freefare-sys

Raw FFI bindings to the public libfreefare C API.

This crate intentionally stays low level. It exposes the upstream ABI for use by higher-level Rust wrappers and NFC tooling, and does not add safe abstractions over tag access, authentication, or memory management.

What changed in 1.0.0

Version 1.0.0 is a breaking cleanup release:

• The binding surface now tracks the public freefare.h API instead of exposing generator artifacts and non-header symbols.
• Opaque native types such as MifareTag, MifareDESFireKey, Mad, and MifareDESFireAID are no longer represented as fake Rust structs with internals.
• Old Struct_* and Enum_* bindgen names were replaced with stable Rust-facing FFI names.
• Unsound Default implementations based on mem::zeroed() were removed.
• Modern Rust FFI types are used throughout (c_char, c_int, c_void, u8, u16, u32, usize, isize).
• The crate now ships smoke tests for layout assumptions and native linking.

Native dependencies

You need both libfreefare and libnfc installed on the system.

macOS with Homebrew

brew install libfreefare libnfc

Debian or Ubuntu

sudo apt install libfreefare-dev libnfc-dev

Linking

build.rs links against freefare. The nfc-sys dependency links libnfc.

By default it checks common Homebrew and Linux library directories for libfreefare. If your libfreefare installation lives elsewhere, set either the preferred LIBFREEFARE_LIB_DIR variable or the legacy LIBFREEFARE_PATH variable:

export LIBFREEFARE_LIB_DIR=/custom/prefix/lib

Usage

[dependencies]
freefare-sys = "1"
libc = "0.2"
nfc-sys = "1"

Example

use std::ffi::CStr;
use std::ptr;

fn main() {
    unsafe {
        let mut context: *mut nfc_sys::nfc_context = ptr::null_mut();
        nfc_sys::nfc_init(&mut context);
        assert!(!context.is_null());

        let device = nfc_sys::nfc_open(context, ptr::null());
        if device.is_null() {
            nfc_sys::nfc_exit(context);
            return;
        }

        let tags = freefare_sys::freefare_get_tags(device);
        if !tags.is_null() && !(*tags).is_null() {
            let tag = *tags;
            let uid = freefare_sys::freefare_get_tag_uid(tag);

            if !uid.is_null() {
                println!("tag uid: {}", CStr::from_ptr(uid).to_string_lossy());
                libc::free(uid.cast());
            }

            freefare_sys::freefare_free_tags(tags);
        }

        nfc_sys::nfc_close(device);
        nfc_sys::nfc_exit(context);
    }
}

Safety

This crate exposes raw C bindings. Callers are responsible for:

• Upholding all pointer validity and lifetime requirements from libfreefare.
• Freeing memory returned by the native library with the correct native deallocator.
• Ensuring linked libfreefare and libnfc versions are ABI-compatible with the declarations in this crate.

Versioning

The Rust crate version follows the Rust FFI surface, not the upstream libfreefare release number. Breaking binding corrections or symbol removals may require a new major version even when the C library version is unchanged.

License

MIT