1 files changed, 209 insertions, 0 deletions
diff --git a/src/java/com/android/internal/net/ipsec/ike/crypto/IkeCombinedModeCipher.java b/src/java/com/android/internal/net/ipsec/ike/crypto/IkeCombinedModeCipher.java
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+++ b/src/java/com/android/internal/net/ipsec/ike/crypto/IkeCombinedModeCipher.java
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+/*
+ * 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.internal.net.ipsec.ike.crypto;
+
+import android.net.IpSecAlgorithm;
+import android.net.ipsec.ike.SaProposal;
+
+import java.nio.ByteBuffer;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.Provider;
+import java.security.spec.AlgorithmParameterSpec;
+import java.util.Arrays;
+
+import javax.crypto.AEADBadTagException;
+import javax.crypto.BadPaddingException;
+import javax.crypto.Cipher;
+import javax.crypto.IllegalBlockSizeException;
+import javax.crypto.ShortBufferException;
+import javax.crypto.spec.GCMParameterSpec;
+import javax.crypto.spec.SecretKeySpec;
+
+/**
+ * IkeCipher represents a negotiated combined-mode cipher(AEAD) encryption algorithm.
+ *
+ * <p>Checksum mentioned in this class is also known as authentication tag or Integrity Checksum
+ * Vector(ICV)
+ *
+ * @see <a href="https://tools.ietf.org/html/rfc7296#section-3.3.2">RFC 7296, Internet Key Exchange
+ *     Protocol Version 2 (IKEv2)</a>
+ * @see <a href="https://tools.ietf.org/html/rfc5282">RFC 5282,Using Authenticated Encryption
+ *     Algorithms with the Encrypted Payload of the Internet Key Exchange version 2 (IKEv2)
+ *     Protocol</a>
+ */
+public final class IkeCombinedModeCipher extends IkeCipher {
+    private static final int SALT_LEN_GCM = 4;
+
+    private final int mChecksumLen;
+    private final int mSaltLen;
+
+    /** Package private */
+    IkeCombinedModeCipher(
+            int algorithmId, int keyLength, int ivLength, String algorithmName, Provider provider) {
+        super(algorithmId, keyLength, ivLength, algorithmName, true /*isAead*/, provider);
+        switch (algorithmId) {
+            case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_8:
+                mSaltLen = SALT_LEN_GCM;
+                mChecksumLen = 8;
+                break;
+            case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_12:
+                mSaltLen = SALT_LEN_GCM;
+                mChecksumLen = 12;
+                break;
+            case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_16:
+                mSaltLen = SALT_LEN_GCM;
+                mChecksumLen = 16;
+                break;
+            default:
+                throw new IllegalArgumentException(
+                        "Unrecognized Encryption Algorithm ID: " + algorithmId);
+        }
+    }
+
+    private byte[] doCipherAction(
+            byte[] data, byte[] additionalAuthData, byte[] keyBytes, byte[] ivBytes, int opmode)
+            throws AEADBadTagException {
+        try {
+            // Provided key consists of encryption/decryption key plus 4-byte salt. Salt is used
+            // with IV to build the nonce.
