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.
Also documented by Alan Dekok in draft-dekok-emu-eap-session-id
Signed-off-by: Mohit Sethi <mohit.sethi@xxxxxxxx>
---
src/eap_peer/eap_aka.c | 36 +++++++++++++++++++++++++++++-------
src/eap_server/eap_server_aka.c | 38 ++++++++++++++++++++++++++++++--------
2 files changed, 59 insertions(+), 15 deletions(-)
diff --git a/src/eap_peer/eap_aka.c b/src/eap_peer/eap_aka.c
index a444141..6d10b5f 100644
--- a/src/eap_peer/eap_aka.c
+++ b/src/eap_peer/eap_aka.c
@@ -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 +1227,15 @@ static struct wpabuf * eap_aka_process_reauthentication(
EAP_AKA_UNABLE_TO_PROCESS_PACKET);
}
+ /* At this stage the MAC received is verified. Use this mac for
+ * reauth Session-Id calculation if all other checks pass.
+ * Peer does not use local MAC but received MAC
+ * in deriving Session-Id */
+ os_memset(data->reauth_mac, 0, EAP_SIM_MAC_LEN);
+ os_memcpy(data->reauth_mac, attr->mac, EAP_SIM_MAC_LEN);
+ wpa_hexdump(MSG_DEBUG, "EAP-SIM: 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 +1507,26 @@ 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;
- id = os_malloc(*len);
- if (id == NULL)
- return NULL;
+ if(!data->reauth) {
+ *len = 1 + EAP_AKA_RAND_LEN + EAP_AKA_AUTN_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);
+ } 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->nonce_s, EAP_SIM_NONCE_S_LEN);
+ os_memcpy(id + 1 + EAP_SIM_NONCE_S_LEN, data->reauth_mac, EAP_SIM_MAC_LEN);
+ }
- 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);
wpa_hexdump(MSG_DEBUG, "EAP-AKA: Derived Session-Id", id, *len);
return id;
diff --git a/src/eap_server/eap_server_aka.c b/src/eap_server/eap_server_aka.c
index 1bea706..14ef999 100644
--- a/src/eap_server/eap_server_aka.c
+++ b/src/eap_server/eap_server_aka.c
@@ -30,6 +30,7 @@ struct eap_aka_data {
u8 ck[EAP_AKA_CK_LEN];
u8 ik[EAP_AKA_IK_LEN];
u8 res[EAP_AKA_RES_MAX_LEN];
+ u8 reauth_mac[EAP_SIM_MAC_LEN];
size_t res_len;
enum {
IDENTITY, CHALLENGE, REAUTH, NOTIFICATION, SUCCESS, FAILURE
@@ -581,7 +582,17 @@ static struct wpabuf * eap_aka_build_reauth(struct eap_sm *sm,
wpa_printf(MSG_DEBUG, " AT_MAC");
eap_sim_msg_add_mac(msg, EAP_SIM_AT_MAC);
- return eap_sim_msg_finish(msg, data->eap_method, data->k_aut, NULL, 0);
+ struct wpabuf * buf = eap_sim_msg_finish(msg, data->eap_method,
+ data->k_aut, NULL, 0);
+
+ /* Remember this MAC before sending it to peer. This MAC is used for
+ * Session-Id calculation after receiving response peer and after all
+ * other checks pass. */
+ os_memset(data->reauth_mac, 0, EAP_SIM_MAC_LEN);
+ os_memcpy(data->reauth_mac, buf->buf + (int) (wpabuf_len(buf) -
+ EAP_SIM_MAC_LEN), EAP_SIM_MAC_LEN);
+
+ return buf;
}
@@ -1304,14 +1315,25 @@ 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;
- id = os_malloc(*len);
- if (id == NULL)
- return NULL;
+ if(!data->reauth) {
+ *len = 1 + EAP_AKA_RAND_LEN + EAP_AKA_AUTN_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);
+ 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);
+ } 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->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;
--
2.7.4
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