src/crypto/md5.c

   1 /*
   2  * MD5 hash implementation and interface functions
   3  * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Alternatively, this software may be distributed under the terms of BSD
  10  * license.
  11  *
  12  * See README and COPYING for more details.
  13  */
  14
  15 #include "includes.h"
  16
  17 #include "common.h"
  18 #include "md5.h"
  19 #include "crypto.h"
  20
  21
  22 /**
  23  * hmac_md5_vector - HMAC-MD5 over data vector (RFC 2104)
  24  * @key: Key for HMAC operations
  25  * @key_len: Length of the key in bytes
  26  * @num_elem: Number of elements in the data vector
  27  * @addr: Pointers to the data areas
  28  * @len: Lengths of the data blocks
  29  * @mac: Buffer for the hash (16 bytes)
  30  */
  31 void hmac_md5_vector(const u8 *key, size_t key_len, size_t num_elem,
  32                      const u8 *addr[], const size_t *len, u8 *mac)
  33 {
  34         u8 k_pad[64]; /* padding - key XORd with ipad/opad */
  35         u8 tk[16];
  36         const u8 *_addr[6];
  37         size_t i, _len[6];
  38
  39         if (num_elem > 5) {
  40                 /*
  41                  * Fixed limit on the number of fragments to avoid having to
  42                  * allocate memory (which could fail).
  43                  */
  44                 return;
  45         }
  46
  47         /* if key is longer than 64 bytes reset it to key = MD5(key) */
  48         if (key_len > 64) {
  49                 md5_vector(1, &key, &key_len, tk);
  50                 key = tk;
  51                 key_len = 16;
  52         }
  53
  54         /* the HMAC_MD5 transform looks like:
  55          *
  56          * MD5(K XOR opad, MD5(K XOR ipad, text))
  57          *
  58          * where K is an n byte key
  59          * ipad is the byte 0x36 repeated 64 times
  60          * opad is the byte 0x5c repeated 64 times
  61          * and text is the data being protected */
  62
  63         /* start out by storing key in ipad */
  64         os_memset(k_pad, 0, sizeof(k_pad));
  65         os_memcpy(k_pad, key, key_len);
  66
  67         /* XOR key with ipad values */
  68         for (i = 0; i < 64; i++)
  69                 k_pad[i] ^= 0x36;
  70
  71         /* perform inner MD5 */
  72         _addr[0] = k_pad;
  73         _len[0] = 64;
  74         for (i = 0; i < num_elem; i++) {
  75                 _addr[i + 1] = addr[i];
  76                 _len[i + 1] = len[i];
  77         }
  78         md5_vector(1 + num_elem, _addr, _len, mac);
  79
  80         os_memset(k_pad, 0, sizeof(k_pad));
  81         os_memcpy(k_pad, key, key_len);
  82         /* XOR key with opad values */
  83         for (i = 0; i < 64; i++)
  84                 k_pad[i] ^= 0x5c;
  85
  86         /* perform outer MD5 */
  87         _addr[0] = k_pad;
  88         _len[0] = 64;
  89         _addr[1] = mac;
  90         _len[1] = MD5_MAC_LEN;
  91         md5_vector(2, _addr, _len, mac);
  92 }
  93
  94
  95 /**
  96  * hmac_md5 - HMAC-MD5 over data buffer (RFC 2104)
  97  * @key: Key for HMAC operations
  98  * @key_len: Length of the key in bytes
  99  * @data: Pointers to the data area
 100  * @data_len: Length of the data area
 101  * @mac: Buffer for the hash (16 bytes)
 102  */
 103 void hmac_md5(const u8 *key, size_t key_len, const u8 *data, size_t data_len,
 104               u8 *mac)
 105 {
 106         hmac_md5_vector(key, key_len, 1, &data, &data_len, mac);
 107 }