auth: discard unphased PAP Authenticate-Request packets

Per https://datatracker.ietf.org/doc/html/rfc1334#section-2.2.1:

 Implementation Note: Because the Authenticate-Ack might be
 lost, the authenticator MUST allow repeated Authenticate-
 Request packets after completing the Authentication phase.
 Protocol phase MUST return the same reply Code returned when
 the Authentication phase completed (the message portion MAY be
 different).  Any Authenticate-Request packets received during
 any other phase MUST be silently discarded.

1 files changed, 18 insertions, 5 deletions

diff --git a/accel-pppd/auth/auth_pap.c b/accel-pppd/auth/auth_pap.c
index 40921019..f31be8b4 100644
--- a/accel-pppd/auth/auth_pap.c
+++ b/accel-pppd/auth/auth_pap.c
@@ -43,6 +43,7 @@ struct pap_auth_data {
 	char *peer_id;
 	int req_id;
 	unsigned int started:1;
+	unsigned int active:1;
 };
 
 struct pap_hdr {
@@ -76,6 +77,10 @@ static struct auth_data_t* auth_data_init(struct ppp_t *ppp)
 	d->auth.len = 0;
 	d->ppp = ppp;
 
+	d->h.proto = PPP_PAP;
+	d->h.recv = pap_recv;
+	ppp_register_chan_handler(ppp, &d->h);
+
 	return &d->auth;
 }
 
@@ -83,6 +88,11 @@ static void auth_data_free(struct ppp_t *ppp, struct auth_data_t *auth)
 {
 	struct pap_auth_data *d = container_of(auth, typeof(*d), auth);
 
+	if (d->timeout.tpd)
+		triton_timer_del(&d->timeout);
+
+	ppp_unregister_handler(ppp, &d->h);
+
 	_free(d);
 }
 
@@ -90,14 +100,12 @@ static int pap_start(struct ppp_t *ppp, struct auth_data_t *auth)
 {
 	struct pap_auth_data *d = container_of(auth, typeof(*d), auth);
 
-	d->h.proto = PPP_PAP;
-	d->h.recv = pap_recv;
 	d->timeout.expire = pap_timeout;
 	d->timeout.period = conf_timeout * 1000;
 
 	triton_timer_add(ppp->ses.ctrl->ctx, &d->timeout, 0);
 
-	ppp_register_chan_handler(ppp, &d->h);
+	d->active = 1;
 
 	return 0;
 }
@@ -105,14 +113,14 @@ static int pap_finish(struct ppp_t *ppp, struct auth_data_t *auth)
 {
 	struct pap_auth_data *d = container_of(auth, typeof(*d), auth);
 
+	d->active = 0;
+
 	if (d->timeout.tpd)
 		triton_timer_del(&d->timeout);
 
 	if (d->peer_id)
 		_free(d->peer_id);
 
-	ppp_unregister_handler(ppp, &d->h);
-
 	return 0;
 }
 
@@ -200,6 +208,11 @@ static int pap_recv_req(struct pap_auth_data *p, struct pap_hdr *hdr)
 	int passwd_len;
 	uint8_t *ptr = (uint8_t*)(hdr + 1);
 
+	if (!p->active) {
+		log_ppp_debug("PAP: unexpected packet received\n");
+		return 0;
+	}
+
 	if (p->timeout.tpd)
 		triton_timer_del(&p->timeout);