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Date: Tue, 23 May 2000 18:48:25 -0300
From: "Federico G. Schwindt" <core.lists.bugtraq@CORE-SDI.COM>
Subject: more majordomo brokeness
To: BUGTRAQ@SECURITYFOCUS.COM
Hi,
Majordomo is a perl script for managing mailing lists. The package
comes with several scripts and a program written in C (wrapper) that
runs setuid to ensure that majordomo performs all the work with proper
permissions (for further information you can check the FAQ that comes
with the package under Doc/ or in
http://www.visi.com/~barr/majordomo-faq.html).
This wrapper is installed by default as root, mode 4755 and group as
the one used for majordomo. What this means? If you can fool majordomo
to run arbitrary commands, they'll be run with uid and gid equal to the
one used for majordomo.
Almost all of these scripts accept an optional configuration from the
command line, which is loaded and evaluated via perl's require keyword.
This file is nothing else than perl code, thus creating a special file
with our commands and pointing it as the configuration of any of the
affected scripts will result in the following (this applies to majordomo
1.94.5):
$ cat /tmp/myconf
system("/bin/sh");
$ id
uid=1000(fgsch) gid=1000(fgsch) groups=1000(fgsch), 0(wheel), 11(core)
$ ./wrapper bounce-remind -C /tmp/myconf
$ id
uid=41(majordom) gid=41(majordom) groups=1000(fgsch), 0(wheel), 11(core)
This is not new. The same problem has been seen in the past in the
majordomo script shipped with the previous version, 1.94.4 (for more
details, http://www.securityfocus.com/bid/903).
Interesting enough, this occurs on several scripts: archive2.pl,
bounce-remind, config-test, digest, majordomo, request-answer and
resend; medit under bin/, and archive_mh.pl, new-list, and sequencer
under Tools/ uses 'require' in the same way, but since the wrapper only
executes those scripts found in the majordomo installation directory,
they cannot be exploited.
The obvious fix is to remove this option from all the involved
scripts, but since it can be useful on large sites with several mailing
lists, we've choosen instead to only allow configuration files from a
trusted directory, removing the problem without loosing functionality.
Diffs:
--- majordomo-1.94.5/Makefile.orig Tue Jan 18 11:01:17 2000
+++ majordomo-1.94.5/Makefile Tue May 23 07:05:24 2000
@@ -63,7 +63,8 @@
# passed to processes run by "wrapper"
W_SHELL = /bin/sh
W_PATH = /bin:/usr/bin:/usr/ucb
-W_MAJORDOMO_CF = $(W_HOME)/majordomo.cf
+W_MAJORDOMO_CF = majordomo.cf
+W_MAJORDOMO_CFDIR = $(W_HOME)/config
# A directory for temp files..
TMPDIR = /usr/tmp
@@ -77,7 +78,8 @@
WRAPPER_FLAGS = -DBIN=\"$(W_HOME)\" -DPATH=\"PATH=$(W_PATH)\" \
-DHOME=\"HOME=$(W_HOME)\" -DSHELL=\"SHELL=$(W_SHELL)\" \
- -DMAJORDOMO_CF=\"MAJORDOMO_CF=$(W_MAJORDOMO_CF)\" \
+ -DMAJORDOMO_CF=\"MAJORDOMO_CF=$(W_MAJORDOMO_CFDIR)/$(W_MAJORDOMO_CF)\"
\
+ -DMAJORDOMO_CFDIR=\"MAJORDOMO_CFDIR=$(W_MAJORDOMO_CFDIR)\" \
$(POSIX)
INSTALL = ./install.sh
