kevin stadmeyer garrett held copyright trustwave 2011 confidential hacking (and defending) iphone...

Kevin StadmeyerGarrett Held

COPYRIGHT TRUSTWAVE 2011 CONFIDENTIAL

Hacking (and Defending) iPhone Applications

Garrett Held and Kevin Stadmeyer

› Managing Consultants with Trustwave SpiderLabs› Have performed hundreds of application tests from mainframe to web to mobile

Who Are We?

› The Basics› Setup For Testing› Secure Storage of Data And Credentials› Inadvertent Local Storage and Caching› Client Side Sanitization› Secure Coding› Push Notifications› Secure Communications

Agenda

What we’ll cover – secure coding and beyond, what to look for when assessing an iPhone application

The Basics

Why are people attacking mobile apps?

› Stealing Money› Embarrassing People (“Hactivists”)› Get Famous

Just the Facts, Ma’am

iPhone Apps in the Press

How are people attacking mobile apps?

› New and unsafe operating systems?› Terrible developers who don’t care?› Clueless users who don’t know they should care?

What Security Model We’re Not Talking About?

› Layer 1: Apple Store› Layer 2: Sandboxing via “Seatbelt”

Setting Up The Testing Environment

Don’t you mean setting up the decompiler?

› No

Setting Up The Testing Environment

On das metal – Step 1: get your proxy right

We Built This City

On das metal – Step 2: Get ya certs heard!

We Built This City

On das metal – Step 3: Roll It Up

We Built This City

On das metal – Step 4: Mail it!

We Built This City

On das metal – Step 5: Install It

We Built This City

On das metal – Step 6: Install It (Errrr….)

We Built This City

On das metal – Step 7: Proxy It!

We Built This City

On das metal – Step 8: Victory!

We Built This City

On The Computer Machine – Step 6: Install It!

We Built This City

On The Computer Machine – Step 7: Install It!

We Built This City

On The Computer Machine

We Built This City

› The format is X’<SHA1 Fingerprint>’

Now What?

We Built This City

Now What?

We Built This City

Now What?

We Built This City

Secure Storage Of Data

The Keychain

› Indefinite Storage› Can you store credentials securely without the keychain?– Don’t let the feature make you lazy– Don’t store credentials in the keychain unless you don’t

care about certain things

Storing Credentials

Keychain Compromise via Jailbreaking

› Through a series of steps, retrieves passwords stored in the keychain [1]

› Researchers compromised keychain passwords only, not other protected classes such as passwords for websites– Jailbreak stolen iPhone (requires physical access), gain

SSH access– Copy scripts that will compromise the keychain– Scripts output the victims passwords

Storing Credentials

[1] http://www.sit.fraunhofer.de/en/Images/sc_iPhone%20Passwords_tcm502-80443.pdf

Where Should You Store Them?

› Not on the device?– At least not in plaintext!

Storing Credentials

Securely Storing Data At Rest – things to look for

› Database calls?– Injection Possible?

› Using Core Data?– Does the application trust the integrity of the data?– Remember trust boundaries!

Storing Credentials

Recommendations for non-credential data

› Do not store data on the phone if at all possible– Never has it been so easy to lose so much data so fast!

› Require user to enter a passcode– Can still be brute-forced with time once the encrypted

text is found– Poor user-experience on mobile devices

Storing Credentials

Recommendations for non-credential data

› Store decryption key on a server and require credentials (non-stored) to access key– Only works for applications that do not require offline

access– Increases data usage– Revocable though– Data not “stored” in the cloud

Storing Credentials

B-b-b-but kSecAttrAccessibleWhenUnlocked!

› By default iOS writes information to the keychain with this attribute

› By default most user’s passwords suck

Storing Credentials

Look Familiar?

Storing Credentials

Most Users

Storing Credentials

Pick Simple PINS10,000 possibilities~.1 second to crack (100k a second is pretty standard)

Protect Stupid Users

Storing Credentials

Require Strong Passwords (8+ alpha-numeric chars)

Use REAL and GOOD encryption Don’t rely on an inherently

insecure PIN to protect users. If they knew what they were

doing we wouldn’t be here today.

Inadvertent Local Storage and Caching

Screenshots

› Where are they stored?› When are they taken?› Who can access them!

I Accidently Your Data…

Screenshots

Screenshot Protection

Other Storage Of Information

› Autocomplete, etc.

Autocomplete

› Override autocomplete› textfield.autocorrectionType = UITextAutocorrectionNone

Client Side Sanitization

It’s bad…

› Less burden on server› Critical bypasses (yay!)

Client Side? More like Bad side, amirite?

It’s bad…

› Some classic Web Application faults translate well into the iPhone.

› Web developers relied on:– JavaScript controls– Hidden fields– JSON responses– Information stored in Flash objects

Rogue Clients

› Attackers can write apps (Some testers, too)› Client side secrets can be decompiled– We don’t care if it’s obfuscated for now, that’s a

point in time.

› Distributed through trusted App store?– Already happened to Android

How To Do It Right

› Server Side Controls› Assume everything coming in came from a rouge or compromised client

› Enforce secure communications

What Applies in the iOS world?

Applies Does Not ApplySQL Injection CSRF*XML Injection XSS*Other InjectionPrivilege EscalationSession HijackingOverflows (Buffer, Integer)Format String Problems Insecure use of SSL

CSRF and XSS In Apps?

