Merge "Add KM_MIN_MAC_LENGTH tag to HMAC and AES-GCM keys." into mnc-dev

4 files changed, 55 insertions, 2 deletions

diff --git a/keystore/java/android/security/keystore/AndroidKeyStoreAuthenticatedAESCipherSpi.java b/keystore/java/android/security/keystore/AndroidKeyStoreAuthenticatedAESCipherSpi.java
index 5459bea..441ee66 100644
--- a/keystore/java/android/security/keystore/AndroidKeyStoreAuthenticatedAESCipherSpi.java
+++ b/keystore/java/android/security/keystore/AndroidKeyStoreAuthenticatedAESCipherSpi.java
@@ -51,7 +51,7 @@ import javax.crypto.spec.GCMParameterSpec;
 abstract class AndroidKeyStoreAuthenticatedAESCipherSpi extends AndroidKeyStoreCipherSpiBase {
 
     abstract static class GCM extends AndroidKeyStoreAuthenticatedAESCipherSpi {
-        private static final int MIN_SUPPORTED_TAG_LENGTH_BITS = 96;
+        static final int MIN_SUPPORTED_TAG_LENGTH_BITS = 96;
         private static final int MAX_SUPPORTED_TAG_LENGTH_BITS = 128;
         private static final int DEFAULT_TAG_LENGTH_BITS = 128;
         private static final int IV_LENGTH_BYTES = 12;
diff --git a/keystore/java/android/security/keystore/AndroidKeyStoreKeyGeneratorSpi.java b/keystore/java/android/security/keystore/AndroidKeyStoreKeyGeneratorSpi.java
index fd014eb..4c174f1 100644
--- a/keystore/java/android/security/keystore/AndroidKeyStoreKeyGeneratorSpi.java
+++ b/keystore/java/android/security/keystore/AndroidKeyStoreKeyGeneratorSpi.java
@@ -171,7 +171,7 @@ public abstract class AndroidKeyStoreKeyGeneratorSpi extends KeyGeneratorSpi {
                         "Key size must be positive: " + mKeySizeBits);
             } else if ((mKeySizeBits % 8) != 0) {
                 throw new InvalidAlgorithmParameterException(
-                        "Key size in must be a multiple of 8: " + mKeySizeBits);
+                        "Key size must be a multiple of 8: " + mKeySizeBits);
             }
 
             try {
@@ -272,6 +272,11 @@ public abstract class AndroidKeyStoreKeyGeneratorSpi extends KeyGeneratorSpi {
         KeymasterUtils.addUserAuthArgs(args,
                 spec.isUserAuthenticationRequired(),
                 spec.getUserAuthenticationValidityDurationSeconds());
+        KeymasterUtils.addMinMacLengthAuthorizationIfNecessary(
+                args,
+                mKeymasterAlgorithm,
+                mKeymasterBlockModes,
+                mKeymasterDigests);
         args.addDateIfNotNull(KeymasterDefs.KM_TAG_ACTIVE_DATETIME, spec.getKeyValidityStart());
         args.addDateIfNotNull(KeymasterDefs.KM_TAG_ORIGINATION_EXPIRE_DATETIME,
                 spec.getKeyValidityForOriginationEnd());
diff --git a/keystore/java/android/security/keystore/AndroidKeyStoreSpi.java b/keystore/java/android/security/keystore/AndroidKeyStoreSpi.java
index 88858de..915d86f 100644
--- a/keystore/java/android/security/keystore/AndroidKeyStoreSpi.java
+++ b/keystore/java/android/security/keystore/AndroidKeyStoreSpi.java
@@ -672,6 +672,11 @@ public class AndroidKeyStoreSpi extends KeyStoreSpi {
             KeymasterUtils.addUserAuthArgs(args,
                     params.isUserAuthenticationRequired(),
                     params.getUserAuthenticationValidityDurationSeconds());
+            KeymasterUtils.addMinMacLengthAuthorizationIfNecessary(
+                    args,
+                    keymasterAlgorithm,
+                    keymasterBlockModes,
+                    keymasterDigests);
             args.addDateIfNotNull(KeymasterDefs.KM_TAG_ACTIVE_DATETIME,
                     params.getKeyValidityStart());
             args.addDateIfNotNull(KeymasterDefs.KM_TAG_ORIGINATION_EXPIRE_DATETIME,
diff --git a/keystore/java/android/security/keystore/KeymasterUtils.java b/keystore/java/android/security/keystore/KeymasterUtils.java
index 92d636c..feafbfa 100644
--- a/keystore/java/android/security/keystore/KeymasterUtils.java
+++ b/keystore/java/android/security/keystore/KeymasterUtils.java
@@ -22,6 +22,8 @@ import android.security.KeyStore;
 import android.security.keymaster.KeymasterArguments;
 import android.security.keymaster.KeymasterDefs;
 
+import java.security.ProviderException;
+
 /**
  * @hide
  */
@@ -133,4 +135,45 @@ public abstract class KeymasterUtils {
                     userAuthenticationValidityDurationSeconds);
         }
     }
+
+    /**
+     * Adds {@code KM_TAG_MIN_MAC_LENGTH} tag, if necessary, to the keymaster arguments for
+     * generating or importing a key. This tag may only be needed for symmetric keys (e.g., HMAC,
+     * AES-GCM).
+     */
+    public static void addMinMacLengthAuthorizationIfNecessary(KeymasterArguments args,
+            int keymasterAlgorithm,
+            int[] keymasterBlockModes,
+            int[] keymasterDigests) {
+        switch (keymasterAlgorithm) {
+            case KeymasterDefs.KM_ALGORITHM_AES:
+                if (com.android.internal.util.ArrayUtils.contains(
+                        keymasterBlockModes, KeymasterDefs.KM_MODE_GCM)) {
+                    // AES GCM key needs the minimum length of AEAD tag specified.
+                    args.addUnsignedInt(KeymasterDefs.KM_TAG_MIN_MAC_LENGTH,
+                            AndroidKeyStoreAuthenticatedAESCipherSpi.GCM
+                                    .MIN_SUPPORTED_TAG_LENGTH_BITS);
+                }
+                break;
+            case KeymasterDefs.KM_ALGORITHM_HMAC:
+                // HMAC key needs the minimum length of MAC set to the output size of the associated
+                // digest. This is because we do not offer a way to generate shorter MACs and
+                // don't offer a way to verify MACs (other than by generating them).
+                if (keymasterDigests.length != 1) {
+                    throw new ProviderException(
+                            "Unsupported number of authorized digests for HMAC key: "
+                                    + keymasterDigests.length
+                                    + ". Exactly one digest must be authorized");
+                }
+                int keymasterDigest = keymasterDigests[0];
+                int digestOutputSizeBits = getDigestOutputSizeBits(keymasterDigest);
+                if (digestOutputSizeBits == -1) {
+                    throw new ProviderException(
+                            "HMAC key authorized for unsupported digest: "
+                                    + KeyProperties.Digest.fromKeymaster(keymasterDigest));
+                }
+                args.addUnsignedInt(KeymasterDefs.KM_TAG_MIN_MAC_LENGTH, digestOutputSizeBits);
+                break;
+        }
+    }
 }