(Visual FoxPro) 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.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loJws
LOCAL lcHmacKey
LOCAL lnSignatureIndex
LOCAL lcJwsCompact
LOCAL lnSuccess
LOCAL v
LOCAL loJoseHeader

* 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.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Jws')
loJws = CreateObject('Chilkat.Jws')

* Set the HMAC key:
lcHmacKey = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
lnSignatureIndex = 0
loJws.SetMacKey(lnSignatureIndex,lcHmacKey,"base64url")

* Load the JWS.
lcJwsCompact = "eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk"
lnSuccess = loJws.LoadJws(lcJwsCompact)

* Validate the 1st (and only) signature at index 0..
v = loJws.Validate(lnSignatureIndex)
IF (v < 0) THEN
    * Perhaps Chilkat was not unlocked or the trial expired..
    ? "Method call failed for some other reason."
    ? loJws.LastErrorText
    RELEASE loJws
    CANCEL
ENDIF

IF (v = 0) THEN
    ? "Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both."
    RELEASE loJws
    CANCEL
ENDIF

* If we get here, the signature was validated..
? "Signature validated."

* Recover the original content:
? "Recovered content:"
? loJws.GetPayload("utf-8")

* Examine the protected header:
loJoseHeader = loJws.GetProtectedHeader(lnSignatureIndex)
IF (loJws.LastMethodSuccess <> 1) THEN
    ? "No protected header found at the given index."
    RELEASE loJws
    CANCEL
ENDIF

loJoseHeader.EmitCompact = 0

? "Protected (JOSE) header:"
? loJoseHeader.Emit()
RELEASE loJoseHeader

* Output:

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

RELEASE loJws