(Excel) PRODA Get OAuth2 Access Token using JWT

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Demonstrates how to get an OAuth2 access token for the PRODA Australian Government Online Services using a JWT.

For more information, see https://www.servicesaustralia.gov.au/organisations/business/services/proda-provider-digital-access

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

' First create a JWT to be sent in the POST to https://vnd.proda.humanservices.gov.au/mga/sps/oauth/oauth20/token

Dim privKey As Chilkat.PrivateKey
Set privKey = Chilkat.NewPrivateKey

' Load an RSA private key from a PEM file.
' Chilkat provides alternative methods to load from other formats, or to load from a string or binary data.

success = privKey.LoadEncryptedPemFile("qa_data/pem/rsa_passwd.pem","passwd")
If (success <> True) Then
    Debug.Print privKey.LastErrorText
    Exit Sub
End If

Dim jwt As Chilkat.Jwt
Set jwt = Chilkat.NewJwt

' Build the JOSE header
Dim jose As Chilkat.JsonObject
Set jose = Chilkat.NewJsonObject
' Use RS256.  Pass the string "RS384" or "RS512" to use RSA with SHA-384 or SHA-512.
success = jose.AppendString("alg","RS256")
success = jose.AppendString("typ","JWT")
success = jose.AppendString("kid","test-device")

' Now build the JWT claims (also known as the payload)
Dim claims As Chilkat.JsonObject
Set claims = Chilkat.NewJsonObject
success = claims.AppendString("iss","9646844092")
success = claims.AppendString("sub","test-device")
success = claims.AppendString("aud","https://proda.humanservices.gov.au")

' Set the timestamp of when the JWT was created to now.

curDateTime = jwt.GenNumericDate(0)
success = claims.AddIntAt(-1,"iat",curDateTime)

' Set the timestamp defining an expiration time (end time) for the token
' to be now + 1 hour (3600 seconds)
success = claims.AddIntAt(-1,"exp",curDateTime + 3600)

' Produce the smallest possible JWT:
jwt.AutoCompact = True

' Create the JWT token.  This is where the RSA signature is created.

jwtToken = jwt.CreateJwtPk(jose.Emit(),claims.Emit(),privKey)

' ---------------------------------------------------------------------
' Build and send the POST, which should look something like this:

' POST https://vnd.proda.humanservices.gov.au/mga/sps/oauth/oauth20/token HTTP/1.1
' Content-Type: application/x-www-form-urlencoded
' Content-Length: 666
' Host: vnd.proda.humanservices.gov.au
' 
' grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer&assertion=<jwt>&client_id=VendorClient03

Dim http As Chilkat.Http
Set http = Chilkat.NewHttp

Dim req As Chilkat.HttpRequest
Set req = Chilkat.NewHttpRequest

' Add the request params.
req.AddParam "grant_type","urn:ietf:params:oauth:grant-type:jwt-bearer"
req.AddParam "assertion",jwtToken
req.AddParam "client_id","VendorClient03"

' Send the POST
' Chilkat automatically adds the Content-Type (which is application/x-www-form-urlencoded for the PostUrlEncoded method)
' Chilkat also automatically adds the Host and Content-Length headers.

Set resp = http.PostUrlEncoded("https://vnd.proda.humanservices.gov.au/mga/sps/oauth/oauth20/token",req)
If (http.LastMethodSuccess <> True) Then
    Debug.Print http.LastErrorText
    Exit Sub
End If

Debug.Print "Response status code = "; resp.StatusCode
Debug.Print "Response body:"
Debug.Print resp.BodyStr