In this post I want to create a single file C file program to open a windows inside Linux without using xlib or any similar libraries. The idea is to explore X11 protocol and see how it is used to interact with X server to create windows.

source: HN

This blog post examines the details of the HVIF format using a hex editor and the canonical parser’s source code. In the process of dissecting an example icon, I’ll also show you an optimization bug in the icon image editor.

source: HN

For practical purposes, old source files are not text files. They are binary files, and must be preserved without modification. It is not OK to take an old source file and convert it to UTF-8. For one thing, UTF-8 didn’t even exist in the times of MASM 5.10 and Microsoft C 5.1, of course old tools can’t deal with it!

source: L

This means that someone, somewhere, had been caught using an exploit for this vulnerability. But who discovered the vulnerability and how was it being used? How does the vulnerability work? Why wasn’t it discovered earlier? And what sort of impact does an exploit like this have?

There are still a lot of details that are missing, but this post attempts to explain what we know about the unusual circumstances of this bug, and provides a new technical analysis and proof-of-concept trigger for CVE-2023-4863 (“the WebP 0day“).

Modern video encoding standards such as H.264 are a marvel of hidden complexity. But with hidden complexity comes hidden security risk. Decoding video in practice means interacting with dedicated hardware accelerators and the proprietary, privileged software components used to drive them. The video decoder ecosystem is obscure, opaque, diverse, highly privileged, largely untested, and highly exposed—a dangerous combination.

We introduce and evaluate H26FORGE, domain-specific infrastructure for analyzing, generating, and manipulating syntactically correct but semantically spec-non-compliant video files. Using H26FORGE, we uncover insecurity in depth across the video decoder ecosystem, including kernel memory corruption bugs in iOS, memory corruption bugs in Firefox and VLC for Windows, and video accelerator and application processor kernel memory bugs in multiple Android devices.

https://github.com/h26forge/h26forge

so basically the pixel 7 pro, when you crop and save a screenshot, overwrites the image with the new version, but leaves the rest of the original file in its place

https://twitter.com/ItsSimonTime/status/1636857478263750656

source: L

It seems the reason for pushing values like 10ms back up to 100ms originates from a requirement to emulate the slowness of Netscape. Qt and Firefox source code comments both want to reduce CPU usage but since a value of 20ms is supported, I think they should just be clamping the value to 20ms instead. Or, don’t clamp the value at all! Modern browsers already render 20ms GIF frames just fine, and I’m not sure the “computers are too slow” argument holds up 30 years later.

source: HN

Around this time 30 years ago, two separate working groups were putting the finishing touches on technical standards that would come to reshape the way people observed the world. One technical standard reshaped the way that people used an important piece of office equipment at the time: the fax machine. The other would basically reshape just about everything else, becoming the de facto way that high-quality images and low-quality memes alike are shared on the internet and in professional settings. They took two divergent paths, but they came from the same place: The world of compression standards. The average person has no idea what JBIG, the compression standard most fax machines use, is—but they’ve most assuredly heard about JPEG, which was first publicly released in 1992. The JPEG format is awesome and culture-defining, but this is Tedium, and I am of course more interested in the no-name formats of the world. Today’s Tedium discusses 10 image formats that time forgot. Hope you have the right conversion tool.

The same JSON document can be parsed with different values across microservices, leading to a variety of potential security risks. If you prefer a hands-on approach, try the labs and when they scare you, come back and read on.

https://github.com/BishopFox/json-interop-vuln-labs/

source: HN

Part of Computer Arithmetic. http://www.quadibloc.com/comp/cp02.htm

And How does a computer work? http://www.quadibloc.com/comp/cpint.htm

source: trivium

Authenticated encryption (AE) is used in a wide variety of applications, potentially in settings for which it was not originally designed. Recent research tries to understand what happens when AE is not used as prescribed by its designers. A question given relatively little attention is whether an AE scheme guarantees “key commitment’’: ciphertext should decrypt to a valid plaintext only under the key that was used to generate the ciphertext. As key commitment is not part of AE’s design goal, AE schemes in general do not satisfy it. Nevertheless, one would not expect this seemingly obscure property to have much impact on the security of actual products. In reality, however, products do rely on key commitment. We discuss three recent applications where missing key commitment is exploitable in practice. We provide proof-of-concept attacks via a tool that constructs AES-GCM ciphertext which can be decrypted to two plaintexts valid under a wide variety of file formats, such as PDF, Windows executables, and DICOM. Finally we discuss two solutions to add key commitment to AE schemes which have not been analyzed in the literature: one is a generic approach that adds an explicit key commitment scheme to the AE scheme, and the other is a simple fix which works for AE schemes like AES-GCM and ChaCha20Poly1305, but requires separate analysis for each scheme.

source: white

What I want to focus on is (2), because it’s a lesson we learned the hard way in cryptography and didn’t transfer effectively to the rest of security engineering.

One of my favorite cryptographic attacks is the Bleichenbacher‘06 signature forgery. I wrote up how it works when I found it in python-rsa, so again go read that, but here’s a tl;dr. When you verify an RSA PKCS#1 v1.5 signature, you get a ASN.1 DER structure wrapping the message hash that you need to check. If you don’t parse it strictly, for example by allowing extra fields or trailing bytes, an attacker can fake the signature. This was exploited countless times.

The lesson we learned was that instead of parsing the ASN.1 DER to extract the message hash, we should reconstruct the ASN.1 DER we’d expect to see, and then simply compare it byte-by-byte.

The same technique would have saved Vault.

A format war within a format...

This document provides a gentle introduction to the data structures and formats that define the certificates used in HTTPS. It should be accessible to anyone with a little bit of computer science experience and a bit of familiarity with certificates.

“Gentle.”

source: L

Based on the title, could be just about anything...

The parser will not complain about leading zeros because JSON has no concept of leading zeros.

Unexpectedly a parse error, not a lex error.

Parsing is hard, even when a file format is well specified. But when the specification is ambiguous, it leads to unintended and strange parser and interpreter behaviors that make file formats susceptible to security vulnerabilities. What if we could automatically generate a “safe” subset of any file format, along with an associated, verified parser? That’s our collective goal in Dr. Sergey Bratus’s DARPA SafeDocs program.

We’ve developed two new tools that take the pain out of parsing and make file formats safer:
PolyFile: A polyglot-aware file identification utility with manually instrumented parsers that can semantically label the bytes of a file hierarchically; and
PolyTracker: An automated instrumentation framework that efficiently tracks input file taint through the execution of a program.

source: grugq

In this blog post, I’m going to share about a double-free vulnerability that I discovered in WhatsApp for Android, and how I turned it into an RCE.

Double-free vulnerability in DDGifSlurp in decoding.c in libpl_droidsonroids_gif

source: HN

This article explained what position independent code is, and how it helps create shared libraries with shareable read-only text sections. There are some tradeoffs when choosing between PIC and its alternative (load-time relocation), and the eventual outcome really depends on a lot of factors, like the CPU architecture on which the program is going to run.

source: L

Much of the credit goes to folks much smarter than myself (they will be introduced); this tutorial is meant to curate previous work and literature as much as it is for myself to educate you. The goal here is to allow for any curious, technically-minded newcomer to make sense of all the concepts involved in creating compression quines.

source: L

This covers a lot of ground. I liked this quote, even though there’s much more to the post.

Canonicalization is a quagnet, which is a term of art in vulnerability research meaning quagmire and vulnerability magnet. You can tell it’s bad just by how hard it is to type ‘canonicalization’.

source: HN