› Calls to browser– Recent Android Issue [1]– Loads javascript:alert(document.cookie)

› Embedded browser shares web app issues

› Rogue applications and rogue users

]1] http://www.crn.com.au/News/265931,video-details-android-browser-intercept-flaw.aspx

Break That Down Into Attackers View

Attacker Targets Server Attacker Targets DeviceSQL Injection Overflows (Buffer, Integer)XML Injection Format String Problems Other InjectionPrivilege EscalationSession HijackingInsecure use of SSL

What Does This Mean to a Developer?

› Time to throw out any assumptions that the device will protect you by obfuscating anything

› A new set of security practices need to be developed and followed when creating App’s

Shifting Paradigms – we hate ourselves

› Local Storage Review– What is stored and why?

› Educating QA– Proxy testing

› Review Local and Remote Inputs› Information Leakage

Local Storage Review

› Review what’s stored on the device by the application

› Review what’s stored on the device by iOS

› Keep it simple, review to remove

A New Methodology

Educating QA

› Develop test cases for new and old vulnerabilities

› Formal process for testing communications and settings

A New Methodology

Local And Remote Inputs

› User input from Apps is always a concern

› Don’t forget about responses that could be intercepted or hijacked.

› Maintain the integrity of the device.

A New Methodology

Information Leakage

› Examine all traffic to / from the application, like should be done with web applications

› Additional examination of what sensitive data may be in the binary.– Is it necessary? Keep it simple. Review to Remove.

A New Methodology

Secure Coding

What Can Go Wrong?

› Arbitrary executable code could be loaded and executed on the device

› Bypass “seatbelt”

Buffer Overflow

How To Do It Right

› Same concerns as in C› Use appropriate functions [1]– Example: strlcpy NOT strncpy

› Properly calculate buffer size (constants)› Includes integer bounds checking

Buffer Overflow

[1] http://developer.apple.com/library/mac/#documentation/Security/Conceptual/SecureCodingGuide/Articles/BufferOverflows.html

What Can Go Wrong?

› Application displays user input (as applications are known to do)

› Uses the [NSString stringWithFormat] method› Uses the printf function› Attacker sends “%s%s%s%s” instead of “Hello”

Format String Attack

How To Do It Right

› Enforce Secure Coding Standard– Just like web applications– No vulnerable function should accept untrusted

user input that could be used to determine the format of the output

Format String Attack

What Can Go Wrong?

› Application manages state using the deviceID NOT the session ID.

› Sessions not terminated properly on the server side

› Following Conditions– User logged into the application at some point in

the last day and subsequently logged out.– Attacker supplies wrong credentials through the

mobile app.

Race Conditions

What Can Go Wrong?

› Following Conditions– Application request “session refresh” while waiting

for the incorrect login response to be sent. – Server “refreshes” the session based on the device

ID.– Application receives a response indicating the login

was successful, followed by a login denied error. – Application subsequently ignores the login denied,

continues using the previous session now tied to the Device ID.

Race Conditions

How To Do It Right

› Strong server side controls over access– Policy enforcement on concurrent logins– Do not maintain session via Device ID– Properly Logout Users

› Make sure any mobile applications have the same, proper logic enforcement as web applications.

Race Conditions

What Can Go Wrong?

› Just about everything– Logic vulnerabilities– Weak session controls– Classic web application vulnerabilities– Too much trust in the client-side controls

Server Side

How To Do It Right

› Harden the server– Every client is treated like it might be malicious

› Use same guidelines as Web Apps– OWASP Secure Development

Server Side

Push Notifications

Real Fast

Push Notifications

http://www.dhanjani.com/

Secure Communications

SSL Whaaaa?› NSURL method

– iOS is secure by default in regards to SSL certs when using this method to retrieve HTTPS content

Source: http://www.flickr.com/photos/mikebaird/

Well, that’s true now…› SSLizzard

– Exploit developed by SpiderLabs to take advantage of weakness in certificate validation. [1]

– Allowed SSL MITM attacks without errors.– Apple patched this, “This vulnerability has been corrected in versions

5.0b4, 4.3.5, and 4.2.10.”

[1] TWSL2011-007: iOS SSL Implementation Does Not Validate Certificate Chain, https://www.trustwave.com/spiderlabs/advisories/TWSL2011-007.txt

SSL Whaaaa?

Source: http://www.flickr.com/photos/lenore-m/

This Is It

› The Basics› Setup For Testing› Secure Storage of Data And Credentials› Inadvertent Local Storage and Caching› Client Side Sanitization› Secure Coding› Push Notifications› Secure Communications

This Is It

Review

Summary

› Testing is easy– For you and for “them”

› Security is hard– Really just for you

› So test everything!

This Is It

kevin stadmeyer garrett held copyright trustwave 2011 confidential hacking (and defending) iphone...

copyright trustwave

city slide

maam slide

confidential dont

confidential setting

confidential garrett

trustwave spiderlabs

confidential hacking

Documents

swg version 11.0 quick start guide - trustwave

trustwave appdetectivepro version 8.7 security target

mailmarshal exchange user guide - trustwave

trustwave 2012 global güvenlik raporu

security target: trustwave siem enterprise · trustwave...

defcon 18 trustwave spiderlabs android rootkit wp

trustwave 2015securitypressuresreport final

trustwave dlp discover integration guide for google g...

trustwave network access control (nac) software version 3...

microsoft office 365 and trustwave seg cloud · trustwave...

trustwave network access control (nac) version 4.1 … ·...

executive summary: 2013 trustwave global security report

2014 trustwave global security report...victims & attackers...

sammanfattning av 2014 trustwave global security report

trustwave: inside a hacker's playbook

defending territories, defending our lives

trustwave wp global security report 2011

defcon 18 trustwave spiderlabs sniper forensics

trustwave siem lp software and siem operations edition ......

2016 security pressures report - singtel · welcome to the...