eseqiv.c 6.67 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
/*
 * eseqiv: Encrypted Sequence Number IV Generator
 *
 * This generator generates an IV based on a sequence number by xoring it
 * with a salt and then encrypting it with the same key as used to encrypt
 * the plain text.  This algorithm requires that the block size be equal
 * to the IV size.  It is mainly useful for CBC.
 *
 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 */

#include <crypto/internal/skcipher.h>
19
#include <crypto/rng.h>
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138
#include <crypto/scatterwalk.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/spinlock.h>
#include <linux/string.h>

struct eseqiv_request_ctx {
	struct scatterlist src[2];
	struct scatterlist dst[2];
	char tail[];
};

struct eseqiv_ctx {
	spinlock_t lock;
	unsigned int reqoff;
	char salt[];
};

static void eseqiv_complete2(struct skcipher_givcrypt_request *req)
{
	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
	struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);

	memcpy(req->giv, PTR_ALIGN((u8 *)reqctx->tail,
			 crypto_ablkcipher_alignmask(geniv) + 1),
	       crypto_ablkcipher_ivsize(geniv));
}

static void eseqiv_complete(struct crypto_async_request *base, int err)
{
	struct skcipher_givcrypt_request *req = base->data;

	if (err)
		goto out;

	eseqiv_complete2(req);

out:
	skcipher_givcrypt_complete(req, err);
}

static void eseqiv_chain(struct scatterlist *head, struct scatterlist *sg,
			 int chain)
{
	if (chain) {
		head->length += sg->length;
		sg = scatterwalk_sg_next(sg);
	}

	if (sg)
		scatterwalk_sg_chain(head, 2, sg);
	else
		sg_mark_end(head);
}

static int eseqiv_givencrypt(struct skcipher_givcrypt_request *req)
{
	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
	struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
	struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);
	struct ablkcipher_request *subreq;
	crypto_completion_t complete;
	void *data;
	struct scatterlist *osrc, *odst;
	struct scatterlist *dst;
	struct page *srcp;
	struct page *dstp;
	u8 *giv;
	u8 *vsrc;
	u8 *vdst;
	__be64 seq;
	unsigned int ivsize;
	unsigned int len;
	int err;

	subreq = (void *)(reqctx->tail + ctx->reqoff);
	ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));

	giv = req->giv;
	complete = req->creq.base.complete;
	data = req->creq.base.data;

	osrc = req->creq.src;
	odst = req->creq.dst;
	srcp = sg_page(osrc);
	dstp = sg_page(odst);
	vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + osrc->offset;
	vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + odst->offset;

	ivsize = crypto_ablkcipher_ivsize(geniv);

	if (vsrc != giv + ivsize && vdst != giv + ivsize) {
		giv = PTR_ALIGN((u8 *)reqctx->tail,
				crypto_ablkcipher_alignmask(geniv) + 1);
		complete = eseqiv_complete;
		data = req;
	}

	ablkcipher_request_set_callback(subreq, req->creq.base.flags, complete,
					data);

	sg_init_table(reqctx->src, 2);
	sg_set_buf(reqctx->src, giv, ivsize);
	eseqiv_chain(reqctx->src, osrc, vsrc == giv + ivsize);

	dst = reqctx->src;
	if (osrc != odst) {
		sg_init_table(reqctx->dst, 2);
		sg_set_buf(reqctx->dst, giv, ivsize);
		eseqiv_chain(reqctx->dst, odst, vdst == giv + ivsize);

		dst = reqctx->dst;
	}

	ablkcipher_request_set_crypt(subreq, reqctx->src, dst,
139 140
				     req->creq.nbytes + ivsize,
				     req->creq.info);
141 142 143 144 145 146 147 148 149 150 151 152 153 154 155

	memcpy(req->creq.info, ctx->salt, ivsize);

	len = ivsize;
	if (ivsize > sizeof(u64)) {
		memset(req->giv, 0, ivsize - sizeof(u64));
		len = sizeof(u64);
	}
	seq = cpu_to_be64(req->seq);
	memcpy(req->giv + ivsize - len, &seq, len);

	err = crypto_ablkcipher_encrypt(subreq);
	if (err)
		goto out;

