This topic branch extends the protections introduced for Git GUI's
CVE-2022-41953 to cover `gitk`, too.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This topic branch fixes a vulnerability in Git GUI's "clone" feature
(tracked as CVE-2022-41953) that was graded with a CVSS Score 8.6/10
(high).
These patches were backported to Git GUI in
https://github.com/prati0100/git-gui/pull/85
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Just like CVE-2022-41953 for Git GUI, there exists a vulnerability of
`gitk` where it looks for `taskkill.exe` in the current directory before
searching `PATH`.
Note that the many `exec git` calls are unaffected, due to an obscure
quirk in Tcl's `exec` function. Typically, `git.exe` lives next to
`wish.exe` (i.e. the program that is run to execute `gitk` or Git GUI)
in Git for Windows, and that is the saving grace for `git.exe because
`exec` searches the directory where `wish.exe` lives even before the
current directory, according to
https://www.tcl-lang.org/man/tcl/TclCmd/exec.htm#M24:
If a directory name was not specified as part of the application
name, the following directories are automatically searched in
order when attempting to locate the application:
The directory from which the Tcl executable was loaded.
The current directory.
The Windows 32-bit system directory.
The Windows home directory.
The directories listed in the path.
The same is not true, however, for `taskkill.exe`: it lives in the
Windows system directory (never mind the 32-bit, Tcl's documentation is
outdated on that point, it really means `C:\Windows\system32`).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
As per https://www.tcl.tk/man/tcl8.6/TclCmd/exec.html#M23, Tcl's `exec`
function goes out of its way to imitate the highly dangerous path lookup
of `cmd.exe`, but _of course_ only on Windows:
If a directory name was not specified as part of the application
name, the following directories are automatically searched in
order when attempting to locate the application:
The directory from which the Tcl executable was loaded.
The current directory.
The Windows 32-bit system directory.
The Windows home directory.
The directories listed in the path.
The dangerous part is the second item, of course: `exec` _prefers_
executables in the current directory to those that are actually in the
`PATH`.
It is almost as if people wanted to Windows users vulnerable,
specifically.
To avoid that, Git GUI already has the `_which` function that does not
imitate that dangerous practice when looking up executables in the
search path.
However, Git GUI currently fails to use that function e.g. when trying to
execute `aspell` for spell checking.
That is not only dangerous but combined with Tcl's unfortunate default
behavior and with the fact that Git GUI tries to spell-check a
repository just after cloning, leads to a critical Remote Code Execution
vulnerability.
Let's override both `exec` and `open` to always use `_which` instead of
letting Tcl perform the path lookup, to prevent this attack vector.
This addresses CVE-2022-41953.
For more details, see
https://github.com/git-for-windows/git/security/advisories/GHSA-v4px-mx59-w99c
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
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>
Fixes to code that parses the todo file used in "rebase -i".
* pw/rebase-i-parse-fix:
rebase -i: fix parsing of "fixup -C<commit>"
rebase -i: match whole word in is_command()
Various fix-ups on HTTP tests.
* jk/http-test-fixes:
t5559: make SSL/TLS the default
t5559: fix test failures with LIB_HTTPD_SSL
t/lib-httpd: enable HTTP/2 "h2" protocol, not just h2c
t/lib-httpd: respect $HTTPD_PROTO in expect_askpass()
t5551: drop curl trace lines without headers
t5551: handle v2 protocol in cookie test
t5551: simplify expected cookie file
t5551: handle v2 protocol in upload-pack service test
t5551: handle v2 protocol when checking curl trace
t5551: stop forcing clone to run with v0 protocol
t5551: handle HTTP/2 when checking curl trace
t5551: lower-case headers in expected curl trace
t5551: drop redundant grep for Accept-Language
t5541: simplify and move "no empty path components" test
t5541: stop marking "used receive-pack service" test as v0 only
t5541: run "used receive-pack service" test earlier
The format.attach configuration variable lacked a way to override a
value defined in a lower-priority configuration file (e.g. the
system one) by redefining it in a higher-priority configuration
file. Now, setting format.attach to an empty string means show the
patch inline in the e-mail message, without using MIME attachment.
This is a backward incompatible change.
