Always getting "invalid_client" from Identity Server - asp.net-core

Question

Everything seems normal but it is not working, It returns "Invalid_Client" - (400 - Bad request).
Both side so simple below;
Identity Server Code:
new Client
{
ClientId = "js",
ClientSecrets = {
new Secret("secret".Sha256())
},
AllowedGrantTypes = GrantTypes.ClientCredentials,
RequireClientSecret = false,
AllowedScopes =
{
"api1"
}
}
Javascript Client Code:
axios.post('http://localhost:5000/connect/token',request, {
headers: {
'client_id' : 'js',
'client_secret' : 'secret',
'grant_type': 'client_credentials',
'scope' : 'api1'
}});

Answer 1

The parameters should be passed in request body not request header , you can modify the client script as :
const params = new URLSearchParams();
params.append('client_id', 'js');
params.append('client_secret', 'secret');
params.append('grant_type', 'client_credentials');
params.append('scope', 'api1');
axios.post('http://localhost:5000/connect/token', params, {
headers: {
'Content-Type': 'application/x-www-form-urlencoded',
}
}).then(function (response) {
console.log(response.data);
});
And also configure CORS is to use the AllowedCorsOrigins collection on the client configuration:
new Client
{
ClientId = "js",
ClientSecrets = {
new Secret("secret".Sha256())
},
AllowedCorsOrigins= new List<string>() { "http://localhost:5002" },
AllowedGrantTypes = GrantTypes.ClientCredentials,
RequireClientSecret = false,
AllowedScopes =
{
"api1"
}
},

Answer 2

Should not use normall fetch or axis.
Because the service is Oauth service and should be use 'client-oauth2' library.
Code Example:
var ClientOAuth2 = require("client-oauth2");
var authRequest = new ClientOAuth2({
clientId: IDENTITY_CONFIG.client_id,
clientSecret: IDENTITY_CONFIG.client_secret,
accessTokenUri: IDENTITY_CONFIG.token_endpoint,
scopes: [IDENTITY_CONFIG.grantType]
});
return authRequest.credentials.getToken();