156 157
	if (giv != req->giv)
		eseqiv_complete2(req);
158 159 160 161 162 163 164 165 166

out:
	return err;
}

static int eseqiv_givencrypt_first(struct skcipher_givcrypt_request *req)
{
	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
	struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
167
	int err = 0;
168 169 170 171 172 173

	spin_lock_bh(&ctx->lock);
	if (crypto_ablkcipher_crt(geniv)->givencrypt != eseqiv_givencrypt_first)
		goto unlock;

	crypto_ablkcipher_crt(geniv)->givencrypt = eseqiv_givencrypt;
174 175
	err = crypto_rng_get_bytes(crypto_default_rng, ctx->salt,
				   crypto_ablkcipher_ivsize(geniv));
176 177 178 179

unlock:
	spin_unlock_bh(&ctx->lock);

180 181 182
	if (err)
		return err;

183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224
	return eseqiv_givencrypt(req);
}

static int eseqiv_init(struct crypto_tfm *tfm)
{
	struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
	struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
	unsigned long alignmask;
	unsigned int reqsize;

	spin_lock_init(&ctx->lock);

	alignmask = crypto_tfm_ctx_alignment() - 1;
	reqsize = sizeof(struct eseqiv_request_ctx);

	if (alignmask & reqsize) {
		alignmask &= reqsize;
		alignmask--;
	}

	alignmask = ~alignmask;
	alignmask &= crypto_ablkcipher_alignmask(geniv);

	reqsize += alignmask;
	reqsize += crypto_ablkcipher_ivsize(geniv);
	reqsize = ALIGN(reqsize, crypto_tfm_ctx_alignment());

	ctx->reqoff = reqsize - sizeof(struct eseqiv_request_ctx);

	tfm->crt_ablkcipher.reqsize = reqsize +
				      sizeof(struct ablkcipher_request);

	return skcipher_geniv_init(tfm);
}

static struct crypto_template eseqiv_tmpl;

static struct crypto_instance *eseqiv_alloc(struct rtattr **tb)
{
	struct crypto_instance *inst;
	int err;

225 226 227 228
	err = crypto_get_default_rng();
	if (err)
		return ERR_PTR(err);

229 230
	inst = skcipher_geniv_alloc(&eseqiv_tmpl, tb, 0, 0);
	if (IS_ERR(inst))
231
		goto put_rng;
232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250

	err = -EINVAL;
	if (inst->alg.cra_ablkcipher.ivsize != inst->alg.cra_blocksize)
		goto free_inst;

	inst->alg.cra_ablkcipher.givencrypt = eseqiv_givencrypt_first;

	inst->alg.cra_init = eseqiv_init;
	inst->alg.cra_exit = skcipher_geniv_exit;

	inst->alg.cra_ctxsize = sizeof(struct eseqiv_ctx);
	inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;

out:
	return inst;

free_inst:
	skcipher_geniv_free(inst);
	inst = ERR_PTR(err);
251 252
put_rng:
	crypto_put_default_rng();
253 254 255
	goto out;
}

256 257 258 259 260 261
static void eseqiv_free(struct crypto_instance *inst)
{
	skcipher_geniv_free(inst);
	crypto_put_default_rng();
}

262 263 264
static struct crypto_template eseqiv_tmpl = {
	.name = "eseqiv",
	.alloc = eseqiv_alloc,
265
	.free = eseqiv_free,
266 267 268
	.module = THIS_MODULE,
};

269
static int __init eseqiv_module_init(void)
270 271 272 273
{
	return crypto_register_template(&eseqiv_tmpl);
}

274
static void __exit eseqiv_module_exit(void)
275 276 277
{
	crypto_unregister_template(&eseqiv_tmpl);
}
278 279 280 281 282 283

module_init(eseqiv_module_init);
module_exit(eseqiv_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Encrypted Sequence Number IV Generator");