Add documentation

documentation/modules/auxiliary/scanner/http/citrix_directory_traversal.md

@@ -0,0 +1,51 @@
+##  Introduction
+
+An issue was discovered in Citrix Application Delivery Controller (ADC) and Gateway 10.5, 11.1, 12.0, 12.1, and 13.0. The vulnerability, tracked as CVE-2019-19781, allows for directory traversal. If exploited, it could allow an unauthenticated attacker to perform arbitrary code execution.
+
+Because vulnerable servers allow for directory traversal, they will accept the request `GET /vpn/../vpns/` and  process it as a request for `GET /vpns/`, a directory that contains PERL scripts that can be targeted to allow for limited file writing on the vulnerable host.
+
+This module checks if a target server is vulnerable by issuing an HTTP GET request for `/vpn/../vpns/cfg/smb.conf`and then checking the response for `global`since this configuration file should contain global variables. If ``global``is found, the server is vulnerable to CVE-2019-19781.
+
+## Verification Steps
+
+1. Install the module as usual
+
+2. Start msfconsole
+
+3. Do: `use auxiliary/scanner/http/citrix_directory_traversal`
+
+4.  Do: `set RHOSTS [IP]`
+
+5. Do: `run`
+
+
+## Options
+
+1.  `Proxies`  . This option is not set by default.
+2.  `RPORT`  . The default setting is  `80`. To use:  `set RPORT [PORT]`
+3.  `SSL`  . The default setting is  `false`.
+4.  `THREADS`  . The default setting is  `1`.
+5.  `VHOST`  . This option is not set by default.
+
+## Scenarios
+
+```
+msf5 > use auxiliary/scanner/http/citrix_directory_traversal
+
+msf5 auxiliary(scanner/http/citrix_directory_traversal) > set RHOSTS xxx.xxx.xxx.xxx
+
+RHOSTS => xxx.xxx.xxx.xxx
+
+msf5 auxiliary(scanner/http/citrix_directory_traversal) > run
+
+[*] Found xxx.xxx.xxx.xxx/vpn/../vpns/cfg/smb.conf.
+[+] The target is vulnerable to CVE-2019-19781.
+[*] Scanned 1 of 1 hosts (100% complete)
+[*] Auxiliary module execution completed
+```
+
+##  References
+
+1. <https://nvd.nist.gov/vuln/detail/CVE-2019-19781>
+
+2. <https://support.citrix.com/article/CTX267027>