log4j-sniffer

README

log4j-sniffer

log4j-sniffer crawls for all instances of log4j that are earlier than version 2.16 on disk within a specified directory. It can be used to determine whether there are any vulnerable instances of log4j within a directory tree.

What this does

log4j-sniffer will scan a filesystem looking for all files of the following types based upon suffix:

• Zips: .zip
• Java archives: .jar, .war, .ear
• Tar: .tar.gz, .tgz

It will look for the following:

• Jar files matching log4j-core-<version>.jar, including those nested within another archive
• Class files named org.apache.logging.log4j.core.lookup.JndiLookup within Jar files or other archives
• Class files named JndiLookup in other package hierarchies

Installing

If Go is available on the host system, the following command can be used to install this program:

go install github.com/palantir/log4j-sniffer@latest

This repository also publishes binaries that can be downloaded and executed.

Downloads

log4j-sniffer executables compiled for linux-amd64, darwin-amd64, and darwin-arm64 architectures are available on the releases page.

Running

This tool is intensive and is recommended to be run with low priority settings.

On Linux:

ionice -c 3 nice -n 19 log4j-sniffer crawl /path/to/a/directory

Output for vulnerable files looks as follows:

INFO  [2021-12-17T14:10:10.046706-08:00] github.com/palantir/log4j-sniffer/pkg/crawl/crawler.go:50: Crawl started (runID: 0132794a-6b5a-4632-b7ee-7e92672990ee)
INFO  [2021-12-17T14:10:10.053085-08:00] github.com/palantir/log4j-sniffer/pkg/crawl/report.go:44: CVE-2021-45046 detected (classNameMatched: false, classPackageAndNameMatch: true, filename: log4j-core-2.14.1.jar, jarNameInsideArchiveMatched: false, jarNameMatched: true, runID: 0132794a-6b5a-4632-b7ee-7e92672990ee) (path: examples/single_bad_version/log4j-core-2.14.1.jar)
INFO  [2021-12-17T14:10:10.053327-08:00] github.com/palantir/log4j-sniffer/pkg/crawl/crawler.go:54: Crawl complete (crawlDuration: 6.867927ms, filesScanned: 1, permissionDeniedCount: 0, runID: 0132794a-6b5a-4632-b7ee-7e92672990ee)
INFO  [2021-12-17T14:10:10.053455-08:00] github.com/palantir/log4j-sniffer/internal/crawler/crawl.go:46: Files affected by CVE-2021-45046 detected (runID: 0132794a-6b5a-4632-b7ee-7e92672990ee, vulnerableFileCount: 1)

With the following meaning:

• classNameMatched: there was a .class file called JndiLookup
• classPackageAndNameMatched: there was a .class file called JndiLookup with a package of org.apache.logging.log4j.core.lookup
• jarNameInsideArchiveMatched: there was a .jar file called log4j-core-<version>.jar inside the archive
• jarNameMatched: the file scanned was a .jar file called log4j-core-<version>.jar
• filename: the filename matched
• path: the full path on disk for the file