You're a dev/ops guy, I'm an appsec security assessor. I think we just look for different things. Trust me, this isn't just common it's standard practice.
Actually I'm a CISSP and was CISO for a major financial web site for >5 years. I look at things the way you do, trust me.
It's just that I try to temper my security reflexes. Just because something might be potentially dangerous doesn't means it's automatically a bad idea.
Everybody runs development machines that can (a) be spoken to by machines with human-driven browsers and (b) can speak to other machines.
Indeed we do. And if you can't trust that environment to be private and secure, then you've got bigger problems than a web console. I wouldn't stop at shutting down SSH; I'd disconnect entirely. Hell, I'd quit.
If your dev environment is exposed to people who are malicious, you're screwed. Web console is not going to hurt you, because it's too late -- you've already been hacked.
I think you're contemplating the attack vectors from the wrong direction. We're not necessarily talking machines with open ports on internet facing IP addresses. Think about it from the other direction.
The root of the problem lies at the feet of a few factors:
A) HTTP is a relatively "trusted" protocol, which means you should be very, very careful about running local services over HTTP (on any port) that can do bad things™ to your computer.
B) http://localhost:3000/ isn't difficult to guess. If you know someone is a Rails developer, there is a good chance that embedding requests to that URL will hit a Rails dev environment at some point, and that's where this thing is going to end up running.
C) Eval, in general, is just about the right length of rope to hang yourself with. Use sparingly and with great respect for its ability to completely hose you. Passing anything sent as HTTP params to eval is just asking for it.
Knowing the above, consider an example like Patrick (patio11) outlines above.
Let's say this takes off and people start using it. This means that some percentage of Rails devs have this running. To attack their machines, I need only to trick their machine in to making a request to 'http://localhost:3000/malicious-string-here.
How might I accomplish that? I like Patrick's suggestion of an img tag src attribute. There are plenty of forums that treat img tags as safe, or provide some means of embedding images with arbitrary src attributes.
So let's say I head over to railsnewbforum.com and embed the malicious image in my sig. Then I start happily posting useful information in every thread on the board. Assuming this webconsole takes off, how long until a vulnerable dev hits a page with my malicious signature code and gets pwnd?
Can this be made safe? Probably to some degree, but then it would involve many of the security measures involved with using the Rails console over an ssh session or something similar.
Actually I'm a CISSP and was CISO for a major financial web site for >5 years. I look at things the way you do, trust me.
It's just that I try to temper my security reflexes. Just because something might be potentially dangerous doesn't means it's automatically a bad idea.
Everybody runs development machines that can (a) be spoken to by machines with human-driven browsers and (b) can speak to other machines.
Indeed we do. And if you can't trust that environment to be private and secure, then you've got bigger problems than a web console. I wouldn't stop at shutting down SSH; I'd disconnect entirely. Hell, I'd quit.
If your dev environment is exposed to people who are malicious, you're screwed. Web console is not going to hurt you, because it's too late -- you've already been hacked.