/* md5.c - Functions to compute MD5 message digest of files or memory blocks
 *  according to the definition of MD5 in RFC 1321 from April 1992.
 *  Copyright (C) 1995, 1996 Free Software Foundation, Inc.
 *
 *  NOTE: This source is derived from an old version taken from the GNU C
 *  Library (glibc).
 *
 *  This program is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License as published by the
 *  Free Software Foundation; either version 2, or (at your option) any
 *  later version.
 *
 *  This program 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 for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software Foundation,
 *  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <sys/types.h>

# include <stdlib.h>
# include <string.h>

#include "ansidecl.h"
#include "md5.h"

#ifdef __APPLE__
    # include <machine/endian.h>
#elif !defined( _WIN32 )
    # include <endian.h>
#endif
# if __BYTE_ORDER == __BIG_ENDIAN
#  define WORDS_BIGENDIAN 1
# endif

#ifdef WORDS_BIGENDIAN
# define SWAP(n)                            \
(((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
#else
# define SWAP(n) (n)
#endif


/* This array contains the bytes used to pad the buffer to the next
 * 64-byte boundary.  (RFC 1321, 3.1: Step 1)  */
static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */ };


/* Initialize structure containing state of computation.
 *  (RFC 1321, 3.3: Step 3)  */
void
md5_init_ctx ( struct md5_ctx *ctx )
{
    ctx->A = (md5_uint32) 0x67452301;
    ctx->B = (md5_uint32) 0xefcdab89;
    ctx->C = (md5_uint32) 0x98badcfe;
    ctx->D = (md5_uint32) 0x10325476;

    ctx->total[0] = ctx->total[1] = 0;
    ctx->buflen = 0;
}

/* Put result from CTX in first 16 bytes following RESBUF.  The result
 * must be in little endian byte order.
 *
 * IMPORTANT: On some systems it is required that RESBUF is correctly
 * aligned for a 32 bits value.  */
void *
md5_read_ctx ( const struct md5_ctx *ctx, void *resbuf )
{
    ((md5_uint32 *) resbuf)[0] = SWAP (ctx->A);
    ((md5_uint32 *) resbuf)[1] = SWAP (ctx->B);
    ((md5_uint32 *) resbuf)[2] = SWAP (ctx->C);
    ((md5_uint32 *) resbuf)[3] = SWAP (ctx->D);

    return resbuf;
}

/* Process the remaining bytes in the internal buffer and the usual
 * prolog according to the standard and write the result to RESBUF.
 *
 * IMPORTANT: On some systems it is required that RESBUF is correctly
 * aligned for a 32 bits value.  */
void *
md5_finish_ctx ( struct md5_ctx *ctx, void *resbuf )
{
    /* Take yet unprocessed bytes into account.  */
    md5_uint32 bytes = ctx->buflen;
    size_t pad;

    /* Now count remaining bytes.  */
    ctx->total[0] += bytes;
    if (ctx->total[0] < bytes)
        ++ctx->total[1];

    pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
    memcpy (&ctx->buffer[bytes], fillbuf, pad);

    /* Put the 64-bit file length in *bits* at the end of the buffer.  */
    *(md5_uint32 *) (&ctx->buffer[bytes + pad]) = SWAP (ctx->total[0] << 3);
    *(md5_uint32 *) (&ctx->buffer[bytes + pad + 4]) = SWAP ((ctx->total[1] << 3) |
                               (ctx->total[0] >> 29));

    /* Process last bytes.  */
    md5_process_block (ctx->buffer, bytes + pad + 8, ctx);

    return md5_read_ctx (ctx, resbuf);
}

/* Compute MD5 message digest for bytes read from STREAM.  The
 * resulting message digest number will be written into the 16 bytes
 * beginning at RESBLOCK.  */
int
md5_stream ( FILE *stream, void *resblock )
{
    /* Important: BLOCKSIZE must be a multiple of 64.  */
    #define BLOCKSIZE 4096
    struct md5_ctx ctx;
    char buffer[BLOCKSIZE + 72];
    size_t sum;

    /* Initialize the computation context.  */
    md5_init_ctx (&ctx);

