--- /dev/null
+/*
+ * Salsa20: Salsa20 stream cipher algorithm
+ *
+ * Copyright (c) 2007 Tan Swee Heng <thesweeheng@gmail.com>
+ *
+ * Derived from:
+ * - salsa20.c: Public domain C code by Daniel J. Bernstein <djb@cr.yp.to>
+ *
+ * Salsa20 is a stream cipher candidate in eSTREAM, the ECRYPT Stream
+ * Cipher Project. It is designed by Daniel J. Bernstein <djb@cr.yp.to>.
+ * More information about eSTREAM and Salsa20 can be found here:
+ * http://www.ecrypt.eu.org/stream/
+ * http://cr.yp.to/snuffle.html
+ *
+ * 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/init.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/crypto.h>
+#include <linux/types.h>
+#include <linux/bitops.h>
+#include <crypto/algapi.h>
+#include <asm/byteorder.h>
+
+#define SALSA20_IV_SIZE 8U
+#define SALSA20_MIN_KEY_SIZE 16U
+#define SALSA20_MAX_KEY_SIZE 32U
+
+/*
+ * Start of code taken from D. J. Bernstein's reference implementation.
+ * With some modifications and optimizations made to suit our needs.
+ */
+
+/*
+salsa20-ref.c version 20051118
+D. J. Bernstein
+Public domain.
+*/
+
+#define U32TO8_LITTLE(p, v) \
+ { (p)[0] = (v >> 0) & 0xff; (p)[1] = (v >> 8) & 0xff; \
+ (p)[2] = (v >> 16) & 0xff; (p)[3] = (v >> 24) & 0xff; }
+#define U8TO32_LITTLE(p) \
+ (((u32)((p)[0]) ) | ((u32)((p)[1]) << 8) | \
+ ((u32)((p)[2]) << 16) | ((u32)((p)[3]) << 24) )
+
+struct salsa20_ctx
+{
+ u32 input[16];
+};
+
+static void salsa20_wordtobyte(u8 output[64], const u32 input[16])
+{
+ u32 x[16];
+ int i;
+
+ memcpy(x, input, sizeof(x));
+ for (i = 20; i > 0; i -= 2) {
+ x[ 4] ^= rol32((x[ 0] + x[12]), 7);
+ x[ 8] ^= rol32((x[ 4] + x[ 0]), 9);
+ x[12] ^= rol32((x[ 8] + x[ 4]), 13);
+ x[ 0] ^= rol32((x[12] + x[ 8]), 18);
+ x[ 9] ^= rol32((x[ 5] + x[ 1]), 7);
+ x[13] ^= rol32((x[ 9] + x[ 5]), 9);
+ x[ 1] ^= rol32((x[13] + x[ 9]), 13);
+ x[ 5] ^= rol32((x[ 1] + x[13]), 18);
+ x[14] ^= rol32((x[10] + x[ 6]), 7);
+ x[ 2] ^= rol32((x[14] + x[10]), 9);
+ x[ 6] ^= rol32((x[ 2] + x[14]), 13);
+ x[10] ^= rol32((x[ 6] + x[ 2]), 18);
+ x[ 3] ^= rol32((x[15] + x[11]), 7);
+ x[ 7] ^= rol32((x[ 3] + x[15]), 9);
+ x[11] ^= rol32((x[ 7] + x[ 3]), 13);
+ x[15] ^= rol32((x[11] + x[ 7]), 18);
+ x[ 1] ^= rol32((x[ 0] + x[ 3]), 7);
+ x[ 2] ^= rol32((x[ 1] + x[ 0]), 9);
+ x[ 3] ^= rol32((x[ 2] + x[ 1]), 13);
+ x[ 0] ^= rol32((x[ 3] + x[ 2]), 18);
+ x[ 6] ^= rol32((x[ 5] + x[ 4]), 7);
+ x[ 7] ^= rol32((x[ 6] + x[ 5]), 9);
+ x[ 4] ^= rol32((x[ 7] + x[ 6]), 13);
+ x[ 5] ^= rol32((x[ 4] + x[ 7]), 18);
+ x[11] ^= rol32((x[10] + x[ 9]), 7);
+ x[ 8] ^= rol32((x[11] + x[10]), 9);
+ x[ 9] ^= rol32((x[ 8] + x[11]), 13);
+ x[10] ^= rol32((x[ 9] + x[ 8]), 18);
+ x[12] ^= rol32((x[15] + x[14]), 7);
+ x[13] ^= rol32((x[12] + x[15]), 9);
+ x[14] ^= rol32((x[13] + x[12]), 13);
+ x[15] ^= rol32((x[14] + x[13]), 18);
+ }
+ for (i = 0; i < 16; ++i)
+ x[i] += input[i];
+ for (i = 0; i < 16; ++i)
+ U32TO8_LITTLE(output + 4 * i,x[i]);
+}
+
+static const char sigma[16] = "expand 32-byte k";
+static const char tau[16] = "expand 16-byte k";
+
+static void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k, u32 kbytes)
+{
+ const char *constants;
+
+ ctx->input[1] = U8TO32_LITTLE(k + 0);
+ ctx->input[2] = U8TO32_LITTLE(k + 4);
+ ctx->input[3] = U8TO32_LITTLE(k + 8);
+ ctx->input[4] = U8TO32_LITTLE(k + 12);
+ if (kbytes == 32) { /* recommended */
