1 /* 2 * SHA-256 hash implementation and interface functions 3 * Copyright (c) 2003-2007, 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 "sha256.h" 13 #include "crypto.h" 14 15 16 /** 17 * hmac_sha256_vector - HMAC-SHA256 over data vector (RFC 2104) 18 * @key: Key for HMAC operations 19 * @key_len: Length of the key in bytes 20 * @num_elem: Number of elements in the data vector 21 * @addr: Pointers to the data areas 22 * @len: Lengths of the data blocks 23 * @mac: Buffer for the hash (32 bytes) 24 */ 25 void hmac_sha256_vector(const u8 *key, size_t key_len, size_t num_elem, 26 const u8 *addr[], const size_t *len, u8 *mac) 27 { 28 unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */ 29 unsigned char tk[32]; 30 const u8 *_addr[6]; 31 size_t _len[6], i; 32 33 if (num_elem > 5) { 34 /* 35 * Fixed limit on the number of fragments to avoid having to 36 * allocate memory (which could fail). 37 */ 38 return; 39 } 40 41 /* if key is longer than 64 bytes reset it to key = SHA256(key) */ 42 if (key_len > 64) { 43 sha256_vector(1, &key, &key_len, tk); 44 key = tk; 45 key_len = 32; 46 } 47 48 /* the HMAC_SHA256 transform looks like: 49 * 50 * SHA256(K XOR opad, SHA256(K XOR ipad, text)) 51 * 52 * where K is an n byte key 53 * ipad is the byte 0x36 repeated 64 times 54 * opad is the byte 0x5c repeated 64 times 55 * and text is the data being protected */ 56 57 /* start out by storing key in ipad */ 58 os_memset(k_pad, 0, sizeof(k_pad)); 59 os_memcpy(k_pad, key, key_len); 60 /* XOR key with ipad values */ 61 for (i = 0; i < 64; i++) 62 k_pad[i] ^= 0x36; 63 64 /* perform inner SHA256 */ 65 _addr[0] = k_pad; 66 _len[0] = 64; 67 for (i = 0; i < num_elem; i++) { 68 _addr[i + 1] = addr[i]; 69 _len[i + 1] = len[i]; 70 } 71 sha256_vector(1 + num_elem, _addr, _len, mac); 72 73 os_memset(k_pad, 0, sizeof(k_pad)); 74 os_memcpy(k_pad, key, key_len); 75 /* XOR key with opad values */ 76 for (i = 0; i < 64; i++) 77 k_pad[i] ^= 0x5c; 78 79 /* perform outer SHA256 */ 80 _addr[0] = k_pad; 81 _len[0] = 64; 82 _addr[1] = mac; 83 _len[1] = SHA256_MAC_LEN; 84 sha256_vector(2, _addr, _len, mac); 85 } 86 87 88 /** 89 * hmac_sha256 - HMAC-SHA256 over data buffer (RFC 2104) 90 * @key: Key for HMAC operations 91 * @key_len: Length of the key in bytes 92 * @data: Pointers to the data area 93 * @data_len: Length of the data area 94 * @mac: Buffer for the hash (20 bytes) 95 */ 96 void hmac_sha256(const u8 *key, size_t key_len, const u8 *data, 97 size_t data_len, u8 *mac) 98 { 99 hmac_sha256_vector(key, key_len, 1, &data, &data_len, mac); 100 } 101 102 103 /** 104 * sha256_prf - SHA256-based Pseudo-Random Function (IEEE 802.11r, 8.5.1.5.2) 105 * @key: Key for PRF 106 * @key_len: Length of the key in bytes 107 * @label: A unique label for each purpose of the PRF 108 * @data: Extra data to bind into the key 109 * @data_len: Length of the data 110 * @buf: Buffer for the generated pseudo-random key 111 * @buf_len: Number of bytes of key to generate 112 * 113 * This function is used to derive new, cryptographically separate keys from a 114 * given key. 115 */ 116 void sha256_prf(const u8 *key, size_t key_len, const char *label, 117 const u8 *data, size_t data_len, u8 *buf, size_t buf_len) 118 { 119 u16 counter = 1; 120 size_t pos, plen; 121 u8 hash[SHA256_MAC_LEN]; 122 const u8 *addr[4]; 123 size_t len[4]; 124 u8 counter_le[2], length_le[2]; 125 126 addr[0] = counter_le; 127 len[0] = 2; 128 addr[1] = (u8 *) label; 129 len[1] = os_strlen(label); 130 addr[2] = data; 131 len[2] = data_len; 132 addr[3] = length_le; 133 len[3] = sizeof(length_le); 134 135 WPA_PUT_LE16(length_le, buf_len * 8); 136 pos = 0; 137 while (pos < buf_len) { 138 plen = buf_len - pos; 139 WPA_PUT_LE16(counter_le, counter); 140 if (plen >= SHA256_MAC_LEN) { 141 hmac_sha256_vector(key, key_len, 4, addr, len, 142 &buf[pos]); 143 pos += SHA256_MAC_LEN; 144 } else { 145 hmac_sha256_vector(key, key_len, 4, addr, len, hash); 146 os_memcpy(&buf[pos], hash, plen); 147 break; 148 } 149 counter++; 150 } 151 } 152
