Skip to content

Instantly share code, notes, and snippets.

michalc /
Last active July 17, 2024 16:15
Restore all objects under S3 prefix in versioned bucket
# Restores all objects under a prefix in an S3 bucket to the version they were before being deleted.
# Works by deleting the latest delete marker for the objects.
import boto3
bucket = 'the-bucket'
prefix = 'the-prefix/'
region = 'eu-west-2'
client = boto3.client('s3', region_name=region)
paginator = client.get_paginator('list_object_versions')
michalc /
Created April 24, 2024 13:34
Script for checking if any PostgreSQL session blocks another
# docker run --rm -it -p 5432:5432 -e POSTGRES_PASSWORD=password postgres:14
import pprint
import threading
import time
from concurrent.futures import ThreadPoolExecutor
from contextlib import contextmanager
import psycopg2
import psycopg2.extras
michalc /
Created November 14, 2023 07:38
Check the stack of apps in CloudFoundry
import json
import os
from urllib.parse import urlparse, parse_qsl
import requests
from rich import box
from rich.console import Console
from rich.table import Table
with open(f'{os.environ["HOME"]}/.cf/config.json') as f:
michalc /
Last active July 19, 2024 04:09
Bulk delete files from an AWS S3 bucket in Python using multiple threads via a parallel (eventually) depth-first search
# Deletes objects in bulk using boto3's delete_objects, but using multiple threads to achieve some
# parallelism - in spite of the GIL multiple HTTP requests to S3 should happen at the same time.
# Instead of looping over all keys under the root prefix, it walks the tree of keys of delimiter-
# defined "folders" in a depth-first way, which allows each page to be processed by a separate
# thread as its discovered. Depth-first is done because the depth is limited by the maximum key
# size of 1024 in S3, and so means that there is a limit to the memory used by the algorithm to
# store the next requests to make. This would not be the case with breadth-first because there is
# no limit to how many keys are in any folder.
# To do the search in parallel, each bit of work (i.e. an HTTP request to fetch a page of keys
michalc /
Last active November 16, 2022 03:49
Decrypt KMS-encrypted SES emails in an S3 bucket
import base64
import json
import boto3
from cryptography.hazmat.primitives.ciphers.aead import AESGCM
s3 = boto3.resource('s3')
bucket = s3.Bucket('my-bucket')
kms_client = boto3.client('kms')
michalc /
Created January 3, 2022 16:37
Generating a Zip 2.0 file that's (just under) 8GiB
# Often it's claimed that a Zip 2.0 file cannot be bigger than 4GiB
# Here's how to make one that's just under 8GiB
from datetime import datetime
from stream_zip import stream_zip, ZIP_32
now =
perms = 0o600
def files():
for i in range(0, 0xffff):
class MyPipeline(_PipelineV2):
# Everything is a method so nothing happens on import time for flexibility (although possibly
# does a bit of discovery magic... need to think about that...)
# Everything is a _static_ method: nothing on self since things are run on different bits of hardware,
# and gets any run-time dependencies injected in
# _PipelineV2 won't actually have any code: other parts of the system will interrogate its
# subclasses as needed. For example
# - Code in Data Flow would construct a DAG
# - The test harness would the run this and upstream pipelines synchronously
michalc /
Last active September 13, 2021 05:27
Use libcrypto (OpenSSL) directly from Python with ctypes without compiling anything: AES decrypt with a little endian CTR counter
from contextlib import contextmanager
from ctypes import POINTER, cdll, c_char_p, c_void_p, c_int, create_string_buffer, byref
from sys import platform
# Uses a _little_ endian CTR counter, which OpenSSL doesn't directly support.
# Could be used to decrypt AES-encrypted ZIP files
def decrypt_aes_256_ctr_little_endian(
key, ciphertext_chunks,
get_libcrypto=lambda: cdll.LoadLibrary({'linux': '', 'darwin': 'libcrypto.dylib'}[platform])
michalc / postman-hawk.js
Last active September 21, 2021 05:44
Postman pre-request script for Hawk authentication in custom header
const hawkId = pm.variables.get('hawk_id');
const hawkKey = pm.variables.get('hawk_key');
const hawkHeader = pm.variables.get('hawk_header') || 'authorization';
const timestamp = parseInt(new Date().getTime() / 1000);
const nonce = CryptoJS.enc.Base64.stringify(CryptoJS.lib.WordArray.random(6));
michalc /
Last active April 3, 2024 17:26
Use libsqlite3 directly from Python with ctypes: without using the built-in sqlite3 Python package, and without compiling anything
# From, which is itself inspired by
from contextlib import contextmanager
from collections import namedtuple
from ctypes import cdll, byref, string_at, c_char_p, c_int, c_double, c_int64, c_void_p
from ctypes.util import find_library
from sys import platform
def query(db_file, sql, params=()):