(PureBasic) 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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IncludeFile "CkJws.pb"
IncludeFile "CkJsonObject.pb"

Procedure ChilkatExample()

    ; 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.

    jws.i = CkJws::ckCreate()
    If jws.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Set the HMAC key:
    hmacKey.s = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
    signatureIndex.i = 0
    CkJws::ckSetMacKey(jws,signatureIndex,hmacKey,"base64url")

    ; Load the JWS.
    jwsCompact.s = "eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk"
    success.i = CkJws::ckLoadJws(jws,jwsCompact)

    ; Validate the 1st (and only) signature at index 0..
    v.i = CkJws::ckValidate(jws,signatureIndex)
    If v < 0
        ; Perhaps Chilkat was not unlocked or the trial expired..
        Debug "Method call failed for some other reason."
        Debug CkJws::ckLastErrorText(jws)
        CkJws::ckDispose(jws)
        ProcedureReturn
    EndIf

    If v = 0
        Debug "Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both."
        CkJws::ckDispose(jws)
        ProcedureReturn
    EndIf

    ; If we get here, the signature was validated..
    Debug "Signature validated."

    ; Recover the original content:
    Debug "Recovered content:"
    Debug CkJws::ckGetPayload(jws,"utf-8")

    ; Examine the protected header:
    joseHeader.i = CkJws::ckGetProtectedHeader(jws,signatureIndex)
    If CkJws::ckLastMethodSuccess(jws) <> 1
        Debug "No protected header found at the given index."
        CkJws::ckDispose(jws)
        ProcedureReturn
    EndIf

    CkJsonObject::setCkEmitCompact(joseHeader, 0)

    Debug "Protected (JOSE) header:"
    Debug CkJsonObject::ckEmit(joseHeader)
    CkJsonObject::ckDispose(joseHeader)

    ; Output:

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


    CkJws::ckDispose(jws)


    ProcedureReturn
EndProcedure