Add MSRV build to CI

We were not testing MSRV 1.56.1 before due to a build failure. This
allowed a bit of feature creap which relies on newer versions of
Rust. Luckily, it was a single feature in our unit tests, so easy
to refactor. Now enforcing the MSRV in CI, but this did require us
to use precise versions of memchr and backtrace. Currently controlled
by our lock file.

.github/workflows/ci.yml

@@ -40,9 +40,8 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        # Minumum Supported Rust Version (MSRV) is 1.56.1 but
-        # having some weird issues with the memchr dependency.
-        toolchain: [stable, beta, nightly]
+        # Minumum Supported Rust Version (MSRV) is 1.56.1.
+        toolchain: [1.56.1, stable, beta, nightly]
     steps:
       - uses: actions/checkout@v3
       - name: Update Toolchain
@@ -74,8 +73,10 @@ jobs:
           cargo test --package bip324 --verbose --no-default-features
           cargo test --package bip324 --verbose --no-default-features --features alloc
       - name: Check No Standard Library Support
+        # The cross tool used to test in a no standard library environment doesn't play nice with our MSRV, so limiting to just stable toolchain.
+        if: matrix.toolchain == 'stable'
         run: |
           rustup target add --toolchain ${{ matrix.toolchain }} thumbv7m-none-eabi
-          cargo install cross
+          cargo install cross --locked
           cross build --package bip324 --target thumbv7m-none-eabi --no-default-features --features alloc
         

protocol/src/chacha20poly1305/chacha20.rs

@@ -359,11 +359,10 @@ mod tests {
         let count = 1;
         let mut chacha = ChaCha20::new(key, nonce, count);
         let mut binding = [8; 3];
-        let to = binding.as_mut_slice();
-        chacha.apply_keystream(to).unwrap();
+        chacha.apply_keystream(&mut binding[..]).unwrap();
         let mut chacha = ChaCha20::new(key, nonce, count);
-        chacha.apply_keystream(to).unwrap();
-        assert_eq!([8; 3], to);
+        chacha.apply_keystream(&mut binding[..]).unwrap();
+        assert_eq!([8; 3], binding);
     }
 
     #[test]
@@ -376,11 +375,10 @@ mod tests {
         let count = 1;
         let mut chacha = ChaCha20::new(key, nonce, count);
         let mut binding = [8; 64];
-        let to = binding.as_mut_slice();
-        chacha.apply_keystream(to).unwrap();
+        chacha.apply_keystream(&mut binding[..]).unwrap();
         let mut chacha = ChaCha20::new(key, nonce, count);
-        chacha.apply_keystream(to).unwrap();
-        assert_eq!([8; 64], to);
+        chacha.apply_keystream(&mut binding[..]).unwrap();
+        assert_eq!([8; 64], binding);
     }
 
     #[test]
@@ -393,13 +391,11 @@ mod tests {
         let count = 64;
         let mut chacha = ChaCha20::new(key, nonce, count);
         let mut binding = *b"Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it.";
-        let to = binding.as_mut_slice();
-        chacha.apply_keystream(to).unwrap();
-        assert_eq!(to, Vec::from_hex("6e2e359a2568f98041ba0728dd0d6981e97e7aec1d4360c20a27afccfd9fae0bf91b65c5524733ab8f593dabcd62b3571639d624e65152ab8f530c359f0861d807ca0dbf500d6a6156a38e088a22b65e52bc514d16ccf806818ce91ab77937365af90bbf74a35be6b40b8eedf2785e42874d").unwrap());
+        chacha.apply_keystream(&mut binding[..]).unwrap();
+        assert_eq!(binding[..], Vec::from_hex("6e2e359a2568f98041ba0728dd0d6981e97e7aec1d4360c20a27afccfd9fae0bf91b65c5524733ab8f593dabcd62b3571639d624e65152ab8f530c359f0861d807ca0dbf500d6a6156a38e088a22b65e52bc514d16ccf806818ce91ab77937365af90bbf74a35be6b40b8eedf2785e42874d").unwrap());
         let mut chacha = ChaCha20::new(key, nonce, count);
-        chacha.apply_keystream(to).unwrap();
-        let binding = *b"Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it.";
-        assert_eq!(binding, to);
+        chacha.apply_keystream(&mut binding[..]).unwrap();
+        assert_eq!(binding, *b"Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it.");
     }
 
     #[test]
@@ -412,13 +408,11 @@ mod tests {
         let block: u32 = 1;
         let mut chacha = ChaCha20::new_from_block(key, nonce, block);
         let mut binding = *b"Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it.";
-        let to = binding.as_mut_slice();
-        chacha.apply_keystream(to).unwrap();
-        assert_eq!(to, Vec::from_hex("6e2e359a2568f98041ba0728dd0d6981e97e7aec1d4360c20a27afccfd9fae0bf91b65c5524733ab8f593dabcd62b3571639d624e65152ab8f530c359f0861d807ca0dbf500d6a6156a38e088a22b65e52bc514d16ccf806818ce91ab77937365af90bbf74a35be6b40b8eedf2785e42874d").unwrap());
+        chacha.apply_keystream(&mut binding[..]).unwrap();
+        assert_eq!(binding[..], Vec::from_hex("6e2e359a2568f98041ba0728dd0d6981e97e7aec1d4360c20a27afccfd9fae0bf91b65c5524733ab8f593dabcd62b3571639d624e65152ab8f530c359f0861d807ca0dbf500d6a6156a38e088a22b65e52bc514d16ccf806818ce91ab77937365af90bbf74a35be6b40b8eedf2785e42874d").unwrap());
         chacha.block(block);
-        chacha.apply_keystream(to).unwrap();
-        let binding = *b"Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it.";
-        assert_eq!(binding, to);
+        chacha.apply_keystream(&mut binding[..]).unwrap();
+        assert_eq!(binding, *b"Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it.");
     }
 
     #[cfg(feature = "std")]

protocol/src/lib.rs

@@ -163,7 +163,7 @@ pub struct PacketReader {
 }
 
 impl PacketReader {
-    /// Decode the length, in bytes, of the of the rest imbound message.
+    /// Decode the length, in bytes, of the rest of the inbound message.
     ///
     /// Intended for use with `TcpStream` and `read_exact`. Note that this does not decode to the
     /// length of contents described in BIP324, and is meant to represent the entire imbound message