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https://github.com/resilar/sqleet
SQLite3 encryption that sucks less
https://github.com/resilar/sqleet
cryptography encryption sqlite sqlite3
Last synced: 4 months ago
JSON representation
SQLite3 encryption that sucks less
- Host: GitHub
- URL: https://github.com/resilar/sqleet
- Owner: resilar
- License: unlicense
- Created: 2017-09-23T19:24:15.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2023-05-03T13:00:06.000Z (over 1 year ago)
- Last Synced: 2024-06-22T07:49:26.557Z (6 months ago)
- Topics: cryptography, encryption, sqlite, sqlite3
- Language: C
- Size: 5.53 MB
- Stars: 372
- Watchers: 27
- Forks: 53
- Open Issues: 15
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
**Warning:** This project is currently unmaintained due to [the deprecation of
codec API](https://www.sqlite.org/src/timeline?c=5a877221ce90e752) in SQLite3
upstream. Therefore, sqleet is stuck at SQLite version 3.31.1 until a *major*
rewrite happens. Meanwhile, I recommend using
[wxSQLite3](https://github.com/utelle/wxsqlite3) which offers sqleet-compatible
encryption for the latest version(s) of SQLite3.
---
**sqleet** is an encryption extension for [SQLite3](https://www.sqlite.org/).
The encryption is transparent (*on-the-fly*) and based on modern cryptographic
algorithms designed for high performance in software and robust side-channel
resistance. The compilation of sqleet is easy because there are no external
dependencies, which simplifies cross-compiling and cross-platform development.
In the spirit of SQLite3, the sqleet source code is in the public domain.
- [Compiling](#compiling)
- [Example](#example)
- [Cryptography](#cryptography)
- [sqleet API](#sqleet-api)
- [C programming interface](#c-programming-interface)
- [URI configuration interface](#uri-configuration-interface)
- [Android/iOS support](#androidios-support)
- [Versioning scheme](#versioning-scheme)
- [License](#license)
Compiling
---------
SQLite3 shell with sqleet encryption support can be compiled as follows:
```sh
% # UNIX
% gcc sqleet.c shell.c -o sqleet -lpthread -ldl
% # Windows
% gcc sqleet.c shell.c -o sqleet
```
[Example](#example) demonstrates the use of the sqleet encryption extension with
the compiled shell. For application programmers, [sqleet API](#sqleet-api)
offers [C programming interface](#c-programming-interface) and language-agnostic
[URI-based configuration interface](#uri-configuration-interface) for run-time
management of the encryption settings.
To use sqleet as a library, the recommended way is to download a preconfigured
[release package](https://github.com/resilar/sqleet/releases/latest) instead of
cloning the git repository. Release package contains `sqleet.c` and `sqleet.h`
amalgamations that are drop-in replacements for the official `sqlite3.c` and
`sqlite3.h` amalgamations. Non-amalgamated `sqleet.c` and `sqleet.h` files from
master branch can be used as drop-in replacements similarly, assuming all
necessary sqleet source files are available during compilation. However, sqleet
development mainly happens in the master branch, so release are considered to be
more stable and a better choice for the average user.
Building a custom release version of sqleet is a straightforward task.
* Clone or fork sqleet and patch it as you wish
* Create source and header amalgamations for release
* `./script/amalgamate.sh sqlame.c`
* `./script/amalgamate.sh sqlame.h`
* Package the amalgamations with other release files
[script/release.sh](script/release.sh) shows the exact release procedure of
sqleet.
Example
-------
Encrypting an existing database `hello.db` with a *key* (i.e., password)
`"swordfish"`.