+ k += 16;
+ constants = sigma;
+ } else { /* kbytes == 16 */
+ constants = tau;
+ }
+ ctx->input[11] = U8TO32_LITTLE(k + 0);
+ ctx->input[12] = U8TO32_LITTLE(k + 4);
+ ctx->input[13] = U8TO32_LITTLE(k + 8);
+ ctx->input[14] = U8TO32_LITTLE(k + 12);
+ ctx->input[0] = U8TO32_LITTLE(constants + 0);
+ ctx->input[5] = U8TO32_LITTLE(constants + 4);
+ ctx->input[10] = U8TO32_LITTLE(constants + 8);
+ ctx->input[15] = U8TO32_LITTLE(constants + 12);
+}
+
+static void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv)
+{
+ ctx->input[6] = U8TO32_LITTLE(iv + 0);
+ ctx->input[7] = U8TO32_LITTLE(iv + 4);
+ ctx->input[8] = 0;
+ ctx->input[9] = 0;
+}
+
+static void salsa20_encrypt_bytes(struct salsa20_ctx *ctx, u8 *dst,
+ const u8 *src, unsigned int bytes)
+{
+ u8 buf[64];
+
+ if (dst != src)
+ memcpy(dst, src, bytes);
+
+ while (bytes) {
+ salsa20_wordtobyte(buf, ctx->input);
+
+ ctx->input[8]++;
+ if (!ctx->input[8])
+ ctx->input[9]++;
+
+ if (bytes <= 64) {
+ crypto_xor(dst, buf, bytes);
+ return;
+ }
+
+ crypto_xor(dst, buf, 64);
+ bytes -= 64;
+ dst += 64;
+ }
+}
+
+/*
+ * End of code taken from D. J. Bernstein's reference implementation.
+ */
+
+static int setkey(struct crypto_tfm *tfm, const u8 *key,
+ unsigned int keysize)
+{
+ struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
+ salsa20_keysetup(ctx, key, keysize);
+ return 0;
+}
+
+static int encrypt(struct blkcipher_desc *desc,
+ struct scatterlist *dst, struct scatterlist *src,
+ unsigned int nbytes)
+{
+ struct blkcipher_walk walk;
+ struct crypto_blkcipher *tfm = desc->tfm;
+ struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
+ int err;
+
+ blkcipher_walk_init(&walk, dst, src, nbytes);
+ err = blkcipher_walk_virt_block(desc, &walk, 64);
+
+ salsa20_ivsetup(ctx, walk.iv);
+
+ if (likely(walk.nbytes == nbytes))
+ {
+ salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
+ walk.src.virt.addr, nbytes);
+ return blkcipher_walk_done(desc, &walk, 0);
+ }
+
+ while (walk.nbytes >= 64) {
+ salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
+ walk.src.virt.addr,
+ walk.nbytes - (walk.nbytes % 64));
+ err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
+ }
+
+ if (walk.nbytes) {
+ salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
+ walk.src.virt.addr, walk.nbytes);
+ err = blkcipher_walk_done(desc, &walk, 0);
+ }
+
+ return err;
+}
+
+static struct crypto_alg alg = {
+ .cra_name = "salsa20",
+ .cra_driver_name = "salsa20-generic",
+ .cra_priority = 100,
+ .cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER,
+ .cra_type = &crypto_blkcipher_type,
+ .cra_blocksize = 1,
+ .cra_ctxsize = sizeof(struct salsa20_ctx),
+ .cra_alignmask = 3,
+ .cra_module = THIS_MODULE,
+ .cra_u = {
+ .blkcipher = {
+ .setkey = setkey,
+ .encrypt = encrypt,
+ .decrypt = encrypt,
+ .min_keysize = SALSA20_MIN_KEY_SIZE,
+ .max_keysize = SALSA20_MAX_KEY_SIZE,
+ .ivsize = SALSA20_IV_SIZE,
+ }
+ }
+};
+
+static int __init salsa20_generic_mod_init(void)
+{
+ return crypto_register_alg(&alg);
+}
+
+static void __exit salsa20_generic_mod_fini(void)
+{
+ crypto_unregister_alg(&alg);
+}
+
+module_init(salsa20_generic_mod_init);
+module_exit(salsa20_generic_mod_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm");
+MODULE_ALIAS_CRYPTO("salsa20");
+MODULE_ALIAS_CRYPTO("salsa20-generic");
Code Review / kvmfornfv.git / blobdiff