mirror of
https://github.com/OpenVPN/openvpn3.git
synced 2024-09-19 19:52:15 +02:00
be3f20dc58
The need of having to call the assert_crypto() member function to ensure that a cryptographically strong RNG is used where needed, was reported as potentially insecure, since calling it manually can easily be missed. In the commit the two new classes StrongRandomAPI and WeakRandomAPI are introduced. They are to be used instead of just RandomAPI, unless it doesn't matter what strength the RNG is. All the places the assert_crypto() was called were converted to using StrongRandomAPI instead. Also the RNGs for which assert_crypto() was not throwing are now inheriting from StrongRandomAPI. Variable names, which have the StrongRandomAPI type, but were called prng, are changed to rng instead to follow the source code convention. Signed-off-by: Heiko Hund <heiko@openvpn.net>
612 lines
18 KiB
ReStructuredText
612 lines
18 KiB
ReStructuredText
OpenVPN 3
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=========
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OpenVPN 3 is a C++ class library that implements the functionality
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of an OpenVPN client, and is protocol-compatible with the OpenVPN
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2.x branch.
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OpenVPN 3 includes a minimal client wrapper (``cli``) that links in with
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the library and provides basic command line functionality.
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OpenVPN 3 is currently used in production as the core of the
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OpenVPN Connect clients for iOS, Android, Linux, Windows, and Mac OS X.
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NOTE: OpenVPN 3 does not currently implement server functionality.
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.. contents:: Table of Contents
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OpenVPN 3 Client API
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--------------------
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OpenVPN 3 is organized as a C++ class library, and the API is defined in
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`<client/ovpncli.hpp>`_.
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A simple command-line wrapper for the API is provided in
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`<test/ovpncli/cli.cpp>`_.
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Building the OpenVPN 3 client on Linux
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--------------------------------------
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These instructions were tested on Ubuntu 20.
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Prepare directory structure::
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$ sudo apt install g++ make libmbedtls-dev libssl-dev liblz4-dev cmake
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$ export O3=~/O3 && mkdir $O3
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$ export DEP_DIR=$O3/deps && mkdir $DEP_DIR
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$ export DL=$O3/dl && mkdir $DL
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Clone the OpenVPN 3 source repo::
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$ cd $O3
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$ git clone https://github.com/OpenVPN/openvpn3.git core
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Build dependencies::
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$ cd core/scripts/linux/
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$ ./build-all
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Build the OpenVPN 3 client wrapper (cli) with OpenSSL library::
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$ cd $O3/core && mkdir build && cd build
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$ cmake ..
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$ cmake --build .
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To use mbed TLS, use::
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$ cmake -DUSE_MBEDTLS=on ..
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Run OpenVPN 3 client::
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$ sudo test/ovpncli/ovpncli myprofile.ovpn route-nopull
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Options used:
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- :code:`myprofile.ovpn` : OpenVPN config file (must have .ovpn extension)
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- :code:`route-nopull` : if you are connected via ssh, prevent ssh session lockout
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Using cli with ovpn-dco
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"""""""""""""""""""""""
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ovpn-dco is a kernel module which optimises data channel encryption and
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transport, providing better performance. The cli will detect when the
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kernel module is available and enable dco automatically (use --no-dco
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to disable this).
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Download, build and install ovpn-dco::
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$ cd $O3
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$ git clone https://github.com/OpenVPN/ovpn-dco.git
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$ cd ovpn-dco
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$ make && sudo make install
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$ sudo modprobe ovpn-dco
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Install core dependencies::
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$ sudo apt install pkg-config libnl-genl-3-dev
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Build cli with ovpn-dco support::
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$ cd $O3/core/build
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$ cmake -DCLI_OVPNDCO=on .. && make
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$ sudo test/ovpncli/ovpncli [--no-dco] myprofile.ovpn
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Options:
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- :code:`myprofile.ovpn` : OpenVPN config file (must have .ovpn extension)
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- :code:`--no-dco` : disable data channel offload (optional)
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Building the OpenVPN 3 client on macOS
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--------------------------------------
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OpenVPN 3 should be built in a non-root macOS account.
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Make sure that Xcode is installed with optional command-line tools.
