A CCA attestation token is a collection of claims about the state of a
Realm and of the CCA platform on which the Realm is running.
A CCA attestation token consists of two parts:
* Realm token - Contains attributes of the Realm, including:
# Realm Initial Measurement
# Realm Extensible Measurements
* CCA platform token - Contains attributes of the CCA platform
on which the Realm is running, including:
# CCA platform identity
# CCA platform life cycle state
# CCA platform software component measurements
The CCA attestation token is used by a verification service to validate
these claims.
The Realm Service Interface defines the following interfaces to retrieve
an attestation token from the Realm Management Monitor (RMM).
- RSI_ATTESTATION_TOKEN_INIT
- RSI_ATTESTATION_TOKEN_CONTINUE
Therefore, update the ArmCcaRsiLib to add an interface to get an
attestation token from the RMM.
Signed-off-by: Sami Mujawar <sami.muja...@arm.com>
---
ArmVirtPkg/Include/Library/ArmCcaRsiLib.h | 42 +++++
ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsi.h | 10 +-
ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsiLib.c | 193 ++++++++++++++++++++
3 files changed, 241 insertions(+), 4 deletions(-)
diff --git a/ArmVirtPkg/Include/Library/ArmCcaRsiLib.h
b/ArmVirtPkg/Include/Library/ArmCcaRsiLib.h
index
ae798a2feb9c3c417f06b7c2dfdb49479731df52..fe176d83c4b11d3f7bb35c97ec8ef00a4f47f981
100644
--- a/ArmVirtPkg/Include/Library/ArmCcaRsiLib.h
+++ b/ArmVirtPkg/Include/Library/ArmCcaRsiLib.h
@@ -31,6 +31,19 @@
*/
#define RIPAS_TYPE_MASK 0xFF
+/* Maximum attestation token size
+ RBXKKY The size of an attestation token is no larger than 4KB.
+*/
+#define MAX_ATTESTATION_TOKEN_SIZE SIZE_4KB
+
+/* Maximum challenge data size in bits.
+*/
+#define MAX_CHALLENGE_DATA_SIZE_BITS 512
+
+/* Minimum recommended challenge data size in bits.
+*/
+#define MIN_CHALLENGE_DATA_SIZE_BITS 256
+
/** An enum describing the RSI RIPAS.
See Section A5.2.2 Realm IPA state, RMM Specification, version A-bet0
*/
@@ -51,6 +64,35 @@ typedef struct RealmConfig {
UINT8 Reserved[SIZE_4KB - sizeof (UINT64)];
} REALM_CONFIG;
+/**
+ Retrieve an attestation token from the RMM.
+
+ @param [in] ChallengeData Pointer to the challenge data to be
+ included in the attestation token.
+ @param [in] ChallengeDataSizeBits Size of the challenge data in bits.
+ @param [out] TokenBuffer Pointer to a buffer to store the
+ retrieved attestation token.
+ @param [in, out] TokenBufferSize Size of the token buffer on input and
+ number of bytes stored in token
buffer
+ on return.
+
+ @retval RETURN_SUCCESS Success.
+ @retval RETURN_INVALID_PARAMETER A parameter is invalid.
+ @retval RETURN_ABORTED The operation was aborted as the state
+ of the Realm or REC does not match the
+ state expected by the command.
+ @retval RETURN_NOT_READY The operation requested by the command
+ is not complete.
+**/
+RETURN_STATUS
+EFIAPI
+RsiGetAttestationToken (
+ IN CONST UINT8 *CONST ChallengeData,
+ IN UINT64 ChallengeDataSizeBits,
+ OUT UINT8 *CONST TokenBuffer,
+ IN OUT UINT64 *CONST TokenBufferSize
+ );
+
/**
Returns the IPA state for the page pointed by the address.
diff --git a/ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsi.h
b/ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsi.h
index
9cc12bc5a70b457367077d0b26011c3b91fa63c9..325234d06695befc840dcf37e951130dfe0550c3
100644
--- a/ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsi.h
+++ b/ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsi.h
@@ -18,10 +18,12 @@
#define ARM_CCA_RSI_H_
// FIDs for Realm Service Interface calls.
