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");