Made Hash store a byte array, so Node can store a Hash, rather than a byte slice

Cargo.toml

@@ -19,6 +19,7 @@ categories = [
 [dependencies]
 blake2-rfc = "0.2.18"
 byteorder = "1.2.6"
+constant_time_eq = "0.1.3" 
 ed25519-dalek = "0.8.1"
 failure = "0.1.2"
 flat-tree = "4.0.1"

src/crypto/hash.rs

@@ -1,11 +1,14 @@
 pub use blake2_rfc::blake2b::Blake2bResult;
 
+use crate::storage::Node;
 use blake2_rfc::blake2b::Blake2b;
 use byteorder::{BigEndian, WriteBytesExt};
 // use ed25519_dalek::PublicKey;
-use crate::storage::Node;
+use constant_time_eq::constant_time_eq;
 use merkle_tree_stream::Node as NodeTrait;
+use pretty_hash::fmt as pretty_fmt;
 use std::convert::AsRef;
+use std::fmt;
 use std::mem;
 use std::ops::{Deref, DerefMut};
 
@@ -14,53 +17,57 @@ const LEAF_TYPE: [u8; 1] = [0x00];
 const PARENT_TYPE: [u8; 1] = [0x01];
 const ROOT_TYPE: [u8; 1] = [0x02];
 //const HYPERCORE: [u8; 9] = *b"hypercore";
+const BLAKE_2_HASH_SIZE: usize = 32;
 
+type StoredHash = [u8; BLAKE_2_HASH_SIZE];
 /// `BLAKE2b` hash.
-#[derive(Debug, Clone, PartialEq)]
+/// uses [blake2_rfc::blake2b::Blake2bResult] to hash its inputs on initalisation, the calculated
+/// hash is then constant and can not be changed.
+#[derive(Debug, Clone)]
 pub struct Hash {
-  hash: Blake2bResult,
+  hash: StoredHash,
 }
 
 impl Hash {
   /// Hash a `Leaf` node.
   pub fn from_leaf(data: &[u8]) -> Self {
     let size = u64_as_be(data.len() as u64);
 
-    let mut hasher = Blake2b::new(32);
+    let mut hasher = Blake2b::new(BLAKE_2_HASH_SIZE);
     hasher.update(&LEAF_TYPE);
     hasher.update(&size);
     hasher.update(data);
 
     Self {
-      hash: hasher.finalize(),
+      hash: hasher_to_stored_hash(hasher),
     }
   }
 
   /// Hash two `Leaf` nodes hashes together to form a `Parent` hash.
   pub fn from_hashes(left: &Node, right: &Node) -> Self {
-    let (node1, node2) = if left.index <= right.index {
+    let (node1, node2) = if left <= right {
       (left, right)
     } else {
       (right, left)
     };
 
     let size = u64_as_be((node1.length + node2.length) as u64);
 
-    let mut hasher = Blake2b::new(32);
+    let mut hasher = Blake2b::new(BLAKE_2_HASH_SIZE);
     hasher.update(&PARENT_TYPE);
     hasher.update(&size);
     hasher.update(node1.hash());
     hasher.update(node2.hash());
 
     Self {
-      hash: hasher.finalize(),
+      hash: hasher_to_stored_hash(hasher),
     }
   }
 
   // /// Hash a public key. Useful to find the key you're looking for on a public
   // /// network without leaking the key itself.
   // pub fn from_key(public_key: PublicKey) -> Self {
-  //   let mut hasher = Blake2b::new(32);
+  //   let mut hasher = Blake2b::new(BLAKE_2_HASH_SIZE);
   //   hasher.update(*HYPERCORE);
   //   hasher.update(public_key.as_bytes());
   //   Self {
@@ -71,7 +78,7 @@ impl Hash {
   /// Hash a vector of `Root` nodes.
   // Called `crypto.tree()` in the JS implementation.
   pub fn from_roots(roots: &[impl AsRef<Node>]) -> Self {
-    let mut hasher = Blake2b::new(32);
+    let mut hasher = Blake2b::new(BLAKE_2_HASH_SIZE);
     hasher.update(&ROOT_TYPE);
 
     for node in roots {
@@ -82,14 +89,37 @@ impl Hash {
     }
 
     Self {
-      hash: hasher.finalize(),
+      hash: hasher_to_stored_hash(hasher),
+    }
+  }
+
+  pub fn from_bytes(bytes: &[u8]) -> Self {
+    Self {
+      hash: slice_to_stored_hash(bytes),
     }
   }
 
