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Rollup merge of #108060 - ChrisDenton:rtlgenrandom, r=thomcc
Revert to using `RtlGenRandom` as a fallback This is required due to `BCryptGenRandom` failing to load a dll it depends on. Fixes #108059
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,106 +1,39 @@ | ||
| //! # Random key generation | ||
| //! | ||
| //! This module wraps the RNG provided by the OS. There are a few different | ||
| //! ways to interface with the OS RNG so it's worth exploring each of the options. | ||
| //! Note that at the time of writing these all go through the (undocumented) | ||
| //! `bcryptPrimitives.dll` but they use different route to get there. | ||
| //! | ||
| //! Originally we were using [`RtlGenRandom`], however that function is | ||
| //! deprecated and warns it "may be altered or unavailable in subsequent versions". | ||
| //! | ||
| //! So we switched to [`BCryptGenRandom`] with the `BCRYPT_USE_SYSTEM_PREFERRED_RNG` | ||
| //! flag to query and find the system configured RNG. However, this change caused a small | ||
| //! but significant number of users to experience panics caused by a failure of | ||
| //! this function. See [#94098]. | ||
| //! | ||
| //! The current version falls back to using `BCryptOpenAlgorithmProvider` if | ||
| //! `BCRYPT_USE_SYSTEM_PREFERRED_RNG` fails for any reason. | ||
| //! | ||
| //! [#94098]: https://github.com/rust-lang/rust/issues/94098 | ||
| //! [`RtlGenRandom`]: https://docs.microsoft.com/en-us/windows/win32/api/ntsecapi/nf-ntsecapi-rtlgenrandom | ||
| //! [`BCryptGenRandom`]: https://docs.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptgenrandom | ||
| use crate::io; | ||
| use crate::mem; | ||
| use crate::ptr; | ||
| use crate::sys::c; | ||
|
|
||
| /// Generates high quality secure random keys for use by [`HashMap`]. | ||
| /// | ||
| /// This is used to seed the default [`RandomState`]. | ||
| /// | ||
| /// [`HashMap`]: crate::collections::HashMap | ||
| /// [`RandomState`]: crate::collections::hash_map::RandomState | ||
| pub fn hashmap_random_keys() -> (u64, u64) { | ||
| Rng::SYSTEM.gen_random_keys().unwrap_or_else(fallback_rng) | ||
| let mut v = (0, 0); | ||
| let ret = unsafe { | ||
| c::BCryptGenRandom( | ||
| ptr::null_mut(), | ||
| &mut v as *mut _ as *mut u8, | ||
| mem::size_of_val(&v) as c::ULONG, | ||
| c::BCRYPT_USE_SYSTEM_PREFERRED_RNG, | ||
| ) | ||
| }; | ||
| if c::nt_success(ret) { v } else { fallback_rng() } | ||
| } | ||
|
|
||
| struct Rng { | ||
| algorithm: c::BCRYPT_ALG_HANDLE, | ||
| flags: u32, | ||
| } | ||
| impl Rng { | ||
| const SYSTEM: Self = unsafe { Self::new(ptr::null_mut(), c::BCRYPT_USE_SYSTEM_PREFERRED_RNG) }; | ||
|
|
||
| /// Create the RNG from an existing algorithm handle. | ||
| /// | ||
| /// # Safety | ||
| /// | ||
| /// The handle must either be null or a valid algorithm handle. | ||
| const unsafe fn new(algorithm: c::BCRYPT_ALG_HANDLE, flags: u32) -> Self { | ||
| Self { algorithm, flags } | ||
| } | ||
|
|
||
| /// Open a handle to the RNG algorithm. | ||
| fn open() -> Result<Self, c::NTSTATUS> { | ||
| use crate::sync::atomic::AtomicPtr; | ||
| use crate::sync::atomic::Ordering::{Acquire, Release}; | ||
|
|
||
| // An atomic is used so we don't need to reopen the handle every time. | ||
| static HANDLE: AtomicPtr<crate::ffi::c_void> = AtomicPtr::new(ptr::null_mut()); | ||
|
|
||
| let mut handle = HANDLE.load(Acquire); | ||
| if handle.is_null() { | ||
| let status = unsafe { | ||
| c::BCryptOpenAlgorithmProvider( | ||
| &mut handle, | ||
| c::BCRYPT_RNG_ALGORITHM.as_ptr(), | ||
| ptr::null(), | ||
| 0, | ||
| ) | ||
| }; | ||
| if c::nt_success(status) { | ||
| // If another thread opens a handle first then use that handle instead. | ||
| let result = HANDLE.compare_exchange(ptr::null_mut(), handle, Release, Acquire); | ||
| if let Err(previous_handle) = result { | ||
| // Close our handle and return the previous one. | ||
| unsafe { c::BCryptCloseAlgorithmProvider(handle, 0) }; | ||
| handle = previous_handle; | ||
| } | ||
| Ok(unsafe { Self::new(handle, 0) }) | ||
| } else { | ||
| Err(status) | ||
| } | ||
| } else { | ||
| Ok(unsafe { Self::new(handle, 0) }) | ||
| } | ||
| } | ||
| /// Generate random numbers using the fallback RNG function (RtlGenRandom) | ||
| /// | ||
| /// This is necessary because of a failure to load the SysWOW64 variant of the | ||
| /// bcryptprimitives.dll library from code that lives in bcrypt.dll | ||
| /// See <https://bugzilla.mozilla.org/show_bug.cgi?id=1788004#c9> | ||
| #[cfg(not(target_vendor = "uwp"))] | ||
| #[inline(never)] | ||
| fn fallback_rng() -> (u64, u64) { | ||
| let mut v = (0, 0); | ||
| let ret = | ||
| unsafe { c::RtlGenRandom(&mut v as *mut _ as *mut u8, mem::size_of_val(&v) as c::ULONG) }; | ||
|
|
||
| fn gen_random_keys(self) -> Result<(u64, u64), c::NTSTATUS> { | ||
| let mut v = (0, 0); | ||
| let status = unsafe { | ||
| let size = mem::size_of_val(&v).try_into().unwrap(); | ||
| c::BCryptGenRandom(self.algorithm, ptr::addr_of_mut!(v).cast(), size, self.flags) | ||
| }; | ||
| if c::nt_success(status) { Ok(v) } else { Err(status) } | ||
| } | ||
| if ret != 0 { v } else { panic!("fallback RNG broken: {}", io::Error::last_os_error()) } | ||
| } | ||
|
|
||
| /// Generate random numbers using the fallback RNG function | ||
| /// We can't use RtlGenRandom with UWP, so there is no fallback | ||
| #[cfg(target_vendor = "uwp")] | ||
| #[inline(never)] | ||
| fn fallback_rng(rng_status: c::NTSTATUS) -> (u64, u64) { | ||
| match Rng::open().and_then(|rng| rng.gen_random_keys()) { | ||
| Ok(keys) => keys, | ||
| Err(status) => { | ||
| panic!("RNG broken: {rng_status:#x}, fallback RNG broken: {status:#x}") | ||
| } | ||
| } | ||
| fn fallback_rng() -> (u64, u64) { | ||
| panic!("fallback RNG broken: RtlGenRandom() not supported on UWP"); | ||
| } |