npm package: @jdiamond/pbac
Description: AWS IAM Policy inspired and (mostly) compatible evaluation engine
Author: Moritz Onken
Latest version: 1.0.0

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# Policy Based Access Control

**AWS IAM Policy inspired and (mostly) compatible evaluation engine**

Use the power and flexibility of the AWS IAM Policy syntax in your own application to manage access control. For more details on AWS IAM Policies have a look at https://docs.aws.amazon.com/IAM/latest/UserGuide/policies_overview.html.

## Installation

```
npm install pbac
```

<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
Contents

- [Synopsis](#synopsis)
- [Constructor](#constructor)
  - [Properties](#properties)
- [Methods](#methods)
  - [evaluate(params)](#evaluateparams)
  - [validate(policy)](#validatepolicy)
- [Reference](#reference)
  - [Context](#context)

<!-- END doctoc generated TOC please keep comment here to allow auto update -->

## Synopsis

```javascript
var PBAC = require('pbac');

var policies = [{
  "Version": "2012-10-17",
  "Statement": [{
    "Sid": "OptionalDescription",
    "Effect": "Allow",
    "Action": [
      "iam:CreateUser",
      "iam:UpdateUser",
      "iam:DeleteUser"
    ],
    "Resource": [
      "arn:aws:iam:::user/${req:UserName}"
    ],
    "Condition": {
      "IpAddress": {
        "req:IpAddress": "10.0.20.0/24"
      }
    }
  }]
}];

var pbac = new PBAC(policies);

// returns true
pbac.evaluate({
  action: 'iam:CreateUser',
  resource: 'arn:aws:iam:::user/testuser',
  context: {
    req: {
      IpAddress: '10.0.20.51',
      UserName: 'testuser',
    }
  }
});
```

## Constructor

```javascript
var pbac = new PBAC(policies, [options]);
```

Constructs a policy evaluator.

### Properties


* **`policies`** (Array|Object)
  Either an array of policies or a single policy document. Have a look at https://docs.aws.amazon.com/IAM/latest/UserGuide/AccessPolicyLanguage_ElementDescriptions.html for a description of the policy syntax.
* **`options`** (Object)
    * `schema` (Object) - JSON schema that describes the policies. Defaults to the contents of schema.json that ships with this module.
    * `validateSchema` (Boolean) - Validate the schema when the object is constructed. This can be disabled in production environment if it can be assumed that the schema is valid to improve performance when constructing new objects.
    * `validatePolicies` (Boolean) - Policies passed to the constructor will be validated against the `schema`. Defaults to `true`. Can be disabled to improve performance if the policies can be assumed to be valid.
    * `conditions` (Object) - Object of conditions that are supported in the `Conditions` attribute of policies. Defaults to `conditions.js` in this module. If conditions are passed to the constructor they will be merged with the conditions of the `conditions.js` module (with `conditions.js` taking precedence).


## Methods


### evaluate(params)

Tests an object against the policies and determines if the object passes.
The method will first try to find a policy with an explicit `Deny` for the combination of
`resource`, `action` and `condition` (matching policy). If such policy exists, `evaluate` returns false.
If there is no explicit deny the method will look for a matching policy with an explicit `Allow`.
`evaluate` will return `true` if such a policy is found. If no matching can be found at all,
`evaluate` will return `false`. Please find a more thorough explanation of this process at https://docs.aws.amazon.com/IAM/latest/UserGuide/AccessPolicyLanguage_EvaluationLogic.html.

```javascript
pbac.evaluate({
  action: 'iam:CreateUser',
  resource: 'arn:aws:iam:::user/testuser',
  context: {
    req: {
      IpAddress: '10.0.20.51',
      UserName: 'testuser',
    }
  }
});
```

**Parameters**

* **`params`** (Object)
    * `action` (String) - Action to validate
    * `resource` (String) - Resource to validate
    * `context` (Object) - Nested object of context for interpolation of policy context. See [Context](#context).

**Returns**: `boolean`, Returns `true` if `params` passes the policies, `false` otherwise

### validate(policy)

Validates one or many policies against the schema provided in the constructor.
Will throw an error if validation fails.

**Parameters**

* **`policy`** (Array|Object)
  Array of policies or a single policy object

**Returns**: `boolean`, Returns `true` if the policies are valid


## Reference

### Context

Have a look at https://docs.aws.amazon.com/IAM/latest/UserGuide/Policycontext.html to understand what policy context are, where they can be used and how they are interpreted. The `evaluate` method expects a `context` parameter which is a nested object that translates to colon-separated context.

**Example:**

```javascript
var context = {
    req: {
      IpAddress: '10.0.20.51',
      UserName: 'testuser',
    },
    session: {
      LoggedInDate: '2015-09-29T15:12:42Z',
  },
};
```

This would translate to the context `req:IpAddress`, `req:UserName` and `session:LoggedInDate`.


* * *
The MIT License (MIT)

Copyright (c) 2018 Moritz Onken

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.