--- majordomo-1.94.5/archive2.pl.orig Fri Jan 7 08:00:49 2000
+++ majordomo-1.94.5/archive2.pl Tue May 23 07:47:09 2000
@@ -50,7 +50,7 @@
# Read and execute the .cf file
$cf = $ENV{"MAJORDOMO_CF"} || "/etc/majordomo.cf";
if ($ARGV[0] eq "-C") {
- $cf = $ARGV[1];
+ $cf = "$ENV{'MAJORDOMO_CFDIR'}/$ARGV[1]" unless $ARGV[1] =~ /\//;
shift(@ARGV);
shift(@ARGV);
}
--- majordomo-1.94.5/contrib/archive_mh.pl.orig Mon Mar 10 12:40:41 1997
+++ majordomo-1.94.5/contrib/archive_mh.pl Tue May 23 07:50:23 2000
@@ -17,9 +17,9 @@
$ENV{'PATH'} = "/bin:/usr/bin:/usr/ucb";
# Read and execute the .cf file
-$cf = $ENV{"MAJORDOMO_CF"} || "/tools/majordomo-1.56/majordomo.cf";
+$cf = $ENV{"MAJORDOMO_CF"} || "/etc/majordomo.cf";
if ($ARGV[0] eq "-C") {
- $cf = $ARGV[1];
+ $cf = "$ENV{'MAJORDOMO_CFDIR'}/$ARGV[1]" unless $ARGV[1] =~ /\//;
shift(@ARGV);
shift(@ARGV);
}
--- majordomo-1.94.5/bounce-remind.orig Mon Dec 9 13:49:46 1996
+++ majordomo-1.94.5/bounce-remind Tue May 23 07:47:27 2000
@@ -20,7 +20,7 @@
# Read and execute the .cf file
$cf = $ENV{"MAJORDOMO_CF"} || "/etc/majordomo.cf";
if ($ARGV[0] eq "-C") {
- $cf = $ARGV[1];
+ $cf = "$ENV{'MAJORDOMO_CFDIR'}/$ARGV[1]";
shift(@ARGV);
shift(@ARGV);
}
--- majordomo-1.94.5/config-test.orig Wed Aug 27 12:17:13 1997
+++ majordomo-1.94.5/config-test Tue May 23 16:10:05 2000
@@ -117,6 +117,8 @@
print "\n\tNon obvious things that cause headaches:\n\n";
&header('');
+$ARGV[0] = ($ARGV[0] && $ARGV[0] !~ /\//) ?
+ "$ENV{'MAJORDOMO_CFDIR'}/$ARGV[0]" : '';
$cf = $ARGV[0] || $ENV{'MAJORDOMO_CF'};
if (eval "require '$cf'") {
--- majordomo-1.94.5/digest.orig Fri Jan 7 08:04:34 2000
+++ majordomo-1.94.5/digest Tue May 23 16:02:49 2000
@@ -322,6 +322,8 @@
&abort("-C used without -l");
} else {
# Read and execute the .cf file
+ $opt_c = ($opt_c && $opt_c !~ /\//) ?
+ "$ENV{'MAJORDOMO_CFDIR'}/$opt_c" : '';
$cf = $opt_c || $ENV{"MAJORDOMO_CF"} ||
"/etc/majordomo.cf";
require "$cf";
--- majordomo-1.94.5/majordomo.orig Thu Jan 13 14:29:31 2000
+++ majordomo-1.94.5/majordomo Tue May 23 07:48:42 2000
@@ -29,7 +29,7 @@
while ($ARGV[0]) { # parse for config file or default list
if ($ARGV[0] =~ /^-C$/i) { # sendmail v8 clobbers case
- $cf = $ARGV[1];
+ $cf = "$ENV{'MAJORDOMO_CFDIR'}/$ARGV[1]" unless $ARGV[1] =~
/\//;
shift(@ARGV);
shift(@ARGV);
} elsif ($ARGV[0] eq "-l") {
--- majordomo-1.94.5/medit.orig Mon Apr 28 15:38:05 1997
+++ majordomo-1.94.5/medit Tue May 23 07:48:55 2000
@@ -19,7 +19,7 @@
# Read and execute the .cf file
$cf = $ENV{"MAJORDOMO_CF"} || "/etc/majordomo.cf";
if ($ARGV[0] eq "-C") {
- $cf = $ARGV[1];
+ $cf = "$ENV{'MAJORDOMO_CFDIR'}/$ARGV[1]" unless $ARGV[1] =~ /\//;
shift(@ARGV);
shift(@ARGV);
}
--- majordomo-1.94.5/contrib/new-list.orig Mon Dec 9 13:50:45 1996
+++ majordomo-1.94.5/contrib/new-list Tue May 23 07:50:41 2000
@@ -15,7 +15,7 @@
# Read and execute the .cf file
$cf = $ENV{"MAJORDOMO_CF"} || "/etc/majordomo.cf";
if ($ARGV[0] eq "-C") {
- $cf = $ARGV[1];
+ $cf = "$ENV{'MAJORDOMO_CFDIR'}/$ARGV[1]" unless $ARGV[1] =~ /\//;
shift(@ARGV);
shift(@ARGV);
