2 * echainiv: Encrypted Chain IV Generator
4 * This generator generates an IV based on a sequence number by xoring it
5 * with a salt and then encrypting it with the same key as used to encrypt
6 * the plain text. This algorithm requires that the block size be equal
7 * to the IV size. It is mainly useful for CBC.
9 * This generator can only be used by algorithms where authentication
10 * is performed after encryption (i.e., authenc).
12 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
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)
21 #include <crypto/internal/geniv.h>
22 #include <crypto/scatterwalk.h>
23 #include <crypto/skcipher.h>
24 #include <linux/err.h>
25 #include <linux/init.h>
26 #include <linux/kernel.h>
28 #include <linux/module.h>
29 #include <linux/percpu.h>
30 #include <linux/spinlock.h>
31 #include <linux/string.h>
33 #define MAX_IV_SIZE 16
35 static DEFINE_PER_CPU(u32
[MAX_IV_SIZE
/ sizeof(u32
)], echainiv_iv
);
37 /* We don't care if we get preempted and read/write IVs from the next CPU. */
38 static void echainiv_read_iv(u8
*dst
, unsigned size
)
41 u32 __percpu
*b
= echainiv_iv
;
43 for (; size
>= 4; size
-= 4) {
44 *a
++ = this_cpu_read(*b
);
49 static void echainiv_write_iv(const u8
*src
, unsigned size
)
51 const u32
*a
= (const u32
*)src
;
52 u32 __percpu
*b
= echainiv_iv
;
54 for (; size
>= 4; size
-= 4) {
55 this_cpu_write(*b
, *a
);
61 static void echainiv_encrypt_complete2(struct aead_request
*req
, int err
)
63 struct aead_request
*subreq
= aead_request_ctx(req
);
64 struct crypto_aead
*geniv
;
67 if (err
== -EINPROGRESS
)
73 geniv
= crypto_aead_reqtfm(req
);
74 ivsize
= crypto_aead_ivsize(geniv
);
76 echainiv_write_iv(subreq
->iv
, ivsize
);
78 if (req
->iv
!= subreq
->iv
)
79 memcpy(req
->iv
, subreq
->iv
, ivsize
);
82 if (req
->iv
!= subreq
->iv
)
86 static void echainiv_encrypt_complete(struct crypto_async_request
*base
,
89 struct aead_request
*req
= base
->data
;
91 echainiv_encrypt_complete2(req
, err
);
92 aead_request_complete(req
, err
);
95 static int echainiv_encrypt(struct aead_request
*req
)
97 struct crypto_aead
*geniv
= crypto_aead_reqtfm(req
);
98 struct aead_geniv_ctx
*ctx
= crypto_aead_ctx(geniv
);
99 struct aead_request
*subreq
= aead_request_ctx(req
);
100 crypto_completion_t
compl;
103 unsigned int ivsize
= crypto_aead_ivsize(geniv
);
106 if (req
->cryptlen
< ivsize
)
109 aead_request_set_tfm(subreq
, ctx
->child
);
111 compl = echainiv_encrypt_complete
;
115 if (req
->src
!= req
->dst
) {
116 SKCIPHER_REQUEST_ON_STACK(nreq
, ctx
->sknull
);
118 skcipher_request_set_tfm(nreq
, ctx
->sknull
);
119 skcipher_request_set_callback(nreq
, req
->base
.flags
,
121 skcipher_request_set_crypt(nreq
, req
->src
, req
->dst
,
122 req
->assoclen
+ req
->cryptlen
,
125 err
= crypto_skcipher_encrypt(nreq
);
130 if (unlikely(!IS_ALIGNED((unsigned long)info
,
131 crypto_aead_alignmask(geniv
) + 1))) {
132 info
= kmalloc(ivsize
