Esqlcipher

An Erlang nif library for sqlcipher.

Introduction

This library allows you to use the sqlcipher library based on the fantastic sqlite3 engine from erlang. The library is implemented as a nif library, which allows for the fastest access to a sqlite database. This can be risky, as a bug in the nif library or the sqlite database can crash the entire Erlang VM. If you do not want to take this risk, it is always possible to access the sqlite nif from a separate erlang node.

Special care has been taken not to block the scheduler of the calling process. This is done by handling all commands from erlang within a lightweight thread. The erlang scheduler will get control back when the command has been added to the command-queue of the thread.

Versions

The library currently uses Sqlcipher version 4.5.0, which is based on sqlite version 3.36.0 compiled using the following compile-time options:

-DSQLITE_DQS=0 -DSQLITE_HAS_CODEC -DSQLITE_DEFAULT_WAL_SYNCHRONOUS=1 -DSQLITE_LIKE_DOESNT_MATCH_BLOBS -DSQLITE_OMIT_DEPRECATED -DSQLITE_TEMPSTORE=2 -DSQLITE_THREADSAFE=1 -DSQLITE_USE_URI -DSQLITE_ENABLE_FTS4 -DSQLITE_ENABLE_FTS5 -DSQLITE_ENABLE_FTS3_PARENTHESIS -DSQLITE_ENABLE_JSON1 -DSQLITE_ENABLE_MATH_FUNCTIONS

Caveats

The interface could probably use some polishig. Sqlcipher mostly this works exactly like SQLite3, except for the crypto stuff. However, the Sqlcipher included in this is built using some breaking compile time options such as SQLITE_DQS = 0 (see here). This means that string literals in SQL commands must use single quotes. For instance, this:

INSERT INTO test_table VALUES('hello', 11);

works while the following will not do what you would expect:

# this is wrong!
INSERT INTO test_table VALUES("hello", 11);

See rebar.config.script for all compile options that were set!

TODO (Incomplete list)

Better testing of encryption
Primitives that support named databases (i.e. sqlite3_key_v2())
Configuration options (HMAC, PBKDF2 iterations, salts, page sizes, ...)
Testing on other platforms
...

On the Author(s)

This version is derived from Maas-Maarten Zeeman’s Erlang sqlite library esqlite. I (Felix Kiunke) merely made some smaller amendments to provide support for sqlcipher, a library that provides encryption for sqlite databases.

FelixKiunke / esqlcipher