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 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
79static 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
159out:
160    return err;
161}
162
163static 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
177unlock:
178    spin_unlock_bh(&ctx->lock);
179
180    if (err)
181        return err;
182
183    return eseqiv_givencrypt(req);
184}
185
186static 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
218static struct crypto_template eseqiv_tmpl;
219
220static 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
245out:
246    return inst;
247
248free_inst:
249    skcipher_geniv_free(inst);
250    inst = ERR_PTR(err);
251put_rng:
252    crypto_put_default_rng();
253    goto out;
254}
255
256static void eseqiv_free(struct crypto_instance *inst)
257{
258    skcipher_geniv_free(inst);
259    crypto_put_default_rng();
260}
261
262static struct crypto_template eseqiv_tmpl = {
263    .name = "eseqiv",
264    .alloc = eseqiv_alloc,
265    .free = eseqiv_free,
266    .module = THIS_MODULE,
267};
268
269static int __init eseqiv_module_init(void)
270{
271    return crypto_register_template(&eseqiv_tmpl);
272}
273
274static void __exit eseqiv_module_exit(void)
275{
276    crypto_unregister_template(&eseqiv_tmpl);
277}
278
279module_init(eseqiv_module_init);
280module_exit(eseqiv_module_exit);
281
282MODULE_LICENSE("GPL");
283MODULE_DESCRIPTION("Encrypted Sequence Number IV Generator");
284

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