1 files changed, 36 insertions, 0 deletions
diff --git a/third_party/rust/getrandom/src/macos.rs b/third_party/rust/getrandom/src/macos.rs
new file mode 100644
index 0000000000..312f9b27f0
--- /dev/null
+++ b/third_party/rust/getrandom/src/macos.rs
@@ -0,0 +1,36 @@
+// Copyright 2019 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 macOS
+use crate::{
+    use_file,
+    util_libc::{last_os_error, Weak},
+    Error,
+};
+use core::mem::{self, MaybeUninit};
+
+type GetEntropyFn = unsafe extern "C" fn(*mut u8, libc::size_t) -> libc::c_int;
+
+pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
+    // getentropy(2) was added in 10.12, Rust supports 10.7+
+    static GETENTROPY: Weak = unsafe { Weak::new("getentropy\0") };
+    if let Some(fptr) = GETENTROPY.ptr() {
+        let func: GetEntropyFn = unsafe { mem::transmute(fptr) };
+        for chunk in dest.chunks_mut(256) {
+            let ret = unsafe { func(chunk.as_mut_ptr() as *mut u8, chunk.len()) };
+            if ret != 0 {
+                return Err(last_os_error());
+            }
+        }
+        Ok(())
+    } else {
+        // We fallback to reading from /dev/random instead of SecRandomCopyBytes
+        // to avoid high startup costs and linking the Security framework.
+        use_file::getrandom_inner(dest)
+    }
+}