```
[sqleet]% hexdump -C hello.db
00000000 53 51 4c 69 74 65 20 66 6f 72 6d 61 74 20 33 00 |SQLite format 3.|
00000010 10 00 01 01 00 40 20 20 00 00 00 01 00 00 00 02 |.....@ ........|
*
00000fd0 00 00 00 2b 01 06 17 17 17 01 37 74 61 62 6c 65 |...+......7table|
00000fe0 68 65 6c 6c 6f 68 65 6c 6c 6f 02 43 52 45 41 54 |hellohello.CREAT|
00000ff0 45 20 54 41 42 4c 45 20 68 65 6c 6c 6f 28 78 29 |E TABLE hello(x)|
*
00001fe0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0f |................|
00001ff0 01 02 27 48 65 6c 6c 6f 2c 20 77 6f 72 6c 64 21 |..'Hello, world!|
[sqleet]% ./sqleet hello.db
SQLite version 3.28.0 2019-04-16 19:49:53
Enter ".help" for usage hints.
sqlite> PRAGMA rekey='swordfish';
sqlite> .quit
[sqleet]% hexdump -C hello.db
00000000 4e 61 0c 1a 25 3f 77 1e 20 50 f4 56 61 c6 b3 37 |Na..%?w. P.Va..7|
00000010 eb aa d5 59 37 0d e6 41 1d d1 69 c8 8e 9a f5 eb |...Y7..A..i.....|
*
00001fe0 07 79 a0 3b f1 cc 9f 7b b2 72 11 21 28 15 71 ce |.y.;...{.r.!(.q.|
00001ff0 e5 ad 4a cd 75 af 8e 8a e2 79 f3 d9 2e 21 e8 4b |..J.u....y...!.K|
```
Notice that the data of the encrypted database is indistinguishable from random.
After encryption, the unencrypted data is accessible only with the correct key.
```
[sqleet]% ./sqleet hello.db
SQLite version 3.28.0 2019-04-16 19:49:53
Enter ".help" for usage hints.
sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
/**** ERROR: (26) file is not a database *****/
ROLLBACK; -- due to errors
sqlite> PRAGMA key='swordfish';
sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE hello(x);
INSERT INTO hello VALUES('Hello, world!');
COMMIT;
```
Instead of `PRAGMA` commands, the key can also be provided in [SQLite3 URI
filename](https://www.sqlite.org/uri.html) using `key` parameter.
```
[sqleet]% ./sqleet 'file:hello.db?key=swordfish' 'SELECT * FROM hello'
Hello, world!
```
Cryptography
------------
- PBKDF2-HMAC-SHA256 key derivation with a 16-byte salt and 12345 iterations.
- ChaCha20 stream cipher with one-time keys.
- Poly1305 authentication tags.
A low-level description of the database encryption scheme is available in
[sqleet.c:265](sqleet.c#L265).
sqleet API
----------
The public sqleet API consists of [C programming
interface](#c-programming-interface) and [URI configuration
interface](#uri-configuration-interface).
### C programming interface
sqleet defines `SQLITE_HAS_CODEC` compile-time option to expose SQLite3
encryption API, i.e., C functions `sqlite3_key()` and `sqlite3_rekey()` for
managing database encryption keys. These functions can be called directly from
C code, while other programming languages need to call the C functions via
[FFI](https://en.wikipedia.org/wiki/Foreign_function_interface) mechanism.
Another way to invoke the functions is with `PRAGMA key` and `PRAGMA rekey`
commands (see [Example](#example)).
```c
SQLITE_API int sqlite3_key( /* Invoked by PRAGMA key='x' */
sqlite3 *db, /* Database to key */
const void *pKey, int nKey /* Key (password) */
);
```
`sqlite3_key()` is typically called immediately after `sqlite3_open()` to
specify an encryption key (password) for the opened database. The function
validates the key by decrypting the first page of the database from disk.
Return value is `SQLITE_OK` if the given key was correct; otherwise, a non-zero
SQLite3 error code is returned and subsequent attempts to read or write the
database will fail.
```c
SQLITE_API int sqlite3_rekey( /* Invoked by PRAGMA rekey='x' */
sqlite3 *db, /* Database to rekey */
const void *pKey, int nKey /* New key (password) */
);
```
`sqlite3_rekey()` changes the database encryption key. This includes encrypting
the database the first time, fully decrypting the database (if `nKey == 0`), as
well as re-encrypting it with a new key. Internally, the function runs `VACUUM`
command to encrypt or decrypt all pages of the database, whereas re-encryption
with a new key is performed directly by processing each page sequentially.
