fixed endian issue for the rng regarding #447

Author: nstilt1

chacha20/src/backends/soft.rs

@@ -11,6 +11,9 @@ use cipher::{
     consts::{U1, U64},
 };
 
+#[cfg(feature = "rng")]
+use crate::rng::BLOCK_WORDS;
+
 pub(crate) struct Backend<'a, R: Rounds, V: Variant>(pub(crate) &'a mut ChaChaCore<R, V>);
 
 #[cfg(feature = "cipher")]
@@ -45,16 +48,15 @@ impl<R: Rounds, V: Variant> StreamCipherBackend for Backend<'_, R, V> {
 impl<R: Rounds, V: Variant> Backend<'_, R, V> {
     #[inline(always)]
     pub(crate) fn gen_ks_blocks(&mut self, buffer: &mut [u32; 64]) {
-        for i in 0..4 {
+        for block in 0..4 {
             let res = run_rounds::<R>(&self.0.state);
             let mut ctr = u64::from(self.0.state[13]) << 32 | u64::from(self.0.state[12]);
             ctr = ctr.wrapping_add(1);
             self.0.state[12] = ctr as u32;
             self.0.state[13] = (ctr >> 32) as u32;
 
-            for (word, val) in buffer[i << 4..(i + 1) << 4].iter_mut().zip(res.iter()) {
-                *word = val.to_le();
-            }
+            buffer[block * BLOCK_WORDS as usize..(block + 1) * BLOCK_WORDS as usize]
+                .copy_from_slice(&res);
         }
     }
 }

chacha20/src/rng.rs

@@ -27,7 +27,7 @@ use crate::{
 use cfg_if::cfg_if;
 
 /// Number of 32-bit words per ChaCha block (fixed by algorithm definition).
-const BLOCK_WORDS: u8 = 16;
+pub(crate) const BLOCK_WORDS: u8 = 16;
 
 /// The seed for ChaCha20. Implements ZeroizeOnDrop when the
 /// zeroize feature is enabled.
@@ -590,10 +590,6 @@ macro_rules! impl_chacha_rng {
             #[inline]
             fn generate(&mut self, r: &mut Self::Results) {
                 self.0.generate(&mut r.0);
-                #[cfg(target_endian = "big")]
-                for word in r.0.iter_mut() {
-                    *word = word.to_le();
-                }
             }
         }
     };