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dir-iterator: prevent top-level symlinks without FOLLOW_SYMLINKS

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When using the dir_iterator API, we first stat(2) the base path, and
then use that as a starting point to enumerate the directory's contents.

If the directory contains symbolic links, we will immediately die() upon
encountering them without the `FOLLOW_SYMLINKS` flag. The same is not
true when resolving the top-level directory, though.

As explained in a previous commit, this oversight in 6f054f9fb3
(builtin/clone.c: disallow `--local` clones with symlinks, 2022-07-28)
can be used as an attack vector to include arbitrary files on a victim's
filesystem from outside of the repository.

Prevent resolving top-level symlinks unless the FOLLOW_SYMLINKS flag is
given, which will cause clones of a repository with a symlink'd
"$GIT_DIR/objects" directory to fail.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Taylor Blau
2023-01-24 19:43:51 -05:00
committed by Junio C Hamano
parent cf8f6ce02a
commit bffc762f87
4 changed files with 56 additions and 5 deletions
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5
dir-iterator.h
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@ -61,6 +61,11 @@
* not the symlinks themselves, which is the default behavior. Broken
* symlinks are ignored.
*
* Note: setting DIR_ITERATOR_FOLLOW_SYMLINKS affects resolving the
* starting path as well (e.g., attempting to iterate starting at a
* symbolic link pointing to a directory without FOLLOW_SYMLINKS will
* result in an error).
*
* Warning: circular symlinks are also followed when
* DIR_ITERATOR_FOLLOW_SYMLINKS is set. The iteration may end up with
* an ELOOP if they happen and DIR_ITERATOR_PEDANTIC is set.