1/*
2 * Glue code for optimized assembly version of  Salsa20.
3 *
4 * Copyright (c) 2007 Tan Swee Heng <thesweeheng@gmail.com>
5 *
6 * The assembly codes are public domain assembly codes written by Daniel. J.
7 * Bernstein <djb@cr.yp.to>. The codes are modified to include indentation
8 * and to remove extraneous comments and functions that are not needed.
9 * - i586 version, renamed as salsa20-i586-asm_32.S
10 *   available from <http://cr.yp.to/snuffle/salsa20/x86-pm/salsa20.s>
11 * - x86-64 version, renamed as salsa20-x86_64-asm_64.S
12 *   available from <http://cr.yp.to/snuffle/salsa20/amd64-3/salsa20.s>
13 *
14 * This program is free software; you can redistribute it and/or modify it
15 * under the terms of the GNU General Public License as published by the Free
16 * Software Foundation; either version 2 of the License, or (at your option)
17 * any later version.
18 *
19 */
20
21#include <crypto/algapi.h>
22#include <linux/module.h>
23#include <linux/crypto.h>
24
25#define SALSA20_IV_SIZE        8U
26#define SALSA20_MIN_KEY_SIZE  16U
27#define SALSA20_MAX_KEY_SIZE  32U
28
29struct salsa20_ctx
30{
31	u32 input[16];
32};
33
34asmlinkage void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k,
35				 u32 keysize, u32 ivsize);
36asmlinkage void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv);
37asmlinkage void salsa20_encrypt_bytes(struct salsa20_ctx *ctx,
38				      const u8 *src, u8 *dst, u32 bytes);
39
40static int setkey(struct crypto_tfm *tfm, const u8 *key,
41		  unsigned int keysize)
42{
43	struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
44	salsa20_keysetup(ctx, key, keysize*8, SALSA20_IV_SIZE*8);
45	return 0;
46}
47
48static int encrypt(struct blkcipher_desc *desc,
49		   struct scatterlist *dst, struct scatterlist *src,
50		   unsigned int nbytes)
51{
52	struct blkcipher_walk walk;
53	struct crypto_blkcipher *tfm = desc->tfm;
54	struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
55	int err;
56
57	blkcipher_walk_init(&walk, dst, src, nbytes);
58	err = blkcipher_walk_virt_block(desc, &walk, 64);
59
60	salsa20_ivsetup(ctx, walk.iv);
61
62	if (likely(walk.nbytes == nbytes))
63	{
64		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
65				      walk.dst.virt.addr, nbytes);
66		return blkcipher_walk_done(desc, &walk, 0);
67	}
68
69	while (walk.nbytes >= 64) {
70		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
71				      walk.dst.virt.addr,
72				      walk.nbytes - (walk.nbytes % 64));
73		err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
74	}
75
76	if (walk.nbytes) {
77		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
78				      walk.dst.virt.addr, walk.nbytes);
79		err = blkcipher_walk_done(desc, &walk, 0);
80	}
81
82	return err;
83}
84
85static struct crypto_alg alg = {
86	.cra_name           =   "salsa20",
87	.cra_driver_name    =   "salsa20-asm",
88	.cra_priority       =   200,
89	.cra_flags          =   CRYPTO_ALG_TYPE_BLKCIPHER,
90	.cra_type           =   &crypto_blkcipher_type,
91	.cra_blocksize      =   1,
92	.cra_ctxsize        =   sizeof(struct salsa20_ctx),
93	.cra_alignmask      =	3,
94	.cra_module         =   THIS_MODULE,
95	.cra_u              =   {
96		.blkcipher = {
97			.setkey         =   setkey,
98			.encrypt        =   encrypt,
99			.decrypt        =   encrypt,
100			.min_keysize    =   SALSA20_MIN_KEY_SIZE,
101			.max_keysize    =   SALSA20_MAX_KEY_SIZE,
102			.ivsize         =   SALSA20_IV_SIZE,
103		}
104	}
105};
106
107static int __init init(void)
108{
109	return crypto_register_alg(&alg);
110}
111
112static void __exit fini(void)
113{
114	crypto_unregister_alg(&alg);
115}
116
117module_init(init);
118module_exit(fini);
119
120MODULE_LICENSE("GPL");
121MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm (optimized assembly version)");
122MODULE_ALIAS("salsa20");
123MODULE_ALIAS("salsa20-asm");
124