1 files changed, 96 insertions, 0 deletions
diff --git a/generic.c b/generic.c
new file mode 100644
index 0000000..4e311df
--- /dev/null
+++ b/generic.c
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include <linux/kernel.h>
+#include <crypto/algapi.h>
+
+enum {
+	CHACHA20_IV_SIZE = 16,
+	CHACHA20_KEY_SIZE = 32,
+	CHACHA20_BLOCK_SIZE = 64,
+	CHACHA20_BLOCK_WORDS = CHACHA20_BLOCK_SIZE / sizeof(u32)
+};
+
+#define EXPAND_32_BYTE_K 0x61707865U, 0x3320646eU, 0x79622d32U, 0x6b206574U
+
+#define QUARTER_ROUND(x, a, b, c, d) ( \
+	x[a] += x[b], \
+	x[d] = rol32((x[d] ^ x[a]), 16), \
+	x[c] += x[d], \
+	x[b] = rol32((x[b] ^ x[c]), 12), \
+	x[a] += x[b], \
+	x[d] = rol32((x[d] ^ x[a]), 8), \
+	x[c] += x[d], \
+	x[b] = rol32((x[b] ^ x[c]), 7) \
+)
+
+#define C(i, j) (i * 4 + j)
+
+#define DOUBLE_ROUND(x) ( \
+	/* Column Round */ \
+	QUARTER_ROUND(x, C(0, 0), C(1, 0), C(2, 0), C(3, 0)), \
+	QUARTER_ROUND(x, C(0, 1), C(1, 1), C(2, 1), C(3, 1)), \
+	QUARTER_ROUND(x, C(0, 2), C(1, 2), C(2, 2), C(3, 2)), \
+	QUARTER_ROUND(x, C(0, 3), C(1, 3), C(2, 3), C(3, 3)), \
+	/* Diagonal Round */ \
+	QUARTER_ROUND(x, C(0, 0), C(1, 1), C(2, 2), C(3, 3)), \
+	QUARTER_ROUND(x, C(0, 1), C(1, 2), C(2, 3), C(3, 0)), \
+	QUARTER_ROUND(x, C(0, 2), C(1, 3), C(2, 0), C(3, 1)), \
+	QUARTER_ROUND(x, C(0, 3), C(1, 0), C(2, 1), C(3, 2)) \
+)
+
+#define TWENTY_ROUNDS(x) ( \
+	DOUBLE_ROUND(x), \
+	DOUBLE_ROUND(x), \
+	DOUBLE_ROUND(x), \
+	DOUBLE_ROUND(x), \
+	DOUBLE_ROUND(x), \
+	DOUBLE_ROUND(x), \
+	DOUBLE_ROUND(x), \
+	DOUBLE_ROUND(x), \
+	DOUBLE_ROUND(x), \
+	DOUBLE_ROUND(x) \
+)
+
+static void chacha20_block_generic(__le32 *stream, u32 *state)
+{
+	u32 x[CHACHA20_BLOCK_WORDS];
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(x); ++i)
+		x[i] = state[i];
+
+	TWENTY_ROUNDS(x);
+
+	for (i = 0; i < ARRAY_SIZE(x); ++i)
+		stream[i] = cpu_to_le32(x[i] + state[i]);
+
+	++state[12];
+}
+
+void chacha20_generic(u8 *out, const u8 *in, u32 len, const u32 key[8], const u32 counter[4])
+{
+	__le32 buf[CHACHA20_BLOCK_WORDS];
+	u32 x[] = {
+		EXPAND_32_BYTE_K,
+		key[0], key[1], key[2], key[3],
+		key[4], key[5], key[6], key[7],
+		counter[0], counter[1], counter[2], counter[3]
+	};
+
+	if (out != in)
+		memmove(out, in, len);
+
+	while (len >= CHACHA20_BLOCK_SIZE) {
+		chacha20_block_generic(buf, x);
+		crypto_xor(out, (u8 *)buf, CHACHA20_BLOCK_SIZE);
+		len -= CHACHA20_BLOCK_SIZE;
+		out += CHACHA20_BLOCK_SIZE;
+	}
+	if (len) {
+		chacha20_block_generic(buf, x);
+		crypto_xor(out, (u8 *)buf, len);
+	}
+}