Name
====

lua-resty-hmac - HMAC functions for ngx_lua and LuaJIT

Table of Contents
=================

* [Name](#name)
* [Status](#status)
* [Description](#description)
* [Synopsis](#synopsis)
* [Methods](#methods)
    * [new](#new)
    * [update](#update)
    * [final](#final)
    * [reset](#reset)
* [Prerequisites](#prerequisites)
* [Installation](#installation)
* [Copyright and License](#copyright-and-license)
* [See Also](#see-also)

Status
======

This library is still under active development and is considered production ready.

Description
===========

This library requires an nginx build with OpenSSL,
the [ngx_lua module](http://wiki.nginx.org/HttpLuaModule), and [LuaJIT 2.0](http://luajit.org/luajit.html).

Synopsis
========

```lua
    # nginx.conf:

    lua_package_path "/path/to/lua-resty-hmac/lib/?.lua;;";

    server {
        location = /test {
            content_by_lua_file conf/test.lua;
        }
    }

    -- conf/test.lua:

    local hmac = require "resty.hmac"

    local hmac_sha1 = hmac:new("secret_key", hmac.ALGOS.SHA1)
    if not hmac_sha1 then
        ngx.say("failed to create the hmac_sha1 object")
        return
    end

    local ok = hmac_sha1:update("he")
    if not ok then
        ngx.say("failed to add data")
        return
    end

    ok = hmac_sha1:update("llo")
    if not ok then
        ngx.say("failed to add data")
        return
    end

    local mac = hmac_sha1:final()  -- binary mac

    local str = require "resty.string"
    ngx.say("hmac_sha1: ", str.to_hex(mac))
        -- output: "hmac_sha1: aee4b890b574ea8fa4f6a66aed96c3e590e5925a"

    -- dont forget to reset after final!
    if not hmac_sha1:reset() then
        ngx.say("failed to reset hmac_sha1")
        return
    end

    -- short version
    ngx.say("hmac_sha1: ", hmac_sha1:final("world", true))
        -- output: "hmac_sha1: 4e9538f1efbe565c522acfb72fce6092ea6b15e0"
```

[Back to TOC](#table-of-contents)

Methods
=======

To load this library,

1. you need to specify this library's path in ngx_lua's [lua_package_path](https://github.com/openresty/lua-nginx-module#lua_package_path) directive. For example, `lua_package_path "/path/to/lua-resty-hmac/lib/?.lua;;";`.
2. you use `require` to load the library into a local Lua variable:

```lua
    local hmac = require "resty.hmac"
```

[Back to TOC](#table-of-contents)

new
---
`syntax: local hmac_sha256 = hmac:new(key [, hash_algorithm])`

Creates a new hmac instance. If failed, returns `nil`.

The `key` argument specifies the key to use when calculating the message authentication code (MAC).
`key` is a lua string which may contain printable characters or binary data.

The `hash_algorithm` argument specifies which hashing algorithm to use (`hmac.ALGOS.MD5`, `hmac.ALGOS.SHA1`, `hmac.ALGOS.SHA256`, `hmac.ALGOS.SHA512`).
The default value is `hmac.ALGOS.MD5`.

[Back to TOC](#table-of-contents)

update
---
`syntax: hmac_sha256:update(data)`

Updates the MAC calculation to include new data. If failed, returns `false`.

The `data` argument specifies the additional data to include in the MAC.
`data` is a lua string which may contain printable characters or binary data.

[Back to TOC](#table-of-contents)

final
---
`syntax: local mac = hmac_sha256:final([data, output_hex])`

Finalizes the MAC calculation and returns the final MAC value. If failed, returns `nil`.
When `output_hex` is not `true` returns a lua string containing the raw, binary MAC. When `output_hex` is `true` returns a lua string containing the hexadecimal representation of the MAC.

The `data` argument specifies the additional data to include in the MAC before finalizing the calculation.
The default value is `nil`.

The `output_hex` argument specifies wether the MAC should be returned as hex or binary. If `true` the MAC will be returned as hex.
The default value is `false`.

[Back to TOC](#table-of-contents)

reset
------
`syntax: hmac_sha256:reset()`

Resets the internal hmac context so it can be re-used to calculate a new MAC. If failed, returns `false`.
If successful, the `key` and `hash_algorithm` remain the same but all other information is cleared.

This MUST be called after `hmac_sha256:final()` in order to calculate a new MAC using the same hmac instance.

[Back to TOC](#table-of-contents)

Prerequisites
=============

* [LuaJIT](http://luajit.org) 2.0+
* [ngx_lua module](http://wiki.nginx.org/HttpLuaModule)
* [lua-resty-string](https://github.com/openresty/lua-resty-string) 0.8+
* [OpenSSL](https://www.openssl.org/) 1.0.0+

[Back to TOC](#table-of-contents)

Installation
============

It is recommended to use the latest [ngx_openresty bundle](http://openresty.org) directly. You'll need to enable LuaJIT when building your ngx_openresty
bundle by passing the `--with-luajit` option to its `./configure` script.

Also, You need to configure
the [lua_package_path](https://github.com/openresty/lua-nginx-module#lua_package_path) directive to
add the path of your lua-resty-hmac source tree to ngx_lua's Lua module search path, as in

```nginx
    # nginx.conf
    http {
        lua_package_path "/path/to/lua-resty-hmac/lib/?.lua;;";
        ...
    }
```

and then load the library in Lua:

```lua
    local hmac = require "resty.hmac"
```

[Back to TOC](#table-of-contents)

Copyright and License
=====================

This module is licensed under the BSD license.

Copyright (C) 2012-2023, Thought Foundry Inc.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

[Back to TOC](#table-of-contents)

See Also
========
* the ngx_lua module: http://wiki.nginx.org/HttpLuaModule

[Back to TOC](#table-of-contents)

