// Copyright (C) 2016 xaizek <xaizek@posteo.net>
//
// This file is part of uncov.
//
// uncov is free software: you can redistribute it and/or modify
// it under the terms of version 3 of the GNU Affero General Public License as
// published by the Free Software Foundation.
//
// uncov 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with uncov.  If not, see <http://www.gnu.org/licenses/>.

// Converted to C++ class by Frank Thilo (thilo@unix-ag.org)
// for bzflag (http://www.bzflag.org)
//
//   based on:
//
//   md5.h and md5.c
//   reference implementation of RFC 1321
//
//   Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
// rights reserved.
//
// License to copy and use this software is granted provided that it
// is identified as the "RSA Data Security, Inc. MD5 Message-Digest
// Algorithm" in all material mentioning or referencing this software
// or this function.
//
// License is also granted to make and use derivative works provided
// that such works are identified as "derived from the RSA Data
// Security, Inc. MD5 Message-Digest Algorithm" in all material
// mentioning or referencing the derived work.
//
// RSA Data Security, Inc. makes no representations concerning either
// the merchantability of this software or the suitability of this
// software for any particular purpose. It is provided "as is"
// without express or implied warranty of any kind.
//
// These notices must be retained in any copies of any part of this
// documentation and/or software.

#include "utils/md5.hpp"

#include <cstdint>
#include <cstring>

// a small class for calculating MD5 hashes of strings or byte arrays
// it is not meant to be fast or secure
//
// usage: 1) feed it blocks of uchars with update()
//      2) finalize()
//      3) get hexdigest() string
//      or
//      MD5(std::string).hexdigest()
class MD5
{
public:
    typedef std::uint32_t size_type; // must be 32bit

    MD5();
    MD5(const std::string& text);
    void update(const unsigned char buf[], size_type length);
    void update(const char input[], size_type length);
    MD5& finalize();
    std::string hexdigest() const;

private:
    void init();
    typedef std::uint8_t uint1;   //  8bit
    typedef std::uint32_t uint4;  // 32bit
    enum {blocksize = 64}; // VC6 won't eat a const static int here

    void transform(const uint1 block[blocksize]);
    static void decode(uint4 output[], const uint1 input[], size_type len);
    static void encode(uint1 output[], const uint4 input[], size_type len);

    bool finalized;
    uint1 buffer[blocksize]; // bytes that didn't fit in last 64 byte chunk
    uint4 count[2];   // 64bit counter for number of bits (lo, hi)
    uint4 state[4];   // digest so far
    uint1 digest[16]; // the result

    // low level logic operations
    static inline uint4 F(uint4 x, uint4 y, uint4 z);
    static inline uint4 G(uint4 x, uint4 y, uint4 z);
    static inline uint4 H(uint4 x, uint4 y, uint4 z);
    static inline uint4 I(uint4 x, uint4 y, uint4 z);
    static inline uint4 rotate_left(uint4 x, int n);
    static inline void FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
    static inline void GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
    static inline void HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
    static inline void II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
};

// F, G, H and I are basic MD5 functions.
inline MD5::uint4 MD5::F(uint4 x, uint4 y, uint4 z)
{
    return (x&y) | (~x&z);
}

inline MD5::uint4 MD5::G(uint4 x, uint4 y, uint4 z)
{
    return (x&z) | (y&~z);
}

inline MD5::uint4 MD5::H(uint4 x, uint4 y, uint4 z)
{
    return x^y^z;
}

inline MD5::uint4 MD5::I(uint4 x, uint4 y, uint4 z)
{
    return y ^ (x | ~z);
}

// rotate_left rotates x left n bits.
inline MD5::uint4 MD5::rotate_left(uint4 x, int n)
{
    return (x << n) | (x >> (32-n));
}

// FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
// Rotation is separate from addition to prevent recomputation.
inline void MD5::FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
{
    a = rotate_left(a+ F(b,c,d) + x + ac, s) + b;
}

inline void MD5::GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
{
    a = rotate_left(a + G(b,c,d) + x + ac, s) + b;
}

inline void MD5::HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
{
    a = rotate_left(a + H(b,c,d) + x + ac, s) + b;
}

inline void MD5::II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
{
    a = rotate_left(a + I(b,c,d) + x + ac, s) + b;
}

// default ctor, just initailize
MD5::MD5()
{
    init();
}

// nifty shortcut ctor, compute MD5 for string and finalize it right away
MD5::MD5(const std::string &text)
{
    init();
    update(text.c_str(), text.length());
    finalize();
}

void MD5::init()
{
    finalized=false;

    count[0] = 0;
    count[1] = 0;

    // load magic initialization constants.
    state[0] = 0x67452301;
    state[1] = 0xefcdab89;
    state[2] = 0x98badcfe;
    state[3] = 0x10325476;
}

