subrepo: set GIT_ALLOW_PROTOCOL to limit git clone protocols (SEC) stable
authorMateusz Kwapich <mitrandir@fb.com>
Sun, 20 Mar 2016 21:52:21 -0700
branchstable
changeset 28658 34d43cb85de8
parent 28657 b9714d958e89
child 28659 197eed39e3d5
subrepo: set GIT_ALLOW_PROTOCOL to limit git clone protocols (SEC) CVE-2016-3068 (1/1) Git's git-remote-ext remote helper provides an ext:: URL scheme that allows running arbitrary shell commands. This feature allows implementing simple git smart transports with a single shell shell command. However, git submodules could clone arbitrary URLs specified in the .gitmodules file. This was reported as CVE-2015-7545 and fixed in git v2.6.1. However, if a user directly clones a malicious ext URL, the git client will still run arbitrary shell commands. Mercurial is similarly effected. Mercurial allows specifying git repositories as subrepositories. Git ext:: URLs can be specified as Mercurial subrepositories allowing arbitrary shell commands to be run on `hg clone ...`. The Mercurial community would like to thank Blake Burkhart for reporting this issue. The description of the issue is copied from Blake's report. This commit changes submodules to pass the GIT_ALLOW_PROTOCOL env variable to git commands with the same list of allowed protocols that git submodule is using. When the GIT_ALLOW_PROTOCOL env variable is already set, we just pass it to git without modifications.
mercurial/subrepo.py
tests/test-subrepo-git.t
--- a/mercurial/subrepo.py	Wed Mar 16 17:30:26 2016 -0700
+++ b/mercurial/subrepo.py	Sun Mar 20 21:52:21 2016 -0700
@@ -1383,6 +1383,11 @@
         are not supported and very probably fail.
         """
         self.ui.debug('%s: git %s\n' % (self._relpath, ' '.join(commands)))
+        if env is None:
+            env = os.environ.copy()
+        # fix for Git CVE-2015-7545
+        if 'GIT_ALLOW_PROTOCOL' not in env:
+            env['GIT_ALLOW_PROTOCOL'] = 'file:git:http:https:ssh'
         # unless ui.quiet is set, print git's stderr,
         # which is mostly progress and useful info
         errpipe = None
--- a/tests/test-subrepo-git.t	Wed Mar 16 17:30:26 2016 -0700
+++ b/tests/test-subrepo-git.t	Sun Mar 20 21:52:21 2016 -0700
@@ -1132,4 +1132,36 @@
   ? s/foobar.orig
   ? s/snake.python.orig
 
+test for Git CVE-2016-3068
+  $ hg init malicious-subrepository
+  $ cd malicious-subrepository
+  $ echo "s = [git]ext::sh -c echo% pwned% >&2" > .hgsub
+  $ git init s
+  Initialized empty Git repository in $TESTTMP/tc/malicious-subrepository/s/.git/
+  $ cd s
+  $ git commit --allow-empty -m 'empty'
+  [master (root-commit) 153f934] empty
   $ cd ..
+  $ hg add .hgsub
+  $ hg commit -m "add subrepo"
+  $ cd ..
+  $ env -u GIT_ALLOW_PROTOCOL hg clone malicious-subrepository malicious-subrepository-protected
+  Cloning into '$TESTTMP/tc/malicious-subrepository-protected/s'...
+  fatal: transport 'ext' not allowed
+  updating to branch default
+  cloning subrepo s from ext::sh -c echo% pwned% >&2
+  abort: git clone error 128 in s (in subrepo s)
+  [255]
+
+whitelisting of ext should be respected (that's the git submodule behaviour)
+  $ env GIT_ALLOW_PROTOCOL=ext hg clone malicious-subrepository malicious-subrepository-clone-allowed
+  Cloning into '$TESTTMP/tc/malicious-subrepository-clone-allowed/s'...
+  pwned
+  fatal: Could not read from remote repository.
+  
+  Please make sure you have the correct access rights
+  and the repository exists.
+  updating to branch default
+  cloning subrepo s from ext::sh -c echo% pwned% >&2
+  abort: git clone error 128 in s (in subrepo s)
+  [255]