# TunnelKit
[](https://www.openssl.org/news/openssl-1.1.0-notes.html)
[](LICENSE)
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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] 1.1.0i, which in turn enables support for a certain range of encryption and digest algorithms.
## Getting started
The client is known to work with [OpenVPN®][openvpn] 2.3+ servers.
- [x] Handshake and tunneling over UDP or TCP
- [x] Ciphers
- AES-CBC (128/192/256 bit)
- AES-GCM (128/192/256 bit, 2.4)
- [x] HMAC digests
- SHA-1
- SHA-2 (224/256/384/512 bit)
- [x] NCP (Negotiable Crypto Parameters, 2.4)
- Server-side
- [x] TLS handshake
- Server validation (CA, EKU)
- Client certificate
- [x] TLS wrapping
- Authentication (`--tls-auth`)
- Encryption (`--tls-crypt`)
- [x] Compression framing
- Via `--comp-lzo` (deprecated in 2.4)
- Via `--compress`
- [x] Compression algorithms
- LZO (via `--comp-lzo` or `--compress lzo`)
- [x] Key renegotiation
- [x] Replay protection (hardcoded window)
The library therefore supports compression framing, just not newer compression. Remember to match server-side compression and framing, otherwise the client will shut down with an error. E.g. if server has `comp-lzo no`, client must use `compressionFraming = .compLZO`.
### Support for .ovpn configuration
TunnelKit can parse .ovpn configuration files. Below are a few limitations worth mentioning.
Unsupported:
- UDP fragmentation, i.e. `--fragment`
- Compression via `--compress` other than empty or `lzo`
- Proxy
- External file references (inline `` only)
- `` blocks
Ignored:
- MTU overrides
- `--*-mtu` and variants
- `--mssfix`
- Multiple `--remote` with different `host` values (first wins)
- Custom `--redirect-gateway`, VPN is always default gateway (no [split tunnelling][issue-55] yet)
Many other flags are ignored too but it's normally not an issue.
## Installation
### Requirements
- iOS 11.0+ / macOS 10.11+
- Xcode 10+ (Swift 5)
- Git (preinstalled with Xcode Command Line Tools)
- Ruby (preinstalled with macOS)
- [CocoaPods 1.6.0][dep-cocoapods]
- [jazzy][dep-jazzy] (optional, for documentation)
- [Disable Bitcode][issue-51]
It's highly recommended to use the Git and Ruby packages provided by [Homebrew][dep-brew].
### CocoaPods
To use with CocoaPods just add this to your Podfile:
```ruby
pod 'TunnelKit'
```
### Testing
Download the library codebase locally:
$ git clone https://github.com/keeshux/tunnelkit.git
Assuming you have a [working CocoaPods environment][dep-cocoapods], setting up the library workspace only requires installing the pod dependencies:
$ pod install
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.
#### Demo
There is a `Demo` directory containing a simple app for testing the tunnel, called `BasicTunnel`. As usual, prepare for CocoaPods:
$ pod install
then open `Demo.xcworkspace` and run the `BasicTunnel-iOS` target.
For the VPN to work properly, the `BasicTunnel` demo requires:
- _App Groups_ and _Keychain Sharing_ capabilities
- App IDs with _Packet Tunnel_ entitlements
both in the main app and the tunnel extension target.
In order to test connection to your own server, modify the file `Demo/BasicTunnel-[iOS|macOS]/ViewController.swift` and make sure to set `ca` to the PEM encoded certificate of your VPN server's CA.
Example:
private let ca = CryptoContainer(pem: """
-----BEGIN CERTIFICATE-----
MIIFJDCC...
-----END CERTIFICATE-----
""")
Make sure to also update the following constants in the same files, according to your developer account and your target bundle identifiers:
public static let appGroup
public static let tunnelIdentifier
Remember that the App Group on macOS requires a team ID prefix.
## Documentation
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.
### AppExtension
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 the App Group container.
### LZO
Due to the restrictive license (GPLv2), LZO support is provided as an optional subspec.
## License
### Part I
This project is licensed under the [GPLv3][license-content].
### Part II
As seen in [libsignal-protocol-c][license-signal]:
> Additional Permissions For Submission to Apple App Store: Provided that you are otherwise in compliance with the GPLv3 for each covered work you convey (including without limitation making the Corresponding Source available in compliance with Section 6 of the GPLv3), the Author also grants you the additional permission to convey through the Apple App Store non-source executable versions of the Program as incorporated into each applicable covered work as Executable Versions only under the Mozilla Public License version 2.0 (https://www.mozilla.org/en-US/MPL/2.0/).
### Part III
Part I and II do not apply to the LZO library, which remains licensed under the terms of the GPLv2+.
### Contributing
By contributing to this project you are agreeing to the terms stated in the [Contributor License Agreement (CLA)][contrib-cla].
For more details please see [CONTRIBUTING][contrib-readme].
## Credits
- [PIATunnel][dep-piatunnel-repo] - Copyright (c) 2018-Present Private Internet Access
- [SwiftyBeaver][dep-swiftybeaver-repo] - Copyright (c) 2015 Sebastian Kreutzberger
- [lzo][dep-lzo-website] - Copyright (c) 1996 - 2017 Markus F.X.J. Oberhumer
This product includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit. ([https://www.openssl.org/][dep-openssl])
© 2002-2018 OpenVPN Inc. - OpenVPN is a registered trademark of OpenVPN Inc.
## Contacts
Twitter: [@keeshux][about-twitter]
Website: [davidederosa.com][about-website]
[openvpn]: https://openvpn.net/index.php/open-source/overview.html
[dep-cocoapods]: https://guides.cocoapods.org/using/getting-started.html
[dep-jazzy]: https://github.com/realm/jazzy
[dep-brew]: https://brew.sh/
[dep-openssl]: https://www.openssl.org/
[issue-51]: https://github.com/keeshux/tunnelkit/issues/51
[issue-55]: https://github.com/keeshux/tunnelkit/issues/55
[ne-home]: https://developer.apple.com/documentation/networkextension
[ne-ptp]: https://developer.apple.com/documentation/networkextension/nepackettunnelprovider
[ne-udp]: https://developer.apple.com/documentation/networkextension/nwudpsession
[ne-tcp]: https://developer.apple.com/documentation/networkextension/nwtcpconnection
[license-content]: LICENSE
[license-signal]: https://github.com/signalapp/libsignal-protocol-c#license
[license-mit]: https://choosealicense.com/licenses/mit/
[contrib-cla]: CLA.rst
[contrib-readme]: CONTRIBUTING.md
[dep-piatunnel-repo]: https://github.com/pia-foss/tunnel-apple
[dep-swiftybeaver-repo]: https://github.com/SwiftyBeaver/SwiftyBeaver
[dep-lzo-website]: http://www.oberhumer.com/opensource/lzo/
[about-twitter]: https://twitter.com/keeshux
[about-website]: https://davidederosa.com
[about-patreon]: https://www.patreon.com/keeshux