AA/attester: support to read CCEL for kernel older than v6.4

attestation-agent/attester/Cargo.toml

@@ -59,7 +59,7 @@ all-attesters = [
 # quotes. It's an unconditional dependency for tdx-attester since that is the only way to
 # generate TDX quotes with upstream kernels.
 tsm-report = ["tempfile"]
-tdx-attester = ["scroll", "tsm-report", "tdx-attest-rs"]
+tdx-attester = ["scroll", "tsm-report", "tdx-attest-rs", "tokio/io-util"]
 sgx-attester = ["occlum_dcap"]
 az-snp-vtpm-attester = ["az-snp-vtpm"]
 az-tdx-vtpm-attester = ["az-snp-vtpm-attester", "az-tdx-vtpm"]

attestation-agent/attester/src/tdx/ccel.rs

@@ -0,0 +1,101 @@
+// Copyright (c) 2024 Alibaba Cloud
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+use anyhow::{bail, Context};
+use scroll::Pread;
+use tokio::io::{AsyncReadExt, AsyncSeekExt};
+
+use crate::tdx::TdxAttester;
+
+use std::path::Path;
+
+const CCEL_PATH: &str = "/sys/firmware/acpi/tables/data/CCEL";
+
+/// Path to the ACPI table CCEL description
+const CCEL_ACPI_DESCRIPTION: &str = "/sys/firmware/acpi/tables/CCEL";
+
+/// Guest memory which is used to read the CCEL
+const GUEST_MEMORY: &str = "/dev/mem";
+
+/// Signature of CCEL's ACPI Description Header
+const CCEL_SIGNATURE: &[u8] = b"CCEL";
+
+#[repr(C)]
+#[derive(Pread)]
+struct EfiAcpiDescriptionHeader {
+    signature: u32,
+    length: u32,
+    revision: u8,
+    checksum: u8,
+    oem_id: [u8; 6],
+    oem_table_id: u64,
+    oem_revision: u32,
+    craetor_id: u32,
+    creator_revision: u32,
+}
+
+#[repr(C)]
+#[derive(Pread)]
+struct TdxEventLogACPITable {
+    efi_acpi_description_header: EfiAcpiDescriptionHeader,
+    rsv: u32,
+    laml: u64,
+    lasa: u64,
+}
+
+impl TdxAttester {
+    pub async fn read_ccel() -> anyhow::Result<Vec<u8>> {
+        if Path::new(CCEL_PATH).exists() {
+            let ccel = tokio::fs::read(CCEL_PATH).await?;
+            return Ok(ccel);
+        }
+
+        let efi_acpi_description = tokio::fs::read(CCEL_ACPI_DESCRIPTION)
+            .await
+            .context("read ccel description")?;
+        let ccel_acpi_table = efi_acpi_description
+            .pread::<TdxEventLogACPITable>(0)
+            .context("parse CCEL ACPI description failed")?;
+
+        let ccel_signature = u32::from_le_bytes(CCEL_SIGNATURE.try_into()?);
+        if ccel_acpi_table.efi_acpi_description_header.signature != ccel_signature {
+            bail!("invalid CCEL ACPI table: wrong CCEL signature");
+        }
+
+        if ccel_acpi_table.rsv != 0 {
+            bail!("invalid CCEL ACPI table: RSV must be 0");
+        }
+
+        if ccel_acpi_table.efi_acpi_description_header.length != efi_acpi_description.len() as u32 {
+            bail!("invalid CCEL ACPI table: header length not match");
+        }
+
+        let mut guest_memory = tokio::fs::OpenOptions::new()
+            .read(true)
+            .open(GUEST_MEMORY)
+            .await?;
+        guest_memory
+            .seek(std::io::SeekFrom::Start(ccel_acpi_table.lasa))
+            .await?;
+        let mut ccel = vec![0; ccel_acpi_table.laml as usize];
+        let read_size = guest_memory.read(&mut ccel).await?;
+        if read_size == 0 {
+            bail!("read CCEL failed");
+        }
+
+        Ok(ccel)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tdx::TdxAttester;
+
+    #[ignore]
+    #[tokio::test]
+    async fn test_read_ccel() {
+        let _ccel = TdxAttester::read_ccel().await.unwrap();
+    }
+}

attestation-agent/attester/src/tdx/mod.rs

@@ -18,11 +18,11 @@ use std::fs;
 use std::path::Path;
 use tdx_attest_rs::tdx_report_t;
 
+mod ccel;
 mod report;
 mod rtmr;
 
 const TDX_REPORT_DATA_SIZE: usize = 64;
-const CCEL_PATH: &str = "/sys/firmware/acpi/tables/data/CCEL";
 
 pub fn detect_platform() -> bool {
     TsmReportPath::new(TsmReportProvider::Tdx).is_ok() || Path::new("/dev/tdx_guest").exists()
@@ -129,7 +129,7 @@ impl Attester for TdxAttester {
         let engine = base64::engine::general_purpose::STANDARD;
         let quote = engine.encode(quote_bytes);
 
-        let cc_eventlog = match std::fs::read(CCEL_PATH) {
+        let cc_eventlog = match Self::read_ccel().await {
             Result::Ok(el) => Some(engine.encode(el)),
             Result::Err(e) => {
                 log::warn!("Read CC Eventlog failed: {:?}", e);