Ruby On Rails JSON Processor YAML Deserialization Scanner

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Auxiliary  
include Msf::Exploit::Remote::HttpClient  
include Msf::Auxiliary::Scanner  
  
def initialize(info={})  
super(update_info(info,  
'Name' => 'Ruby on Rails JSON Processor YAML Deserialization Scanner',  
'Description' => %q{  
This module attempts to identify Ruby on Rails instances vulnerable to  
an arbitrary object instantiation flaw in the JSON request processor.  
},  
'Author' =>  
[  
'jjarmoc', # scanner module  
'hdm' # CVE-2013-0156 scanner, basis of this technique.  
],  
'License' => MSF_LICENSE,  
'References' =>  
[  
['CVE', '2013-0333']  
]  
))  
  
register_options([  
OptString.new('TARGETURI', [true, "The URI to test", "/"]),  
OptEnum.new('HTTP_METHOD', [true, 'HTTP Method', 'POST', ['GET', 'POST', 'PUT']]),  
])  
end  
  
def send_probe(pdata)  
res = send_request_cgi({  
'uri' => normalize_uri(datastore['TARGETURI']),  
'method' => datastore['HTTP_METHOD'],  
'ctype' => 'application/json',  
'data' => pdata  
})  
end  
  
def run_host(ip)  
  
# Straight JSON as a baseline  
res1 = send_probe(  
"{ \"#{Rex::Text.rand_text_alpha(rand(8)+1)}\" : \"#{Rex::Text.rand_text_alpha(rand(8)+1)}\" }"  
)  
  
unless res1  
vprint_status("#{rhost}:#{rport} No reply to the initial JSON request")  
return  
end  
  
if res1.code.to_s =~ /^[5]/  
vprint_error("#{rhost}:#{rport} The server replied with #{res1.code} for our initial JSON request, double check TARGETURI and HTTP_METHOD")  
return  
end  
  
# Deserialize a hash, this should work if YAML deserializes.  
res2 = send_probe("--- {}\n".gsub(':', '\u003a'))  
  
unless res2  
vprint_status("#{rhost}:#{rport} No reply to the initial YAML probe")  
return  
end  
  
# Deserialize a malformed object, inducing an error.  
res3 = send_probe("--- !ruby/object:\x00".gsub(':', '\u003a'))  
  
unless res3  
vprint_status("#{rhost}:#{rport} No reply to the second YAML probe")  
return  
end  
  
vprint_status("Probe response codes: #{res1.code} / #{res2.code} / #{res3.code}")  
  
if (res2.code == res1.code) and (res3.code != res2.code) and (res3.code != 200)  
# If first and second requests are the same, and the third is different but not a 200, we're vulnerable.  
print_good("#{rhost}:#{rport} is likely vulnerable due to a #{res3.code} reply for invalid YAML")  
report_vuln({  
:host => rhost,  
:port => rport,  
:proto => 'tcp',  
:name => self.name,  
:info => "Module triggered a #{res3.code} reply",  
:refs => self.references  
})  
else  
# Otherwise we're not likely vulnerable.  
vprint_status("#{rhost}:#{rport} is not likely to be vulnerable or TARGETURI & HTTP_METHOD must be set")  
end  
end  
end  
`