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
eseqiv_complete2(struct skcipher_givcrypt_request * req)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
eseqiv_complete(struct crypto_async_request * base,int err)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
eseqiv_givencrypt(struct skcipher_givcrypt_request * req)65 static int eseqiv_givencrypt(struct skcipher_givcrypt_request *req)
66 {
67 struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
68 struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
69 struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);
70 struct ablkcipher_request *subreq;
71 crypto_completion_t compl;
72 void *data;
73 struct scatterlist *osrc, *odst;
74 struct scatterlist *dst;
75 struct page *srcp;
76 struct page *dstp;
77 u8 *giv;
78 u8 *vsrc;
79 u8 *vdst;
80 __be64 seq;
81 unsigned int ivsize;
82 unsigned int len;
83 int err;
84
85 subreq = (void *)(reqctx->tail + ctx->reqoff);
86 ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
87
88 giv = req->giv;
89 compl = req->creq.base.complete;
90 data = req->creq.base.data;
91
92 osrc = req->creq.src;
93 odst = req->creq.dst;
94 srcp = sg_page(osrc);
95 dstp = sg_page(odst);
96 vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + osrc->offset;
97 vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + odst->offset;
98
99 ivsize = crypto_ablkcipher_ivsize(geniv);
100
101 if (vsrc != giv + ivsize && vdst != giv + ivsize) {
102 giv = PTR_ALIGN((u8 *)reqctx->tail,
103 crypto_ablkcipher_alignmask(geniv) + 1);
104 compl = eseqiv_complete;
105 data = req;
106 }
107
108 ablkcipher_request_set_callback(subreq, req->creq.base.flags, compl,
109 data);
110
111 sg_init_table(reqctx->src, 2);
112 sg_set_buf(reqctx->src, giv, ivsize);
113 scatterwalk_crypto_chain(reqctx->src, osrc, vsrc == giv + ivsize, 2);
114
115 dst = reqctx->src;
116 if (osrc != odst) {
117 sg_init_table(reqctx->dst, 2);
118 sg_set_buf(reqctx->dst, giv, ivsize);
119 scatterwalk_crypto_chain(reqctx->dst, odst, vdst == giv + ivsize, 2);
120
121 dst = reqctx->dst;
122 }
123
124 ablkcipher_request_set_crypt(subreq, reqctx->src, dst,
125 req->creq.nbytes + ivsize,
126 req->creq.info);
127
128 memcpy(req->creq.info, ctx->salt, ivsize);
129
130 len = ivsize;
131 if (ivsize > sizeof(u64)) {
132 memset(req->giv, 0, ivsize - sizeof(u64));
133 len = sizeof(u64);
134 }
135 seq = cpu_to_be64(req->seq);
136 memcpy(req->giv + ivsize - len, &seq, len);
137
138 err = crypto_ablkcipher_encrypt(subreq);
139 if (err)
140 goto out;
141
142 if (giv != req->giv)
143 eseqiv_complete2(req);
144
145 out:
146 return err;
147 }
148
eseqiv_givencrypt_first(struct skcipher_givcrypt_request * req)149 static int eseqiv_givencrypt_first(struct skcipher_givcrypt_request *req)
150 {
151 struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
152 struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
153 int err = 0;
154
155 spin_lock_bh(&ctx->lock);
156 if (crypto_ablkcipher_crt(geniv)->givencrypt != eseqiv_givencrypt_first)
157 goto unlock;
158
159 crypto_ablkcipher_crt(geniv)->givencrypt = eseqiv_givencrypt;
160 err = crypto_rng_get_bytes(crypto_default_rng, ctx->salt,
161 crypto_ablkcipher_ivsize(geniv));
162
163 unlock:
164 spin_unlock_bh(&ctx->lock);
165
166 if (err)
167 return err;
168
169 return eseqiv_givencrypt(req);
170 }
171
eseqiv_init(struct crypto_tfm * tfm)172 static int eseqiv_init(struct crypto_tfm *tfm)
173 {
174 struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
175 struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
176 unsigned long alignmask;
177 unsigned int reqsize;
178
179 spin_lock_init(&ctx->lock);
180
181 alignmask = crypto_tfm_ctx_alignment() - 1;
182 reqsize = sizeof(struct eseqiv_request_ctx);
183
184 if (alignmask & reqsize) {
185 alignmask &= reqsize;
186 alignmask--;
187 }
188
189 alignmask = ~alignmask;
190 alignmask &= crypto_ablkcipher_alignmask(geniv);
191
192 reqsize += alignmask;
193 reqsize += crypto_ablkcipher_ivsize(geniv);
194 reqsize = ALIGN(reqsize, crypto_tfm_ctx_alignment());
195
196 ctx->reqoff = reqsize - sizeof(struct eseqiv_request_ctx);
197
198 tfm->crt_ablkcipher.reqsize = reqsize +
199 sizeof(struct ablkcipher_request);
200
201 return skcipher_geniv_init(tfm);
202 }
203
204 static struct crypto_template eseqiv_tmpl;
205
eseqiv_alloc(struct rtattr ** tb)206 static struct crypto_instance *eseqiv_alloc(struct rtattr **tb)
207 {
208 struct crypto_instance *inst;
209 int err;
210
211 err = crypto_get_default_rng();
212 if (err)
213 return ERR_PTR(err);
214
215 inst = skcipher_geniv_alloc(&eseqiv_tmpl, tb, 0, 0);
216 if (IS_ERR(inst))
217 goto put_rng;
218
219 err = -EINVAL;
220 if (inst->alg.cra_ablkcipher.ivsize != inst->alg.cra_blocksize)
221 goto free_inst;
222
223 inst->alg.cra_ablkcipher.givencrypt = eseqiv_givencrypt_first;
224
225 inst->alg.cra_init = eseqiv_init;
226 inst->alg.cra_exit = skcipher_geniv_exit;
227
228 inst->alg.cra_ctxsize = sizeof(struct eseqiv_ctx);
229 inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
230
231 out:
232 return inst;
233
234 free_inst:
235 skcipher_geniv_free(inst);
236 inst = ERR_PTR(err);
237 put_rng:
238 crypto_put_default_rng();
239 goto out;
240 }
241
eseqiv_free(struct crypto_instance * inst)242 static void eseqiv_free(struct crypto_instance *inst)
243 {
244 skcipher_geniv_free(inst);
245 crypto_put_default_rng();
246 }
247
248 static struct crypto_template eseqiv_tmpl = {
249 .name = "eseqiv",
250 .alloc = eseqiv_alloc,
251 .free = eseqiv_free,
252 .module = THIS_MODULE,
253 };
254
eseqiv_module_init(void)255 static int __init eseqiv_module_init(void)
256 {
257 return crypto_register_template(&eseqiv_tmpl);
258 }
259
eseqiv_module_exit(void)260 static void __exit eseqiv_module_exit(void)
261 {
262 crypto_unregister_template(&eseqiv_tmpl);
263 }
264
265 module_init(eseqiv_module_init);
266 module_exit(eseqiv_module_exit);
267
268 MODULE_LICENSE("GPL");
269 MODULE_DESCRIPTION("Encrypted Sequence Number IV Generator");
270 MODULE_ALIAS_CRYPTO("eseqiv");
271