md5.c

   1 /*
   2  *  md5.c - Compute MD5 checksum of strings according to the
   3  *          definition of MD5 in RFC 1321 from April 1992.
   4  *
   5  *  Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.
   6  *
   7  *  Copyright (C) 1995-1999 Free Software Foundation, Inc.
   8  *  Copyright (C) 2001 Manuel Novoa III
   9  *  Copyright (C) 2003 Glenn L. McGrath
  10  *  Copyright (C) 2003 Erik Andersen
  11  *
  12  *  Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
  13  */
  14
  15 #include <libubox/blob.h> /* TODO: better include for bswap_32 compat */
  16 #include "md5.h"
  17
  18 #if __BYTE_ORDER == __LITTLE_ENDIAN
  19 #define SWAP_LE32(x) (x)
  20 #else
  21 #define SWAP_LE32(x) bswap_32(x)
  22 #endif
  23
  24 /* Initialize structure containing state of computation.
  25  * (RFC 1321, 3.3: Step 3)
  26  */
  27 void md5_begin(md5_ctx_t *ctx)
  28 {
  29         ctx->A = 0x67452301;
  30         ctx->B = 0xefcdab89;
  31         ctx->C = 0x98badcfe;
  32         ctx->D = 0x10325476;
  33
  34         ctx->total = 0;
  35         ctx->buflen = 0;
  36 }
  37
  38 /* These are the four functions used in the four steps of the MD5 algorithm
  39  * and defined in the RFC 1321.  The first function is a little bit optimized
  40  * (as found in Colin Plumbs public domain implementation).
  41  * #define FF(b, c, d) ((b & c) | (~b & d))
  42  */
  43 # define FF(b, c, d) (d ^ (b & (c ^ d)))
  44 # define FG(b, c, d) FF (d, b, c)
  45 # define FH(b, c, d) (b ^ c ^ d)
  46 # define FI(b, c, d) (c ^ (b | ~d))
  47
  48 /* Hash a single block, 64 bytes long and 4-byte aligned. */
  49 static void md5_hash_block(const void *buffer, md5_ctx_t *ctx)
  50 {
  51         uint32_t correct_words[16];
  52         const uint32_t *words = buffer;
  53
  54         static const uint32_t C_array[] = {
  55                 /* round 1 */
  56                 0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
  57                 0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
  58                 0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
  59                 0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
  60                 /* round 2 */
  61                 0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
  62                 0xd62f105d, 0x2441453, 0xd8a1e681, 0xe7d3fbc8,
  63                 0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
  64                 0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
  65                 /* round 3 */
  66                 0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
  67                 0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
  68                 0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x4881d05,
  69                 0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
  70                 /* round 4 */
  71                 0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
  72                 0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
  73                 0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
  74                 0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
  75         };
  76
  77         static const char P_array[] = {
  78                 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,   /* 1 */
  79                 1, 6, 11, 0, 5, 10, 15, 4, 9, 14, 3, 8, 13, 2, 7, 12,   /* 2 */
  80                 5, 8, 11, 14, 1, 4, 7, 10, 13, 0, 3, 6, 9, 12, 15, 2,   /* 3 */
  81                 0, 7, 14, 5, 12, 3, 10, 1, 8, 15, 6, 13, 4, 11, 2, 9    /* 4 */
  82         };
  83
  84         static const char S_array[] = {
  85                 7, 12, 17, 22,
  86                 5, 9, 14, 20,
  87                 4, 11, 16, 23,
  88                 6, 10, 15, 21
  89         };
  90
  91         uint32_t A = ctx->A;
  92         uint32_t B = ctx->B;
  93         uint32_t C = ctx->C;
  94         uint32_t D = ctx->D;
  95
  96         uint32_t *cwp = correct_words;
  97
  98 #  define CYCLIC(w, s) (w = (w << s) | (w >> (32 - s)))
  99
 100         const uint32_t *pc;
 101         const char *pp;
 102         const char *ps;
 103         int i;
 104         uint32_t temp;
 105
 106         for (i = 0; i < 16; i++) {
 107                 cwp[i] = SWAP_LE32(words[i]);
 108         }
 109         words += 16;
 110
 111         pc = C_array;
 112         pp = P_array;
 113         ps = S_array;
 114
 115         for (i = 0; i < 16; i++) {
