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Fun-reliable side-channels for cross-container communication (via) Here’s a really intelligent hack for speaking between completely different processes working in several containers on the identical machine. It’s primarily based on intelligent abuse of POSIX advisory locks which permit a course of to create and detect locks throughout byte offset ranges:
These properties mixed are sufficient to supply a primary cross-container side-channel primitive, as a result of a course of in a single container can set a read-lock at some interval on
/proc/self/ns/time, and a course of in one other container can observe the presence of that lock by querying for a hypothetically intersecting write-lock.
I dumped the C proof-of-concept into GPT-5 for a code-level explanation, then had it assist me work out learn how to run it in Docker. Here’s the recipe that labored for me:
cd /tmp
wget
docker run --rm -it -v "$PWD:/src"
-w /src gcc:13 bash -lc 'gcc -Wall -O2
-o h4x0rchat h4x0rchat.c && ./h4x0rchat'
Run that docker run line in two separate terminal home windows and you’ll chat between the 2 of them like this:
This web page was created programmatically, to learn the article in its authentic location you’ll be able to go to the hyperlink bellow:
https://simonwillison.net/2025/Nov/12/h4x0rchat/
and if you wish to take away this text from our website please contact us
This web page was created programmatically, to learn the article in its authentic location you…
This web page was created programmatically, to learn the article in its unique location you…
This web page was created programmatically, to learn the article in its unique location you…
This web page was created programmatically, to learn the article in its authentic location you…
This web page was created programmatically, to learn the article in its unique location you…
This web page was created programmatically, to learn the article in its authentic location you'll…