// decodes input (unsigned char) into output (uint4). Assumes len is a multiple of 4.
void MD5::decode(uint4 output[], const uint1 input[], size_type len)
{
    for (unsigned int i = 0, j = 0; j < len; ++i, j += 4) {
        output[i] = ((uint4)input[j]) | (((uint4)input[j + 1]) << 8) |
            (((uint4)input[j + 2]) << 16) | (((uint4)input[j + 3]) << 24);
    }
}

// encodes input (uint4) into output (unsigned char). Assumes len is
// a multiple of 4.
void MD5::encode(uint1 output[], const uint4 input[], size_type len)
{
    for (size_type i = 0, j = 0; j < len; ++i, j += 4) {
        output[j] = input[i] & 0xff;
        output[j+1] = (input[i] >> 8) & 0xff;
        output[j+2] = (input[i] >> 16) & 0xff;
        output[j+3] = (input[i] >> 24) & 0xff;
    }
}

// apply MD5 algo on a block
void MD5::transform(const uint1 block[blocksize])
{
    enum {
        S11 = 7, S12 = 12, S13 = 17, S14 = 22,
        S21 = 5, S22 =  9, S23 = 14, S24 = 20,
        S31 = 4, S32 = 11, S33 = 16, S34 = 23,
        S41 = 6, S42 = 10, S43 = 15, S44 = 21,
    };

    uint4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];
    decode(x, block, blocksize);

    /* Round 1 */
    FF(a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
    FF(d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
    FF(c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
    FF(b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
    FF(a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
    FF(d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
    FF(c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
    FF(b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
    FF(a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
    FF(d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
    FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
    FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
    FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
    FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
    FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
    FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

    /* Round 2 */
    GG(a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
    GG(d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
    GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
    GG(b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
    GG(a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
    GG(d, a, b, c, x[10], S22,  0x2441453); /* 22 */
    GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
    GG(b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
    GG(a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
    GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
    GG(c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
    GG(b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
    GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
    GG(d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
    GG(c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
    GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

    /* Round 3 */
    HH(a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
    HH(d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
    HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
    HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
    HH(a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
    HH(d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
    HH(c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
    HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
    HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
    HH(d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
    HH(c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
    HH(b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
    HH(a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
    HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
    HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
    HH(b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

    /* Round 4 */
    II(a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
    II(d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
    II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
    II(b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
    II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
    II(d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
    II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
    II(b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
    II(a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
    II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
    II(c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
    II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
    II(a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
    II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
    II(c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
    II(b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;

    // Zeroize sensitive information.
    std::memset(x, 0, sizeof x);
}

// MD5 block update operation. Continues an MD5 message-digest
// operation, processing another message block
void MD5::update(const unsigned char input[], size_type length)
{
    // compute number of bytes mod 64
    size_type index = count[0] / 8 % blocksize;

    // Update number of bits
    if ((count[0] += (length << 3)) < (length << 3)) {
        count[1]++;
    }
    count[1] += (length >> 29);

    // number of bytes we need to fill in buffer
    size_type firstpart = 64 - index;

    size_type i;

    // transform as many times as possible.
    if (length >= firstpart) {
        // fill buffer first, transform
        std::memcpy(&buffer[index], input, firstpart);
        transform(buffer);

        // transform chunks of blocksize (64 bytes)
        for (i = firstpart; i + blocksize <= length; i += blocksize) {
            transform(&input[i]);
        }

        index = 0;
    } else {
        i = 0;
    }

    // buffer remaining input
    std::memcpy(&buffer[index], &input[i], length - i);
}

// for convenience provide a verson with signed char
void MD5::update(const char input[], size_type length)
{
    update(reinterpret_cast<const unsigned char *>(input), length);
}

// MD5 finalization. Ends an MD5 message-digest operation, writing the
// the message digest and zeroizing the context.
MD5& MD5::finalize()
{
    static unsigned char padding[64] = { 0x80 };

    if (!finalized) {
        // Save number of bits
        unsigned char bits[8];
        encode(bits, count, 8);

        // pad out to 56 mod 64.
        size_type index = count[0] / 8 % 64;
        size_type padLen = (index < 56) ? (56 - index) : (120 - index);
        update(padding, padLen);

        // Append length (before padding)
        update(bits, 8);

        // Store state in digest
        encode(digest, state, 16);

        // Zeroize sensitive information.
        std::memset(buffer, 0, sizeof buffer);
        std::memset(count, 0, sizeof count);

        finalized = true;
    }

    return *this;
}

// return hex representation of digest as string
std::string MD5::hexdigest() const
{
    if (!finalized) {
        return std::string();
    }

    char buf[33];
    for (int i = 0; i < 16; ++i) {
        std::sprintf(buf + i*2, "%02x", digest[i]);
    }
    buf[32] = 0;

    return std::string(buf);
}

std::string md5(const std::string &str)
{
   return MD5(str).hexdigest();
}