The variables `path` and `ce->name`, at write_entry(), usually have the
same contents, but that's not the case when using a checkout prefix or
writing to a tempfile. (In fact, `path` will be either empty or dirty
when writing to a tempfile.) Therefore, these variables cannot be used
interchangeably. In this sense, fix wrong uses of `path` in error
messages where it should really be `ce->name`, and add some regression
tests. (Note: there doesn't seem to be any misuse in the other way
around.)
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Before checking out a file, we have to confirm that all of its leading
components are real existing directories. And to reduce the number of
lstat() calls in this process, we cache the last leading path known to
contain only directories. However, when a path collision occurs (e.g.
when checking out case-sensitive files in case-insensitive file
systems), a cached path might have its file type changed on disk,
leaving the cache on an invalid state. Normally, this doesn't bring
any bad consequences as we usually check out files in index order, and
therefore, by the time the cached path becomes outdated, we no longer
need it anyway (because all files in that directory would have already
been written).
But, there are some users of the checkout machinery that do not always
follow the index order. In particular: checkout-index writes the paths
in the same order that they appear on the CLI (or stdin); and the
delayed checkout feature -- used when a long-running filter process
replies with "status=delayed" -- postpones the checkout of some entries,
thus modifying the checkout order.
When we have to check out an out-of-order entry and the lstat() cache is
invalid (due to a previous path collision), checkout_entry() may end up
using the invalid data and thrusting that the leading components are
real directories when, in reality, they are not. In the best case
scenario, where the directory was replaced by a regular file, the user
will get an error: "fatal: unable to create file 'foo/bar': Not a
directory". But if the directory was replaced by a symlink, checkout
could actually end up following the symlink and writing the file at a
wrong place, even outside the repository. Since delayed checkout is
affected by this bug, it could be used by an attacker to write
arbitrary files during the clone of a maliciously crafted repository.
Some candidate solutions considered were to disable the lstat() cache
during unordered checkouts or sort the entries before passing them to
the checkout machinery. But both ideas include some performance penalty
and they don't future-proof the code against new unordered use cases.
Instead, we now manually reset the lstat cache whenever we successfully
remove a directory. Note: We are not even checking whether the directory
was the same as the lstat cache points to because we might face a
scenario where the paths refer to the same location but differ due to
case folding, precomposed UTF-8 issues, or the presence of `..`
components in the path. Two regression tests, with case-collisions and
utf8-collisions, are also added for both checkout-index and delayed
checkout.
Note: to make the previously mentioned clone attack unfeasible, it would
be sufficient to reset the lstat cache only after the remove_subtree()
call inside checkout_entry(). This is the place where we would remove a
directory whose path collides with the path of another entry that we are
currently trying to check out (possibly a symlink). However, in the
interest of a thorough fix that does not leave Git open to
similar-but-not-identical attack vectors, we decided to intercept
all `rmdir()` calls in one fell swoop.
This addresses CVE-2021-21300.
Co-authored-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
If we encounter an error while checking out an explicit path, we print a
message to stderr but do not actually exit with a non-zero code. While
this is a plumbing command and the behavior goes all the way back to
33db5f4d90 (Add a "checkout-cache" command which does what the name
suggests., 2005-04-09), this is almost certainly an oversight:
- we _do_ return an exit code from checkout_file(); the caller just
never reads it
- errors while checking out all paths (with "-a") do result in a
non-zero exit code.
- it would be quite unusual not to use the exit code for an error,
as otherwise the caller has no idea the command failed except by
scraping stderr
To keep our tests simple and portable, we can use the most obvious
error: asking to checkout a path which is not in the index at all.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Use the i18n-specific test functions in test scripts for parseopt tests.
This issue was was introduced in v1.7.10.1-488-g54e6d:
54e6d i18n: parseopt: lookup help and argument translations when showing usage
and been broken under GETTEXT_POISON=YesPlease since.
Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
checkout-index loads the index before parsing options. Erroring out
is counterproductive at that point if the operator is hunting for a
command to recover useful data from the broken repository.
[jn: new commit message, tests]
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Junio C Hamano
Matheus Tavares
Johannes Schindelin
Jeff King
Jiang Xin
Nguyễn Thái Ngọc Duy