Add AES support for RISC-V: RV64 scalar

Author: silvanshade

.github/workflows/aes.yml

@@ -310,6 +310,35 @@ jobs:
       - run: cross test --package aes --target ${{ matrix.target }} --features hazmat
       - run: cross test --package aes --target ${{ matrix.target }} --all-features
 
+  riscv:
+    strategy:
+      matrix:
+        include:
+          - target: riscv64gc-unknown-linux-gnu
+            rustflags: ''
+            rust: stable
+          - target: riscv64gc-unknown-linux-gnu
+            rustflags: ''
+            rust: nightly
+          - target: riscv64gc-unknown-linux-gnu
+            rustflags: '-Ctarget-feature=+zkne,+zknd'
+            rust: nightly
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: .
+    steps:
+      - uses: actions/checkout@v4
+      - uses: RustCrypto/actions/cargo-cache@master
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+          targets: ${{ matrix.target }}
+      - uses: RustCrypto/actions/cross-install@master
+      - run: cross test --package aes --target ${{ matrix.target }}
+        env:
+          RUSTFLAGS: "-Dwarning ${{ matrix.rustflags }}"
+
   clippy:
     env:
       RUSTFLAGS: "-Dwarnings --cfg aes_compact"

aes/Cargo.toml

@@ -31,7 +31,13 @@ hazmat = [] # Expose cryptographically hazardous APIs
 
 [lints.rust.unexpected_cfgs]
 level = "warn"
-check-cfg = ["cfg(aes_compact)", "cfg(aes_force_soft)", "cfg(aes_avx256_disable)", "cfg(aes_avx512_disable)"]
+check-cfg = [
+    "cfg(aes_compact)",
+    "cfg(aes_force_soft)",
+    "cfg(aes_avx256_disable)",
+    "cfg(aes_avx512_disable)",
+    "cfg(aes_riscv_zkned)",
+]
 
 [package.metadata.docs.rs]
 all-features = true

aes/src/lib.rs

@@ -35,6 +35,13 @@
 //! runtime. On other platforms the `aes` target feature must be enabled via
 //! RUSTFLAGS.
 //!
+//! ## RISC-V rv64 (scalar) {Zkne, ZKnd} extensions
+//!
+//! Support is available for the RISC-V rv64 scalar crypto extensions for AES. This
+//! is not currently autodetected at runtime. In order to enable, you need to
+//! enable the appropriate target features at compile time. For example:
+//! `RUSTFLAGS=-C target-feature=+zkne,+zknd`.
+//!
 //! ## `x86`/`x86_64` intrinsics (AES-NI and VAES)
 //! By default this crate uses runtime detection on `i686`/`x86_64` targets
 //! in order to determine if AES-NI and VAES are available, and if they are
@@ -123,6 +130,7 @@
 )]
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 #![warn(missing_docs, rust_2018_idioms)]
+#![cfg_attr(aes_riscv_zkned, feature(riscv_ext_intrinsics))]
 
 #[cfg(feature = "hazmat")]
 pub mod hazmat;
@@ -137,6 +145,10 @@ cfg_if! {
         mod armv8;
         mod autodetect;
         pub use autodetect::*;
+        mod soft;
+    } else if #[cfg(all(target_arch = "riscv64", aes_riscv_zkned))] {
+        mod riscv;
+        pub use riscv::rv64::*;
     } else if #[cfg(all(
         any(target_arch = "x86", target_arch = "x86_64"),
         not(aes_force_soft)

aes/src/riscv.rs

@@ -0,0 +1,23 @@
+//! AES block cipher implementations for RISC-V using the Cryptography
+//! Extensions
+//!
+//! Supported targets: rv64 (scalar)
+//!
+//! NOTE: rv32 (scalar) is not currently implemented, primarily due to the
+//! difficulty in obtaining a suitable development environment (lack of distro
+//! support and lack of precompiled toolchains), the effort required for
+//! maintaining a test environment as 32-bit becomes less supported, and the
+//! overall scarcity of relevant hardware. If someone has a specific need for
+//! such an implementation, please open an issue.
+//!
+//! NOTE: These implementations are currently not enabled through
+//! auto-detection. In order to use this implementation, you must enable the
+//! appropriate target-features.
+//!
+//! Examining the module structure for this implementation should give you an
+//! idea of how to specify these features in your own code.
+//!
+//! NOTE: AES-128, AES-192, and AES-256 are supported.
+
+#[cfg(all(target_arch = "riscv64", aes_riscv_zkned))]
+pub(crate) mod rv64;