Upgrade getrandom to 0.2.12 am: 1872b3e122emu-34-2-dev

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/getrandom/+/2944786

Change-Id: I315dfe2e9f343a483e0a525f8f29e2a53fc9e8f7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

1 files changed, 21 insertions, 11 deletions

diff --git a/src/windows.rs b/src/windows.rs
index 41dc37a..2d1c483 100644
--- a/src/windows.rs
+++ b/src/windows.rs
@@ -1,13 +1,6 @@
-// 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 Windows
 use crate::Error;
-use core::{ffi::c_void, num::NonZeroU32, ptr};
+use core::{ffi::c_void, mem::MaybeUninit, num::NonZeroU32, ptr};
 
 const BCRYPT_USE_SYSTEM_PREFERRED_RNG: u32 = 0x00000002;
 
@@ -21,20 +14,37 @@ extern "system" {
     ) -> u32;
 }
 
-pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
+// Forbidden when targetting UWP
+#[cfg(not(target_vendor = "uwp"))]
+#[link(name = "advapi32")]
+extern "system" {
+    #[link_name = "SystemFunction036"]
+    fn RtlGenRandom(RandomBuffer: *mut c_void, RandomBufferLength: u32) -> u8;
+}
+
+pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
     // Prevent overflow of u32
     for chunk in dest.chunks_mut(u32::max_value() as usize) {
         // BCryptGenRandom was introduced in Windows Vista
         let ret = unsafe {
             BCryptGenRandom(
                 ptr::null_mut(),
-                chunk.as_mut_ptr(),
+                chunk.as_mut_ptr() as *mut u8,
                 chunk.len() as u32,
                 BCRYPT_USE_SYSTEM_PREFERRED_RNG,
             )
         };
         // NTSTATUS codes use the two highest bits for severity status.
         if ret >> 30 == 0b11 {
+            // Failed. Try RtlGenRandom as a fallback.
+            #[cfg(not(target_vendor = "uwp"))]
+            {
+                let ret =
+                    unsafe { RtlGenRandom(chunk.as_mut_ptr() as *mut c_void, chunk.len() as u32) };
+                if ret != 0 {
+                    continue;
+                }
+            }
             // We zeroize the highest bit, so the error code will reside
             // inside the range designated for OS codes.
             let code = ret ^ (1 << 31);