1 /* 2 * SHA1 T-PRF for EAP-FAST 3 * Copyright (c) 2003-2005, Jouni Malinen <j (at) 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 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 unsigned char counter = 0; 33 size_t pos, plen; 34 u8 hash[SHA1_MAC_LEN]; 35 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 addr[0] = hash; 41 len[0] = 0; 42 addr[1] = (unsigned char *) label; 43 len[1] = label_len + 1; 44 addr[2] = seed; 45 len[2] = seed_len; 46 addr[3] = output_len; 47 len[3] = 2; 48 addr[4] = &counter; 49 len[4] = 1; 50 51 output_len[0] = (buf_len >> 8) & 0xff; 52 output_len[1] = buf_len & 0xff; 53 pos = 0; 54 while (pos < buf_len) { 55 counter++; 56 plen = buf_len - pos; 57 if (hmac_sha1_vector(key, key_len, 5, addr, len, hash)) 58 return -1; 59 if (plen >= SHA1_MAC_LEN) { 60 os_memcpy(&buf[pos], hash, SHA1_MAC_LEN); 61 pos += SHA1_MAC_LEN; 62 } else { 63 os_memcpy(&buf[pos], hash, plen); 64 break; 65 } 66 len[0] = SHA1_MAC_LEN; 67 } 68 69 return 0; 70 } 71
