src/crypto/sha1-tlsprf.c

   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 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         if (secret_len & 1)
  44                 return -1;
  45
  46         MD5_addr[0] = A_MD5;
  47         MD5_len[0] = MD5_MAC_LEN;
  48         MD5_addr[1] = (unsigned char *) label;
  49         MD5_len[1] = os_strlen(label);
  50         MD5_addr[2] = seed;
  51         MD5_len[2] = seed_len;
  52
  53         SHA1_addr[0] = A_SHA1;
  54         SHA1_len[0] = SHA1_MAC_LEN;
  55         SHA1_addr[1] = (unsigned char *) label;
  56         SHA1_len[1] = os_strlen(label);
  57         SHA1_addr[2] = seed;
  58         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         L_S1 = L_S2 = (secret_len + 1) / 2;
  67         S1 = secret;
  68         S2 = secret + L_S1;
  69         if (secret_len & 1) {
  70                 /* The last byte of S1 will be shared with S2 */
  71                 S2--;
  72         }
  73
  74         hmac_md5_vector(S1, L_S1, 2, &MD5_addr[1], &MD5_len[1], A_MD5);
  75         hmac_sha1_vector(S2, L_S2, 2, &SHA1_addr[1], &SHA1_len[1], A_SHA1);
  76
  77         MD5_pos = MD5_MAC_LEN;
  78         SHA1_pos = SHA1_MAC_LEN;
  79         for (i = 0; i < outlen; i++) {
  80                 if (MD5_pos == MD5_MAC_LEN) {
  81                         hmac_md5_vector(S1, L_S1, 3, MD5_addr, MD5_len, P_MD5);
  82                         MD5_pos = 0;
  83                         hmac_md5(S1, L_S1, A_MD5, MD5_MAC_LEN, A_MD5);
  84                 }
  85                 if (SHA1_pos == SHA1_MAC_LEN) {
  86                         hmac_sha1_vector(S2, L_S2, 3, SHA1_addr, SHA1_len,
  87                                          P_SHA1);
  88                         SHA1_pos = 0;
  89                         hmac_sha1(S2, L_S2, A_SHA1, SHA1_MAC_LEN, A_SHA1);
  90                 }
  91
  92                 out[i] = P_MD5[MD5_pos] ^ P_SHA1[SHA1_pos];
  93
  94                 MD5_pos++;
  95                 SHA1_pos++;
  96         }
  97
  98         os_memset(A_MD5, 0, MD5_MAC_LEN);
  99         os_memset(P_MD5, 0, MD5_MAC_LEN);
 100         os_memset(A_SHA1, 0, SHA1_MAC_LEN);
 101         os_memset(P_SHA1, 0, SHA1_MAC_LEN);
 102
 103         return 0;
 104 }