/* md5.d - RSA Data Security, Inc., MD5 message-digest algorithm
 * Derived from the RSA Data Security, Inc. MD5 Message-Digest Algorithm.
 */

/**
 * Computes MD5 digests of arbitrary data. MD5 digests are 16 byte quantities that are like a checksum or crc, but are more robust.
 *
 * There are two ways to do this. The first does it all in one function call to
 * sum(). The second is for when the data is buffered.
 *
 * Bugs:
 * MD5 digests have been demonstrated to not be unique.
 *
 * Author:
 * The routines and algorithms are derived from the
 * $(I RSA Data Security, Inc. MD5 Message-Digest Algorithm).
 *
 * References:
 *      $(LINK2 http://en.wikipedia.org/wiki/Md5, Wikipedia on MD5)
 *
 * Macros:
 *      WIKI = Phobos/StdMd5
 */

/++++++++++++++++++++++++++++++++
 Example:

--------------------
// This code is derived from the
// RSA Data Security, Inc. MD5 Message-Digest Algorithm.

import std.md5;

private import std.stdio;
private import std.string;
private import std.c.stdio;
private import std.c.string;

int main(char[][] args)
{
    foreach (char[] arg; args)
         MDFile(arg);
    return 0;
}

/* Digests a file and prints the result. */
void MDFile(char[] filename)
{
    FILE* file;
    MD5_CTX context;
    int len;
    ubyte[4 * 1024] buffer;
    ubyte digest[16];

    if ((file = fopen(std.string.toStringz(filename), "rb")) == null)
        writefln("%s can't be opened", filename);
    else
    {
        context.start();
        while ((len = fread(buffer, 1, buffer.sizeof, file)) != 0)
            context.update(buffer[0 .. len]);
        context.finish(digest);
        fclose(file);

        writefln("MD5 (%s) = %s", filename, digestToString(digest));
    }
}
--------------------
 +/

/* 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.
 */

module std.md5;

//debug=md5;            // uncomment to turn on debugging printf's

import std.string;

/***************************************
 * Computes MD5 digest of array of data.
 */

void sum(ubyte[16] digest, void[] data)
{
    MD5_CTX context;

    context.start();
    context.update(data);
    context.finish(digest);
}

/******************
 * Prints a message digest in hexadecimal to stdout.
 */
void printDigest(ubyte digest[16])
{
    foreach (ubyte u; digest)
        printf("%02x", u);
}

/****************************************
 * Converts MD5 digest to a string.
 */

char[] digestToString(ubyte[16] digest)
{
    char[] result = new char[32];
    int i;

    foreach (ubyte u; digest)
    {
        result[i] = std.string.hexdigits[u >> 4];
        result[i + 1] = std.string.hexdigits[u & 15];
        i += 2;
    }
    return result;
}

/**
 * Holds context of MD5 computation.
 *
 * Used when data to be digested is buffered.
 */
struct MD5_CTX
{
    uint state[4] =                                   /* state (ABCD) */
    /* magic initialization constants */
    [0x67452301,0xefcdab89,0x98badcfe,0x10325476];

    ulong count;        /* number of bits, modulo 2^64 */
    ubyte buffer[64];   /* input buffer */

    static ubyte[64] PADDING =
    [
      0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
    ];

    /* F, G, H and I are basic MD5 functions.
     */
    private static
    {
        uint F(uint x, uint y, uint z) { return (x & y) | (~x & z); }
        uint G(uint x, uint y, uint z) { return (x & z) | (y & ~z); }
        uint H(uint x, uint y, uint z) { return x ^ y ^ z; }
        uint I(uint x, uint y, uint z) { return y ^ (x | ~z); }
    }

    /* ROTATE_LEFT rotates x left n bits.
     */
    static uint ROTATE_LEFT(uint x, uint n)
    {
        version (D_InlineAsm_X86)
        {
            asm
            {   naked                   ;
                mov     ECX,EAX         ;
                mov     EAX,4[ESP]      ;
                rol     EAX,CL          ;
                ret     4               ;
            }
        }
        else
        {
            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.
     */
    static void FF(inout uint a, uint b, uint c, uint d, uint x, uint s, uint ac)
    {
        a += F (b, c, d) + x + cast(uint)(ac);
        a = ROTATE_LEFT (a, s);
        a += b;
    }

    static void GG(inout uint a, uint b, uint c, uint d, uint x, uint s, uint ac)
    {
        a += G (b, c, d) + x + cast(uint)(ac);
        a = ROTATE_LEFT (a, s);
        a += b;
    }

    static void HH(inout uint a, uint b, uint c, uint d, uint x, uint s, uint ac)
    {
        a += H (b, c, d) + x + cast(uint)(ac);
        a = ROTATE_LEFT (a, s);
        a += b;
    }

    static void II(inout uint a, uint b, uint c, uint d, uint x, uint s, uint ac)
    {
        a += I (b, c, d) + x + cast(uint)(ac);
        a = ROTATE_LEFT (a, s);
        a += b;
    }

