/*

 * Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package com.oracle.security.ucrypto;

import java.io.ByteArrayOutputStream;

import java.nio.ByteBuffer;

import java.util.Set;

import java.util.Arrays;

import java.security.*;

import java.security.spec.*;

import javax.crypto.*;

import javax.crypto.spec.SecretKeySpec;

import javax.crypto.spec.GCMParameterSpec;

/**

 * Cipher wrapper class utilizing ucrypto APIs. This class currently supports

 * - AES/GCM/NoPADDING

 *

 * @since 1.9

 */

class NativeGCMCipher extends NativeCipher {

    public static final class AesGcmNoPadding extends NativeGCMCipher {

        public AesGcmNoPadding() throws NoSuchAlgorithmException {

            super(-1);

        }

        public AesGcmNoPadding(int keySize) throws NoSuchAlgorithmException {

            super(keySize);

        }

    }

    private static final int DEFAULT_TAG_LEN = 128; // same as SunJCE provider

    // buffer for storing AAD data; if null, meaning buffer content has been

    // supplied to native context

    private ByteArrayOutputStream aadBuffer = new ByteArrayOutputStream();

    // buffer for storing input in decryption, not used for encryption

    private ByteArrayOutputStream ibuffer = null;

    private int tagLen = DEFAULT_TAG_LEN;

    /*

     * variables used for performing the GCM (key+iv) uniqueness check.

     * To use GCM mode safely, the cipher object must be re-initialized

     * with a different combination of key + iv values for each

     * ENCRYPTION operation. However, checking all past key + iv values

     * isn't feasible. Thus, we only do a per-instance check of the

     * key + iv values used in previous encryption.

     * For decryption operations, no checking is necessary.

     */

    private boolean requireReinit = false;

    private byte[] lastEncKey = null;

    private byte[] lastEncIv = null;

    NativeGCMCipher(int fixedKeySize) throws NoSuchAlgorithmException {

        super(UcryptoMech.CRYPTO_AES_GCM, fixedKeySize);

    }

    @Override

    protected void ensureInitialized() {

        if (!initialized) {

            if (aadBuffer != null && aadBuffer.size() > 0) {

                init(encrypt, keyValue, iv, tagLen, aadBuffer.toByteArray());

                aadBuffer = null;

            } else {

                init(encrypt, keyValue, iv, tagLen, null);

            }

            if (!initialized) {

                throw new UcryptoException("Cannot initialize Cipher");

            }

        }

    }

    @Override

    protected int getOutputSizeByOperation(int inLen, boolean isDoFinal) {

        if (inLen < 0) return 0;

        if (!isDoFinal && (inLen == 0)) {

            return 0;

        }

        int result = inLen + bytesBuffered;

        if (encrypt) {

            if (isDoFinal) {

                result += tagLen/8;

            }

        } else {

            if (ibuffer != null) {

                result += ibuffer.size();

            }

            result -= tagLen/8;

        }

        if (result < 0) {

            result = 0;

        }

        return result;

    }

    @Override

    protected void reset(boolean doCancel) {

        super.reset(doCancel);

        if (aadBuffer == null) {

            aadBuffer = new ByteArrayOutputStream();

        } else {

            aadBuffer.reset();

        }

        if (ibuffer != null) {

            ibuffer.reset();

        }

        if (!encrypt) requireReinit = false;

    }

    // actual init() implementation - caller should clone key and iv if needed

    protected void init(boolean encrypt, byte[] keyVal, byte[] ivVal, int tLen, byte[] aad) {

        reset(true);

        this.encrypt = encrypt;

        this.keyValue = keyVal;

        this.iv = ivVal;

        long pCtxtVal = NativeCipher.nativeInit(mech.value(), encrypt, keyValue, iv,

            tLen, aad);

        initialized = (pCtxtVal != 0L);

        if (initialized) {

            pCtxt = new CipherContextRef(this, pCtxtVal, encrypt);

        } else {

            throw new UcryptoException("Cannot initialize Cipher");

        }

    }

    // see JCE spec

    @Override

    protected synchronized AlgorithmParameters engineGetParameters() {

        AlgorithmParameters params = null;

        try {

            if (iv != null) {

                GCMParameterSpec gcmSpec = new GCMParameterSpec(tagLen, iv.clone());

                params = AlgorithmParameters.getInstance("GCM");

                params.init(gcmSpec);

