/* * Copyright (C) 2003-2005 by Christopher R. Hertel * 2015 Freie Universität Berlin * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library 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 * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ /** * @ingroup sys_hashes * @{ * * @file * @brief Implements the MD5 hash algorithm, as described in RFC 1321 * * @author Christopher R. Hertel * @author Hauke Petersen * * @} */ #include "hashes/md5.h" /** * @brief In round one, the values of k (which are used to index * particular four-byte sequences in the input) are simply * sequential. In later rounds, however, they are a bit more * varied. Rather than calculate the values of k (which may * or may not be possible--I haven't though about it) the * values are stored in this array. */ static const uint8_t K[3][16] = { /* Round 1: skipped (since it is simply sequential). */ { 1, 6, 11, 0, 5, 10, 15, 4, 9, 14, 3, 8, 13, 2, 7, 12 }, /* R2 */ { 5, 8, 11, 14, 1, 4, 7, 10, 13, 0, 3, 6, 9, 12, 15, 2 }, /* R3 */ { 0, 7, 14, 5, 12, 3, 10, 1, 8, 15, 6, 13, 4, 11, 2, 9 } /* R4 */ }; /** * @brief In each round there is a left rotate operation performed as * part of the 16 permutations. The number of bits varies in * a repeating patter. This array keeps track of the patterns * used in each round. */ static const uint8_t S[4][4] = { { 7, 12, 17, 22 }, /* Round 1 */ { 5, 9, 14, 20 }, /* Round 2 */ { 4, 11, 16, 23 }, /* Round 3 */ { 6, 10, 15, 21 } /* Round 4 */ }; /** * @brief There are four rounds of 16 permutations for a total of 64. * In each of these 64 permutation operations, a different * constant value is added to the mix. The constants are * based on the sine function...read RFC 1321 for more detail. * In any case, the correct constants are stored in the T[][] * array. They're divided up into four groups of 16. */ static const uint32_t T[4][16] = { { 0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, /* Round 1 */ 0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, 0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be, 0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821 }, { 0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa, /* Round 2 */ 0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8, 0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, 0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a }, { 0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c, /* Round 3 */ 0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, 0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05, 0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665 }, { 0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, /* Round 4 */ 0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1, 0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1, 0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391 }, }; /** * @brief md5F(), md5G(), md5H(), and md5I() are described in RFC 1321 * * All of these operations are bitwise, and so not impacted by endian-ness. * @{ */ #define md5F( X, Y, Z ) (((X) &(Y)) | ((~(X)) & (Z))) #define md5G( X, Y, Z ) (((X) &(Z)) | ((Y) &(~(Z)))) #define md5H( X, Y, Z ) ((X) ^ (Y) ^ (Z)) #define md5I( X, Y, Z ) ((Y) ^ ((X) | (~(Z)))) /** @} */ /** * @brief Extract one byte from a 32-bit word * * A value of 0 for indicates the lowest order byte, while 3 indicates * the highest order byte. */ #define GETBYTE(L, idx) ((uint8_t)((L >> (((idx) & 0x03) << 3)) & 0xFF)) /** * @brief Permute the ABCD "registers" using the 64-byte as a driver * * The MD5 algorithm operates on a set of four longwords stored (conceptually) * in four "registers". It is easy to imagine a simple MD4/5 chip that would * operate this way. In any case, the mangling of the contents of those * registers is driven by the input message. The message is chopped and finally * padded into 64-byte chunks and each chunk is used to manipulate the contents * of the registers. * * The MD5 Algorithm calls for padding the input to ensure that it is a multiple * of 64 bytes in length. The last 16 bytes of the padding space are used to * store the message length (the length of the original message, before padding, * expressed in terms of bits). If there is not enough room for 16 bytes worth * of bitcount (eg., if the original message was 122 bytes long) then the block * is padded to the end with zeros and passed to this function. Then *another* * block is filled with zeros except for the last 16 bytes which contain the * length. * * Oh... and the algorithm requires that there be at least one padding byte. The * first padding byte has a value of 0x80, and any others are 0x00. * * @param[in|out] abcd Pointer to an array of four unsigned longwords * @param[in] block Array of bytes, must be 64 bytes in size */ static void permute(uint32_t abcd[4], const uint8_t block[64] ) { uint8_t s; uint32_t a, b, c, d; uint32_t keep_abcd[4]; uint32_t x[16]; /* Store