4 ms·
The issue is ruby's `system` method which interprets args in the shell. They should have used `popen` instead. This is similar to python's subprocess with `sh
by tantalor 6y ago
The issue is ruby's `system` method which interprets args in the shell.
They should have used `popen` instead.
This is similar to python's subprocess with `shell=True`
Edit: I'm wrong!
> ls-remote has a parameter --upload-pack which can be used to execute a new shell
- xucheng 6y agoI don't believe this is the case. [1] pry(main)> system "echo", "$(whoami)" $(whoami) => true [2] pry(main)> system "git", "ls-remote", "--upload-pack=$(whoami)", "HEAD" $(whoami) 'HEAD': USERNAME: command not found fatal: Could not read from remote repository. Please make sure you have the correct access rights and the repository exists. => false
- deleted 6y ago[deleted]
- deleted 6y ago[deleted]
- tantalor 6y agoOh, that's very silly. Don't do that!
- xucheng 6y agoI think I understand why this happens. See https://news.ycombinator.com/item?id=26885103 https://news.ycombinator.com/item?id=26885103
- kirby88 6y agoI had the same reaction as you... it looks like the vulnerability is coming from git, that's a very dangerous behavior.
- xucheng 6y agoI think I understand why this is happening. This is not an issue that argument parsing in git goes wrong. But instead, the `--upload-pack=` instructs git to run certain command in the remote server. In my above example (`system "git", "ls-remote", "--upload-pack=$(whoami)", "HEAD"`), HEAD is interpreted as a local file based git server. As such, the command is executed in the same machine.
- kirby88 6y agoI don't think so, you just forgot to add the remote server address. If you run `system "git", "ls-remote", " --upload-pack=$(touch hello) git@github.com:torvalds/linux.git", "HEAD"` it will fetch the remote server but still create the file on the local machine.
- xucheng 6y agoIn your example, `HEAD` is the server address, which is interpreted as a local file. `$(touch hello) git@github.com:torvalds/linux.git` is the command to be run in the remote (locally in this case). It will not connect to the server in GitHub. P.S. it seems that you have an extra space before `--upload-pack`.