Build outbound IkeAuthPskPayload

This commit:
- Create constructor for building outbound IkeAuthPskPayload
- Support calculating PSK signature
- Support encoding IkeAuthPskPayload

Bug: 122686851
Test: FrameworksIkeTests IkeAuthPskPayload
Change-Id: I28c8c6c3c03a339761547303d4caacfd2db31729

5 files changed, 178 insertions, 16 deletions

diff --git a/src/java/com/android/ike/ikev2/message/IkeAuthDigitalSignPayload.java b/src/java/com/android/ike/ikev2/message/IkeAuthDigitalSignPayload.java
index 12fb5f66..5b5a3f0b 100644
--- a/src/java/com/android/ike/ikev2/message/IkeAuthDigitalSignPayload.java
+++ b/src/java/com/android/ike/ikev2/message/IkeAuthDigitalSignPayload.java
@@ -138,14 +138,14 @@ public class IkeAuthDigitalSignPayload extends IkeAuthPayload {
     // TODO: Add methods for generating and validating signature.
 
     @Override
-    protected void encodeToByteBuffer(@PayloadType int nextPayload, ByteBuffer byteBuffer) {
+    protected void encodeAuthDataToByteBuffer(ByteBuffer byteBuffer) {
         // TODO: Implement it.
         throw new UnsupportedOperationException(
                 "It is not supported to encode a " + getTypeString());
     }
 
     @Override
-    protected int getPayloadLength() {
+    protected int getAuthDataLength() {
         // TODO: Implement it.
         throw new UnsupportedOperationException(
                 "It is not supported to get payload length of " + getTypeString());
diff --git a/src/java/com/android/ike/ikev2/message/IkeAuthPayload.java b/src/java/com/android/ike/ikev2/message/IkeAuthPayload.java
index beb2bdc6..502af36a 100644
--- a/src/java/com/android/ike/ikev2/message/IkeAuthPayload.java
+++ b/src/java/com/android/ike/ikev2/message/IkeAuthPayload.java
@@ -61,7 +61,7 @@ public abstract class IkeAuthPayload extends IkePayload {
 
     @AuthMethod public final int authMethod;
 
-    protected IkeAuthPayload(boolean critical, int authMethod) throws IkeException {
+    protected IkeAuthPayload(boolean critical, int authMethod) {
         super(PAYLOAD_TYPE_AUTH, critical);
         this.authMethod = authMethod;
     }
@@ -131,7 +131,23 @@ public abstract class IkeAuthPayload extends IkePayload {
     }
 
     @Override
+    protected void encodeToByteBuffer(@PayloadType int nextPayload, ByteBuffer byteBuffer) {
+        encodePayloadHeaderToByteBuffer(nextPayload, getPayloadLength(), byteBuffer);
+        byteBuffer.put((byte) authMethod).put(new byte[AUTH_RESERVED_FIELD_LEN]);
+        encodeAuthDataToByteBuffer(byteBuffer);
+    }
+
+    @Override
+    protected int getPayloadLength() {
+        return GENERIC_HEADER_LENGTH + AUTH_HEADER_LEN + getAuthDataLength();
+    }
+
+    @Override
     public String getTypeString() {
         return "Authentication Payload";
     }
+
+    protected abstract void encodeAuthDataToByteBuffer(ByteBuffer byteBuffer);
+
+    protected abstract int getAuthDataLength();
 }
diff --git a/src/java/com/android/ike/ikev2/message/IkeAuthPskPayload.java b/src/java/com/android/ike/ikev2/message/IkeAuthPskPayload.java
index 63f45dd5..213e24a3 100644
--- a/src/java/com/android/ike/ikev2/message/IkeAuthPskPayload.java
+++ b/src/java/com/android/ike/ikev2/message/IkeAuthPskPayload.java
@@ -16,9 +16,10 @@
 
 package com.android.ike.ikev2.message;
 
-import com.android.ike.ikev2.exceptions.IkeException;
-
 import java.nio.ByteBuffer;
+import java.security.InvalidKeyException;
+
+import javax.crypto.Mac;
 
 /**
  * IkeAuthPskPayload represents an Authentication Payload using Pre-Shared Key to do authentication.
@@ -27,25 +28,79 @@ import java.nio.ByteBuffer;
  *     Protocol Version 2 (IKEv2).
  */
 public final class IkeAuthPskPayload extends IkeAuthPayload {
+    // Hex of ASCII characters "Key Pad for IKEv2" for calculating PSK signature.
+    private static final byte[] IKE_KEY_PAD_STRING_ASCII_HEX_BYTES = {
+        (byte) 0x4b, (byte) 0x65, (byte) 0x79, (byte) 0x20,
+        (byte) 0x50, (byte) 0x61, (byte) 0x64, (byte) 0x20,
+        (byte) 0x66, (byte) 0x6f, (byte) 0x72, (byte) 0x20,
+        (byte) 0x49, (byte) 0x4b, (byte) 0x45, (byte) 0x76,
+        (byte) 0x32
+    };
+
     public final byte[] signature;
 
