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a repo upon the deep

In reference to arbitrary code execution in various source control programs. Refer svn advisory. Remember A Fire Upon the Deep?

There’s some code archaeologists who dig up an artifact. They don’t know what it does, but it includes some instructions for how to unpack it. And so they follow the instructions. And they think they’re taking precautions to prevent it from doing bad stuff, but they screw up, and the evil AI is turned loose. And then bad stuff happens.

It’s funny how similar this is to today’s vulnerability. In theory, checking out a code repo should be a safe operation. All you’re doing is downloading some artifact from a server. Building the code, running the code, all that can be unsafe. But surely there’s no trouble to simply checking out some code?

Alas, a repo is not just a repo. Checking out a repo might require checking out other sub repos and external resources. And so a dumb read only artifact is actually a smart read/execute artifact. The artifact can’t be checked out without also interpreting some of its contents. And if interpreting happens to execute some unwanted shell commands... Bad stuff happens.

It’s a bug, and it’s fixed, but another lesson that nothing is ever simple when adding features. What looks like just a hostname over here could be interpreted as a shell command over there.

Posted 10 Aug 2017 19:38 by tedu Updated: 10 Aug 2017 19:38