B4X

Get Access Token using a Pre-Created JSON Web Token

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Demonstrates how to get an access token using a pre-created JSON Web Token (JWT). B4X

Dim success As Boolean = False

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

'  We're going to duplicate this CURL statement:
'  curl -X POST https://api-sandbox.abnamro.com/v1/oauth/token \
'  -H "Content-Type: application/x-www-form-urlencoded" \
'  -H "API-Key: xxxxxx" \
'  -d 'client_assertion_type=urn:ietf:params:oauth:client-assertion-type:jwt-bearer&grant_type=client_credentials&client_assertion=eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ4eHh4eHgiLCJleHAiOiIxNDk5OTQ3NjY4IiwiaXNzIjoibWUiLCJhdWQiOiJodHRwczovL2F1dGgtc2FuZGJveC5hYm5hbXJvLmNvbS9vYXV0aC90b2tlbiJ9.jGwHKG_YjgKpR8NPpaLu6nJ97obeP2vcxg6fOWBKdJ0&scope=tikkie'

'  Load our pre-creaed private key PEM file.
'  Note: Please share your public key along with your app name and developer email id at api.support@nl.abnamro.com. 
'  Token generation will not work unless public key is associated with your app.
Dim privkey As ChilkatPrivateKey
privkey.Initialize("privkey")

success = privkey.LoadPemFile("qa_data/pem/abnAmroPrivateKey.pem")
If success = False Then
    Log(privkey.LastErrorText)
    Return
End If


'  Create the JWT.
Dim jwt As ChilkatJwt
jwt.Initialize

'  Create the header:
'  {
'      "typ": "JWT",
'      "alg": "RS256"
'  }
Dim jsonHeader As ChilkatJsonObject
jsonHeader.Initialize
jsonHeader.UpdateString("typ", "JWT")
jsonHeader.UpdateString("alg", "RS256")

'  Create the payload:
'  {
'      "nbf": 1499947668,
'      "exp": 1499948668,
'      "iss": "me",
'      "sub": "anApiKey",
'      "aud": "https://auth-sandbox.abnamro.com/oauth/token"
'  }
Dim jsonPayload As ChilkatJsonObject
jsonPayload.Initialize

Dim curDateTime As Int = jwt.GenNumericDate(0)

'  Set the "not process before" timestamp to now.
success = jsonPayload.AddIntAt(-1, "nbf", curDateTime)

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

jsonPayload.UpdateString("iss", "me")
jsonPayload.UpdateString("sub", "anApiKey")
jsonPayload.UpdateString("aud", "https://auth-sandbox.abnamro.com/oauth/token")

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

Dim jwtStr As String = jwt.CreateJwtPk(jsonHeader.Emit, jsonPayload.Emit, privkey)
If jwt.LastMethodSuccess = False Then
    Log(jwt.LastErrorText)
    Return
End If


Dim http As ChilkatHttp
http.Initialize("http")

Dim req As ChilkatHttpRequest
req.Initialize
req.AddParam("client_assertion_type", "urn:ietf:params:oauth:client-assertion-type:jwt-bearer")
req.AddParam("grant_type", "client_credentials")
req.AddParam("client_assertion", jwtStr)
req.AddParam("scope", "tikkie")

req.HttpVerb = "POST"
req.ContentType = "application/x-www-form-urlencoded"

Dim resp As ChilkatHttpResponse
resp.Initialize
success = http.HttpReq("https://api-sandbox.abnamro.com/v1/oauth/token", req, resp)
If success = False Then
    Log(http.LastErrorText)
    Return
End If


If resp.StatusCode <> 200 Then
    Log(resp.BodyStr)
    Return
End If


'  Get the JSON result:
'  {
'      "access_token": "{your access token}",
'      "expires_in": "{duration of validity in seconds}",
'      "scope": "{scope(s) for which the access token is valid}",
'      "token_type": "{it is always Bearer}"
'  }
Dim json As ChilkatJsonObject
json.Initialize
json.Load(resp.BodyStr)
Log("access_token: " & json.StringOf("access_token"))
Log("token_type: " & json.StringOf("token_type"))
Log("expires_in: " & json.StringOf("expires_in"))
Log("scope: " & json.StringOf("scope"))