****This small mod allows players with Ely.by's auth system to enter the server with online_mode=true setting without interfering with Mojang's auth system.

The mod just combines two or more authentication systems without interfering with the server itself.

First, authentication occurs on the Mojang servers, and after an unsuccessful login, a check occurs on Ely.by or other servers, depending on the config. If it didn't pass either, then the player can't join the server.

In order to achieve this result, it was necessary to download the patch from the official site of Ely.by, which wasn't convenient and prevented players with official accounts from logging in.

When using this mod, it's recommended to change enforce-secure-profile=true to enforce-secure-profile=false in the server.properties file to disable message signing that Ely.by players don't have.

At the moment, I have managed to create an agent with this idea for other server cores besides fabric in combo-auth-agent.

Config example:

"AuthList":[ "(order of execution)" ],
"AuthSchema":{
    "(name)":{
        "url_check": "(hasJoined request)"
        "url_property" : "(texture request)"
        "AddProperty" : [{"(custom)" : "(property)"},
            {"name":"ely","value":"but why are you asking?"}]
    }
},
"debug" : "all/detail/(nothing)"