We are about to make use of the `_which` function to address
CVE-2022-41953 by overriding Tcl/Tk's unsafe PATH lookup on Windows.
In preparation for that, let's move it close to the top of the file to
make sure that even early `exec` calls that happen during the start-up
of Git GUI benefit from the fix.
This commit is best viewed with `--color-moved`.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
We need these in `_which` and they should be defined before that
function's definition.
This commit is best viewed with `--color-moved`.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
The `is_Cygwin` function is used, among other things, to determine
how executables are discovered in the `PATH` list by the `_which` function.
We are about to change the behavior of the `_which` function on Windows
(but not Cygwin): On Windows, we want it to ignore empty elements of the
`PATH` instead of treating them as referring to the current directory
(which is a "legacy feature" according to
https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03,
but apparently not explicitly deprecated, the POSIX documentation is
quite unclear on that even if the Cygwin project itself considers it to
be deprecated: https://github.com/cygwin/cygwin/commit/fc74dbf22f5c).
This is important because on Windows, `exec` does something very unsafe
by default (unless we're running a Cygwin version of Tcl, which follows
Unix semantics).
However, we try to `exec` something _inside_ `is_Cygwin` to determine
whether we're running within Cygwin or not, i.e. before we determined
whether we need to handle `PATH` specially or not. That's a Catch-22.
Therefore, and because it is much cleaner anyway, use the
`$::tcl_platform(os)` value which is guaranteed to start with `CYGWIN_`
when running a Cygwin variant of Tcl/Tk, instead of executing `cygpath
--windir`.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
When looking up an executable via the `_which` function, Git GUI
imitates the `execlp()` strategy where the environment variable `PATH`
is interpreted as a list of paths in which to search.
For historical reasons, stemming from the olden times when it was
uncommon to download a lot of files from the internet into the current
directory, empty elements in this list are treated as if the current
directory had been specified.
Nowadays, of course, this treatment is highly dangerous as the current
directory often contains files that have just been downloaded and not
yet been inspected by the user. Unix/Linux users are essentially
expected to be very, very careful to simply not add empty `PATH`
elements, i.e. not to make use of that feature.
On Windows, however, it is quite common for `PATH` to contain empty
elements by mistake, e.g. as an unintended left-over entry when an
application was installed from the Windows Store and then uninstalled
manually.
While it would probably make most sense to safe-guard not only Windows
users, it seems to be common practice to ignore these empty `PATH`
elements _only_ on Windows, but not on other platforms.
Sadly, this practice is followed inconsistently between different
software projects, where projects with few, if any, Windows-based
contributors tend to be less consistent or even "blissful" about it.
Here is a non-exhaustive list:
Cygwin:
It specifically "eats" empty paths when converting path lists to
POSIX: https://github.com/cygwin/cygwin/commit/753702223c7d
I.e. it follows the common practice.
PowerShell:
It specifically ignores empty paths when searching the `PATH`.
The reason for this is apparently so self-evident that it is not
even mentioned here:
https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_environment_variables#path-information
I.e. it follows the common practice.
CMD:
Oh my, CMD. Let's just forget about it, nobody in their right
(security) mind takes CMD as inspiration. It is so unsafe by
default that we even planned on dropping `Git CMD` from Git for
Windows altogether, and only walked back on that plan when we
found a super ugly hack, just to keep Git's users secure by
default:
https://github.com/git-for-windows/MINGW-packages/commit/82172388bb51
So CMD chooses to hide behind the battle cry "Works as
Designed!" that all too often leaves users vulnerable. CMD is
probably the most prominent project whose lead you want to avoid
following in matters of security.
Win32 API (`CreateProcess()`)
Just like CMD, `CreateProcess()` adheres to the original design
of the path lookup in the name of backward compatibility (see
https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-createprocessw
for details):
If the file name does not contain a directory path, the
system searches for the executable file in the following
sequence:
1. The directory from which the application loaded.
2. The current directory for the parent process.
[...]
