_64::tdx::{TDVF_SIGNATURE, TDVF_VERSION};

#[trace_error]
Expand All @@ -36,6 +37,8 @@ pub enum Error {
MissingMetadata { name: &'static str },
#[snafu(display("Firmware missing TDVF signature {TDVF_SIGNATURE:08x}, got {got:08x}"))]
MissingTdvfSignature { got: u32 },
#[snafu(display("Firmware missing AMD-SEV signature {SEV_SIGNATURE:08x}, got {got:08x}"))]
MissingAmdSevSignature { got: u32 },
#[snafu(display("Firmware missing TDVF version {TDVF_VERSION}, got {got}"))]
MissingTdvfVersion { got: u32 },
#[snafu(display("Invalid firmware data layout"))]
Expand Down
7 changes: 7 additions & 0 deletions alioth/src/firmware/ovmf/ovmf_x86_64/sev.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@ pub const GUID_SEV_ES_RESET_BLOCK: [u8; GUID_SIZE] = [
pub const GUID_SEV_METADATA: [u8; GUID_SIZE] = [
0x66, 0x65, 0x88, 0xdc, 0x4a, 0x98, 0x98, 0x47, 0xA7, 0x5e, 0x55, 0x85, 0xa7, 0xbf, 0x67, 0xcc,
];
pub const SEV_SIGNATURE: u32 = u32::from_le_bytes(*b"ASEV");

#[derive(Debug, KnownLayout, Immutable, FromBytes, IntoBytes)]
#[repr(C)]
Expand Down Expand Up @@ -102,6 +103,12 @@ pub fn parse_desc(data: &[u8]) -> Result<&[SevMetadataDesc]> {
let Ok((metadata, remain)) = SevMetaData::ref_from_prefix(&data[offset..]) else {
return error::InvalidLayout.fail();
};
if metadata.signature != SEV_SIGNATURE {
return error::MissingAmdSevSignature {
got: metadata.signature,
}
.fail();
};
let Ok((entries, _)) =
<[SevMetadataDesc]>::ref_from_prefix_with_elems(remain, metadata.num_desc as usize)
else {
Expand Down