Xojo Plugin

Verify a JWT Created by the Amazon Cognito Service

See more JSON Web Token (JWT) Examples

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

Dim success As Boolean
success = False

// 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:

Dim http As New Chilkat.Http
Dim sbJsonKeys As New Chilkat.StringBuilder
success = http.QuickGetSb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json",sbJsonKeys)
If (success = False) Then
    System.DebugLog(http.LastErrorText)
    Return
End If

Dim jsonKeys As New Chilkat.JsonObject
success = jsonKeys.LoadSb(sbJsonKeys)
jsonKeys.EmitCompact = False
System.DebugLog(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.
Dim jsonKey1 As New Chilkat.JsonObject
success = jsonKeys.ObjectOf2("keys[0]",jsonKey1)

Dim pubKey1 As New Chilkat.PublicKey
success = pubKey1.LoadFromString(jsonKey1.Emit())
If (success = False) Then
    System.DebugLog(pubKey1.LastErrorText)
    Return
End If

System.DebugLog("Success")

Dim jwt As New Chilkat.Jwt

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

// First verify the signature.
Dim sigVerified As Boolean
sigVerified = jwt.VerifyJwtPk(token,pubKey1)
System.DebugLog("verified: " + Str(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.
Dim leeway As Int32
leeway = 60
Dim bTimeValid As Boolean
bTimeValid = jwt.IsTimeValid(token,leeway)
System.DebugLog("time constraints valid: " + Str(bTimeValid))

// Now let's recover the original claims JSON (the payload).
Dim payload As String
payload = jwt.GetPayload(token)
// The payload will likely be in compact form:
System.DebugLog(payload)

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
Dim json As New Chilkat.JsonObject
success = json.Load(payload)
json.EmitCompact = False
System.DebugLog(json.Emit())

// We can recover the original JOSE header in the same way:
Dim joseHeader As String
joseHeader = jwt.GetHeader(token)
// The payload will likely be in compact form:
System.DebugLog(joseHeader)

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
success = json.Load(joseHeader)
json.EmitCompact = False
System.DebugLog(json.Emit())