I.e. the Win32 API itself chooses backwards compatibility over
users' safety.
Git LFS:
There have been not one, not two, but three security advisories
about Git LFS executing executables from the current directory by
mistake. As part of one of them, a change was introduced to stop
treating empty `PATH` elements as equivalent to `.`:
https://github.com/git-lfs/git-lfs/commit/7cd7bb0a1f0d
I.e. it follows the common practice.
Go:
Go does not follow the common practice, and you can think about
that what you want:
https://github.com/golang/go/blob/go1.19.3/src/os/exec/lp_windows.go#L114-L135https://github.com/golang/go/blob/go1.19.3/src/path/filepath/path_windows.go#L108-L137
Git Credential Manager:
It tries to imitate Git LFS, but unfortunately misses the empty
`PATH` element handling. As of time of writing, this is in the
process of being fixed:
https://github.com/GitCredentialManager/git-credential-manager/pull/968
So now that we have established that it is a common practice to ignore
empty `PATH` elements on Windows, let's assess this commit's change
using Schneier's Five-Step Process
(https://www.schneier.com/crypto-gram/archives/2002/0415.html#1):
Step 1: What problem does it solve?
It prevents an entire class of Remote Code Execution exploits via
Git GUI's `Clone` functionality.
Step 2: How well does it solve that problem?
Very well. It prevents the attack vector of luring an unsuspecting
victim into cloning an executable into the worktree root directory
that Git GUI immediately executes.
Step 3: What other security problems does it cause?
Maybe non-security problems: If a project (ab-)uses the unsafe
`PATH` lookup. That would not only be unsafe, though, but
fragile in the first place because it would break when running
in a subdirectory. Therefore I would consider this a scenario
not worth keeping working.
Step 4: What are the costs of this measure?
Almost nil, except for the time writing up this commit message
;-)
Step 5: Given the answers to steps two through four, is the security
measure worth the costs?
Yes. Keeping Git's users Secure By Default is worth it. It's a
tiny price to pay compared to the damages even a single
successful exploit can cost.
So let's follow that common practice in Git GUI, too.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Windows updates.
* ds/maintenance-on-windows-fix:
git maintenance: avoid console window in scheduled tasks on Windows
win32: add a helper to run `git.exe` without a foreground window
Adjust to newer Term::ReadLine to prevent it from breaking
the interactive prompt code in send-email.
* jk/send-email-with-new-readline:
send-email: avoid creating more than one Term::ReadLine object
send-email: drop FakeTerm hack
Developer support to detect meaningless combination of options.
* rs/parse-opt-forbid-set-int-0-without-noneg:
parse-options: disallow negating OPTION_SET_INT 0
This fixes an occasional hang I see when running t4053 with
--verbose-log using dash.
Commit 1e3f26542a (diff --no-index: support reading from named pipes,
2023-07-05) added a test that "diff --no-index" will complain when
comparing a named pipe and a directory. The minimum we need to test this
is to mkfifo the pipe, and then run "git diff --no-index pipe some_dir".
But the test does one thing more: it spawns a background shell process
that opens the pipe for writing, like this:
{
(>pipe) &
} &&
This extra writer _could_ be useful if Git misbehaves and tries to open
the pipe for reading. Without the writer, Git would block indefinitely
and the test would never end. But since we do not have such a bug, Git
does not open the pipe and it is the writing process which will block
indefinitely, since there are no readers. The test addresses this by
running "kill $!" in a test_when_finished block. Since the writer should
be blocking forever, this kill command will reliably find it waiting.
However, this seems to be somewhat racy, in that the writing process
sometimes hangs around even after the "kill". In a normal run of the
test script without options, this doesn't have any effect; the
main test script completes anyway. But with --verbose-log, we spawn a
"tee" process that reads the script output, and it won't end until all
descriptors pointing to its input pipe are closed. And the background
process that is hanging around still has its stderr, etc, pointed into
that pipe.