   /// Returns a byte slice of this `Hash`'s contents.
   pub fn as_bytes(&self) -> &[u8] {
-    self.hash.as_bytes()
+    &self.hash[..]
+  }
+}
+
+fn slice_to_stored_hash(slice: &[u8]) -> StoredHash {
+  assert!(slice.len() == BLAKE_2_HASH_SIZE);
+
+  let mut stored_hash: StoredHash = [0; BLAKE_2_HASH_SIZE];
+  let mut i = 0;
+  for byte in slice.iter() {
+    stored_hash[i] = *byte;
+    i = i + 1;
   }
+
+  stored_hash
+}
+
+fn hasher_to_stored_hash(hasher: Blake2b) -> StoredHash {
+  slice_to_stored_hash(hasher.finalize().as_bytes())
 }
 
 fn u64_as_be(n: u64) -> [u8; 8] {
@@ -99,7 +129,7 @@ fn u64_as_be(n: u64) -> [u8; 8] {
 }
 
 impl Deref for Hash {
-  type Target = Blake2bResult;
+  type Target = StoredHash;
 
   fn deref(&self) -> &Self::Target {
     &self.hash
@@ -112,6 +142,20 @@ impl DerefMut for Hash {
   }
 }
 
+impl fmt::Display for Hash {
+  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    write!(f, "{}", pretty_fmt(&self.hash[..]).unwrap())
+  }
+}
+
+impl PartialEq for Hash {
+  fn eq(&self, other: &Self) -> bool {
+    constant_time_eq(&self.hash[..], &other.hash[..])
+  }
+}
+
+impl Eq for Hash {}
+
 #[cfg(test)]
 mod tests {
   use super::*;
@@ -143,8 +187,8 @@ mod tests {
   fn parent_hash() {
     let d1: &[u8] = &[0, 1, 2, 3, 4];
     let d2: &[u8] = &[42, 43, 44, 45, 46, 47, 48];
-    let node1 = Node::new(0, Hash::from_leaf(d1).as_bytes().to_vec(), d1.len());
-    let node2 = Node::new(1, Hash::from_leaf(d2).as_bytes().to_vec(), d2.len());
+    let node1 = Node::new(0, Hash::from_leaf(d1), d1.len());
+    let node2 = Node::new(1, Hash::from_leaf(d2), d2.len());
     check_hash(
       Hash::from_hashes(&node1, &node2),
       "6fac58578fa385f25a54c0637adaca71fdfddcea885d561f33d80c4487149a14",
@@ -159,8 +203,8 @@ mod tests {
   fn root_hash() {
     let d1: &[u8] = &[0, 1, 2, 3, 4];
     let d2: &[u8] = &[42, 43, 44, 45, 46, 47, 48];
-    let node1 = Node::new(0, Hash::from_leaf(d1).as_bytes().to_vec(), d1.len());
-    let node2 = Node::new(1, Hash::from_leaf(d2).as_bytes().to_vec(), d2.len());
+    let node1 = Node::new(0, Hash::from_leaf(d1), d1.len());
+    let node2 = Node::new(1, Hash::from_leaf(d2), d2.len());
     check_hash(
       Hash::from_roots(&[&node1, &node2]),
       "2d117e0bb15c6e5236b6ce764649baed1c41890da901a015341503146cc20bcd",

src/crypto/merkle.rs

@@ -6,9 +6,9 @@ use merkle_tree_stream::{
 use std::rc::Rc;
 
 #[derive(Debug)]
-struct H;
+struct Hasher;
 
-impl HashMethods for H {
+impl HashMethods for Hasher {
   type Node = Node;
   type Hash = Hash;
 
@@ -33,7 +33,7 @@ impl HashMethods for H {
       index: partial.index(),
       parent: partial.parent,
       length: partial.len(),
-      hash: hash.as_bytes().into(),
+      hash: hash,
       data,
     }
   }
@@ -42,7 +42,7 @@ impl HashMethods for H {
 /// Merkle Tree Stream
 #[derive(Debug)]
 pub struct Merkle {
-  stream: MerkleTreeStream<H>,
+  stream: MerkleTreeStream<Hasher>,
   nodes: Vec<Rc<Node>>,
 }
 
@@ -58,7 +58,7 @@ impl Merkle {
   pub fn new() -> Self {
     Self {
       nodes: vec![],
-      stream: MerkleTreeStream::new(H, vec![]),
+      stream: MerkleTreeStream::new(Hasher, vec![]),
     }
   }
 

src/feed.rs

@@ -287,11 +287,9 @@ where
 
     let mut visited = vec![];
     let mut top = match data {
-      Some(data) => Node::new(
-        tree_index(index),
-        Hash::from_leaf(&data).as_bytes().to_owned(),
-        data.len(),
-      ),
+      Some(data) => {
+        Node::new(tree_index(index), Hash::from_leaf(&data), data.len())
+      }
       None => proof.nodes.remove(0),
     };
 
