This Python script tests the CryptProtectData() Windows function. It might help test and solve issues that can affect many Windows programs.

crypt32_test.py

# crypt32_test.py
#
# 2024-05-24 - 1st version published as a gist at
# https://gist.github.com/AltoRetrato/05f6957756931b12dc7ff8a87c2fe835

# TL;DR: This script helps you test the CryptProtectData() Windows function
#        to possibly find and solve issues that can affect many programs.

# ----------------------------------------------------------------------------
# Is Google Chrome pausing sync each time you (re)start the browser?
#
# Does Steam always ask for login even when selecting
# "Remember my password on this device"?
#
# I investigated these and other issues in Chromium Embedded Framework (CEF)
# apps on my PC by starting those apps with the command-line argument
# --enable-logging
#
# One thing they all had in common (Chrome, Steam, Evernote, ...) was an error
# similar to "Failed to encrypt: Access is denied. (0x5)" appearing in the log.
#
# After some debugging, I found that the Windows function CryptProtectData()
# was returning error code 5 (access denied) instead of 0 (no error) on my PC.
# So I wrote this script to reproduce the issue faster and test on other PCs,
# where it worked fine. I just converted this C++ code to Python:
# https://learn.microsoft.com/en-us/windows/win32/api/dpapi/nf-dpapi-cryptprotectdata#examples
#
# Using Process Monitor, I captured events while running the Python script
# and found that lsass.exe encountered an "ACCESS DENIED" error
# when trying to access %APPDATA%\Microsoft\Protect\CREDHIST.
#
# SOLUTION / CONCLUSION
# =====================
#
# Though CREDHIST file permissions were correct, I noticed that the file
# was set to "read-only". Removing the "read-only" attribute solved the issue!
# You can check and change it from a command prompt using the "attrib" command,
# or by right-clicking the file in Windows Explorer and selecting "Properties".
#
# As for what changed the attribute, I have no idea.
#
# From a quick web search, this doesn't seem to be a common issue.
# Still, I think the process I used to find and fix the issue might help
# other users to find other issues as well.
#
# Some possibly related Chromium issues:
#   Logout and Sync Pause Issue
#   https://issues.chromium.org/issues/40281493
#
#   Chrome Sync is paused after closing and opening Chrome
#   https://issues.chromium.org/issues/40936509
#
#   Google not saving my passwords, or prompting me to save pw even though I have the option selected
#   https://issues.chromium.org/issues/337476657

import ctypes
from ctypes import POINTER, byref, c_void_p, c_wchar_p, c_char_p, c_ulong, c_int, c_char

# Define required structures
class DATA_BLOB(ctypes.Structure):
    _fields_ = [("cbData", c_ulong),
                ("pbData", POINTER(c_char))]

# Load CryptProtectData from Crypt32
crypt32 = ctypes.WinDLL('Crypt32.dll')
CryptProtectData = crypt32.CryptProtectData
CryptProtectData.argtypes = [POINTER(DATA_BLOB), c_wchar_p, c_void_p, c_void_p, c_void_p, c_ulong, POINTER(DATA_BLOB)]
CryptProtectData.restype = c_int

# Initialize variables
pbDataInput = b"Hello world of data protection."
cbDataInput = len(pbDataInput) + 1

# Initialize the DataIn structure
DataIn = DATA_BLOB()
DataIn.pbData = ctypes.cast(pbDataInput, POINTER(c_char))
DataIn.cbData = cbDataInput

# Call CryptProtectData
DataOut = DATA_BLOB()
if CryptProtectData(byref(DataIn), None, None, None, None, 0, byref(DataOut)):
    print("The encryption phase worked.")
    # Free memory allocated by CryptProtectData
    ctypes.windll.kernel32.LocalFree(DataOut.pbData)
else:
    print("Encryption error using CryptProtectData.")
    print(f"Error number {ctypes.GetLastError()}.")
input("[ENTER] to terminate.")