1 files changed, 111 insertions, 0 deletions
diff --git a/c_src/linux/crypto/chacha20_generic.c b/c_src/linux/crypto/chacha20_generic.c
new file mode 100644
index 00000000..914189e7
--- /dev/null
+++ b/c_src/linux/crypto/chacha20_generic.c
@@ -0,0 +1,111 @@
+/*
+ * ChaCha20 256-bit cipher algorithm, RFC7539
+ *
+ * Copyright (C) 2015 Martin Willi
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/byteorder.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/scatterlist.h>
+#include <asm/unaligned.h>
+
+#include <linux/crypto.h>
+#include <crypto/algapi.h>
+#include <crypto/chacha.h>
+#include <crypto/skcipher.h>
+
+#include <sodium/crypto_stream_chacha20.h>
+
+static struct skcipher_alg alg;
+
+struct chacha20_tfm {
+	struct crypto_skcipher	tfm;
+	u32			key[8];
+};
+
+static int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
+				  unsigned int keysize)
+{
+	struct chacha20_tfm *ctx =
+		container_of(tfm, struct chacha20_tfm, tfm);
+	int i;
+
+	if (keysize != CHACHA_KEY_SIZE)
+		return -EINVAL;
+
+	for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
+		ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
+
+	return 0;
+}
+
+static int crypto_chacha20_crypt(struct skcipher_request *req)
+{
+	struct chacha20_tfm *ctx =
+		container_of(req->tfm, struct chacha20_tfm, tfm.base);
+	struct scatterlist *sg = req->src;
+	unsigned nbytes = req->cryptlen;
+	u32 iv[4];
+	int ret;
+
+	BUG_ON(req->src != req->dst);
+
+	memcpy(iv, req->iv, sizeof(iv));
+
+	while (1) {
+		ret = crypto_stream_chacha20_xor_ic(sg_virt(sg),
+						    sg_virt(sg),
+						    sg->length,
+						    (void *) &iv[2],
+						    iv[0] | ((u64) iv[1] << 32),
+						    (void *) ctx->key);
+		BUG_ON(ret);
+
+		nbytes -= sg->length;
+
+		if (sg_is_last(sg))
+			break;
+
+		BUG_ON(sg->length % CHACHA_BLOCK_SIZE);
+		iv[0] += sg->length / CHACHA_BLOCK_SIZE;
+		sg = sg_next(sg);
+	};
+
+	BUG_ON(nbytes);
+
+	return 0;
+}
+
+static void *crypto_chacha20_alloc_tfm(void)
+{
+	struct chacha20_tfm *tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
+
+	if (!tfm)
+		return NULL;
+
+	tfm->tfm.base.alg	= &alg.base;
+	tfm->tfm.setkey		= crypto_chacha20_setkey;
+	tfm->tfm.encrypt	= crypto_chacha20_crypt;
+	tfm->tfm.decrypt	= crypto_chacha20_crypt;
+	tfm->tfm.ivsize		= CHACHA_IV_SIZE;
+	tfm->tfm.keysize	= CHACHA_KEY_SIZE;
+
+	return tfm;
+}
+
+static struct skcipher_alg alg = {
+	.base.cra_name		= "chacha20",
+	.base.alloc_tfm		= crypto_chacha20_alloc_tfm,
+};
+
+__attribute__((constructor(110)))
+static int chacha20_generic_mod_init(void)
+{
+	return crypto_register_skcipher(&alg);
+}