Verify a Square Webhook Signature in Vapor 4.0

SquareWebhookVerification.swift

func validSquareSignature(req: Request) -> Bool {
    guard let headerSignature: String = req.headers["x-square-signature"].first else { return false }
    guard let urlData = "my webhook url".data(using: .utf8) else { return false }
    guard let bodyData = req.body.string?.replacingOccurrences(of: " ", with: "").replacingOccurrences(of: "\n", with: "").data(using: .utf8) else { return false }
    let payload = urlData + bodyData
    var hmac = HMAC<Insecure.SHA1>(key: SymmetricKey(data: EnvVars.squareSig.data(using: .utf8) ?? Data()))
    hmac.update(data: payload)
    let mac = Data(hmac.finalize()).base64EncodedString()
    return mac == headerSignature;
}