    /* Iterate over full file contents.  */
    while (1)
    {
        /* We read the file in blocks of BLOCKSIZE bytes.  One call of the
         *    computation function processes the whole buffer so that with the
         *    next round of the loop another block can be read.  */
        size_t n;
        sum = 0;

        /* Read block.  Take care for partial reads.  */
        do
        {
            n = fread (buffer + sum, 1, BLOCKSIZE - sum, stream);

            sum += n;
        }
        while (sum < BLOCKSIZE && n != 0);
        if (n == 0 && ferror (stream))
            return 1;

        /* If end of file is reached, end the loop.  */
        if (n == 0)
            break;

        /* Process buffer with BLOCKSIZE bytes.  Note that
         *           BLOCKSIZE % 64 == 0
         */
        md5_process_block (buffer, BLOCKSIZE, &ctx);
    }

    /* Add the last bytes if necessary.  */
    if (sum > 0)
        md5_process_bytes (buffer, sum, &ctx);

    /* Construct result in desired memory.  */
    md5_finish_ctx (&ctx, resblock);
    return 0;
}

/* Compute MD5 message digest for LEN bytes beginning at BUFFER.  The
 * result is always in little endian byte order, so that a byte-wise
 * output yields to the wanted ASCII representation of the message
 * digest.  */
void *
md5_buffer ( const char *buffer, size_t len, void *resblock )
{
    struct md5_ctx ctx;

    /* Initialize the computation context.  */
    md5_init_ctx (&ctx);

    /* Process whole buffer but last len % 64 bytes.  */
    md5_process_bytes (buffer, len, &ctx);

    /* Put result in desired memory area.  */
    return md5_finish_ctx (&ctx, resblock);
}


void
md5_process_bytes ( const void *buffer, size_t len, struct md5_ctx *ctx )
{
    /* When we already have some bits in our internal buffer concatenate
     *    both inputs first.  */
    if (ctx->buflen != 0)
    {
        size_t left_over = ctx->buflen;
        size_t add = 128 - left_over > len ? len : 128 - left_over;

        memcpy (&ctx->buffer[left_over], buffer, add);
        ctx->buflen += add;

        if (left_over + add > 64)
        {
            md5_process_block (ctx->buffer, (left_over + add) & ~63, ctx);
            /* The regions in the following copy operation cannot overlap.  */
            memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63],
                    (left_over + add) & 63);
            ctx->buflen = (left_over + add) & 63;
        }

        buffer = (const void *) ((const char *) buffer + add);
        len -= add;
    }

    /* Process available complete blocks.  */
    if (len > 64)
    {
        md5_process_block (buffer, len & ~63, ctx);
        buffer = (const void *) ((const char *) buffer + (len & ~63));
        len &= 63;
    }

    /* Move remaining bytes in internal buffer.  */
    if (len > 0)
    {
        memcpy (ctx->buffer, buffer, len);
        ctx->buflen = len;
    }
}


/* These are the four functions used in the four steps of the MD5 algorithm
 * and defined in the RFC 1321.  The first function is a little bit optimized
 * (as found in Colin Plumbs public domain implementation).  */
/* #define FF(b, c, d) ((b & c) | (~b & d)) */
#define FF(b, c, d) (d ^ (b & (c ^ d)))
#define FG(b, c, d) FF (d, b, c)
#define FH(b, c, d) (b ^ c ^ d)
#define FI(b, c, d) (c ^ (b | ~d))

/* Process LEN bytes of BUFFER, accumulating context into CTX.
 *  It is assumed that LEN % 64 == 0.  */

void
md5_process_block ( const void *buffer, size_t len, struct md5_ctx *ctx )
{
    md5_uint32 correct_words[16];
    const md5_uint32 *words = (const md5_uint32 *) buffer;
    size_t nwords = len / sizeof (md5_uint32);
    const md5_uint32 *endp = words + nwords;
    md5_uint32 A = ctx->A;
    md5_uint32 B = ctx->B;
    md5_uint32 C = ctx->C;
    md5_uint32 D = ctx->D;

