Policy Based Access Control

This library will be like 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-validator

Contents

• Synopsis
• Constructor
  • Properties
• Methods
  • evaluate(params)
  • validate(policy)
• Reference
  • Context

Statements

import {PBAC, PBACStatement} from "pbac-validator";

const statements: PBACStatement[] = [
  {
    effect: "allow",
    action: ["iam:CreateUser", "iam:UpdateUser", "iam:DeleteUser"],
    resource: ["arn:aws:iam:::user/${req:UserName}"],
  },
];

const pbac = new PBAC(statements);

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

Constructor

const pbac = new PBAC(statements);

Constructs a policy evaluator.

Properties

• statements (Array|Object) Either an array of policy statement. Have a look at https://docs.aws.amazon.com/IAM/latest/UserGuide/AccessPolicyLanguage_ElementDescriptions.html for a description of the policy statement syntax.

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.

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.

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

evaluateMulti(params)

Tests many objects against the policies and determines if the each object passes.

Parameters

• params (Array) Array of policy object

Returns: boolean[]

addFromFunctionMatrix(params)

Add the function matrix and convert thems to policy statements by grouping the action and resource

Parameters

• params (Array) Array of function matric
  • action (String) - Action to validate
  • resource (String) - Resource to validate
  • allow (Boolean) - allow the action on resource

const functions = [
  {
    resource: "employee",
    action: "create",
    allow: true,
  },
  {
    resource: "employee",
    action: "update",
    allow: true,
  },
  {
    resource: "employee",
    action: "list",
    allow: true,
  },
  {
    resource: "employee",
    action: "remove",
    allow: true,
  },
  {
    resource: "employee",
    action: "invite",
    allow: false,
  },
  {
    resource: "org",
    action: "create",
    allow: true,
  },
  {
    resource: "org",
    action: "remove",
    allow: false,
  },
  {
    resource: "workspace",
    action: "create",
    allow: false,
  },
  {
    resource: "workspace",
    action: "remove",
    allow: false,
  },
];

pbac.addFromFunctionMatrix(functions);
console.log(pbac.statements);
/*
It will be
[
  {
    effect: "allow",
    actions: ["*"],
    resources: ["employee"],
  },
  {
    effect: "deny",
    actions: ["invite"],
    resources: ["employee"],
  },
  {
    effect: "deny",
    actions: ["remove"],
    resources: ["org"],
  },
  {
    effect: "allow",
    actions: ["create"],
    resources: ["org"],
  },
  {
    effect: "deny",
    actions: ["*"],
    resources: ["workspace"],
  },
];
*/

Reference

Context

Have a look at https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_condition.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:

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.