Vinyl

Access Level for him and her

by: Federico Saravia Barrantes @fsaravia and Lautaro Orazi @tarolandia

"Vinyl" is a simple gem that allows developers to define different access levels for a resource and a series of local and global validators to gain access to those levels. It works by analyzing a series of validators defined by you and returning a number representing the access level a particular request is able to reach.

This gem is useful when you need to control the output of a process depending on who wants to access to a resource.

For example: user A wants to get user B's profile.

1. If A == B, then A has full access to data
2. If A is friend of B, than A can see private data but not config data
3. If A is not friend of B, then A only can see public data

In this example we have 3 different levels of access to B's information.

  gem install vinyl

  require 'vinyl'

  Vinyl.configure do |config|
    config.api_acl_mode = Vinyl::Configuration::STRATEGY_DESCENDING
    config.force_access_control = true 
    config.warn_on_missing_validators = true 
  end

:api_acl_mode can take two values:

1. Vinyl::Configuration::STRATEGY_DESCENDING, Check for validators starting on the highest access level
2. Vinyl::Configuration::STRATEGY_ASCENDING, Check for validators starting on the lowest access level

:force_access_control true/false

Deny access if no validators are given for a route/method combination and no global validators exist

:warn_on_missing_validators true/false

Display a warning on STDOUT when calling a non-existent validator (Missing validators output always default to false)

A rule defines the access level and the validators for a route/method combination:

Vinyl.when_route 
  '/api/route', 
  :with_method => 'POST|GET|PUT|DELETE',
  :get_access_level => 1...n,
  :if_pass => ['validator1', 'validator2', …, 'validatorn']

Example:

Vinyl.when_route '/profiles.json', 
  :with_method => 'GET', 
  :get_access_level => 1, 
  :if_pass => ['is_user']

Vinyl.when_route '/profiles.json', 
  :with_method => 'GET', 
  :get_access_level => 2, 
  :if_pass => ['is_admin']

You can define your routes using a string, they may include wildcards or you can also use regular expressions:

Example:

Vinyl.when_route '/profiles*', 
  :with_method => 'GET', 
  :get_access_level => 1, 
  :if_pass => ['is_user']

Vinyl.when_route /^\/profiles\/(\d+)\.(.+)/, 
  :with_method => 'GET', 
  :get_access_level => 1, 
  :if_pass => ['is_user']

There are two kinds of validators: global and normal validators. All validators you define must return true or false.

Global validators will be applied to every rule. You can add a global validator using add_global_validator method:

Vinyl.add_global_validator("name_of_global_validator", lambda {
  # your code here
  return true/false
})

Normal validators will be applied when a rule includes it into its validators list. Validators can be added using add_validator method:

Vinyl.add_validator("name_of_validator", lambda {
  # your code here
  return true/false
})

Inside validators you can use your models, classes and whatever. If you want a custom variable to be available in the scope of the validators, add it this way:

Vinyl.my_variable = variable_value

Inside your validator:

Vinyl.add_validator("my_validator", lambda {
  puts my_variable # will output variable_value
  return true/false
})

Clearing Variables

If you need to reset previously defined variables to avoid validation errors just call:

Vinyl.reset_variables

At this point you had defined your rules, validators and variables. Now you are ready to check for the access level.

access_level = Vinyl.check_level('/call/route','call_method')

If you need to avoid a global validator you can use bypass method:

access_level = Vinyl.bypass("global_validator_name").check_level('/call/route','call_method')

or a list of them

access_level = Vinyl.bypass(["global_1","global_2"]).check_level('/call/route','call_method')

Using bypass means exclude the validators only for the current check.

See the UNLICENSE file included with this gem distribution.