B4X

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 B4X Downloads

B4X

Dim success As Boolean = False

'  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 ChilkatPublicKey
pubKey.Initialize
success = pubKey.LoadFromFile("qa_data/pem/rsa_public.pem")

Dim jwt As ChilkatJwt
jwt.Initialize

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)
Log("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 Int = 60
Dim bTimeValid As Boolean = jwt.IsTimeValid(token, leeway)
Log("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:
Log(payload)

'  We can format for human viewing by loading it into Chilkat's JSON object
'  and emit.
Dim json As ChilkatJsonObject
json.Initialize
success = json.Load(payload)
json.EmitCompact = False
Log(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:
Log(joseHeader)

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