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895a6af122
We now depend on libsodium unconditionally. Future work will require functions from libsodium, and nobody we're aware of uses the nacl build for anything other than making sure it still works on CI.
175 lines
6.9 KiB
Markdown
175 lines
6.9 KiB
Markdown
# 
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**Current Coverage:** [](https://codecov.io/gh/TokTok/c-toxcore)
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[**Website**](https://tox.chat) **|** [**Wiki**](https://wiki.tox.chat/) **|** [**Blog**](https://blog.tox.chat/) **|** [**FAQ**](https://wiki.tox.chat/doku.php?id=users:faq) **|** [**Binaries/Downloads**](https://tox.chat/download.html) **|** [**Clients**](https://wiki.tox.chat/doku.php?id=clients) **|** [**Compiling**](/INSTALL.md)
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## What is Tox
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Tox is a peer to peer (serverless) instant messenger aimed at making security
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and privacy easy to obtain for regular users. It uses
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[libsodium](https://doc.libsodium.org/) (based on
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[NaCl](https://nacl.cr.yp.to/)) for its encryption and authentication.
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## IMPORTANT!
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### 
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This is an **experimental** cryptographic network library. It has not been
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formally audited by an independent third party that specializes in
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cryptography or cryptanalysis. **Use this library at your own risk.**
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The underlying crypto library [libsodium](https://doc.libsodium.org/) provides
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reliable encryption, but the security model has not yet been fully specified.
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See [issue 210](https://github.com/TokTok/c-toxcore/issues/210) for a
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discussion on developing a threat model. See other issues for known weaknesses
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(e.g. [issue 426](https://github.com/TokTok/c-toxcore/issues/426) describes
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what can happen if your secret key is stolen).
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## Toxcore Development Roadmap
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The roadmap and changelog are generated from GitHub issues. You may view them
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on the website, where they are updated at least once every 24 hours:
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- Changelog: https://toktok.ltd/changelog/c-toxcore
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- Roadmap: https://toktok.ltd/roadmap/c-toxcore
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## Installing toxcore
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Detailed installation instructions can be found in [INSTALL.md](INSTALL.md).
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Be advised that due to the addition of `cmp` as a submodule, you now also need to initialize the git submodules required by toxcore. This can be done by cloning the repo with the following command: `git clone --recurse-submodules https://github.com/Toktok/c-toxcore` or by running `git submodule update --init` in the root directory of the repo.
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In a nutshell, if you have [libsodium](https://github.com/jedisct1/libsodium)
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installed, run:
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```sh
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mkdir _build && cd _build
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cmake ..
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make
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sudo make install
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```
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If you have [libvpx](https://github.com/webmproject/libvpx) and
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[opus](https://github.com/xiph/opus) installed, the above will also build the
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A/V library for multimedia chats.
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## Using toxcore
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The simplest "hello world" example could be an echo bot. Here we will walk
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through the implementation of a simple bot.
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### Creating the tox instance
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All toxcore API functions work with error parameters. They are enums with one
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`OK` value and several error codes that describe the different situations in
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which the function might fail.
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```c
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TOX_ERR_NEW err_new;
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Tox *tox = tox_new(NULL, &err_new);
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if (err_new != TOX_ERR_NEW_OK) {
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fprintf(stderr, "tox_new failed with error code %d\n", err_new);
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exit(1);
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}
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```
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Here, we simply exit the program, but in a real client you will probably want
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to do some error handling and proper error reporting to the user. The `NULL`
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argument given to the first parameter of `tox_new` is the `Tox_Options`. It
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contains various write-once network settings and allows you to load a
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previously serialised instance. See [toxcore/tox.h](tox.h) for details.
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### Setting up callbacks
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Toxcore works with callbacks that you can register to listen for certain
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events. Examples of such events are "friend request received" or "friend sent
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a message". Search the API for `tox_callback_*` to find all of them.
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Here, we will set up callbacks for receiving friend requests and receiving
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messages. We will always accept any friend request (because we're a bot), and
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when we receive a message, we send it back to the sender.
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```c
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tox_callback_friend_request(tox, handle_friend_request);
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tox_callback_friend_message(tox, handle_friend_message);
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```
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These two function calls set up the callbacks. Now we also need to implement
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these "handle" functions.
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### Handle friend requests
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```c
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static void handle_friend_request(
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Tox *tox, const uint8_t *public_key, const uint8_t *message, size_t length,
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void *user_data) {
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// Accept the friend request:
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TOX_ERR_FRIEND_ADD err_friend_add;
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tox_friend_add_norequest(tox, public_key, &err_friend_add);
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if (err_friend_add != TOX_ERR_FRIEND_ADD_OK) {
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fprintf(stderr, "unable to add friend: %d\n", err_friend_add);
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}
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}
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```
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The `tox_friend_add_norequest` function adds the friend without sending them a
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friend request. Since we already got a friend request, this is the right thing
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to do. If you wanted to send a friend request yourself, you would use
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`tox_friend_add`, which has an extra parameter for the message.
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### Handle messages
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Now, when the friend sends us a message, we want to respond to them by sending
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them the same message back. This will be our "echo".
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```c
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static void handle_friend_message(
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Tox *tox, uint32_t friend_number, TOX_MESSAGE_TYPE type,
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const uint8_t *message, size_t length,
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void *user_data) {
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TOX_ERR_FRIEND_SEND_MESSAGE err_send;
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tox_friend_send_message(tox, friend_number, type, message, length,
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&err_send);
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if (err_send != TOX_ERR_FRIEND_SEND_MESSAGE_OK) {
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fprintf(stderr, "unable to send message back to friend %d: %d\n",
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friend_number, err_send);
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}
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}
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```
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That's it for the setup. Now we want to actually run the bot.
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### Main event loop
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Toxcore works with a main event loop function `tox_iterate` that you need to
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call at a certain frequency dictated by `tox_iteration_interval`. This is a
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polling function that receives new network messages and processes them.
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```c
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while (true) {
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usleep(1000 * tox_iteration_interval(tox));
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tox_iterate(tox, NULL);
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}
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```
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That's it! Now you have a working echo bot. The only problem is that since Tox
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works with public keys, and you can't really guess your bot's public key, you
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can't add it as a friend in your client. For this, we need to call another API
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function: `tox_self_get_address(tox, address)`. This will fill the 38 byte
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friend address into the `address` buffer. You can then display that binary
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string as hex and input it into your client. Writing a `bin2hex` function is
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left as exercise for the reader.
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We glossed over a lot of details, such as the user data which we passed to
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`tox_iterate` (passing `NULL`), bootstrapping into an actual network (this bot
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will work in the LAN, but not on an internet server) and the fact that we now
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have no clean way of stopping the bot (`while (true)`). If you want to write a
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real bot, you will probably want to read up on all the API functions. Consult
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the API documentation in [toxcore/tox.h](toxcore/tox.h) for more information.
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### Other resources
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- [Another echo bot](https://wiki.tox.chat/developers/client_examples/echo_bot)
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- [minitox](https://github.com/hqwrong/minitox) (A minimal tox client)
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