From 5eefa8115b884f8ab45ac6521f66dc68f555dcd0 Mon Sep 17 00:00:00 2001 From: Mohit Sethi Date: Fri, 17 May 2019 22:06:12 +0300 Subject: [PATCH] EAP-AKA: Add Session-Id derivation during fast-reauth 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 --- src/eap_peer/eap_aka.c | 25 ++++++++++++++++++++++--- src/eap_server/eap_server_aka.c | 29 +++++++++++++++++++++++++---- 2 files changed, 47 insertions(+), 7 deletions(-) diff --git a/src/eap_peer/eap_aka.c b/src/eap_peer/eap_aka.c index a4441413f..da5beee21 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 +1227,14 @@ 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; diff --git a/src/eap_server/eap_server_aka.c b/src/eap_server/eap_server_aka.c index 1bea706d4..1f3884e36 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 @@ -542,6 +543,7 @@ static struct wpabuf * eap_aka_build_reauth(struct eap_sm *sm, struct eap_aka_data *data, u8 id) { struct eap_sim_msg *msg; + struct wpabuf *buf; wpa_printf(MSG_DEBUG, "EAP-AKA: Generating Re-authentication"); @@ -581,7 +583,16 @@ 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); + buf = eap_sim_msg_finish(msg, data->eap_method, data->k_aut, NULL, 0); + + /* Remember this MAC before sending it to the peer. This MAC is used for + * Session-Id calculation after receiving response from the peer and + * after all other checks pass. */ + os_memcpy(data->reauth_mac, + wpabuf_head(buf) + wpabuf_len(buf) - EAP_SIM_MAC_LEN, + EAP_SIM_MAC_LEN); + + return buf; } @@ -1304,14 +1315,24 @@ 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;