(DataFlex) Validate JWS Using HMAC SHA-256

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

Note: This example requires Chilkat v11.0.0 or greater.

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

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoJws
    String sHmacKey
    Integer iSignatureIndex
    String sJwsCompact
    Integer v
    Variant vJoseHeader
    Handle hoJoseHeader
    String sTemp1

    Move False To iSuccess

    // 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.

    Get Create (RefClass(cComChilkatJws)) To hoJws
    If (Not(IsComObjectCreated(hoJws))) Begin
        Send CreateComObject of hoJws
    End

    // Set the HMAC key:
    Move "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow" To sHmacKey
    Move 0 To iSignatureIndex
    Get ComSetMacKey Of hoJws iSignatureIndex sHmacKey "base64url" To iSuccess

    // Load the JWS.
    Move "eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk" To sJwsCompact
    Get ComLoadJws Of hoJws sJwsCompact To iSuccess

    // Validate the 1st (and only) signature at index 0..
    Get ComValidate Of hoJws iSignatureIndex To v
    If (v < 0) Begin
        // Perhaps Chilkat was not unlocked or the trial expired..
        Showln "Method call failed for some other reason."
        Get ComLastErrorText Of hoJws To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    If (v = 0) Begin
        Showln "Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both."
        Procedure_Return
    End

    // If we get here, the signature was validated..
    Showln "Signature validated."

    // Recover the original content:
    Showln "Recovered content:"
    Get ComGetPayload Of hoJws "utf-8" To sTemp1
    Showln sTemp1

    // Examine the protected header:

    Get Create (RefClass(cComChilkatJsonObject)) To hoJoseHeader
    If (Not(IsComObjectCreated(hoJoseHeader))) Begin
        Send CreateComObject of hoJoseHeader
    End
    Get pvComObject of hoJoseHeader to vJoseHeader
    Get ComGetProtectedH Of hoJws iSignatureIndex vJoseHeader To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoJws To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Set ComEmitCompact Of hoJoseHeader To False

    Showln "Protected (JOSE) header:"
    Get ComEmit Of hoJoseHeader To sTemp1
    Showln sTemp1

    // Output:

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


End_Procedure