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/*
* SHA-256 hash implementation and interface functions
* Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Alternatively, this software may be distributed under the terms of BSD
* license.
*
* See README and COPYING for more details.
*/
#include "includes.h"
#include "common.h"
#include "sha256.h"
#include "crypto.h"
/**
* hmac_sha256_vector - HMAC-SHA256 over data vector (RFC 2104)
* @key: Key for HMAC operations
* @key_len: Length of the key in bytes
* @num_elem: Number of elements in the data vector
* @addr: Pointers to the data areas
* @len: Lengths of the data blocks
* @mac: Buffer for the hash (32 bytes)
*/
void hmac_sha256_vector(const u8 *key, size_t key_len, size_t num_elem,
const u8 *addr[], const size_t *len, u8 *mac)
{
unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */
unsigned char tk[32];
const u8 *_addr[6];
size_t _len[6], i;
if (num_elem > 5) {
/*
* Fixed limit on the number of fragments to avoid having to
* allocate memory (which could fail).
*/
return;
}
/* if key is longer than 64 bytes reset it to key = SHA256(key) */
if (key_len > 64) {
sha256_vector(1, &key, &key_len, tk);
key = tk;
key_len = 32;
}
/* the HMAC_SHA256 transform looks like:
*
* SHA256(K XOR opad, SHA256(K XOR ipad, text))
*
* where K is an n byte key
* ipad is the byte 0x36 repeated 64 times
* opad is the byte 0x5c repeated 64 times
* and text is the data being protected */
/* start out by storing key in ipad */
os_memset(k_pad, 0, sizeof(k_pad));
os_memcpy(k_pad, key, key_len);
/* XOR key with ipad values */
for (i = 0; i < 64; i++)
k_pad[i] ^= 0x36;
/* perform inner SHA256 */
_addr[0] = k_pad;
_len[0] = 64;
for (i = 0; i < num_elem; i++) {
_addr[i + 1] = addr[i];
_len[i + 1] = len[i];
}
sha256_vector(1 + num_elem, _addr, _len, mac);
os_memset(k_pad, 0, sizeof(k_pad));
os_memcpy(k_pad, key, key_len);
/* XOR key with opad values */
for (i = 0; i < 64; i++)
k_pad[i] ^= 0x5c;
/* perform outer SHA256 */
_addr[0] = k_pad;
_len[0] = 64;
_addr[1] = mac;
_len[1] = SHA256_MAC_LEN;
sha256_vector(2, _addr, _len, mac);
}
/**
* hmac_sha256 - HMAC-SHA256 over data buffer (RFC 2104)
* @key: Key for HMAC operations
* @key_len: Length of the key in bytes
* @data: Pointers to the data area
* @data_len: Length of the data area
* @mac: Buffer for the hash (20 bytes)
*/
void hmac_sha256(const u8 *key, size_t key_len, const u8 *data,
size_t data_len, u8 *mac)
{
hmac_sha256_vector(key, key_len, 1, &data, &data_len, mac);
}
/**
* sha256_prf - SHA256-based Pseudo-Random Function (IEEE 802.11r, 8.5.1.5.2)
* @key: Key for PRF
* @key_len: Length of the key in bytes
* @label: A unique label for each purpose of the PRF
* @data: Extra data to bind into the key
* @data_len: Length of the data
* @buf: Buffer for the generated pseudo-random key
* @buf_len: Number of bytes of key to generate
*
* This function is used to derive new, cryptographically separate keys from a
* given key.
*/
void sha256_prf(const u8 *key, size_t key_len, const char *label,
const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
{
u16 counter = 1;
size_t pos, plen;
u8 hash[SHA256_MAC_LEN];
const u8 *addr[4];
size_t len[4];
u8 counter_le[2], length_le[2];
addr[0] = counter_le;
len[0] = 2;
addr[1] = (u8 *) label;
len[1] = os_strlen(label);
addr[2] = data;
len[2] = data_len;
addr[3] = length_le;
len[3] = sizeof(length_le);
WPA_PUT_LE16(length_le, buf_len * 8);
pos = 0;
while (pos < buf_len) {
plen = buf_len - pos;
WPA_PUT_LE16(counter_le, counter);
if (plen >= SHA256_MAC_LEN) {
hmac_sha256_vector(key, key_len, 4, addr, len,
&buf[pos]);
pos += SHA256_MAC_LEN;
} else {
hmac_sha256_vector(key, key_len, 4, addr, len, hash);
os_memcpy(&buf[pos], hash, plen);
break;
}
counter++;
}
}
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