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ERP: Add HMAC-SHA256 KDF (RFC 5295)

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This is needed for ERP key derivation.

Signed-off-by: Jouni Malinen <j@w1.fi>
This commit is contained in:
Jouni Malinen 2014-11-29 21:28:24 +02:00
parent 2a5156a66c
commit 0087061de7
2 changed files with 80 additions and 1 deletions
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76
src/crypto/sha256-kdf.c Normal file
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@ -0,0 +1,76 @@
/*
* HMAC-SHA256 KDF (RFC 5295)
* Copyright (c) 2014, 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 "sha256.h"
/**
* hmac_sha256_kdf - HMAC-SHA256 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
* @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.
*/
int hmac_sha256_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[SHA256_MAC_LEN];
u8 iter = 1;
const unsigned char *addr[4];
size_t len[4];
size_t pos, clen;
addr[0] = T;
len[0] = SHA256_MAC_LEN;
addr[1] = (const unsigned char *) label;
len[1] = os_strlen(label) + 1;
addr[2] = seed;
len[2] = seed_len;
addr[3] = &iter;
len[3] = 1;
if (hmac_sha256_vector(secret, secret_len, 3, &addr[1], &len[1], T) < 0)
return -1;
pos = 0;
for (;;) {
clen = outlen - pos;
if (clen > SHA256_MAC_LEN)
clen = SHA256_MAC_LEN;
os_memcpy(out + pos, T, clen);
pos += clen;
if (pos == outlen)
break;
if (iter == 255) {
os_memset(out, 0, outlen);
return -1;
}
iter++;
if (hmac_sha256_vector(secret, secret_len, 4, addr, len, T) < 0)
{
os_memset(out, 0, outlen);
return -1;
}
}
return 0;
}

5
src/crypto/sha256.h
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@ -1,6 +1,6 @@
/*
* SHA256 hash implementation and interface functions
* Copyright (c) 2003-2013, Jouni Malinen <j@w1.fi>
* Copyright (c) 2003-2014, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
@ -23,5 +23,8 @@ void sha256_prf_bits(const u8 *key, size_t key_len, const char *label,
void tls_prf_sha256(const u8 *secret, size_t secret_len,
const char *label, const u8 *seed, size_t seed_len,
u8 *out, size_t outlen);
int hmac_sha256_kdf(const u8 *secret, size_t secret_len,
const char *label, const u8 *seed, size_t seed_len,
u8 *out, size_t outlen);
#endif /* SHA256_H */