Simon Willison’s Weblog

Dependency Confusion: How I Hacked Into Apple, Microsoft and Dozens of Other Companies (via) Alex Birsan describes a new category of security vulnerability he discovered in the npm, pip and gem packaging ecosystems: if a company uses a private repository with internal package names, uploading a package with the same name to the public repository can often result in an attacker being able to execute their own code inside the networks of their target. Alex scored over $130,000 in bug bounties from this one, from a number of name-brand companies. Of particular note for Python developers: the --extra-index-url argument to pip will consult both public and private registries and install the package with the highest version number! # 10th February 2021, 8:42 pm

Hunting for Malicious Packages on PyPI (via) Jordan Wright installed all 268,000 Python packages from PyPI in containers, and ran Sysdig to capture syscalls made during installation to see if any of them were making extra network calls or reading or writing from the filesystem. Absolutely brilliant piece of security engineering and research. # 14th November 2020, 4:48 am

Pysa: An open source static analysis tool to detect and prevent security issues in Python code (via) Interesting new static analysis tool for auditing Python for security vulnerabilities—things like SQL injection and os.execute() calls. Built by Facebook and tested extensively on Instagram, a multi-million line Django application. # 7th August 2020, 8:50 pm

Bleach, HTML sanitizer and auto-linker. HTML sanitisation is notoriously difficult to do correctly, but Bleach (a Python library) looks like an excellent effort. It uses the html5lib parsing library to deal with potentially malformed HTML, uses a whitelist rather than a blacklist and has a neat feature for auto-linking URLs that is aware of the DOM (so it won’t try to auto-link a URL that is already wrapped in a link element). It was written by the Mozilla team for addons.mozilla.org and support.mozilla.org so it should be production ready. # 25th October 2010, 1:32 pm

Timing attack in Google Keyczar library. An issue I also need to fix in the proposed Django signing code. If you’re comparing two strings in crypto (e.g. seeing if the provided signature matches the expected signature) you need to use a timing independent string comparison function or you risk leaking information. This kind of thing is exactly why I want an audited signing module in Django rather than leaving developers to figure it out on their own. # 4th January 2010, 3:23 pm

Design and code review requested for Django string signing / signed cookies. Do you know your way around web app security and cryptography (in particular signing things using hmac and sha1)? We’d appreciate your help reviewing the usage of these concepts in Django’s proposed string signing and signed cookie implementations. # 4th January 2010, 1:24 pm

Django security updates released. A potential denial of service vulnerability has been discovered in the regular expressions used by Django form library’s EmailField and URLField—a malicious input could trigger a pathological performance. Patches (and patched releases) for Django 1.1 and Django 1.0 have been published. # 10th October 2009, 12:24 am

Why Python Pickle is Insecure. Because pickle is essentially a stack-based interpreter, so you can put os.system on the stack and use it to execute arbitrary commands. # 9th September 2009, 11:04 pm

Django: Security updates released. A fix for a directory traversal attack in the Django development server (the one with the big “never run this in production” warnings in the documentation). Also reminds that the release of 1.1 means that 0.96, released over two years ago, has reached end of life and will not receive any further bug fixes after the just-released 0.96.4. # 29th July 2009, 1:45 pm

Django snippets: Sign a string using SHA1, then shrink it using url-safe base65. I needed a way to create tamper-proof URLs and cookies by signing them, but didn’t want the overhead of a full 40 character SHA1 hash. After some experimentation, it turns out you can knock a 40 char hash down to 27 characters by encoding it using a custom base65 encoding which only uses URL-safe characters. # 27th August 2008, 10:18 pm

Changeset 8162. “Implemented a secure password reset form that uses a token and prompts user for new password”—also sneaks base36 encoding and decoding in to Django. # 31st July 2008, 10:54 pm

IPy. Handy Python module for manipulating IP addresses—use IP(ip_addr).iptype() == ’PUBLIC’ to check that an address isn’t in a private address range. # 24th December 2007, 1:19 pm

Django Changeset 6671. Malcolm Tredinnick: “Implemented auto-escaping of variable output in templates”. Fantastic—Django now has protection against accidental XSS holes, turned on by default. # 14th November 2007, 5:05 pm

Django security fix released. Django’s internationalisation system has a denial of service hole in it; you’re vulnerable if you are using the i18n middleware. Fixes have been made available for trunk, 0.96, 0.95 and 0.91. # 26th October 2007, 9:47 pm

Two months with Ruby on Rails. Good rant—covers both the good and the bad. The first complaint is the lack of XSS protection by default in the template language. Django has the same problem, but the solution was 90% there when I saw Malcolm at OSCON. # 9th October 2007, 12:23 pm