crystal-argon2

# crystal-argon2

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This Crystal shard provides C bindings, and a simplified interface, to the Argon2 algorithm. [Argon2](https://github.com/P-H-C/phc-winner-argon2) is the official winner of the Password Hashing Competition, a several year project to identify a successor to bcrypt/PBKDF/scrypt methods of securely storing passwords. This is an independent project and not official from the PHC team.

This project is mostly a clone of this awesome ruby project [technion/ruby-argon2](https://github.com/technion/ruby-argon2)

## Installation

1. Add the dependency to your `shard.yml`:
```yaml
dependencies:
  crystal-argon2:
    github: sushichain/crystal-argon2
```
2. Run `shards install`

## Design

This project has several key tenants to its design:

* The reference Argon2 implementation is to be used "unaltered". To ensure compliance with this goal, and encourage regular updates from upstream, the upstream library is implemented as a git submodule, and is intended to stay that way.
* Security and maintainability take top priority. This can have an impact on platform support. A PR that contains platform specific code paths is unlikely to be accepted.
* Tested versions are Crystal 0.27.0 on MacOS and Linux. No assertions are made on other platforms.
* Errors from the C interface are raised as Exceptions. There are a lot of exception classes, but they tend to relate to things like very broken input, and code bugs. Calls to this library should generally not require a rescue.
* Test suite should aim for 100% code coverage.
* Default work values should not be considered constants. They may change.
* Not exposing the threads parameter is a design choice. I believe there is significant risk, and minimal gain in using a value other than '1'. Four threads on a four core box completely ties up the entire server to process one user logon. If you want more security, increase m_cost.

## Usage

```crystal
require "crystal-argon2"
```

To generate a hash using specific time and memory cost:

```crystal
hasher = Argon2::Password.new(t_cost: 2, m_cost: 16)
hasher.create("password")
    => "$argon2i$v=19$m=65536,t=2,p=1$jL7lLEAjDN+pY2cG1N8D2g$iwj1ueduCvm6B9YVjBSnAHu+6mKzqGmDW745ALR38Uo"
```

To utilise default costs:

```crystal
hasher = Argon2::Password.new
hasher.create("password")
```

If you follow this pattern, it is important to create a new `Argon2::Password` every time you generate a hash, in order to ensure a unique salt. See [issue 23](https://github.com/technion/ruby-argon2/issues/23) for more information.
Alternatively, use this shotcut:

```crystal
Argon2::Password.create("password")
    => "$argon2i$v=19$m=65536,t=2,p=1$61qkSyYNbUgf3kZH3GtHRw$4CQff9AZ0lWd7uF24RKMzqEiGpzhte1Hp8SO7X8bAew"
```

You can then use this function to verify a password against a given hash. Will return either `Argon2::Response::ARGON2_OK` for success or raise and exception with then appropriate error code e.g. `ARGON2_VERIFY_MISMATCH`.

```crystal
Argon2::Password.verify_password("password", secure_password)
```

## Development

* build the C library `cd ext && make`
* run specs: `crystal spec`

## Using crystal_lib

To generate the initial crystal bindings using this library:

* git clone https://github.com/crystal-lang/crystal_lib.git
* download the argon2 code from here [https://github.com/P-H-C/phc-winner-argon2/releases](https://github.com/P-H-C/phc-winner-argon2/releases)
* use `make` to build the argon2 code
* create a crystal bindings file for argon2 that will be run from crystal_lib (see below)
* export LLVM_CONFIG=/usr/local/opt/llvm/bin/llvm-config (use the correct path for your LLVM install)
* crystal run src/main.cr -- path/to/argon2_bindings.cr

#### argon2_bindings.cr example

```crystal
# export LLVM_CONFIG=/usr/local/opt/llvm/bin/llvm-config
@[Include("../phc-winner-argon2/include/argon2.h")]
@[Link("argon2")]
lib LibArgon2
  fun argon2i_hash_raw
  fun argon2i_hash_encoded
  fun argon2d_hash_raw
  fun argon2d_hash_encoded
  fun argon2id_hash_raw
  fun argon2id_hash_encoded

  fun argon2i_verify
  fun argon2d_verify
  fun argon2id_verify
end
```

## Contributing

1. Fork it (<https://github.com/sushichain/crystal-argon2/fork>)
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request

## Contributors

- [Kingsley Hendrickse](https://github.com/kingsleyh) - creator and maintainer