            }

        } catch (GeneralSecurityException e) {

            // NoSuchAlgorithmException, NoSuchProviderException

            // InvalidParameterSpecException

            throw new UcryptoException("Could not encode parameters", e);

        }

        return params;

    }

    // see JCE spec

    @Override

    protected synchronized void engineInit(int opmode, Key key,

            AlgorithmParameterSpec params, SecureRandom random)

            throws InvalidKeyException, InvalidAlgorithmParameterException {

        checkKey(key);

        if (opmode != Cipher.ENCRYPT_MODE &&

            opmode != Cipher.DECRYPT_MODE &&

            opmode != Cipher.WRAP_MODE &&

            opmode != Cipher.UNWRAP_MODE) {

            throw new InvalidAlgorithmParameterException

                ("Unsupported mode: " + opmode);

        }

        boolean doEncrypt = (opmode == Cipher.ENCRYPT_MODE || opmode == Cipher.WRAP_MODE);

        byte[] keyBytes = key.getEncoded().clone();

        byte[] ivBytes = null;

        if (params != null) {

            if (!(params instanceof GCMParameterSpec)) {

                throw new InvalidAlgorithmParameterException("GCMParameterSpec required");

            } else {

                tagLen = ((GCMParameterSpec) params).getTLen();

                ivBytes = ((GCMParameterSpec) params).getIV();

            }

        } else {

            if (doEncrypt) {

                tagLen = DEFAULT_TAG_LEN;

                // generate IV if none supplied for encryption

                ivBytes = new byte[blockSize];

                new SecureRandom().nextBytes(ivBytes);

            } else {

                throw new InvalidAlgorithmParameterException("Parameters required for decryption");

            }

        }

        if (doEncrypt) {

            requireReinit = Arrays.equals(ivBytes, lastEncIv) &&

            if (requireReinit) {

                throw new InvalidAlgorithmParameterException

                    ("Cannot reuse iv for GCM encryption");

            }

            lastEncIv = ivBytes;

            lastEncKey = keyBytes;

        } else {

            requireReinit = false;

            ibuffer = new ByteArrayOutputStream();

        }

        init(doEncrypt, keyBytes, ivBytes, tagLen, null);

    }

    // see JCE spec

    @Override

    protected synchronized void engineInit(int opmode, Key key, AlgorithmParameters params,

            SecureRandom random)

            throws InvalidKeyException, InvalidAlgorithmParameterException {

        AlgorithmParameterSpec spec = null;

        if (params != null) {

            try {

                // mech must be UcryptoMech.CRYPTO_AES_GCM

                spec = params.getParameterSpec(GCMParameterSpec.class);

            } catch (InvalidParameterSpecException iaps) {

                throw new InvalidAlgorithmParameterException(iaps);

            }

        }

        engineInit(opmode, key, spec, random);

    }

    // see JCE spec

    @Override

    protected synchronized byte[] engineUpdate(byte[] in, int inOfs, int inLen) {

        if (aadBuffer != null && aadBuffer.size() > 0) {

            // init again with AAD data

            init(encrypt, keyValue, iv, tagLen, aadBuffer.toByteArray());

            aadBuffer = null;

        }

        if (requireReinit) {

            throw new IllegalStateException

                ("Must use either different key or iv for GCM encryption");

        }

        if (inLen > 0) {

            if (!encrypt) {

                ibuffer.write(in, inOfs, inLen);

                return null;

            }

            return super.engineUpdate(in, inOfs, inLen);

        } else return null;

    }

    // see JCE spec

    @Override

    protected synchronized int engineUpdate(byte[] in, int inOfs, int inLen, byte[] out,

            int outOfs) throws ShortBufferException {

        int len = getOutputSizeByOperation(inLen, false);

        if (out.length - outOfs < len) {

            throw new ShortBufferException("Output buffer must be "

                                           + "(at least) " + len

                                           + " bytes long");

        }

        if (aadBuffer != null && aadBuffer.size() > 0) {

            // init again with AAD data

            init(encrypt, keyValue, iv, tagLen, aadBuffer.toByteArray());

            aadBuffer = null;

