Retrieve Windows Credential via Python

wincred.py

"""
Access windows credentials

Credentials must be stored in the Windows Credentials Manager in the Control
Panel. This helper will search for "generic credentials" under the section
"Windows Credentials"

Example usage::

    result = get_generic_credential('foobar')
    if result:
        print("NAME:", result.username)
        print("PASSWORD:", result.password)
    else:
        print('No matching credentials found')

Based on https://gist.github.com/exhuma/a310f927d878b3e5646dc67dfa509b42
which was based on https://gist.github.com/mrh1997/717b14f5783b49ca14310419fa7f03f6
"""
import ctypes as ct
import ctypes.wintypes as wt
from enum import Enum
from typing import NamedTuple, Optional

LPBYTE = ct.POINTER(wt.BYTE)

Credential = NamedTuple('Credential', [
    ('username', str),
    ('password', str)
])


def as_pointer(cls):
    """
    Class decorator which converts the class to ta ctypes pointer

    :param cls: The class to decorate
    :return: The class as pointer
    """
    output = ct.POINTER(cls)
    return output


class CredType(Enum):
    """
    CRED_TYPE_* enumeration (wincred.h)
    https://docs.microsoft.com/en-us/windows/win32/api/wincred/ns-wincred-credentialw
    """
    GENERIC = 0x01
    DOMAIN_PASSWORD = 0x02
    DOMAIN_CERTIFICATE = 0x03
    DOMAIN_VISIBLE_PASSWORD = 0x04
    GENERIC_CERTIFICATE = 0x05
    DOMAIN_EXTENDED = 0x06
    MAXIMUM = 0x07
    MAXIMUM_EX = MAXIMUM + 1000


@as_pointer
class CredentialAttribute(ct.Structure):
    """
    PCREDENTIAL_ATTRIBUTEW structure (wincred.h)
    https://docs.microsoft.com/en-us/windows/win32/api/wincred/ns-wincred-credential_attributew
    """
    _fields_ = [
        ('Keyword', wt.LPWSTR),
        ('Flags', wt.DWORD),
        ('ValueSize', wt.DWORD),
        ('Value', LPBYTE)]


@as_pointer
class WinCredential(ct.Structure):
    """
    CREDENTIALW structure (wincred.h)
    https://docs.microsoft.com/en-us/windows/win32/api/wincred/ns-wincred-credentialw
    """
    _fields_ = [
        ('Flags', wt.DWORD),
        ('Type', wt.DWORD),
        ('TargetName', wt.LPWSTR),
        ('Comment', wt.LPWSTR),
        ('LastWritten', wt.FILETIME),
        ('CredentialBlobSize', wt.DWORD),
        ('CredentialBlob', LPBYTE),
        ('Persist', wt.DWORD),
        ('AttributeCount', wt.DWORD),
        ('Attributes', CredentialAttribute),
        ('TargetAlias', wt.LPWSTR),
        ('UserName', wt.LPWSTR)]


def get_generic_credential(name: str) -> Optional[Credential]:
    """
    Returns a tuple of name and password of a generic Windows credential.

    If no matching credential is found, this will return ``None``

    :param name: The lookup string for the credential.
    """
    advapi32 = ct.WinDLL('Advapi32.dll')
    advapi32.CredReadW.restype = wt.BOOL
    advapi32.CredReadW.argtypes = [wt.LPCWSTR, wt.DWORD, wt.DWORD, ct.POINTER(WinCredential)]

    cred_ptr = WinCredential()
    if advapi32.CredReadW(name, CredType.GENERIC.value, 0, ct.byref(cred_ptr)):
        try:
            username = cred_ptr.contents.UserName
            cred_blob = cred_ptr.contents.CredentialBlob
            cred_blob_size = cred_ptr.contents.CredentialBlobSize
            password_as_list = [int.from_bytes(cred_blob[pos:pos+2], 'little')
                                for pos in range(0, cred_blob_size, 2)]
            password = ''.join(map(chr, password_as_list))
            return Credential(username, password)
        finally:
            advapi32.CredFree(cred_ptr)
    return None


def main():
    result = get_generic_credential('foobar')
    if result:
        print("NAME:", result.username)
        print("PASSWORD:", result.password)
    else:
        print('No matching credentials found')


if __name__ == '__main__':
    main()

I've made a small update to set restype and argtypes for CredReadW (where this is setting them for the unused CredReadA).

Also fixed links to Windows documentation, and added docstrings.

https://gist.github.com/RodneyRichardson/c1049d1b92f263109428542b94dd255c

Thanks for the update. I merged your changes

the fact you're using chr means you can't decode emoji, and other valid things for a password.
Is there a reason you moved away from the 'source' material, and didn't want to use the decode that can handle those?

python cred_str = ct.string_at(cred_blob, cred_blob_size) password = cred_str.decode('utf-16le', errors='ignore') return Credential(username, password)
NAME: test
PASSWORD: awesome🫠

vs

PASSWORD: Traceback (most recent call last):
File "windows_creds_interface\wincreds2.py", line 161, in
main()
File "windows_creds_interface\wincreds2.py", line 155, in main
print("PASSWORD:", result.password)
UnicodeEncodeError: 'utf-8' codec can't encode characters in position 7-8: surrogates not allowed

Windows 11
Python 3.12.1

@spdkils unfortunately I don't remember the reasons why I deviated from that. But I don't feel particularly comfortable about using unicode in passwords. I don't see a technical reason why you shouldn't allow it, but unicode has plenty of invisible control-characters that could mess with the data. Considering that there's no real intereset in ever displaying the passwords that shouldn't be an issue. Nevertheless, I feel safer not opening up that pandora's box.

Having said that, your code uses error='ignore' which modifies the resulting string if things break. Meaning that you get different data back from whatever was stored. This leads to hard to debug errors in any application code using this. I would stick to the default (i.e. not specifying the error argument). That will raise an exception which will lead you on the right track whenever it happens.