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Mix in more data to GTK/IGTK derivation

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The example GMK-to-GTK derivation described in the IEEE 802.11 standard
is marked informative and there is no protocol reason for following it
since this derivation is done only on the AP/Authenticator and does not
need to match with the Supplicant. Mix in more data into the derivation
process to get more separation from GMK.
This commit is contained in:
Jouni Malinen 2010-11-23 00:57:14 +02:00
parent 783a082ccc
commit 5cb9d5c3d1
1 changed files with 32 additions and 19 deletions
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51
src/ap/wpa_auth.c
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@ -220,6 +220,8 @@ static void wpa_rekey_gmk(void *eloop_ctx, void *timeout_ctx)
"initialization."); "initialization.");
} else { } else {
wpa_auth_logger(wpa_auth, NULL, LOGGER_DEBUG, "GMK rekeyd"); wpa_auth_logger(wpa_auth, NULL, LOGGER_DEBUG, "GMK rekeyd");
wpa_hexdump_key(MSG_DEBUG, "GMK",
wpa_auth->group->GMK, WPA_GMK_LEN);
} }
if (wpa_auth->conf.wpa_gmk_rekey) { if (wpa_auth->conf.wpa_gmk_rekey) {
@ -325,9 +327,12 @@ static struct wpa_group * wpa_group_init(struct wpa_authenticator *wpa_auth,
os_free(group); os_free(group);
return NULL; return NULL;
} }
wpa_hexdump_key(MSG_DEBUG, "GMK", group->GMK, WPA_GMK_LEN);
sha1_prf(rkey, sizeof(rkey), "Init Counter", buf, sizeof(buf), sha1_prf(rkey, sizeof(rkey), "Init Counter", buf, sizeof(buf),
group->Counter, WPA_NONCE_LEN); group->Counter, WPA_NONCE_LEN);
wpa_hexdump_key(MSG_DEBUG, "Key Counter",
group->Counter, WPA_NONCE_LEN);
group->GInit = TRUE; group->GInit = TRUE;
wpa_group_sm_step(wpa_auth, group); wpa_group_sm_step(wpa_auth, group);
@ -995,25 +1000,31 @@ void wpa_receive(struct wpa_authenticator *wpa_auth,
} }
static void wpa_gmk_to_gtk(const u8 *gmk, const u8 *addr, const u8 *gnonce, static void wpa_gmk_to_gtk(const u8 *gmk, const char *label, const u8 *addr,
u8 *gtk, size_t gtk_len) const u8 *gnonce, u8 *gtk, size_t gtk_len)
{ {
u8 data[ETH_ALEN + WPA_NONCE_LEN]; u8 data[ETH_ALEN + WPA_NONCE_LEN + 8 + 16];
u8 *pos;
/* GTK = PRF-X(GMK, "Group key expansion", AA || GNonce) */ /* GTK = PRF-X(GMK, "Group key expansion",
* AA || GNonce || Time || random data)
* The example described in the IEEE 802.11 standard uses only AA and
* GNonce as inputs here. Add some more entropy since this derivation
* is done only at the Authenticator and as such, does not need to be
* exactly same.
*/
os_memcpy(data, addr, ETH_ALEN); os_memcpy(data, addr, ETH_ALEN);
os_memcpy(data + ETH_ALEN, gnonce, WPA_NONCE_LEN); os_memcpy(data + ETH_ALEN, gnonce, WPA_NONCE_LEN);
pos = data + ETH_ALEN + WPA_NONCE_LEN;
wpa_get_ntp_timestamp(pos);
pos += 8;
os_get_random(pos, 16);
#ifdef CONFIG_IEEE80211W #ifdef CONFIG_IEEE80211W
sha256_prf(gmk, WPA_GMK_LEN, "Group key expansion", sha256_prf(gmk, WPA_GMK_LEN, label, data, sizeof(data), gtk, gtk_len);
data, sizeof(data), gtk, gtk_len);
#else /* CONFIG_IEEE80211W */ #else /* CONFIG_IEEE80211W */
sha1_prf(gmk, WPA_GMK_LEN, "Group key expansion", sha1_prf(gmk, WPA_GMK_LEN, label, data, sizeof(data), gtk, gtk_len);
data, sizeof(data), gtk, gtk_len);
#endif /* CONFIG_IEEE80211W */ #endif /* CONFIG_IEEE80211W */
wpa_hexdump_key(MSG_DEBUG, "GMK", gmk, WPA_GMK_LEN);
wpa_hexdump_key(MSG_DEBUG, "GTK", gtk, gtk_len);
} }
@ -2094,20 +2105,22 @@ static int wpa_gtk_update(struct wpa_authenticator *wpa_auth,
{ {
int ret = 0; int ret = 0;
/* FIX: is this the correct way of getting GNonce? */
os_memcpy(group->GNonce, group->Counter, WPA_NONCE_LEN); os_memcpy(group->GNonce, group->Counter, WPA_NONCE_LEN);
inc_byte_array(group->Counter, WPA_NONCE_LEN); inc_byte_array(group->Counter, WPA_NONCE_LEN);
wpa_gmk_to_gtk(group->GMK, wpa_auth->addr, group->GNonce, wpa_gmk_to_gtk(group->GMK, "Group key expansion",
wpa_auth->addr, group->GNonce,
group->GTK[group->GN - 1], group->GTK_len); group->GTK[group->GN - 1], group->GTK_len);
wpa_hexdump_key(MSG_DEBUG, "GTK",
group->GTK[group->GN - 1], group->GTK_len);
#ifdef CONFIG_IEEE80211W #ifdef CONFIG_IEEE80211W
if (wpa_auth->conf.ieee80211w != NO_MGMT_FRAME_PROTECTION) { if (wpa_auth->conf.ieee80211w != NO_MGMT_FRAME_PROTECTION) {
if (os_get_random(group->IGTK[group->GN_igtk - 4], os_memcpy(group->GNonce, group->Counter, WPA_NONCE_LEN);
WPA_IGTK_LEN) < 0) { inc_byte_array(group->Counter, WPA_NONCE_LEN);
wpa_printf(MSG_INFO, "RSN: Failed to get new random " wpa_gmk_to_gtk(group->GMK, "IGTK key expansion",
"IGTK"); wpa_auth->addr, group->GNonce,
ret = -1; group->IGTK[group->GN_igtk - 4],
} WPA_IGTK_LEN);
wpa_hexdump_key(MSG_DEBUG, "IGTK", wpa_hexdump_key(MSG_DEBUG, "IGTK",
group->IGTK[group->GN_igtk - 4], WPA_IGTK_LEN); group->IGTK[group->GN_igtk - 4], WPA_IGTK_LEN);
} }