You can reproduce the situation like this:
cd t
./t4053-diff-no-index.sh --verbose-log --stress
Let that run for a few minutes, and then you'll find that some of the
runs have hung. For example, at 11:53, I ran:
$ ps xk start o pid,start,command | grep tee | head
713459 11:48:06 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-9.out
713527 11:48:06 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-15.out
719434 11:48:07 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-1.out
728117 11:48:08 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-5.out
738738 11:48:09 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-31.out
739457 11:48:09 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-27.out
744432 11:48:10 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-21.out
744471 11:48:10 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-29.out
761961 11:48:12 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-0.out
812299 11:48:19 tee -a /home/peff/compile/git/t/test-results/t4053-diff-no-index.stress-8.out
All of these have been hung for several minutes. We can investigate one
and see that it's waiting to get EOF on its input:
$ strace -p 713459
strace: Process 713459 attached
read(0,
^C
Who else has that descriptor open?
$ lsof -a -p 713459 -d 0 +E
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
tee 713459 peff 0r FIFO 0,13 0t0 3943636 pipe 719203,sh,5w 719203,sh,7w 719203,sh,12w 719203,sh,13w
sh 719203 peff 5w FIFO 0,13 0t0 3943636 pipe 713459,tee,0r 719203,sh,7w 719203,sh,12w 719203,sh,13w
sh 719203 peff 7w FIFO 0,13 0t0 3943636 pipe 713459,tee,0r 719203,sh,5w 719203,sh,12w 719203,sh,13w
sh 719203 peff 12w FIFO 0,13 0t0 3943636 pipe 713459,tee,0r 719203,sh,5w 719203,sh,7w 719203,sh,13w
sh 719203 peff 13w FIFO 0,13 0t0 3943636 pipe 713459,tee,0r 719203,sh,5w 719203,sh,7w 719203,sh,12w
It's a shell, presumably a subshell spawned by the main script. Though
it may seem odd, having the same descriptor open several times is not
unreasonable (they're all basically the original stdout/stderr of the
script that has been copied). And they should all close when the process
exits. So what's it doing? Curiously, it will exit as soon as we strace
it:
$ strace -s 64 -p 719203
strace: Process 719203 attached
openat(AT_FDCWD, "pipe", O_WRONLY|O_CREAT|O_TRUNC, 0666) = -1 ENOENT (No such file or directory)
write(2, "./t4053-diff-no-index.sh: 7: eval: ", 35) = 35
write(2, "cannot create pipe: Directory nonexistent", 41) = 41
write(2, "\n", 1) = 1
exit_group(2) = ?
+++ exited with 2 +++
I think what happens is this:
- it is blocking in the openat() call for the pipe, as we expect (so
this is definitely the backgrounded subshell mentioned above)
- strace sends signals (probably STOP/CONT); those cause the kernel to
stop blocking, but libc will restart the system call automatically
- by this time, the "pipe" fifo is gone, so we'll actually try to
create a regular file. But of course the surrounding directory is
gone, too! So we get ENOENT, and then exit as normal.
So the blocking is something we expect to happen. But what we didn't
expect is for the process to still exist at all! It should have been
killed earlier when the parent process called "kill", but it wasn't. And
we can't catch the race at this point, because it happened much earlier.
One can guess, though, that there is some race with the shell setting up
the signal handling in the backgrounded subshell, and possibly blocking
or ignoring signals at the time that the "kill" is received. Curiously,
the race does not seem to happen if I use "bash" instead of "dash", so
presumably bash's setup here is more atomic.
One fix might be to try killing the subshell more aggressively, either
using SIGKILL, or looping on kill/wait. But that seems complex and
likely to introduce new problems/races. Instead, we can observe that the
writer is not needed at all. Git will notice the pipe via stat() before
it is ever opened. So we can simply drop the writer subshell entirely.
