1 files changed, 68 insertions, 0 deletions
diff --git a/third_party/rust/fuchsia-zircon/src/cprng.rs b/third_party/rust/fuchsia-zircon/src/cprng.rs
new file mode 100644
index 0000000000..433ed26d9e
--- /dev/null
+++ b/third_party/rust/fuchsia-zircon/src/cprng.rs
@@ -0,0 +1,68 @@
+use {Status, ok, sys};
+
+/// Draw random bytes from the kernel's CPRNG to fill the given buffer. Returns the actual number of
+/// bytes drawn, which may sometimes be less than the size of the buffer provided.
+///
+/// The buffer must have length less than `ZX_CPRNG_DRAW_MAX_LEN`.
+///
+/// Wraps the
+/// [zx_cprng_draw](https://fuchsia.googlesource.com/zircon/+/HEAD/docs/syscalls/cprng_draw.md)
+/// syscall.
+pub fn cprng_draw(buffer: &mut [u8]) -> Result<usize, Status> {
+    let mut actual = 0;
+    let status = unsafe { sys::zx_cprng_draw(buffer.as_mut_ptr(), buffer.len(), &mut actual) };
+    ok(status).map(|()| actual)
+}
+
+/// Mix the given entropy into the kernel CPRNG.
+///
+/// The buffer must have length less than `ZX_CPRNG_ADD_ENTROPY_MAX_LEN`.
+///
+/// Wraps the
+/// [zx_cprng_add_entropy](https://fuchsia.googlesource.com/zircon/+/HEAD/docs/syscalls/cprng_add_entropy.md)
+/// syscall.
+pub fn cprng_add_entropy(buffer: &[u8]) -> Result<(), Status> {
+    let status = unsafe { sys::zx_cprng_add_entropy(buffer.as_ptr(), buffer.len()) };
+    ok(status)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn cprng() {
+        let mut buffer = [0; 20];
+        assert_eq!(cprng_draw(&mut buffer), Ok(20));
+        let mut first_zero = 0;
+        let mut last_zero = 0;
+        for _ in 0..30 {
+            let mut buffer = [0; 20];
+            assert_eq!(cprng_draw(&mut buffer), Ok(20));
+            if buffer[0] == 0 {
+                first_zero += 1;
+            }
+            if buffer[19] == 0 {
+                last_zero += 1;
+            }
+        }
+        assert_ne!(first_zero, 30);
+        assert_ne!(last_zero, 30);
+    }
+
+    #[test]
+    fn cprng_too_large() {
+        let mut buffer = [0; sys::ZX_CPRNG_DRAW_MAX_LEN + 1];
+        assert_eq!(cprng_draw(&mut buffer), Err(Status::INVALID_ARGS));
+
+        for mut s in buffer.chunks_mut(sys::ZX_CPRNG_DRAW_MAX_LEN) {
+            assert_eq!(cprng_draw(&mut s), Ok(s.len()));
+        }
+    }
+
+    #[test]
+    fn cprng_add() {
+        let buffer = [0, 1, 2];
+        assert_eq!(cprng_add_entropy(&buffer), Ok(()));
+    }
+}
+\ No newline at end of file