Add linux_rustix opt-in backend (#520)

This backend can be useful for `libc`-free applications and libraries.
It's also used by default on `*-unknown-linux-none` targets.

Author: newpavlov

.github/workflows/nopanic.yaml

@@ -40,6 +40,14 @@ jobs:
       - name: Check (linux_android.rs)
         run: ret=$(grep panic target/release/libgetrandom_wrapper.so; echo $?); [ $ret -eq 1 ]
 
+      # TODO: re-enable after https://github.com/bytecodealliance/rustix/pull/1184 is released
+      # - name: Build (linux_rustix.rs)
+      #   env:
+      #     RUSTFLAGS: -Dwarnings --cfg getrandom_backend="linux_rustix"
+      #   run: cargo build --release
+      # - name: Check (linux_rustix.rs)
+      #   run: ret=$(grep panic target/release/libgetrandom_wrapper.so; echo $?); [ $ret -eq 1 ]
+
       - name: Build (rdrand.rs)
         env:
           RUSTFLAGS: -Dwarnings --cfg getrandom_backend="rdrand"

.github/workflows/tests.yml

@@ -71,6 +71,9 @@ jobs:
       - env:
           RUSTFLAGS: -Dwarnings --cfg getrandom_backend="linux_getrandom"
         run: cargo test ${{ matrix.cargo_test_opts }} --target=${{ matrix.target }} --features=std
+      - env:
+          RUSTFLAGS: -Dwarnings --cfg getrandom_backend="linux_rustix"
+        run: cargo test ${{ matrix.cargo_test_opts }} --target=${{ matrix.target }} --features=std
       - env:
           RUSTFLAGS: -Dwarnings --cfg getrandom_test_linux_fallback
         run: cargo test --features=std

.github/workflows/workspace.yml

@@ -53,6 +53,10 @@ jobs:
       env:
         RUSTFLAGS: -Dwarnings --cfg getrandom_backend="linux_getrandom"
       run: cargo clippy --target x86_64-unknown-linux-gnu
+    - name: Linux (linux_rustix.rs)
+      env:
+        RUSTFLAGS: -Dwarnings --cfg getrandom_backend="linux_rustix"
+      run: cargo clippy --target x86_64-unknown-linux-gnu
     - name: Linux (linux_android_with_fallback.rs)
       run: cargo clippy --target x86_64-unknown-linux-gnu
     - name: NetBSD (netbsd.rs)

CHANGELOG.md

@@ -28,7 +28,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `wasm32-wasip1` and `wasm32-wasip2` support [#499]
 - `getrandom_backend` configuration flag for selection of opt-in backends [#504]
 - `Error::new_custom` method [#507]
-- AArch64 RNDR register opt-in backend [#512]
+- `rndr` opt-in backend [#512]
+- `linux_rustix` opt-in backend [#520]
 
 [#415]: https://github.com/rust-random/getrandom/pull/415
 [#440]: https://github.com/rust-random/getrandom/pull/440
@@ -40,6 +41,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 [#504]: https://github.com/rust-random/getrandom/pull/504
 [#507]: https://github.com/rust-random/getrandom/pull/507
 [#512]: https://github.com/rust-random/getrandom/pull/512
+[#520]: https://github.com/rust-random/getrandom/pull/520
 
 ## [0.2.15] - 2024-05-06
 ### Added

Cargo.toml

@@ -18,31 +18,68 @@ cfg-if = "1"
 compiler_builtins = { version = "0.1", optional = true }
 core = { version = "1.0", optional = true, package = "rustc-std-workspace-core" }
 
-[target.'cfg(unix)'.dependencies]
+# linux_android / linux_android_with_fallback
+[target.'cfg(all(any(target_os = "linux", target_os = "android"), not(any(target_env = "", getrandom_backend = "linux_rustix", getrandom_backend = "custom"))))'.dependencies]
 libc = { version = "0.2.154", default-features = false }
 