Return value is `SQLITE_OK` on success and an SQLite3 error code on failure.
In addition, there are `sqlite3_key_v2()` and `sqlite3_rekey_v2()` functions
that accept name of the target database as the second parameter.
---
**Note**: \
In sqleet, the contents of an encrypted database file are indistinguishable from
random data (of the same length). This is a conscious design decision, but as a
drawback, database settings cannot be read from the database file. Therefore, it
is the user's responsibility to properly initialize database settings before
accessing the database. The most common issue is that opening a database fails
regardless of valid key because the page size of the database differs from the
default 4096 and `page_size` has not been set to the correct value with `PRAGMA`
or [URI API](#uri-configuration-interface).
The official [SQLite Encryption Extension (SEE)](https://www.sqlite.org/see)
leaves bytes 16..23 of the database header unencrypted so that page size and
other settings can be directly read from encrypted databases, which obviously
makes SEE-encrypted databases distinguishable from random data. In sqleet, this
behavior can be optionally enabled with `-DSKIP_HEADER_BYTES=24` compile-time
flag (bytes 0..15 contain the KDF salt so only the bytes 16..23 are actually
skipped and left unencrypted). At run-time, the compile-time default can be
overridden with URI parameter `skip=n` where `n` is the skip amount.
---
### URI configuration interface
**Disclaimer**: URI interface is experimental and subject to changes in future
versions. Use at your own risk!
Run-time configuration of sqleet encryption is implemented based on [SQLite3
URI filenames](https://www.sqlite.org/uri.html) which contain configuration
parameters for databases. List of URI parameters supported by sqleet:
| Parameter | Description |
| :---------- | :------------------------------------------------------------- |
| `key` | Encryption key for `sqlite3_key()` after opening the database |
| `salt` | 16-byte salt for the key derivation function (KDF) |
| `header` | 16-byte header overwriting the database magic header (or salt) |
| `kdf` | Key derivation function (only `none` supported for now) |
| `skip` | Run-time setting overriding compile-time SKIP_HEADER_BYTES |
| `page_size` | Equivalent to `page_size` PRAGMA |
Parameters `key`, `salt` and `header` have additional `hex`-prefixed versions
that accept hex input strings such as `'73716c656574'`.
Parameters `salt` and `header` expect 16-byte input strings. Shorter strings are
zero-padded to 16-bytes, while longer inputs get automatically rejected.
Parameter `header` represents the first 16 bytes of the database file, that is,
SQLite3 magic header string for unencrypted databases. For encrypted databases,
`header` defaults to the value of `salt` unless explicitly set to other value.
Remember that `salt` is a parameter for the key derivation function (KDF) which
is stored in the beginning of the database file *by default*, in which case both
`salt` and `header` contain the same value (KDF salt). Sometimes, however, the
user may want to keep the salt secret, or control the first 16 bytes of the
database file for some purpose. In such cases, the user stores the salt and then
overwrites the beginning of the database file with any 16-byte `header` value.
(If this explanation was too abstract or nonsensical to fully grasp, see the iOS
workaround in the end of [Android/iOS support](#androidios-support) for a
practical real-world use-case of `header` feature).
URI parameter `kdf=none` disables the default PBKDF2-HMAC-SHA256 key derivation.
If KDF is disabled, `key` and `hexkey` accept a 32-byte *raw key* that becomes
the *master* encryption key which otherwise would be derived by the KDF from the
key and salt. Disabling KDF is a powerful feature for *advanced users* who need
full control of the key derivation process.
Parameters `skip` and `page_size` override the compile-time `SKIP_HEADER_BYTES`
value and the database `PRAGMA page_size` configuration.
Changing URI settings of an existing database can be accomplished with `VACUUM
INTO` (introduced in SQLite 3.27.0) by giving new URI parameter values in the
`INTO` filename. For example, `VACUUM INTO 'file:skipped.db?skip=24'` vacuums
the current main database to file `skipped.db` with `skip` set to 24. Other URI
settings, including the encryption key, are inherited from the main database
unless `key` parameter is specified, in which case any undefined parameters are
initialized to default values. Database settings update with `VACUUM INTO` is
complex operation with many special cases and important details (omitted here).
