c_md5.c

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/* md5sum.c - Compute MD5 checksum of files or strings according to the
 *            definition of MD5 in RFC 1321 from April 1992.
 * Copyright (C) 1995-1999 Free Software Foundation, Inc.
 *
 * 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.
 */

#include "c_md5.h"

#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <getopt.h>

#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <endian.h>
#include <unistd.h>
#include  <fcntl.h>


typedef u_int32_t md5_uint32;

/* Structure to save state of computation between the single steps.  */
struct md5_ctx
{
  md5_uint32 A;
  md5_uint32 B;
  md5_uint32 C;
  md5_uint32 D;

  md5_uint32 total[2];
  md5_uint32 buflen;
  char buffer[128];
};

#define SWAP(n) (n)

/* 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, ...  */  };

/* 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))


#define OPENOPTS(BINARY) "r"


/* 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  = 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, 0xd76aa478);
    OP(D, A, B, C, 12, 0xe8c7b756);
    OP(C, D, A, B, 17, 0x242070db);
    OP(B, C, D, A, 22, 0xc1bdceee);
    OP(A, B, C, D,  7, 0xf57c0faf);
    OP(D, A, B, C, 12, 0x4787c62a);
    OP(C, D, A, B, 17, 0xa8304613);
    OP(B, C, D, A, 22, 0xfd469501);
    OP(A, B, C, D,  7, 0x698098d8);
    OP(D, A, B, C, 12, 0x8b44f7af);
    OP(C, D, A, B, 17, 0xffff5bb1);
    OP(B, C, D, A, 22, 0x895cd7be);
    OP(A, B, C, D,  7, 0x6b901122);
    OP(D, A, B, C, 12, 0xfd987193);
    OP(C, D, A, B, 17, 0xa679438e);
    OP(B, C, D, A, 22, 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(f, a, b, c, d, k, s, T)                  \
    do                                                        \
   {                                                            \
        a += f (b, c, d) + correct_words[k] + T;    \
        CYCLIC (a, s);                                      \
        a += b;                                               \
      }                                                         \
    while (0)

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

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

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



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 char *) buffer + add;
    len    -=  add;
  }

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

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



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


/* An interface to md5_stream.  Operate on FILENAME (it may be "-") and
   put the result in *MD5_RESULT.  Return non-zero upon failure, zero
   to indicate success.
*/
int md5_file(char *filename, int binary, unsigned char *md5_result)
{
  FILE *fp;

  fp = fopen(filename, OPENOPTS(binary));
  if (fp == NULL)
  {
    printf("md5sum: %s: %s\n", filename, strerror(errno));
    return 0;
  }

  if (md5_stream(fp, md5_result))
  {
    printf("md5sum: %s: %s\n", filename, strerror(errno));

    if (fp != stdin)
    {
      fclose(fp);
    }
    return 0;
  }


  if (fp != stdin && fclose(fp) == EOF)
  {
    printf("md5sum: %s: %s\n", filename, strerror(errno));
    return 0;
  }

  return 1;
}