1 files changed, 24 insertions, 0 deletions
diff --git a/src/apple-other.rs b/src/apple-other.rs
new file mode 100644
index 0000000..167d8cf
--- /dev/null
+++ b/src/apple-other.rs
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+//! Implementation for iOS, tvOS, and watchOS where `getentropy` is unavailable.
+use crate::Error;
+use core::{ffi::c_void, mem::MaybeUninit};
+
+// libsystem contains the libc of Darwin, and every binary ends up linked against it either way. This
+// makes it a more lightweight choice compared to `Security.framework`.
+extern "C" {
+    // This RNG uses a thread-local CSPRNG to provide data, which is seeded by the operating system's root CSPRNG.
+    // Its the best option after `getentropy` on modern Darwin-based platforms that also avoids the
+    // high startup costs and linking of Security.framework.
+    //
+    // While its just an implementation detail, `Security.framework` just calls into this anyway.
+    fn CCRandomGenerateBytes(bytes: *mut c_void, size: usize) -> i32;
+}
+
+pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
+    let ret = unsafe { CCRandomGenerateBytes(dest.as_mut_ptr() as *mut c_void, dest.len()) };
+    // kCCSuccess (from CommonCryptoError.h) is always zero.
+    if ret != 0 {
+        Err(Error::IOS_SEC_RANDOM)
+    } else {
+        Ok(())
+    }
+}