Overview

Apache Solr is a full text search engine that is built on Apache Lucene. One of the common questions on the solr-user mailing list (ie: here and here) is how to hide sensitive values from the Solr UI. There is a little known setting that enables hiding these sensitive values.

Apache Solr and Hiding Sensitive Properties

Apache Solr has a few places where sensitive values can be seen on the Solr UI. The keystore and truststore passwords are two examples that came up as part of SOLR-10076. Starting in Solr 6.6 and 7.0, Solr will hide any property in the /admin/info/system API that contains the word password when the system property solr.redaction.system.enabled is set to true. The /admin/info/system API is used to power the Solr UI. This works well for most cases, but the implementation is more generic enabling it to hide any custom properties.

The property solr.redaction.system.pattern is a system property that takes a regular expression. If the regular expression matches the property name then the system property value will be redacted. This can enable hiding sensitive values for custom libraries or other use cases.

The table below lays out the two properties that can be configured in Solr 6.6 or later.

Apache Solr and Hiding Metrics Properties

The Solr Metrics API can leak sensitive information as well. There is a hiddenSysProps configuration that can prevent certain properties from being exposed via the metrics API. If additional properties need to be hidden then they need to be configured in the hiddenSysPropes section.

Conclusion

Currently, there is limited documentation about the available options for hiding sensitive values. It is frustrating to have to configure hiding sensitive values in two places, but there is hope for improvement. SOLR-12976 was created earlier this month to try to address the duplication and documentation.