kbs_protocol: support composite attestation for IBM SE

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

@@ -3,7 +3,7 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 
-use super::{Attester, TeeEvidence};
+use super::{utils::validate_and_pad_data, Attester, TeeEvidence};
 use anyhow::*;
 use pv::{
     misc,
@@ -14,7 +14,7 @@ use serde::{Deserialize, Serialize};
 use serde_with::{base64::Base64, serde_as};
 use tracing::debug;
 
-const RUNTIME_DIGEST_SIZE: usize = 48; // SHA-384 digest size in bytes
+const SE_REPORT_DATA_SIZE: usize = 64; // SHA-512 digest size in bytes
 
 /// Structured user data for IBM SEL attestation
 /// Currently, only contains runtime data digest bound to the attestation measurement
@@ -105,25 +105,11 @@ impl Attester for SeAttester {
             runtime_digest
         );
 
-        let runtime_digest = match runtime_digest.len() {
-            len if len > RUNTIME_DIGEST_SIZE => {
-                bail!(
-                    "Invalid runtime_data_digest length: expected {} bytes (SHA-384), got {} (too large)",
-                    RUNTIME_DIGEST_SIZE,
-                    len
-                );
-            }
-            len if len < RUNTIME_DIGEST_SIZE => {
-                debug!(
-                    "Padding runtime_data_digest from {} to {} bytes with zeros",
-                    len, RUNTIME_DIGEST_SIZE
-                );
-                let mut padded = runtime_digest;
-                padded.resize(RUNTIME_DIGEST_SIZE, 0);
-                padded
-            }
-            _ => runtime_digest, // Exact match, use as-is
-        };
+        let runtime_digest = validate_and_pad_data(
+            runtime_digest,
+            SE_REPORT_DATA_SIZE,
+            "runtime_data_digest (SHA-512)",
+        )?;
 
         let user_data = UserData {
             runtime_data_digest: runtime_digest,
@@ -224,64 +210,55 @@ mod tests {
 
     #[tokio::test]
     async fn test_runtime_data_digest_with_various_sizes() {
-        // Helper function that mimics the validation/padding logic from lines 110-129
-        fn process_runtime_digest(runtime_digest: Vec<u8>) -> Result<Vec<u8>> {
-            match runtime_digest.len() {
-                len if len > RUNTIME_DIGEST_SIZE => {
-                    bail!(
-                        "Invalid runtime_data_digest length: expected {} bytes (SHA-384), got {} (too large)",
-                        RUNTIME_DIGEST_SIZE,
-                        len
-                    )
-                }
-                len if len < RUNTIME_DIGEST_SIZE => {
-                    let mut padded = runtime_digest;
-                    padded.resize(RUNTIME_DIGEST_SIZE, 0);
-                    Ok(padded)
-                }
-                _ => Ok(runtime_digest), // Exact match, use as-is
-            }
-        }
-
-        // Case 1: Exact size (48 bytes) - should use as-is
-        let exact_digest = vec![0xAA; RUNTIME_DIGEST_SIZE];
-        let result = process_runtime_digest(exact_digest.clone()).unwrap();
-        assert_eq!(result.len(), RUNTIME_DIGEST_SIZE);
+        // Case 1: Exact size (64 bytes) - should use as-is
+        let exact_digest = vec![0xAA; SE_REPORT_DATA_SIZE];
+        let result = validate_and_pad_data(
+            exact_digest.clone(),
+            SE_REPORT_DATA_SIZE,
+            "runtime_data_digest",
+        )
+        .unwrap();
+        assert_eq!(result.len(), SE_REPORT_DATA_SIZE);
         assert_eq!(result, exact_digest);
 
-        // Case 2: Too small (< 48 bytes) - should be padded with zeros
+        // Case 2: Small size (< 64 bytes) - should be padded with zeros
         let small_test_cases = vec![
             (vec![], 0),                       // Empty digest
             (vec![0xAA], 1),                   // Single byte
             (vec![0xAA, 0xBB, 0xCC, 0xDD], 4), // 4 bytes
             (vec![0xFF; 32], 32),              // 32 bytes (SHA-256 size)
-            (vec![0x11; 47], 47),              // 47 bytes (just under limit)
+            (vec![0x11; 63], 63),              // 63 bytes (just under limit)
         ];
 
         for (small_digest, original_len) in small_test_cases {
-            let result = process_runtime_digest(small_digest.clone()).unwrap();
+            let result = validate_and_pad_data(
+                small_digest.clone(),
+                SE_REPORT_DATA_SIZE,
+                "runtime_data_digest",
+            )
+            .unwrap();
 
