(Xojo Plugin) Validate JWS Using HMAC SHA-256

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

Note: This example requires Chilkat v9.5.0.66 or greater.

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

// Note: This example requires Chilkat v9.5.0.66 or greater.

// 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 New Chilkat.Jws

// Set the HMAC key:
Dim hmacKey As String
hmacKey = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
Dim signatureIndex As Int32
signatureIndex = 0
Dim success As Boolean
success = jws.SetMacKey(signatureIndex,hmacKey,"base64url")

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

// Validate the 1st (and only) signature at index 0..
Dim v As Int32
v = jws.Validate(signatureIndex)
If (v < 0) Then
    // Perhaps Chilkat was not unlocked or the trial expired..
    System.DebugLog("Method call failed for some other reason.")
    System.DebugLog(jws.LastErrorText)
    Return
End If

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

// If we get here, the signature was validated..
System.DebugLog("Signature validated.")

// Recover the original content:
System.DebugLog("Recovered content:")
System.DebugLog(jws.GetPayload("utf-8"))

// Examine the protected header:
Dim joseHeader As Chilkat.JsonObject
joseHeader = jws.GetProtectedHeader(signatureIndex)
If (jws.LastMethodSuccess <> True) Then
    System.DebugLog("No protected header found at the given index.")
    Return
End If

joseHeader.EmitCompact = False

System.DebugLog("Protected (JOSE) header:")
System.DebugLog(joseHeader.Emit())

// Output:

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