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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 09:22:09 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 09:22:09 +0000 |
commit | 43a97878ce14b72f0981164f87f2e35e14151312 (patch) | |
tree | 620249daf56c0258faa40cbdcf9cfba06de2a846 /third_party/rust/getrandom/src/rdrand.rs | |
parent | Initial commit. (diff) | |
download | firefox-upstream.tar.xz firefox-upstream.zip |
Adding upstream version 110.0.1.upstream/110.0.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/rust/getrandom/src/rdrand.rs')
-rw-r--r-- | third_party/rust/getrandom/src/rdrand.rs | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/third_party/rust/getrandom/src/rdrand.rs b/third_party/rust/getrandom/src/rdrand.rs new file mode 100644 index 0000000000..1df21e5d9d --- /dev/null +++ b/third_party/rust/getrandom/src/rdrand.rs @@ -0,0 +1,97 @@ +// Copyright 2018 Developers of the Rand project. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +//! Implementation for SGX using RDRAND instruction +use crate::Error; +use core::mem; + +cfg_if! { + if #[cfg(target_arch = "x86_64")] { + use core::arch::x86_64 as arch; + use arch::_rdrand64_step as rdrand_step; + } else if #[cfg(target_arch = "x86")] { + use core::arch::x86 as arch; + use arch::_rdrand32_step as rdrand_step; + } +} + +// Recommendation from "Intel® Digital Random Number Generator (DRNG) Software +// Implementation Guide" - Section 5.2.1 and "Intel® 64 and IA-32 Architectures +// Software Developer’s Manual" - Volume 1 - Section 7.3.17.1. +const RETRY_LIMIT: usize = 10; +const WORD_SIZE: usize = mem::size_of::<usize>(); + +#[target_feature(enable = "rdrand")] +unsafe fn rdrand() -> Result<[u8; WORD_SIZE], Error> { + for _ in 0..RETRY_LIMIT { + let mut el = mem::zeroed(); + if rdrand_step(&mut el) == 1 { + // AMD CPUs from families 14h to 16h (pre Ryzen) sometimes fail to + // set CF on bogus random data, so we check these values explicitly. + // See https://github.com/systemd/systemd/issues/11810#issuecomment-489727505 + // We perform this check regardless of target to guard against + // any implementation that incorrectly fails to set CF. + if el != 0 && el != !0 { + return Ok(el.to_ne_bytes()); + } + // Keep looping in case this was a false positive. + } + } + Err(Error::FAILED_RDRAND) +} + +// "rdrand" target feature requires "+rdrnd" flag, see https://github.com/rust-lang/rust/issues/49653. +#[cfg(all(target_env = "sgx", not(target_feature = "rdrand")))] +compile_error!( + "SGX targets require 'rdrand' target feature. Enable by using -C target-feature=+rdrnd." +); + +#[cfg(target_feature = "rdrand")] +fn is_rdrand_supported() -> bool { + true +} + +// TODO use is_x86_feature_detected!("rdrand") when that works in core. See: +// https://github.com/rust-lang-nursery/stdsimd/issues/464 +#[cfg(not(target_feature = "rdrand"))] +fn is_rdrand_supported() -> bool { + use crate::util::LazyBool; + + // SAFETY: All Rust x86 targets are new enough to have CPUID, and if CPUID + // is supported, CPUID leaf 1 is always supported. + const FLAG: u32 = 1 << 30; + static HAS_RDRAND: LazyBool = LazyBool::new(); + HAS_RDRAND.unsync_init(|| unsafe { (arch::__cpuid(1).ecx & FLAG) != 0 }) +} + +pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> { + if !is_rdrand_supported() { + return Err(Error::NO_RDRAND); + } + + // SAFETY: After this point, rdrand is supported, so calling the rdrand + // functions is not undefined behavior. + unsafe { rdrand_exact(dest) } +} + +#[target_feature(enable = "rdrand")] +unsafe fn rdrand_exact(dest: &mut [u8]) -> Result<(), Error> { + // We use chunks_exact_mut instead of chunks_mut as it allows almost all + // calls to memcpy to be elided by the compiler. + let mut chunks = dest.chunks_exact_mut(WORD_SIZE); + for chunk in chunks.by_ref() { + chunk.copy_from_slice(&rdrand()?); + } + + let tail = chunks.into_remainder(); + let n = tail.len(); + if n > 0 { + tail.copy_from_slice(&rdrand()?[..n]); + } + Ok(()) +} |