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
  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
  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
  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
  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 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
 145 out:
 146         return err;
 147 }
 148
 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
 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
 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
 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
 255 static int __init eseqiv_module_init(void)
 256 {
 257         return crypto_register_template(&eseqiv_tmpl);
 258 }
 259
 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");