Download - Owasp App Sec Ireland Windows Phone 7 Security

David Rook

Windows Phone 7 Security

OWASP AppSec Ireland

Friday, 7 September 2012

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• Application Security Lead, Realex Payments, Dublin CISSP, CISA, GCIH and many other acronyms

• Security Ninja (@securityninja)

• Speaker at developer and security conferences

• Microsoft Developer Security MVP

• SC Magazine Information Security Rising Star 2012

• Developed and released Agnitio and the WPAA


• Smartphones and apps - big numbers, little security?

• Windows Phone 7 introduction

• Windows Phone 7 platform security

• Windows Phone 7 application security

Agenda


Mobile device sales 2011

Mobile69%

Smartphones31%

1.3 billion

472 million

Source: http://www.gartner.com/it/page.jsp?id=1924314Friday, 7 September 2012

http://www.gartner.com/it/page.jsp?id=1924314


Smartphone OS market share 2011

Android51%

iOS24%

Symbian12%

RIM9%

Microsoft2%

Source: http://www.gartner.com/it/page.jsp?id=2120015Friday, 7 September 2012




• Microsoft has 1.9% of the smartphone market share

• Smaller market share than something called Bada





• Similar approach to Android with many devices available • Should I even continue with this talk about Windows Phone 7?





• Similar approach to Android with many devices available • IDC predict that they will have 20% market share by 2015

• Should I even continue with this talk about Windows Phone 7?





• Similar approach to Android with many devices available • IDC predict that it will have 20% market share by 2015

• Should I even continue with this talk about Windows Phone 7?

• 20% is unlikely but it’s market share will increase in my opinion


Windows Phone 7 Introduction

• The smartphone from Microsoft

• First released in late 2010 with 7 updates since then

• Minimum “tough but fair” hardware requirements• Apps only available via the Windows Phone Marketplace• Specifically aimed at the consumer market not enterprise

• Based on Windows Embedded Compact v6 and v7



• .NET Compact Framework

• Version of the .NET framework for resource constrained devices

• Compiler translates your code into Intermediate Language • Apps are JIT compiled and executed by the .NET CLR• Only managed .NET code allowed in your apps*

• Some of the same classes and some mobile specific ones


Windows Phone 7 Introductionprivate void button1_Click(object sender, RoutedEventArgs e) { MessageBox.Show("Hello OWASP AppSec Ireland!"); }

C# Compiler

ManagedModule

.NET CLR



• Windows Phone 7 Kernel Architecture

• 32bit OS that runs inside a 4GB virtual address space

• That isn’t quite true, the process executing only gets 1GB• 1GB is for components commonly mapped into all processes

• 2GB allocated to the kernel and 2GB to process executing



• Windows Phone 7 Kernel Architecture

Hardware

Ker

nel

Spa

ce

Drivers

Device.DLL

kCoreDLL.DLL

COREDLL/WINSOCK/COMMCRL/WININET

NetworkGWESFSDMGR.DLL

FILESYS.DLL

KERNEL.DLL

OAL.EXE

APPLICATIONS

Use

rS

pace

TELSHELL.EXE UDEVICES.EXE SERVICESD.EXE CPROG.EXE


Windows Phone 7 IntroductionK

erne

lS

pace

2GB

Pro

cess

Spa

ce

2GB

Kernel

File System

Drivers

GWES

Memory Mapped Files

User DLLs

Process Code


Windows Phone 7 IntroductionP

roce

ssM

emor

y

2GB Shared User DLLs

512MB

RAM Backed Mapfiles256MB

Shared System Heap256MB

Process Space1GB per process

Priv

ate

toea

ch

proc

ess

Com

mon

ac

ross

all

proc

esse

s


Windows Phone 7 Platform Security

• Windows Phone 7 Security Model

• Chambers concept to enforce app isolation and least privilege

• Four chambers and apps run in one of them• Three chambers have fixed permission sets• The fourth chamber is capabilities based

• The chambers provide a security boundary to restrict the apps



Trusted Computing Base (TCB)

Elevated RightsChamber (ERC)

Standard RightsChamber (SRC)

Least PrivilegedChamber (LPC)

Fixed permissions

Capabilities based



Trusted Computing Base (TCB)

• Allows processes to have unrestricted access to most resources• The TCB chamber can modify policy and enforce the security model• Only Microsoft can add signed software to the TCB chamber

• The kernel and kernel-mode drivers run in the TCB chamber



Elevated RightsChamber (ERC)

• Can access all resources except security policy• Intended for services and user-mode drivers• Only Microsoft can add signed software to the ERC chamber

• User-mode drivers and services runs in this chamber



Standard RightsChamber (SRC)

• Apps that do not provide device-wide services run in the SRC• The default chamber for pre-installed MS and OEM applications



Least PrivilegedChamber (LPC)

• Least Privileged Chambers are configured using capabilities• The default chamber for all non-Microsoft applications

• Capabilities listed in applications WMAppManifest.xml file



• Windows Phone 7 Application Capabilities

• Application capabilities are features that an app uses

• Default app manifest file includes a list of all the capabilities*• WP7 grants security permissions based on the contents of your

