avoid the dashed ssh hostname class of security holes

Security fix: Disallow hostname starting with a dash, which would get
passed to ssh and be treated an option. This could be used by an attacker
who provides a crafted ssh url (for eg a git remote) to execute arbitrary
code via ssh -oProxyCommand.

No CVE has yet been assigned for this hole.
The same class of security hole recently affected git itself,
CVE-2017-1000117.

Method: Identified all places where ssh is run, by git grep '"ssh"'
Converted them all to use a SshHost, if they did not already, for
specifying the hostname.

SshHost was made a data type with a smart constructor, which rejects
hostnames starting with '-'.

Note that git-annex already contains extensive use of Utility.SafeCommand,
which fixes a similar class of problem where a filename starting with a
dash gets passed to a program which treats it as an option.

This commit was sponsored by Jochen Bartl on Patreon.
This commit is contained in:
Joey Hess 2017-08-17 22:11:31 -04:00
parent 25e55e7c2f
commit df11e54788
No known key found for this signature in database
GPG key ID: DB12DB0FF05F8F38
12 changed files with 106 additions and 61 deletions

View file

@ -48,6 +48,7 @@ import Utility.Rsync
import Utility.Tmp
import Logs.Remote
import Utility.Gpg
import Utility.SshHost
remote :: RemoteType
remote = RemoteType {
@ -158,8 +159,9 @@ rsyncTransport r gc
let rsyncpath = if "/~/" `isPrefixOf` path
then drop 3 path
else path
opts <- sshOptions ConsumeStdin (host, Nothing) gc []
return (rsyncShell $ Param "ssh" : opts, host ++ ":" ++ rsyncpath, AccessShell)
let sshhost = either error id (mkSshHost host)
opts <- sshOptions ConsumeStdin (sshhost, Nothing) gc []
return (rsyncShell $ Param "ssh" : opts, fromSshHost sshhost ++ ":" ++ rsyncpath, AccessShell)
othertransport = return ([], loc, AccessDirect)
noCrypto :: Annex a