Rust wrapper: implement Clone for HMAC types

wrapper/rust/wolfssl-wolfcrypt/src/hmac.rs

@@ -330,6 +330,24 @@ impl HMAC {
     }
 }
 
+impl Clone for HMAC {
+    /// Deep-copy the HMAC state via `wc_HmacCopy()`.
+    ///
+    /// Panics if the underlying wolfSSL copy fails.
+    fn clone(&self) -> Self {
+        let mut wc_hmac: MaybeUninit<sys::Hmac> = MaybeUninit::uninit();
+        let rc = unsafe {
+            sys::wc_HmacCopy(&self.wc_hmac as *const _ as *mut _,
+                wc_hmac.as_mut_ptr())
+        };
+        if rc != 0 {
+            panic!("wc_HmacCopy() failed: {}", rc);
+        }
+        let wc_hmac = unsafe { wc_hmac.assume_init() };
+        HMAC { wc_hmac }
+    }
+}
+
 impl Drop for HMAC {
     /// Safely free the underlying wolfSSL Hmac context.
     ///

wrapper/rust/wolfssl-wolfcrypt/src/hmac_mac.rs

@@ -42,6 +42,7 @@ macro_rules! impl_hmac_mac {
         $name:ident, hmac_type = $hmac_type:expr, key = $key_size:ty, out = $out_size:ty
     ) => {
         $(#[$attr])*
+        #[derive(Clone)]
         pub struct $name {
             hmac: crate::hmac::HMAC,
         }

wrapper/rust/wolfssl-wolfcrypt/tests/test_hmac_mac.rs

@@ -40,6 +40,27 @@ fn test_hmac_sha256_mac_finalize() {
     assert_eq!(result.as_bytes().as_slice(), expected);
 }
 
+#[test]
+fn test_hmac_sha256_mac_clone() {
+    let key = b"\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b";
+    let prefix = b"Hi ";
+    let suffix = b"There";
+    let expected = b"\xb0\x34\x4c\x61\xd8\xdb\x38\x53\x5c\xa8\xaf\xce\xaf\x0b\xf1\x2b\x88\x1d\xc2\x00\xc9\x83\x3d\xa7\x26\xe9\x37\x6c\x2e\x32\xcf\xf7";
+
+    let mut mac = HmacSha256::new_from_slice(key)
+        .expect("HMAC init failed");
+    mac.update(prefix);
+
+    let mut forked = mac.clone();
+    forked.update(suffix);
+    let forked_tag = forked.finalize();
+    assert_eq!(forked_tag.as_bytes().as_slice(), expected);
+
+    mac.update(suffix);
+    let original_tag = mac.finalize();
+    assert_eq!(original_tag.as_bytes().as_slice(), expected);
+}
+
 #[test]
 fn test_hmac_sha256_mac_verify_fail() {
     let key = b"\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b";