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Create the directory ``~/src``::
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$ mkdir -p ~/src
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Clone the OpenVPN 3 repo::
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$ cd ~/src
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$ git clone https://github.com/OpenVPN/openvpn3.git openvpn3
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Install the dependencies:
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Ensure that [homebrew](https://brew.sh/) is set up.
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::
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$ brew install asio cmake jsoncpp lz4 openssl pkg-config xxhash
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Now build the OpenVPN 3 client executable:
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On a ARM64 based Mac::
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$ cd ~/src/
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$ mkdir build-openvpn3
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$ cd build-openvpn3
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$ cmake -DOPENSSL_ROOT_DIR=/opt/homebrew/opt/openssl -DCMAKE_PREFIX_PATH=/opt/homebrew ~/src/openvpn3
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$ cmake --build .
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For a build on a Intel based Mac::
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$ cd ~/src/
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$ mkdir build-openvpn3
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$ cd build-openvpn3
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$ cmake -DOPENSSL_ROOT_DIR=/usr/local/opt/openssl -DCMAKE_PREFIX_PATH=/usr/local/opt ~/src/openvpn3
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$ cmake --build .
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This will build the OpenVPN 3 client library with a small client
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wrapper (``ovpncli``) and the unit tests.
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These build scripts will create binaries with the same architecture as the host it is
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running on. The Mac OS X tuntap driver is not required, as OpenVPN 3 can use the integrated
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utun interface if available.
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To view the client wrapper options::
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$ ./test/ovpncli/ovpncli -h
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To connect::
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$ ./test/ovpncli/ovpncli client.ovpn
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Building the OpenVPN 3 client for Windows
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-----------------------------------------
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.. image:: ../../../actions/workflows/msbuild.yml/badge.svg
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Building with Visual Studio
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"""""""""""""""""""""""""""
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Prerequisites:
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* Visual Studio 2019 or 2022
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* CMake
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* vcpkg
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* git
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::
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> git clone https://github.com/OpenVPN/openvpn3.git core && cd core
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> set VCPKG_ROOT=<path to vcpkg checkout>
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> cmake --preset win-amd64-release
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> cmake --build --preset win-amd64-release --target ovpncli
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Building with MinGW
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"""""""""""""""""""
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This build should work on both Windows and Linux.
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Prerequisites:
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* mingw-w64
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* CMake
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* vcpkg
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* git
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::
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$ git clone https://github.com/OpenVPN/openvpn3.git core && cd core
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$ export VCPKG_ROOT=<path to vcpkg checkout>
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$ cmake --preset mingw-x64-release
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$ cmake --build --preset mingw-x64-release --target ovpncli
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Testing
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-------
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The OpenVPN 3 core includes a stress/performance test of
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the OpenVPN protocol implementation. The test basically
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creates a virtualized lossy network between two OpenVPN
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protocol objects, triggers TLS negotiations between them,
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passes control/data channel messages, and measures the ability
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of the OpenVPN protocol objects to perform and remain in
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a valid state.
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The OpenVPN protocol implementation that is being tested
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is here: `<openvpn/ssl/proto.hpp>`_
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The test code itself is here: `<test/ssl/proto.cpp>`_
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Build the test::
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$ cd $O3
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$ cmake --build . -- test/ssl/proto
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Run the test::
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$ cd test/ssl
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$ time ./proto
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*** app bytes=72777936 net_bytes=122972447 data_bytes=415892854 prog=0000216599/0000216598 D=12700/600/12700/600 N=109/109 SH=17400/15300 HE=0/0
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real 0m15.813s
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user 0m15.800s
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sys 0m0.004s
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The OpenVPN 3 core also includes unit tests, which are based on
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Google Test framework. To run unit tests, you need to install
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CMake and build Google Test.
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Build and run tests on Linux::
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$ cd $O3/core/build
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$ cmake --build . -- test/unittests/coreUnitTests
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$ make test
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Developer Guide
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---------------
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OpenVPN 3 is written in C++17 and developers who are moving
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from C to C++ should take some time to familiarize themselves with
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key C++ design patterns such as *RAII*:
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https://en.wikipedia.org/wiki/Resource_acquisition_is_initialization
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OpenVPN 3 Client Core
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"""""""""""""""""""""
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OpenVPN 3 is designed as a class library, with an API that
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is essentially defined inside of namespace ``ClientAPI``
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with headers and implementation in `<client>`_ and
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header-only library files under `<openvpn>`_.
