OpenSSH Security Advisory (adv.channelalloc)

[Markus Friedl <markus () openbsd org>]

1. Systems affected:

        All versions of OpenSSH between 2.0 and 3.0.2 contain
        an off-by-one error in the channel code.

        OpenSSH 3.1 and later are not affected.

2. Impact:

        This bug can be exploited locally by an authenticated user
        logging into a vulnerable OpenSSH server or by a malicious
        SSH server attacking a vulnerable OpenSSH client.
        
3. Solution:

        Upgrade to OpenSSH 3.1 or apply the following patch.

4. Credits:

        This bug was discovered by Joost Pol <joost () pine nl>


Appendix:

Index: channels.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/channels.c,v
retrieving revision 1.170
retrieving revision 1.171
diff -u -r1.170 -r1.171
--- channels.c  27 Feb 2002 21:23:13 -0000      1.170
+++ channels.c  4 Mar 2002 19:37:58 -0000       1.171
@@ -146,7 +146,7 @@
 {
        Channel *c;
 
-       if (id < 0 || id > channels_alloc) {
+       if (id < 0 || id >= channels_alloc) {
                log("channel_lookup: %d: bad id", id);
                return NULL;
        }