-            // Verify result is padded to 48 bytes
-            assert_eq!(result.len(), RUNTIME_DIGEST_SIZE);
+            // Verify result is padded to 64 bytes
+            assert_eq!(result.len(), SE_REPORT_DATA_SIZE);
 
             // Verify original data is preserved at the beginning
             assert_eq!(&result[..original_len], &small_digest[..]);
 
             // Verify zeros are padded at the end
-            for i in original_len..RUNTIME_DIGEST_SIZE {
+            for i in original_len..SE_REPORT_DATA_SIZE {
                 assert_eq!(result[i], 0, "Byte at index {} should be 0 (padded)", i);
             }
         }
 
-        // Case 3: Too large (> 48 bytes) - should return error
+        // Case 3: Large size (> 64 bytes) - should return error
         let large_test_cases = vec![
-            (vec![0xFF; 49], 49),   // 49 bytes (just over limit)
-            (vec![0xFF; 64], 64),   // 64 bytes (SHA-512 size)
+            (vec![0xFF; 65], 65),   // 65 bytes (just over limit)
             (vec![0xFF; 100], 100), // 100 bytes (way over limit)
         ];
 
         for (large_digest, len) in large_test_cases {
-            let result = process_runtime_digest(large_digest);
+            let result =
+                validate_and_pad_data(large_digest, SE_REPORT_DATA_SIZE, "runtime_data_digest");
 
             // Verify error is returned
             assert!(

attestation-agent/attester/src/utils.rs

@@ -8,6 +8,7 @@ use std::{env, path::Path};
 use anyhow::{bail, Result};
 use base64::{engine::general_purpose::STANDARD, Engine};
 use tokio::{fs::File, io::AsyncReadExt};
+use tracing::debug;
 
 pub fn pad<const T: usize>(input: &[u8]) -> [u8; T] {
     let mut output = [0; T];
@@ -20,6 +21,48 @@ pub fn pad<const T: usize>(input: &[u8]) -> [u8; T] {
     output
 }
 
+/// Validates and pads data to a specified size.
+///
+/// This function ensures that the input data does not exceed the expected size,
+/// and pads it with zeros if it's smaller than the expected size.
+///
+/// # Arguments
+///
+/// * `data` - The input data to validate and pad
+/// * `expected_size` - The target size for the data
+/// * `data_name` - A descriptive name for the data (used in error messages)
+///
+/// # Returns
+///
+/// * `Ok(Vec<u8>)` - The validated and padded data
+/// * `Err(anyhow::Error)` - If the data exceeds the expected size
+pub fn validate_and_pad_data(
+    data: Vec<u8>,
+    expected_size: usize,
+    data_name: &str,
+) -> Result<Vec<u8>> {
+    match data.len() {
+        len if len > expected_size => {
+            bail!(
+                "Invalid {} length: expected {} bytes, got {} (too large)",
+                data_name,
+                expected_size,
+                len
+            )
+        }
+        len if len < expected_size => {
+            debug!(
+                "Padding {} from {} to {} bytes with zeros",
+                data_name, len, expected_size
+            );
+            let mut padded = data;
+            padded.resize(expected_size, 0);
+            Ok(padded)
+        }
+        _ => Ok(data), // Exact match, use as-is
+    }
+}
+
 /// This is a fixed eventlog header. If no CCEL is found, we will use this header ahead
 /// of aael eventlog.
 ///

attestation-agent/kbs_protocol/src/client/rcar_client.rs

@@ -180,10 +180,6 @@ impl KbsClient<Box<dyn EvidenceProvider>> {
             // - injects runtime_data_digest into the request
             // The injected data will be used in SE attester's get_evidence method.
             Tee::Se => {
-                if !additional_evidence.is_empty() {
-                    bail!("Cannot attest multiple devices on s390x platform.")
-                }
-
                 #[cfg(feature = "se-attester")]
                 {
                     use attester::se::SeAttestationRequest;