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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 
29 // use the ECRYPT_* function names
30 #define salsa20_keysetup        ECRYPT_keysetup
31 #define salsa20_ivsetup         ECRYPT_ivsetup
32 #define salsa20_encrypt_bytes   ECRYPT_encrypt_bytes
33 
34 struct salsa20_ctx
35 {
36 	u32 input[16];
37 };
38 
39 asmlinkage void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k,
40 				 u32 keysize, u32 ivsize);
41 asmlinkage void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv);
42 asmlinkage void salsa20_encrypt_bytes(struct salsa20_ctx *ctx,
43 				      const u8 *src, u8 *dst, u32 bytes);
44 
setkey(struct crypto_tfm * tfm,const u8 * key,unsigned int keysize)45 static int setkey(struct crypto_tfm *tfm, const u8 *key,
46 		  unsigned int keysize)
47 {
48 	struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
49 	salsa20_keysetup(ctx, key, keysize*8, SALSA20_IV_SIZE*8);
50 	return 0;
51 }
52 
encrypt(struct blkcipher_desc * desc,struct scatterlist * dst,struct scatterlist * src,unsigned int nbytes)53 static int encrypt(struct blkcipher_desc *desc,
54 		   struct scatterlist *dst, struct scatterlist *src,
55 		   unsigned int nbytes)
56 {
57 	struct blkcipher_walk walk;
58 	struct crypto_blkcipher *tfm = desc->tfm;
59 	struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
60 	int err;
61 
62 	blkcipher_walk_init(&walk, dst, src, nbytes);
63 	err = blkcipher_walk_virt_block(desc, &walk, 64);
64 
65 	salsa20_ivsetup(ctx, walk.iv);
66 
67 	if (likely(walk.nbytes == nbytes))
68 	{
69 		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
70 				      walk.dst.virt.addr, nbytes);
71 		return blkcipher_walk_done(desc, &walk, 0);
72 	}
73 
74 	while (walk.nbytes >= 64) {
75 		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
76 				      walk.dst.virt.addr,
77 				      walk.nbytes - (walk.nbytes % 64));
78 		err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
79 	}
80 
81 	if (walk.nbytes) {
82 		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
83 				      walk.dst.virt.addr, walk.nbytes);
84 		err = blkcipher_walk_done(desc, &walk, 0);
85 	}
86 
87 	return err;
88 }
89 
90 static struct crypto_alg alg = {
91 	.cra_name           =   "salsa20",
92 	.cra_driver_name    =   "salsa20-asm",
93 	.cra_priority       =   200,
94 	.cra_flags          =   CRYPTO_ALG_TYPE_BLKCIPHER,
95 	.cra_type           =   &crypto_blkcipher_type,
96 	.cra_blocksize      =   1,
97 	.cra_ctxsize        =   sizeof(struct salsa20_ctx),
98 	.cra_alignmask      =	3,
99 	.cra_module         =   THIS_MODULE,
100 	.cra_list           =   LIST_HEAD_INIT(alg.cra_list),
101 	.cra_u              =   {
102 		.blkcipher = {
103 			.setkey         =   setkey,
104 			.encrypt        =   encrypt,
105 			.decrypt        =   encrypt,
106 			.min_keysize    =   SALSA20_MIN_KEY_SIZE,
107 			.max_keysize    =   SALSA20_MAX_KEY_SIZE,
108 			.ivsize         =   SALSA20_IV_SIZE,
109 		}
110 	}
111 };
112 
init(void)113 static int __init init(void)
114 {
115 	return crypto_register_alg(&alg);
116 }
117 
fini(void)118 static void __exit fini(void)
119 {
120 	crypto_unregister_alg(&alg);
121 }
122 
123 module_init(init);
124 module_exit(fini);
125 
126 MODULE_LICENSE("GPL");
127 MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm (optimized assembly version)");
128 MODULE_ALIAS("salsa20");
129 MODULE_ALIAS("salsa20-asm");
130