Made it. Trouble was linked to domain names / ip discrepancies on my local network.

For the record, here what was required to make fider work with KeyCloak :

• In keycloak create client "fider" for the intended realm and get client secret in client "Credentials" tab
• In Fider set the following values for the new custom oauth provider
  • Client ID : fider
  • Client secret : the value generated by keycloak (e.g : 93e3ef33-a81a-4e06-abae-60ee1a350a81)
  • Authorize URL : http://keycloak.domain/auth/realms/ign/protocol/openid-connect/auth
  • Token URL : http://keycloak.domain/auth/realms/ign/protocol/openid-connect/token
  • Scope : I put "profile". A scope generated by default by keycloak for the fider client.
  • Profile API URL : http://keycloak.domain/auth/realms/ign/protocol/openid-connect/userinfo
  • JSON Path : ID = preferred_username / Name = name / Email = email

Will try with https and tls certificates soon but all in all this solution works in order to use an pre-existing LDAP.

For people who is gonna stumble here in the future.

I was trying to setup keycloak 25.0 with fider using docker-compose locally & to make it works, I needed to change a few things from esgn configs

• Authorize URL: http://127.0.0.1:8080/realms/{realm-name}/protocol/openid-connect/auth
• Token URL: http://127.0.0.1:8080/realms/{realm-name}/protocol/openid-connect/token
• Scope: I put profile openid email
• Profile API URL: http://127.0.0.1:8080/realms/{realm-name}/protocol/openid-connect/userinfo
• JSON Path, same as esgn

You can actually get the above urls by going to

http://127.0.0.1:8082/realms/{realm-name}/.well-known/openid-configuration

Do note here is 127.0.0.1 instead of localhost because when I used localhost, I received this error in fider logs.

dial tcp [::1]:8082: connect: connection refused