This script is used to perform a fast check if your server is possibly affected by CVE-2021-44228 (the log4j vulnerability). It does not give a 100% proof, that you are not vulnerable, but it gives a hint if it is possible, that you could be vulnerable.
- scans files for occurrences of log4j
- checks for packages containing log4j and Solr ElasticSearch
- checks if Java is installed
- Analyzes JAR/WAR/EAR files
- Option of checking hashes of .class files in archives
wget https://raw.githubusercontent.com/rubo77/log4j_checker_beta/main/log4j_checker_beta.sh -q -O - |bash
The script can test .class files on the first level of JAR/WAR/EAR archives to see if they match with known sha256 hashes of vulnerable class files from log4j.
You have to provide a download of plain text file with sha256 hashes in HEX format, one per line, everything after first is ignored.
The URL can be placed in variable download_file. Otherwise this feature will not operate.
We did not include an actual URL, this exercise is left to the reader, as they say:
The information Lunasec.io has put out about hashes of vulnerable binary Java .class files:
https://github.com/lunasec-io/lunasec/blob/master/tools/log4shell/constants/vulnerablehashes.go
Also see their blog: https://www.lunasec.io/docs/blog/log4j-zero-day-mitigation-guide/
The command locate has to to be installed, be sure to have locate up-to-date with:
sudo updatedb
The command unzip also needs to be installed, to inspect the jar files.