Configuring a Truststore

How to configure the Keycloak Truststore to communicate with external services through TLS.

When Keycloak communicates with external services through TLS, it has to validate the remote server’s 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 remote server’s or the CA that signed these certificates must be put in a truststore. This truststore is managed by the Keycloak server.

The truststore is used when connecting securely to identity brokers, LDAP identity providers, when sending emails, and for backchannel communication with client applications. It is also useful when you want to change the policy on how host names are verified and trusted by the server.

By default, a truststore provider is not configured, and any TLS/HTTPS connections fall back to standard Java Truststore configuration. If there is no trust established, then these outgoing requests will fail.

Configuring the Keycloak Truststore

You can add your truststore configuration by entering this command:

bin/kc.[sh|bat] start --spi-truststore-file-file=myTrustStore.jks --spi-truststore-file-password=password --spi-truststore-file-hostname-verification-policy=ANY

The following are possible configuration options for this setting:

file

The path to a Java keystore file. HTTPS requests need a way to verify the host of the server to which they are talking. This is what the truststore does. The keystore contains one or more trusted host certificates or certificate authorities. This truststore file should only contain public certificates of your secured hosts. This is REQUIRED if any of these properties are defined.

password

Password of the keystore. This option is REQUIRED if any of these properties are defined.

hostname-verification-policy

For HTTPS requests, this option verifies the hostname of the server’s certificate. Default: WILDCARD

  • ANY means that the hostname is not verified.

  • WILDCARD allows wildcards in subdomain names, such as *.foo.com.

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

Example of a truststore configuration

The following is an example configuration for a truststore that allows you to create trustful connections to all mycompany.org domains and its subdomains:

bin/kc.[sh|bat] start --spi-truststore-file-file=path/to/truststore.jks --spi-truststore-file-password=change_me --spi-truststore-file-hostname-verification-policy=WILDCARD
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