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crypto: implement HKDF-Expand (RFC 5869)

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This will be required by OWE
This commit is contained in:
James Prestwood 2018-11-16 14:22:51 -08:00 committed by Denis Kenzior
parent 0b42ca7c30
commit 40685e8fe3
2 changed files with 54 additions and 0 deletions
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51
src/crypto.c
View File

@ -446,6 +446,57 @@ bool hkdf_extract_sha256(const uint8_t *key, size_t key_len, uint8_t num_args,
return (ret == 32);
}
bool hkdf_expand_sha256(const uint8_t *key, size_t key_len, const char *info,
size_t info_len, void *out, size_t out_len)
{
uint8_t t[32];
size_t t_len = 0;
struct iovec iov[3];
struct l_checksum *hmac;
uint8_t count = 1;
uint8_t *out_ptr = out;
while (out_len > 0) {
ssize_t ret;
hmac = l_checksum_new_hmac(L_CHECKSUM_SHA256, key, key_len);
iov[0].iov_base = t;
iov[0].iov_len = t_len;
iov[1].iov_base = (void *) info;
iov[1].iov_len = info_len;
iov[2].iov_base = &count;
iov[2].iov_len = 1;
if (!l_checksum_updatev(hmac, iov, 3)) {
l_checksum_free(hmac);
return false;
}
ret = l_checksum_get_digest(hmac, t,
(out_len > 32) ? 32 : out_len);
if (ret < 0) {
l_checksum_free(hmac);
return false;
}
memcpy(out_ptr, t, ret);
out_len -= ret;
out_ptr += ret;
/*
* RFC specifies that T(0) = empty string, so after the first
* iteration we update the length for T(1)...T(N)
*/
t_len = 32;
count++;
l_checksum_free(hmac);
}
return true;
}
/*
* 802.11, Section 11.6.6.7:
* PTK = PRF-X(PMK, "Pairwise key expansion", Min(AA, SA) || Max(AA, SA) ||

3
src/crypto.h
View File

@ -95,6 +95,9 @@ bool prf_sha1(const void *key, size_t key_len,
bool hkdf_extract_sha256(const uint8_t *key, size_t key_len, uint8_t num_args,
uint8_t *out, ...);
bool hkdf_expand_sha256(const uint8_t *key, size_t key_len, const char *info,
size_t info_len, void *out, size_t out_len);
bool crypto_derive_pairwise_ptk(const uint8_t *pmk,
const uint8_t *addr1, const uint8_t *addr2,
const uint8_t *nonce1, const uint8_t *nonce2,