(Ruby) OAuth2 Token using IdentityServer4 with Client Credentials

Demonstrates how to get an OAuth2 access token using the client credential flow with IdentityServer4.

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# This example assumes the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

http = Chilkat::CkHttp.new()

# The first step is to fetch your IdentityServer4's discovery document
# (OpenID Connect defines a discovery mechanism, called OpenID Connect Discovery, where an OpenID server publishes its metadata at a well-known URL, 
# typically https://server.com/.well-known/openid-configuration

# resp is a CkHttpResponse
resp = http.QuickRequest("GET","https://localhost:5000/.well-known/openid-configuration")
if (http.get_LastMethodSuccess() != true)
    print http.lastErrorText() + "\n";
    exit
end

if (resp.get_StatusCode() != 200)
    print "Received response status code " + resp.get_StatusCode().to_s() + "\n";
    print "Response body containing error text or JSON:" + "\n";
    print resp.bodyStr() + "\n";

    exit
end

json = Chilkat::CkJsonObject.new()
success = json.Load(resp.bodyStr())

# We have the discovery document, which contains something like this:

# You can use this online tool to generate parsing code from sample JSON: 
# Generate Parsing Code from JSON

# {
#   "issuer": "https://localhost:5000",
#   "jwks_uri": "https://localhost:5000/.well-known/openid-configuration/jwks",
#   "authorization_endpoint": "https://localhost:5000/connect/authorize",
#   "token_endpoint": "https://localhost:5000/connect/token",
#   "userinfo_endpoint": "https://localhost:5000/connect/userinfo",
#   "end_session_endpoint": "https://localhost:5000/connect/endsession",
#   "check_session_iframe": "https://localhost:5000/connect/checksession",
#   "revocation_endpoint": "https://localhost:5000/connect/revocation",
#   "introspection_endpoint": "https://localhost:5000/connect/introspect",
#   "frontchannel_logout_supported": true,
#   "frontchannel_logout_session_supported": true,
#   "backchannel_logout_supported": true,
#   "backchannel_logout_session_supported": true,
#   "scopes_supported": [
#     "openid",
#     "profile",
#     "email",
#     "MyCompany.profile",
#     "MyCompany.Identity.WebApi",
#     "MyCompany.TriHub.WebApi",
#     "offline_access"
#   ],
#   "claims_supported": [
#     "sub",
#     "updated_at",
#     "locale",
#     "zoneinfo",
#     "birthdate",
#     "gender",
#     "website",
#     "profile",
#     "preferred_username",
#     "nickname",
#     "middle_name",
#     "given_name",
#     "family_name",
#     "name",
#     "picture",
#     "email_verified",
#     "email",
#     "userId",
#     "groups",
#     "fullname"
#   ],
#   "grant_types_supported": [
#     "authorization_code",
#     "client_credentials",
#     "refresh_token",
#     "implicit",
#     "password"
#   ],
#   "response_types_supported": [
#     "code",
#     "token",
#     "id_token",
#     "id_token token",
#     "code id_token",
#     "code token",
#     "code id_token token"
#   ],
#   "response_modes_supported": [
#     "form_post",
#     "query",
#     "fragment"
#   ],
#   "token_endpoint_auth_methods_supported": [
#     "client_secret_basic",
#     "client_secret_post"
#   ],
#   "subject_types_supported": [
#     "public"
#   ],
#   "id_token_signing_alg_values_supported": [
#     "RS256"
#   ],
#   "code_challenge_methods_supported": [
#     "plain",
#     "S256"
#   ]
# }
# 

# The next steps are to (1) get the token_endpoint,
# and (2) verify that the client_credentials grant type is supported.

tokenEndpoint = json.stringOf("token_endpoint")

# grantTypes is a CkJsonArray
grantTypes = json.ArrayOf("grant_types_supported")
clientCredentialsIdx = grantTypes.FindString("client_credentials",true)

# If clientCredentialsIdx is less then zero (-1) then the "client_credentials" string was not found.
if (clientCredentialsIdx < 0)
    print "The client credentials grant type is not supported." + "\n";
    exit
end

# Request the access token using our Client ID and Client Secret.
# We're going to duplicate this CURL statement:

# curl --request POST \
#   --url '<tokenEndpoint>' \
#   --header 'content-type: application/x-www-form-urlencoded' \
#   --data 'grant_type=client_credentials&client_id=CLIENT_ID&client_secret=CLIENT_SECRET'

req = Chilkat::CkHttpRequest.new()
req.put_HttpVerb("POST")
req.AddParam("grant_type","client_credentials")
req.AddParam("client_id","CLIENT_ID")
req.AddParam("client_secret","CLIENT_SECRET")

# resp is a CkHttpResponse
resp = http.PostUrlEncoded(tokenEndpoint,req)
if (http.get_LastMethodSuccess() == false)
    print http.lastErrorText() + "\n";
    exit
end

# Make sure we got a 200 response status code, otherwise it's an error.
if (resp.get_StatusCode() != 200)
    print "POST to token endpoint failed." + "\n";
    print "Received response status code " + resp.get_StatusCode().to_s() + "\n";
    print "Response body containing error text or JSON:" + "\n";
    print resp.bodyStr() + "\n";

    exit
end

success = json.Load(resp.bodyStr())

# Our JSON response should contain this:
# {
#   "access_token":"eyJz93a...k4laUWw",
#   "token_type":"Bearer",
#   "expires_in":86400
# }

# Get the access token:
accessToken = json.stringOf("access_token")

# The access token is what gets added to "Authorization: Bearer <access_token>"
# for the subsequent REST API calls..