1 /*
2 * eseqiv: Encrypted Sequence Number IV Generator
3 *
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.
8 *
9 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
10 *
11 * This program is free software; you can redistribute it and/or modify it
12 * under the terms of the GNU General Public License as published by the Free
13 * Software Foundation; either version 2 of the License, or (at your option)
14 * any later version.
15 *
16 */
17
18 #include <crypto/internal/skcipher.h>
19 #include <crypto/rng.h>
20 #include <crypto/scatterwalk.h>
21 #include <linux/err.h>
22 #include <linux/init.h>
23 #include <linux/kernel.h>
24 #include <linux/mm.h>
25 #include <linux/module.h>
26 #include <linux/scatterlist.h>
27 #include <linux/spinlock.h>
28 #include <linux/string.h>
29
30 struct eseqiv_request_ctx {
31 struct scatterlist src[2];
32 struct scatterlist dst[2];
33 char tail[];
34 };
35
36 struct eseqiv_ctx {
37 spinlock_t lock;
38 unsigned int reqoff;
39 char salt[];
40 };
41
42 static void eseqiv_complete2(struct skcipher_givcrypt_request *req)
43 {
44 struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
45 struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);
46
47 memcpy(req->giv, PTR_ALIGN((u8 *)reqctx->tail,
48 crypto_ablkcipher_alignmask(geniv) + 1),
49 crypto_ablkcipher_ivsize(geniv));
50 }
51
52 static void eseqiv_complete(struct crypto_async_request *base, int err)
53 {
54 struct skcipher_givcrypt_request *req = base->data;
55
56 if (err)
57 goto out;
58
59 eseqiv_complete2(req);
60
61 out:
62 skcipher_givcrypt_complete(req, err);
63 }
64
65 static void eseqiv_chain(struct scatterlist *head, struct scatterlist *sg,
66 int chain)
67 {
68 if (chain) {
69 head->length += sg->length;
70 sg = scatterwalk_sg_next(sg);
71 }
72
73 if (sg)
74 scatterwalk_sg_chain(head, 2, sg);
75 else
76 sg_mark_end(head);
77 }
78
79 static int eseqiv_givencrypt(struct skcipher_givcrypt_request *req)
80 {
81 struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
82 struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
83 struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);
84 struct ablkcipher_request *subreq;
85 crypto_completion_t complete;
86 void *data;
87 struct scatterlist *osrc, *odst;
88 struct scatterlist *dst;
89 struct page *srcp;
90 struct page *dstp;
91 u8 *giv;
92 u8 *vsrc;
93 u8 *vdst;
94 __be64 seq;
95 unsigned int ivsize;
96 unsigned int len;
97 int err;
98
99 subreq = (void *)(reqctx->tail + ctx->reqoff);
100 ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
101
102 giv = req->giv;
103 complete = req->creq.base.complete;
104 data = req->creq.base.data;
105
106 osrc = req->creq.src;
107 odst = req->creq.dst;
108 srcp = sg_page(osrc);
109 dstp = sg_page(odst);
110 vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + osrc->offset;
111 vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + odst->offset;
112
113 ivsize = crypto_ablkcipher_ivsize(geniv);
114
115 if (vsrc != giv + ivsize && vdst != giv + ivsize) {
116 giv = PTR_ALIGN((u8 *)reqctx->tail,
117 crypto_ablkcipher_alignmask(geniv) + 1);
118 complete = eseqiv_complete;
119 data = req;
120 }
121
122 ablkcipher_request_set_callback(subreq, req->creq.base.flags, complete,
123 data);
124
125 sg_init_table(reqctx->src, 2);
126 sg_set_buf(reqctx->src, giv, ivsize);
127 eseqiv_chain(reqctx->src, osrc, vsrc == giv + ivsize);
128
129 dst = reqctx->src;
130 if (osrc != odst) {
131 sg_init_table(reqctx->dst, 2);
132 sg_set_buf(reqctx->dst, giv, ivsize);
133 eseqiv_chain(reqctx->dst, odst, vdst == giv + ivsize);
134
135 dst = reqctx->dst;
136 }
137
138 ablkcipher_request_set_crypt(subreq, reqctx->src, dst,
