feat: Add support for Ariel OS

.github/workflows/workspace.yml

@@ -37,6 +37,10 @@ jobs:
       env:
         RUSTFLAGS: -Dwarnings --cfg getrandom_backend="esp_idf"
       run: cargo clippy -Zbuild-std=core --target riscv32imc-esp-espidf
+    - name: Ariel OS (ariel_os.rs)
+      env:
+        RUSTFLAGS: -Dwarnings --cfg getrandom_backend="ariel-os"
+      run: cargo clippy -Zbuild-std=core --target riscv32imac-unknown-none-elf
     - name: Fuchsia (fuchsia.rs)
       run: cargo clippy -Zbuild-std=core --target x86_64-unknown-fuchsia
     - name: OpenBSD (getentropy.rs)

Cargo.toml

@@ -74,10 +74,15 @@ js-sys = { version = "0.3.77", default-features = false, optional = true }
 [target.'cfg(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "none")))'.dev-dependencies]
 wasm-bindgen-test = "0.3"
 
+# ariel-os
+[target.'cfg(getrandom_backend = "ariel-os")'.dependencies]
+ariel-os-random = { git = "https://github.com/ariel-os/ariel-os.git", tag = "v0.2.1", features = ["csprng"] }
+rand = { version = "0.8.5", default-features = false }
+
 [lints.rust.unexpected_cfgs]
 level = "warn"
 check-cfg = [
-  'cfg(getrandom_backend, values("custom", "efi_rng", "rdrand", "rndr", "linux_getrandom", "linux_raw", "wasm_js", "unsupported"))',
+  'cfg(getrandom_backend, values("custom", "efi_rng", "rdrand", "rndr", "linux_getrandom", "linux_raw", "wasm_js", "ariel-os", "unsupported"))',
   'cfg(getrandom_msan)',
   'cfg(getrandom_windows_legacy)',
   'cfg(getrandom_test_linux_fallback)',

README.md

@@ -78,16 +78,17 @@ Pull Requests that add support for new targets to `getrandom` are always welcome
 `getrandom` also provides optional (opt-in) backends, which allow users to customize the source
 of randomness based on their specific needs:
 
-| 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_raw`       | Linux, Android       | `*‑linux‑*`              | Same as `linux_getrandom`, but uses raw `asm!`-based syscalls instead of `libc`.
-| `rdrand`          | x86, x86-64          | `x86_64-*`, `i686-*`     | [`RDRAND`] instruction
-| `rndr`            | AArch64              | `aarch64-*`              | [`RNDR`] register
+| 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_raw`       | Linux, Android       | `*‑linux‑*`                               | Same as `linux_getrandom`, but uses raw `asm!`-based syscalls instead of `libc`.
+| `rdrand`          | x86, x86-64          | `x86_64-*`, `i686-*`                      | [`RDRAND`] instruction
+| `rndr`            | AArch64              | `aarch64-*`                               | [`RNDR`] register
 | `wasm_js`         | Web Browser, Node.js | `wasm32‑unknown‑unknown`, `wasm32v1-none` | [`Crypto.getRandomValues`]. Requires feature `wasm_js` ([see below](#webassembly-support)).
-| `efi_rng`         | UEFI                 | `*-unknown‑uefi`         | [`EFI_RNG_PROTOCOL`] with `EFI_RNG_ALGORITHM_RAW` (requires `std` and Nightly compiler)
-| `custom`          | All targets          | `*`                      | User-provided custom implementation (see [custom backend])
-| `unsupported`     | All targets          | `*`                      | Always returns `Err(Error::UNSUPPORTED)` (see [unsupported backend])
+| `efi_rng`         | UEFI                 | `*-unknown‑uefi`                          | [`EFI_RNG_PROTOCOL`] with `EFI_RNG_ALGORITHM_RAW` (requires `std` and Nightly compiler)
+| `ariel-os`        | Ariel OS             |                                           | Ariel OS's built-in entropy source (see [Ariel OS documentation](https://ariel-os.org/docs/development/getting-random-numbers/))
+| `custom`          | All targets          | `*`                                       | User-provided custom implementation (see [custom backend])
+| `unsupported`     | All targets          | `*`                                       | Always returns `Err(Error::UNSUPPORTED)` (see [unsupported backend])
 
 Opt-in backends can be enabled using the `getrandom_backend` configuration flag.
 The flag can be set either by specifying the `rustflags` field in [`.cargo/config.toml`]:

src/backends.rs

@@ -190,6 +190,9 @@ cfg_if! {
             For more information see: \
             https://docs.rs/getrandom/", env!("CARGO_PKG_VERSION"), "/#webassembly-support"
         ));
+    } else if #[cfg(getrandom_backend = "ariel-os")] {
+        mod ariel_os;
+        pub use ariel_os::*;
     } else {
         compile_error!(concat!(
             "target is not supported. You may need to define a custom backend see: \

src/backends/ariel_os.rs

@@ -0,0 +1,14 @@
+//! Implementation for Ariel OS
+use crate::Error;
+use core::mem::MaybeUninit;
+use rand::RngCore;
+
+pub use crate::util::{inner_u32, inner_u64};
+
+pub fn fill_inner(_dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
+    let mut rng = ariel_os_random::crypto_rng();
+    let buf: &mut [u8] =
+        unsafe { core::slice::from_raw_parts_mut(_dest.as_mut_ptr().cast::<u8>(), _dest.len()) };
+    rng.try_fill_bytes(buf)
+        .map_err(|e| Error::from_neg_error_code(e.raw_os_error().unwrap()))
+}