If we ever changed Git to open the path and fstat() it, this would
result in the test hanging. But we're not likely to do that. After all,
we have to stat() paths to see if they are openable at all (e.g., it
could be a directory), so this seems like a low risk. And anybody who
does make such a change will immediately see the issue, as Git would
hang consistently.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The test 'diff --no-index reads from pipes' starts a couple of
background processes that write to the pipes that are passed to "diff
--no-index". If the test passes then we expect these processes to exit
as all their output will have been read. However if the test fails
then we want to make sure they do not hang about on the users machine
and the test remembers they should be killed by calling
test_when_finished "! kill $!"
after each background process is created. Unfortunately there is a
race where test_when_finished may run before the background process
exits even when all its output has been read resulting in the kill
command succeeding which causes the test to fail. Fix this by ignoring
the exit status of the kill command. If the diff is successful we
could instead wait for the background process to exit and check their
status but that feels like it is testing the platform's printf
implementation rather than git's code.
Reported-by: Jeff King <peff@peff.net>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Originally introduced as `core.useBuiltinFSMonitor` in Git for Windows
and developed, improved and stabilized there, the built-in FSMonitor
only made it into upstream Git (after unnecessarily long hemming and
hawing and throwing overly perfectionist style review sticks into the
spokes) as `core.fsmonitor = true`.
In Git for Windows, with this topic branch, we re-introduce the
now-obsolete config setting, with warnings suggesting to existing users
how to switch to the new config setting, with the intention to
ultimately drop the patch at some stage.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This topic branch re-adds the deprecated --stdin/-z options to `git
reset`. Those patches were overridden by a different set of options in
the upstream Git project before we could propose `--stdin`.
We offered this in MinGit to applications that wanted a safer way to
pass lots of pathspecs to Git, and these applications will need to be
adjusted.
Instead of `--stdin`, `--pathspec-from-file=-` should be used, and
instead of `-z`, `--pathspec-file-nul`.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
A fix for calling `vim` in Windows Terminal caused a regression and was
reverted. We partially un-revert this, to get the fix again.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This patch introduces support to set special NTFS attributes that are
interpreted by the Windows Subsystem for Linux as file mode bits, UID
and GID.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
With this patch, Git for Windows works as intended on mounted APFS
volumes (where renaming read-only files would fail).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
These are Git for Windows' Git GUI and gitk patches. We will have to
decide at some point what to do about them, but that's a little lower
priority (as Git GUI seems to be unmaintained for the time being, and
the gitk maintainer keeps a very low profile on the Git mailing list,
too).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This is the recommended way on GitHub to describe policies revolving around
security issues and about supported versions.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Rather than using private IFTTT Applets that send mails to this
maintainer whenever a new version of a Git for Windows component was
released, let's use the power of GitHub workflows to make this process
publicly visible.
This workflow monitors the Atom/RSS feeds, and opens a ticket whenever a
new version was released.
Note: Bash sometimes releases multiple patched versions within a few
minutes of each other (i.e. 5.1p1 through 5.1p4, 5.0p15 and 5.0p16). The
MSYS2 runtime also has a similar system. We can address those patches as
a group, so we shouldn't get multiple issues about them.
Note further: We're not acting on newlib releases, OpenSSL alphas, Perl
release candidates or non-stable Perl releases. There's no need to open
issues about them.
Co-authored-by: Matthias Aßhauer <mha1993@live.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Git documentation refers to $HOME and $XDG_CONFIG_HOME often, but does not specify how or where these values come from on Windows where neither is set by default. The new documentation reflects the behavior of setup_windows_environment() in compat/mingw.c.
Signed-off-by: Alejandro Barreto <alejandro.barreto@ni.com>
Git for Windows accepts pull requests; Core Git does not. Therefore we
need to adjust the template (because it only matches core Git's
project management style, not ours).
Also: direct Git for Windows enhancements to their contributions page,
space out the text for easy reading, and clarify that the mailing list
is plain text, not HTML.
