34 lines
1.3 KiB
Markdown
34 lines
1.3 KiB
Markdown
Copied from an email I sent --[[Joey]]
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> Apart from restricting escape characters and characters with special
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> meanings to the filesystem (such as '/') or the version control system
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> (which may not cope with \n), why limit filenames at all?
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Suppose that git-add and git-commit a shell scripts:
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#!/bin/sh
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/opt/git/git commit $1
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#!/bin/sh
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/opt/git/git add $1
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Ok, that's crappy code, but git add and commit are only run by a trusted
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user at the command line, so it's hardly a security hole. (And frankly,
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I'm not all too impressed with the real shell code I've seen in git-*
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..)
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But there's no security problem until ikiwiki calls it on a filename
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that a web user made up. Now, suppose that ikiwiki decided to allow
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spaces in filenames. Nothing else new, just spaces. Of course, the above
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bad code will fail to add and commit such files.
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But it won't just fail, it can even expose private data. Suppose that $1
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is "foo.mdwn .ikiwiki/userdb foo.mdwn". Then the userdb, with its
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passwords and emails is committed, along with foo.mdwn.
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Moral: ikiwiki interfaces with code that was not necessarily written for the
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security context that ikiwiki runs in. Even the most innocuous filenames can do
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very unexpected things if you let the shell get ahold of them. Ikiwiki needs to
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sanitize the hell out of user inputted data before letting it anywhere near the
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shell.
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