139 req->creq.nbytes + ivsize,
140 req->creq.info);
141
142 memcpy(req->creq.info, ctx->salt, ivsize);
143
144 len = ivsize;
145 if (ivsize > sizeof(u64)) {
146 memset(req->giv, 0, ivsize - sizeof(u64));
147 len = sizeof(u64);
148 }
149 seq = cpu_to_be64(req->seq);
150 memcpy(req->giv + ivsize - len, &seq, len);
151
152 err = crypto_ablkcipher_encrypt(subreq);
153 if (err)
154 goto out;
155
156 if (giv != req->giv)
157 eseqiv_complete2(req);
158
159 out:
160 return err;
161 }
162
163 static int eseqiv_givencrypt_first(struct skcipher_givcrypt_request *req)
164 {
165 struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
166 struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
167 int err = 0;
168
169 spin_lock_bh(&ctx->lock);
170 if (crypto_ablkcipher_crt(geniv)->givencrypt != eseqiv_givencrypt_first)
171 goto unlock;
172
173 crypto_ablkcipher_crt(geniv)->givencrypt = eseqiv_givencrypt;
174 err = crypto_rng_get_bytes(crypto_default_rng, ctx->salt,
175 crypto_ablkcipher_ivsize(geniv));
176
177 unlock:
178 spin_unlock_bh(&ctx->lock);
179
180 if (err)
181 return err;
182
183 return eseqiv_givencrypt(req);
184 }
185
186 static int eseqiv_init(struct crypto_tfm *tfm)
187 {
188 struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
189 struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
190 unsigned long alignmask;
191 unsigned int reqsize;
192
193 spin_lock_init(&ctx->lock);
194
195 alignmask = crypto_tfm_ctx_alignment() - 1;
196 reqsize = sizeof(struct eseqiv_request_ctx);
197
198 if (alignmask & reqsize) {
199 alignmask &= reqsize;
200 alignmask--;
201 }
202
203 alignmask = ~alignmask;
204 alignmask &= crypto_ablkcipher_alignmask(geniv);
205
206 reqsize += alignmask;
207 reqsize += crypto_ablkcipher_ivsize(geniv);
208 reqsize = ALIGN(reqsize, crypto_tfm_ctx_alignment());
209
210 ctx->reqoff = reqsize - sizeof(struct eseqiv_request_ctx);
211
212 tfm->crt_ablkcipher.reqsize = reqsize +
213 sizeof(struct ablkcipher_request);
214
215 return skcipher_geniv_init(tfm);
216 }
217
218 static struct crypto_template eseqiv_tmpl;
219
220 static struct crypto_instance *eseqiv_alloc(struct rtattr **tb)
221 {
222 struct crypto_instance *inst;
223 int err;
224
225 err = crypto_get_default_rng();
226 if (err)
227 return ERR_PTR(err);
228
229 inst = skcipher_geniv_alloc(&eseqiv_tmpl, tb, 0, 0);
230 if (IS_ERR(inst))
231 goto put_rng;
232
233 err = -EINVAL;
234 if (inst->alg.cra_ablkcipher.ivsize != inst->alg.cra_blocksize)
235 goto free_inst;
236
237 inst->alg.cra_ablkcipher.givencrypt = eseqiv_givencrypt_first;
238
239 inst->alg.cra_init = eseqiv_init;
240 inst->alg.cra_exit = skcipher_geniv_exit;
241
242 inst->alg.cra_ctxsize = sizeof(struct eseqiv_ctx);
243 inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
244
245 out:
246 return inst;
247
248 free_inst:
249 skcipher_geniv_free(inst);
250 inst = ERR_PTR(err);
251 put_rng:
252 crypto_put_default_rng();
253 goto out;
254 }
255
256 static void eseqiv_free(struct crypto_instance *inst)
257 {
258 skcipher_geniv_free(inst);
259 crypto_put_default_rng();
260 }
261
262 static struct crypto_template eseqiv_tmpl = {
263 .name = "eseqiv",
264 .alloc = eseqiv_alloc,
265 .free = eseqiv_free,
266 .module = THIS_MODULE,
267 };
268
269 static int __init eseqiv_module_init(void)
270 {
271 return crypto_register_template(&eseqiv_tmpl);
272 }
273
274 static void __exit eseqiv_module_exit(void)
275 {
276 crypto_unregister_template(&eseqiv_tmpl);
277 }
278
279 module_init(eseqiv_module_init);
280 module_exit(eseqiv_module_exit);
281
282 MODULE_LICENSE("GPL");
283 MODULE_DESCRIPTION("Encrypted Sequence Number IV Generator");
284
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