So be prepared for some undocumented behavior, but please open an issue if
encountering obviously broken on wrong behavior.
Erroneus parameters, such as unsupported parameter value or otherwise bad input,
returns a non-zero SQLite3 error code when opening (or vacuuming) a database.
The current version returns `SQLITE_MISUSE` error, in most cases, if URI parsing
fails or the resulting configuration is invalid.
Android/iOS support
-------------------
sqleet does not have an out-of-the-box support for Android. However, [SQLite
Android Bindings](https://www.sqlite.org/android/doc/trunk/www/index.wiki)
project provides an easy way to bundle a custom SQLite3 version (such as
sqleet) into an Android application with the standard Android interface
[`android.database.sqlite`](https://developer.android.com/reference/android/database/sqlite/package-summary).
In particular, see [Using The SQLite Encryption
Extension](https://www.sqlite.org/android/doc/trunk/www/see.wiki) page for
build & usage instructions.
Likewise, sqleet does not offer an iOS version either, but compiling a custom
SQLite3 with sqleet encryption support for iOS is a straightforward task (e.g.,
compile [switflyfalling/SQLiteLib](https://github.com/swiftlyfalling/SQLiteLib)
with sqleet release amalgamation instead of the SQLite3 amalgamation).
Moreover, iOS apps with an *encrypted* WAL-journaled SQLite3 database in a
shared data container are terminated when sent to the background (see
[sqlcipher/sqlcipher#255](https://github.com/sqlcipher/sqlcipher/issues/255),
[TN2408](https://developer.apple.com/library/archive/technotes/tn2408/_index.html)
and
[TN2151](https://developer.apple.com/library/archive/technotes/tn2151/_index.html)
for more information). A common workaround is to leave the first 32 bytes of
the database file unencrypted so that iOS recognizes the file as a regular
WAL-journaled SQLite3 database and does not terminate the app. Thus, an
iOS-compatible sqleet database can be created with the following URI settings:
```
[sqleet]% ./sqleet 'file:ios.db?key=swordfish&salt=SodiumChloride42&header=SQLite%20format%203&skip=32'
SQLite version 3.28.0 2019-04-16 19:49:53
Enter ".help" for usage hints.
sqlite> CREATE TABLE f(x,y);
sqlite> .quit
[sqleet]% xxd secrets.db | head -n5
00000000: 5351 4c69 7465 2066 6f72 6d61 7420 3300 SQLite format 3.
00000010: 1000 0101 2040 2020 0000 0001 0000 0002 .... @ ........
00000020: 4640 824c 703e 3f72 dffc 3a19 23a6 c964 [email protected]>?r..:.#..d
00000030: a1b3 abf0 8f3c 996f 0eb8 c665 afe1 0d72 .....<.o...e...r
00000040: b864 57f7 2492 8c31 6398 61d0 5d49 5a28 .dW.$..1c.a.]IZ(
```
Versioning scheme
-----------------
[sqleet releases](https://github.com/resilar/sqleet/releases/) follow a
perverse form of semantic versioning which requires some explanation. Major
version number increments indicate compatibility breaks as usual, but the minor
and patch version numbers match the targeted SQLite3 version. For instance,
sqleet v0.25.1 corresponds to SQLite v3.25.1. Although the target SQLite3
version is the primarily supported, sqleet is typically forward and backward
compatible across different SQLite3 versions without any changes to the code.
As a corollary, sqleet releases are published whenever a new SQLite3 version is
released. A new sqleet release thus does not necessarily include bug fixes or
new features (except updated SQLite3 version) if there has been no commits to
sqleet master branch since the previous SQLite3 release. [Releases
page](https://github.com/resilar/sqleet/releases) contains a changelog for each
sqleet release version.
License
-------
Like SQLite3, sqleet has been released in the public domain (specifically,
under the [UNLICENSE](https://unlicense.org/) license). In other words, feel
free to do whatever the fuck you want to with the code. In the unlikely case
that your country's legal system is broken with respect to public domain
software, contact `[email protected]` for a custom-licensed version.