From 46faab535f74e12f1d74fb50125c8a9475c636ba Mon Sep 17 00:00:00 2001
From: Eran Messeri <eranm@google.com>
Date: Tue, 10 May 2022 10:07:42 +0100
Subject: [PATCH] Keystore: Wire up Ed25519 signing

Wire Ed25519 signing into Keystore. This consists of registering a
provider for Ed25519.

Ed25519 has its own digest scheme, so the caller should specify "none"
as the digest scheme, and that's the tag that's going to be passed into
KeyMint.
However, unlike other uses of the "NONE" digest scheme, the input to the
signature algorithm should not be truncated.

Bug: 194359292
Test: atest android.keystore.cts.Curve25519Test
Change-Id: Icce4f7f2f8fa10081a9c6beff4813c2d91756469
---
 .../AndroidKeyStoreBCWorkaroundProvider.java  |  2 ++
 .../AndroidKeyStoreECDSASignatureSpi.java     | 24 +++++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/keystore/java/android/security/keystore2/AndroidKeyStoreBCWorkaroundProvider.java b/keystore/java/android/security/keystore2/AndroidKeyStoreBCWorkaroundProvider.java
index 9ad6f3adbd33d..6fff52a200626 100644
--- a/keystore/java/android/security/keystore2/AndroidKeyStoreBCWorkaroundProvider.java
+++ b/keystore/java/android/security/keystore2/AndroidKeyStoreBCWorkaroundProvider.java
@@ -206,6 +206,8 @@ class AndroidKeyStoreBCWorkaroundProvider extends Provider {
 
         putSignatureImpl("NONEwithECDSA",
                 PACKAGE_NAME + ".AndroidKeyStoreECDSASignatureSpi$NONE");
+        putSignatureImpl("Ed25519",
+                PACKAGE_NAME + ".AndroidKeyStoreECDSASignatureSpi$Ed25519");
 
         putSignatureImpl("SHA1withECDSA", PACKAGE_NAME + ".AndroidKeyStoreECDSASignatureSpi$SHA1");
         put("Alg.Alias.Signature.ECDSA", "SHA1withECDSA");
diff --git a/keystore/java/android/security/keystore2/AndroidKeyStoreECDSASignatureSpi.java b/keystore/java/android/security/keystore2/AndroidKeyStoreECDSASignatureSpi.java
index 8289671de2124..5216a908826b4 100644
--- a/keystore/java/android/security/keystore2/AndroidKeyStoreECDSASignatureSpi.java
+++ b/keystore/java/android/security/keystore2/AndroidKeyStoreECDSASignatureSpi.java
@@ -29,7 +29,10 @@ import libcore.util.EmptyArray;
 import java.io.ByteArrayOutputStream;
 import java.security.InvalidKeyException;
 import java.security.SignatureSpi;
+import java.security.spec.NamedParameterSpec;
+import java.util.Arrays;
 import java.util.List;
+import java.util.Set;
 
 /**
  * Base class for {@link SignatureSpi} providing Android KeyStore backed ECDSA signatures.
@@ -37,6 +40,10 @@ import java.util.List;
  * @hide
  */
 abstract class AndroidKeyStoreECDSASignatureSpi extends AndroidKeyStoreSignatureSpiBase {
+    private static final Set<String> ACCEPTED_SIGNING_SCHEMES = Set.of(
+            KeyProperties.KEY_ALGORITHM_EC.toLowerCase(),
+            NamedParameterSpec.ED25519.getName().toLowerCase(),
+            "eddsa");
 
     public final static class NONE extends AndroidKeyStoreECDSASignatureSpi {
         public NONE() {
@@ -114,6 +121,18 @@ abstract class AndroidKeyStoreECDSASignatureSpi extends AndroidKeyStoreSignature
         }
     }
 
+    public static final class Ed25519 extends AndroidKeyStoreECDSASignatureSpi {
+        public Ed25519() {
+            // Ed25519 uses an internal digest system.
+            super(KeymasterDefs.KM_DIGEST_NONE);
+        }
+
+        @Override
+        protected String getAlgorithm() {
+            return NamedParameterSpec.ED25519.getName();
+        }
+    }
+
     public final static class SHA1 extends AndroidKeyStoreECDSASignatureSpi {
         public SHA1() {
             super(KeymasterDefs.KM_DIGEST_SHA1);
@@ -174,9 +193,10 @@ abstract class AndroidKeyStoreECDSASignatureSpi extends AndroidKeyStoreSignature
 
     @Override
     protected final void initKey(AndroidKeyStoreKey key) throws InvalidKeyException {
-        if (!KeyProperties.KEY_ALGORITHM_EC.equalsIgnoreCase(key.getAlgorithm())) {
+        if (!ACCEPTED_SIGNING_SCHEMES.contains(key.getAlgorithm().toLowerCase())) {
             throw new InvalidKeyException("Unsupported key algorithm: " + key.getAlgorithm()
-                    + ". Only" + KeyProperties.KEY_ALGORITHM_EC + " supported");
+                    + ". Only" + Arrays.toString(ACCEPTED_SIGNING_SCHEMES.stream().toArray())
+                    + " supported");
         }
 
         long keySizeBits = -1;