How to acquire OAuth2.0 token from Azure AD in Go? - go

Question

I am attempting to consume Azure service bus entity using Go. Authentication with Azure service bus is possible by supplying either an SAS token or an Azure AD OAuth2.0 token, which will be obtained via the security principals of Azure AD app. Technically I prefer the security principals option rather than an SAS token as it has security vulnerabilities.
How do I acquire an OAuth2.0 token from Azure AD using Go for which Azure AD SDK is not available?
Is it possible to make a direct call to Azure AD REST APIs to access an OAuth2.0 token?

Answer 1

There are some methods to get access token using Go.
1. Use Http Request
For example with authorization code flow, the whole code sample here:
func GetTokens(c AuthorizationConfig, authCode AuthorizationCode, scope string) (t Tokens, err error) {
formVals := url.Values{}
formVals.Set("code", authCode.Value)
formVals.Set("grant_type", "authorization_code")
formVals.Set("redirect_uri", c.RedirectURL())
formVals.Set("scope", scope)
if c.ClientSecret != "" {
formVals.Set("client_secret", c.ClientSecret)
}
formVals.Set("client_id", c.ClientID)
response, err := http.PostForm(TokenURL, formVals)
if err != nil {
return t, errors.Wrap(err, "error while trying to get tokens")
}
body, err := ioutil.ReadAll(response.Body)
if err != nil {
return t, errors.Wrap(err, "error while trying to read token json body")
}
err = json.Unmarshal(body, &t)
if err != nil {
return t, errors.Wrap(err, "error while trying to parse token json body")
}
return
}
2. Use MSAL Go
// 1.1 Initializing a public client:
publicClientapp, err := public.New("client_id", public.WithAuthority("https://login.microsoftonline.com/Enter_The_Tenant_Name_Here"))
// 1.2 Initializing a confidential client:
confidentialClientApp, err := confidential.New("client_id", cred, confidential.WithAuthority("https://login.microsoftonline.com/Enter_The_Tenant_Name_Here"))
// 2. MSAL comes packaged with an in-memory cache. Utilizing the cache is optional, but we would highly recommend it.
var userAccount public.Account
accounts := publicClientApp.Accounts()
if len(accounts) > 0 {
// Assuming the user wanted the first account
userAccount = accounts[0]
// found a cached account, now see if an applicable token has been cached
result, err := publicClientApp.AcquireTokenSilent(context.Background(), []string{"your_scope"}, public.WithSilentAccount(userAccount))
accessToken := result.AccessToken
}
// 3. If there is no suitable token in the cache, or you choose to skip this step, now we can send a request to AAD to obtain a token.
result, err := publicClientApp.AcquireToken"ByOneofTheActualMethods"([]string{"your_scope"}, ...(other parameters depending on the function))
if err != nil {
log.Fatal(err)
}
accessToken := result.AccessToken
Last, Azure SDK for Go seems used to authenticate with Azure, but it doesn't provide a SDK method to acquire an access token.