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/null.h>
23 #include <crypto/rng.h>
24 #include <crypto/scatterwalk.h>
25 #include <linux/err.h>
26 #include <linux/init.h>
27 #include <linux/kernel.h>
29 #include <linux/module.h>
30 #include <linux/percpu.h>
31 #include <linux/spinlock.h>
32 #include <linux/string.h>
34 #define MAX_IV_SIZE 16
37 /* aead_geniv_ctx must be first the element */
38 struct aead_geniv_ctx geniv;
39 struct crypto_blkcipher *null;
40 u8 salt[] __attribute__ ((aligned(__alignof__(u32))));
43 static DEFINE_PER_CPU(u32 [MAX_IV_SIZE / sizeof(u32)], echainiv_iv);
45 /* We don't care if we get preempted and read/write IVs from the next CPU. */
46 static void echainiv_read_iv(u8 *dst, unsigned size)
49 u32 __percpu *b = echainiv_iv;
51 for (; size >= 4; size -= 4) {
52 *a++ = this_cpu_read(*b);
57 static void echainiv_write_iv(const u8 *src, unsigned size)
59 const u32 *a = (const u32 *)src;
60 u32 __percpu *b = echainiv_iv;
62 for (; size >= 4; size -= 4) {
63 this_cpu_write(*b, *a);
69 static void echainiv_encrypt_complete2(struct aead_request *req, int err)
71 struct aead_request *subreq = aead_request_ctx(req);
72 struct crypto_aead *geniv;
75 if (err == -EINPROGRESS)
81 geniv = crypto_aead_reqtfm(req);
82 ivsize = crypto_aead_ivsize(geniv);
84 echainiv_write_iv(subreq->iv, ivsize);
86 if (req->iv != subreq->iv)
87 memcpy(req->iv, subreq->iv, ivsize);
90 if (req->iv != subreq->iv)
94 static void echainiv_encrypt_complete(struct crypto_async_request *base,
97 struct aead_request *req = base->data;
99 echainiv_encrypt_complete2(req, err);
100 aead_request_complete(req, err);
103 static int echainiv_encrypt(struct aead_request *req)
105 struct crypto_aead *geniv = crypto_aead_reqtfm(req);
106 struct echainiv_ctx *ctx = crypto_aead_ctx(geniv);
107 struct aead_request *subreq = aead_request_ctx(req);
108 crypto_completion_t compl;
111 unsigned int ivsize = crypto_aead_ivsize(geniv);
114 if (req->cryptlen < ivsize)
117 aead_request_set_tfm(subreq, ctx->geniv.child);
119 compl = echainiv_encrypt_complete;
123 if (req->src != req->dst) {
124 struct blkcipher_desc desc = {
128 err = crypto_blkcipher_encrypt(
129 &desc, req->dst, req->src,
130 req->assoclen + req->cryptlen);
135 if (unlikely(!IS_ALIGNED((unsigned long)info,
136 crypto_aead_alignmask(geniv) + 1))) {
137 info = kmalloc(ivsize, req->base.flags &
138 CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL:
143 memcpy(info, req->iv, ivsize);
146 aead_request_set_callback(subreq, req->base.flags, compl, data);
147 aead_request_set_crypt(subreq, req->dst, req->dst,
148 req->cryptlen - ivsize, info);
149 aead_request_set_ad(subreq, req->assoclen + ivsize);
151 crypto_xor(info, ctx->salt, ivsize);
152 scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
153 echainiv_read_iv(info, ivsize);
155 err = crypto_aead_encrypt(subreq);
156 echainiv_encrypt_complete2(req, err);
160 static int echainiv_decrypt(struct aead_request *req)
162 struct crypto_aead *geniv = crypto_aead_reqtfm(req);
163 struct echainiv_ctx *ctx = crypto_aead_ctx(geniv);
164 struct aead_request *subreq = aead_request_ctx(req);
165 crypto_completion_t compl;