-#define FID_RSI_IPA_STATE_GET 0xC4000198
-#define FID_RSI_IPA_STATE_SET 0xC4000197
-#define FID_RSI_REALM_CONFIG 0xC4000196
-#define FID_RSI_VERSION 0xC4000190
+#define FID_RSI_ATTESTATION_TOKEN_CONTINUE 0xC4000195
+#define FID_RSI_ATTESTATION_TOKEN_INIT 0xC4000194
+#define FID_RSI_IPA_STATE_GET 0xC4000198
+#define FID_RSI_IPA_STATE_SET 0xC4000197
+#define FID_RSI_REALM_CONFIG 0xC4000196
+#define FID_RSI_VERSION 0xC4000190
/** RSI Command Return codes
See Section B4.4.1, RMM Specification, version A-bet0.
diff --git a/ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsiLib.c
b/ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsiLib.c
index
546df9a94cb86533b37fef7e42fdaf7b8563052d..01ecee3a6798c0e5cefd9fb4f48788d3063c94cd
100644
--- a/ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsiLib.c
+++ b/ArmVirtPkg/Library/ArmCcaRsiLib/ArmCcaRsiLib.c
@@ -82,6 +82,199 @@ AddrIsGranuleAligned (
return TRUE;
}
+/**
+ Continue the operation to retrieve an attestation token.
+
+ @param [out] TokenBuffer Pointer to a buffer to store the
+ retrieved attestation token.
+ @param [in,out] TokenSize On input size of the token buffer,
+ and on output size of the token
+ returned if operation is successful,
+ otherwise 0.
+
+ @retval RETURN_SUCCESS Success.
+ @retval RETURN_INVALID_PARAMETER A parameter is invalid.
+ @retval RETURN_ABORTED The operation was aborted as the state
+ of the Realm or REC does not match the
+ state expected by the command.
+ @retval RETURN_NOT_READY The operation requested by the command
+ is not complete.
+ **/
+STATIC
+RETURN_STATUS
+EFIAPI
+RsiAttestationTokenContinue (
+ OUT UINT8 *CONST TokenBuffer,
+ OUT UINT64 *CONST TokenSize
+ )
+{
+ RETURN_STATUS Status;
+ ARM_SMC_ARGS SmcCmd;
+
+ ZeroMem (&SmcCmd, sizeof (SmcCmd));
+ SmcCmd.Arg0 = FID_RSI_ATTESTATION_TOKEN_CONTINUE;
+ // Set the IPA of the Granule to which the token will be written.
+ SmcCmd.Arg1 = (UINTN)TokenBuffer;
+
+ ArmCallSmc (&SmcCmd);
+ Status = RsiCmdStatusToEfiStatus (SmcCmd.Arg0);
+ if (!RETURN_ERROR (Status)) {
+ // Update the token size
+ *TokenSize = SmcCmd.Arg1;
+ } else {
+ // Clear the TokenBuffer on error.
+ ZeroMem (TokenBuffer, *TokenSize);
+ *TokenSize = 0;
+ }
+
+ return Status;
+}
+
+/**
+ Initialize the operation to retrieve an attestation token.
+
+ @param [in] ChallengeData Pointer to the challenge data to be
+ included in the attestation token.
+ @param [in] ChallengeDataSizeBits Size of the challenge data in bits.
+ @param [in] TokenBuffer Pointer to a buffer to store the
+ retrieved attestation token.
+
+ @retval RETURN_SUCCESS Success.
+ @retval RETURN_INVALID_PARAMETER A parameter is invalid.
+ **/
+STATIC
+RETURN_STATUS
+EFIAPI
+RsiAttestationTokenInit (
+ IN CONST UINT8 *CONST ChallengeData,
+ IN UINT64 ChallengeDataSizeBits,
+ IN UINT8 *CONST TokenBuffer
+ )
+{
+ ARM_SMC_ARGS SmcCmd;
+ UINT8 *Buffer8;
+ CONST UINT8 *Data8;
+ UINT64 Count;
+ UINT8 TailBits;
+
+ /* See A7.2.2 Attestation token generation, RMM Specification, version A-bet0
+ IWTKDD - If the size of the challenge provided by the relying party is
less
+ than 64 bytes, it should be zero-padded prior to calling
+ RSI_ATTESTATION_TOKEN_INIT.
+
+ Therefore, zero out the SmcCmd memory before coping the ChallengeData
+ bits.
