# Safe-ish

NOT FOR PRODUCTION USE

Safe-ish is an _experimental_, minimally restrictive sandbox for BEAM modules 
that examines and rejects BEAM bytecode at load time containing instructions 
that could cause side effects such as:

- Spawning processes
- Sending and receiving messages
- File system access
- Network access
- Compilation
- System level introspection and diagnostics
- Creating atoms dynamically at runtime (which would allow calls to non-whitelisted modules)

You can provide an optional whitelist of modules, functions and language features that the 
loaded module is allowed to use.

## Use
You can call:

- `Safeish.check(bytecode)` to check binary bytecode `bytecode` without loading the module
- `Safeish.load_bytecode(bytecode)` to check `bytecode` and then load the module if it is ok
- `Safeish.load_file(path)` to read the bytecode from the beam file at `path`, check and load it if it is ok

All the above functions take a second optional whitelist argument of calls and language features to allow.
The following list entries are allowed:

- `Module` to allow calls to any function in Elixir module `Module`
- `{Module, function}` to allow calls to an Elixir function with any arity
- `{Module, function, arity}` to allow calls to an Elixir function with a specific arity
- `:module` to allow calls to any function in Erlang module `:module`
- `{:module, function}` to allow calls to an Erlang function with any arity
- `{:module, function, arity}` to allow calls to an Erlang function with a specific arity
- `:send` to allow sending of messages
- `:receive` to allow receipt of messages

The return value for all functions is either `{:ok, Module}` or `{:error, ["reason 1", "reason 2", ...]}`

## Example

```
> Safeish.load_file("CallFileRead.beam")
{:error, CallFileRead, ["Elixir.File.read/1 not whitelisted"]}
> Safeish.load_file("CallFileRead.beam", [{File, read, 1}])
{:ok, CallFileRead}
> CallFileRead.somefunc()
```

## Installation

If [available in Hex](https://hex.pm/docs/publish), the package can be installed
by adding `safeish` to your list of dependencies in `mix.exs`:

```elixir
def deps do
  [
    {:safeish, "~> 0.1.0"}
  ]
end
```

Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
be found at [https://hexdocs.pm/safeish](https://hexdocs.pm/safeish).