* jc/countermand-format-attach:
format.attach: allow empty value to disable multi-part messages
sscanf(3) used in "git symbolic-ref --short" implementation found
to be not working reliably on macOS in UTF-8 locales. Rewrite the
code to avoid sscanf() altogether to work it around.
* jk/shorten-unambiguous-ref-wo-sscanf:
shorten_unambiguous_ref(): avoid sscanf()
shorten_unambiguous_ref(): use NUM_REV_PARSE_RULES constant
shorten_unambiguous_ref(): avoid integer truncation
The credential subsystem learned that a password may have an
explicit expiration.
* mh/credential-password-expiry:
credential: new attribute password_expiry_utc
"git archive HEAD^{tree}" records the paths with the current
timestamp in the archive, making it harder to obtain a stable
output. The command learned the --mtime option to specify an
arbitrary timestamp (e.g. --mtime="@0 +0000" for the epoch).
* rs/archive-mtime:
archive: add --mtime
Remove leftover and unused code.
* tb/drop-dir-iterator-follow-symlink-bit:
t0066: drop setup of "dir5"
dir-iterator: drop unused `DIR_ITERATOR_FOLLOW_SYMLINKS`
The "diff" drivers specified by the "diff" attribute attached to
paths can now specify which algorithm (e.g. histogram) to use.
* jc/diff-algo-attribute:
diff: teach diff to read algorithm from diff driver
diff: consolidate diff algorithm option parsing
An invalid label or ref in the "rebase -i" todo file used to
trigger an runtime error. SUch an error is now diagnosed while the
todo file is parsed.
* pw/rebase-i-validate-labels-early:
rebase -i: check labels and refs when parsing todo list
When a comment describing how each test file should start was added in
commit [1], it was the second comment of t/test-lib.sh. The comment
describes how variable "test_description" is supposed to be assigned at
the top of each test file and how "test-lib.sh" should be used by
sourcing it. However, even in [1], the comment was ten lines away from
the usage of the variable by test-lib.sh. Since then, the comment has
drifted away both from the top of the file and from the usage of the
variable. The comment just sits in the middle of the initialization of
the test library, surrounded by unrelated code, almost one hundred lines
away from the usage of "test_description".
Nobody has noticed this drift during evolution of test-lib.sh, which
suggests that this comment has outlived its usefulness. The assignment
of "test_description", sourcing of "test-lib.sh" by tests, and the
process of writing tests in general are described in detail in
"t/README". So drop the obsolete comment.
An alternative solution could be to move the comment either to the top
of the file, or down to the usage of variable "test_description".
[1] e1970ce43a ("[PATCH 1/2] Test framework take two.", 2005-05-13)
Signed-off-by: Andrei Rybak <rybak.a.v@gmail.com>
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>
Previously, we interpolated paths in config variables that start with a
forward-slash as relative to the runtime prefix. This was not portable
and has been replaced with `%(prefix)/`.
Let's warn users when they use the now-deprecated form.
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>
The Makefile target `install-mingit-test-artifacts` simply copies stuff
and things directly into a MinGit directory, including an init.bat
script to set everything up so that the tests can be run in a cmd
window.
Sadly, Git's test suite still relies on a Perl interpreter even if
compiled with NO_PERL=YesPlease. We punt for now, installing a small
script into /usr/bin/perl that hands off to an existing Perl of a Git
for Windows SDK.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
On Windows, the current working directory is pretty much guaranteed to
contain a colon. If we feed that path to CVS, it mistakes it for a
separator between host and port, though.
This has not been a problem so far because Git for Windows uses MSYS2's
Bash using a POSIX emulation layer that also pretends that the current
directory is a Unix path (at least as long as we're in a shell script).
However, that is rather limiting, as Git for Windows also explores other
ports of other Unix shells. One of those is BusyBox-w32's ash, which is
a native port (i.e. *not* using any POSIX emulation layer, and certainly
not emulating Unix paths).
So let's just detect if there is a colon in $PWD and punt in that case.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Git for Windows uses MSYS2's Bash to run the test suite, which comes
with benefits but also at a heavy price: on the plus side, MSYS2's
POSIX emulation layer allows us to continue pretending that we are on a
Unix system, e.g. use Unix paths instead of Windows ones, yet this is
bought at a rather noticeable performance penalty.