-    protected IkeAuthPskPayload(boolean critical, byte[] authData) throws IkeException {
+    /**
+     * Construct IkeAuthPskPayload for received IKE packet in the context of {@link
+     * IkePayloadFactory}.
+     */
+    protected IkeAuthPskPayload(boolean critical, byte[] authData) {
         super(critical, IkeAuthPayload.AUTH_METHOD_PRE_SHARED_KEY);
         signature = authData;
     }
 
+    /**
+     * Construct IkeAuthPskPayload for an outbound IKE packet.
+     *
+     * <p>Since IKE library is always a client, outbound IkeAuthPskPayload always signs IKE
+     * initiator's SignedOctets, which is concatenation of the IKE_INIT request message, the Nonce
+     * of IKE responder and the signed ID-Initiator payload body.
+     *
+     * @param psk locally stored pre-shared key
+     * @param ikeInitBytes IKE_INIT request for calculating IKE initiator's SignedOctets.
+     * @param nonce nonce of IKE responder for calculating IKE initiator's SignedOctets.
+     * @param idPayloadBodyBytes ID-Initiator payload body for calculating IKE initiator's
+     *     SignedOctets.
+     * @param prfMac locally store PRF
+     * @param prfKeyBytes locally store PRF keys
+     */
+    public IkeAuthPskPayload(
+            byte[] psk,
+            byte[] ikeInitBytes,
+            byte[] nonce,
+            byte[] idPayloadBodyBytes,
+            Mac prfMac,
+            byte[] prfKeyBytes) {
+        super(false, IkeAuthPayload.AUTH_METHOD_PRE_SHARED_KEY);
+        signature =
+                calculatePskSignature(
+                        psk, ikeInitBytes, nonce, idPayloadBodyBytes, prfMac, prfKeyBytes);
+    }
+
+    private static byte[] calculatePskSignature(
+            byte[] psk,
+            byte[] ikeInitBytes,
+            byte[] nonce,
+            byte[] idPayloadBodyBytes,
+            Mac prfMac,
+            byte[] prfKeyBytes) {
+        try {
+            byte[] signingKeyBytes = signWithPrf(prfMac, psk, IKE_KEY_PAD_STRING_ASCII_HEX_BYTES);
+            byte[] dataToSignBytes =
+                    getSignedOctets(ikeInitBytes, nonce, idPayloadBodyBytes, prfMac, prfKeyBytes);
+            return signWithPrf(prfMac, signingKeyBytes, dataToSignBytes);
+        } catch (InvalidKeyException e) {
+            throw new IllegalArgumentException("Locally stored PRF key is invalid: ", e);
+        }
+    }
+
     @Override
-    protected void encodeToByteBuffer(@PayloadType int nextPayload, ByteBuffer byteBuffer) {
-        // TODO: Implement it.
-        throw new UnsupportedOperationException(
-                "It is not supported to encode a " + getTypeString());
+    protected void encodeAuthDataToByteBuffer(ByteBuffer byteBuffer) {
+        byteBuffer.put(signature);
     }
 
     @Override
-    protected int getPayloadLength() {
-        // TODO: Implement it.
-        throw new UnsupportedOperationException(
-                "It is not supported to get payload length of " + getTypeString());
+    protected int getAuthDataLength() {
+        return signature.length;
     }
 
     @Override
diff --git a/tests/iketests/src/java/com/android/ike/ikev2/message/IkeAuthPayloadTest.java b/tests/iketests/src/java/com/android/ike/ikev2/message/IkeAuthPayloadTest.java
index a67f04c4..7c630b76 100644
--- a/tests/iketests/src/java/com/android/ike/ikev2/message/IkeAuthPayloadTest.java
+++ b/tests/iketests/src/java/com/android/ike/ikev2/message/IkeAuthPayloadTest.java
@@ -28,7 +28,7 @@ import javax.crypto.Mac;
 public final class IkeAuthPayloadTest {
     private static final String PSK_AUTH_PAYLOAD_HEX_STRING =
             "02000000df7c038aefaaa32d3f44b228b52a332744dfb2c1";
-    private static final String PSK_AUTH_PAYLOAD_SIGNATRUE_HEX_STRING =
+    private static final String PSK_AUTH_PAYLOAD_SIGNATURE_HEX_STRING =
             "df7c038aefaaa32d3f44b228b52a332744dfb2c1";
     private static final String PSK_ID_PAYLOAD_HEX_STRING = "010000000a50500d";
     private static final String PSK_SKP_HEX_STRING = "094787780EE466E2CB049FA327B43908BC57E485";
@@ -89,7 +89,7 @@ public final class IkeAuthPayloadTest {
         assertTrue(payload instanceof IkeAuthPskPayload);
 
         byte[] expectedSignature =
-                TestUtils.hexStringToByteArray(PSK_AUTH_PAYLOAD_SIGNATRUE_HEX_STRING);
+                TestUtils.hexStringToByteArray(PSK_AUTH_PAYLOAD_SIGNATURE_HEX_STRING);
         assertArrayEquals(expectedSignature, ((IkeAuthPskPayload) payload).signature);
     }
 
