(VBScript) Verify a JWT Created by the Amazon Cognito Service

Demonstrates how to verify a JWT created by the Amazon Cognito Service.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

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

' The public keys for this example are at https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json
' Let's get them:

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Http")
set http = CreateObject("Chilkat.Http")
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.StringBuilder")
set sbJsonKeys = CreateObject("Chilkat.StringBuilder")
success = http.QuickGetSb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json",sbJsonKeys)
If (success = 0) Then
    outFile.WriteLine(http.LastErrorText)
    WScript.Quit
End If

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set jsonKeys = CreateObject("Chilkat.JsonObject")
success = jsonKeys.LoadSb(sbJsonKeys)
jsonKeys.EmitCompact = 0
outFile.WriteLine(jsonKeys.Emit())

' Here are the keys:

' {
'   "keys": [
'     {
'       "alg": "RS256",
'       "e": "AQAB",
'       "kid": "1A/L5Fsb2EsEwxy5E0cmCMS1BnMe6Jl6NXiMig4iNwU=",
'       "kty": "RSA",
'       "n": "y0w7BJrIJYi ... jKG27z2P3OKw",
'       "use": "sig"
'     },
'     {
'       "alg": "RS256",
'       "e": "AQAB",
'       "kid": "mos6VTJnvDwurY3ghJg6IAPUq+dMwl6CL/iThzJOkzg=",
'       "kty": "RSA",
'       "n": "qbIEH-7tg6yrT ... 3Fj94ooTd0w",
'       "use": "sig"
'     }
'   ]
' }

' Try the 1st key.
' jsonKey1 is a Chilkat.JsonObject
Set jsonKey1 = jsonKeys.ObjectOf("keys[0]")
If (jsonKeys.LastMethodSuccess = 0) Then
    outFile.WriteLine("Did not get the 1st JSON public key.")
    WScript.Quit
End If

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.PublicKey")
set pubKey1 = CreateObject("Chilkat.PublicKey")
success = pubKey1.LoadFromString(jsonKey1.Emit())
If (success = 0) Then
    outFile.WriteLine(pubKey1.LastErrorText)
    WScript.Quit
End If

outFile.WriteLine("Success")

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Jwt")
set jwt = CreateObject("Chilkat.Jwt")

' I did not include the an actual AWS Cognito token here because our test sample used customer-provided data..
token = "eyJ..asXg"

' First verify the signature.
sigVerified = jwt.VerifyJwtPk(token,pubKey1)
outFile.WriteLine("verified: " & sigVerified)

' Let's see if the time constraints, if any, are valid.
' The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
' If the current system time is before the "nbf" time, or after the "exp" time,
' then IsTimeValid will return false/0.
' Also, we'll allow a leeway of 60 seconds to account for any clock skew.
' Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
leeway = 60
bTimeValid = jwt.IsTimeValid(token,leeway)
outFile.WriteLine("time constraints valid: " & bTimeValid)

' Now let's recover the original claims JSON (the payload).
payload = jwt.GetPayload(token)
' The payload will likely be in compact form:
outFile.WriteLine(payload)

' We can format for human viewing by loading it into Chilkat's JSON object
' and emit.
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set json = CreateObject("Chilkat.JsonObject")
success = json.Load(payload)
json.EmitCompact = 0
outFile.WriteLine(json.Emit())

' We can recover the original JOSE header in the same way:
joseHeader = jwt.GetHeader(token)
' The payload will likely be in compact form:
outFile.WriteLine(joseHeader)

' We can format for human viewing by loading it into Chilkat's JSON object
' and emit.
success = json.Load(joseHeader)
json.EmitCompact = 0
outFile.WriteLine(json.Emit())

outFile.Close