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git.ipfire.org Git - thirdparty/hostap.git/blob - src/crypto/sha256-prf.c
2 * SHA256-based PRF (IEEE 802.11r)
3 * Copyright (c) 2003-2016, Jouni Malinen <j@w1.fi>
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
17 * sha256_prf - SHA256-based Pseudo-Random Function (IEEE 802.11r, 8.5.1.5.2)
19 * @key_len: Length of the key in bytes
20 * @label: A unique label for each purpose of the PRF
21 * @data: Extra data to bind into the key
22 * @data_len: Length of the data
23 * @buf: Buffer for the generated pseudo-random key
24 * @buf_len: Number of bytes of key to generate
25 * Returns: 0 on success, -1 on failure
27 * This function is used to derive new, cryptographically separate keys from a
30 int sha256_prf(const u8
*key
, size_t key_len
, const char *label
,
31 const u8
*data
, size_t data_len
, u8
*buf
, size_t buf_len
)
33 return sha256_prf_bits(key
, key_len
, label
, data
, data_len
, buf
,
39 * sha256_prf_bits - IEEE Std 802.11-2012, 11.6.1.7.2 Key derivation function
41 * @key_len: Length of the key in bytes
42 * @label: A unique label for each purpose of the PRF
43 * @data: Extra data to bind into the key
44 * @data_len: Length of the data
45 * @buf: Buffer for the generated pseudo-random key
46 * @buf_len: Number of bits of key to generate
47 * Returns: 0 on success, -1 on failure
49 * This function is used to derive new, cryptographically separate keys from a
50 * given key. If the requested buf_len is not divisible by eight, the least
51 * significant 1-7 bits of the last octet in the output are not part of the
54 int sha256_prf_bits(const u8
*key
, size_t key_len
, const char *label
,
55 const u8
*data
, size_t data_len
, u8
*buf
,
60 u8 hash
[SHA256_MAC_LEN
];
63 u8 counter_le
[2], length_le
[2];
64 size_t buf_len
= (buf_len_bits
+ 7) / 8;
68 addr
[1] = (u8
*) label
;
69 len
[1] = os_strlen(label
);
73 len
[3] = sizeof(length_le
);
75 WPA_PUT_LE16(length_le
, buf_len_bits
);
77 while (pos
< buf_len
) {
79 WPA_PUT_LE16(counter_le
, counter
);
80 if (plen
>= SHA256_MAC_LEN
) {
81 if (hmac_sha256_vector(key
, key_len
, 4, addr
, len
,
84 pos
+= SHA256_MAC_LEN
;
86 if (hmac_sha256_vector(key
, key_len
, 4, addr
, len
,
89 os_memcpy(&buf
[pos
], hash
, plen
);
97 * Mask out unused bits in the last octet if it does not use all the
100 if (buf_len_bits
% 8) {
101 u8 mask
= 0xff << (8 - buf_len_bits
% 8);
102 buf
[pos
- 1] &= mask
;
105 forced_memzero(hash
, sizeof(hash
));