167 lines
5.9 KiB
C
167 lines
5.9 KiB
C
/* These are the four functions used in the four steps of the MD5 algorithm
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and defined in the RFC 1321. The first function is a little bit optimized
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(as found in Colin Plumbs public domain implementation). */
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/* #define FF(b, c, d) ((b & c) | (~b & d)) */
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#define FF(b, c, d) (d ^ (b & (c ^ d)))
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#define FG(b, c, d) FF (d, b, c)
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#define FH(b, c, d) (b ^ c ^ d)
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#define FI(b, c, d) (c ^ (b | ~d))
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/* Process LEN bytes of BUFFER, accumulating context into CTX.
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It is assumed that LEN % 64 == 0. */
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void
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__md5_process_block (const void *buffer, size_t len, struct md5_ctx *ctx)
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{
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md5_uint32 correct_words[16];
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const md5_uint32 *words = buffer;
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size_t nwords = len / sizeof (md5_uint32);
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const md5_uint32 *endp = words + nwords;
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md5_uint32 A = ctx->A;
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md5_uint32 B = ctx->B;
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md5_uint32 C = ctx->C;
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md5_uint32 D = ctx->D;
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md5_uint32 lolen = len;
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/* First increment the byte count. RFC 1321 specifies the possible
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length of the file up to 2^64 bits. Here we only compute the
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number of bytes. Do a double word increment. */
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ctx->total[0] += lolen;
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ctx->total[1] += (len >> 31 >> 1) + (ctx->total[0] < lolen);
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/* Process all bytes in the buffer with 64 bytes in each round of
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the loop. */
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while (words < endp)
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{
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md5_uint32 *cwp = correct_words;
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md5_uint32 A_save = A;
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md5_uint32 B_save = B;
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md5_uint32 C_save = C;
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md5_uint32 D_save = D;
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/* First round: using the given function, the context and a constant
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the next context is computed. Because the algorithms processing
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unit is a 32-bit word and it is determined to work on words in
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little endian byte order we perhaps have to change the byte order
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before the computation. To reduce the work for the next steps
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we store the swapped words in the array CORRECT_WORDS. */
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#define OP(a, b, c, d, s, T) \
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do \
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{ \
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a += FF (b, c, d) + (*cwp++ = SWAP (*words)) + T; \
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++words; \
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CYCLIC (a, s); \
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a += b; \
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} \
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while (0)
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/* It is unfortunate that C does not provide an operator for
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cyclic rotation. Hope the C compiler is smart enough. */
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#define CYCLIC(w, s) (w = (w << s) | (w >> (32 - s)))
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/* Before we start, one word to the strange constants.
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They are defined in RFC 1321 as
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T[i] = (int) (4294967296.0 * fabs (sin (i))), i=1..64
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*/
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/* Round 1. */
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OP (A, B, C, D, 7, 0xd76aa478);
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OP (D, A, B, C, 12, 0xe8c7b756);
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OP (C, D, A, B, 17, 0x242070db);
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OP (B, C, D, A, 22, 0xc1bdceee);
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OP (A, B, C, D, 7, 0xf57c0faf);
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OP (D, A, B, C, 12, 0x4787c62a);
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OP (C, D, A, B, 17, 0xa8304613);
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OP (B, C, D, A, 22, 0xfd469501);
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OP (A, B, C, D, 7, 0x698098d8);
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OP (D, A, B, C, 12, 0x8b44f7af);
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OP (C, D, A, B, 17, 0xffff5bb1);
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OP (B, C, D, A, 22, 0x895cd7be);
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OP (A, B, C, D, 7, 0x6b901122);
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OP (D, A, B, C, 12, 0xfd987193);
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OP (C, D, A, B, 17, 0xa679438e);