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The consise definition of the client API is essentially ``class OpenVPNClient``
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in `<client/ovpncli.hpp>`_ with several imporant extensions to
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the API found in:
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* :code:`class TunBuilderBase` in `<openvpn/tun/builder/base.hpp>`_ —
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Provides an abstraction layer defining the *tun* interface,
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and is especially useful for interfacing with an OS-layer VPN API.
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* :code:`class ExternalPKIBase` in `<openvpn/pki/epkibase.hpp>`_ —
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Provides a callback for external private key operations, and
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is useful for interfacing with an OS-layer Keychain such as
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the Keychain on iOS, Mac OS X, and Android, and the Crypto API
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on Windows.
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* :code:`class LogReceiver` in `<client/ovpncli.hpp>`_ —
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Provides an abstraction layer for the delivery of logging messages.
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OpenVPN 3 includes a command-line reference client (``cli``) for
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testing the API. See `<test/ovpncli/cli.cpp>`_.
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The basic approach to building an OpenVPN 3 client is
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to define a client class that derives from
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:code:`ClientAPI::OpenVPNClient`, then provide implementations
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for callbacks including event and logging notifications:
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::
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class Client : public ClientAPI::OpenVPNClient
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{
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public:
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virtual void event(const Event&) override { // events delivered here
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...
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}
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virtual void log(const LogInfo&) override { // logging delivered here
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...
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}
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...
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};
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To start the client, first create a :code:`ClientAPI::ProtoConfig` object
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and initialize it with the OpenVPN config file and other options:
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::
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ClientAPI::ProtoConfig config;
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config.content = <config_file_content_as_multiline_string>;
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...
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Next, create a client object and evaluate the configuration:
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::
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Client client;
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ClientAPI::EvalConfig eval = client.eval_config(config);
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if (eval.error)
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throw ...;
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Finally, in a new worker thread, start the connection:
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::
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ClientAPI::Status connect_status = client.connect();
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Note that :code:`client.connect()` will not return until
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the session has terminated.
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Top Layer
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"""""""""
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The top layer of the OpenVPN 3 client is implemented
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in `<test/ovpncli/cli.cpp>`_ and `<openvpn/client/cliopt.hpp>`_.
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Most of what this code does is marshalling the configuration and
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dispatching the higher-level objects that implement the OpenVPN
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client session.
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Connection
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""""""""""
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:code:`class ClientConnect` in `<openvpn/client/cliconnect.hpp>`_
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implements the top-level connection logic for an OpenVPN client
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connection. It is concerned with starting, stopping, pausing, and resuming
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OpenVPN client connections. It deals with retrying a connection and handles
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the connection timeout. It also deals with connection exceptions and understands
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the difference between an exception that should halt any further reconnection
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attempts (such as ``AUTH_FAILED``), and other exceptions such as network errors
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that would justify a retry.
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Some of the methods in the class
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(such as ``stop``, ``pause``, and ``reconnect``) are often
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called by another thread that is controlling the connection, therefore
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thread-safe methods are provided where the thread-safe function posts a message
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to the actual connection thread.
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In an OpenVPN client connection, the following object stack would be used:
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1. :code:`class ClientConnect` in `<openvpn/client/cliconnect.hpp>`_ —
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The top-layer object in an OpenVPN client connection.
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2. :code:`class ClientProto::Session` in `<openvpn/client/cliproto.hpp>`_ —
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The OpenVPN client protocol object that subinstantiates the transport
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and tun layer objects.
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3. :code:`class ProtoContext` in `<openvpn/ssl/proto.hpp>`_ —
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The core OpenVPN protocol implementation that is common to both
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client and server.
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4. :code:`class ProtoStackBase<Packet>` in `<openvpn/ssl/protostack.hpp>`_ —
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The bottom-layer class that implements
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the basic functionality of tunneling a protocol over a reliable or
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unreliable transport layer, but isn't specific to OpenVPN per-se.
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Transport Layer
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"""""""""""""""
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OpenVPN 3 defines abstract base classes for Transport layer
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implementations in `<openvpn/transport/client/transbase.hpp>`_.
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Currently, transport layer implementations are provided for:
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* **UDP** — `<openvpn/transport/client/udpcli.hpp>`_
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* **TCP** — `<openvpn/transport/client/tcpcli.hpp>`_
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* **HTTP Proxy** — `<openvpn/transport/client/httpcli.hpp>`_
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Tun Layer
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"""""""""
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OpenVPN 3 defines abstract base classes for Tun layer
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implementations in `<openvpn/tun/client/tunbase.hpp>`_.
