nettle-sys

Low-level Rust bindings for the Nettle cryptographic library.

The documentation can be found here.

Building

To build the Nettle bindings, you need a few libraries and support packages. Notably, you need the Nettle cryptographic library version 3.4.1 or up. Some cryptographic algorithms are only available if build against newer versions of Nettle, see optional features.

Please see below for OS-specific commands to install the needed libraries.

Debian

shell $ sudo apt install clang llvm pkg-config nettle-dev

Arch Linux

shell $ sudo pacman -S clang pkg-config nettle --needed

Fedora

shell $ sudo dnf install clang pkg-config nettle-devel

macOS (Mojave), using MacPorts

shell $ sudo port install nettle pkgconfig

Windows

MSYS2

You can install the needed libraries with the following command:

shell $ pacman -S mingw-w64-x86_64-{clang,pkg-config,nettle} libnettle-devel

Optional features

Some cryptographic algorithms are only available if build against newer versions of Nettle. Support for each feature is detected at build time.

In case the automatic detection does not work for some reason, the optional algorithms can be enabled or disabled by setting the given environment variable.

Setting such a variable to 1, y, yes, enable, or true enables a feature. Any other value disables it.

| Algorithm | Required Nettle version | Environment variable | |--------------|-------------------------|----------------------| | cv448, ed448 | >= 3.6 | NETTLEHAVECV448 | | OCB | >= 3.9 | NETTLEHAVEOCB |

Cross compilation

nettle-sys can be cross compiled using cross and a custom Docker container. First, build the container and install cross:

bash cargo install cross docker -t nettle-sys/<toolchain>:1 docker/<toolchain>

Then, you can cross compile the project:

bash cross --target <toolchain> -v

The build artifacts will be placed in target/debug/<toolchain>.

Static linking

By default, nettle-sys is dynamically linked to its dependencies.

By defining the NETTLE_STATIC environment variable during the build, it can also be statically link to its dependencies:

bash env NETTLE_STATIC=yes cargo build

This is particularly useful to produce standalone binaries that can be easily distributed.

Pregenerate bindings.rs

By default, nettle-sys invokes bindgen to generate bindings for Nettle. In some build environments, this might not work due to bindgen depending on libllvm. In this case, the bindings.rs may be pregenerated, and used by setting:

bash env NETTLE_PREGENERATED_BINDINGS=/path/to/bindings.rs cargo build

Note: bindings.rs is specific to target architecture, operating system, and Nettle version.

License

This project is licensed under either of

• GNU General Public License, Version 2.0, (LICENSE-GPL2 or https://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
• GNU General Public License, Version 3.0, (LICENSE-GPL3 or https://www.gnu.org/licenses/gpl.html)
• GNU Lesser General Public License, Version 3.0, (LICENSE-LGPL3 or https://www.gnu.org/licenses/lgpl.html)

at your option.