argon2: migrate from the variable output traits (#739)

Closes #736

Author: newpavlov

Cargo.lock

@@ -15,7 +15,3 @@ exclude = ["benches", "fuzz"]
 
 [profile.dev]
 opt-level = 2
-
-[patch.crates-io.blake2]
-git = "https://github.com/RustCrypto/hashes"
-branch = "blake2/restore-blake-var"

Cargo.toml

@@ -3,12 +3,14 @@
 use crate::{Error, Result};
 
 use blake2::{
-    Blake2b512, Blake2bVar,
-    digest::{self, Digest},
+    Blake2b512, Blake2bVarCore,
+    digest::{
+        Digest,
+        block_api::{UpdateCore, VariableOutputCore},
+        block_buffer::LazyBuffer,
+    },
 };
 
-use core::convert::TryFrom;
-
 pub fn blake2b_long(inputs: &[&[u8]], out: &mut [u8]) -> Result<()> {
     if out.is_empty() {
         return Err(Error::OutputTooShort);
@@ -19,19 +21,17 @@ pub fn blake2b_long(inputs: &[&[u8]], out: &mut [u8]) -> Result<()> {
         .map_err(|_| Error::OutputTooLong)?;
 
     // Use blake2b directly if the output is small enough.
-    if out.len() <= Blake2b512::output_size() {
-        let mut digest = Blake2bVar::new(out.len()).map_err(|_| Error::OutputTooLong)?;
-
-        // Conflicting method name from `Digest` and `Update` traits
-        digest::Update::update(&mut digest, &len_bytes);
+    if let Ok(mut hasher) = Blake2bVarCore::new(out.len()) {
+        let mut buf = LazyBuffer::new(&len_bytes);
 
         for input in inputs {
-            digest::Update::update(&mut digest, input);
+            buf.digest_blocks(input, |blocks| hasher.update_blocks(blocks));
         }
 
-        digest
-            .finalize_variable(out)
-            .map_err(|_| Error::OutputTooLong)?;
+        let mut full_out = Default::default();
+        hasher.finalize_variable_core(&mut buf, &mut full_out);
+        let out_src = &full_out[..out.len()];
+        out.copy_from_slice(out_src);
 
         return Ok(());
     }
@@ -47,33 +47,28 @@ pub fn blake2b_long(inputs: &[&[u8]], out: &mut [u8]) -> Result<()> {
     let mut last_output = digest.finalize();
 
     // Then we write the first 32 bytes of this hash to the output
-    out[..half_hash_len].copy_from_slice(&last_output[..half_hash_len]);
+    let (first_chunk, mut out) = out.split_at_mut(half_hash_len);
+    first_chunk.copy_from_slice(&last_output[..half_hash_len]);
 
     // Next, we write a number of 32 byte blocks to the output.
     // Each block is the first 32 bytes of the hash of the last block.
     // The very last block of the output is excluded, and has a variable
     // length in range [1, 32].
-    let mut counter = 0;
-    let out_len = out.len();
-    for chunk in out[half_hash_len..]
-        .chunks_exact_mut(half_hash_len)
-        .take_while(|_| {
-            counter += half_hash_len;
-            out_len - counter > 64
-        })
-    {
+    while out.len() > 64 {
+        let (chunk, tail) = out.split_at_mut(half_hash_len);
+        out = tail;
         last_output = Blake2b512::digest(last_output);
         chunk.copy_from_slice(&last_output[..half_hash_len]);
     }
 
     // Calculate the last block with VarBlake2b.
-    let last_block_size = out.len() - counter;
-    let mut digest = Blake2bVar::new(last_block_size).map_err(|_| Error::OutputTooLong)?;
-
-    digest::Update::update(&mut digest, &last_output);
-    digest
-        .finalize_variable(&mut out[counter..])
-        .expect("invalid Blake2bVar out length");
+    let mut hasher = Blake2bVarCore::new(out.len())
+        .expect("`out.len()` is guaranteed to be smaller or equal to 64");
+    let mut buf = LazyBuffer::new(&last_output);
+    let mut full_out = Default::default();
+    hasher.finalize_variable_core(&mut buf, &mut full_out);
+    let out_src = &full_out[..out.len()];
+    out.copy_from_slice(out_src);
 
     Ok(())
 }