Bad request at accessToken url in apereo CAS server - oauth-2.0

Question

I want to integrate my spring cloud gateway application with apereo CAS server(running on 8443 port) and I configure CAS server to act as Oauth2 authorization server. here is the flow;
I request gateway
It interacts authorization server(CAS here)
Before interaction, it needs to login at there.
I login with default cas-overlay-template credentials successfully.(casuser:Mellon)
cas redirect to gateway with login/oauth2/code/login-client?code=OC-3-TURQDNdC4jXulPgK7ipJSzfoBLi-iaSv&state=aitARK42e0zx2iTFkeZxoRM2rLehXSex6gTIfZOHlwY%3D url.
And [invalid_grant] error happened at gateway.
I check Spring Cloud Gateway trace logs and error happens at getting access token step.
[ctor-http-nio-2] o.s.w.s.adapter.HttpWebHandlerAdapter : [33597172] Completed 302 FOUND, headers={masked}
[ctor-http-nio-2] o.s.h.s.r.ReactorHttpHandlerAdapter : [33597172] Handling completed
[ctor-http-nio-2] o.s.w.s.adapter.HttpWebHandlerAdapter : [33597172] HTTP GET "/login/oauth2/code/login-client?code=OC-14-F99FROWxhVYzpfxkmQqB1BAfP-oOfIfI&state=Y9XC3NNkPUvb649Tx0dIDG4ZyIInioAD-xT2ll3bfII%3D", headers={masked}
[ctor-http-nio-2] o.s.w.r.f.client.ExchangeFunctions : [dee9e83] HTTP POST http://localhost:8443/cas/oauth2.0/accessToken, headers={masked}
[ctor-http-nio-2] o.s.http.codec.FormHttpMessageWriter : [dee9e83] Writing form fields [grant_type, code, redirect_uri] (content masked)
[ctor-http-nio-2] o.s.w.r.f.client.ExchangeFunctions : [dee9e83] Response 400 BAD_REQUEST, headers={masked}
[ctor-http-nio-2] o.s.http.codec.json.Jackson2JsonDecoder : [dee9e83] Decoded [{error=invalid_grant}]
Clearly, it cannot request to access_token due to bad request. but, i can't find what valid parameters are. And, I don't request manually, instead it happens automatically at behind the scene. where is my mistake? thanks for your helps.
Here is my spring cloud gateway configuration:
spring:
security:
oauth2:
client:
registration:
login-client:
provider: uaa
client-id: first-client
client-secret: noonewilleverguess
authorization-grant-type: authorization_code
redirect-uri: "{baseUrl}/login/oauth2/code/{registrationId}"
provider:
uaa:
authorization-uri: http://localhost:8443/cas/oauth2.0/authorize
token-uri: http://localhost:8443/cas/oauth2.0/accessToken
user-info-uri: http://localhost:8443/cas/oauth2.0/profile
prefer-token-info: false
client-authentication-scheme: form
cas oauth2 registered service:
{
"#class" : "org.apereo.cas.support.oauth.services.OAuthRegisteredService",
"clientId": "first-client",
"clientSecret": "noonewilleverguess",
"serviceId": "http://localhost:8085/.*",
"name": "OAuthService",
"bypassApprovalPrompt": true,
"id": 1003,
"supportedGrantTypes": [ "java.util.HashSet", [ "authorization_code" ] ],
"supportedResponseTypes": [ "java.util.HashSet", [ "code" ] ]
}
The resources I used :
https://apereo.github.io/2019/02/19/cas61-as-oauth-authz-server/
https://apereo.github.io/cas/5.3.x/installation/OAuth-OpenId-Authentication.html#responsegrant-types

Answer 1

okay, the question was actually simple. spring cloud gateway fills 3 fields (grant_type, code, redirect_uri) automatically but cas apereo server has api which takes 5 fields (grant_type, code, redirect_uri and also client_id, client_secret). to address this problem, you can define your api which takes 3 parameters at cas and rest of logic will be same. the only things you do is to override access token api field behaivour.