(Classic ASP) Azure Key Vault Get OAuth2 Access Token using Client Credentials

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Demonstrates how to get an OAuth2 access token using client credentials for an Azure Key Vault resource.

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

' You can use OAuth2 client credentials with an Azure App (service principal) that has
' the required Role-Based Access Control (RBAC) permissions.
' In this case, it would be service principal with RBAC permissions to administer and manage
' the key vault.

' You can create the Azure App (also known as the Service Principal)
' in the Azure CLI (command line interface) as follows:

' ----------------------------------------------------------------------
' az ad sp create-for-rbac --name http://example.com --role Contributor
' ----------------------------------------------------------------------

' The argument to --name must be a valid URI that is a verified domain of your 
' organization or its subdomain.

' The output of the above "az ad sp create-for-rbac ..." command is JSON such as this:

' {
'   "appId": "25ac6e3a-9ac7-42b9-b13e-18644c1de959",
'   "displayName": "azure-cli-2023-10-14-22-38-15",
'   "name": "http://example.com",
'   "password": "f1f2f3f0-52dc-4236-8295-c8a1d6aa393c",
'   "tenant": "4d8dfd66-68d1-13b0-af5c-b31b4b3d53d"
' }

' Save the values in the above JSON.  You'll need it below..

' You'll also want to add the role of "Key Vault Administrator" to the Service Principal
' for the particular key vault.

' ----------------------------------------------------------------------
' az role assignment create --assignee <Application-ID> --role "Key Vault Administrator" 
'       --scope /subscriptions/<Subscription-ID>/resourceGroups/<Resource-Group-Name>/providers/Microsoft.KeyVault/vaults/<KeyVault-Name>
' ----------------------------------------------------------------------

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Http")
set http = Server.CreateObject("Chilkat.Http")
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.HttpRequest")
set req = Server.CreateObject("Chilkat.HttpRequest")

' Add query params to the request.
req.AddParam "grant_type","client_credentials"

' Use the service principal's appId
req.AddParam "client_id","25ac6e3a-9ac7-42b9-b13e-18644c1de959"

' Use the service principal's password.
req.AddParam "client_secret","f1f2f3f0-52dc-4236-8295-c8a1d6aa393c"

' Note: The resource must match the API for which you're using the access token..
req.AddParam "resource","https://vault.azure.net"

success = http.SetUrlVar("tenant","4d8dfd66-68d1-13b0-af5c-b31b4b3d53d")
' resp is a Chilkat.HttpResponse
Set resp = http.PostUrlEncoded("https://login.microsoftonline.com/{$tenant}/oauth2/token",req)
If (http.LastMethodSuccess <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( http.LastErrorText) & "</pre>"
    Response.End
End If

strRespBody = resp.BodyStr
respStatusCode = resp.StatusCode
If (respStatusCode >= 400) Then
    Response.Write "<pre>" & Server.HTMLEncode( "Response Status Code = " & respStatusCode) & "</pre>"
    Response.Write "<pre>" & Server.HTMLEncode( "Response Body:") & "</pre>"
    Response.Write "<pre>" & Server.HTMLEncode( strRespBody) & "</pre>"

    Response.End
End If

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set jsonResp = Server.CreateObject("Chilkat.JsonObject")
success = jsonResp.Load(strRespBody)
jsonResp.EmitCompact = 0
Response.Write "<pre>" & Server.HTMLEncode( jsonResp.Emit()) & "</pre>"

' The result is an access token such as the following:

' {
'   "token_type": "Bearer",
'   "expires_in": "3600",
'   "ext_expires_in": "3600",
'   "expires_on": "1557864616",
'   "not_before": "1557860716",
'   "resource": "https://vault.azure.net",
'   "access_token": "eyJ0eXAiOiJKV1QiL ... 20UFDDOHEyUg"
' }

' If you wish, you can save the token to a file.
' The access token is generally valid for 1 hour.
' After 1 hour, you would need to get a new access token in the same way.
success = jsonResp.WriteFile("qa_data/tokens/azureKeyVaultToken.json")


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