Root/crypto/eseqiv.c

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
30struct eseqiv_request_ctx {
31    struct scatterlist src[2];
32    struct scatterlist dst[2];
33    char tail[];
34};
35
36struct eseqiv_ctx {
37    spinlock_t lock;
38    unsigned int reqoff;
39    char salt[];
40};
41
42static 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
52static 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
61out:
62    skcipher_givcrypt_complete(req, err);
63}
64
65static 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 complete;
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    complete = 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        complete = eseqiv_complete;
105        data = req;
106    }
107
108    ablkcipher_request_set_callback(subreq, req->creq.base.flags, complete,
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
145out:
146    return err;
147}
148
149static 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
163unlock:
164    spin_unlock_bh(&ctx->lock);
165
166    if (err)
167        return err;
168
169    return eseqiv_givencrypt(req);
170}
171
172static 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
204static struct crypto_template eseqiv_tmpl;
205
206static 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
231out:
232    return inst;
233
234free_inst:
235    skcipher_geniv_free(inst);
236    inst = ERR_PTR(err);
237put_rng:
238    crypto_put_default_rng();
239    goto out;
240}
241
242static void eseqiv_free(struct crypto_instance *inst)
243{
244    skcipher_geniv_free(inst);
245    crypto_put_default_rng();
246}
247
248static struct crypto_template eseqiv_tmpl = {
249    .name = "eseqiv",
250    .alloc = eseqiv_alloc,
251    .free = eseqiv_free,
252    .module = THIS_MODULE,
253};
254
255static int __init eseqiv_module_init(void)
256{
257    return crypto_register_template(&eseqiv_tmpl);
258}
259
260static void __exit eseqiv_module_exit(void)
261{
262    crypto_unregister_template(&eseqiv_tmpl);
263}
264
265module_init(eseqiv_module_init);
266module_exit(eseqiv_module_exit);
267
268MODULE_LICENSE("GPL");
269MODULE_DESCRIPTION("Encrypted Sequence Number IV Generator");
270

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