rabbitmq-server/deps/rabbitmq_auth_mechanism_ssl

x509 (TLS/SSL) certificate Authentication Mechanism for RabbitMQ

This plugin allows RabbitMQ clients authenticate using x509 certificates and TLS (PKI) peer verification mechanism instead of credentials (username/password pairs).

How it Works

When a client connects and performs TLS upgrade, the username is obtained from the client's TLS (x509) certificate. The user's password is not checked.

In order to use this mechanism the client must connect with TLS enabled, and present a client certificate.

Usage

This mechanism must also be enabled in RabbitMQ's configuration file, see Authentication Mechanisms and Configuration guides for more details.

A couple of examples:

auth_mechanisms.1 = PLAIN
auth_mechanisms.2 = AMQPLAIN
auth_mechanisms.3 = EXTERNAL

to allow this mechanism in addition to the defaults, or:

auth_mechanisms.1 = EXTERNAL

to allow only this mechanism and prohibit connections that use username and passwords.

For safety the server must be configured with the SSL option 'verify' set to 'verify_peer', to ensure that if an SSL client presents a certificate, it gets verified.

On Certificate Formats and Generation

RabbitMQ uses certificates and private keys in the PEM format. How they are generated is entirely up to the cluster operator. They can be obtained from a well-known and trusted commercial certificate authority or generated as "self-signed" (the CA will be project-specific and will not be widely trusted).

tls-gen is a tool that can generate self-signed certificate chains: a CA, a CA certificate, zero or more intermediate certificates and a client or server (leaf) certificate.

Some of the examples below will use openssl CLI tools directly because of their widespread use. However, this plugin will work just fine with any x.509 standards compliant certificate in the PEM format, regardless of what tool has generated them.

Username Extraction from Certificate

Distinguished Name

By default this will set the username to an RFC 4514-ish string form of the certificate's subject's Distinguished Name, similar to that produced by OpenSSL's "-nameopt RFC 2253" option.

You can obtain this string form from a certificate with a command like:

openssl x509 -nameopt RFC2253 -subject -noout -in path/to/cert.pem

or from an existing amqps connection with commands like:

rabbitmqctl list_connections peer_cert_subject

Subject Alternative Name

To extract username from a Subject Alternative Name (SAN) field, a few settings need to be configured. Since a certificate can have more than one SAN field and they can represent identities of different types, the type and the index of the field to use must be provided.

For example, to use the first SAN value of type DNS:

auth_mechanisms.1 = EXTERNAL

ssl_cert_login_from      = subject_alternative_name
ssl_cert_login_san_type  = dns
ssl_cert_login_san_index = 0

Or of type email:

auth_mechanisms.1 = EXTERNAL

ssl_cert_login_from      = subject_alternative_name
ssl_cert_login_san_type  = email
ssl_cert_login_san_index = 0

Common Name

To use the Common Name instead, set rabbit.ssl_cert_login_from to common_name:

auth_mechanisms.1 = EXTERNAL

ssl_cert_login_from = common_name

Note that the authenticated user will then be looked up in the configured authentication / authorisation backend(s). This will be the internal node database by default but could include other backends if so configured.

Copyright & License

(c) 2007-2025 Broadcom. All Rights Reserved. The term “Broadcom” refers to Broadcom Inc. and/or its subsidiaries.

Released under the same license as RabbitMQ.