+ */
+ ZeroMem (&SmcCmd, sizeof (SmcCmd));
+ SmcCmd.Arg0 = FID_RSI_ATTESTATION_TOKEN_INIT;
+ // Set the IPA of the Granule to which the token will be written.
+ SmcCmd.Arg1 = (UINTN)TokenBuffer;
+
+ // Copy challenge data.
+ Buffer8 = (UINT8 *)&SmcCmd.Arg2;
+ Data8 = ChallengeData;
+
+ // First copy whole bytes
+ Count = ChallengeDataSizeBits >> 3;
+ CopyMem (Buffer8, Data8, Count);
+
+ // Now copy any remaining tail bits.
+ TailBits = ChallengeDataSizeBits & (8 - 1);
+ if (TailBits > 0) {
+ // Advance buffer pointers.
+ Buffer8 += Count;
+ Data8 += Count;
+
+ // Copy tail byte.
+ *Buffer8 = *Data8;
+
+ // Clear unused tail bits.
+ *Buffer8 &= ~(0xFF << TailBits);
+ }
+
+ ArmCallSmc (&SmcCmd);
+ return RsiCmdStatusToEfiStatus (SmcCmd.Arg0);
+}
+
+/**
+ Retrieve an attestation token from the RMM.
+
+ @param [in] ChallengeData Pointer to the challenge data to be
+ included in the attestation token.
+ @param [in] ChallengeDataSizeBits Size of the challenge data in bits.
+ @param [out] TokenBuffer Pointer to a buffer to store the
+ retrieved attestation token.
+ @param [in, out] TokenBufferSize Size of the token buffer on input and
+ number of bytes stored in token
buffer
+ on return.
+
+ @retval RETURN_SUCCESS Success.
+ @retval RETURN_INVALID_PARAMETER A parameter is invalid.
+ @retval RETURN_ABORTED The operation was aborted as the state
+ of the Realm or REC does not match the
+ state expected by the command.
+ @retval RETURN_NOT_READY The operation requested by the command
+ is not complete.
+**/
+RETURN_STATUS
+EFIAPI
+RsiGetAttestationToken (
+ IN CONST UINT8 *CONST ChallengeData,
+ IN UINT64 ChallengeDataSizeBits,
+ OUT UINT8 *CONST TokenBuffer,
+ IN OUT UINT64 *CONST TokenBufferSize
+ )
+{
+ RETURN_STATUS Status;
+
+ if ((TokenBuffer == NULL) ||
+ (TokenBufferSize == NULL) ||
+ (ChallengeData == NULL))
+ {
+ return RETURN_INVALID_PARAMETER;
+ }
+
+ if (*TokenBufferSize < MAX_ATTESTATION_TOKEN_SIZE) {
+ *TokenBufferSize = MAX_ATTESTATION_TOKEN_SIZE;
+ return RETURN_BAD_BUFFER_SIZE;
+ }
+
+ if (!AddrIsGranuleAligned ((UINT64 *)TokenBuffer)) {
+ DEBUG ((DEBUG_ERROR, "ERROR : Token buffer not granule aligned\n"));
+ return RETURN_INVALID_PARAMETER;
+ }
+
+ if (ChallengeDataSizeBits > MAX_CHALLENGE_DATA_SIZE_BITS) {
+ return RETURN_INVALID_PARAMETER;
+ }
+
+ /* See A7.2.2 Attestation token generation, RMM Specification, version A-bet0
+ IWTKDD - Arm recommends that the challenge should contain at least 32
bytes
+ of unique data.
+ */
+ if (ChallengeDataSizeBits < MIN_CHALLENGE_DATA_SIZE_BITS) {
+ DEBUG ((DEBUG_WARN, "Minimum Challenge data size should be 32 bytes\n"));
+ }
+
+ Status = RsiAttestationTokenInit (
+ ChallengeData,
+ ChallengeDataSizeBits,
+ TokenBuffer
+ );
+ if (RETURN_ERROR (Status)) {
+ ASSERT (0);
+ return Status;
+ }
+
+ /* Loop until the token is ready or there is an error.
+ */
+ do {
+ Status = RsiAttestationTokenContinue (TokenBuffer, TokenBufferSize);
+ } while (Status == RETURN_NOT_READY);
+
+ return Status;
+}
+
/**
Returns the IPA state for the page pointed by the address.
--
'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'
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