@@ -322,7 +320,7 @@ where
       visited.push(top.clone());
       let hash = Hash::from_hashes(&top, &node);
       let len = top.len() + node.len();
-      top = Node::new(flat::parent(top.index), hash.as_bytes().into(), len);
+      top = Node::new(flat::parent(top.index), hash, len);
 
       if verify_node(&trusted_node, &top) {
         self.write(index, data, &visited, None)?;
@@ -526,7 +524,7 @@ where
         let node = self.storage.get_node(2 * index)?;
         let data = self.storage.get_data(index)?;
         let data_hash = Hash::from_leaf(&data);
-        if node.hash == data_hash.as_bytes() {
+        if node.hash == data_hash {
           valid_blocks += 1;
         } else {
           invalid_blocks += 1;

src/lib.rs

@@ -37,6 +37,7 @@ extern crate failure;
 
 extern crate blake2_rfc;
 extern crate byteorder;
+extern crate constant_time_eq;
 extern crate ed25519_dalek;
 extern crate flat_tree;
 extern crate merkle_tree_stream;

src/storage/node.rs

@@ -1,12 +1,12 @@
+use crate::crypto::Hash;
 use crate::Result;
 use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
 use flat_tree;
 use merkle_tree_stream::Node as NodeTrait;
-use pretty_hash::fmt as pretty_fmt;
 use std::cmp::Ordering;
 use std::convert::AsRef;
 use std::fmt::{self, Display};
-use std::io::Cursor;
+use std::io::{Cursor, Seek, SeekFrom};
 
 /// Nodes that are persisted to disk.
 // TODO: replace `hash: Vec<u8>` with `hash: Hash`. This requires patching /
@@ -15,7 +15,7 @@ use std::io::Cursor;
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Node {
   pub(crate) index: usize,
-  pub(crate) hash: Vec<u8>,
+  pub(crate) hash: Hash,
   pub(crate) length: usize,
   pub(crate) parent: usize,
   pub(crate) data: Option<Vec<u8>>,
@@ -24,7 +24,7 @@ pub struct Node {
 impl Node {
   /// Create a new instance.
   // TODO: ensure sizes are correct.
-  pub fn new(index: usize, hash: Vec<u8>, length: usize) -> Self {
+  pub fn new(index: usize, hash: Hash, length: usize) -> Self {
     Self {
       index,
       hash,
@@ -41,16 +41,15 @@ impl Node {
     ensure!(buffer.len() == 40, "buffer should be 40 bytes");
 
     let parent = flat_tree::parent(index);
-    let mut reader = Cursor::new(buffer);
 
     // TODO: subslice directly, move cursor forward.
     let capacity = 32;
-    let mut hash = Vec::with_capacity(capacity);
-    for _ in 0..capacity {
-      hash.push(reader.read_u8()?);
-    }
+    let hash = Hash::from_bytes(&buffer[..capacity]);
 
+    let mut reader = Cursor::new(buffer);
+    reader.seek(SeekFrom::Start(capacity as u64))?;
     // TODO: This will blow up on 32 bit systems, because usize can be 32 bits.
+    // Note: we could stop using usize on any protocol specific parts of code?
     let length = reader.read_u64::<BigEndian>()? as usize;
     Ok(Self {
       hash,
@@ -64,7 +63,7 @@ impl Node {
   /// Convert to a buffer that can be written to disk.
   pub fn to_bytes(&self) -> Result<Vec<u8>> {
     let mut writer = Vec::with_capacity(40);
-    writer.extend_from_slice(&self.hash);
+    writer.extend_from_slice(&self.hash.as_bytes());
     writer.write_u64::<BigEndian>(self.length as u64)?;
     Ok(writer)
   }
@@ -78,7 +77,7 @@ impl NodeTrait for Node {
 
   #[inline]
   fn hash(&self) -> &[u8] {
-    &self.hash
+    &self.hash.as_bytes()
   }
 
   #[inline]
@@ -109,9 +108,7 @@ impl Display for Node {
     write!(
       f,
       "Node {{ index: {}, hash: {}, length: {} }}",
-      self.index,
-      pretty_fmt(&self.hash).unwrap(),
-      self.length
+      self.index, self.hash, self.length
     )
   }
 }