the current ABCD values for later re-use */ for (int i = 0; i < 4; i++) { keep_abcd[i] = abcd[i]; } /* Convert the input block into an array of unsigned longs, taking care * to read the block in Little Endian order (the algorithm assumes this). * The uint32_t values are then handled in host order. */ for (int i = 0, j = 0; i < 16; i++) { x[i] = (uint32_t)block[j++]; x[i] |= ((uint32_t)block[j++] << 8); x[i] |= ((uint32_t)block[j++] << 16); x[i] |= ((uint32_t)block[j++] << 24); } /* This loop performs the four rounds of permutations. * The rounds are each very similar. The differences are in three areas: * - The function (F, G, H, or I) used to perform bitwise permutations * on the registers, * - The order in which values from X[] are chosen. * - Changes to the number of bits by which the registers are rotated. * This implementation uses a switch statement to deal with some of the * differences between rounds. Other differences are handled by storing * values in arrays and using the round number to select the correct set * of values. * * (My implementation appears to be a poor compromise between speed, size, * and clarity. Ugh. [crh]) */ for (int round = 0; round < 4; round++) { for (int i = 0; i < 16; i++) { /* handles the rotation of ABCD */ int j = (4 - (i % 4)) & 0x3; /* is the bit shift for this iteration */ s = S[round][i % 4]; /* Copy the b,c,d values per ABCD rotation. This isn't really * necessary, it just looks clean & will hopefully be optimized * away. */ b = abcd[(j + 1) & 0x3]; c = abcd[(j + 2) & 0x3]; d = abcd[(j + 3) & 0x3]; /* The actual perumation function. * This is broken out to minimize the code within the switch(). */ switch (round) { case 0: /* round 1 */ a = md5F( b, c, d ) + x[i]; break; case 1: /* round 2 */ a = md5G( b, c, d ) + x[ K[0][i] ]; break; case 2: /* round 3 */ a = md5H( b, c, d ) + x[ K[1][i] ]; break; default: /* round 4 */ a = md5I( b, c, d ) + x[ K[2][i] ]; break; } a = 0xFFFFFFFF & (abcd[j] + a + T[round][i]); abcd[j] = b + (0xFFFFFFFF & ((a << s) | (a >> (32 - s)))); } } /* Use the stored original A, B, C, D values to perform * one last convolution. */ for (int i = 0; i < 4; i++) { abcd[i] = (abcd[i] + keep_abcd[i]); } } void md5_init(md5_ctx_t *ctx) { ctx->len = 0; ctx->b_used = 0; /* The array ABCD[] contains the four 4-byte "registers" that are * manipulated to produce the MD5 digest. The input acts upon the registers, * not the other way 'round. The initial values are thosegiven in RFC 1321 * (pg. 4). Note, however, that RFC 1321 provides these values as bytes, not * as longwords, and the bytes are arranged in little-endian order as if * they were the bytes of (little endian) 32-bit ints. That's confusing as * all getout (to me, anyway). The values given here are provided as 32-bit * values in C language format, so they are endian-agnostic. */ ctx->abcd[0] = 0x67452301; ctx->abcd[1] = 0xefcdab89; ctx->abcd[2] = 0x98badcfe; ctx->abcd[3] = 0x10325476; } void md5_update(md5_ctx_t *ctx, const void *data, size_t len) { /* Add the new block's length to the total length. */ ctx->len += (uint32_t)len; /* Copy the new block's data into the context block. * Call the permute() function whenever the context block is full. */ for (size_t i = 0; i < len; i++) { const uint8_t *d = data; ctx->block[ctx->b_used] = d[i]; (ctx->b_used)++; if (64 == ctx->b_used) { permute(ctx->abcd, ctx->block); ctx->b_used = 0; } } } void md5_final(md5_ctx_t *ctx, void *digest) { uint32_t l; /* Add the required 0x80 padding initiator byte. * The md5_update() function always permutes and resets the context * block when it gets full, so we know that there must be at least one * free byte in the context block. */ ctx->block[ctx->b_used] = 0x80; (ctx->b_used)++; /* Zero out any remaining free bytes in the context block. */ for (int i = ctx->b_used; i < 64; i++) { ctx->block[i] = 0; } /* We need 8 bytes to store the length field. * If we don't have 8, call permute() and reset the context block. */ if (56 < ctx->b_used) { permute(ctx->abcd, ctx->block); for (int i = 0; i < 64; i++) { ctx->block[i] = 0; } } /* Add the total length and perform the final perumation. * Note: The 60'th byte is read from the *original* len> value * and shifted to the correct position. This neatly avoids * any MAXINT numeric overflow issues. */ l = ctx->len << 3; for (int i = 0; i < 4; i++) { ctx->block[56 + i] |= GETBYTE(l, i); } ctx->block[60] = ((GETBYTE(ctx->len, 3) & 0xE0) >> 5); /* See Above! */ permute(ctx->abcd, ctx->block); /* Now copy the result into the output buffer and we're done */ for (int i = 0; i < 4; i++) { uint8_t *d = digest; d[ 0 + i] = GETBYTE(ctx->abcd[0], i); d[ 4 + i] = GETBYTE(ctx->abcd[1], i); d[ 8 + i] = GETBYTE(ctx->abcd[2], i); d[12 + i] = GETBYTE(ctx->abcd[3], i); } } void md5(void *digest, const void *data, size_t len) { md5_ctx_t ctx; md5_init(&ctx); md5_update(&ctx, data, len); md5_final(&ctx, digest); }