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OP (B, C, D, A, 22, 0x49b40821);
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/* For the second to fourth round we have the possibly swapped words
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in CORRECT_WORDS. Redefine the macro to take an additional first
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argument specifying the function to use. */
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#undef OP
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#define OP(f, a, b, c, d, k, s, T) \
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do \
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{ \
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a += f (b, c, d) + correct_words[k] + T; \
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CYCLIC (a, s); \
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a += b; \
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} \
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while (0)
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/* Round 2. */
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OP (FG, A, B, C, D, 1, 5, 0xf61e2562);
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OP (FG, D, A, B, C, 6, 9, 0xc040b340);
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OP (FG, C, D, A, B, 11, 14, 0x265e5a51);
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OP (FG, B, C, D, A, 0, 20, 0xe9b6c7aa);
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OP (FG, A, B, C, D, 5, 5, 0xd62f105d);
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OP (FG, D, A, B, C, 10, 9, 0x02441453);
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OP (FG, C, D, A, B, 15, 14, 0xd8a1e681);
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OP (FG, B, C, D, A, 4, 20, 0xe7d3fbc8);
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OP (FG, A, B, C, D, 9, 5, 0x21e1cde6);
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OP (FG, D, A, B, C, 14, 9, 0xc33707d6);
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OP (FG, C, D, A, B, 3, 14, 0xf4d50d87);
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OP (FG, B, C, D, A, 8, 20, 0x455a14ed);
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OP (FG, A, B, C, D, 13, 5, 0xa9e3e905);
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OP (FG, D, A, B, C, 2, 9, 0xfcefa3f8);
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OP (FG, C, D, A, B, 7, 14, 0x676f02d9);
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OP (FG, B, C, D, A, 12, 20, 0x8d2a4c8a);
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/* Round 3. */
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OP (FH, A, B, C, D, 5, 4, 0xfffa3942);
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OP (FH, D, A, B, C, 8, 11, 0x8771f681);
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OP (FH, C, D, A, B, 11, 16, 0x6d9d6122);
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OP (FH, B, C, D, A, 14, 23, 0xfde5380c);
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OP (FH, A, B, C, D, 1, 4, 0xa4beea44);
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OP (FH, D, A, B, C, 4, 11, 0x4bdecfa9);
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OP (FH, C, D, A, B, 7, 16, 0xf6bb4b60);
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OP (FH, B, C, D, A, 10, 23, 0xbebfbc70);
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OP (FH, A, B, C, D, 13, 4, 0x289b7ec6);
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OP (FH, D, A, B, C, 0, 11, 0xeaa127fa);
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OP (FH, C, D, A, B, 3, 16, 0xd4ef3085);
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OP (FH, B, C, D, A, 6, 23, 0x04881d05);
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OP (FH, A, B, C, D, 9, 4, 0xd9d4d039);
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OP (FH, D, A, B, C, 12, 11, 0xe6db99e5);
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OP (FH, C, D, A, B, 15, 16, 0x1fa27cf8);
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OP (FH, B, C, D, A, 2, 23, 0xc4ac5665);
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/* Round 4. */
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OP (FI, A, B, C, D, 0, 6, 0xf4292244);
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OP (FI, D, A, B, C, 7, 10, 0x432aff97);
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OP (FI, C, D, A, B, 14, 15, 0xab9423a7);
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OP (FI, B, C, D, A, 5, 21, 0xfc93a039);
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OP (FI, A, B, C, D, 12, 6, 0x655b59c3);
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OP (FI, D, A, B, C, 3, 10, 0x8f0ccc92);
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OP (FI, C, D, A, B, 10, 15, 0xffeff47d);
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OP (FI, B, C, D, A, 1, 21, 0x85845dd1);
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OP (FI, A, B, C, D, 8, 6, 0x6fa87e4f);
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OP (FI, D, A, B, C, 15, 10, 0xfe2ce6e0);
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OP (FI, C, D, A, B, 6, 15, 0xa3014314);
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OP (FI, B, C, D, A, 13, 21, 0x4e0811a1);
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OP (FI, A, B, C, D, 4, 6, 0xf7537e82);
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OP (FI, D, A, B, C, 11, 10, 0xbd3af235);
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OP (FI, C, D, A, B, 2, 15, 0x2ad7d2bb);
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OP (FI, B, C, D, A, 9, 21, 0xeb86d391);
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/* Add the starting values of the context. */
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A += A_save;
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B += B_save;
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C += C_save;
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D += D_save;
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}
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/* Put checksum in context given as argument. */
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ctx->A = A;
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ctx->B = B;
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ctx->C = C;
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ctx->D = D;
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}
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