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add bug for security hole, with exploit details

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Joey Hess 2017-08-18 11:36:34 -04:00
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doc/bugs/dashed_ssh_hostname_security_hole.mdwn Normal file
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git-annex was vulnerable to the same class of security hole as
git's CVE-2017-1000117. In several cases, git-annex parses a repository
url, and uses it to generate a ssh command, with the hostname to ssh to
coming from the url. If the hostname it parses is something like
"-eProxyCommand=evil", this could result in arbitrary local code execution
via ssh.
I have not bothered to try to exploit the problem, and some details of URL
parsing may prevent the exploit working in some cases.
Exploiting this would involve the attacker tricking the victim into adding
a remote something like "ssh://-eProxyCommand=evil/blah".
One possible avenue for an attacker that avoids exposing the URL to the
user is to use initremote with a ssh remote, so embedding the URL in the
git-annex branch. Then the victim would enable it with enableremote.
This was fixed in version 6.20170818. Now there's a SshHost type that
is not allowed to start with a dash, and every invocation of git-annex is
in a function that takes a SshHost.
[[done]]
--[[Joey]]