description = [[
Detects Ruby on Rails servers vulnerable to object injection, remote command executions and denial of service attacks. (CVE-2013-0156)

All Ruby on Rails versions before 2.3.15, 3.0.x before 3.0.19, 3.1.x before 3.1.10, and 3.2.x before 3.2.11 are vulnerable. This script
sends 3 harmless yaml payloads to detect vulnerable installations. If the malformed object receives a status 500 response, the server
is processing YAML objects and therefore is likely vulnerable.

References:
* https://community.rapid7.com/community/metasploit/blog/2013/01/10/exploiting-ruby-on-rails-with-metasploit-cve-2013-0156',
* https://groups.google.com/forum/?fromgroups=#!msg/rubyonrails-security/61bkgvnSGTQ/nehwjA8tQ8EJ',
* http://cvedetails.com/cve/2013-0156/

TODO:
* Add argument to exploit cmd exec vuln
]]

---
-- @usage
-- nmap -sV --script http-vuln-cve2013-0156 <target>
-- nmap -sV --script http-vuln-cve2013-0156 --script-args uri="/test/" <target>
--
-- @output
-- PORT   STATE SERVICE REASON
-- 80/tcp open  http    syn-ack
-- | http-vuln-cve2013-0156:
-- |   VULNERABLE:
-- |   Parameter parsing vulnerabilities in several versions of Ruby on Rails allow object injection, remote command execution and Denial Of Service attacks (CVE-2013-0156)
-- |     State: VULNERABLE
-- |     Risk factor: High
-- |     Description:
-- |       All Ruby on Rails versions before 2.3.15, 3.0.x before 3.0.19, 3.1.x before 3.1.10, and 3.2.x before 3.2.11 are vulnerable to object injection, remote command execution and denial of service attacks.
-- |       The attackers don't need to be authenticated to exploit these vulnerabilities.
-- |
-- |     References:
-- |       https://groups.google.com/forum/?fromgroups=#!msg/rubyonrails-security/61bkgvnSGTQ/nehwjA8tQ8EJ
-- |       https://community.rapid7.com/community/metasploit/blog/2013/01/10/exploiting-ruby-on-rails-with-metasploit-cve-2013-0156
-- |_      http://cvedetails.com/cve/2013-0156/
--
-- @args http-vuln-cve2013-0156.uri Basepath URI (default: /).
---

author = "Paulino Calderon <calderon@websec.mx>"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"exploit","vuln"}

local http = require "http"
local shortport = require "shortport"
local stdnse = require "stdnse"
local vulns = require "vulns"

portrule = shortport.http

local PAYLOAD_OK = [=[<?xml version="1.0" encoding="UTF-8"?>
<probe type="string"><![CDATA[
nmap
]]></probe>]=]

local PAYLOAD_TIME = [=[<?xml version="1.0" encoding="UTF-8"?>
<probe type="yaml"><![CDATA[
--- !ruby/object:Time {}

]]></probe>]=]

local PAYLOAD_MALFORMED = [=[<?xml version="1.0" encoding="UTF-8"?>
<probe type="yaml"><![CDATA[
--- !ruby/object:^@
]]></probe>
]=]

---
--detect(host, port, uri)
--Sends 3 payloads where one of them is malformed. Status 500 indicates that yaml parsing is enabled.
---
local function detect(host, port, uri)
  local opts = {header={}}
  opts["header"]["Content-type"] = 'application/xml'

  local req_ok = http.post(host, port, uri, opts, nil, PAYLOAD_OK)
  local req_time = http.post(host, port, uri, opts, nil, PAYLOAD_TIME)
  stdnse.debug2("First request returned status %d. Second request returned status %d", req_ok.status, req_time.status)
  if req_ok.status == 200 and req_time.status == 200 then
    local req_malformed = http.post(host, port, uri, opts, nil, PAYLOAD_MALFORMED)
    stdnse.debug2("Malformed request returned status %d", req_malformed.status)
    if req_malformed.status == 500 then
      return true
    end
  end

  return false
end

---
--MAIN
action = function(host, port)
  local uri = stdnse.get_script_args(SCRIPT_NAME..".uri") or "/"
  local vuln_table = {
    title = "Parameter parsing vulnerabilities in several versions of Ruby on Rails allow object injection, remote command execution and Denial Of Service attacks (CVE-2013-0156)",
    state = vulns.STATE.NOT_VULN,
    risk_factor = "High",
    description = [[
All Ruby on Rails versions before 2.3.15, 3.0.x before 3.0.19, 3.1.x before 3.1.10, and 3.2.x before 3.2.11 are vulnerable to object injection, remote command execution and denial of service attacks.
The attackers don't need to be authenticated to exploit these vulnerabilities.
]],

    references = {
      'https://community.rapid7.com/community/metasploit/blog/2013/01/10/exploiting-ruby-on-rails-with-metasploit-cve-2013-0156',
      'https://groups.google.com/forum/?fromgroups=#!msg/rubyonrails-security/61bkgvnSGTQ/nehwjA8tQ8EJ',
      'http://cvedetails.com/cve/2013-0156/',
    }
  }

  if detect(host,port,uri) then
    stdnse.debug1("Received status 500 as expected in vulnerable installations. Marking as vulnerable...")
    vuln_table.state = vulns.STATE.VULN
    local report = vulns.Report:new(SCRIPT_NAME, host, port)
    return report:make_output(vuln_table)
  end

  return nil
end