Configuring trusted certificates

How to configure the Keycloak Truststore to communicate through TLS.

When Keycloak communicates with external services or has an incoming connection through TLS, it has to validate the remote certificate in order to ensure it is connecting to a trusted server. This is necessary in order to prevent man-in-the-middle attacks.

The certificates of these clients or servers, or the CA that signed these certificates, must be put in a truststore. This truststore is then configured for use by Keycloak.

Configuring the System Truststore

The existing Java default truststore certs will always be trusted. If you need additional certificates, which will be the case if you have self-signed or internal certificate authorities that are not recognized by the JRE, they can be included in the conf/truststores directory or subdirectories. The certs may be in PEM files, or PKCS12 files with extension .p12 or .pfx. If in PKCS12, the certs must be unencrypted - meaning no password is expected.

If you need an alternative path, use the --truststore-paths option to specify additional files or directories where PEM or PKCS12 files are located. Paths are relative to where you launched Keycloak, so absolute paths are recommended instead. If a directory is specified, it will be recursively scanned for truststore files.

After all applicable certs are included, the truststore will be used as the system default truststore via the javax.net.ssl properties, and as the default for internal usage within Keycloak.

For example:

bin/kc.[sh|bat] start --truststore-paths=/opt/truststore/myTrustStore.pfx,/opt/other-truststore/myOtherTrustStore.pem

It is still possible to directly set your own javax.net.ssl truststore System properties, but it’s recommended to use the --truststore-paths instead.

Hostname Verification Policy

You may refine how hostnames are verified by TLS connections with the tls-hostname-verifier property.

  • WILDCARD (the default) allows wildcards in subdomain names, such as *.foo.com.

  • ANY means that the hostname is not verified.

  • When using STRICT, the Common Name (CN) must match the hostname exactly.

    Please note that this setting does not apply to LDAP secure connections, which require strict hostname checking.

Relevant options

Value

tls-hostname-verifier

The TLS hostname verification policy for out-going HTTPS and SMTP requests.

CLI: --tls-hostname-verifier
Env: KC_TLS_HOSTNAME_VERIFIER

ANY, WILDCARD (default), STRICT

truststore-paths

List of pkcs12 (p12 or pfx file extensions), PEM files, or directories containing those files that will be used as a system truststore.

CLI: --truststore-paths
Env: KC_TRUSTSTORE_PATHS
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