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/*
* SHA1 T-PRF for EAP-FAST
* 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_t_prf - EAP-FAST Pseudo-Random Function (T-PRF)
* @key: Key for PRF
* @key_len: Length of the key in bytes
* @label: A unique label for each purpose of the PRF
* @seed: Seed value to bind into the key
* @seed_len: Length of the seed
* @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 for EAP-FAST. T-PRF is defined in RFC 4851, Section 5.5.
*/
int sha1_t_prf(const u8 *key, size_t key_len, const char *label,
const u8 *seed, size_t seed_len, u8 *buf, size_t buf_len)
{
unsigned char counter = 0;
size_t pos, plen;
u8 hash[SHA1_MAC_LEN];
size_t label_len = os_strlen(label);
u8 output_len[2];
const unsigned char *addr[5];
size_t len[5];
addr[0] = hash;
len[0] = 0;
addr[1] = (unsigned char *) label;
len[1] = label_len + 1;
addr[2] = seed;
len[2] = seed_len;
addr[3] = output_len;
len[3] = 2;
addr[4] = &counter;
len[4] = 1;
output_len[0] = (buf_len >> 8) & 0xff;
output_len[1] = buf_len & 0xff;
pos = 0;
while (pos < buf_len) {
counter++;
plen = buf_len - pos;
if (hmac_sha1_vector(key, key_len, 5, addr, len, hash))
return -1;
if (plen >= SHA1_MAC_LEN) {
os_memcpy(&buf[pos], hash, SHA1_MAC_LEN);
pos += SHA1_MAC_LEN;
} else {
os_memcpy(&buf[pos], hash, plen);
break;
}
len[0] = SHA1_MAC_LEN;
}
return 0;
}
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