package/network/services/ppp/patches/702-pppd-Ignore-received-EAP-messages-when-not-doing-EAP.patch

   1 From 8d45443bb5c9372b4c6a362ba2f443d41c5636af Mon Sep 17 00:00:00 2001
   2 From: Paul Mackerras <paulus@ozlabs.org>
   3 Date: Mon, 3 Feb 2020 16:31:42 +1100
   4 Subject: [PATCH] pppd: Ignore received EAP messages when not doing EAP
   5
   6 This adds some basic checks to the subroutines of eap_input to check
   7 that we have requested or agreed to doing EAP authentication before
   8 doing any processing on the received packet.  The motivation is to
   9 make it harder for a malicious peer to disrupt the operation of pppd
  10 by sending unsolicited EAP packets.  Note that eap_success() already
  11 has a check that the EAP client state is reasonable, and does nothing
  12 (apart from possibly printing a debug message) if not.
  13
  14 Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
  15 ---
  16  pppd/eap.c | 18 ++++++++++++++++++
  17  1 file changed, 18 insertions(+)
  18
  19 diff --git a/pppd/eap.c b/pppd/eap.c
  20 index 1b93db01aebd..082e95343120 100644
  21 --- a/pppd/eap.c
  22 +++ b/pppd/eap.c
  23 @@ -1328,6 +1328,12 @@ int len;
  24         int fd;
  25  #endif /* USE_SRP */
  26
  27 +       /*
  28 +        * Ignore requests if we're not open
  29 +        */
  30 +       if (esp->es_client.ea_state <= eapClosed)
  31 +               return;
  32 +
  33         /*
  34          * Note: we update es_client.ea_id *only if* a Response
  35          * message is being generated.  Otherwise, we leave it the
  36 @@ -1736,6 +1742,12 @@ int len;
  37         u_char dig[SHA_DIGESTSIZE];
  38  #endif /* USE_SRP */
  39
  40 +       /*
  41 +        * Ignore responses if we're not open
  42 +        */
  43 +       if (esp->es_server.ea_state <= eapClosed)
  44 +               return;
  45 +
  46         if (esp->es_server.ea_id != id) {
  47                 dbglog("EAP: discarding Response %d; expected ID %d", id,
  48                     esp->es_server.ea_id);
  49 @@ -2047,6 +2059,12 @@ u_char *inp;
  50  int id;
  51  int len;
  52  {
  53 +       /*
  54 +        * Ignore failure messages if we're not open
  55 +        */
  56 +       if (esp->es_client.ea_state <= eapClosed)
  57 +               return;
  58 +
  59         if (!eap_client_active(esp)) {
  60                 dbglog("EAP unexpected failure message in state %s (%d)",
  61                     eap_state_name(esp->es_client.ea_state),