From 4be67893ccece4823b606c5e29eccd44f7e07450 Mon Sep 17 00:00:00 2001 From: Tony Arcieri Date: Thu, 5 Sep 2024 20:56:09 -0600 Subject: [PATCH] aarch64-dit: initial crate (#1102) Adds a crate with wrappers for the Data-Independent Timing (DIT) feature of AArch64 CPUs. The implementation is largely a translation of Apple's guide of how to write wrappers for enabling/disabling DIT: https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms#Enable-DIT-for-constant-time-cryptographic-operations It would be nice to wrap that all up into an RAII guard which can first use `cpufeatures` to check for `FEAT_DIT` and, if available, enable it for the current thread, while also first querying the processor status register and restoring the previous state on `Drop`, which is necessary for proper nested usage of DIT. But for now, this just wraps the barebones functionality in an `unsafe` API. --- .github/workflows/aarch64-dit.yml | 37 ++++++ .github/workflows/workspace.yml | 2 +- Cargo.lock | 7 ++ Cargo.toml | 1 + aarch64-dit/CHANGELOG.md | 5 + aarch64-dit/Cargo.toml | 19 +++ aarch64-dit/LICENSE-APACHE | 202 ++++++++++++++++++++++++++++++ aarch64-dit/LICENSE-MIT | 21 ++++ aarch64-dit/README.md | 51 ++++++++ aarch64-dit/src/lib.rs | 68 ++++++++++ 10 files changed, 412 insertions(+), 1 deletion(-) create mode 100644 .github/workflows/aarch64-dit.yml create mode 100644 aarch64-dit/CHANGELOG.md create mode 100644 aarch64-dit/Cargo.toml create mode 100644 aarch64-dit/LICENSE-APACHE create mode 100644 aarch64-dit/LICENSE-MIT create mode 100644 aarch64-dit/README.md create mode 100644 aarch64-dit/src/lib.rs diff --git a/.github/workflows/aarch64-dit.yml b/.github/workflows/aarch64-dit.yml new file mode 100644 index 00000000..c01a02fd --- /dev/null +++ b/.github/workflows/aarch64-dit.yml @@ -0,0 +1,37 @@ +name: aarch64-dit + +on: + pull_request: + paths: + - "aarch64-dit/**" + - "Cargo.*" + push: + branches: master + +permissions: + contents: read + +defaults: + run: + working-directory: aarch64-dit + +env: + CARGO_INCREMENTAL: 0 + RUSTFLAGS: "-Dwarnings" + +jobs: + macos: + strategy: + matrix: + toolchain: + - 1.61.0 # MSRV + - stable + runs-on: macos-latest + steps: + - uses: actions/checkout@v4 + - uses: RustCrypto/actions/cargo-cache@master + - uses: dtolnay/rust-toolchain@master + with: + toolchain: ${{ matrix.toolchain }} + targets: aarch64-apple-darwin + - run: cargo test diff --git a/.github/workflows/workspace.yml b/.github/workflows/workspace.yml index 2d6a07fb..d74c76ce 100644 --- a/.github/workflows/workspace.yml +++ b/.github/workflows/workspace.yml @@ -22,7 +22,7 @@ jobs: with: toolchain: 1.72.0 # Pinned to prevent breakages components: clippy - - run: cargo clippy --all --all-features -- -D warnings + - run: cargo clippy --all --all-features --exclude aarch64-dit -- -D warnings rustfmt: runs-on: ubuntu-latest diff --git a/Cargo.lock b/Cargo.lock index 56a5a30e..d495ca89 100644 --- a/Cargo.lock +++ b/Cargo.lock @@ -2,6 +2,13 @@ # It is not intended for manual editing. version = 3 +[[package]] +name = "aarch64-dit" +version = "0.0.0" +dependencies = [ + "cpufeatures", +] + [[package]] name = "blobby" version = "0.3.1" diff --git a/Cargo.toml b/Cargo.toml index bb5566d7..02f453c4 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -1,6 +1,7 @@ [workspace] resolver = "2" members = [ + "aarch64-dit", "blobby", "block-buffer", "block-padding", diff --git a/aarch64-dit/CHANGELOG.md b/aarch64-dit/CHANGELOG.md new file mode 100644 index 00000000..d6637e04 --- /dev/null +++ b/aarch64-dit/CHANGELOG.md @@ -0,0 +1,5 @@ +# Changelog +All notable changes to this project will be documented in this file. + +The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), +and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html). diff --git a/aarch64-dit/Cargo.toml b/aarch64-dit/Cargo.toml new file mode 100644 index 00000000..c2f43207 --- /dev/null +++ b/aarch64-dit/Cargo.toml @@ -0,0 +1,19 @@ +[package] +name = "aarch64-dit" +description = """ +Wrappers for enabling/disabling the Data Independent Timing (DIT) feature on AArch64 CPUs +""" +version = "0.0.0" +authors = ["RustCrypto Developers"] +license = "Apache-2.0 OR MIT" +homepage = "https://github.com/RustCrypto/utils/tree/master/aarch64-dit" +repository = "https://github.com/RustCrypto/utils" +categories = ["cryptography", "hardware-support", "no-std"] +keywords = ["crypto", "intrinsics"] +readme = "README.md" +edition = "2021" +rust-version = "1.61" + +[dev-dependencies] +# TODO: release `cpufeatures` with `dit` support +cpufeatures = { path = "../cpufeatures" } diff --git a/aarch64-dit/LICENSE-APACHE b/aarch64-dit/LICENSE-APACHE new file mode 100644 index 00000000..d6456956 --- /dev/null +++ b/aarch64-dit/LICENSE-APACHE @@ -0,0 +1,202 @@ + + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + + TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + + 1. 