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There are two possible approaches to define a Tun
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layer implementation:
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1. Use a VPN API-centric model (such as for Android
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or iOS). These models derive from **class TunBuilderBase**
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in `<openvpn/tun/builder/base.hpp>`_
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2. Use an OS-specific model such as:
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* **Linux** — `<openvpn/tun/linux/client/tuncli.hpp>`_
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* **Windows** — `<openvpn/tun/win/client/tuncli.hpp>`_
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* **Mac OS X** — `<openvpn/tun/mac/client/tuncli.hpp>`_
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Protocol Layer
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""""""""""""""
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The OpenVPN protocol is implemented in **class ProtoContext**
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in `<openvpn/ssl/proto.hpp>`_.
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Options Processing
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""""""""""""""""""
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The parsing and query of the OpenVPN config file
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is implemented by :code:`class OptionList` in
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`<openvpn/common/options.hpp>`_.
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Note that OpenVPN 3 always assumes an *inline* style of
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configuration, where all certs, keys, etc. are
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defined inline rather than through an external file
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reference.
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For config files that do use external file references,
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:code:`class ProfileMerge` in `<openvpn/options/merge.hpp>`_
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is provided to merge those external
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file references into an inline form.
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Calling the Client API from other languages
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"""""""""""""""""""""""""""""""""""""""""""
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The OpenVPN 3 client API, as defined by :code:`class OpenVPNClient`
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in `<client/ovpncli.hpp>`_, can be wrapped by the
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Swig_ tool to create bindings for other languages.
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.. _Swig: http://www.swig.org/
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For example, OpenVPN Connect for Android creates a Java
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binding of the API using `<javacli/ovpncli.i>`_.
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Security
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--------
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When developing security software in C++, it's very important to
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take advantage of the language and OpenVPN library code
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to insulate code from the kinds of
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bugs that can introduce security vulnerabilities.
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Here is a brief set of guidelines:
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* When dealing with strings, use a :code:`std::string`
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rather than a :code:`char *`.
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* When dealing with binary data or buffers, always try to use a
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:code:`Buffer`, :code:`ConstBuffer`, :code:`BufferAllocated`, or
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:code:`BufferPtr` object to provide managed access to the buffer, to
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protect against security bugs that arise when using raw buffer pointers.
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See `<openvpn/buffer/buffer.hpp>`_ for the OpenVPN :code:`Buffer` classes.
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* When it's necessary to have a pointer to an object, use
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:code:`std::unique_ptr<>` for non-shared objects and reference-counted
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smart pointers for shared objects. For shared-pointers,
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OpenVPN code should use the smart pointer classes defined
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in `<openvpn/common/rc.hpp>`_. Please see the comments in
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this file for documentation.
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* Never use :code:`malloc` or :code:`free`. When allocating objects,
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use the C++ :code:`new` operator and then immediately construct
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a smart pointer to reference the object:
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::
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std::unique_ptr<MyObject> ptr = new MyObject();
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ptr->method();
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* When interfacing with C functions that deal with
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raw pointers, memory allocation, etc., consider wrapping
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the functionality in C++. For an example, see :code:`enum_dir()`
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in `<openvpn/common/enumdir.hpp>`_,
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a function that returns a list of files in
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a directory (Unix only) via a high-level
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string vector, while internally calling
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the low level libc methods
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:code:`opendir`, :code:`readdir`, and :code:`closedir`.
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Notice how :code:`unique_ptr_del` is used to wrap the
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``DIR`` struct in a smart pointer with a custom
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deletion function.
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* When grabbing random entropy that is to be used
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for cryptographic purposes (i.e. for keys, tokens, etc.),
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always ensure that the RNG is crypto-grade by using
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:code:`class StrongRandomAPI` as the RNG type:
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::
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StrongRandomAPI::Ptr rng;
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void set_rng(StrongRandomAPI::Ptr rng_arg) {
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rng = std::move(rng_arg);
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}
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* Any variable whose value is not expected to change should
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be declared :code:`const`.
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* Don't use non-const global or static variables unless absolutely
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necessary.
