Composer leaks contents of tokens configured as GitHub OAuth tokens

ddamienwebdev about 11 hours ago 20 commentsRead Article on github.com

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Discussion (20 Comments)Read Original on HackerNews

damienwebdev•about 11 hours ago

I was the reporter on this one. If you have Github Actions in your organization, disable them immediately if you're unsure which version of composer your Github Actions run.

securesaml•about 1 hour ago

Nice find. The tokens being leaked in actions log was not one of the security implications I thought of when they released the feature.

How many other actions/libraries do you think are vulnerable?

ammar2•about 3 hours ago

Could you elaborate on this bit on why Github's secret masking doesn't work here:

> GitHub Actions' built-in secret masker matches registered values as exact substrings. When the exception message is rendered by Symfony Console it may wrap, embed in In BaseIO.php line N: framing, or interleave with ANSI control sequences. So the masker does not redact, and the plaintext token reaches the log.

What does this log rendering look like such that the token from that code snippet becomes interleaved enough to not be a substring match?

I'm not familiar with composer/Symfony but I would expect something like:

  Line 34: Foo bar
  Line 34: <red>Foo bar</red>

jacobrussell•about 2 hours ago

From what I can tell Symfony wraps these errors in a styled error block so it messes with GitHub's masking. For example, newlines breaking up the token are apparently enough to trick the masker since it's not a substring anymore.

For your example:

Line 34: <red>ghs_fdsafdsarewqfdsa...</red>

Is probably long enough in most cases to break to a new line.

Also, those blocks get "interleaved" like this:

<red>ghs_fdsafdsarewqfdsafdsa</red>

<red>fdsardsardsafdsafs......</red>

So there are now </red>'s within the token, also breaking the substring matching.

This is kind of eye-opening for me -- I have never thought about how styled output like this could cause logging leakages.

ammar2•about 2 hours ago

Aah, the newlines were the thing I was missing. That makes sense then.

semi-extrinsic•about 3 hours ago

Not immediately clear to me, is this limited to ghu_xxx type OAUTH tokens? And it's only relevant for PHP projects that use composer in GHA?

securesaml•about 1 hour ago

It's limited to ghs_ (server to server token's), that have the new format enabled: https://github.blog/changelog/2026-04-24-notice-about-upcomi... (and actions that use the vulnerable package)

This include's the GITHUB_TOKEN that is builtin within a actions jobs.

jacobrussell•about 2 hours ago

That's my understanding. This seems to only effect PHP projects that use Composer in GitHub actions. Examples being usage of shivammathur/setup-php and or php-actions/composer.

Normal_gaussian•about 3 hours ago

GHA have always been a PITA for any serious DevOps; it's quite clear they were designed to integrate in 7 lines of code and then tell everyone who complains that they're doing it wrong.

This does not surprise me.

freedomben•about 2 hours ago

It is a PITA, but that can be significantly improved IMHO if you just write shell script wrappers for your tasks. Not only does it make it easier to run CI locally, but it also makes it so much easier to move platforms in the future.

When the GH action YAML is just invoking shell scripts, I find it quite pleasant to use

datadrivenangel•about 2 hours ago

You've perfectly described how microsoft operates and how github actions is apparently based on AzureDevOps pipelines.

youre-wrong3•about 2 hours ago

No. GHA has always been trash before MS got to it. A lot of GHA influenced ADO.

ShowalkKama•about 1 hour ago

I may be silly but why would you ever want to validate the structure of an opaque authentication key? Couldn't you just hit an harmless endpoint (e.g. /rate_limit) to see if it returns 401 or not?

euph0ria•about 2 hours ago

What is the security implication for private repos?

Normal_gaussian•about 1 hour ago

If everyone that can read the logs are people who can read the secrets, then nothing. If there are any log readers who should be be secret readers, its a potentially exposed secret.

esafak•about 3 hours ago

The title suggests it is a Github issue but really it is https://github.com/composer/composer no? I would edit the title for clarity.

darkwater•about 2 hours ago

Yes, it's a Composer issue (which is a PHP dependencies manager) with the new format of GITHUB_TOKEN.

It's not an issue in GHA itself, this time. But if you are a composer user in GH, you should definitely be warned (and worried).

incomplete•about 3 hours ago

it's not super clear, but that's my read as well... i think i can start lowering my panic levels now.

h1fra•about 2 hours ago

the title is incorrect; it's not a github error but php composer's github action. cc @dang before people freak out

shimman•about 1 hour ago

@'ing doesn't work on hackernews, emailing does tho.