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PPP, EAP: ignore received EAP messages when not doing EAP

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This adds some basic checks to the subroutines of eap_input to check
that we have requested or agreed to doing EAP authentication before
doing any processing on the received packet.  The motivation is to
make it harder for a malicious peer to disrupt the operation of pppd
by sending unsolicited EAP packets.  Note that eap_success() already
has a check that the EAP client state is reasonable, and does nothing
(apart from possibly printing a debug message) if not.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Sylvain Rochet <gradator@gradator.net> (ported to lwIP PPP pcb struct)
This commit is contained in:
Paul Mackerras 2020-02-10 23:33:29 +01:00 committed by Sylvain Rochet
parent 2ee3cbe69c
commit d281d3e959
1 changed files with 18 additions and 0 deletions
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18
src/netif/ppp/eap.c
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@ -1325,6 +1325,12 @@ static void eap_request(ppp_pcb *pcb, u_char *inp, int id, int len) {
int fd;
#endif /* USE_SRP */
/*
* Ignore requests if we're not open
*/
if (pcb->eap.es_client.ea_state <= eapClosed)
return;
/*
* Note: we update es_client.ea_id *only if* a Response
* message is being generated. Otherwise, we leave it the
@ -1737,6 +1743,12 @@ static void eap_response(ppp_pcb *pcb, u_char *inp, int id, int len) {
u_char dig[SHA_DIGESTSIZE];
#endif /* USE_SRP */
/*
* Ignore responses if we're not open
*/
if (pcb->eap.es_server.ea_state <= eapClosed)
return;
if (pcb->eap.es_server.ea_id != id) {
ppp_dbglog(("EAP: discarding Response %d; expected ID %d", id,
pcb->eap.es_server.ea_id));
@ -2043,6 +2055,12 @@ static void eap_success(ppp_pcb *pcb, u_char *inp, int id, int len) {
static void eap_failure(ppp_pcb *pcb, u_char *inp, int id, int len) {
LWIP_UNUSED_ARG(id);
/*
* Ignore failure messages if we're not open
*/
if (pcb->eap.es_client.ea_state <= eapClosed)
return;
if (!eap_client_active(pcb)) {
ppp_dbglog(("EAP unexpected failure message in state %s (%d)",
eap_state_name(pcb->eap.es_client.ea_state),