1. Why Eve & Mallory Love Android
An Analysis of Android SSL (In)Security

3. Android Apps
Android is the most used Smartphone OS in the world with 48% market share
Over 400,000 apps in the Google Play Market
Android apps have been installed over 10 billion times
Apps process a lot of privacy-related user data and have valid reasons to transmit it over the internet

4. Problem Apps are not forced to use SSL
Apps are allowed to customize SSL so many Android apps use SSL incorrectly and are vulnerable to MITM attacks
User has no idea when Android uses SSL
Users are misinformed about the security of the connection or misinterpret warning signs

5. Able to inject virus code into an antivirus app to disable virus detection and detect arbitrary apps as a virus.

6. log-in credentials, personal documents, contacts, financial data, messages, pictures or videos.
Able to capture credentials from American Express, Paypal, various bank accounts, Facebook, Twitter, Google, Yahoo, Microsoft Live ID, etc

7. Secure Sockets Layer (SSL)
Used to establish a secure connection between a client and server.
Client receives a X.509 certificate containing the server’s public key that is signed by a certificate authority.
Client should validate certificate but this is not yet required by the SSL and X.509 standards.

8. SSL Validation Checks
Does the subject (CN) of the certificate match the client’s desired destination?
Is it a trusted Certificate Authority (CA)?
Is the signature correct?
Has the certificate expired?
Has the certificate been revoked?
Check Certificate Revocation Lists (CRLs)?
Use Online Certificate Status Protocol (OCSP)?

9. SSL Misuses in Android Trusting all certificates
Disregards the signer of the certificate and the subject
Allowing all hostnames
Does not check if certificate was issued for a given address
Trusting many Certificate Authorities
Attacks on CAs in 2011 makes trusting 134 root authorities questionable
Mixed-Mode / No SSL
Can mix secure with insecure connections or use no SSL

10. Man-in-the-Middle Attacks
MITMA: an attacker can intercept messages between conversation partners
Passive (eavesdropping) vs. active (tampering)
Mixed-Mode/No SSL allows for passive MITMA by eavesdropping on non-protected communication or allowing for SSL stripping
SSL stripping avoids SSL by replacing with
Can occur if a browsing session begins using HTTP and switches to HTTPS via a link or a redirect.

11. Evaluating Android SSL Usage
Built MalloDroid to perform static code analysis on 13,500 free apps from Google’s Play Market
Permissions
Request INTERNET and other privacy related permissions
Network API calls
HTTP transport and Non-HTTP (direct socket connections)
HTTP vs. HTTPS
HTTP only, mixed-mode (HTTP and HTTPS), or HTTPS only
HTTPS available
Able to establish a secure connection to the HTTP urls?
Deployed certificates
Evaluates SSL certificates of hosts referenced in apps
SSL Validation

12. Android SSL Usage HTTP vs. HTTPS Deployed SSL Certificates
74% could have used HTTPS instead of HTTP
46% mixed-mode, 43% HTTP only, 0.8% HTTPS only
Deployed SSL Certificates
17.3% bypass effective SSL verification by accepting all certificates or all hostnames for a from a trusted CA
Many apps include HTTPS URLs for hosts that have certificates that are either expired, self-signed, have mismatching CNs (site’s common name) or are signed by non-default-trusted CAs.
By adding an s to the url

13. MITMA: Trusting All Certificates
51% use the INTERNET permission in addition to permissions to access privacy related information
Trusting all certificates
Attack: MITMA proxy with self-signed certificate
Over half of the banking apps tested leaked login credentials, affecting an install base of 100,000 – half a million users
Windows Live Messenger service app with million users leaks login credentials for , messaging, or SkyDrive cloud storage
users’ calendars, contacts, browser histories, profile information, social streams, short messages, or exact geographic locations

14. MITMA: Trusting All Hostnames
Attack: Cert for an unrelated domain signed by startSSL
Apps, including one used by 82% of Fortune 500 companies, leaked credentials for sensitive data
Antivirus app updated virus signatures via broken SSL
Install base of 500,000 – 1 million users
Trusted that connection was secure and did no further validation
Able to send empty signature database that was accepted without informing the user
Able to create a virus signature for the antivirus which caused it to recognize itself as a virus and delete itself
cre- dentials for different services, s, text messages, contact data, bitcoin-miner API keys, premium content or access to online meetings

16. Overcoming MITMA SSL stripping Lazy SSL
Used to go to secure login page from insecure landing page
Apps with 1.5 million - 6 million installs leak login credentials for Yahoo, Facebook, and Google
Overcome by forcing HTTPS
Lazy SSL
Poor SSL validation
Overcome with SSL pinning
A custom list of trusted CAs or a custom list of specific certificates

17. Feedback to Users
Apps don’t always display visual feedback about whether the communication is secure.
clients did login and registration in SSL, but sending and receiving mail defaulted to HTTP without alerting the user.
Apps indicate that the connection is secure but are vulnerable
MITMA when they fail to establish an SSL connection or do SSL validation
Replay attack when the logins are encrypted but not fresh
Apps that did prevent MITMA failed and gave confusing error messages

20. Countermeasures: OS Solutions
Enforced certificate checking
Disallow custom SSL handling by forcing users to use standard Android API implementation
HTTPS everywhere
Integrated into communication APIs to prevent SSL stripping
Improved permissions and policies
Separate permissions for SSL and PLAIN so apps can specify
Policies like GSM_ONLY, NO_OPEN_WIFI, TRUSTED_NETWORKS to prevent MITMA
Visual security feedback
Properly inform users about connection type and security status.
MalloDroid installation protection
Integrated into app installers to warn user of unsafe apps

21. Countermeasures: Other Solutions
App Market Solutions
MalloDroid could be integrated into app market
Automatically checks apps
Could prevent apps from entering market or display the warnings in the app description
Standalone Solution: The MalloDroid App and Service
Easily deployed
Allows user to perform checks on apps before install

22. Conclusion
Google apps handle a lot of personal information for a lot of different people
Users wrongly assume, or are incorrectly informed, that they are transmitting your securely when apps are not required to use SSL
Apps are vulnerable to MITMA by failing to correctly validate the SSL certificates or by mixing HTTP with HTTPS
Instead of allowing for SSL customization, proper certificate validation should be enforced, HTTPS should be used everywhere, and permissions and policies should be separated so that apps can better protect users’ data.
Users should be better informed about how secure the connection is.