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* When formatting strings, don't use :code:`snprintf`. Instead, use
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:code:`std::ostringstream` or build the string using the :code:`+`
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:code:`std::string` operator:
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::
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std::string format_reconnecting(const int n_seconds) {
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return "Reconnecting in " + openvpn::to_string(n_seconds) + " seconds.";
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}
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or:
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::
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std::string format_reconnecting(const int n_seconds) {
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std::ostringstream os;
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os << "Reconnecting in " << n_seconds << " seconds.";
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return os.str();
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}
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* OpenVPN 3 is a "header-only" library, therefore all free functions
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outside of classes should have the :code:`inline` attribute.
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Conventions
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"""""""""""
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* Use the **Asio** library for I/O and timers.
|
|
Don't deal with sockets directly.
|
|
|
|
* Never block. If you need to wait for something, use **Asio** timers
|
|
or sockets.
|
|
|
|
* Use the :code:`OPENVPN_LOG()` macro to log stuff. Don't use :code:`printf`.
|
|
|
|
* Don't call crypto/ssl libraries directly. Instead use the abstraction
|
|
layers (`<openvpn/crypto>`_ and `<openvpn/ssl>`_) that allow OpenVPN
|
|
to link with different crypto/ssl libraries (such as **OpenSSL**
|
|
or **mbed TLS**).
|
|
|
|
* Use :code:`RandomAPI` as a wrapper for random number
|
|
generators (`<openvpn/random/randapi.hpp>`_).
|
|
|
|
* If you need to deal with configuration file options,
|
|
see :code:`class OptionList` in `<openvpn/common/options.hpp>`_.
|
|
|
|
* If you need to deal with time or time durations, use the
|
|
classes under `<openvpn/time>`_.
|
|
|
|
* If you need to deal with IP addresses, see the comprehensive classes
|
|
under `<openvpn/addr>`_.
|
|
|
|
* In general, if you need a general-purpose library class or function,
|
|
look under `<openvpn/common>`_. Chances are good that it's already
|
|
been implemented.
|
|
|
|
* The OpenVPN 3 approach to errors is to count them, rather than
|
|
unconditionally log them. If you need to add a new error
|
|
counter, see `<openvpn/error/error.hpp>`_.
|
|
|
|
* If you need to create a new event type which can be transmitted
|
|
as a notification back to the client API user, see
|
|
`<openvpn/client/clievent.hpp>`_.
|
|
|
|
* Raw pointers or references can be okay when used by an object to
|
|
point back to its parent (or container), if you can guarantee that
|
|
the object will not outlive its parent. Backreferences to a parent
|
|
object is also a common use case for weak pointers.
|
|
|
|
* Use C++ exceptions for error handling and as an alternative
|
|
to :code:`goto`. See OpenVPN's general exception classes
|
|
and macros in `<openvpn/common/exception.hpp>`_.
|
|
|
|
* Use C++ destructors for automatic object cleanup, and so
|
|
that thrown exceptions will not leak objects. Alternatively,
|
|
use :code:`Cleanup` in `<openvpn/common/cleanup.hpp>`_ when
|
|
you need to specify a code block to execute prior to scope
|
|
exit. For example, ensure that the file :code:`pid_fn` is
|
|
deleted before scope exit:
|
|
::
|
|
|
|
auto clean = Cleanup([pid_fn]() {
|
|
if (pid_fn)
|
|
::unlink(pid_fn);
|
|
});
|
|
|
|
* When calling global methods (such as libc :code:`fork`),
|
|
prepend :code:`::` to the symbol name, e.g.:
|
|
::
|
|
|
|
struct dirent *e;
|
|
while ((e = ::readdir(dir.get())) != nullptr) {
|
|
...
|
|
}
|
|
|
|
* Use :code:`nullptr` instead of :code:`NULL`.
|
|
|
|
Threading
|
|
"""""""""
|
|
|
|
The OpenVPN 3 client core is designed to run in a single thread, with
|
|
the UI or controller driving the OpenVPN API running in a different
|
|
thread.
|
|
|
|
It's almost never necessary to create additional threads within
|
|
the OpenVPN 3 client core.
|
|
|
|
|
|
Contributing
|
|
------------
|
|
|
|
See `<CONTRIBUTING.rst>`_.
|
|
|
|
License
|
|
-------
|
|
|
|
See `<LICENSE.rst>`_.
|