1 /* 2 * TLS PRF (SHA1 + MD5) 3 * Copyright (c) 2003-2005, Jouni Malinen <j (at) 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 "sha1.h" 19 #include "md5.h" 20 #include "crypto.h" 21 22 23 /** 24 * tls_prf - Pseudo-Random Function for TLS (TLS-PRF, RFC 2246) 25 * @secret: Key for PRF 26 * @secret_len: Length of the key in bytes 27 * @label: A unique label for each purpose of the PRF 28 * @seed: Seed value to bind into the key 29 * @seed_len: Length of the seed 30 * @out: Buffer for the generated pseudo-random key 31 * @outlen: Number of bytes of key to generate 32 * Returns: 0 on success, -1 on failure. 33 * 34 * This function is used to derive new, cryptographically separate keys from a 35 * given key in TLS. This PRF is defined in RFC 2246, Chapter 5. 36 */ 37 int tls_prf(const u8 *secret, size_t secret_len, const char *label, 38 const u8 *seed, size_t seed_len, u8 *out, size_t outlen) 39 { 40 size_t L_S1, L_S2, i; 41 const u8 *S1, *S2; 42 u8 A_MD5[MD5_MAC_LEN], A_SHA1[SHA1_MAC_LEN]; 43 u8 P_MD5[MD5_MAC_LEN], P_SHA1[SHA1_MAC_LEN]; 44 int MD5_pos, SHA1_pos; 45 const u8 *MD5_addr[3]; 46 size_t MD5_len[3]; 47 const unsigned char *SHA1_addr[3]; 48 size_t SHA1_len[3]; 49 50 if (secret_len & 1) 51 return -1; 52 53 MD5_addr[0] = A_MD5; 54 MD5_len[0] = MD5_MAC_LEN; 55 MD5_addr[1] = (unsigned char *) label; 56 MD5_len[1] = os_strlen(label); 57 MD5_addr[2] = seed; 58 MD5_len[2] = seed_len; 59 60 SHA1_addr[0] = A_SHA1; 61 SHA1_len[0] = SHA1_MAC_LEN; 62 SHA1_addr[1] = (unsigned char *) label; 63 SHA1_len[1] = os_strlen(label); 64 SHA1_addr[2] = seed; 65 SHA1_len[2] = seed_len; 66 67 /* RFC 2246, Chapter 5 68 * A(0) = seed, A(i) = HMAC(secret, A(i-1)) 69 * P_hash = HMAC(secret, A(1) + seed) + HMAC(secret, A(2) + seed) + .. 70 * PRF = P_MD5(S1, label + seed) XOR P_SHA-1(S2, label + seed) 71 */ 72 73 L_S1 = L_S2 = (secret_len + 1) / 2; 74 S1 = secret; 75 S2 = secret + L_S1; 76 if (secret_len & 1) { 77 /* The last byte of S1 will be shared with S2 */ 78 S2--; 79 } 80 81 hmac_md5_vector_non_fips_allow(S1, L_S1, 2, &MD5_addr[1], &MD5_len[1], 82 A_MD5); 83 hmac_sha1_vector(S2, L_S2, 2, &SHA1_addr[1], &SHA1_len[1], A_SHA1); 84 85 MD5_pos = MD5_MAC_LEN; 86 SHA1_pos = SHA1_MAC_LEN; 87 for (i = 0; i < outlen; i++) { 88 if (MD5_pos == MD5_MAC_LEN) { 89 hmac_md5_vector_non_fips_allow(S1, L_S1, 3, MD5_addr, 90 MD5_len, P_MD5); 91 MD5_pos = 0; 92 hmac_md5_non_fips_allow(S1, L_S1, A_MD5, MD5_MAC_LEN, 93 A_MD5); 94 } 95 if (SHA1_pos == SHA1_MAC_LEN) { 96 hmac_sha1_vector(S2, L_S2, 3, SHA1_addr, SHA1_len, 97 P_SHA1); 98 SHA1_pos = 0; 99 hmac_sha1(S2, L_S2, A_SHA1, SHA1_MAC_LEN, A_SHA1); 100 } 101 102 out[i] = P_MD5[MD5_pos] ^ P_SHA1[SHA1_pos]; 103 104 MD5_pos++; 105 SHA1_pos++; 106 } 107 108 return 0; 109 } 110