There *are* some more native ports of Unix shells out there, though,
most notably BusyBox-w32's ash. These native ports do not use any POSIX
emulation layer (or at most a *very* thin one, choosing to avoid
features such as fork() that are expensive to emulate on Windows), and
they use native Windows paths (usually with forward slashes instead of
backslashes, which is perfectly legal in almost all use cases).
And here comes the problem: with a $PWD looking like, say,
C:/git-sdk-64/usr/src/git/t/trash directory.t5813-proto-disable-ssh
Git's test scripts get quite a bit confused, as their assumptions have
been shattered. Not only does this path contain a colon (oh no!), it
also does not start with a slash.
This is a problem e.g. when constructing a URL as t5813 does it:
ssh://remote$PWD. Not only is it impossible to separate the "host" from
the path with a $PWD as above, even prefixing $PWD by a slash won't
work, as /C:/git-sdk-64/... is not a valid path.
As a workaround, detect when $PWD does not start with a slash on
Windows, and simply strip the drive prefix, using an obscure feature of
Windows paths: if an absolute Windows path starts with a slash, it is
implicitly prefixed by the drive prefix of the current directory. As we
are talking about the current directory here, anyway, that strategy
works.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
When t5605 tries to verify that files are hardlinked (or that they are
not), it uses the `-links` option of the `find` utility.
BusyBox' implementation does not support that option, and BusyBox-w32's
lstat() does not even report the number of hard links correctly (for
performance reasons).
So let's just switch to a different method that actually works on
Windows.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
While it may seem super convenient to some old Unix hands to simpy
require Perl to be available when running the test suite, this is a
major hassle on Windows, where we want to verify that Perl is not,
actually, required in a NO_PERL build.
As a super ugly workaround, we "install" a script into /usr/bin/perl
reading like this:
#!/bin/sh
# We'd much rather avoid requiring Perl altogether when testing
# an installed Git. Oh well, that's why we cannot have nice
# things.
exec c:/git-sdk-64/usr/bin/perl.exe "$@"
The problem with that is that BusyBox assumes that the #! line in a
script refers to an executable, not to a script. So when it encounters
the line #!/usr/bin/perl in t5532's proxy-get-cmd, it barfs.
Let's help this situation by simply executing the Perl script with the
"interpreter" specified explicitly.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
At some stage, t5003-archive-zip wants to add a file that is not ASCII.
To that end, it uses /bin/sh. But that file may actually not exist (it
is too easy to forget that not all the world is Unix/Linux...)! Besides,
we already have perfectly fine binary files intended for use solely by
the tests. So let's use one of them instead.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
When running with BusyBox, we will want to avoid calling executables on
the PATH that are implemented in BusyBox itself.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
The -W option is only understood by MSYS2 Bash's pwd command. We already
make sure to override `pwd` by `builtin pwd -W` for MINGW, so let's not
double the effort here.
This will also help when switching the shell to another one (such as
BusyBox' ash) whose pwd does *not* understand the -W option.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Traditionally, Git for Windows' SDK uses Bash as its default shell.
However, other Unix shells are available, too. Most notably, the Win32
port of BusyBox comes with `ash` whose `pwd` command already prints
Windows paths as Git for Windows wants them, while there is not even a
`builtin` command.
Therefore, let's be careful not to override `pwd` unless we know that
the `builtin` command is available.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
To verify that the symlink is resolved correctly, we use the fact that
`git.exe` is a native Win32 program, and that `git.exe config -f <path>`
therefore uses the native symlink resolution.
Signed-off-by: Bert Belder <bertbelder@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
BusyBox-w32 is a true Win32 application, i.e. it does not come with a
POSIX emulation layer.
That also means that it does *not* use the Unix convention of separating
the entries in the PATH variable using colons, but semicolons.
However, there are also BusyBox ports to Windows which use a POSIX
emulation layer such as Cygwin's or MSYS2's runtime, i.e. using colons
as PATH separators.
As a tell-tale, let's use the presence of semicolons in the PATH
variable: on Unix, it is highly unlikely that it contains semicolons,
and on Windows (without POSIX emulation), it is virtually guaranteed, as
everybody should have both $SYSTEMROOT and $SYSTEMROOT/system32 in their
PATH.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
The idea is to allow running the test suite on MinGit with BusyBox
installed in /mingw64/bin/sh.exe. In that case, we will want to exclude
sort & find (and other Unix utilities) from being bundled.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
