[CVE-2014-0647] Insecure Data Storage of User Data Elements in Starbucks v2.6.1 iOS mobile application

[Daniel Wood <daniel.wood () owasp org>]

Title: [CVE-2014-0647] Insecure Data Storage of User Data Elements in Starbucks v2.6.1 iOS mobile application
Published: January 13, 2014
Reported to Vendor: December 2013 (no direct response)
CVE Reference: CVE-2014-0647
Credit: This issue was discovered by Daniel E. Wood
http://www.linkedin.com/in/danielewood

Product: Starbucks iOS mobile application
Version: 2.6.1 (May 02, 2013)
Vendor: Starbucks Coffee Company
URL: https://itunes.apple.com/us/app/starbucks/id331177714

Issue:  Username, email address, and password elements are being stored in clear-text in the session.clslog crashlytics 
log file.
Location:       /Library/Caches/com.crashlytics.data/com.starbucks.mystarbucks/session.clslog

Within session.clslog there are multiple instances of the storage of clear-text credentials that can be recovered and 
leveraged for unauthorized usage of a users account on the malicious users’ own device or online at 
https://www.starbucks.com/account/signin.  It contains the HTML of the mobile application page that performs the 
account login or account reset.  session.clslog also contains the OAuth token (signed with HMAC-SHA1) and OAuth 
signature for the users account/device to the Starbucks service.

From session.clslog:
<div class="block_login">
<form action="/OAuth/sign-in" class="siren" id="accountForm" method="post">
        <fieldset class="login_position">
                <legend><span class="group-header">I have a Starbucks account.</span></legend>
                
                [...snip...]
                
                <li>
                        <label for="Account_UserName" class="">Username <span class='req'>*</span></label>
                        <span class="x">
                                <input class="field text medium" id="Account_UserName" maxlength="200" 
name="Account.UserName" tabindex="0" type="text" value="CLEARTEXT" />
                                </span>
                </li>
                <li>
                        <label for="Account_PassWord" class="">Password <span class='req'>*</span></label>
                        <span class="x">
                                <input class="field text medium" id="Account_PassWord" maxlength="200" 
name="Account.PassWord" tabindex="0" type="password" value="CLEARTEXT" />
                        </span>
                </li>

43440 $ -[AccountManager forgotPasswordEmail:withUserName:] line 1609 $ BODY STRING:[ 
{"emailAddress":"CLEARTEXT","userName":"CLEARTEXT"} ]

Note: All references of 'CLEARTEXT' above are the cleartext values of each referenced string.


Mitigation:
To prevent sensitive user data (credentials) from being recovered by a malicious user, output sanitization should be 
conducted to prevent these data elements from being stored in the crashlytics log files in clear-text, if at all.
        
iOS Specific Best Practices (from OWASP Mobile Top 10 - M1 Insecure Data Storage):
- Never store credentials on the phone file system. Force the user to authenticate using a standard web or API login 
scheme (over HTTPS) to the application upon each opening and ensure session timeouts are set at the bare minimum to 
meet the user experience requirements.
- Where storage or caching of information is necessary consider using a standard iOS encryption library such as 
CommonCrypto
- If the data is small, using the provided apple keychain API is recommended but, once a phone is jailbroken or 
exploited the keychain can be easily read. This is in addition to the threat of a bruteforce on the devices PIN, which 
as stated above is trivial in some cases.
- For databases consider using SQLcipher for Sqlite data encryption
- For items stored in the keychain leverage the most secure API designation, kSecAttrAccessibleWhenUnlocked (now the 
default in iOS 5) and for enterprise managed mobile devices ensure a strong PIN is forced, alphanumeric, larger than 4 
characters.
- For larger or more general types of consumer-grade data, Apple’s File Protection mechanism can safely be used (see 
NSData Class Reference for protection options).
- Avoid using NSUserDefaults to store senstitve pieces of information as it stores data in plist files.
- Be aware that all data/entities using NSManagedObects will be stored in an unencrypted database file.

References:
http://try.crashlytics.com/security/
https://developer.apple.com/library/mac/documentation/Security/Conceptual/SecureCodingGuide/SecurityDevelopmentChecklists/SecurityDevelopmentChecklists.html#//apple_ref/doc/uid/TP40002415-CH1-SW1
https://www.owasp.org/index.php/IOS_Developer_Cheat_Sheet#Insecure_Data_Storage_.28M1.29

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