log4j-tools

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Overview

CVE-2021-44228 poses a serious threat to a wide range of Java-based applications. The important questions a developer may ask in this context are:

1. Does my code include log4j2?

Does the released code include log4j2? Which version of the library is included there? Answering these questions may not be immediate due to two factors:

1. Transitive dependencies: while log4j2 may not be in the direct dependency list of the project, it may be used indirectly by some other dependency.

2. The code of this library may not appear directly as a separate file (i.e., log4j2-core-2.xx.0.jar), but rather be bundled in some other code jar file.

JFrog is releasing a tool to help resolve this problem: scan_jndimanager_versions. The tool looks for the class code of JndiManager (regardless of containing .jar file names and content of pom.xml files), which is required for the vulnerability to be exploitable, and checks whether its version is fixed one (i.e., 2.15 or above) by testing for existence of an indicative string. Both Python and Java implementations are included.

2. Where does my code use log4j2?

The question is relevant for the cases where the developer would like to verify if the calls to log4j2 in the codebase may pass potentially attacker-controlled data. While the safest way to fix the vulnerability, as discussed in the advisories, is to apply the appropriate patches and global flags, controlling for and verifying the potential impact under assumption of unpatched log4j2 may be valuable in many situations. In order to address this problem JFrog is releasing two scripts:

1. scan_log4j2_calls_src.py, which locates calls to log4j2 logging functions (info, log, error etc.) with non-constant arguments in .java source files and reports the findings on the level of source file and line
2. scan_log4j2_calls_jar.py, which locates the calls to logging functions in compiled .jars, and reports the findings as class name and method names in which each call appears.

Usage instructions

scan_jndimanager_versions.py

The tool requires python3, without additional dependencies.

Usage

python scan_jndimanager_versions.py root-folder

The tool will scan root_folder recursively for .jar and .war files; in each located file the tool looks for a *log4j/core/net/JndiManager.class code (recursively in each .jar file). If the code is located, and does not contain allowedJndiProtocols string constant (added in 2.15), the file as reported as containing a vulnerable implementation if JndiManager.

scan_jndimanager_versions.jar

The tool requires java runtime, without additional dependencies. It can be recompiled from the provided source.

Usage

java -jar scan_jndimanager_versions.jar root-folder

The tool will scan root_folder recursively for .jar and .war files; in each located file the tool looks for a *log4j/core/net/JndiManager.class code. If the code is located, and does not contain allowedJndiProtocols string constant (added in 2.15), the file as reported as containing a vulnerable implementation if JndiManager.

scan_log4j_calls_jar.py

The tool requires python 3 and the following 3rd party libraries: jawa, tqdm, easyargs, colorama

Dependencies installation

pip install -r requirements.txt

Usage

The default use case:

python scan_log4j_calls_jar.py root-folder

will recursively scan all .jar files in root-folder, for each printing out locations (class name and method name) of calls to info/warn/error/log/debug /trace/fatal methods of log4j2.Logger.

The tool may be configured for additional use cases using the following command line flags.

For example,

python scan_log4j_calls_jar.py --class_regex ".*JndiManager$" --class_existence --no_quickmatch root-folder

Will scan all .jar files (even if they do have no mentions of log4j2) for the existence of a class ending with JndiManager.

scan_log4j_calls_src.py

The tool requires python 3 and the following 3rd party libraries: javalang, tqdm, easyargs, colorama

Dependencies installation

pip install -r requirements.txt

Usage

The default use case:

python scan_log4j_calls_src.py root-folder

will recursively scan all .java files in root-folder, for each printing out the locations (file name and corresponding code lines) of calls to log4j2 logging methods.

The tool may be configured for additional use cases using the following command line flags:

Compiling scan_jndimanager_versions.jar from source

cd scan_jndimanager_versions
gradle build
cp build/libs/scan_jndimanager_versions.jar ..