Line data    Source code

       1             : /*
       2             :  * TLS PRF (SHA1 + MD5)
       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 "md5.h"
      14             : 
      15             : 
      16             : /**
      17             :  * tls_prf_sha1_md5 - Pseudo-Random Function for TLS (TLS-PRF, RFC 2246)
      18             :  * @secret: Key for PRF
      19             :  * @secret_len: Length of the key in bytes
      20             :  * @label: A unique label for each purpose of the PRF
      21             :  * @seed: Seed value to bind into the key
      22             :  * @seed_len: Length of the seed
      23             :  * @out: Buffer for the generated pseudo-random key
      24             :  * @outlen: Number of bytes of key to generate
      25             :  * Returns: 0 on success, -1 on failure.
      26             :  *
      27             :  * This function is used to derive new, cryptographically separate keys from a
      28             :  * given key in TLS. This PRF is defined in RFC 2246, Chapter 5.
      29             :  */
      30          43 : int tls_prf_sha1_md5(const u8 *secret, size_t secret_len, const char *label,
      31             :                      const u8 *seed, size_t seed_len, u8 *out, size_t outlen)
      32             : {
      33             :         size_t L_S1, L_S2, i;
      34             :         const u8 *S1, *S2;
      35             :         u8 A_MD5[MD5_MAC_LEN], A_SHA1[SHA1_MAC_LEN];
      36             :         u8 P_MD5[MD5_MAC_LEN], P_SHA1[SHA1_MAC_LEN];
      37             :         int MD5_pos, SHA1_pos;
      38             :         const u8 *MD5_addr[3];
      39             :         size_t MD5_len[3];
      40             :         const unsigned char *SHA1_addr[3];
      41             :         size_t SHA1_len[3];
      42             : 
      43          43 :         if (secret_len & 1)
      44           0 :                 return -1;
      45             : 
      46          43 :         MD5_addr[0] = A_MD5;
      47          43 :         MD5_len[0] = MD5_MAC_LEN;
      48          43 :         MD5_addr[1] = (unsigned char *) label;
      49          43 :         MD5_len[1] = os_strlen(label);
      50          43 :         MD5_addr[2] = seed;
      51          43 :         MD5_len[2] = seed_len;
      52             : 
      53          43 :         SHA1_addr[0] = A_SHA1;
      54          43 :         SHA1_len[0] = SHA1_MAC_LEN;
      55          43 :         SHA1_addr[1] = (unsigned char *) label;
      56          43 :         SHA1_len[1] = os_strlen(label);
      57          43 :         SHA1_addr[2] = seed;
      58          43 :         SHA1_len[2] = seed_len;
      59             : 
      60             :         /* RFC 2246, Chapter 5
      61             :          * A(0) = seed, A(i) = HMAC(secret, A(i-1))
      62             :          * P_hash = HMAC(secret, A(1) + seed) + HMAC(secret, A(2) + seed) + ..
      63             :          * PRF = P_MD5(S1, label + seed) XOR P_SHA-1(S2, label + seed)
      64             :          */
      65             : 
      66          43 :         L_S1 = L_S2 = (secret_len + 1) / 2;
      67          43 :         S1 = secret;
      68          43 :         S2 = secret + L_S1;
      69          43 :         if (secret_len & 1) {
      70             :                 /* The last byte of S1 will be shared with S2 */
      71           0 :                 S2--;
      72             :         }
      73             : 
      74          43 :         hmac_md5_vector(S1, L_S1, 2, &MD5_addr[1], &MD5_len[1], A_MD5);
      75          43 :         hmac_sha1_vector(S2, L_S2, 2, &SHA1_addr[1], &SHA1_len[1], A_SHA1);
      76             : 
      77          43 :         MD5_pos = MD5_MAC_LEN;
      78          43 :         SHA1_pos = SHA1_MAC_LEN;
      79        6459 :         for (i = 0; i < outlen; i++) {
      80        6416 :                 if (MD5_pos == MD5_MAC_LEN) {
      81         401 :                         hmac_md5_vector(S1, L_S1, 3, MD5_addr, MD5_len, P_MD5);
      82         401 :                         MD5_pos = 0;
      83         401 :                         hmac_md5(S1, L_S1, A_MD5, MD5_MAC_LEN, A_MD5);
      84             :                 }
      85        6416 :                 if (SHA1_pos == SHA1_MAC_LEN) {
      86         350 :                         hmac_sha1_vector(S2, L_S2, 3, SHA1_addr, SHA1_len,
      87             :                                          P_SHA1);
      88         350 :                         SHA1_pos = 0;
      89         350 :                         hmac_sha1(S2, L_S2, A_SHA1, SHA1_MAC_LEN, A_SHA1);
      90             :                 }
      91             : 
      92        6416 :                 out[i] = P_MD5[MD5_pos] ^ P_SHA1[SHA1_pos];
      93             : 
      94        6416 :                 MD5_pos++;
      95        6416 :                 SHA1_pos++;
      96             :         }
      97             : 
      98          43 :         return 0;
      99             : }