        }

        if (requireReinit) {

            throw new IllegalStateException

                ("Must use either different key or iv for GCM encryption");

        }

        if (inLen > 0) {

            if (!encrypt) {

                ibuffer.write(in, inOfs, inLen);

                return 0;

            } else {

                return super.engineUpdate(in, inOfs, inLen, out, outOfs);

            }

        }

        return 0;

    }

    // see JCE spec

    @Override

    protected synchronized void engineUpdateAAD(byte[] src, int srcOfs, int srcLen)

            throws IllegalStateException {

        if ((src == null) || (srcOfs < 0) || (srcOfs + srcLen > src.length)) {

            throw new IllegalArgumentException("Invalid AAD");

        }

        if (keyValue == null) {

            throw new IllegalStateException("Need to initialize Cipher first");

        }

        if (requireReinit) {

            throw new IllegalStateException

                ("Must use either different key or iv for GCM encryption");

        }

        if (aadBuffer != null) {

            aadBuffer.write(src, srcOfs, srcLen);

        } else {

            // update has already been called

            throw new IllegalStateException

                ("Update has been called; no more AAD data");

        }

    }

    // see JCE spec

    @Override

    protected void engineUpdateAAD(ByteBuffer src)

            throws IllegalStateException {

        if (src == null) {

            throw new IllegalArgumentException("Invalid AAD");

        }

        if (keyValue == null) {

            throw new IllegalStateException("Need to initialize Cipher first");

        }

        if (requireReinit) {

            throw new IllegalStateException

                ("Must use either different key or iv for GCM encryption");

        }

        if (aadBuffer != null) {

            if (src.hasRemaining()) {

                byte[] srcBytes = new byte[src.remaining()];

                src.get(srcBytes);

                aadBuffer.write(srcBytes, 0, srcBytes.length);

            }

        } else {

            // update has already been called

            throw new IllegalStateException

                ("Update has been called; no more AAD data");

        }

    }

    // see JCE spec

    @Override

    protected synchronized byte[] engineDoFinal(byte[] in, int inOfs, int inLen)

            throws IllegalBlockSizeException, BadPaddingException {

        byte[] out = new byte[getOutputSizeByOperation(inLen, true)];

        try {

            // delegate to the other engineDoFinal(...) method

            int k = engineDoFinal(in, inOfs, inLen, out, 0);

            if (out.length != k) {

                out = Arrays.copyOf(out, k);

            }

            return out;

        } catch (ShortBufferException e) {

            throw new UcryptoException("Internal Error", e);

        }

    }

    // see JCE spec

    @Override

    protected synchronized int engineDoFinal(byte[] in, int inOfs, int inLen,

                                             byte[] out, int outOfs)

        throws ShortBufferException, IllegalBlockSizeException,

               BadPaddingException {

        int len = getOutputSizeByOperation(inLen, true);

        if (out.length - outOfs < len) {

            throw new ShortBufferException("Output buffer must be "

                                           + "(at least) " + len

                                           + " bytes long");

        }

        if (aadBuffer != null && aadBuffer.size() > 0) {

            // init again with AAD data

            init(encrypt, keyValue, iv, tagLen, aadBuffer.toByteArray());

            aadBuffer = null;

        }

        if (requireReinit) {

            throw new IllegalStateException

                ("Must use either different key or iv for GCM encryption");

        }

        if (!encrypt) {

            if (inLen > 0) {

                ibuffer.write(in, inOfs, inLen);

            }

            inLen = ibuffer.size();

            if (inLen < tagLen/8) {

                // Otherwise, Solaris lib will error out w/ CRYPTO_BUFFER_TOO_SMALL

                // when ucrypto_decrypt_final() is called

                throw new AEADBadTagException("Input too short - need tag");

            }

            // refresh 'in' to all buffered-up bytes

            in = ibuffer.toByteArray();

            inOfs = 0;

            ibuffer.reset();

        }

        try {

            return super.engineDoFinal(in, inOfs, inLen, out, outOfs);

        } catch (UcryptoException ue) {

            if (ue.getMessage().equals("CRYPTO_INVALID_MAC")) {

                throw new AEADBadTagException("Tag does not match");

            } else {

                // pass it up

                throw ue;

            }

        } finally {

            requireReinit = encrypt;

        }

    }

}