WMAppManifest.xml file*• Not everything your app does needs a capability defined

• Apps request permission to access protected APIs during the deployment process



• Windows Phone 7 Application Capabilities

• Capability checks are enforced at runtime

• Requests for other resources == UnauthorizedAccessException• This exception occurs when the access is attempted not when

the app is executed

• Permission set for the apps LPC is created based on the capabilities



• Windows Phone 7 Capabilities Detection Demo



• Windows Phone 7 Application Signing

• Apart from developer unlocked devices apps must be signed• Microsoft automatically signs approved apps• Apps must have a valid Microsoft signature to be installed



• Windows Phone 7 Application Sandboxing

• Apps execute within a restricted LPC as we saw earlier• Cannot communicate with other apps on the phone• Sandboxed apps aren’t allowed to run in the background • No access to native code from within the sandbox• All I/O operations are restricted to per app Isolated Storage



• Windows Phone 7 Application Isolated Storage

• Per app Isolated Storage allows apps to keep data “private”• Very similar to Isolated Storage in Silverlight• No direct access to the file system• No access to other apps Isolated Storage• Three different ways to use your apps Isolated Storage


Windows Phone 7 Application Security

• Windows Phone 7 Application Security

• Mobile application security introduces almost no new issues• Forget about specific vulnerabilities for one minute• Think about the root causes of vulnerabilities, I’ll give you a hand



• Input Validation• Output Validation• Error Handling• Authentication and Authorisation• Secure Storage• Secure Communications• Session Management• Secure Resource Access• Auditing and Logging• Privacy



• Windows Phone 7 Application Security

• Mobile application security introduces almost no new issues• Forget about specific vulnerabilities for one minute• Think about the root causes of vulnerabilities, I’ll give you a hand• From that list what do you think the top 3 are?• My top 3 are:

• Secure Storage• Authentication and Authorisation• Secure Resource Access/Privacy



• OWASP Top 10 Mobile Risks

• I compared the OWASP top 10 mobile risks to my list• 50% Secure Storage/Secure Communications• 20% Authentication and Authorisation• 0% Privacy*



• OWASP Mobile Controls

• Lists the mobile app security controls you should implement • I compared each control to the list I showed you, guess what?• 26% Secure Storage• 16% Secure Communications

• 16% Secure Resource Access*• 16% Authentication and Authorisation



• My top 3 in the real world

• Secure Storage: Facebook, Citibank, LinkedIn, Google Wallet• A&A: Foodspotting, Google Wallet, Google (multiple apps)• SRA/Privacy: Path, Hipster, Ad Libraries• This doesn’t mean we can ignore all of the other issues



• Preventing the top 3 in your WP7 apps

• I can’t cover every principle in this talk• With that in mind I'm grouping them to make a "new" top 3• Data Security - Secure Storage and Communications• Authentication and Authorisation• Data Access/Privacy



• Windows Phone 7 Data Security

• Never store data on the device if it really isn’t needed• WP7 allows us to encrypt data and databases• Only new databases can be encrypted but very easy to do• DPAPI is used for file/password/pin etc encryption• No hashing available and no algorithm selection




• The local database encryption is based on a password• You create a DB in code and you must include the password• The database is encrypted using AES-128• The password is hashed using SHA-256• An encrypted database can be created with two lines of code



// Create the data context, specify the database file location and passwordDavesDataContext db = new DavesDataContext ("Data Source=isostore:/NinjaSecrets.sdf;Password=NinjaPassword");

// Create an encrypted database after confirming that it does not existif (!db.DatabaseExists()) db.CreateDatabase();




• Saving data to an apps isolated storage is not secure• If you want to encrypt data and not a DB you use the DPAPI• Use the System.Security.Cryptography.ProtectedData class• Specifically the Protect() and Unprotect() methods• Symmetric encryption (AES) used. Hashing isn’t possible




• Every app on a WP7 phone gets its own Encryption Key• DPAPI generates and securely stores this for you• Calling Protect() or Unprotect() implicitly selects the apps key• optionalEntropy parameter can be used to provide extra entropy



• Encrypted Data Code Sample




• Secure Communications is a lot easier!• Very little to do with the app code itself in my opinion• More to do with good design and a good security code review!• Data sent to web services, SQL Azure etc needs protection• No client side SSL certs allowed and no VPN functionality



• Windows Phone 7 Authentication & Authorisation

• Not just talking about app logon or service authentication• Specifically talking about access to data on the device• Gaining users authorisation before accessing sensitive data• This includes access to users contacts, SMS etc• I know we already "asked" in the WMAppManifest.xml file....



• Windows Phone 7 Data Access/Privacy

• Another one which isn’t a platform/framework specific• Understand the data accessed by third party libraries• Create a privacy policy covering personal data and stick to it!• Don’t store historical data on the device beyond required time• Audit app communications to check for data leaks



• The good things

• Shared Windows Core (NT Kernel on a phone)• Secure boot and Bitlocker on by default• Enterprise app deployment/management functionality• OTA updates for all phones for at least 18 months



• The potentially bad things

• Shared Windows Core (NT Kernel on a phone)• NFC and Wallet Hub• Native C and C++ code now available to everyone• Micro SD Card support but with no Bitlocker support


Application Security Workshop

• Free Application Security Workshop at Realex

• 27th September in our Dublin office

• Secure coding: why and how

• Think like a pen tester

• Security focused code reviews


www.securityninja.co.uk

@securityninja

QUESTIONS?

/realexninja

/securityninja

/realexninja

http://sourceforge.net/projects/agnitiotool/


http://www.securityninja.co.uk

http://www.securityninja.co.uk