+# linux_rustix
+[target.'cfg(all(any(target_os = "linux", target_os = "android"), any(target_env = "", getrandom_backend = "linux_rustix")))'.dependencies]
+rustix = { version = "0.38", default-features = false, features = ["rand"] }
+
+# apple-other
+[target.'cfg(any(target_os = "ios", target_os = "visionos", target_os = "watchos", target_os = "tvos"))'.dependencies]
+libc = { version = "0.2.154", default-features = false }
+
+# getentropy
+[target.'cfg(any(target_os = "macos", target_os = "openbsd", target_os = "vita", target_os = "emscripten"))'.dependencies]
+libc = { version = "0.2.154", default-features = false }
+
+# getrandom
+[target.'cfg(any(target_os = "dragonfly", target_os = "freebsd", target_os = "hurd", target_os = "illumos", all(target_os = "horizon", target_arch = "arm")))'.dependencies]
+libc = { version = "0.2.154", default-features = false }
+
+# netbsd
+[target.'cfg(target_os = "netbsd")'.dependencies]
+libc = { version = "0.2.154", default-features = false }
+
+# solaris
+[target.'cfg(target_os = "solaris")'.dependencies]
+libc = { version = "0.2.154", default-features = false }
+
+# use_file
+[target.'cfg(any(target_os = "haiku", target_os = "redox", target_os = "nto", target_os = "aix"))'.dependencies]
+libc = { version = "0.2.154", default-features = false }
+
+# vxworks
+[target.'cfg(target_os = "vxworks")'.dependencies]
+libc = { version = "0.2.154", default-features = false }
+
+# wasi (0.2 only)
 [target.'cfg(all(target_arch = "wasm32", target_os = "wasi", target_env = "p2"))'.dependencies]
 wasi = { version = "0.13", default-features = false }
 
+# windows7
 [target.'cfg(all(windows, not(target_vendor = "win7")))'.dependencies]
 windows-targets = "0.52"
 
+# wasm_js
 [target.'cfg(all(getrandom_backend = "wasm_js", any(target_arch = "wasm32", target_arch = "wasm64"), target_os = "unknown"))'.dependencies]
 wasm-bindgen = { version = "0.2.89", default-features = false }
 js-sys = "0.3"
-[target.'cfg(all(getrandom_backend = "wasm_js", getrandom_browser_test, any(target_arch = "wasm32", target_arch = "wasm64"), target_os = "unknown"))'.dev-dependencies]
+[target.'cfg(all(getrandom_backend = "wasm_js", getrandom_browser_test, target_arch = "wasm32", target_os = "unknown"))'.dev-dependencies]
 wasm-bindgen-test = "0.3.39"
 
 [features]
-# Implement std-only traits for getrandom::Error
+# Implement std::error::Error for getrandom::Error and
+# use std to retrieve OS error descriptions
 std = []
 # Unstable feature to support being a libstd dependency
 rustc-dep-of-std = ["compiler_builtins", "core"]
 
 [lints.rust.unexpected_cfgs]
 level = "warn"
 check-cfg = [
-  'cfg(getrandom_backend, values("custom", "rdrand", "rndr", "linux_getrandom", "wasm_js", "esp_idf"))',
+  'cfg(getrandom_backend, values("custom", "rdrand", "rndr", "linux_getrandom", "linux_rustix", "wasm_js", "esp_idf"))',
   'cfg(getrandom_browser_test)',
   'cfg(getrandom_test_linux_fallback)',
 ]

