Directory traversal vulnerability in svcstatus.c (historylog)

Peoples

I've discovered a directory traversal vulnerability in the svcstatus.c
file, allowing a remote attacker to view any file on the filesystem
that's visible to the web server user.  When viewing a specific
historical entry, and then setting the parameter for TIMEBUF to
"../../../..(etc)/path/to/file" you get to view the file.  For
example:

 http://somesite.com/xymon-cgi/historylog.sh?HOST=somehost&SERVICE=conn&TIMEBUF=../../../../../../../../../../../etc/resolv.conf

Here's a patch to prevent it:

---- web/svcstatus.c.orig        2011-05-06 12:12:45.000000000 +1000
+++ web/svcstatus.c     2011-05-06 13:20:47.000000000 +1000
@@ -83,6 +83,12 @@
                else if (strcasecmp(cwalk->name, "TIMEBUF") == 0) {
                        /* Only for the historical logs */
                        tstamp = strdup(cwalk->value);
+                       char *p = basename(tstamp);
+                       /* Sanity check timestamp to avoid dir
traversal attacks */
+                       if (strcmp(p,tstamp) != 0) {
+                               errormsg("Invalid time specification\n");
+                               return 1;
+                       };
                }
                else if (strcasecmp(cwalk->name, "CLIENT") == 0) {
                        char *p;


I'm not a C coder, so there's an excellent chance someone else can
come up with a better patch.  It would be nice to log an error into
the web server log, but it doesn't work for me, and I'm guessing the
xymon CGI process closes stderr when it starts up or something like
that.

Cheers
Jeremy