Clients connected to MongooseIM may authenticate with their TLS certificates. This method is a combination of the SASL EXTERNAL mechanism and a compatible certificate-aware backend.

Server-side prerequisites

Properly configure ejabberd_c2s listener

A server must request the certificate from a client, so you'll need to enable verify_peer option and provide a path to CA chain that may be used for client's certificate check (cafile option).

Please check Listener modules page for more information or simply follow the examples at the end of this section.

Enable SASL EXTERNAL method

A SASL EXTERNAL authentication method is disabled by default. In order to enable it, please add sasl_mechanisms option to MongooseIM config file. Its value must include a cyrsasl_external item. Obviously the list may be longer, if the system should support both certificate and password based authentication.

Enable compatible authentication backend

Please modify auth_opts option in MongooseIM's config file to include proper item. For now, only pki backend supports SASL EXTERNAL.


Some authentication backends may enforce plain password storage format, which automatically disables SASL EXTERNAL. Below you may find a list of backends that are safe to use with cyrsasl_external mechanism.

  • pki
  • anonymous
  • http without {is_external, true} option
  • internal
  • odbc
  • riak


Certificate authentication only.

{listen, [
           {5222, ejabberd_c2s, [
                                  {cafile, "/path/to/ca.pem"},

{auth_method, [pki]}.

{sasl_mechanisms, [cyrsasl_external]}.

Authentication with a client certificate (validated with provided CA chain) or password (validated with data stored in RDBMS).

{listen, [
           {5222, ejabberd_c2s, [
                                  {cafile, "/path/to/ca.pem"},

{auth_method, [odbc, pki]}.

{sasl_mechanisms, [cyrsasl_scram, cyrsasl_external]}.

Client certificate prerequisites

SASL EXTERNAL will be offered by the server only when a client provides a valid certificate.

Please check documentation of a specific authentication backend you're going to use.

Usage example - Gajim

Verified with Gajim 0.16.8, installed from package gajim-0.16.8-1.fc25.noarch.

Generate client certificate

openssl genrsa -des3 -out rootCA.key 4096
openssl req -x509 -new -nodes -key rootCA.key -sha256 -days 1024 -out rootCA.crt
openssl genrsa -out client.key 2048
openssl req -new -key client.key -out client.csr # Remember to provide username as Common Name!
openssl x509 -req -in client.csr -CA rootCA.crt -CAkey rootCA.key -CAcreateserial -out client.crt -days 500 -sha256
openssl pkcs12 -export -inkey client.key -in client.crt -out client.p12

Configure MongooseIM

See examples in the section above. We recommend using the first snippet for simplicity.

You don't need to pre-create a user account in order to log in with a certificate.

Add an account in Gajim

  1. Edit -> Accounts -> Add.
  2. Pick "I already have an account I want to use".
  3. Jabber ID is [Common Name from certificate]@localhost (domain is different if you've changed it in hosts option). Press "Next".
  4. Untick "Connect when I press Finish" and press "Advanced".
  5. Unfold "Client certificate" and choose the .p12 you've created earlier. Tick "Certificate is encrypted".
  6. Click "Close" and set status to "Available". Tell Gajim to ingnore the unverified server certificate (by default it's self-signed).

If Gajim fails to connect, try to restart it. Version 0.16.8 sometimes "forgets" to ask for the client certificate password.