/**
 * @file llblowfishcipher.cpp
 * @brief Wrapper around OpenSSL Blowfish encryption algorithm.
 *
 * $LicenseInfo:firstyear=2007&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#include "linden_common.h"
#include "llblowfishcipher.h"
#include <openssl/evp.h>


LLBlowfishCipher::LLBlowfishCipher(const U8* secret, size_t secret_size)
:   LLCipher()
{
    llassert(secret);

    mSecretSize = secret_size;
    mSecret = new U8[mSecretSize];
    memcpy(mSecret, secret, mSecretSize);
}

LLBlowfishCipher::~LLBlowfishCipher()
{
    delete [] mSecret;
    mSecret = NULL;
}

// virtual
U32 LLBlowfishCipher::encrypt(const U8* src, U32 src_len, U8* dst, U32 dst_len)
{
    if (!src || !src_len || !dst || !dst_len) return 0;
    if (src_len > dst_len) return 0;

    // OpenSSL uses "cipher contexts" to hold encryption parameters.
    EVP_CIPHER_CTX *context = EVP_CIPHER_CTX_new();
    if (!context)
    {
        LL_WARNS() << "LLBlowfishCipher::encrypt EVP_CIPHER_CTX initiation failure" << LL_ENDL;
        return 0;
    }

    // We want a blowfish cyclic block chain cipher, but need to set
    // the key length before we pass in a key, so call EncryptInit
    // first with NULLs.
    EVP_EncryptInit_ex(context, EVP_bf_cbc(), NULL, NULL, NULL);
    EVP_CIPHER_CTX_set_key_length(context, (int)mSecretSize);

    // Complete initialization.  Per EVP_EncryptInit man page, the
    // cipher pointer must be NULL.  Apparently initial_vector must
    // be 8 bytes for blowfish, as this is the block size.
    unsigned char initial_vector[] = { 0, 0, 0, 0, 0, 0, 0, 0 };
    EVP_EncryptInit_ex(context, NULL, NULL, mSecret, initial_vector);

    int blocksize = EVP_CIPHER_CTX_block_size(context);
    int keylen = EVP_CIPHER_CTX_key_length(context);
    int iv_length = EVP_CIPHER_CTX_iv_length(context);
    LL_DEBUGS() << "LLBlowfishCipher blocksize " << blocksize
        << " keylen " << keylen
        << " iv_len " << iv_length
        << LL_ENDL;

    int output_len = 0;
    int temp_len = 0;
    if (!EVP_EncryptUpdate(context,
            dst,
            &output_len,
            src,
            src_len))
    {
        LL_WARNS() << "LLBlowfishCipher::encrypt EVP_EncryptUpdate failure" << LL_ENDL;
        goto BF_ENCRYPT_ERROR;
    }

    // There may be some final data left to encrypt if the input is
    // not an exact multiple of the block size.
    if (!EVP_EncryptFinal_ex(context, (unsigned char*)(dst + output_len), &temp_len))
    {
        LL_WARNS() << "LLBlowfishCipher::encrypt EVP_EncryptFinal failure" << LL_ENDL;
        goto BF_ENCRYPT_ERROR;
    }
    output_len += temp_len;

    EVP_CIPHER_CTX_free(context);
    return output_len;

BF_ENCRYPT_ERROR:
    EVP_CIPHER_CTX_free(context);
    return 0;
}

// virtual
U32 LLBlowfishCipher::decrypt(const U8* src, U32 src_len, U8* dst, U32 dst_len)
{
    LL_ERRS() << "LLBlowfishCipher decrypt unsupported" << LL_ENDL;
    return 0;
}

// virtual
U32 LLBlowfishCipher::requiredEncryptionSpace(U32 len) const
{
    // *HACK: We know blowfish uses an 8 byte block size.
    // Oddly, sometimes EVP_Encrypt produces an extra block
    // if the input is an exact multiple of the block size.
    // So round up.
    const U32 BLOCK_SIZE = 8;
    len += BLOCK_SIZE;
    len -= (len % BLOCK_SIZE);
    return len;
}