====================================================================

                             CERT-Renater

                 Note d'Information No. 2020/VULN656
_____________________________________________________________________

DATE                : 07/12/2020

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S): Systems running Apache Groovy versions prior to
                         2.4.21, 2.5.14, 3.0.7, 4.0.0-alpha-2.

=====================================================================
http://mail-archives.apache.org/mod_mbox/www-announce/202012.mbox/%3cCADRx3PPJFs4x2Oyy-auG+=e2nB+bDx_f_tKR7xn2qXW7518Pgg@mail.gmail.com%3e
_____________________________________________________________________


CVE-2020-17521 Apache Groovy Information Disclosure

Severity: Important

Vendor: The Apache Software Foundation

Versions Affected:

Unsupported Codehaus versions of Groovy from 2.0 to 2.4.4.
Apache Groovy versions 2.4.4 to 2.4.20, 2.5.0 to 2.5.13,
3.0.0 to 3.0.6, and 4.0.0-alpha-1.

Fixed in versions 2.4.21, 2.5.14, 3.0.7, 4.0.0-alpha-2


Impact:

This vulnerability potentially impacts Unix-like systems, and very old
versions of Mac OSX and Windows. On such OS versions, Groovy may create
temporary directories within the OS temporary directory which is shared
between all users on affected systems. Groovy will create such
directories for internal use when producing Java Stubs (very low impact)
or on behalf of user code via two extension methods[4,5] for creating
temporary directories.
If Groovy user code uses either of these extension methods, and stores
executable code in the resulting temporary directory, then the risk is
high, since this can lead to local privilege escalation. If such Groovy
code is making use of the temporary directory to store sensitive
information, then the risk is medium, since such information could be
exposed or modified.

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

Is the Groovy code running on a machine with an impacted operating
system?
Do other users have access to the machine running the Groovy code?
Does the Groovy code create temporary directories using Groovy's
createTempDir extension methods[4,5]?

If you answer no to any of these questions, you are not affected.
If you answered yes, does the Groovy code write or store executable code
in the temporary directory? If you answer yes, the risk is high, and can
lead to local privilege escalation. Does the Groovy code write sensitive
information, like API keys or passwords, into the temporary directory?
If you answer yes, the risk is medium, and information may be exposed or
modified.


Description:

Groovy was making use of a method in the JDK which is now flagged as not
suitable for security-sensitive contexts. In addition, Groovy wasn't
checking a flag related to successful creation of the temporary
directory which leads to a race condition whereby the vulnerability
exists[1].

For the fixed versions, Groovy 2.5 and above is now using a newer JDK
method which creates a directory that is only readable by the user
running the Groovy code. The same is true for the fixed Groovy 2.4
version except if running on a pre-JDK7 version of the JDK in which case
a fallback implementation is used which now checks for successful
creation of the temporary directory.
This eliminates the high-risk scenario involving the race condition
whereby executables or information could be modified, but still leaves
the potential for sensitive information leakage. Groovy 2.4/JDK 6 users
are recommended to use the `java.io.tmpdir` mitigation.


Mitigation:

Setting the `java.io.tmpdir` system environment variable to a directory
that is exclusively owned by the executing user will fix this
vulnerability for all operating systems and all Groovy versions.

Users who cannot easily move to the fixed Groovy versions may wish to
consider using the JDK's Files#createTempDirectory method instead of the
Groovy extension methods.


Credit:

This vulnerability was discovered by Jonathan Leitschuh (
https://twitter.com/jlleitschuh)

Similar Vulnerabilities:

* Jetty -
https://github.com/eclipse/jetty.project/security/advisories/GHSA-g3wg-6mcf-8jj6
* JUnit4 -
https://github.com/junit-team/junit4/security/advisories/GHSA-269g-pwp5-87pp
* 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


References:

[1] CWE-379: Creation of Temporary File in Directory with Insecure
Permissions (https://cwe.mitre.org/data/definitions/379.html)
[2] "File.createTempFile" should not be used to create a directory (
https://rules.sonarsource.com/java/tag/owasp/RSPEC-2976)
[3] Groovy CVE list (https://groovy-lang.org/security.html)
[4]
https://docs.groovy-lang.org/latest/html/groovy-jdk/java/io/File.html#createTempDir()
[5]
https://docs.groovy-lang.org/latest/html/groovy-jdk/java/io/File.html#createTempDir(java.lang.String,%20java.lang.String)
[6] related Jira issue: https://issues.apache.org/jira/browse/GROOVY-9824


=========================================================
+ CERT-RENATER       |    tel : 01-53-94-20-44          +
+ 23/25 Rue Daviel   |    fax : 01-53-94-20-41          +
+ 75013 Paris        |    email:cert@support.renater.fr +
=========================================================