src/lib.rs

@@ -6,14 +6,14 @@
 //! | ------------------ | ------------------ | --------------
 //! | Linux, Android     | `*‑linux‑*`        | [`getrandom`][1] system call if available, otherwise [`/dev/urandom`][2] after successfully polling `/dev/random`
 //! | Windows 10+        | `*‑windows‑*`      | [`ProcessPrng`]
-//! | Windows 7 and 8    | `*-win7‑windows‑*` | [`RtlGenRandom`]
+//! | Windows 7, 8       | `*-win7‑windows‑*` | [`RtlGenRandom`]
 //! | macOS              | `*‑apple‑darwin`   | [`getentropy`][3]
 //! | iOS, tvOS, watchOS | `*‑apple‑ios`, `*-apple-tvos`, `*-apple-watchos` | [`CCRandomGenerateBytes`]
 //! | FreeBSD            | `*‑freebsd`        | [`getrandom`][5]
 //! | OpenBSD            | `*‑openbsd`        | [`getentropy`][7]
 //! | NetBSD             | `*‑netbsd`         | [`getrandom`][16] if available, otherwise [`kern.arandom`][8]
 //! | Dragonfly BSD      | `*‑dragonfly`      | [`getrandom`][9]
-//! | Solaris            | `*‑solaris`        | [`getrandom`][11] (with `GRND_RANDOM`)
+//! | Solaris            | `*‑solaris`        | [`getrandom`][11] with `GRND_RANDOM`
 //! | illumos            | `*‑illumos`        | [`getrandom`][12]
 //! | Fuchsia OS         | `*‑fuchsia`        | [`cprng_draw`]
 //! | Redox              | `*‑redox`          | `/dev/urandom`
@@ -41,6 +41,7 @@
 //! | Backend name      | Target               | Target Triple        | Implementation
 //! | ----------------- | -------------------- | -------------------- | --------------
 //! | `linux_getrandom` | Linux, Android       | `*‑linux‑*`          | [`getrandom`][1] system call (without `/dev/urandom` fallback). Bumps minimum supported Linux kernel version to 3.17 and Android API level to 23 (Marshmallow).
+//! | `linux_rustix`    | Linux, Android       | `*‑linux‑*`          | Same as `linux_getrandom`, but uses [`rustix`] instead of `libc`.
 //! | `rdrand`          | x86, x86-64          | `x86_64-*`, `i686-*` | [`RDRAND`] instruction
 //! | `rndr`            | AArch64              | `aarch64-*`          | [`RNDR`] register
 //! | `esp_idf`         | ESP-IDF              | `*‑espidf`           | [`esp_fill_random`]. WARNING: can return low quality entropy without proper hardware configuration!
@@ -243,6 +244,7 @@
 //! [platform-support]: https://doc.rust-lang.org/stable/rustc/platform-support.html
 //! [WASI]: https://github.com/CraneStation/wasi
 //! [Emscripten]: https://www.hellorust.com/setup/emscripten/
+//! [`rustix`]: https://docs.rs/rustix
 
 #![doc(
     html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
@@ -295,6 +297,8 @@ cfg_if! {
     } else if #[cfg(getrandom_backend = "linux_getrandom")] {
         mod util_libc;
         #[path = "linux_android.rs"] mod imp;
+    } else if #[cfg(getrandom_backend = "linux_rustix")] {
+        #[path = "linux_rustix.rs"] mod imp;
     } else if #[cfg(getrandom_backend = "rdrand")] {
         mod lazy;
         #[path = "rdrand.rs"] mod imp;

src/linux_rustix.rs

@@ -0,0 +1,30 @@
+//! Implementation for Linux / Android without `/dev/urandom` fallback
+use crate::{Error, MaybeUninit};
+use rustix::rand::{getrandom_uninit, GetRandomFlags};
+
+#[cfg(not(any(target_os = "android", target_os = "linux")))]
+compile_error!("`linux_rustix` backend can be enabled only for Linux/Android targets!");
+
+pub fn getrandom_inner(mut dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
+    loop {
+        let res = getrandom_uninit(dest, GetRandomFlags::empty()).map(|(res, _)| res.len());
+        match res {
+            Ok(0) => return Err(Error::UNEXPECTED),
+            Ok(res_len) => {
+                dest = dest.get_mut(res_len..).ok_or(Error::UNEXPECTED)?;
+                if dest.is_empty() {
+                    return Ok(());
+                }
+            }
+            Err(rustix::io::Errno::INTR) => continue,
+            Err(err) => {
+                let code = err
+                    .raw_os_error()
+                    .wrapping_neg()
+                    .try_into()
+                    .map_err(|_| Error::UNEXPECTED)?;
+                return Err(Error::from_os_error(code));
+            }
+        }
+    }
+}