Implement safe API for RIPEMD-160

CHANGELOG.md

@@ -15,6 +15,7 @@
   - Added missing pattern for only including context and vm config to `testing_env!` to remove friction
 - Added `_array` suffix versions of `sha256`, `keccak256`, and `keccak512` hash functions in `env` [PR 646](https://github.com/near/near-sdk-rs/pull/646)
   - These return a fixed length array instead of heap allocating with `Vec<u8>`
+- Added `ripemd160_array` hash function that returns a fixed length byte array [PR 648](https://github.com/near/near-sdk-rs/pull/648)
 
 ## `4.0.0-pre.4` [10-15-2021]
 - Unpin `syn` dependency in macros from `=1.0.57` to be more composable with other crates. [PR 605](https://github.com/near/near-sdk-rs/pull/605)

near-sdk/src/environment/env.rs

@@ -54,6 +54,12 @@ macro_rules! method_into_register {
 //* Note: need specific length functions because const generics don't work with mem::transmute
 //* https://github.com/rust-lang/rust/issues/61956
 
+pub(crate) unsafe fn read_register_fixed_20(register_id: u64) -> [u8; 20] {
+    let mut hash = [MaybeUninit::<u8>::uninit(); 20];
+    sys::read_register(register_id, hash.as_mut_ptr() as _);
+    std::mem::transmute(hash)
+}
+
 pub(crate) unsafe fn read_register_fixed_32(register_id: u64) -> [u8; 32] {
     let mut hash = [MaybeUninit::<u8>::uninit(); 32];
     sys::read_register(register_id, hash.as_mut_ptr() as _);
@@ -279,6 +285,17 @@ pub fn keccak512_array(value: &[u8]) -> [u8; 64] {
     }
 }
 
+/// Hashes the bytes using the RIPEMD-160 hash function. This returns a 20 byte hash.
+pub fn ripemd160_array(value: &[u8]) -> [u8; 20] {
+    //* SAFETY: ripemd160 syscall will always generate 20 bytes inside of the atomic op register
+    //*         so the read will have a sufficient buffer of 20, and can transmute from uninit
+    //*         because all bytes are filled. This assumes a valid ripemd160 implementation.
+    unsafe {
+        sys::ripemd160(value.len() as _, value.as_ptr() as _, ATOMIC_OP_REGISTER);
+        read_register_fixed_20(ATOMIC_OP_REGISTER)
+    }
+}
+
 // ################
 // # Promises API #
 // ################
@@ -789,5 +806,10 @@ mod tests {
             .unwrap()
             .as_slice()
         );
+
+        assert_eq!(
+            &super::ripemd160_array(b"some value"),
+            base64::decode("CfAl/tcE4eysj4iyvaPlaHbaA6w=").unwrap().as_slice()
+        );
     }
 }

near-sdk/src/environment/mock/mocked_blockchain.rs

@@ -191,6 +191,10 @@ mod mock_chain {
         with_mock_interface(|b| b.keccak512(value_len, value_ptr, register_id))
     }
     #[no_mangle]
+    extern "C" fn ripemd160(value_len: u64, value_ptr: u64, register_id: u64) {
+        with_mock_interface(|b| b.ripemd160(value_len, value_ptr, register_id))
+    }
+    #[no_mangle]
     extern "C" fn value_return(value_len: u64, value_ptr: u64) {
         with_mock_interface(|b| b.value_return(value_len, value_ptr))
     }