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crypto: Add crypto_derive_sae_pt_ecc

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This commit is contained in:
Denis Kenzior 2021-07-07 12:36:10 -05:00
parent 308071796a
commit 277437f3d6
2 changed files with 75 additions and 0 deletions
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68
src/crypto.c
View File

@ -33,6 +33,7 @@
#include <ell/ell.h>
#include "ell/useful.h"
#include "src/missing.h"
#include "src/crypto.h"
@ -1144,3 +1145,70 @@ bool crypto_derive_pmkid(const uint8_t *pmk,
else
return hmac_sha1(pmk, 32, data, 20, out_pmkid, 16);
}
/* 802.11-2020, Table 12-1 Hash algorithm based on length of prime */
static enum l_checksum_type ecc_hash_from_prime_len(size_t prime_len)
{
if (prime_len <= 256 / 8)
return L_CHECKSUM_SHA256;
if (prime_len <= 384 / 8)
return L_CHECKSUM_SHA384;
return L_CHECKSUM_SHA512;
}
struct l_ecc_point *crypto_derive_sae_pt_ecc(unsigned int group,
const char *ssid,
const char *password,
const char *identifier)
{
const struct l_ecc_curve *curve = l_ecc_curve_from_ike_group(group);
enum l_checksum_type hash;
size_t hash_len;
uint8_t pwd_seed[64]; /* SHA512 is the biggest possible right now */
uint8_t pwd_value[128];
size_t pwd_value_len;
_auto_(l_ecc_scalar_free) struct l_ecc_scalar *u1 = NULL;
_auto_(l_ecc_scalar_free) struct l_ecc_scalar *u2 = NULL;
_auto_(l_ecc_point_free) struct l_ecc_point *p1 = NULL;
_auto_(l_ecc_point_free) struct l_ecc_point *p2 = NULL;
_auto_(l_ecc_point_free) struct l_ecc_point *pt = NULL;
if (!curve)
return NULL;
hash = ecc_hash_from_prime_len(l_ecc_curve_get_scalar_bytes(curve));
hash_len = l_checksum_digest_length(hash);
/* pwd-seed = HKDF-Extract(ssid, password [|| identifier]) */
hkdf_extract(hash, ssid, strlen(ssid), 2, pwd_seed,
password, strlen(password),
identifier, identifier ? strlen(identifier) : 0);
/* len = olen(p) + floor(olen(p)/2) */
pwd_value_len = l_ecc_curve_get_scalar_bytes(curve);
pwd_value_len += pwd_value_len / 2;
/*
* pwd-value = HKDF-Expand(pwd-seed, "SAE Hash to Element u1 P1", len)
*/
hkdf_expand(hash, pwd_seed, hash_len, "SAE Hash to Element u1 P1",
pwd_value, pwd_value_len);
u1 = l_ecc_scalar_new_modp(curve, pwd_value, pwd_value_len);
/*
* pwd-value = HKDF-Expand(pwd-seed, "SAE Hash to Element u2 P2", len)
*/
hkdf_expand(hash, pwd_seed, hash_len, "SAE Hash to Element u2 P2",
pwd_value, pwd_value_len);
u2 = l_ecc_scalar_new_modp(curve, pwd_value, pwd_value_len);
p1 = l_ecc_point_from_sswu(u1);
p2 = l_ecc_point_from_sswu(u2);
pt = l_ecc_point_new(curve);
l_ecc_point_add(pt, p1, p2);
return l_steal_ptr(pt);
}

7
src/crypto.h
View File

@ -23,6 +23,8 @@
#include <stddef.h>
#include <stdbool.h>
struct l_ecc_point;
enum crypto_cipher {
CRYPTO_CIPHER_WEP40 = 0x000fac01,
CRYPTO_CIPHER_WEP104 = 0x000fac05,
@ -146,3 +148,8 @@ bool crypto_derive_ft_ptk(const uint8_t *pmk_r1, const uint8_t *pmk_r1_name,
bool crypto_derive_pmkid(const uint8_t *pmk,
const uint8_t *addr1, const uint8_t *addr2,
uint8_t *out_pmkid, bool use_sha256);
struct l_ecc_point *crypto_derive_sae_pt_ecc(unsigned int group,
const char *ssid,
const char *password,
const char *identifier);