So tell me. Do you think #curl should support plain SSH:// URLs to execute commands remotely?
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@bagder i get the feeling that this could be used for some nasty things. Or at least that or at least that this could make RCE easier in some setups where curl ist invoked with a user-supplied URL
@bagder how is it different from https://example.com/execute.api/shutdown%20-h%20now ? :)
but now: “ssh://host.example.com/command=shutdown -h now” instead of passing it with a custom -X
SSH is the transport in this case in stead of HTTPS. But otherwise, it is a ‘URL" that is requested.
For a command like “ps aux" it would make more sense in a way, as then you got a question and an answer (in plain/text or if there is a tool like ‘jq' with json mode).
You would have to come up with a proper SSH URL scheme though. But if one would do that it would fit curl better, yet another special option not so much.
@bagder I don't sense a particular demand for this feature from users.
@bagder My concern is that I don't think libssh2 uses `~/.ssh/config`. There are things that don't seem to fit in a URI. Jump hosts, identity files and agent forwarding would be the big ones from my usage. I usually use the config file to do that, but it also works on the ssh command line.
But if scp/sftp URIs already exist, maybe this would be fine?
@bagder it'd certainly be convenient sometimes... I'm far from qualified to talk about the implications of the increased attack surface area, but it kinda fits in the sense that for any long-lived tool or lib one expects gradual scope growth and hegemonisation. If the scope of curl is URI resolution, adding support for ssh scheme doesn't sound mad at all, and if it's not, where are the natural boundaries? I say do it, why not.
@bagder no. at the moment I expect curl to fetch and put things, not execute things.
also..
Assisted-by: an actual person <human@skunkwerks.at>
@bagder Seems out of scope to me, but it's your project and I'd have already made a different decision with regards to AI-generated submissions.
@bagder It would be fair only if local execution `curl --exec example.com/install` would be supported as well.
@bagder heck no. security smell & pinata for hackers. curl attracts enough scrutiny by bad actors as it is
@bagder speaking of which, I'd love to see grpc:// :)
@bagder no, because I am a strong proponent of the UNIX principle. Curl does one thing great, let ssh do that other job.
can I also remind you all that curl already speaks SCP and SFTP, in command line tool and library...
@bagder honestly I had no idea that it did this already. But I also wonder if it’s not growing beyond the “do one thing really well” philosophy. SSH and others in Curl feels very foreign to me.
@bagder adding 'ssh://' seems like it would introduce a fair amount of confusion. What features of an ssh client should curl itself implement? Does that implementation become some sort of ad hoc RPC protocol?
@bagder for me, that sounds like introducing a new kind of command line injection🫣
@bagder my impression is that the main scope of cURL is to fetch remote files (and push files to remotes that supports it).
From that point of view:
- support the SCP and SFTP protocols makes totally sense
- support remote execution of arbitrary command would fall under scope creep (and open too mant new cans of worms) (and also increase attack surface by giving opportunity for new creative abuse of the feature)
@bagder Hm, ssh can already to it: https://malcontentcomics.com/systemsboy/2006/07/send-remote-commands-via-ssh.html why mis-use curl then for this?
@bagder IMHO no; we have ssh already for that.
