Keystore 2.0: Add keystore engine grant string convenience functions.

This patch adds function for and end decoding grant identfiers as
understood by the keystore boringssl engine.

Test: N/A
Change-Id: I619d8f460163e6270e41da81ca549efb71138113

1 files changed, 45 insertions, 0 deletions

diff --git a/keystore/java/android/security/KeyStore2.java b/keystore/java/android/security/KeyStore2.java
index 476e4d7b7b18..6ac3821d0f9c 100644
--- a/keystore/java/android/security/KeyStore2.java
+++ b/keystore/java/android/security/KeyStore2.java
@@ -24,6 +24,7 @@ import android.os.RemoteException;
 import android.os.ServiceManager;
 import android.os.ServiceSpecificException;
 import android.security.keymaster.KeymasterDefs;
+import android.system.keystore2.Domain;
 import android.system.keystore2.IKeystoreService;
 import android.system.keystore2.KeyDescriptor;
 import android.system.keystore2.KeyEntryResponse;
@@ -157,6 +158,50 @@ public class KeyStore2 {
     }
 
     /**
+     * Grant string prefix as used by the keystore boringssl engine. Must be kept in sync
+     * with system/security/keystore-engine. Note: The prefix here includes the 0x which
+     * std::stringstream used in keystore-engine needs to identify the number as hex represented.
+     * Here we include it in the prefix, because Long#parseUnsignedLong does not understand it
+     * and gets the radix as explicit argument.
+     * @hide
+     */
+    private static final String KEYSTORE_ENGINE_GRANT_ALIAS_PREFIX =
+            "ks2_keystore-engine_grant_id:0x";
+
+    /**
+     * This function turns a grant identifier into a specific string that is understood by the
+     * keystore-engine in system/security/keystore-engine. Is only used by VPN and WI-FI components
+     * to allow certain system components like racoon or vendor components like WPA supplicant
+     * to use keystore keys with boring ssl.
+     *
+     * @param grantId the grant id as returned by {@link #grant} in the {@code nspace} filed of
+     *                the resulting {@code KeyDescriptor}.
+     * @return The grant descriptor string.
+     * @hide
+     */
+    public static String makeKeystoreEngineGrantString(long grantId) {
+        return String.format("%s%016X", KEYSTORE_ENGINE_GRANT_ALIAS_PREFIX, grantId);
+    }
+
+    /**
+     * Convenience function to turn a keystore engine grant string as returned by
+     * {@link #makeKeystoreEngineGrantString(long)} back into a grant KeyDescriptor.
+     *
+     * @param grantString As string returned by {@link #makeKeystoreEngineGrantString(long)}
+     * @return The grant key descriptor.
+     * @hide
+     */
+    public static KeyDescriptor keystoreEngineGrantString2KeyDescriptor(String grantString) {
+        KeyDescriptor key = new KeyDescriptor();
+        key.domain = Domain.GRANT;
+        key.nspace = Long.parseUnsignedLong(
+                grantString.substring(KEYSTORE_ENGINE_GRANT_ALIAS_PREFIX.length()), 16);
+        key.alias = null;
+        key.blob = null;
+        return key;
+    }
+
+    /**
      * Create a grant that allows the grantee identified by {@code granteeUid} to use
      * the key specified by {@code descriptor} withint the restrictions given by
      * {@code accessVectore}.