hostap/src/crypto/sha1-prf.c
Jouni Malinen 51f3427019 crypto: Clear temporary stack buffers after use
This reduces possibility of exposure of private keys should something
get access to stack memory.

Signed-off-by: Jouni Malinen <j@w1.fi>
2015-01-06 02:49:13 +02:00

67 lines
1.6 KiB
C

/*
* SHA1-based PRF
* Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "includes.h"
#include "common.h"
#include "sha1.h"
#include "crypto.h"
/**
* sha1_prf - SHA1-based Pseudo-Random Function (PRF) (IEEE 802.11i, 8.5.1.1)
* @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
* Returns: 0 on success, -1 of failure
*
* This function is used to derive new, cryptographically separate keys from a
* given key (e.g., PMK in IEEE 802.11i).
*/
int sha1_prf(const u8 *key, size_t key_len, const char *label,
const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
{
u8 counter = 0;
size_t pos, plen;
u8 hash[SHA1_MAC_LEN];
size_t label_len = os_strlen(label) + 1;
const unsigned char *addr[3];
size_t len[3];
addr[0] = (u8 *) label;
len[0] = label_len;
addr[1] = data;
len[1] = data_len;
addr[2] = &counter;
len[2] = 1;
pos = 0;
while (pos < buf_len) {
plen = buf_len - pos;
if (plen >= SHA1_MAC_LEN) {
if (hmac_sha1_vector(key, key_len, 3, addr, len,
&buf[pos]))
return -1;
pos += SHA1_MAC_LEN;
} else {
if (hmac_sha1_vector(key, key_len, 3, addr, len,
hash))
return -1;
os_memcpy(&buf[pos], hash, plen);
break;
}
counter++;
}
os_memset(hash, 0, sizeof(hash));
return 0;
}