Apache Storm Client: Anonymous principal assigned on TLS client certificate verification failure

Improper Handling of TLS Client Authentication Failure Leading to Anonymous Principal Assignment in Apache Storm

Versions Affected: up to 2.8.7

Description: When TLS transport is enabled in Apache Storm without requiring client certificate authentication (the default configuration), the TlsTransportPlugin assigns a fallback principal (CN=ANONYMOUS) if no client certificate is presented or if certificate verification fails. The underlying SSLPeerUnverifiedException is caught and suppressed rather than rejecting the connection.

This fail-open behavior means an unauthenticated client can establish a TLS connection and receive a valid principal identity. If the configured authorizer (e.g., SimpleACLAuthorizer) does not explicitly deny access to CN=ANONYMOUS, this may result in unauthorized access to Storm services. The condition is logged at debug level only, reducing visibility in production.

Impact: Unauthenticated clients may be assigned a principal identity, potentially bypassing authorization in permissive or misconfigured environments.

Mitigation: Users should upgrade to 2.8.7 in which TLS authentication failures are handled in a fail-closed manner.

Users who cannot upgrade immediately should:

• Enable mandatory client certificate authentication (nimbus.thrift.tls.client.auth.required: true)
• Ensure authorization rules explicitly deny access to CN=ANONYMOUS
• Review all ACL configurations for implicit default-allow behavior