B4X Requires Chilkat v11.0.0+

Validate JWS Using HMAC SHA-256

See more JSON Web Signatures (JWS) Examples

Validates a JSON Web Signature (JWS) using HMAC SHA-256. B4X

Dim success As Boolean = False

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

'  This example takes a JSON signature in compact serialization format,
'  and uses a MAC key to validate and recover the protected header and payload.

Dim jws As ChilkatJws
jws.Initialize

'  Set the HMAC key:
Dim hmacKey As String = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
Dim signatureIndex As Int = 0
jws.SetMacKey(signatureIndex, hmacKey, "base64url")

'  Load the JWS.
Dim jwsCompact As String = "eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk"
success = jws.LoadJws(jwsCompact)

'  Validate the 1st (and only) signature at index 0..
Dim v As Int = jws.Validate(signatureIndex)
If v < 0 Then
    '  Perhaps Chilkat was not unlocked or the trial expired..
    Log("Method call failed for some other reason.")
    Log(jws.LastErrorText)
    Return
End If

If v = 0 Then
    Log("Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both.")
    Return
End If


'  If we get here, the signature was validated..
Log("Signature validated.")

'  Recover the original content:
Log("Recovered content:")
Log(jws.GetPayload("utf-8"))

'  Examine the protected header:

Dim joseHeader As ChilkatJsonObject
joseHeader.Initialize
success = jws.GetProtectedH(signatureIndex, joseHeader)
If success = False Then
    Log(jws.LastErrorText)
    Return
End If


joseHeader.EmitCompact = False

Log("Protected (JOSE) header:")
Log(joseHeader.Emit)

'  Output:

'  	Signature validated.
'  	Recovered content:
'  	{"iss":"joe",
'  	 "exp":1300819380,
'  	 "http://example.com/is_root":true}
'  	Protected (JOSE) header:
'  	{ 
'  	  "typ": "JWT",
'  	  "alg": "HS256"
'  	}