Authenticating to Azure in Go using REST API - azure

Question

I am trying to authenticate to Azure service management / graph API using golang.
Using purely REST APIs.
No matter what I do, I always end up with error:
{"error":"invalid_request","error_description":"AADSTS900144: The request body must contain the following parameter: 'grant_type'.
Since I am not using SDK there is limited samples out there. Any help would be appreciated.
package main
import (
"bytes"
"encoding/json"
"io/ioutil"
"log"
"net/http"
)
func main() {
authendpoint := "https://login.microsoftonline.com/8xxxxx7-6372-4bcb-xxx-xxxxxx/oauth2/token"
jsonData := []byte(`{
"resource": "https://graph.microsoft.com",
"client_id": "xxxxxxxx-7549-4ea2-b00d-xxxxxxxxxxx",
"client_secret": "Q.xxxxxxxxxxxxxx-6_CgA4yOi_8sS-",
"grant_type": "client_credentials",
}`)
request, err := http.NewRequest("POST", authendpoint, bytes.NewBuffer(jsonData))
request.Header.Set("Content-Type", "application/json")
client := &http.Client{}
resp, err := client.Do(request)
if err != nil {
log.Fatal(err)
}
body, err := ioutil.ReadAll(resp.Body)
var res map[string]interface{}
json.NewDecoder(resp.Body).Decode(&res)
log.Println(string(body))
}

Answer 1

The Microsoft request docs posted by Praveen Premaratne show the request needs to be formatted using Content-Type: application/x-www-form-urlencoded which is a requirement for the OAuth 2.0 standard.
Here's the Microsoft docs and example:
https://learn.microsoft.com/en-us/graph/auth/auth-concepts#register-your-app-with-the-microsoft-identity-platform
POST /common/oauth2/v2.0/token HTTP/1.1
Host: https://login.microsoftonline.com
Content-Type: application/x-www-form-urlencoded
client_id=6731de76-14a6-49ae-97bc-6eba6914391e
&scope=user.read%20mail.read
&code=OAAABAAAAiL9Kn2Z27UubvWFPbm0gLWQJVzCTE9UkP3pSx1aXxUjq3n8b2JRLk4OxVXr...
&redirect_uri=http%3A%2F%2Flocalhost%2Fmyapp%2F
&grant_type=authorization_code
&client_secret=JqQX2PNo9bpM0uEihUPzyrh
Here's how to accomplish this:
package main
import (
"fmt"
"net/http"
"net/url"
"strings"
)
func main() {
authendpoint := "https://login.microsoftonline.com/8xxxxx7-6372-4bcb-xxx-xxxxxx/oauth2/token"
body := url.Values(map[string][]string{
"resource": {"https://graph.microsoft.com"},
"client_id": {"xxxxxxxx-7549-4ea2-b00d-xxxxxxxxxxx"},
"client_secret": {"Q.xxxxxxxxxxxxxx-6_CgA4yOi_8sS-"},
"grant_type": {"client_credentials"}})
request, err := http.NewRequest(
http.MethodPost,
authendpoint,
strings.NewReader(body.Encode()))
if err != nil {
panic(err)
}
request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
client := &http.Client{}
resp, err := client.Do(request)
if err != nil {
panic(err)
}
fmt.Println(resp.StatusCode)
}

Answer 2

for me, it worked when I removed resource from the request body and added scope as new parameter in body.