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There are two modes of ng_pppoe operation, standard and

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nonstandard.  They differ in the values of certain fields in
the PPPoE frame.  Previously, ng_pppoe would start in standard
mode, yet switch to nonstandard one upon reception of a single
nonstandard frame.  After having done so, ng_pppoe would be unable
to interact with standard PPPoE peers.  Thus, a DoS condition
existed that could be triggered by a buggy peer or malicious party.

Since few people have expressed their displeasure WRT this problem,
the default operation of ng_pppoe is left untouched for now.  However,
a new value for the sysctl net.graph.nonstandard_pppoe is introduced,
-1, which will force ng_pppoe stay in standard mode regardless of any
bogus frames floating around.

PR:		kern/47920
Submitted by:	Gleb Smirnoff <glebius <at> cell.sick.ru>
MFC after:	1 week
This commit is contained in:
Yaroslav Tykhiy 2003-12-18 16:38:35 +00:00
parent bb00732864
commit 875467fafa
1 changed files with 38 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
sys/netgraph/ng_pppoe.c
View File

@ -54,6 +54,7 @@
#include <sys/malloc.h> #include <sys/malloc.h>
#include <sys/errno.h> #include <sys/errno.h>
#include <sys/sysctl.h> #include <sys/sysctl.h>
#include <sys/syslog.h>
#include <net/ethernet.h> #include <net/ethernet.h>
#include <netgraph/ng_message.h> #include <netgraph/ng_message.h>
@ -244,23 +245,36 @@ struct ether_header eh_prototype =
{0x00,0x00,0x00,0x00,0x00,0x00}, {0x00,0x00,0x00,0x00,0x00,0x00},
ETHERTYPE_PPPOE_DISC}; ETHERTYPE_PPPOE_DISC};
static int nonstandard; #define PPPOE_KEEPSTANDARD -1 /* never switch to nonstandard mode */
#define PPPOE_STANDARD 0 /* try standard mode (default) */
#define PPPOE_NONSTANDARD 1 /* just be in nonstandard mode */
static int pppoe_mode = PPPOE_STANDARD;
static int static int
ngpppoe_set_ethertype(SYSCTL_HANDLER_ARGS) ngpppoe_set_ethertype(SYSCTL_HANDLER_ARGS)
{ {
int error; int error;
int val; int val;
val = nonstandard; val = pppoe_mode;
error = sysctl_handle_int(oidp, &val, sizeof(int), req); error = sysctl_handle_int(oidp, &val, sizeof(int), req);
if (error != 0 || req->newptr == NULL) if (error != 0 || req->newptr == NULL)
return (error); return (error);
if (val == 1) { switch (val) {
nonstandard = 1; case PPPOE_NONSTANDARD:
pppoe_mode = PPPOE_NONSTANDARD;
eh_prototype.ether_type = ETHERTYPE_PPPOE_STUPID_DISC; eh_prototype.ether_type = ETHERTYPE_PPPOE_STUPID_DISC;
} else { break;
nonstandard = 0; case PPPOE_STANDARD:
pppoe_mode = PPPOE_STANDARD;
eh_prototype.ether_type = ETHERTYPE_PPPOE_DISC; eh_prototype.ether_type = ETHERTYPE_PPPOE_DISC;
break;
case PPPOE_KEEPSTANDARD:
pppoe_mode = PPPOE_KEEPSTANDARD;
eh_prototype.ether_type = ETHERTYPE_PPPOE_DISC;
break;
default:
return (EINVAL);
} }
return (0); return (0);
} }
@ -982,8 +996,21 @@ AAA
length = ntohs(wh->ph.length); length = ntohs(wh->ph.length);
switch(wh->eh.ether_type) { switch(wh->eh.ether_type) {
case ETHERTYPE_PPPOE_STUPID_DISC: case ETHERTYPE_PPPOE_STUPID_DISC:
nonstandard = 1; if (pppoe_mode == PPPOE_STANDARD) {
eh_prototype.ether_type = ETHERTYPE_PPPOE_STUPID_DISC; pppoe_mode = PPPOE_NONSTANDARD;
eh_prototype.ether_type =
ETHERTYPE_PPPOE_STUPID_DISC;
log(LOG_NOTICE,
"Switched to nonstandard PPPoE mode due to "
"packet from %*D\n",
sizeof(wh->eh.ether_shost),
wh->eh.ether_shost, ":");
} else if (pppoe_mode == PPPOE_KEEPSTANDARD)
log(LOG_NOTICE,
"Ignored nonstandard PPPoE packet "
"from %*D\n",
sizeof(wh->eh.ether_shost),
wh->eh.ether_shost, ":");
/* fall through */ /* fall through */
case ETHERTYPE_PPPOE_DISC: case ETHERTYPE_PPPOE_DISC:
/* /*
@ -1185,7 +1212,7 @@ AAA
* from NEWCONNECTED to CONNECTED * from NEWCONNECTED to CONNECTED
*/ */
sp->pkt_hdr = neg->pkt->pkt_header; sp->pkt_hdr = neg->pkt->pkt_header;
if (nonstandard) if (pppoe_mode == PPPOE_NONSTANDARD)
sp->pkt_hdr.eh.ether_type sp->pkt_hdr.eh.ether_type
= ETHERTYPE_PPPOE_STUPID_SESS; = ETHERTYPE_PPPOE_STUPID_SESS;
else else
@ -1237,7 +1264,7 @@ AAA
* Keep a copy of the header we will be using. * Keep a copy of the header we will be using.
*/ */
sp->pkt_hdr = neg->pkt->pkt_header; sp->pkt_hdr = neg->pkt->pkt_header;
if (nonstandard) if (pppoe_mode == PPPOE_NONSTANDARD)
sp->pkt_hdr.eh.ether_type sp->pkt_hdr.eh.ether_type
= ETHERTYPE_PPPOE_STUPID_SESS; = ETHERTYPE_PPPOE_STUPID_SESS;
else else
@ -1519,7 +1546,7 @@ AAA
/* revert the stored header to DISC/PADT mode */ /* revert the stored header to DISC/PADT mode */
wh = &sp->pkt_hdr; wh = &sp->pkt_hdr;
wh->ph.code = PADT_CODE; wh->ph.code = PADT_CODE;
if (nonstandard) if (pppoe_mode == PPPOE_NONSTANDARD)
wh->eh.ether_type = ETHERTYPE_PPPOE_STUPID_DISC; wh->eh.ether_type = ETHERTYPE_PPPOE_STUPID_DISC;
else else
wh->eh.ether_type = ETHERTYPE_PPPOE_DISC; wh->eh.ether_type = ETHERTYPE_PPPOE_DISC;