This library provides a simplified Swift/Obj-C implementation of the OpenVPN® protocol for the Apple platforms. The crypto layer is built on top of [OpenSSL][dep-openssl] 1.1.0h, which in turn enables support for a certain range of encryption and digest algorithms.
The client is known to work with [OpenVPN®][openvpn] 2.3+ servers. Key renegotiation and replay protection are also included, but full-fledged configuration files (.ovpn) are not currently supported.
The library therefore supports compression framing, just not compression. Remember to match server-side compression framing in order to avoid a confusing loss of data packets. E.g. if server has `comp-lzo no`, client must use `compressionFraming = .compLZO`.
After that, open `TunnelKit.xcworkspace` in Xcode and run the unit tests found in the `TunnelKitTests` target. A simple CMD+U while on `TunnelKit-iOS` should do that as well.
In order to test connection to your own server, modify the file `Demo/BasicTunnel-[iOS|macOS]/ViewController.swift` and make sure to set `builder.ca` to the PEM encoded certificate of your VPN server's CA (or `nil` to skip CA validation, however discouraged).
The library is split into two modules, in order to decouple the low-level protocol implementation from the platform-specific bridging, namely the [NetworkExtension][ne-home] VPN framework.
Full documentation of the public interface is available and can be generated with [jazzy][dep-jazzy]. After installing the jazzy Ruby gem with:
$ gem install jazzy
enter the root directory of the repository and run:
$ jazzy
The generated output is stored into the `docs` directory in HTML format.
### Core
Here you will find the low-level entities on top of which the connection is established. Code is mixed Swift and Obj-C, most of it is not exposed to consumers. The *Core* module depends on OpenSSL and is mostly platform-agnostic.
The entry point is the `SessionProxy` class. The networking layer is fully abstract and delegated externally with the use of opaque `IOInterface` (`LinkInterface` and `TunnelInterface`) and `SessionProxyDelegate` protocols.
The goal of this module is packaging up a black box implementation of a [NEPacketTunnelProvider][ne-ptp], which is the essential part of a Packet Tunnel Provider app extension. You will find the main implementation in the `TunnelKitProvider` class.
Currently, the extension supports VPN over both [UDP][ne-udp] and [TCP][ne-tcp] sockets. A debug log snapshot is optionally maintained and shared to host apps via `UserDefaults` in a shared App Group.
This project is licensed under the [GPLv3 license][license-gpl3], which can be found [here][license-content]. I can provide a different license on request, e.g. if you want to use the library on the App Store. Feel free to contact me in such case.
- [PIATunnel][dep-piatunnel-repo] - TunnelKit is a hard fork of PIATunnel that repurposes it substantially. PIATunnel is licensed under the [MIT (Expat) license][license-mit], which can be found [here][dep-piatunnel-license].
- [SwiftyBeaver][dep-swiftybeaver-repo] - A convenient logging library.