}
--- majordomo-1.94.5/request-answer.orig Fri Jan 7 08:10:18 2000
+++ majordomo-1.94.5/request-answer Tue May 23 07:49:10 2000
@@ -16,7 +16,7 @@
# Read and execute the .cf file
$cf = $ENV{"MAJORDOMO_CF"} || "/etc/majordomo.cf";
if ($ARGV[0] eq "-C") {
- $cf = $ARGV[1];
+ $cf = "$ENV{'MAJORDOMO_CFDIR'}/$ARGV[1]" unless $ARGV[1] =~ /\//;
shift(@ARGV);
shift(@ARGV);
}
--- majordomo-1.94.5/resend.orig Fri Jan 7 12:32:39 2000
+++ majordomo-1.94.5/resend Tue May 23 16:02:37 2000
@@ -79,6 +79,9 @@
}
# Read and execute the .cf file
+$cfdir = $ENV{"MAJORDOMO_CFDIR"};
+$opt_C = ($opt_C && $opt_C !~ /\//) ? "$cfdir/$opt_C" : '';
+$opt_c = ($opt_c && $opt_c !~ /\//) ? "$cfdir/$opt_c" : '';
$cf = $opt_C || $opt_c || $ENV{"MAJORDOMO_CF"} || "/etc/majordomo.cf";
# Despite not having a place to send the remains of the body,
--- majordomo-1.94.5/contrib/sequencer.orig Mon Dec 9 13:50:48 1996
+++ majordomo-1.94.5/contrib/sequencer Tue May 23 07:50:58 2000
@@ -48,7 +48,7 @@
# Read and execute the .cf file
$cf = $ENV{"MAJORDOMO_CF"} || "/etc/majordomo.cf";
if ($ARGV[0] eq "-C") {
- $cf = $ARGV[1];
+ $cf = "$ENV{'MAJORDOMO_CFDIR'}/$ARGV[1]" unless $ARGV[1] =~ /\//;
shift(@ARGV);
shift(@ARGV);
}
--- majordomo-1.94.5/wrapper.c.orig Wed Aug 27 12:01:12 1997
+++ majordomo-1.94.5/wrapper.c Tue May 23 07:06:23 2000
@@ -42,20 +42,27 @@
# define SHELL "SHELL=/bin/sh"
#endif
+#ifndef MAJORDOMO_CF
+# error "MAJORDOMO_CF not defined; edit Makefile"
+#endif
+
+#ifndef MAJORDOMO_CFDIR
+# error "MAJORDOMO_CFDIR not defined; edit Makefile"
+#endif
+
char * new_env[] = {
HOME, /* 0 */
PATH, /* 1 */
SHELL, /* 2 */
-#ifdef MAJORDOMO_CF
MAJORDOMO_CF, /* 3 */
-#endif
+ MAJORDOMO_CFDIR, /* 4 */
0, /* possibly for USER or LOGNAME */
0, /* possible for LOGNAME */
0, /* possibly for timezone */
0
};
-int new_env_size = 7; /* to prevent overflow problems */
+int new_env_size = 8; /* to prevent overflow problems */
main(argc, argv, env)
int argc;
@@ -89,11 +96,7 @@
* if they exist.
*/
-#ifdef MAJORDOMO_CF
- e = 4; /* the first unused slot in new_env[] */
-#else
- e = 3; /* the first unused slot in new_env[] */
-#endif
+ e = 5; /* the first unused slot in new_env[] */
for (i = 0 ; env[i] != NULL && e <= new_env_size; i++) {
if ((strncmp(env[i], "USER=", 5) == 0) ||
@@ -153,5 +156,6 @@
fprintf(stderr, " PATH is %s,\n", PATH);
fprintf(stderr, " SHELL is %s,\n", SHELL);
fprintf(stderr, " MAJORDOMO_CF is %s\n", MAJORDOMO_CF);
+ fprintf(stderr, " MAJORDOMO_CFDIR is %s\n", MAJORDOMO_CFDIR);
exit(EX_OSERR);
}
MAJORDOMO_CFDIR points to the trusted directory. You should store all
the configuration files there. Be sure that is pointing to the correct
place or majordomo won't work.
We've also modified wrapper.c to barf if neither MAJORDOMO_CF nor
MAJORDOMO_CFDIR are defined, since there is no point in using it
otherwise, plus a few other minor paranoia changes... ;)
Salute,
f.-
--
Federico Schwindt - Developer fgsch@core-sdi.com
Core SDI S.A. http://www.core-sdi.com
--- For a personal reply use fgsch@core-sdi.com