WhatsApp, a popular cross platform messaging application, has been in the news recently, not only for the high-profile acquisition from Facebook, but also due to security concerns. A recently published article disclosed the WhatsApp database is exposed to third-party access and is not properly secured.
The published analysis showed that WhatsApp can store both plain-text and encrypted databases on the SD card, where they could be accessed by malicious 3rd party applications. The only protection for the database is a simple AES cipher with an easily derived key, which leads to real security issues.
Because the database is encrypted as a whole, it’s very likely that at some point during application usage, the entire database itself must exist somewhere in a plain text form in order for the SQLite library to use it. This could pose a risk if the raw data became available to an attacker.
However, the most significant issue is that WhatsApp uses easily discoverable keys on the the encrypted database. Originally a static key was used to perform the encryption on all Android installations, though WhatsApp has now been updated to use a derived key based on the name of the email account on the device. In either case, this renders the encryption key available to applications running on the device, allowing exploits.
Key management is a difficult issue, requiring careful consideration during application design. Storing the key directly within the application, or derived solely based on data on the device, is a poor practice. Decompiling a binary to access the key or determine the process used to create it is a rather straight forward process. Once the key has been identified, the data is at risk.
We strongly recommend that applications ensure that key data is provided by the user (e.g. a user supplied password). It’s fine to combine that with with device data to generate a password, but that is an additional precaution. It’s equally important to pass the key material through a key derivation function with a salt in to generate the actual key for encryption. This helps protect against dictionary and brute force attacks.
In the case of WhatsApp, SQLCipher can help address some of the factors above by providing a more secure environment for application data. Coupled with a user-supplied password or pin, SQLCipher’s built in security controls would automatically provide key derivation and encryption using a unique per-database salt. This would ensure that even if two databases are created with the same password they will not have the same encryption key. Furthermore, using SQLCipher, data is only decrypted as needed, decreasing the risk of plain-text data exposure. Finally, using SQLCipher would provide additional security features to ensure the integrity of the data, preventing tampering and closing off other potential attack vectors.
Many companies both small and large depend on SQLCipher to protect their data across a variety of platforms. Because WhatsApp is already using SQLite to store data, converting to use SQLCipher in its place would require minimal modifications, something WhatsApp might consider.
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