    /* First increment the byte count.  RFC 1321 specifies the possible
     * length of the file up to 2^64 bits.  Here we only compute the
     * number of bytes.  Do a double word increment.  */
    ctx->total[0] += len;
    if (ctx->total[0] < len)
        ++ctx->total[1];

    /* Process all bytes in the buffer with 64 bytes in each round of
     * the loop.  */
    while (words < endp)
    {
        md5_uint32 *cwp = correct_words;
        md5_uint32 A_save = A;
        md5_uint32 B_save = B;
        md5_uint32 C_save = C;
        md5_uint32 D_save = D;

        /* First round: using the given function, the context and a constant
         * the next context is computed.  Because the algorithms processing
         * unit is a 32-bit word and it is determined to work on words in
         * little endian byte order we perhaps have to change the byte order
         * before the computation.  To reduce the work for the next steps
         * we store the swapped words in the array CORRECT_WORDS.  */

        #define OP(a, b, c, d, s, T)                        \
        do                                \
        {                               \
        a += FF (b, c, d) + (*cwp++ = SWAP (*words)) + T;     \
        ++words;                          \
        CYCLIC (a, s);                        \
        a += b;                           \
    }                               \
    while (0)

        /* It is unfortunate that C does not provide an operator for
         * cyclic rotation.  Hope the C compiler is smart enough.  */
        #define CYCLIC(w, s) (w = (w << s) | (w >> (32 - s)))

        /* Before we start, one word to the strange constants.
         *    They are defined in RFC 1321 as
         *
         *    T[i] = (int) (4294967296.0 * fabs (sin (i))), i=1..64
         */

        /* Round 1.  */
        OP (A, B, C, D,  7, (md5_uint32) 0xd76aa478);
        OP (D, A, B, C, 12, (md5_uint32) 0xe8c7b756);
        OP (C, D, A, B, 17, (md5_uint32) 0x242070db);
        OP (B, C, D, A, 22, (md5_uint32) 0xc1bdceee);
        OP (A, B, C, D,  7, (md5_uint32) 0xf57c0faf);
        OP (D, A, B, C, 12, (md5_uint32) 0x4787c62a);
        OP (C, D, A, B, 17, (md5_uint32) 0xa8304613);
        OP (B, C, D, A, 22, (md5_uint32) 0xfd469501);
        OP (A, B, C, D,  7, (md5_uint32) 0x698098d8);
        OP (D, A, B, C, 12, (md5_uint32) 0x8b44f7af);
        OP (C, D, A, B, 17, (md5_uint32) 0xffff5bb1);
        OP (B, C, D, A, 22, (md5_uint32) 0x895cd7be);
        OP (A, B, C, D,  7, (md5_uint32) 0x6b901122);
        OP (D, A, B, C, 12, (md5_uint32) 0xfd987193);
        OP (C, D, A, B, 17, (md5_uint32) 0xa679438e);
        OP (B, C, D, A, 22, (md5_uint32) 0x49b40821);

        /* For the second to fourth round we have the possibly swapped words
         * in CORRECT_WORDS.  Redefine the macro to take an additional first
         * argument specifying the function to use.  */
        #undef OP
        #define OP(a, b, c, d, k, s, T)                     \
        do                                \
        {                               \
        a += FX (b, c, d) + correct_words[k] + T;         \
        CYCLIC (a, s);                        \
        a += b;                           \
    }                               \
    while (0)

        #define FX(b, c, d) FG (b, c, d)

        /* Round 2.  */
        OP (A, B, C, D,  1,  5, (md5_uint32) 0xf61e2562);
    OP (D, A, B, C,  6,  9, (md5_uint32) 0xc040b340);
    OP (C, D, A, B, 11, 14, (md5_uint32) 0x265e5a51);
    OP (B, C, D, A,  0, 20, (md5_uint32) 0xe9b6c7aa);
    OP (A, B, C, D,  5,  5, (md5_uint32) 0xd62f105d);
    OP (D, A, B, C, 10,  9, (md5_uint32) 0x02441453);
    OP (C, D, A, B, 15, 14, (md5_uint32) 0xd8a1e681);
    OP (B, C, D, A,  4, 20, (md5_uint32) 0xe7d3fbc8);
    OP (A, B, C, D,  9,  5, (md5_uint32) 0x21e1cde6);
    OP (D, A, B, C, 14,  9, (md5_uint32) 0xc33707d6);
    OP (C, D, A, B,  3, 14, (md5_uint32) 0xf4d50d87);
    OP (B, C, D, A,  8, 20, (md5_uint32) 0x455a14ed);
    OP (A, B, C, D, 13,  5, (md5_uint32) 0xa9e3e905);
    OP (D, A, B, C,  2,  9, (md5_uint32) 0xfcefa3f8);
    OP (C, D, A, B,  7, 14, (md5_uint32) 0x676f02d9);
    OP (B, C, D, A, 12, 20, (md5_uint32) 0x8d2a4c8a);

