A Data-Centric Web Application Security Framework

Jonathan Burket, Patrick Mutchler, Michael Weaver, Muzzammil Zaveri, and David Evans

University of Virginiahttp://guardrails.cs.virginia.edu

GuardRails

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Web applications are easier to create than ever!

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Securing web applications is not nearly as easy!

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“><script>alert(document.cookie);</script>

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Application

Page A

Page B

Page C

Page D

Data Object

WriteAppendRead

WriteRead

Delete

Read

Read

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Application

Page A

Page B

Page C

Page D

Data Object

WriteAppendRead

WriteRead

Delete

Read

Read

Output HTML

Data Object

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Application

Page A

Page B

Page C

Page D

Data Object

WriteAppendRead

WriteRead

Delete

Read

Read

Output HTML

Data Object

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Application

Page A

Page B

Page C

Page D

Data Object

WriteAppendRead

WriteRead

Delete

Read

Read

Proxy that EnforcesSecurity Policies

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Our Philosophy

Security policies should be attached to the data

Security policies should be enforced automatically

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Annotated Ruby on Rails Code

Secure Ruby on Rails Code

GuardRails

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Design GoalsTop Priority:

Automatically enforce security policiesOther Objectives:

Preserve application functionalityEasy for developers to use

Lesser Goals:Minimize performance cost

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Annotated Ruby on Rails Code

Secure Ruby on Rails Code

GuardRails

Access Control PoliciesFine Grained Taint-Tracking

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Annotated Ruby on Rails Code

Secure Ruby on Rails Code

GuardRails

Access Control PoliciesFine Grained Taint-Tracking

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if include_subprojects && !active_children.empty? ids = [id] + active_children.collect {|c| c.id}

conditions = ["#{Project.table_name}.id IN (#{ids.join(',')})"]

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if include_subprojects && !active_children.empty? ids = [id] + active_children.collect {|c| c.id}

conditions = ["#{Project.table_name}.id IN (#{ids.join(',')})"]

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if include_subprojects && !active_children.empty? ids = [id] + active_children.collect {|c| c.id}

conditions = ["#{Project.table_name}.id IN (#{ids.join(',')}) AND #{Project.visible_by}"]

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application_helper.rb

4 Checks

project.rb

2 Checks

projects_controller.rb

3 Checks

acts_as_searchable.rb

1 Checks

# @ :read, :self, lambda{|user|self.is_public or user.memberships.include? self.id}

# @ :read, lambda{|user| self.is_public or user.memberships.include? self.id}

class Project < ActiveRecord::Base# Project statusesSTATUS_ACTIVE = 1…

1 GuardRails Annotation

In Project model file:

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Access Control Policy Annotations

# @ (policy_type, [target], [handler], mediator)

# @ :delete, :self, :admin

# @ :write, :password, lambda{|user|user.id == self.id }

# @ :append, :members, lambda{|user| user.belongs_to?(self)}

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Annotated Ruby on Rails Code

Secure Ruby on Rails Code

GuardRails

Access Control PoliciesFine Grained Taint-Tracking

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Dynamic Taint TrackingProtects against injection attacks

“SELECT profile FROM users WHERE username=‘” + user_name + “’”

“User: <a href=‘profile_page’>” + user_name + “</a>”

Good: user_name = “jazzFan26”

Bad: user_name = “’; DROP TABLE users--”

Good: user_name = “DrKevinPhillips”

Bad: user_name = “<script language=‘javascript’>alert(‘document.cookie’);</script>”

SQL Injection:

Cross-Site Scripting:

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Application

Page A

Page B

Page C

Page D

Data Object

WriteAppendRead

WriteRead

Delete

Read

Read

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Application

Page A

Page B

Page C

Page D

Data Object

WriteAppendRead

WriteRead

Delete

Read

Read

Output HTML

Data Object

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Taint Propagation

ModelController

Database

Data Taint Status

View

URL Parameters

Form Data

Other User Input

Tainted HTML

SanitizationSafe HTML

Expressive Taint Status“<a href=‘profile?id=184392’><evil>SoccerFan1985</evil></a>”

“<a href=“profile?id=184392”><evil>SoccerFan1985</evil></a>”

StringValue:

Taint:

Character Index

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<Transformer::Identity>

<Transformer::Default>

<Transformer::Identity>

DifferentChunks

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Transformers

{:HTML => { “//script” => NoDisplay, :default => NoHTMLAllowed }, :SQL => SQLSanitize, :Ruby_eval => NoDisplay}

The Default Transformer

Use Context

Appropriate Sanitization Routine

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Transformers

Raw String Chunk 1 Transformer 1

Raw String Chunk 2 Transformer 2

Raw String Chunk 3 Transformer 3

Use Context

Sanitized Chunk

Sanitized Chunk

Sanitized Chunk

Sanitized String

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Transformer Annotations

# @ :taint, :username, {:HTML => AlphaNumericOnly}

# @ :taint, :full_name, {:HTML =>

{TitleTag => LettersAndSpacesOnly,:default => NoHTML}}

# @ :taint, :profile, {:HTML =>

{"//script” => Invisible,:default => BoldItalicUnderlineOnly}}

# @ taint, target, transformer

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Test Application Application Type

Image Gallery(680 lines)

E-Commerce(5556 lines)

Project Management(30747 lines)

E-Commerce(11561 lines)

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Performance Notes

Onyx Redmine PaperTracks0

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10.7Original ApplicationAccess Control OnlyTaint Tracking OnlyFull System

Rela

tive

Tran

sacti

on T

ime

(Nor

mal

ized

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Try GuardRails

Alpha Release Now Available!Our Web Page: http://guardrails.cs.virginia.eduFull source code can be downloaded from GitHub

Contact Info: guardrails@cs.virginia.edu

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Questions?

Alpha Release Now Available!Our Web Page: http://guardrails.cs.virginia.eduFull source code can be downloaded from GitHub

Contact Info: guardrails@cs.virginia.edu