chore(deps): update rust crate gix to 0.63.0 [security] #13949
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This PR contains the following updates:
0.62.0
->0.63.0
GitHub Vulnerability Alerts
CVE-2024-35186
Summary
During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.
Details
Although
gix-worktree-state
checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks ingix-fs
andgix-worktree
prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's.git
directory. The simplest cases are:..
to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon..git
to enter a.git
directory. This facilitates arbitrary code execution because hooks can be installed.A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:
/
, to traverse upward or downward. For example, even without containing any tree named..
or.git
, a repository can represent a file named../outside
or.git/hooks/pre-commit
. This is distinct from the more intuitive case a repository containing trees that represent those paths.\
, to traverse upward or downward. (Unlike/
, these are valid on other systems.) See GHSA-xjx4-8694-q2fq..git
..git
or a case variant, with characters added that HFS+ ignores in collation. See git/git@6162a1d..git
(or a case variant) by the use of NTFS stream notation, such as.git::$INDEX_ALLOCATION
. See GHSA-5wph-8frv-58vj.git~1
(or a case variant). See GHSA-589j-mmg9-733v.When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.
PoC
For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume
sed
supports-i
, which is the case on most systems. If using Windows, a Git Bash shell should be used.Example: Downward traversal to install hooks
git init dangerous-repo-installs-hook
andcd
into the directory..git@hooks@pre-commit
, with the contents:git add --chmod=+x .git@hooks@pre-commit
env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
git commit -m 'Initial commit'
Then, on another or the same machine:
gix clone …
command.ls -l .git/hooks
to observe that thepre-commit
hook is already present.git
. This causes the payload surreptitiously installed as apre-commit
hook to run, printing the messageVulnerable!
and creating a file in the current directory containing the current date and time.Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs
git commit
is capable of.Example: Upward traversal to create a file above the working tree
git init dangerous-repo-reaches-up
, andcd
into the directory.echo 'A file outside the working tree, somehow.' >..@​outside
git add ..@​outside
env LC_ALL=C sed -i.orig 's|\.\.@​outside|../outside|' .git/index
git commit -m 'Initial commit'
Then, as above, on the same or another machine, clone the repository with a
gix clone …
command. Observe that a file namedoutside
is present alongside (not inside) the cloned directory.Impact
Any use of
gix
or another application that makes use ofgix-worktree-state
, or otherwise relies ongix-fs
andgix-worktree
for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when
gix
is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.CVE-2024-35197
Summary
On Windows, fetching refs that clash with legacy device names reads from the devices, and checking out paths that clash with such names writes arbitrary data to the devices. This allows a repository, when cloned, to cause indefinite blocking or the production of arbitrary message that appear to have come from the application, and potentially other harmful effects under limited circumstances.
Details
It is possible to create a Git repository that contains references or filenames that Windows treats as legacy DOS-style aliases for system devices. When such a repository is cloned:
gix-ref
does not include a check for such names before attempting to access them on disk, which reads from the devices, though the ability to exfiltrate data appears limited.gix-worktree-state
does not treat such names as collisions and instead writes to them, which writes arbitrary attacker-controlled data to the devices.Some such device names refer to devices that are often absent or inaccessible. But a few are guaranteed to be available, allowing some attacks to be carried out with low complexity. For both reading refs and writing paths, one important case is the console:
CON
orCONIN$
reads data from the console, thereby blocking on console input, including in most situations where a console is not readily available. This may facilitate denial of service attacks.CON
orCONOUT$
writes its contents to the console. This allows an untrusted repository to produce arbitrary text that appears to be a message from the application. Such text may facilitate social engineering if it is selected to instruct the user to perform a particular action.Another potentially important case is serial ports. For example,
COM1
refers to the first serial port, if present. A malicious repository may be able to disrupt intended use of serial ports or attempt to interact with a device. In some configurations, it may be possible to interfere with the operation of a physical or virtual serial console. On Windows, local access to serial ports is often permitted even for limited user accounts without elevation.Naming Files, Paths, and Namespaces covers most reserved names.