, req
->base
.flags
&
133 CRYPTO_TFM_REQ_MAY_SLEEP
? GFP_KERNEL
:
138 memcpy(info
, req
->iv
, ivsize
);
141 aead_request_set_callback(subreq
, req
->base
.flags
, compl, data
);
142 aead_request_set_crypt(subreq
, req
->dst
, req
->dst
,
143 req
->cryptlen
, info
);
144 aead_request_set_ad(subreq
, req
->assoclen
);
146 crypto_xor(info
, ctx
->salt
, ivsize
);
147 scatterwalk_map_and_copy(info
, req
->dst
, req
->assoclen
, ivsize
, 1);
148 echainiv_read_iv(info
, ivsize
);
150 err
= crypto_aead_encrypt(subreq
);
151 echainiv_encrypt_complete2(req
, err
);
155 static int echainiv_decrypt(struct aead_request
*req
)
157 struct crypto_aead
*geniv
= crypto_aead_reqtfm(req
);
158 struct aead_geniv_ctx
*ctx
= crypto_aead_ctx(geniv
);
159 struct aead_request
*subreq
= aead_request_ctx(req
);
160 crypto_completion_t
compl;
162 unsigned int ivsize
= crypto_aead_ivsize(geniv
);
164 if (req
->cryptlen
< ivsize
)
167 aead_request_set_tfm(subreq
, ctx
->child
);
169 compl = req
->base
.complete
;
170 data
= req
->base
.data
;
172 aead_request_set_callback(subreq
, req
->base
.flags
, compl, data
);
173 aead_request_set_crypt(subreq
, req
->src
, req
->dst
,
174 req
->cryptlen
- ivsize
, req
->iv
);
175 aead_request_set_ad(subreq
, req
->assoclen
+ ivsize
);
177 scatterwalk_map_and_copy(req
->iv
, req
->src
, req
->assoclen
, ivsize
, 0);
179 return crypto_aead_decrypt(subreq
);
182 static int echainiv_aead_create(struct crypto_template
*tmpl
,
185 struct aead_instance
*inst
;
186 struct crypto_aead_spawn
*spawn
;
187 struct aead_alg
*alg
;
190 inst
= aead_geniv_alloc(tmpl
, tb
, 0, 0);
193 return PTR_ERR(inst
);
195 spawn
= aead_instance_ctx(inst
);
196 alg
= crypto_spawn_aead_alg(spawn
);
199 if (inst
->alg
.ivsize
& (sizeof(u32
) - 1) ||
200 inst
->alg
.ivsize
> MAX_IV_SIZE
)
203 inst
->alg
.encrypt
= echainiv_encrypt
;
204 inst
->alg
.decrypt
= echainiv_decrypt
;
206 inst
->alg
.init
= aead_init_geniv
;
207 inst
->alg
.exit
= aead_exit_geniv
;
209 inst
->alg
.base
.cra_alignmask
|= __alignof__(u32
) - 1;
210 inst
->alg
.base
.cra_ctxsize
= sizeof(struct aead_geniv_ctx
);
211 inst
->alg
.base
.cra_ctxsize
+= inst
->alg
.ivsize
;
213 inst
->free
= aead_geniv_free
;
215 err
= aead_register_instance(tmpl
, inst
);
223 aead_geniv_free(inst
);
227 static void echainiv_free(struct crypto_instance
*inst
)
229 aead_geniv_free(aead_instance(inst
));
232 static struct crypto_template echainiv_tmpl
= {
234 .create
= echainiv_aead_create
,
235 .free
= echainiv_free
,
236 .module
= THIS_MODULE
,
239 static int __init
echainiv_module_init(void)
241 return crypto_register_template(&echainiv_tmpl
);
244 static void __exit
echainiv_module_exit(void)
246 crypto_unregister_template(&echainiv_tmpl
);
249 module_init(echainiv_module_init
);
250 module_exit(echainiv_module_exit
);
252 MODULE_LICENSE("GPL");
253 MODULE_DESCRIPTION("Encrypted Chain IV Generator");
254 MODULE_ALIAS_CRYPTO("echainiv");