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