Line data    Source code

       1             : /*
       2             :  * SHA1 T-PRF for EAP-FAST
       3             :  * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
       4             :  *
       5             :  * This software may be distributed under the terms of the BSD license.
       6             :  * See README for more details.
       7             :  */
       8             : 
       9             : #include "includes.h"
      10             : 
      11             : #include "common.h"
      12             : #include "sha1.h"
      13             : #include "crypto.h"
      14             : 
      15             : /**
      16             :  * sha1_t_prf - EAP-FAST Pseudo-Random Function (T-PRF)
      17             :  * @key: Key for PRF
      18             :  * @key_len: Length of the key in bytes
      19             :  * @label: A unique label for each purpose of the PRF
      20             :  * @seed: Seed value to bind into the key
      21             :  * @seed_len: Length of the seed
      22             :  * @buf: Buffer for the generated pseudo-random key
      23             :  * @buf_len: Number of bytes of key to generate
      24             :  * Returns: 0 on success, -1 of failure
      25             :  *
      26             :  * This function is used to derive new, cryptographically separate keys from a
      27             :  * given key for EAP-FAST. T-PRF is defined in RFC 4851, Section 5.5.
      28             :  */
      29           3 : int sha1_t_prf(const u8 *key, size_t key_len, const char *label,
      30             :                const u8 *seed, size_t seed_len, u8 *buf, size_t buf_len)
      31             : {
      32           3 :         unsigned char counter = 0;
      33             :         size_t pos, plen;
      34             :         u8 hash[SHA1_MAC_LEN];
      35           3 :         size_t label_len = os_strlen(label);
      36             :         u8 output_len[2];
      37             :         const unsigned char *addr[5];
      38             :         size_t len[5];
      39             : 
      40           3 :         addr[0] = hash;
      41           3 :         len[0] = 0;
      42           3 :         addr[1] = (unsigned char *) label;
      43           3 :         len[1] = label_len + 1;
      44           3 :         addr[2] = seed;
      45           3 :         len[2] = seed_len;
      46           3 :         addr[3] = output_len;
      47           3 :         len[3] = 2;
      48           3 :         addr[4] = &counter;
      49           3 :         len[4] = 1;
      50             : 
      51           3 :         output_len[0] = (buf_len >> 8) & 0xff;
      52           3 :         output_len[1] = buf_len & 0xff;
      53           3 :         pos = 0;
      54          15 :         while (pos < buf_len) {
      55          10 :                 counter++;
      56          10 :                 plen = buf_len - pos;
      57          10 :                 if (hmac_sha1_vector(key, key_len, 5, addr, len, hash))
      58           0 :                         return -1;
      59          10 :                 if (plen >= SHA1_MAC_LEN) {
      60           9 :                         os_memcpy(&buf[pos], hash, SHA1_MAC_LEN);
      61           9 :                         pos += SHA1_MAC_LEN;
      62             :                 } else {
      63           1 :                         os_memcpy(&buf[pos], hash, plen);
      64           1 :                         break;
      65             :                 }
      66           9 :                 len[0] = SHA1_MAC_LEN;
      67             :         }
      68             : 
      69           3 :         return 0;
      70             : }