1 /* 2 * SHA-256 hash implementation and interface functions 3 * Copyright (c) 2003-2007, 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 "sha256.h" 19 #include "crypto.h" 20 21 22 /** 23 * hmac_sha256_vector - HMAC-SHA256 over data vector (RFC 2104) 24 * @key: Key for HMAC operations 25 * @key_len: Length of the key in bytes 26 * @num_elem: Number of elements in the data vector 27 * @addr: Pointers to the data areas 28 * @len: Lengths of the data blocks 29 * @mac: Buffer for the hash (32 bytes) 30 */ 31 void hmac_sha256_vector(const u8 *key, size_t key_len, size_t num_elem, 32 const u8 *addr[], const size_t *len, u8 *mac) 33 { 34 unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */ 35 unsigned char tk[32]; 36 const u8 *_addr[6]; 37 size_t _len[6], i; 38 39 if (num_elem > 5) { 40 /* 41 * Fixed limit on the number of fragments to avoid having to 42 * allocate memory (which could fail). 43 */ 44 return; 45 } 46 47 /* if key is longer than 64 bytes reset it to key = SHA256(key) */ 48 if (key_len > 64) { 49 sha256_vector(1, &key, &key_len, tk); 50 key = tk; 51 key_len = 32; 52 } 53 54 /* the HMAC_SHA256 transform looks like: 55 * 56 * SHA256(K XOR opad, SHA256(K XOR ipad, text)) 57 * 58 * where K is an n byte key 59 * ipad is the byte 0x36 repeated 64 times 60 * opad is the byte 0x5c repeated 64 times 61 * and text is the data being protected */ 62 63 /* start out by storing key in ipad */ 64 os_memset(k_pad, 0, sizeof(k_pad)); 65 os_memcpy(k_pad, key, key_len); 66 /* XOR key with ipad values */ 67 for (i = 0; i < 64; i++) 68 k_pad[i] ^= 0x36; 69 70 /* perform inner SHA256 */ 71 _addr[0] = k_pad; 72 _len[0] = 64; 73 for (i = 0; i < num_elem; i++) { 74 _addr[i + 1] = addr[i]; 75 _len[i + 1] = len[i]; 76 } 77 sha256_vector(1 + num_elem, _addr, _len, mac); 78 79 os_memset(k_pad, 0, sizeof(k_pad)); 80 os_memcpy(k_pad, key, key_len); 81 /* XOR key with opad values */ 82 for (i = 0; i < 64; i++) 83 k_pad[i] ^= 0x5c; 84 85 /* perform outer SHA256 */ 86 _addr[0] = k_pad; 87 _len[0] = 64; 88 _addr[1] = mac; 89 _len[1] = SHA256_MAC_LEN; 90 sha256_vector(2, _addr, _len, mac); 91 } 92 93 94 /** 95 * hmac_sha256 - HMAC-SHA256 over data buffer (RFC 2104) 96 * @key: Key for HMAC operations 97 * @key_len: Length of the key in bytes 98 * @data: Pointers to the data area 99 * @data_len: Length of the data area 100 * @mac: Buffer for the hash (20 bytes) 101 */ 102 void hmac_sha256(const u8 *key, size_t key_len, const u8 *data, 103 size_t data_len, u8 *mac) 104 { 105 hmac_sha256_vector(key, key_len, 1, &data, &data_len, mac); 106 } 107 108 109 /** 110 * sha256_prf - SHA256-based Pseudo-Random Function (IEEE 802.11r, 8.5.1.5.2) 111 * @key: Key for PRF 112 * @key_len: Length of the key in bytes 113 * @label: A unique label for each purpose of the PRF 114 * @data: Extra data to bind into the key 115 * @data_len: Length of the data 116 * @buf: Buffer for the generated pseudo-random key 117 * @buf_len: Number of bytes of key to generate 118 * 119 * This function is used to derive new, cryptographically separate keys from a 120 * given key. 121 */ 122 void sha256_prf(const u8 *key, size_t key_len, const char *label, 123 const u8 *data, size_t data_len, u8 *buf, size_t buf_len) 124 { 125 u16 counter = 1; 126 size_t pos, plen; 127 u8 hash[SHA256_MAC_LEN]; 128 const u8 *addr[4]; 129 size_t len[4]; 130 u8 counter_le[2], length_le[2]; 131 132 addr[0] = counter_le; 133 len[0] = 2; 134 addr[1] = (u8 *) label; 135 len[1] = os_strlen(label); 136 addr[2] = data; 137 len[2] = data_len; 138 addr[3] = length_le; 139 len[3] = sizeof(length_le); 140 141 WPA_PUT_LE16(length_le, buf_len * 8); 142 pos = 0; 143 while (pos < buf_len) { 144 plen = buf_len - pos; 145 WPA_PUT_LE16(counter_le, counter); 146 if (plen >= SHA256_MAC_LEN) { 147 hmac_sha256_vector(key, key_len, 4, addr, len, 148 &buf[pos]); 149 pos += SHA256_MAC_LEN; 150 } else { 151 hmac_sha256_vector(key, key_len, 4, addr, len, hash); 152 os_memcpy(&buf[pos], hash, plen); 153 break; 154 } 155 counter++; 156 } 157 } 158