167 unsigned int ivsize = crypto_aead_ivsize(geniv);
169 if (req->cryptlen < ivsize + crypto_aead_authsize(geniv))
172 aead_request_set_tfm(subreq, ctx->geniv.child);
174 compl = req->base.complete;
175 data = req->base.data;
177 aead_request_set_callback(subreq, req->base.flags, compl, data);
178 aead_request_set_crypt(subreq, req->src, req->dst,
179 req->cryptlen - ivsize, req->iv);
180 aead_request_set_ad(subreq, req->assoclen + ivsize);
182 scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
183 if (req->src != req->dst)
184 scatterwalk_map_and_copy(req->iv, req->dst,
185 req->assoclen, ivsize, 1);
187 return crypto_aead_decrypt(subreq);
190 static int echainiv_init(struct crypto_tfm *tfm)
192 struct crypto_aead *geniv = __crypto_aead_cast(tfm);
193 struct echainiv_ctx *ctx = crypto_aead_ctx(geniv);
196 spin_lock_init(&ctx->geniv.lock);
198 crypto_aead_set_reqsize(geniv, sizeof(struct aead_request));
200 err = crypto_rng_get_bytes(crypto_default_rng, ctx->salt,
201 crypto_aead_ivsize(geniv));
205 ctx->null = crypto_get_default_null_skcipher();
206 err = PTR_ERR(ctx->null);
207 if (IS_ERR(ctx->null))
210 err = aead_geniv_init(tfm);
214 ctx->geniv.child = geniv->child;
215 geniv->child = geniv;
221 crypto_put_default_null_skcipher();
225 static void echainiv_exit(struct crypto_tfm *tfm)
227 struct echainiv_ctx *ctx = crypto_tfm_ctx(tfm);
229 crypto_free_aead(ctx->geniv.child);
230 crypto_put_default_null_skcipher();
233 static int echainiv_aead_create(struct crypto_template *tmpl,
236 struct aead_instance *inst;
237 struct crypto_aead_spawn *spawn;
238 struct aead_alg *alg;
241 inst = aead_geniv_alloc(tmpl, tb, 0, 0);
244 return PTR_ERR(inst);
246 spawn = aead_instance_ctx(inst);
247 alg = crypto_spawn_aead_alg(spawn);
249 if (alg->base.cra_aead.encrypt)
253 if (inst->alg.ivsize & (sizeof(u32) - 1) ||
254 inst->alg.ivsize > MAX_IV_SIZE)
257 inst->alg.encrypt = echainiv_encrypt;
258 inst->alg.decrypt = echainiv_decrypt;
260 inst->alg.base.cra_init = echainiv_init;
261 inst->alg.base.cra_exit = echainiv_exit;
263 inst->alg.base.cra_alignmask |= __alignof__(u32) - 1;
264 inst->alg.base.cra_ctxsize = sizeof(struct echainiv_ctx);
265 inst->alg.base.cra_ctxsize += inst->alg.ivsize;
268 err = aead_register_instance(tmpl, inst);
276 aead_geniv_free(inst);
280 static int echainiv_create(struct crypto_template *tmpl, struct rtattr **tb)
284 err = crypto_get_default_rng();
288 err = echainiv_aead_create(tmpl, tb);
296 crypto_put_default_rng();
300 static void echainiv_free(struct crypto_instance *inst)
302 aead_geniv_free(aead_instance(inst));
303 crypto_put_default_rng();
306 static struct crypto_template echainiv_tmpl = {
308 .create = echainiv_create,
309 .free = echainiv_free,
310 .module = THIS_MODULE,
313 static int __init echainiv_module_init(void)
315 return crypto_register_template(&echainiv_tmpl);
318 static void __exit echainiv_module_exit(void)
320 crypto_unregister_template(&echainiv_tmpl);
323 module_init(echainiv_module_init);
324 module_exit(echainiv_module_exit);
326 MODULE_LICENSE("GPL");
327 MODULE_DESCRIPTION("Encrypted Chain IV Generator");
328 MODULE_ALIAS_CRYPTO("echainiv");