Fix ChaCha20 Alignment Issues

benchmarks/stdlib/crypto/chacha20.c3

@@ -2,6 +2,7 @@
 // Use of this source code is governed by the MIT license
 // a copy of which can be found in the LICENSE_STDLIB file.
 module chacha20_benchmarks;
+
 import std::crypto::chacha20;
 
 
@@ -15,11 +16,24 @@ const char[] KEY = x'98bef1469be7269837a45bfbc92a5a6ac762507cf96443bf33b96b1bd4c
 const char[] NONCE = x'44e792d63335abb1582e9253';
 const uint COUNTER = 42;
 
-char[] one_megabyte = { [0..1024*1024] = 0xA5 };
+char[] one_mb @align(ulong.sizeof) = { [0..1024*1024] = 0xA5 };
 
 // This doesn't test both encryption + decryption, because it's a symmetric operation that shares
 //   a single common data transformation. Testing one limb is enough.
 fn void gogo_chacha20() @benchmark
 {
-	chacha20::encrypt_mut(one_megabyte[..], KEY, NONCE, COUNTER);
+	chacha20::encrypt_mut(one_mb[..], KEY, NONCE, COUNTER);
+}
+
+// Check what the speed of an unligned buffer looks like.
+fn void gogo_chacha20_unaligned() @benchmark => @pool()
+{
+    char[] copy = mem::talloc_array(char, one_mb.len + 3);
+    char[] im_off_slightly = copy[3..];
+    copy[3..] = one_mb[..];
+    assert((usz)im_off_slightly.ptr % usz.sizeof > 0);
+
+    runtime::@start_benchmark();
+	chacha20::encrypt_mut(im_off_slightly, KEY, NONCE, COUNTER);
+    runtime::@end_benchmark();
 }

lib/std/crypto/chacha20.c3

@@ -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;
 	}
 

src/compiler/sema_expr.c

@@ -8122,7 +8122,7 @@ static bool sema_expr_analyse_mod(SemaContext *context, Expr *expr, Expr *left,
 {
 	// 1. Analyse both sides and promote to a common type
 	OperatorOverload overload = OVERLOAD_REMINDER;
-	if (!sema_binary_analyse_arithmetic_subexpr(context, expr, "Cannot calculate the reminder %s %% %s",
+	if (!sema_binary_analyse_arithmetic_subexpr(context, expr, "Cannot calculate the remainder %s %% %s",
 		false, &overload, failed_ref)) return false;
 	if (!overload) return true;
 

test/test_suite/vector/vector_pointer_errors.c3

@@ -6,7 +6,7 @@ fn void pointer_add_sub_diff()
 	int*[<2>] y;
     double*[<2>] z = y; // #error: 'int*[<2>]' to 'double*[<2>]'
 	y / y; // #error: Cannot divide
-	y % y; // #error: Cannot calculate the reminder
+	y % y; // #error: Cannot calculate the remainder
 	y * y; // #error: multiply
 	y ^ y; // #error: not defined
 	iptr[<2>] g = (iptr[<2>])y;

test/unit/stdlib/crypto/chacha20.c3

@@ -412,28 +412,31 @@ fn void scrolling_input_unaligned_permutations_with_random_chunks()
 {
 	// Paranoia, honestly... Use a known test vector a couple blocks long, and - no matter the alignment started from - ensure the same result.
 	Lcg64Random rand;
-	random::seed(&rand, 0x1337_83fb_c1ac_1a20);
+	random::seed(&rand, 0x1337_83fb_c1ac_eeee);
 
 	char[*] key = sha256::hash("dance with me");
 	char[*] nonce = "123456789abc";
  
 	for (usz i = 1; i < ulong.sizeof + 1; i++)
 	{
-		for (usz j = 1; j < LARGE_INPUT.len; j++) @pool()
-		{
-			char[] unaligned @align(ulong.sizeof) = mem::talloc_array(char, j + ulong.sizeof);
-			char[] encrypt_me = unaligned[i:j];
-			encrypt_me[..] = LARGE_INPUT[:j];
+		for (usz j = 1; j < LARGE_INPUT.len; j++)
+        {
+            for (usz k = 1; k < 128; k++) @pool()
+            {
+                char[] unaligned @align(ulong.sizeof) = mem::talloc_array(char, 1 + j + ulong.sizeof);
+                unaligned[i:j] = LARGE_INPUT[:j];
+                test::@check(chacha20::tencrypt(unaligned[i:j], key, nonce) == LARGE_EXPECTED[:j], "Mismatched permutation of hash on index (%d, %d).", i, j);
 
-			ChaCha20 c @noinit;
-			defer c.destroy();
-			c.init(key, nonce);
-			for (usz x = 1; encrypt_me.len; encrypt_me = encrypt_me[x..], x = (rand.next_byte() % min(20, encrypt_me.len ?: 1)) ?: 1) c.transform(encrypt_me[:x]);
-			test::@check(unaligned[i:j] == LARGE_EXPECTED[:j], "Mismatched permutation of hash on index (%d, %d).", i, j);
+                char[] encrypt_me = unaligned[i:j];
+                ChaCha20 c @noinit;
+                defer c.destroy();
+                c.init(key, nonce);
+                for (usz x = 1; encrypt_me.len; encrypt_me = encrypt_me[x..], x = (rand.next_byte() % min(k, encrypt_me.len ?: 1)) ?: 1) c.transform(encrypt_me[:x]);
+                test::@check(unaligned[i:j] == LARGE_EXPECTED[:j], "Mismatched permutation of hash on index (%d, %d; %d).", i, j, k);
 
-			// test::@check(chacha20::tencrypt(unaligned[i:j], key, nonce) == LARGE_EXPECTED[:j], "Mismatched permutation of hash on index (%d, %d).", i, j);
-			test::@check(chacha20::tencrypt(LARGE_INPUT[:j], key, nonce) == LARGE_EXPECTED[:j], "Mismatched permutation of hash on index (%d, %d).", i, j);
-		};
+                test::@check(chacha20::tencrypt(LARGE_INPUT[:j], key, nonce) == LARGE_EXPECTED[:j], "Mismatched permutation of hash on index (%d, %d).", i, j);
+            };
+        }
 	}
 }