Development and Analysis of Security Policies in Security Enhanced Android

121 Pages·2013·1.01 MB·English

NAVAL
POSTGRADUATE

SCHOOL

MONTEREY, CALIFORNIA

THESIS

DEVELOPMENT AND ANALYSIS OF SECURITY
POLICIES IN SECURITY ENHANCED ANDROID

by

Ryan A. Rimando

December 2012

Thesis Advisor: George W. Dinolt
Second Reader: Karen Burke
Approved for public release; distribution is unlimited
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December 2012 Master’s Thesis
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Development and Analysis of Security Policies in Security Enhanced Android
6. AUTHOR(S) Rimando, Ryan
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Monterey, CA 93943–5000
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13. ABSTRACT (maximum 200 words)
This thesis examines Security Enhanced Android. Both its policy and its additional security features are explored. The policy is
examined in depth, providing a better understanding of the security provided by SE Android. We analyze the default SE Android
policy. We identify a potential weakness and change the policy to facilitate control over communication channels. A proof-of-
concept set of applications is developed to demonstrate how SE Android can be used to improve application security. The proof-of-
concept policy is then analyzed to determine if security goals are met.

14. SUBJECT TERMS Android, SE Android, SE Linux, Security Policy 15. NUMBER OF
PAGES
121
16. PRICE CODE
17. SECURITY 18. SECURITY 19. SECURITY 20. LIMITATION OF
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Approved for public release; distribution is unlimited

DEVELOPMENT AND ANALYSIS OF SECURITY POLICIES IN SECURITY
ENHANCED ANDROID

Ryan A. Rimando
Civilian, Federal Cyber Corps
B.S., College of Charleston, 2010

Submitted in partial fulfillment of the
requirements for the degree of

MASTER OF SCIENCE IN COMPUTER SCIENCE

from the

NAVAL POSTGRADUATE SCHOOL
December 2012

Author: Ryan A. Rimando

Approved by: George W. Dinolt
Thesis Advisor

Karen Burke
Second Reader

Peter J. Denning
Chair, Department of Computer Science

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ABSTRACT
This thesis examines Security Enhanced Android. Both its policy and its additional
security features are explored. The policy is examined in depth, providing a better
understanding of the security provided by SE Android. We analyze the default SE
Android policy. We identify a potential weakness and change the policy to facilitate
control over communication channels. A proof-of-concept set of applications is
developed to demonstrate how SE Android can be used to improve application security.
The proof-of-concept policy is then analyzed to determine if security goals are met.

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TABLE OF CONTENTS
I. INTRODUCTION........................................................................................................1
A. DISCUSSION ...................................................................................................1
B. SCOPE ..............................................................................................................1
C. ORGANIZATION OF THESIS .....................................................................2
II. BACKGROUND ..........................................................................................................3
A. INTRODUCTION ............................................................................................3
B. CIA PRINCIPLES ...........................................................................................3
C. ACCESS CONTROL.......................................................................................3
1. Discretionary Access Control..............................................................5
2. Mandatory Access Control ..................................................................5
a. Role-Based Access Control Model ...........................................5
b. Type Enforcement Model..........................................................7
c. Bell-LaPadula Model ................................................................8
3. Capability-based Systems ....................................................................9
D. SECURITY ENHANCED LINUX ...............................................................10
E. ANDROID ......................................................................................................10
F. SE ANDROID.................................................................................................12
G. RELATED WORK ........................................................................................12
III. ANDROID AND ITS SECURITY FEATURES .....................................................15
A. ANDROID FRAMEWORK ..........................................................................15
B. ANDROID SECURITY MODEL .................................................................17
C. ANDROID PERMISSIONS ..........................................................................19
D. APPLICATION COMPONENTS ................................................................21
1. Activities..............................................................................................21
2. Services................................................................................................22
3. Content Providers ..............................................................................22
4. Broadcast Receivers ...........................................................................23
E. INTENTS ........................................................................................................23
F. BINDER ..........................................................................................................25
IV. SE LINUX ...................................................................................................................29
A. INTRODUCTION..........................................................................................29
B. SE LINUX ACCESS CONTROL MODELS ..............................................29
1. Type Enforcement ..............................................................................29
2. Role-based Access Control ................................................................31
3. Multi-Level Security ..........................................................................32
C. SE LINUX POLICIES ...................................................................................32
D. SE LINUX POLICY TOOLS .......................................................................33
V. SE LINUX IN ANDROID (SE ANDROID).............................................................35
A. INTRODUCTION..........................................................................................35
B. FEATURES ....................................................................................................35
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C. REFERENCE POLICY ................................................................................36
1. Domain Rules .....................................................................................36
2. Application Domains .........................................................................37
3. Seapp_contexts ...................................................................................39
4. Install-time MAC ...............................................................................40
5. Important System Applications ........................................................42
a. General System Apps ..............................................................43
b. Init............................................................................................43
c. Zygote ......................................................................................44
d. Service Manager .....................................................................44
e. Media Server ...........................................................................44
f. Installd .....................................................................................45
6. Macros .................................................................................................45
7. MLS .....................................................................................................47
D. SE MANAGER...............................................................................................48
E. SE ANDROID VS EXPLOITS .....................................................................48
1. RageAgainstTheCage ........................................................................48
2. Exploid ................................................................................................49
VI. PROOF OF CONCEPT APPLICATIONS AND POLICY ...................................51
A. SCENARIO INTRODUCTION ...................................................................51
B. ARCHITECTURE OF APPLICATIONS ...................................................51
1. Main Application ...............................................................................51
2. Trusted Controller .............................................................................53
3. Calendar Applications .......................................................................54
C. SECURITY GOALS/REQUIREMENTS ....................................................55
D. ANDROID SECURITY .................................................................................56
1. Deficiencies .........................................................................................56
E. SE LINUX POLICY DEVELOPMENT ......................................................57
1. App.te ..................................................................................................57
2. Seapp_contexts ...................................................................................58
3. Poc_app.te ...........................................................................................59
4. Mac_permissions.xml ........................................................................60
F. SE LINUX POLICY ANALYSIS .................................................................60
1. Apol .....................................................................................................60
2. Qisaq....................................................................................................62
G. DISCUSSION .................................................................................................63
VII. CONCLUSION ..........................................................................................................67
A. FUTURE WORK ...........................................................................................67
B. SUMMARY ....................................................................................................69
APPENDIX A. PROOF OF CONCEPT CODE ........................................................71
A. PACKAGE COM.PROC.DISPLAYAPP ....................................................71
1. MainActivity.java...............................................................................71
2. DisplayActivity.java ...........................................................................72
3. AndroidManifest.xml.........................................................................76
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