[Problem] Linux 2.4.5-ac17 ipt_unclean 'fixes'

[Problem] Linux 2.4.5-ac17 ipt_unclean 'fixes'

[J Troy Piper]

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Alan, 

I apologise for having taken so long to write this (I have known about 
this problem since 2.4.5ac17 and have not had a chance to document til 
today) but there seems to be a problem with the ipt_unclean fixes by Rusty 
Russell.  ANY incoming packets from any interface (ppp0 and eth0) are 
marked as 'unclean' with some variation on the following syslog entry:

Jul  8 23:16:04 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long
Jul  8 23:16:05 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long
Jul  8 23:16:16 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long
Jul  8 23:16:18 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long

and thus are blocked by my 'unclean packet dropping' firewall (iptables).

I haven't seen any mention of this on the list, nor have I seen any more 
ipt_unclean patches to address this problem, so here's your heads-up 
(albeit a bit late).

Thanks,

J Troy Piper
jtp@dok.org

Re: [Problem] Linux 2.4.5-ac17 ipt_unclean 'fixes'

[Josh McKinney]

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Me too.

On approximately Sat, Jul 14, 2001 at 05:00:21PM -0500, J Troy Piper wrote:
> 
> > 2.4.5-ac17
> > o	First set of ipt_unclean fixes			(Rusty Russell)
> 
> Alan, 
> 
> I apologise for having taken so long to write this (I have known about 
> this problem since 2.4.5ac17 and have not had a chance to document til 
> today) but there seems to be a problem with the ipt_unclean fixes by Rusty 
> Russell.  ANY incoming packets from any interface (ppp0 and eth0) are 
> marked as 'unclean' with some variation on the following syslog entry:
> 
> Jul  8 23:16:04 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long
> Jul  8 23:16:05 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long
> Jul  8 23:16:16 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long
> Jul  8 23:16:18 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long
> 
> and thus are blocked by my 'unclean packet dropping' firewall (iptables).
> 
> I haven't seen any mention of this on the list, nor have I seen any more 
> ipt_unclean patches to address this problem, so here's your heads-up 
> (albeit a bit late).
> 
> Thanks,
> 
> J Troy Piper
> jtp@dok.org
> -
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Re: [Problem] Linux 2.4.5-ac17 ipt_unclean 'fixes'

[Rusty Russell]

In message <20010714170021.B1391@dok.org> you write:
> today) but there seems to be a problem with the ipt_unclean fixes by Rusty 
> Russell.  ANY incoming packets from any interface (ppp0 and eth0) are 
> marked as 'unclean' with some variation on the following syslog entry:
> 
> Jul  8 23:16:04 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long

Please try this patch which fixes this as well, which is in Linus'
pre-patches.

Rusty.
--
Premature optmztion is rt of all evl. --DK

diff -urN linux-2.4.6/net/ipv4/netfilter/ipt_unclean.c linux-2.4.6-f1/net/ipv4/netfilter/ipt_unclean.c
--- linux-2.4.6/net/ipv4/netfilter/ipt_unclean.c	Wed Jul  4 21:27:32 2001
+++ linux-2.4.6-f1/net/ipv4/netfilter/ipt_unclean.c	Thu Jul  5 19:16:00 2001
@@ -268,6 +268,7 @@
 	  int embedded)
 {
 	u_int8_t *opt = (u_int8_t *)tcph;
+	u_int8_t *endhdr = (u_int8_t *)tcph + tcph->doff * 4;
 	u_int8_t tcpflags;
 	int end_of_options = 0;
 	size_t i;
@@ -373,7 +374,7 @@
 				return 0;
 			}
 			/* CHECK: oversize options. */
-			else if (opt[i+1] + i >= tcph->doff * 4) {
+			else if (&opt[i] + opt[i+1] > endhdr) {
 				limpk("TCP option %u at %Zu too long\n",
 				      (unsigned int) opt[i], i);
 				return 0;
@@ -392,6 +393,7 @@
 check_ip(struct iphdr *iph, size_t length, int embedded)
 {
 	u_int8_t *opt = (u_int8_t *)iph;
+	u_int8_t *endhdr = (u_int8_t *)iph + iph->ihl * 4;
 	int end_of_options = 0;
 	void *protoh;
 	size_t datalen;
@@ -444,7 +446,7 @@
 				return 0;
 			}
 			/* CHECK: oversize options. */
-			else if (opt[i+1] + i > iph->ihl * 4) {
+			else if (&opt[i] + opt[i+1] > endhdr) {
 				limpk("IP option %u at %u too long\n",
 				      opt[i], i);
 				return 0;

Re: [Problem] Linux 2.4.5-ac17 ipt_unclean 'fixes'

[J Troy Piper]

Indeed, the patches work and I see that they have made it into 2.4.5-ac3 
with the rest of the Linux -pre merge.  Thanks.

Troy.

On Mon, Jul 16, 2001 at 08:28:45PM +1000, Rusty Russell wrote:
> In message <20010714170021.B1391@dok.org> you write:
> > today) but there seems to be a problem with the ipt_unclean fixes by Rusty 
> > Russell.  ANY incoming packets from any interface (ppp0 and eth0) are 
> > marked as 'unclean' with some variation on the following syslog entry:
> > 
> > Jul  8 23:16:04 paranoia kernel: ipt_unclean: TCP option 3 at 37 too long
> 
> Please try this patch which fixes this as well, which is in Linus'
> pre-patches.
> 
> Rusty.
> --
> Premature optmztion is rt of all evl. --DK
>