identity: Fix attestation and documentation problems.

- The docs said that IdentityCredential.createEphemeralKey() returned
  data encoded PKCS#8 which is wrong. It's supposed to be in DER format
  which is also what the VTS tests and credstore expects.

- Clarify that createEphemeralKeyPair(), setReaderEphemeralPublicKey(),
  and createAuthChallenge() are all optional.

- Avoid passing an invalid profile ID in the IdentityCredentialTests.
  verifyOneProfileAndEntryPass test.

- Update requirements for which tags must be present in the attestation
  for CredentialKey as well as the requirements on expiration date and
  the issuer name.  Update default implementation to satisfy these
  requirements. Update VTS tests to carefully verify these requrements
  are met.

- Clarify requirements for X.509 cert for AuthenticationKey. Add VTS
  test to verify.

- Mandate that TAG_IDENTITY_CREDENTIAL_KEY must not be set for test
  credentials. Add VTS test to verify this.

- Make default implementation pretend to be implemented in a trusted
  environment and streamline VTS tests to not special-case for the
  default implementation.

- Switch to using the attestation extension parser from the KM 4.1
  support library instead of the one from system/keymaster. The latter
  one did not support the latest attestation extension and thus would
  fail for pretty much anything that wasn't the default HAL impl.

- Fix a couple of bugs in keymaster::V4_1::parse_attestation_record():
  - Report root_of_trust.security_level
  - Add support for Tag::IDENTITY_CREDENTIAL_KEY

- Fix how EMacKey is calculated.

- Add test vectors to verify how EMacKey and DeviceMac is calculated.

Test: atest VtsHalIdentityTargetTest
Test: atest android.security.identity.cts
Bug: 171745570
Change-Id: I2f8bd772de078556733f769cec2021918d1d7de6

1 files changed, 12 insertions, 34 deletions

diff --git a/identity/aidl/default/IdentityCredential.cpp b/identity/aidl/default/IdentityCredential.cpp
index 87d9a935de..dfcd4f557f 100644
--- a/identity/aidl/default/IdentityCredential.cpp
+++ b/identity/aidl/default/IdentityCredential.cpp
@@ -272,6 +272,7 @@ ndk::ScopedAStatus IdentityCredential::startRetrieval(
         const HardwareAuthToken& authToken, const vector<uint8_t>& itemsRequest,
         const vector<uint8_t>& signingKeyBlob, const vector<uint8_t>& sessionTranscript,
         const vector<uint8_t>& readerSignature, const vector<int32_t>& requestCounts) {
+    std::unique_ptr<cppbor::Item> sessionTranscriptItem;
     if (sessionTranscript.size() > 0) {
         auto [item, _, message] = cppbor::parse(sessionTranscript);
         if (item == nullptr) {
@@ -279,7 +280,7 @@ ndk::ScopedAStatus IdentityCredential::startRetrieval(
                     IIdentityCredentialStore::STATUS_INVALID_DATA,
                     "SessionTranscript contains invalid CBOR"));
         }
-        sessionTranscriptItem_ = std::move(item);
+        sessionTranscriptItem = std::move(item);
     }
     if (numStartRetrievalCalls_ > 0) {
         if (sessionTranscript_ != sessionTranscript) {
@@ -319,7 +320,7 @@ ndk::ScopedAStatus IdentityCredential::startRetrieval(
         vector<uint8_t> encodedReaderAuthentication =
                 cppbor::Array()
                         .add("ReaderAuthentication")
-                        .add(sessionTranscriptItem_->clone())
+                        .add(std::move(sessionTranscriptItem))
                         .add(cppbor::Semantic(24, itemsRequestBytes))
                         .encode();
         vector<uint8_t> encodedReaderAuthenticationBytes =
@@ -776,13 +777,6 @@ ndk::ScopedAStatus IdentityCredential::finishRetrieval(vector<uint8_t>* outMac,
     optional<vector<uint8_t>> mac;
     if (signingKeyBlob_.size() > 0 && sessionTranscript_.size() > 0 &&
         readerPublicKey_.size() > 0) {
-        cppbor::Array array;
-        array.add("DeviceAuthentication");
-        array.add(sessionTranscriptItem_->clone());
-        array.add(docType_);
-        array.add(cppbor::Semantic(24, encodedDeviceNameSpaces));
-        vector<uint8_t> deviceAuthenticationBytes = cppbor::Semantic(24, array.encode()).encode();
-
         vector<uint8_t> docTypeAsBlob(docType_.begin(), docType_.end());
         optional<vector<uint8_t>> signingKey =
                 support::decryptAes128Gcm(storageKey_, signingKeyBlob_, docTypeAsBlob);
@@ -792,31 +786,15 @@ ndk::ScopedAStatus IdentityCredential::finishRetrieval(vector<uint8_t>* outMac,
                     "Error decrypting signingKeyBlob"));
         }
 
-        optional<vector<uint8_t>> sharedSecret =
-                support::ecdh(readerPublicKey_, signingKey.value());
-        if (!sharedSecret) {
-            return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_FAILED, "Error doing ECDH"));
-        }
-
-        // Mix-in SessionTranscriptBytes
         vector<uint8_t> sessionTranscriptBytes = cppbor::Semantic(24, sessionTranscript_).encode();
-        vector<uint8_t> sharedSecretWithSessionTranscriptBytes = sharedSecret.value();
-        std::copy(sessionTranscriptBytes.begin(), sessionTranscriptBytes.end(),
-                  std::back_inserter(sharedSecretWithSessionTranscriptBytes));
-
-        vector<uint8_t> salt = {0x00};
-        vector<uint8_t> info = {};
-        optional<vector<uint8_t>> derivedKey =
-                support::hkdf(sharedSecretWithSessionTranscriptBytes, salt, info, 32);
-        if (!derivedKey) {
+        optional<vector<uint8_t>> eMacKey =
+                support::calcEMacKey(signingKey.value(), readerPublicKey_, sessionTranscriptBytes);
+        if (!eMacKey) {
             return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                    IIdentityCredentialStore::STATUS_FAILED,
-                    "Error deriving key from shared secret"));
+                    IIdentityCredentialStore::STATUS_FAILED, "Error calculating EMacKey"));
         }
-
-        mac = support::coseMac0(derivedKey.value(), {},      // payload
-                                deviceAuthenticationBytes);  // detached content
+        mac = support::calcMac(sessionTranscript_, docType_, encodedDeviceNameSpaces,
+                               eMacKey.value());
         if (!mac) {
             return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
                     IIdentityCredentialStore::STATUS_FAILED, "Error MACing data"));
@@ -830,9 +808,9 @@ ndk::ScopedAStatus IdentityCredential::finishRetrieval(vector<uint8_t>* outMac,
 
 ndk::ScopedAStatus IdentityCredential::generateSigningKeyPair(
         vector<uint8_t>* outSigningKeyBlob, Certificate* outSigningKeyCertificate) {
-    string serialDecimal = "0";  // TODO: set serial to something unique
-    string issuer = "Android Open Source Project";
-    string subject = "Android IdentityCredential Reference Implementation";
+    string serialDecimal = "1";
+    string issuer = "Android Identity Credential Key";
+    string subject = "Android Identity Credential Authentication Key";
     time_t validityNotBefore = time(nullptr);
     time_t validityNotAfter = validityNotBefore + 365 * 24 * 3600;