(VB.NET) Verify JWT Using an RSA Public Key (RS256, RS384, RS512)

Demonstrates how to verify a JWT that was signed using an RSA private key.

This example verifies the RSA signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original claims JSON.

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

' Demonstrates how to verify an JWT using an RSA public key.

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


Dim pubKey As New Chilkat.PublicKey
Dim success As Boolean = pubKey.LoadFromFile("qa_data/pem/rsa_public.pem")

Dim jwt As New Chilkat.Jwt

Dim token As String = "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDQ1MjM4LCJuYmYiOjE0NjM0NDUyMzgsImV4cCI6MTQ2MzQ0ODgzOH0.XRtqed6nuJ9lrp0wbNdDX3fCkSh_d9cHAniPbNcqm7G-5N3mtI5ntQvZBDP3pHtECVqufuDwW7XgUtzAi0ZXhyiRm1iZ3wMSN5lHWv52OQJmMHPA7VPd8Q1hDG-tx-QswzJKd75OEUHP7wIXq2Mg_YVElfDvJI6TGjGyS1y-RLHlz-ldlGsEwIBkO0PtzIYTVov97x8p9KCsPNhS4lZUIqKOYoTZUV5LpuAWARl-636DfMEB_A5_IEaw_W8leh2suP2ULVZxwE-Tk1kBC9tsSGrBrPTtg7sziaV4Lbb0JRANmh98uTRu5f8ji9CVOnpbMiAzjsJSy56kz_olweXSuA"

' First verify the signature.
Dim sigVerified As Boolean = jwt.VerifyJwtPk(token,pubKey)
Debug.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.
Dim leeway As Integer = 60
Dim bTimeValid As Boolean = jwt.IsTimeValid(token,leeway)
Debug.WriteLine("time constraints valid: " & bTimeValid)

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

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

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