    /**
     * MD5 initialization. Begins an MD5 operation, writing a new context.
     */
    void start()
    {
        *this = MD5_CTX.init;
    }

    /** MD5 block update operation. Continues an MD5 message-digest
      operation, processing another message block, and updating the
      context.
     */
    void update(void[] input)
    {
      size_t i, index, partLen;
      auto inputLen = input.length;

      /* Compute number of bytes mod 64 */
      index = (cast(uint)count >> 3) & (64 - 1);

      /* Update number of bits */
      count += inputLen * 8;

      partLen = 64 - index;

      /* Transform as many times as possible. */
      if (inputLen >= partLen)
      {
            std.c.string.memcpy(&buffer[index], input.ptr, partLen);
            transform (buffer.ptr);

            for (i = partLen; i + 63 < inputLen; i += 64)
               transform ((cast(ubyte[])input)[i .. i + 64].ptr);

            index = 0;
      }
      else
            i = 0;

      /* Buffer remaining input */
      if (inputLen - i)
            std.c.string.memcpy(&buffer[index], &input[i], inputLen-i);
    }

    /** MD5 finalization. Ends an MD5 message-digest operation, writing the
     * the message to digest and zeroing the context.
     */
    void finish(ubyte[16] digest)         /* message digest */
    {
      ubyte bits[8];
      uint index, padLen;
      uint[2] cnt;

      /* Save number of bits */
      cnt[0] = cast(uint)count;
      cnt[1] = cast(uint)(count >> 32);
      Encode (bits.ptr, cnt.ptr, 8);

      /* Pad out to 56 mod 64. */
      index = (cast(uint)count >> 3) & (64 - 1);
      padLen = (index < 56) ? (56 - index) : (120 - index);
      update (PADDING[0 .. padLen]);

      /* Append length (before padding) */
      update (bits);

      /* Store state in digest */
      Encode (digest.ptr, state.ptr, 16);

      /* Zeroize sensitive information. */
      std.c.string.memset (this, 0, MD5_CTX.sizeof);
    }

    /* MD5 basic transformation. Transforms state based on block.
     */

    /* Constants for MD5Transform routine. */
    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,
    }

    private void transform (ubyte* /*[64]*/ block)
    {
      uint a = state[0],
           b = state[1],
           c = state[2],
           d = state[3];
      uint[16] x;

      Decode (x.ptr, block, 64);

      /* 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. */
      x[] = 0;
    }

    /* Encodes input (uint) into output (ubyte). Assumes len is
      a multiple of 4.
     */
    private static void Encode (ubyte *output, uint *input, uint len)
    {
        uint i, j;

        for (i = 0, j = 0; j < len; i++, j += 4)
        {
            uint u = input[i];
            output[j]   = cast(ubyte)(u);
            output[j+1] = cast(ubyte)(u >> 8);
            output[j+2] = cast(ubyte)(u >> 16);
            output[j+3] = cast(ubyte)(u >> 24);
        }
    }

    /* Decodes input (ubyte) into output (uint). Assumes len is
      a multiple of 4.
     */
    private static void Decode (uint *output, ubyte *input, uint len)
    {
        uint i, j;

        for (i = 0, j = 0; j < len; i++, j += 4)
        {
            version (LittleEndian)
            {
                output[i] = *cast(uint*)&input[j];
            }
            else
            {
                output[i] = (cast(uint)input[j]) | ((cast(uint)input[j+1]) << 8) |
                        ((cast(uint)input[j+2]) << 16) | ((cast(uint)input[j+3]) << 24);
            }
        }
    }
}

unittest
{
    debug(md5) printf("std.md5.unittest\n");

    ubyte[16] digest;

    sum (digest, "");
    assert(digest == cast(ubyte[])x"d41d8cd98f00b204e9800998ecf8427e");

    sum (digest, "a");
    assert(digest == cast(ubyte[])x"0cc175b9c0f1b6a831c399e269772661");

    sum (digest, "abc");
    assert(digest == cast(ubyte[])x"900150983cd24fb0d6963f7d28e17f72");

    sum (digest, "message digest");
    assert(digest == cast(ubyte[])x"f96b697d7cb7938d525a2f31aaf161d0");

    sum (digest, "abcdefghijklmnopqrstuvwxyz");
    assert(digest == cast(ubyte[])x"c3fcd3d76192e4007dfb496cca67e13b");

    sum (digest, "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789");
    assert(digest == cast(ubyte[])x"d174ab98d277d9f5a5611c2c9f419d9f");

    sum (digest,
        "1234567890123456789012345678901234567890"
        "1234567890123456789012345678901234567890");
    assert(digest == cast(ubyte[])x"57edf4a22be3c955ac49da2e2107b67a");

    assert(digestToString(cast(ubyte[16])x"c3fcd3d76192e4007dfb496cca67e13b")
        == "C3FCD3D76192E4007DFB496CCA67E13B");
}

