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EAP-AKA: Add Session-Id derivation during fast-reauth

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The Session-Id derivation for EAP-AKA in RFC 5247 only explained how the
Session-Id is derived for regular authentication. Jouni reported it as
an errata with text explaining how to derive it during fast
reauthentication.

This patch now exports the Session-Id for EAP-AKA during fast
reauthentication based on this Session-Id = 0x17 || NONCE_S || MAC
construction.

Also documented by Alan Dekok in draft-dekok-emu-eap-session-id.

Signed-off-by: Mohit Sethi <mohit.sethi@aalto.fi>
This commit is contained in:
Mohit Sethi 2019-05-17 22:06:12 +03:00 • committed by Jouni Malinen
parent 1c16b257a0
commit 5eefa8115b
2 changed files with 47 additions and 7 deletions
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25
src/eap_peer/eap_aka.c
View file

@ -31,6 +31,7 @@ struct eap_aka_data {
u8 emsk[EAP_EMSK_LEN];
u8 rand[EAP_AKA_RAND_LEN], autn[EAP_AKA_AUTN_LEN];
u8 auts[EAP_AKA_AUTS_LEN];
u8 reauth_mac[EAP_SIM_MAC_LEN];
int num_id_req, num_notification;
u8 *pseudonym;
@ -1226,6 +1227,14 @@ static struct wpabuf * eap_aka_process_reauthentication(
EAP_AKA_UNABLE_TO_PROCESS_PACKET);
}
/* At this stage the received MAC has been verified. Use this MAC for
* reauth Session-Id calculation if all other checks pass.
* The peer does not use the local MAC but the received MAC in deriving
* Session-Id. */
os_memcpy(data->reauth_mac, attr->mac, EAP_SIM_MAC_LEN);
wpa_hexdump(MSG_DEBUG, "EAP-AKA: Server MAC",
data->reauth_mac, EAP_SIM_MAC_LEN);
if (attr->encr_data == NULL || attr->iv == NULL) {
wpa_printf(MSG_WARNING, "EAP-AKA: Reauthentication "
"message did not include encrypted data");
@ -1497,14 +1506,24 @@ static u8 * eap_aka_get_session_id(struct eap_sm *sm, void *priv, size_t *len)
if (data->state != SUCCESS)
return NULL;
*len = 1 + EAP_AKA_RAND_LEN + EAP_AKA_AUTN_LEN;
if (!data->reauth)
*len = 1 + EAP_AKA_RAND_LEN + EAP_AKA_AUTN_LEN;
else
*len = 1 + EAP_SIM_NONCE_S_LEN + EAP_SIM_MAC_LEN;
id = os_malloc(*len);
if (id == NULL)
return NULL;
id[0] = data->eap_method;
os_memcpy(id + 1, data->rand, EAP_AKA_RAND_LEN);
os_memcpy(id + 1 + EAP_AKA_RAND_LEN, data->autn, EAP_AKA_AUTN_LEN);
if (!data->reauth) {
os_memcpy(id + 1, data->rand, EAP_AKA_RAND_LEN);
os_memcpy(id + 1 + EAP_AKA_RAND_LEN, data->autn,
EAP_AKA_AUTN_LEN);
} else {
os_memcpy(id + 1, data->nonce_s, EAP_SIM_NONCE_S_LEN);
os_memcpy(id + 1 + EAP_SIM_NONCE_S_LEN, data->reauth_mac,
EAP_SIM_MAC_LEN);
}
wpa_hexdump(MSG_DEBUG, "EAP-AKA: Derived Session-Id", id, *len);
return id;