blob: 5bde66485e6d04d3adf8651939e022cdbbd1932d [file] [log] [blame]
/*
* HMAC-SHA512 KDF (RFC 5295) and HKDF-Expand(SHA512) (RFC 5869)
* Copyright (c) 2014-2017, 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 "sha512.h"
/**
* hmac_sha512_kdf - HMAC-SHA512 based KDF (RFC 5295)
* @secret: Key for KDF
* @secret_len: Length of the key in bytes
* @label: A unique label for each purpose of the KDF or %NULL to select
* RFC 5869 HKDF-Expand() with arbitrary seed (= info)
* @seed: Seed value to bind into the key
* @seed_len: Length of the seed
* @out: Buffer for the generated pseudo-random key
* @outlen: Number of bytes of key to generate
* Returns: 0 on success, -1 on failure.
*
* This function is used to derive new, cryptographically separate keys from a
* given key in ERP. This KDF is defined in RFC 5295, Chapter 3.1.2. When used
* with label = NULL and seed = info, this matches HKDF-Expand() defined in
* RFC 5869, Chapter 2.3.
*/
int hmac_sha512_kdf(const u8 *secret, size_t secret_len,
const char *label, const u8 *seed, size_t seed_len,
u8 *out, size_t outlen)
{
u8 T[SHA512_MAC_LEN];
u8 iter = 1;
const unsigned char *addr[4];
size_t len[4];
size_t pos, clen;
addr[0] = T;
len[0] = SHA512_MAC_LEN;
if (label) {
addr[1] = (const unsigned char *) label;
len[1] = os_strlen(label) + 1;
} else {
addr[1] = (const u8 *) "";
len[1] = 0;
}
addr[2] = seed;
len[2] = seed_len;
addr[3] = &iter;
len[3] = 1;
if (hmac_sha512_vector(secret, secret_len, 3, &addr[1], &len[1], T) < 0)
return -1;
pos = 0;
for (;;) {
clen = outlen - pos;
if (clen > SHA512_MAC_LEN)
clen = SHA512_MAC_LEN;
os_memcpy(out + pos, T, clen);
pos += clen;
if (pos == outlen)
break;
if (iter == 255) {
os_memset(out, 0, outlen);
forced_memzero(T, SHA512_MAC_LEN);
return -1;
}
iter++;
if (hmac_sha512_vector(secret, secret_len, 4, addr, len, T) < 0)
{
os_memset(out, 0, outlen);
forced_memzero(T, SHA512_MAC_LEN);
return -1;
}
}
forced_memzero(T, SHA512_MAC_LEN);
return 0;
}