+            ByteBuffer secretKeyAndSaltBuffer = ByteBuffer.wrap(keyBytes);
+            byte[] secretKeyBytes = new byte[keyBytes.length - mSaltLen];
+            byte[] salt = new byte[mSaltLen];
+            secretKeyAndSaltBuffer.get(secretKeyBytes);
+            secretKeyAndSaltBuffer.get(salt);
+
+            SecretKeySpec key = new SecretKeySpec(secretKeyBytes, getAlgorithmName());
+
+            ByteBuffer nonceBuffer = ByteBuffer.allocate(mSaltLen + ivBytes.length);
+            nonceBuffer.put(salt);
+            nonceBuffer.put(ivBytes);
+
+            mCipher.init(opmode, key, getParamSpec(nonceBuffer.array()));
+            mCipher.updateAAD(additionalAuthData);
+
+            ByteBuffer inputBuffer = ByteBuffer.wrap(data);
+
+            int outputLen = data.length;
+            if (opmode == Cipher.ENCRYPT_MODE) outputLen += mChecksumLen;
+            ByteBuffer outputBuffer = ByteBuffer.allocate(outputLen);
+
+            mCipher.doFinal(inputBuffer, outputBuffer);
+            return outputBuffer.array();
+        } catch (AEADBadTagException e) {
+            // Checksum failed in decryption
+            throw (AEADBadTagException) e;
+        } catch (InvalidKeyException
+                | InvalidAlgorithmParameterException
+                | IllegalBlockSizeException
+                | BadPaddingException
+                | ShortBufferException e) {
+            String errorMessage =
+                    Cipher.ENCRYPT_MODE == opmode
+                            ? "Failed to encrypt data: "
+                            : "Failed to decrypt data: ";
+            throw new IllegalArgumentException(errorMessage, e);
+        }
+    }
+
+    private AlgorithmParameterSpec getParamSpec(byte[] nonce) {
+        switch (getAlgorithmId()) {
+            case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_8:
+                // Fall through
+            case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_12:
+                // Fall through
+            case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_16:
+                return new GCMParameterSpec(mChecksumLen * 8, nonce);
+            default:
+                throw new IllegalArgumentException(
+                        "Unrecognized Encryption Algorithm ID: " + getAlgorithmId());
+        }
+    }
+
+    /**
+     * Encrypt padded data and calculate checksum for it.
+     *
+     * @param paddedData the padded data to encrypt.
+     * @param additionalAuthData additional data to authenticate (also known as associated data).
+     * @param keyBytes the encryption key.
+     * @param ivBytes the initialization vector (IV).
+     * @return the encrypted and padded data with checksum.
+     */
+    public byte[] encrypt(
+            byte[] paddedData, byte[] additionalAuthData, byte[] keyBytes, byte[] ivBytes) {
+        try {
+            return doCipherAction(
+                    paddedData, additionalAuthData, keyBytes, ivBytes, Cipher.ENCRYPT_MODE);
+        } catch (AEADBadTagException e) {
+            throw new IllegalArgumentException("Failed to encrypt data: ", e);
+        }
+    }
+
+    /**
+     * Authenticate and decrypt the padded data with checksum.
+     *
+     * @param paddedDataWithChecksum the padded data with checksum.
+     * @param additionalAuthData additional data to authenticate (also known as associated data).
+     * @param keyBytes the decryption key.
+     * @param ivBytes the initialization vector (IV).
+     * @return the decrypted and padded data
+     * @throws AEADBadTagException if authentication or decryption fails
+     */
+    public byte[] decrypt(
+            byte[] paddedDataWithChecksum,
+            byte[] additionalAuthData,
+            byte[] keyBytes,
+            byte[] ivBytes)
+            throws AEADBadTagException {
+
+        byte[] decryptPaddedDataAndAuthTag =
+                doCipherAction(
+                        paddedDataWithChecksum,
+                        additionalAuthData,
+                        keyBytes,
+                        ivBytes,
+                        Cipher.DECRYPT_MODE);
+
+        int decryptPaddedDataLen = decryptPaddedDataAndAuthTag.length - mChecksumLen;
+        return Arrays.copyOf(decryptPaddedDataAndAuthTag, decryptPaddedDataLen);
+    }
+
+    /**
+     * Gets key length of this algorithm (in bytes).
+     *
+     * @return the key length (in bytes).
+     */
+    @Override
+    public int getKeyLength() {
+        return super.getKeyLength() + mSaltLen;
+    }
+
+    /**
+     * Returns length of checksum.
+     *
+     * @return the length of checksum in bytes.
+     */
+    public int getChecksumLen() {
+        return mChecksumLen;
+    }
+
+    @Override
+    public IpSecAlgorithm buildIpSecAlgorithmWithKey(byte[] key) {
+        validateKeyLenOrThrow(key);
+        return new IpSecAlgorithm(IpSecAlgorithm.AUTH_CRYPT_AES_GCM, key, mChecksumLen * 8);
+    }
+}