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 return 0; 99 } 100