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Fix ChaCha20 Alignment Issues

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This commit is contained in:
Zack Puhl
2025-12-17 22:57:34 +00:00
committed by Christoffer Lerno
parent 436af4dbca
commit 97a9cab218
5 changed files with 48 additions and 42 deletions
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37
lib/std/crypto/chacha20.c3
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@@ -62,17 +62,6 @@ macro quarter_round(uint* x, int a, int b, int c, int d) @local
x[c] += x[d]; x[b] = (x[b] ^ x[c]).rotl(7);
}
<* Check the position of the keystream/input buffer usage, and mutate it when necessary. *>
macro ChaCha20.check_position(&self) @local
{
if (self.position >= BLOCK_SIZE)
{
self.mutate_keystream();
self.position = 0;
}
}
<* Process the next (or final) chunk of ingested data. *>
fn void ChaCha20.mutate_keystream(&self) @local @inline
{
@@ -136,33 +125,33 @@ fn void ChaCha20.transform(&self, char[] data)
if (self.position < BLOCK_SIZE)
{
usz len = data.len < (BLOCK_SIZE - self.position) ? data.len : (BLOCK_SIZE - self.position);
for (usz i = 0; i < len; i++)
{
data[i] ^= key_stream[self.position + i];
}
for (usz i = 0; i < len; i++) data[i] ^= key_stream[self.position + i];
self.position += len;
data = data[len..];
}
// 2. Process full blocks at a time, word by word according to the system's architecture.
for (; data.len >= BLOCK_SIZE; data = data[BLOCK_SIZE..])
// 2. Get the amount of bytes offset from the nearest alignment boundary.
// Process full blocks at a time, word by word according to the system's architecture.
// Any extra bytes on each side are dynamically processed byte-by-byte.
usz offset = usz.sizeof - (((usz)data.ptr % usz.sizeof) ?: usz.sizeof);
for (usz x = offset; data.len >= BLOCK_SIZE; data = data[BLOCK_SIZE..], x = offset)
{
self.mutate_keystream();
for (usz i = 0; i < BLOCK_SIZE / usz.sizeof; i++)
if (offset) foreach (i, &b : data[:offset]) *b ^= key_stream[i];
char[] aligned_data = data[offset..];
for (; x <= (BLOCK_SIZE - usz.sizeof); x += usz.sizeof)
{
usz* data_ref = (usz*)data.ptr + i;
@unaligned_store(*data_ref, @unaligned_load(*data_ref, 1) ^ ((usz*)&self.key_stream)[i], 1);
((usz*)aligned_data.ptr)[x / usz.sizeof] ^= @unaligned_load(*(usz*)(&key_stream[x]), 1);
}
for (; x < BLOCK_SIZE; x++) data[x] ^= key_stream[x];
}
// 3. Process any remaining bytes.
if (data.len > 0)
{
self.mutate_keystream();
for (usz i = 0; i < data.len; i++)
{
data[i] ^= key_stream[i];
}
for (usz i = 0; i < data.len; i++) data[i] ^= key_stream[i];
self.position = data.len;
}