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gitoxide-core does not neutralize special characters for terminals

Low severity GitHub Reviewed Published Aug 22, 2024 in GitoxideLabs/gitoxide • Updated Oct 24, 2024

Package

cargo gitoxide (Rust)

Affected versions

<= 0.38.0

Patched versions

None
cargo gitoxide-core (Rust)
<= 0.42.0
None

Description

Summary

The gix and ein commands write pathnames and other metadata literally to terminals, even if they contain characters terminals treat specially, including ANSI escape sequences. This sometimes allows an untrusted repository to misrepresent its contents and to alter or concoct error messages.

Details

gitoxide-core, which provides most underlying functionality of the gix and ein commands, does not neutralize newlines, backspaces, or control characters—including those that form ANSI escape sequences—that appear in a repository's paths, author and committer names, commit messages, or other metadata. Such text may be written as part of the output of a command, as well as appearing in error messages when an operation fails.

ANSI escape sequences are of particular concern because, when printed to a terminal, they can change colors, including to render subsequent text unreadable; reposition the cursor to write text in a different location, including where text has already been written; clear the terminal; set the terminal title-bar text to arbitrary values; render the terminal temporarily unusable; and other such operations.

The effect is mostly an annoyance. But the author of a malicious repository who can predict how information from the repository may be accessed can cause files in the repository to be concealed or otherwise misrepresented, as well as rewrite all or part of error messages, or mimic error messages convincingly by repositioning the cursor and writing colored text.

PoC

On a Unix-like system in a POSIX-compatible shell, run:

git init misleading-path
cd misleading-path
touch "$(printf '\033]0;Boo!\007\033[2K\r\033[91mError: Repository is corrupted. Run \033[96mEVIL_COMMAND\033[91m to attempt recovery.\033[0m')"
git add .
git commit -m 'Initial commit'

In the repository—or, if desired, in a clone of it, to show that this is exploitable by getting a user to clone an untrusted repository—run this command, which outputs entries in a three-column form showing type, hash, and filename:

gix tree entries

Although the output is of that form, it does not appear to be. Instead, the output in a terminal looks like this, colorized to appear to be an error message, with EVIL_COMMAND in another color, and with no other text:

Error: Repository is corrupted. Run EVIL_COMMAND to attempt recovery.

In some terminals, a beep or other sound will be made. In most terminals, the title bar text will be changed to Boo!, though in some shells this may be immediately undone when printing the prompt. These elements are included to showcase the abilities of ANSI escape sequences, but they are not usually themselves threats.

To see what is actually produced, gix tree entries can be piped to a command that displays special characters symbolically, such as less or cat -v if available.

BLOB e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 ESC]0;Boo!^GESC[2K^MESC[91mError: Repository is corrupted. Run ESC[96mEVIL_COMMANDESC[91m to attempt recovery.ESC[0m

That shows the effect on gix tree entries, but various other commands are also affected, and the escape sequences and other special characters can also appear in non-path metadata, such as in the user.name used to create a commit.

Impact

For users who do not clone or operate in clones of untrusted repositories, there is no impact.

Windows is much less affected than Unix-like systems due to limitations on what characters can appear in filenames, and because traditionally Windows terminals do not support as many ANSI escape sequences.

Because different gix and ein commands display different data in different formats, the author of a malicious repository must guess how it will be used, which complicates crafting truly convincing output, though it may be possible to craft a repository where gix clone fails to clone it but produces a misleading message.

Although this is mainly exploitable on systems other than Windows, in the ability to produce misleading output this superficially resembles CVE-2024-35197. But this is much more limited, because:

  • The misleading output can only be made to go where the application is already sending output. Redirection is not defeated, and devices to access cannot be chosen by the attacker.
  • The misleading output can only be take place when the application is already producing output. This limitation complicates the production of believable messages.
  • Only terminals are affected. Even if a standard stream is redirected to another file or device, these special characters would not have a special effect, unless echoed later without sanitization.
  • Reading and blocking cannot be performed.
  • Applications other than the gitoxide gix and ein executables are unaffected. The exception is if another application uses gitoxide-core. But this is explicitly discouraged in the gitoxide-core documentation and is believed to be rare.

References

@Byron Byron published to GitoxideLabs/gitoxide Aug 22, 2024
Published by the National Vulnerability Database Aug 22, 2024
Published to the GitHub Advisory Database Aug 22, 2024
Reviewed Aug 22, 2024
Last updated Oct 24, 2024

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements Present
Privileges Required None
User interaction Passive
Vulnerable System Impact Metrics
Confidentiality None
Integrity Low
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

EPSS score

0.043%
(10th percentile)

Weaknesses

CVE ID

CVE-2024-43785

GHSA ID

GHSA-88g2-r9rw-g55h

Source code

Credits

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