Sesame-Server/Sources/App/configure.swift

import Vapor

var deviceManager: DeviceManager!

enum ServerError: Error {
    case invalidAuthenticationFileContent
    case invalidAuthenticationToken
}

// configures your application
public func configure(_ app: Application) throws {
    let storageFolder = URL(fileURLWithPath: app.directory.resourcesDirectory)
    let logFolder = storageFolder.appendingPathComponent("logs")


    let configUrl = storageFolder.appendingPathComponent("config.json")
    let config = try Config(loadFrom: configUrl)

    app.http.server.configuration.port = config.port

    let keyFile = storageFolder.appendingPathComponent(config.keyFileName)

    let (deviceKey, remoteKey) = try loadKeys(at: keyFile)
    deviceManager = DeviceManager(deviceKey: deviceKey, remoteKey: remoteKey, deviceTimeout: config.deviceTimeout)
    try routes(app)
    
    // Gracefully shut down by closing potentially open socket
    DispatchQueue.global(qos: .utility).asyncAfter(deadline: .now() + .seconds(5)) {
        _ = app.server.onShutdown.always { _ in
            deviceManager.removeDeviceConnection()
        }
    }
}

private func loadKeys(at url: URL) throws -> (deviceKey: Data, remoteKey: Data) {
    let authContent: [Data] = try String(contentsOf: url)
        .trimmingCharacters(in: .whitespacesAndNewlines)
        .components(separatedBy: "\n")
        .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
        .map {
            guard let key = Data(fromHexEncodedString: $0) else {
                throw ServerError.invalidAuthenticationToken
            }
            guard key.count == SHA256.byteCount else {
                throw ServerError.invalidAuthenticationToken
            }
            return key
        }
    guard authContent.count == 2 else {
        throw ServerError.invalidAuthenticationFileContent
    }
    return (deviceKey: authContent[0], remoteKey: authContent[1])
}