    #undef FX
    #define FX(b, c, d) FH (b, c, d)

    /* Round 3.  */
    OP (A, B, C, D,  5,  4, (md5_uint32) 0xfffa3942);
    OP (D, A, B, C,  8, 11, (md5_uint32) 0x8771f681);
    OP (C, D, A, B, 11, 16, (md5_uint32) 0x6d9d6122);
    OP (B, C, D, A, 14, 23, (md5_uint32) 0xfde5380c);
    OP (A, B, C, D,  1,  4, (md5_uint32) 0xa4beea44);
    OP (D, A, B, C,  4, 11, (md5_uint32) 0x4bdecfa9);
    OP (C, D, A, B,  7, 16, (md5_uint32) 0xf6bb4b60);
    OP (B, C, D, A, 10, 23, (md5_uint32) 0xbebfbc70);
    OP (A, B, C, D, 13,  4, (md5_uint32) 0x289b7ec6);
    OP (D, A, B, C,  0, 11, (md5_uint32) 0xeaa127fa);
    OP (C, D, A, B,  3, 16, (md5_uint32) 0xd4ef3085);
    OP (B, C, D, A,  6, 23, (md5_uint32) 0x04881d05);
    OP (A, B, C, D,  9,  4, (md5_uint32) 0xd9d4d039);
    OP (D, A, B, C, 12, 11, (md5_uint32) 0xe6db99e5);
    OP (C, D, A, B, 15, 16, (md5_uint32) 0x1fa27cf8);
    OP (B, C, D, A,  2, 23, (md5_uint32) 0xc4ac5665);

    #undef FX
    #define FX(b, c, d) FI (b, c, d)

    /* Round 4.  */
    OP (A, B, C, D,  0,  6, (md5_uint32) 0xf4292244);
    OP (D, A, B, C,  7, 10, (md5_uint32) 0x432aff97);
    OP (C, D, A, B, 14, 15, (md5_uint32) 0xab9423a7);
    OP (B, C, D, A,  5, 21, (md5_uint32) 0xfc93a039);
    OP (A, B, C, D, 12,  6, (md5_uint32) 0x655b59c3);
    OP (D, A, B, C,  3, 10, (md5_uint32) 0x8f0ccc92);
    OP (C, D, A, B, 10, 15, (md5_uint32) 0xffeff47d);
    OP (B, C, D, A,  1, 21, (md5_uint32) 0x85845dd1);
    OP (A, B, C, D,  8,  6, (md5_uint32) 0x6fa87e4f);
    OP (D, A, B, C, 15, 10, (md5_uint32) 0xfe2ce6e0);
    OP (C, D, A, B,  6, 15, (md5_uint32) 0xa3014314);
    OP (B, C, D, A, 13, 21, (md5_uint32) 0x4e0811a1);
    OP (A, B, C, D,  4,  6, (md5_uint32) 0xf7537e82);
    OP (D, A, B, C, 11, 10, (md5_uint32) 0xbd3af235);
    OP (C, D, A, B,  2, 15, (md5_uint32) 0x2ad7d2bb);
    OP (B, C, D, A,  9, 21, (md5_uint32) 0xeb86d391);

    /* Add the starting values of the context.  */
    A += A_save;
    B += B_save;
    C += C_save;
    D += D_save;
    }

    /* Put checksum in context given as argument.  */
    ctx->A = A;
    ctx->B = B;
    ctx->C = C;
    ctx->D = D;
}