Signed-off-by: Philip Oakley <philipoakley@iee.org>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Getting started contributing to Git can be difficult on a Windows
machine. CONTRIBUTING.md contains a guide to getting started, including
detailed steps for setting up build tools, running tests, and
submitting patches to upstream.
[includes an example by Pratik Karki how to submit v2, v3, v4, etc.]
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
The Git project followed suite and added their Code of Conduct, based on
the Contributors' Covenant v1.4.
We edit it slightly to reflect Git for Windows' particulars.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
The Git for Windows project has grown quite complex over the years,
certainly much more complex than during the first years where the
`msysgit.git` repository was abusing Git for package management purposes
and the `git/git` fork was called `4msysgit.git`.
Let's describe the status quo in a thorough way.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Reintroduce the 'core.useBuiltinFSMonitor' config setting (originally added
in 0a756b2a25 (fsmonitor: config settings are repository-specific,
2021-03-05)) after its removal from the upstream version of FSMonitor.
Upstream, the 'core.useBuiltinFSMonitor' setting was rendered obsolete by
"overloading" the 'core.fsmonitor' setting to take a boolean value. However,
several applications (e.g., 'scalar') utilize the original config setting,
so it should be preserved for a deprecation period before complete removal:
* if 'core.fsmonitor' is a boolean, the user is correctly using the new
config syntax; do not use 'core.useBuiltinFSMonitor'.
* if 'core.fsmonitor' is unspecified, use 'core.useBuiltinFSMonitor'.
* if 'core.fsmonitor' is a path, override and use the builtin FSMonitor if
'core.useBuiltinFSMonitor' is 'true'; otherwise, use the FSMonitor hook
indicated by the path.
Additionally, for this deprecation period, advise users to switch to using
'core.fsmonitor' to specify their use of the builtin FSMonitor.
Signed-off-by: Victoria Dye <vdye@github.com>
The `--stdin` option was a well-established paradigm in other commands,
therefore we implemented it in `git reset` for use by Visual Studio.
Unfortunately, upstream Git decided that it is time to introduce
`--pathspec-from-file` instead.
To keep backwards-compatibility for some grace period, we therefore
reinstate the `--stdin` option on top of the `--pathspec-from-file`
option, but mark it firmly as deprecated.
Helped-by: Victoria Dye <vdye@github.com>
Helped-by: Matthew John Cheetham <mjcheetham@outlook.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
In e3f7e01b50 (Revert "editor: save and reset terminal after calling
EDITOR", 2021-11-22), we reverted the commit wholesale where the
terminal state would be saved and restored before/after calling an
editor.
The reverted commit was intended to fix a problem with Windows Terminal
where simply calling `vi` would cause problems afterwards.
To fix the problem addressed by the revert, but _still_ keep the problem
with Windows Terminal fixed, let's revert the revert, with a twist: we
restrict the save/restore _specifically_ to the case where `vi` (or
`vim`) is called, and do not do the same for any other editor.
This should still catch the majority of the cases, and will bridge the
time until the original patch is re-done in a way that addresses all
concerns.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
The `xutftowcs_path` function canonicalizes absolute paths using GetFullPathNameW.
This canonicalization may change the length of the string (e.g. getting rid of \.\),
which breaks callers that pass the template string in a strbuf and expect the
length of the string to remain the same.
In my particular case, the tmp-objdir code is passing a strbuf to mkdtemp and is
breaking since the strbuf.len is no longer synchronized with strlen(strbuf.buf).
Signed-off-by: Neeraj K. Singh <neerajsi@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Previously, we did not install any handler for Ctrl+C, but now we really
want to because the MSYS2 runtime learned the trick to call the
ConsoleCtrlHandler when Ctrl+C was pressed.
With this, hitting Ctrl+C while `git log` is running will only terminate
the Git process, but not the pager. This finally matches the behavior on
Linux and on macOS.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
