OAuth-SSO/main.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"net/url"
	"strings"

	"github.com/valyala/fasttemplate"
)

//ClientInformationStruct export
type ClientsInformationStruct []struct {
	ClientID     string   `json:"client-id"`
	ClientSecret string   `json:"client-secret"`
	Domain       string   `json:"domain"`
	ServiceName  string   `json:"service-name"`
	ServiceImage string   `json:"service-image"`
	Scope        []string `json:"scope"`
}

func main() {
	http.HandleFunc("/login", loginHandler)
	http.HandleFunc("/chklogin", chkloginHandler)
	http.Handle("/asset/", http.StripPrefix("/asset/", http.FileServer(http.Dir("./asset"))))

	http.ListenAndServe(":8080", nil)
}

func loginHandler(w http.ResponseWriter, r *http.Request) {
	_, _, ServiceName, ServiceImage, responseType, clientID, redirectURI, scope, state, nonce := confirmClientInformation(w, r)

	//serve file
	//push assembled data to page
	parsedPage, err := templateLoad("login.html", map[string]interface{}{
		"service-name":  string(ServiceName),
		"service-image": string(ServiceImage),
		"response_type": string(responseType),
		"client_id":     string(clientID),
		"redirect_uri":  string(redirectURI),
		"scope":         string(scope),
		"state":         string(state),
		"nonce":         string(nonce),
	})

	if err != nil {
		log.Println("Error. Unable to load login.html")
	}
	w.Write([]byte(parsedPage))
}

func chkloginHandler(w http.ResponseWriter, r *http.Request) {
	// Call ParseForm() to parse the raw query and update r.PostForm and r.Form.
	if err := r.ParseForm(); err != nil {
		fmt.Fprintf(w, "ParseForm() err: %v", err)
		return
	}
	fmt.Fprintf(w, "Post from website! r.PostFrom = %v\n", r.PostForm)
	email := r.FormValue("email")
	password := r.FormValue("password")
	fmt.Println(email, password)
}

func errHandler(w http.ResponseWriter, r *http.Request, errorMsg string) {
	//push assembled data to page
	parsedPage, err := templateLoad("error.html", map[string]interface{}{
		"error": string(errorMsg),
	})

	if err != nil {
		log.Println("Error. Unable to show error. Additionally, the error page also had error.")
	}
	w.Write([]byte(parsedPage))
	//sendTextResponse(w, parsedPage)
}

func confirmClientInformation(w http.ResponseWriter, r *http.Request) (string, string, string, string, string, string, string, string, string, string) {
	responseType := getGET(w, r, "response_type")
	if string(responseType) != "code" {
		errHandler(w, r, "Url param response_type was incompatible")

	}
	//
	clientID := getGET(w, r, "client_id")
	//
	redirectURI := getGET(w, r, "redirect_uri")
	redirectURIParsed, err := url.Parse(redirectURI)
	host, _, _ := net.SplitHostPort(redirectURIParsed.Host)
	//
	scope := getGET(w, r, "scope")
	state := getGET(w, r, "state")
	nonce := getGET(w, r, "nonce")

	//let say the GET request was good, then let us find does client-id and domain match our record
	data, err := ioutil.ReadFile("./client-id.json")
	if err != nil {
		fmt.Print(err)
	}
	var ClientsInformation ClientsInformationStruct
	err = json.Unmarshal(data, &ClientsInformation)
	if err != nil {
		fmt.Println("error:", err)
	}
	//process DB
	DBClientID := ""
	DBClientSecret := ""
	DBDomain := ""
	DBServiceName := ""
	DBServiceImage := ""
	var DBScope []string
	for _, ClientInformation := range ClientsInformation {
		if ClientInformation.ClientID == clientID {
			DBClientID = ClientInformation.ClientID
			DBClientSecret = ClientInformation.ClientSecret
			DBDomain = ClientInformation.Domain
			DBServiceName = ClientInformation.ServiceName
			DBServiceImage = ClientInformation.ServiceImage
			DBScope = ClientInformation.Scope
		}
	}
	if DBClientID == "" {
		errHandler(w, r, "client_id does not exist in our database.")

	}
	//check the record does it match
	if DBDomain != host {
		errHandler(w, r, "client_id and redirect_uri not match the system record.")

	}
	//check if scope is available for that client
	scopeArr := strings.Split(scope, " ")
	for _, scopeItem := range scopeArr {
		if !contains(DBScope, scopeItem) {
			errHandler(w, r, "scope not match our system record.")

		}
	}
	return DBClientSecret, DBDomain, DBServiceName, DBServiceImage, responseType, clientID, redirectURI, scope, state, nonce
}

func getGET(w http.ResponseWriter, r *http.Request, name string) string {
	response, ok := r.URL.Query()[name]
	if !ok || len(response[0]) < 1 {
		errHandler(w, r, "Url param "+name+" was missing")
	}
	return response[0]
}

func templateLoad(filename string, replacement map[string]interface{}) (string, error) {
	content, err := ioutil.ReadFile(filename)
	if err != nil {
		return "", nil
	}
	t := fasttemplate.New(string(content), "{{", "}}")
	s := t.ExecuteString(replacement)
	return string(s), nil
}

//https://ispycode.com/GO/Collections/Arrays/Check-if-item-is-in-array
func contains(arr []string, str string) bool {
	for _, a := range arr {
		if a == str {
			return true
		}
	}
	return false
}