[UNIX] Molly IRC Bot Command Execution
From: support@securiteam.comDate: 10/19/02
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From: support@securiteam.com To: list@securiteam.com Date: 19 Oct 2002 04:04:42 +0200
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Molly IRC Bot Command Execution
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SUMMARY
<http://www.lysator.liu.se/~unicorn/hacks/molly/> Molly is a small,
simple IRC bot that I use for intra-office communication. She will handle
lunch menus, stock quotes, take polls and stuff like that. A vulnerability
in the product allows remote attackers to cause the program to execute
arbitrary code.
DETAILS
Vulnerable systems:
* Molly version 0.5 and prior
Immune systems:
* Molly version 0.6
1. Due to a call which sends unfiltered user input to be interpreted by
the shell it is possible to run any command at the permission level of the
script.
A more detailed explanation:
In plugins/nslookup.pl the script makes a call to the shell. Sending user
input in the $host variable:
@answer = `/usr/bin/nslookup $host`; # FIXME: Should be configurable.
The user input is not checked for any shell meta-characters or limited to
any set of characters, so users can execute commands by supplying
something like scan-associates.net;/bin/ls
guejez suggest fixing this by making sure $host is only the characters \w
or '.' (This limits nslookup queries). Then use
system('/usr/bin/nslookup', $host); instead of ``, so that the $host
variable is sent as an argument only, not directly to the shell.
The same advice should be used with:
@answer = `/home/hape/bin/winpopup.sh $to $from "$message"`;
In unusedplugins/pop.pl
`/home/hape/bin/sms.pl $words[2] $words[3] "$text"`;
In unusedplugins/sms.pl and
open(SMB, "| smbclient '\\\\$server\\$printer' lkpcourse -P -U
lkpcourse -n lkpcourse -W LKPIFS") || die("Couldn't open
/tmp/hpled.tmp!");
In unusedplugins/hpled.pl. All of which are making calls to the shell
without checking user input.
Fix:
According to the author a fix for some of the issues will be in all
versions after 0.5. The author did make note that anything in the
unusedplugins/directory is not maintained, may not work, and may introduce
security issues into your script. Use with caution.
As a quick fix replace the following line in plugins/nslookup.pl:
@answer = `/usr/bin/nslookup $host`; # FIXME: Should be configurable.
With:
$host =~ s/[^\w\.]//g;
open(NSLOOKUP, "-|", "/usr/bin/nslookup '$host'");
@answer = <NSLOOKUP>;
guejez suggests not to use any plugins from within unusedplugins, but if
you must then replace the following line in unusedplugins/pop.pl
@answer = `/home/hape/bin/winpopup.sh $to $from "$message"`;
With:
$to =~ s/[^\w\.]//g;
$from =~ s/[^\w\.\s]//g;
open(WINPOP, "-|", "/usr/bin/nslookup /home/hape/bin/winpopup.sh '$to'
'$from' '$message'");
@answer = <WINPOP>;
Replace the following line in unusedplugins/sms.pl
`/home/hape/bin/sms.pl $words[2] $words[3] "$text"`;
With:
$words[2] =~ s/[^\w\.\s]//g;
$words[3] =~ s/[^\w\.\s]//g;
$text =~ s/[^\w\.\s]//g;
system('/home/hape/bin/sms.pl', $words[2], $words[3], $text);
And replace the following line in unusedplugins/hpled.pl:
open(SMB, "| smbclient '\\\\$server\\$printer' lkpcourse -P -U lkpcourse
-n lkpcourse -W LKPIFS") || die("Couldn't open /tmp/hpled.tmp!");
With:
$server =~ s/[^\w\.]//g;
$printer =~ s/[^\w\.]//g;
open(SMB, "| smbclient '\\\\$server\\$printer' lkpcourse -P -U lkpcourse
-n lkpcourse -W LKPIFS") || die("Couldn't open /tmp/hpled.tmp!");
Vendor Contact:
07-22-02 - guejez emailed unicorn@lysator.liu.se and alerted him of this
vulnerability.
07-23-02 - guejez received an email confirming vulnerabilities and stating
some issues will be fixed in newer versions and some will not be fixed.
ADDITIONAL INFORMATION
The information has been provided by <mailto:guejez@scan-associates.net>
guejez.
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