 116                 temp = A + FF(B, C, D) + cwp[(int) (*pp++)] + *pc++;
 117                 CYCLIC(temp, ps[i & 3]);
 118                 temp += B;
 119                 A = D;
 120                 D = C;
 121                 C = B;
 122                 B = temp;
 123         }
 124
 125         ps += 4;
 126         for (i = 0; i < 16; i++) {
 127                 temp = A + FG(B, C, D) + cwp[(int) (*pp++)] + *pc++;
 128                 CYCLIC(temp, ps[i & 3]);
 129                 temp += B;
 130                 A = D;
 131                 D = C;
 132                 C = B;
 133                 B = temp;
 134         }
 135         ps += 4;
 136         for (i = 0; i < 16; i++) {
 137                 temp = A + FH(B, C, D) + cwp[(int) (*pp++)] + *pc++;
 138                 CYCLIC(temp, ps[i & 3]);
 139                 temp += B;
 140                 A = D;
 141                 D = C;
 142                 C = B;
 143                 B = temp;
 144         }
 145         ps += 4;
 146         for (i = 0; i < 16; i++) {
 147                 temp = A + FI(B, C, D) + cwp[(int) (*pp++)] + *pc++;
 148                 CYCLIC(temp, ps[i & 3]);
 149                 temp += B;
 150                 A = D;
 151                 D = C;
 152                 C = B;
 153                 B = temp;
 154         }
 155
 156
 157         ctx->A += A;
 158         ctx->B += B;
 159         ctx->C += C;
 160         ctx->D += D;
 161 }
 162
 163 /* Feed data through a temporary buffer to call md5_hash_aligned_block()
 164  * with chunks of data that are 4-byte aligned and a multiple of 64 bytes.
 165  * This function's internal buffer remembers previous data until it has 64
 166  * bytes worth to pass on.  Call md5_end() to flush this buffer. */
 167
 168 void md5_hash(const void *buffer, size_t len, md5_ctx_t *ctx)
 169 {
 170         char *buf = (char *)buffer;
 171
 172         /* RFC 1321 specifies the possible length of the file up to 2^64 bits,
 173          * Here we only track the number of bytes.  */
 174
 175         ctx->total += len;
 176
 177         // Process all input.
 178
 179         while (len) {
 180                 unsigned i = 64 - ctx->buflen;
 181
 182                 // Copy data into aligned buffer.
 183
 184                 if (i > len)
 185                         i = len;
 186                 memcpy(ctx->buffer + ctx->buflen, buf, i);
 187                 len -= i;
 188                 ctx->buflen += i;
 189                 buf += i;
 190
 191                 // When buffer fills up, process it.
 192
 193                 if (ctx->buflen == 64) {
 194                         md5_hash_block(ctx->buffer, ctx);
 195                         ctx->buflen = 0;
 196                 }
 197         }
 198 }
 199
 200 /* Process the remaining bytes in the buffer and put result from CTX
 201  * in first 16 bytes following RESBUF.  The result is always in little
 202  * endian byte order, so that a byte-wise output yields to the wanted
 203  * ASCII representation of the message digest.
 204  *
 205  * IMPORTANT: On some systems it is required that RESBUF is correctly
 206  * aligned for a 32 bits value.
 207  */
 208 void md5_end(void *resbuf, md5_ctx_t *ctx)
 209 {
 210         char *buf = ctx->buffer;
 211         int i;
 212
 213         /* Pad data to block size.  */
 214
 215         buf[ctx->buflen++] = 0x80;
 216         memset(buf + ctx->buflen, 0, 128 - ctx->buflen);
 217
 218         /* Put the 64-bit file length in *bits* at the end of the buffer.  */
 219         ctx->total <<= 3;
 220         if (ctx->buflen > 56)
 221                 buf += 64;
 222
 223         for (i = 0; i < 8; i++)
 224                 buf[56 + i] = ctx->total >> (i*8);
 225
 226         /* Process last bytes.  */
 227         if (buf != ctx->buffer)
 228                 md5_hash_block(ctx->buffer, ctx);
 229         md5_hash_block(buf, ctx);
 230
 231         /* Put result from CTX in first 16 bytes following RESBUF.  The result is
 232          * always in little endian byte order, so that a byte-wise output yields
 233          * to the wanted ASCII representation of the message digest.
 234          *
 235          * IMPORTANT: On some systems it is required that RESBUF is correctly
 236          * aligned for a 32 bits value.
 237          */
 238         ((uint32_t *) resbuf)[0] = SWAP_LE32(ctx->A);
 239         ((uint32_t *) resbuf)[1] = SWAP_LE32(ctx->B);
 240         ((uint32_t *) resbuf)[2] = SWAP_LE32(ctx->C);
 241         ((uint32_t *) resbuf)[3] = SWAP_LE32(ctx->D);
 242 }