diff --git a/tests/iketests/src/java/com/android/ike/ikev2/message/IkeAuthPskPayloadTest.java b/tests/iketests/src/java/com/android/ike/ikev2/message/IkeAuthPskPayloadTest.java
new file mode 100644
index 00000000..398e9626
--- /dev/null
+++ b/tests/iketests/src/java/com/android/ike/ikev2/message/IkeAuthPskPayloadTest.java
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.ike.ikev2.message;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import java.nio.ByteBuffer;
+
+import javax.crypto.Mac;
+
+
+public final class IkeAuthPskPayloadTest {
+    private static final String PSK_AUTH_PAYLOAD_HEX_STRING =
+            "2100001c02000000df7c038aefaaa32d3f44b228b52a332744dfb2c1";
+    private static final String PSK_AUTH_PAYLOAD_SIGNATURE_HEX_STRING =
+            "df7c038aefaaa32d3f44b228b52a332744dfb2c1";
+
+    private static final String PSK_IKE_INIT_REQUEST_HEX_STRING =
+            "5f54bf6d8b48e6e1000000000000000021202208"
+                    + "0000000000000150220000300000002c01010004"
+                    + "0300000c0100000c800e00800300000803000002"
+                    + "0300000804000002000000080200000228000088"
+                    + "00020000b4a2faf4bb54878ae21d638512ece55d"
+                    + "9236fc5046ab6cef82220f421f3ce6361faf3656"
+                    + "4ecb6d28798a94aad7b2b4b603ddeaaa5630adb9"
+                    + "ece8ac37534036040610ebdd92f46bef84f0be7d"
+                    + "b860351843858f8acf87056e272377f70c9f2d81"
+                    + "e29c7b0ce4f291a3a72476bb0b278fd4b7b0a4c2"
+                    + "6bbeb08214c707137607958729000024c39b7f36"
+                    + "8f4681b89fa9b7be6465abd7c5f68b6ed5d3b4c7"
+                    + "2cb4240eb5c464122900001c00004004e54f73b7"
+                    + "d83f6beb881eab2051d8663f421d10b02b00001c"
+                    + "00004005d915368ca036004cb578ae3e3fb26850"
+                    + "9aeab19000000020699369228741c6d4ca094c93"
+                    + "e242c9de19e7b7c60000000500000500";
+    private static final String PSK_NONCE_RESP_HEX_STRING =
+            "9756112ca539f5c25abacc7ee92b73091942a9c06950f98848f1af1694c4ddff";
+    private static final String PSK_ID_INITIATOR_PAYLOAD_HEX_STRING = "010000000a50500d";
+
+    private static final String PSK_HEX_STRING = "6A756E69706572313233";
+    private static final String PSK_SKP_HEX_STRING = "094787780EE466E2CB049FA327B43908BC57E485";
+
+    private static final String PRF_HMAC_SHA1_ALGO_NAME = "HmacSHA1";
+
+    @Test
+    public void testBuildOutboundIkeAuthPskPayload() throws Exception {
+        byte[] psk = TestUtils.hexStringToByteArray(PSK_HEX_STRING);
+        byte[] ikeInitBytes = TestUtils.hexStringToByteArray(PSK_IKE_INIT_REQUEST_HEX_STRING);
+        byte[] nonce = TestUtils.hexStringToByteArray(PSK_NONCE_RESP_HEX_STRING);
+        byte[] idPayloadBodyBytes =
+                TestUtils.hexStringToByteArray(PSK_ID_INITIATOR_PAYLOAD_HEX_STRING);
+        byte[] prfKeyBytes = TestUtils.hexStringToByteArray(PSK_SKP_HEX_STRING);
+        Mac prfMac = Mac.getInstance(PRF_HMAC_SHA1_ALGO_NAME, IkeMessage.getSecurityProvider());
+
+        IkeAuthPskPayload payload =
+                new IkeAuthPskPayload(
+                        psk, ikeInitBytes, nonce, idPayloadBodyBytes, prfMac, prfKeyBytes);
+
+        assertEquals(IkeAuthPayload.AUTH_METHOD_PRE_SHARED_KEY, payload.authMethod);
+        byte[] expectedSignature =
+                TestUtils.hexStringToByteArray(PSK_AUTH_PAYLOAD_SIGNATURE_HEX_STRING);
+        assertArrayEquals(expectedSignature, payload.signature);
+
+        // Verify payload length
+        int payloadLength = payload.getPayloadLength();
+        byte[] expectedPayload = TestUtils.hexStringToByteArray(PSK_AUTH_PAYLOAD_HEX_STRING);
+        assertEquals(expectedPayload.length, payloadLength);
+
+        // Verify encoding
+        ByteBuffer byteBuffer = ByteBuffer.allocate(payloadLength);
+        payload.encodeToByteBuffer(IkePayload.PAYLOAD_TYPE_SA, byteBuffer);
+        assertArrayEquals(expectedPayload, byteBuffer.array());
+    }
+}