identity: Fix for atttestion requirements and how EMacKey is calculated.

Test: atest VtsHalIdentityTargetTest
Test: atest android.security.identity.cts
Bug: 171745570
Change-Id: Ie9018b23e899721751fa327db851726a694570aa
Merged-In: If1afa2dd59c3c97337fd81bb6100334ebe0ad777
diff --git a/tests/tests/identity/src/android/security/identity/cts/AttestationTest.java b/tests/tests/identity/src/android/security/identity/cts/AttestationTest.java
index 06ae8ab..c63b793 100644
--- a/tests/tests/identity/src/android/security/identity/cts/AttestationTest.java
+++ b/tests/tests/identity/src/android/security/identity/cts/AttestationTest.java
@@ -102,16 +102,6 @@
         // Since we cannot get the implementation name or author at this layer, we can't test for
         // it. This can be tested for in the VTS test, however.
 
-        // As per the IC HAL, the keymasterVersion field should be the version of the Identity
-        // Credential HAL - 1.0 - and this is encoded as major*10 + minor. This field is used by
-        // Keymaster which is known to report integers less than or equal to 4 (for KM up to 4.0)
-        // and integers greater or equal than 41 (for KM starting with 4.1).
-        //
-        // Since we won't get to version 4.0 of the IC HAL for a while, let's also check that a KM
-        // version isn't errornously returned.
-        assertTrue(record.getKeymasterVersion() >= 10);
-        assertTrue(record.getKeymasterVersion() < 40);
-
         // Check that the challenge we passed in, is in fact in the attestation record.
         assertArrayEquals(challenge, record.getAttestationChallenge());
 
diff --git a/tests/tests/identity/src/android/security/identity/cts/Util.java b/tests/tests/identity/src/android/security/identity/cts/Util.java
index df9a300..bbd6ee7 100644
--- a/tests/tests/identity/src/android/security/identity/cts/Util.java
+++ b/tests/tests/identity/src/android/security/identity/cts/Util.java
@@ -37,6 +37,7 @@
 import java.security.KeyStore;
 import java.security.KeyPair;
 import java.security.KeyPairGenerator;
+import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.security.PublicKey;
 import java.security.PrivateKey;
@@ -1002,15 +1003,10 @@
 
             byte[] sessionTranscriptBytes =
                     Util.prependSemanticTagForEncodedCbor(encodedSessionTranscript);
-            byte[] sharedSecretWithSessionTranscriptBytes =
-                    Util.concatArrays(sharedSecret, sessionTranscriptBytes);
 
-            byte[] salt = new byte[1];
-            byte[] info = new byte[0];
-
-            salt[0] = 0x00;
-            byte[] derivedKey = Util.computeHkdf("HmacSha256",
-                    sharedSecretWithSessionTranscriptBytes, salt, info, 32);
+            byte[] salt = MessageDigest.getInstance("SHA-256").digest(sessionTranscriptBytes);
+            byte[] info = new byte[] {'E', 'M', 'a', 'c', 'K', 'e', 'y'};
+            byte[] derivedKey = Util.computeHkdf("HmacSha256", sharedSecret, salt, info, 32);
             SecretKey secretKey = new SecretKeySpec(derivedKey, "");
             return secretKey;
         } catch (InvalidKeyException