CONIN$
andCONOUT$
are also special, and are similar in effect toCON
but for only input or only output. These names are case-insensitive and can also be accessed with file extensions (e.g,CON.txt
is equivalent toCON
) and with some variations involving added spaces or colons.PoC
Ref example
Create a repository on a non-Windows system (or in WSL) with at least one commit. Use
git tag CON
to create a lightweight tag namedCON
. Place the repository somewhere it can be cloned on Windows. Afile://
URL is sufficient for testing if a private remote is unavailable. If usinggit push
, pass--tags
so the remote has the tag.On a Windows system, clone the repository with
gix clone
. This command will block immediately, reading input from the console. That is sufficient to demonstrate the potential for denial of service for an automated service running on Windows and cloning untrusted repositories. The experiment can be stopped with Ctrl+C.However, if desired, input can be provided. Ending input with Ctrl+Z followed by Enter will cause it to be passed to the application. This will lead to an error message, the specific details of which vary by whether the input is empty or nonempty, and whether it matches or does not match the hexadecimal hash of the tagged commit.
Path example
Create a repository on a non-Windows system (or in WSL) and commit a file named
CON
with the contents:While that example text serves to illustrate the risk, any distinctive text is sufficient to observe the vulnerability. Place the repository somewhere it can be cloned on Windows. As above, a
file://
URL is sufficient.On a Windows system, clone the repository with
gix clone
. The output usually looks like this, with the deceptive message appearing to come fromgix
:The exact placement of the message is nondeterministic. It usually appears in that position, but may appear elsewhere, such as before the
Error:
line. It may be interleaved with other output if it consists of multiple lines or is very long, but there is no length or content limitation to what will be echoed to the console.Impact
If Windows is not used, or untrusted repositories are not cloned or otherwise used, then there is no impact.
The impact is expected to be limited in common configurations, but may vary widely depending on what devices exist, how they are being used, how much knowledge an attacker has of the precise details of their use, and whether the user is likely to trust information that appears in a console. Accessing devices through refs is expected to be less dangerous than accessing them through filenames, since it is trivial to attempt to write arbitrary data using filenames.
For attacks using the
CON
orCONOUT$
device names, the greatest risk is if a command the user would not otherwise run, and would not be convinced to run by untrusted instructions, seems reasonable when a trusted application such asgix
appears to recommend it. The user may then be misled into running an attacker's command.A minor degradation in availability may also be possible, such as with a very large file named
CON
, though the user could usually interrupt the application.Release Notes
Byron/gitoxide (gix)
v0.63.0
: gix v0.63.0Compare Source
New Features
checkout respects options for
core.protectHFS
andcore.protectNTFS
.This also adds
gitoxide.core.protectWindows
as a way to enforceadditional restrictions that are usually only available on Windows.
Note that
core.protectNFS
is always enabled by default, just likeit is in Git.
Bug Fixes
empty paths as configured will not be an error with lenient configuration enabled.
When using
gix::open_opts(path, options.strict_config(false))
, emptycore.excludesFile
valueswill not cause an error anymore.
Note that in strict mode, the behaviour is unchanged so invalid configuration can rather be fixed
than ignored.
don't unwrap when reading possibly left-over bytes from pack-stream
Commit Statistics
Commit Details
view details
88a6a4e
)3c7b7b3
)9511416
)d6cd449
)cd4de83
)6f55f2a
)79dce79
)gix-ref
(d2ae9d5
)gix-index
(5f86e6b
)f961687
)fcc3b69
)bad9a79
)core.protectHFS
andcore.protectNTFS
. (886d6b5
)gix-worktree
(1ca6a3c
)3c21741
)d3588ca
)04ef31e
)git2
(5197b5a
)e791bc5
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)54ac559
)fe24c89
)41bf65a
)Configuration
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