Date: Tue, 25 Mar 2003 22:13:38 -0800 (PST) From: Ignacio Solis <isolis@igso.net> To: FreeBSD-gnats-submit@FreeBSD.org Cc: Ignacio Solis <isolis@igso.net> Subject: bin/50310: natd / libalias fix to allow dcc resume in irc Message-ID: <200303260613.h2Q6Dcg7049971@miramar.cse.ucsc.edu> Resent-Message-ID: <200303260610.h2Q6ACcV034872@freefall.freebsd.org>
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>Number: 50310
>Category: bin
>Synopsis: natd / libalias fix to allow dcc resume in irc
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Mar 25 22:10:12 PST 2003
>Closed-Date:
>Last-Modified:
>Originator: Ignacio Solis
>Release: FreeBSD 5.0-RELEASE i386
>Organization:
UC Santa Cruz, California, US
>Environment:
System: FreeBSD imperial.casa.igso.net 5.0-RELEASE FreeBSD 5.0-RELEASE #5: Tue
Jan 28 23:31:36 PST 2003 isolis@imperial.casa.igso.net:/usr/obj/usr/src/sys/IMPERIAL i386
Machine running natd as router/firewall, clients trying to do DCC RESUME while downloading files from irc
>Description:
The current implementation of libalias has a simple way of doing NAT
for irc connections. It assumes that DCC messages all have the same format,
namely "DCC command file ip port .... etc". The RESUME command has a different
structure, and hence the simple assumptions of libalias make RESUME fail,
sending out erroneously translated messages. The format of RESUME is: "DCC
RESUME port size", where port is the port of the sender of the file (where we
connect), hence no translation is necesary. The problem can be clearly seen
with 2 tcpdumps (with packet contents) at the sides of the nat box.
>How-To-Repeat:
Enable natd on the firewall/router. Have a client connect to IRC. Download a
piece of a file. Now try to download the rest of the file with a RESUME.
>Fix:
This is a simple fix that just passes the packet through if it sees
it's a RESUME command.
--- libalias_dcc_resume.diff begins here ---
--- alias_irc.c.backup Tue Mar 25 01:28:12 2003
+++ alias_irc.c Tue Mar 25 02:39:39 2003
@@ -140,6 +140,20 @@
}
}
+
+ if( sptr[i+0] == 'R' &&
+ sptr[i+1] == 'E' &&
+ sptr[i+2] == 'S' &&
+ sptr[i+3] == 'U' &&
+ sptr[i+4] == 'M' &&
+ sptr[i+5] == 'E' &&
+ sptr[i+6] == ' '){
+ /* It's a resume packet, let it through, lBAD_CTCP
+ * will copy the rest of the packet */
+ DBprintf(("RESUME command...\n"));
+ goto lBAD_CTCP;
+ }
+
DBprintf(("Transferring command...\n"));
while(sptr[i] != ' ') {
newpacket[iCopy++] = sptr[i];
--- libalias_dcc_resume.diff ends here ---
>Release-Note:
>Audit-Trail:
>Unformatted:
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