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It's hidden in the sense that it creates ambiguity at the usage site. Compare with sudo: $ sudo ls 'file with spaces' ls: cannot access 'file with spa
by chubot 1y ago
It's hidden in the sense that it creates ambiguity at the usage site. Compare with sudo:
$ sudo ls 'file with spaces'
ls: cannot access 'file with spaces': No such file or directory
If ssh (and sh eval) did not accept multiple arguments, then this wouldn't even get to ls:
$ ssh example.com ls 'file with spaces'
ls: cannot access 'file': No such file or directory
ls: cannot access 'with': No such file or directory
ls: cannot access 'spaces': No such file or directory
Accepting argv is better. Or forcing this is better:
$ ssh example.com "ls 'file with spaces'"
So it's clear it's a single shell string.
Accepting a shell string is sometimes OK, but silently joining multiple args is useless, and insecure.
"RTFM" is not a good answer when security is involved.
- blueflow 1y agoThis stubborn attitude to refuse to consult the documentation at all and then expect the tool to work according to your preconceptions. Tools do have rough edges, if you don't want to learn about them, you will get bitten.
- chubot 1y agoIt’s a design mistake because it adds exactly zero functionality. The only thing it adds is insecurity. If the feature didn’t exist, then it wouldn’t need to be documented, and the world would be better.
- blueflow 1y ago[flagged]
- chubot 1y agoI think you missed the original point, which is that joining argv is equivalent to sh -c "$1 $2 $3 $4 ..." This is a form of shell injection, just like sh -c "ls $dir" because there's interpolation WITHOUT escaping. That should be: dir=$(escape "$dir") sh -c "ls $dir" Or simply ls "$dir" It's not my preconception -- it's a security problem. It's similar to ShellShock -- you can argue it was documented behavior, but it's still a security problem.
- blueflow 1y agoThe interpolation is not the security problem, the problem is the user not quoting their data. It's similar to curl CWE-93[1], where it was documented and in-use behavior and consequently was rejected as a security problem. Example for ssh: ssh host ls "$(quote "$dir")" [1] https://hackerone.com/reports/3133379 https://hackerone.com/reports/3133379
- Filligree 1y agoAnd yet it keeps happening. An engineering field grows up when people stop assigning blame, and start searching for solutions.
- blueflow 1y agoI just posted one way how to do it correctly. And research (aka: consulting the manpage) is an essential part of engineering. Doing that would also solve the problem.
- immibis 1y agoNo, the problem is that even if you quote your data, ssh unquotes it, so you have to quote it twice.
- nothrabannosir 1y agoThis statement can be true without contradicting anything anyone said upstream. Otherwise could use it to justify just about any bad design decision. Yes it’s in the docs. Yes people who carefully read the docs won’t get bitten. Also yes the design could be improved so people don’t make this mistake even without reading the docs. Both things can be true. We’re currently only talking about the latter, though.
- blueflow 1y ago> We’re currently only talking about the latter, though. I'm surprised, as i started this subthread explicitly to contest that the argv join is "hidden".
- immibis 1y agoThis very stubborn attitude to defend a bad design because it's documented. Bugs can be fixed.
- blueflow 1y agoIt is bad design, but your idea of something does not make anything non-conforming a bug.
- pwdisswordfishz 1y ago> Tools do have rough edges, if you don't want to learn about them, you will get bitten. I presume you consider INTERCAL to be a sanely designed programming language.
- blueflow 1y agoI'm not defending SSH's design, im criticizing peoples unwillingness to learn about the design as it is so they can work around it. Edit: The INTERCAL handbook is a great read, and despite being satirical, it is more detailed and qualified than the documentation of some other popular projects.