B4X

Verify JWT Using HS256, HS384, or HS512

See more JSON Web Token (JWT) Examples

Demonstrates how to verify a JWT that was signed using HS256, HS384, or HS512. (HS256 is JWT's acronym for HMAC-SHA256.)

This example verifies the 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.

B4X

Dim success As Boolean = False

'  Demonstrates how to verify an HMAC JWT using a shared secret (password).

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

Dim jwt As ChilkatJwt
jwt.Initialize

Dim token As String = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU"

'  First verify the signature.
'  The password used to create this JWT was "secret".
Dim sigVerified As Boolean = jwt.VerifyJwt(token, "secret")
Log("with correct password: " & sigVerified)

'  Now try with a different password:
sigVerified = jwt.VerifyJwt(token, "secret2")
Log("with incorrect password " & 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)