nt-hive

by Colin Finck <colin@reactos.org>

The nt-hive Rust crate provides a comfortable and safe interface for accessing keys, values, and data stored in hive files. Hive files can be found in C:\Windows\system32\config and store what is commonly called the Windows registry. This crate supports the hive format that is used from Windows NT 4.0 up to the current Windows 10.

nt-hive has been developed as part of a Rust bootloader project. Its current feature set is therefore aligned to the needs of a ReactOS/Windows bootloader.

Features

• Support for reading keys, values, and data from any byte slice containing hive data (i.e. anything that implements zerocopy::ByteSlice).
• Basic in-memory modifications of hive data (as required for a bootloader).
• Iterators for keys and values to enable writing idiomatic Rust code.
• Functions to find a specific subkey, subkey path, or value as efficient as possible (taking advantage of binary search for keys).
• Error propagation through a custom NtHiveError type that implements Display.
  As a bootloader may hit corrupted hive files at some point, nt-hive outputs precise errors everywhere that refer to the faulty data byte.
• Full functionality even in a no_std environment (with alloc, some limitations without alloc).
• Static borrow checking everywhere. No mutexes or runtime borrowing.
• Zero-copy data representations wherever possible.
• No usage of unsafe anywhere. Checked arithmetic where needed.
• Platform and endian independence.

Non-Goals

Full write support is currently not a goal for nt-hive. This would require a wholly different architecture, where nt-hive loads a hive into linked in-memory data structures, keeps track of changes, and can write changes back to disk (possibly extending the on-disk file). The current focus on read-only access allows for a simpler architecture.

Examples

The following example reads the List value from the ControlSet001\Control\ServiceGroupOrder subkey of the SYSTEM hive, which is a real thing that happens during boot:

let mut buffer = Vec::new();
File::open("SYSTEM").unwrap().read_to_end(&mut buffer).unwrap();

let hive = Hive::new(buffer.as_ref()).unwrap();
let root_key_node = hive.root_key_node().unwrap();
let key_node = root_key_node.subpath("ControlSet001\\Control\\ServiceGroupOrder").unwrap().unwrap();
let key_value = key_node.value("List").unwrap().unwrap();

let multi_sz_data = key_value.multi_string_data();
if let Ok(vec) = multi_sz_data {
    println!("Vector of REG_MULTI_SZ lines: {vec:?}");
}

Check out the docs, the tests, and the supplied readhive example application for more ideas how to use nt-hive.

Contributing and License

Contributions are currently preferred in the form of bug reports. If you encounter a bug, an unexpected panic, or a potentially unsafe calculation, please file a bug report.

nt-hive is available under GNU General Public License 2.0 or (at your option) any later version. This license fits well with the projects I'm planning to use nt-hive for, and should allow integration into any open-source project.
I may however put nt-hive under a more permissive license later if you give me a good reason.

As relicensing requires permission from every contributor, I only accept code contributions that are explicitly put under Creative Commons Zero (CC0). If that is not an option for you, you are still very welcome to suggest your change in a bug report.

Further Resources

• Windows registry file format specification by Maxim Suhanov
• cmlib library by the ReactOS Project