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authorJeff King <>2018-04-30 07:25:25 (GMT)
committerJeff King <>2018-05-22 03:50:11 (GMT)
commit0383bbb9015898cbc79abd7b64316484d7713b44 (patch)
tree9dea4e74b490a09d29c653b5c29f7fb40589c4d8 /
parent42e6fde5c28150206956ea4be490d886c4ecbd68 (diff)
submodule-config: verify submodule names as paths
Submodule "names" come from the untrusted .gitmodules file, but we blindly append them to $GIT_DIR/modules to create our on-disk repo paths. This means you can do bad things by putting "../" into the name (among other things). Let's sanity-check these names to avoid building a path that can be exploited. There are two main decisions: 1. What should the allowed syntax be? It's tempting to reuse verify_path(), since submodule names typically come from in-repo paths. But there are two reasons not to: a. It's technically more strict than what we need, as we really care only about breaking out of the $GIT_DIR/modules/ hierarchy. E.g., having a submodule named "foo/.git" isn't actually dangerous, and it's possible that somebody has manually given such a funny name. b. Since we'll eventually use this checking logic in fsck to prevent downstream repositories, it should be consistent across platforms. Because verify_path() relies on is_dir_sep(), it wouldn't block "foo\..\bar" on a non-Windows machine. 2. Where should we enforce it? These days most of the .gitmodules reads go through submodule-config.c, so I've put it there in the reading step. That should cover all of the C code. We also construct the name for "git submodule add" inside the script. This is probably not a big deal for security since the name is coming from the user anyway, but it would be polite to remind them if the name they pick is invalid (and we need to expose the name-checker to the shell anyway for our test scripts). This patch issues a warning when reading .gitmodules and just ignores the related config entry completely. This will generally end up producing a sensible error, as it works the same as a .gitmodules file which is missing a submodule entry (so "submodule update" will barf, but "git clone --recurse-submodules" will print an error but not abort the clone. There is one minor oddity, which is that we print the warning once per malformed config key (since that's how the config subsystem gives us the entries). So in the new test, for example, the user would see three warnings. That's OK, since the intent is that this case should never come up outside of malicious repositories (and then it might even benefit the user to see the message multiple times). Credit for finding this vulnerability and the proof of concept from which the test script was adapted goes to Etienne Stalmans. Signed-off-by: Jeff King <>
Diffstat (limited to '')
1 files changed, 5 insertions, 0 deletions
diff --git a/ b/
index c0d0e9a..92750b9 100755
--- a/
+++ b/
@@ -228,6 +228,11 @@ Use -f if you really want to add it." >&2
+ if ! git submodule--helper check-name "$sm_name"
+ then
+ die "$(eval_gettext "'$sm_name' is not a valid submodule name")"
+ fi
# perhaps the path exists and is already a git repo, else clone it
if test -e "$sm_path"