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IN NO EVENT SHALL THE +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +SOFTWARE. diff --git a/aarch64-dit/README.md b/aarch64-dit/README.md new file mode 100644 index 00000000..e882be62 --- /dev/null +++ b/aarch64-dit/README.md @@ -0,0 +1,51 @@ +# [RustCrypto]: AArch64 Data-Independent Timing (DIT) + +[![Crate][crate-image]][crate-link] +[![Docs][docs-image]][docs-link] +[![Build Status][build-image]][build-link] +![Apache 2.0/MIT Licensed][license-image] +![MSRV][msrv-image] + +Wrappers for enabling/disabling the [Data-Independent Timing] feature of modern AArch64 CPUs which +can be used to help ensure that instructions take a constant amount of time regardless of input +data, thus preventing potential information leaks via timing sidechannels. + +[Documentation][docs-link] + +## Minimum Supported Rust Version + +Rust **1.61** or newer. + +In the future, we reserve the right to change MSRV (i.e. MSRV is out-of-scope for this crate's +SemVer guarantees), however when we do it will be accompanied by a minor version bump. + +## License + +Licensed under either of: + +* [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0) +* [MIT license](http://opensource.org/licenses/MIT) + +at your option. + +### Contribution + +Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the +work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any +additional terms or conditions. + +[//]: # (badges) + +[crate-image]: https://img.shields.io/crates/v/aarch64-dit.svg +[crate-link]: https://crates.io/crates/aarch64-dit +[docs-image]: https://docs.rs/aarch64-dit/badge.svg +[docs-link]: https://docs.rs/aarch64-dit/ +[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg +[msrv-image]: https://img.shields.io/badge/rustc-1.61+-blue.svg +[build-image]: https://github.com/RustCrypto/utils/actions/workflows/aarch64-dit.yml/badge.svg +[build-link]: https://github.com/RustCrypto/utils/actions/workflows/aarch64-dit.yml + +[//]: # (links) + +[RustCrypto]: https://github.com/RustCrypto +[Data-Independent Timing]: https://developer.arm.com/documentation/ddi0595/2021-06/AArch64-Registers/DIT--Data-Independent-Timing diff --git a/aarch64-dit/src/lib.rs b/aarch64-dit/src/lib.rs new file mode 100644 index 00000000..2239537e --- /dev/null +++ b/aarch64-dit/src/lib.rs @@ -0,0 +1,68 @@ +#![no_std] +#![doc = include_str!("../README.md")] +#![doc( + html_logo_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg", + html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg" +)] +#![warn(missing_docs, rust_2018_idioms, unused_qualifications)] + +#[cfg(not(target_arch = "aarch64"))] +compile_error!("This crate only builds on `aarch64` targets"); + +use core::arch::asm; + +/// Detect if DIT is enabled for the current thread by checking the processor state register. +#[target_feature(enable = "dit")] +pub unsafe fn get_dit_enabled() -> bool { + let mut dit: u64; + asm!( + "mrs {dit}, DIT", + dit = out(reg) dit, + options(nomem, nostack, preserves_flags) + ); + (dit >> 24) & 1 != 0 +} + +/// Enable DIT for the current thread. +#[target_feature(enable = "dit")] +pub unsafe fn set_dit_enabled() { + asm!("msr DIT, #1", options(nomem, nostack, preserves_flags)); +} + +/// Restore DIT state depending on the enabled bit. +#[target_feature(enable = "dit")] +pub unsafe fn restore_dit(enabled: bool) { + if !enabled { + // Disable DIT + asm!("msr DIT, #0", options(nomem, nostack, preserves_flags)); + } +} + +#[cfg(test)] +mod tests { + use super::{get_dit_enabled, restore_dit, set_dit_enabled}; + cpufeatures::new!(dit_supported, "dit"); + + #[test] + fn get() { + let dit_token = dit_supported::init(); + if !dit_token.get() { + panic!("DIT is not available on this CPU"); + } + + let dit_enabled = unsafe { get_dit_enabled() }; + assert!(!dit_enabled); + + unsafe { set_dit_enabled() }; + let dit_enabled = unsafe { get_dit_enabled() }; + assert!(dit_enabled); + + unsafe { restore_dit(true) }; + let dit_enabled = unsafe { get_dit_enabled() }; + assert!(dit_enabled); + + unsafe { restore_dit(false) }; + let dit_enabled = unsafe { get_dit_enabled() }; + assert!(!dit_enabled); + } +}