Vulnerability

The JUnit4 test rule TemporaryFolder contains a local information disclosure vulnerability.

Example of vulnerable code: java public static class HasTempFolder { @Rule public TemporaryFolder folder = new TemporaryFolder();

@Test public void testUsingTempFolder() throws IOException { folder.getRoot(); // Previous file permissions: drwxr-xr-x; After fix:drwx------ File createdFile= folder.newFile("myfile.txt"); // unchanged/irrelevant file permissions File createdFolder= folder.newFolder("subfolder"); // unchanged/irrelevant file permissions // ... } }

Impact

On Unix like systems, the system's temporary directory is shared between all users on that system. Because of this, when files and directories are written into this directory they are, by default, readable by other users on that same system.

This vulnerability does not allow other users to overwrite the contents of these directories or files. This is purely an information disclosure vulnerability.

When analyzing the impact of this vulnerability, here are the important questions to ask:

1. Do the JUnit tests write sensitive information, like API keys or passwords, into the temporary folder? - If yes, this vulnerability impacts you, but only if you also answer 'yes' to question 2. - If no, this vulnerability does not impact you. 2. Do the JUnit tests ever execute in an environment where the OS has other untrusted users. This may apply in CI/CD environments but normally won't be 'yes' for personal developer machines. - If yes, and you answered 'yes' to question 1, this vulnerability impacts you. - If no, this vulnerability does not impact you.

Patches

Because certain JDK file system APIs were only added in JDK 1.7, this this fix is dependent upon the version of the JDK you are using. - Java 1.7 and higher users: this vulnerability is fixed in 4.13.1. - Java 1.6 and lower users: no patch is available, you must use the workaround below.

Workarounds

If you are unable to patch, or are stuck running on Java 1.6, specifying the java.io.tmpdir system environment variable to a directory that is exclusively owned by the executing user will fix this vulnerability.

References - CWE-200: Exposure of Sensitive Information to an Unauthorized Actor - Fix commit https://github.com/junit-team/junit4/commit/610155b8c22138329f0723eec22521627dbc52ae

Similar Vulnerabilities - Google Guava - https://github.com/google/guava/issues/4011 - Apache Ant - https://nvd.nist.gov/vuln/detail/CVE-2020-1945 - JetBrains Kotlin Compiler - https://nvd.nist.gov/vuln/detail/CVE-2020-15824

For more information If you have any questions or comments about this advisory, please pen an issue in junit-team/junit4.

Summary

This vulnerability affects JUnit's support for writing Open Test Reporting XML files which is an opt-in feature of junit-platform-reporting.

If a repository is cloned using a GitHub token or other credentials in its URL, for example:

bash git clone https://${GHAPP}:${GHTOKEN}@github.com/example/example.git

The credentials are captured by OpenTestReportGeneratingListener which produces (trimmed for brevity):

xml <infrastructure> <git:repository originUrl="https://username:token@github.com/example/example.git" /> </infrastructure>

Details

https://github.com/junit-team/junit5/blob/6b7764dac92fd35cb348152d1b37f8726875a4e0/junit-platform-reporting/src/main/java/org/junit/platform/reporting/open/xml/OpenTestReportGeneratingListener.java#L183

I think this should be configurable in some way to exclude select git information or exclude it entirely.

PoC

1. Clone a repo using a GitHub token as shown above. 2. Enable the listener junit.platform.reporting.open.xml.enabled=true 3. Observe report captures credentials

Impact

Depending on the level of access of the token, it can be nothing, limited, or everything.

If these test reports are published or stored anywhere public, then there is the possibility that a rouge attacker can steal the token and perform elevated actions by impersonating the user or app.

Resolution

JUnit 5.13.2 and later replace credentials in the URL with . Moreover, including any Git metadata in the XML output is now an opt-in feature that can be enabled via the new junit.platform.reporting.open.xml.git.enabled=true configuration parameter but is not included by default.