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/scatterwalk.h>
  20 #include <linux/err.h>
  21 #include <linux/init.h>
  22 #include <linux/kernel.h>
  23 #include <linux/mm.h>
  24 #include <linux/module.h>
  25 #include <linux/random.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 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
  79 static 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         eseqiv_complete2(req);
 157
 158 out:
 159         return err;
 160 }
 161
 162 static int eseqiv_givencrypt_first(struct skcipher_givcrypt_request *req)
 163 {
 164         struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
 165         struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
 166
 167         spin_lock_bh(&ctx->lock);
 168         if (crypto_ablkcipher_crt(geniv)->givencrypt != eseqiv_givencrypt_first)
 169                 goto unlock;
 170
 171         crypto_ablkcipher_crt(geniv)->givencrypt = eseqiv_givencrypt;
 172         get_random_bytes(ctx->salt, crypto_ablkcipher_ivsize(geniv));
 173
 174 unlock:
 175         spin_unlock_bh(&ctx->lock);
 176
 177         return eseqiv_givencrypt(req);
 178 }
 179
 180 static int eseqiv_init(struct crypto_tfm *tfm)
 181 {
 182         struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
 183         struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
 184         unsigned long alignmask;
 185         unsigned int reqsize;
 186
 187         spin_lock_init(&ctx->lock);
 188
 189         alignmask = crypto_tfm_ctx_alignment() - 1;
 190         reqsize = sizeof(struct eseqiv_request_ctx);
 191
 192         if (alignmask & reqsize) {
 193                 alignmask &= reqsize;
 194                 alignmask--;
 195         }
 196
 197         alignmask = ~alignmask;
 198         alignmask &= crypto_ablkcipher_alignmask(geniv);
 199
 200         reqsize += alignmask;
 201         reqsize += crypto_ablkcipher_ivsize(geniv);
 202         reqsize = ALIGN(reqsize, crypto_tfm_ctx_alignment());
 203
 204         ctx->reqoff = reqsize - sizeof(struct eseqiv_request_ctx);
 205
 206         tfm->crt_ablkcipher.reqsize = reqsize +
 207                                       sizeof(struct ablkcipher_request);
 208
 209         return skcipher_geniv_init(tfm);
 210 }
 211
 212 static struct crypto_template eseqiv_tmpl;
 213
 214 static struct crypto_instance *eseqiv_alloc(struct rtattr **tb)
 215 {
 216         struct crypto_instance *inst;
 217         int err;
 218
 219         inst = skcipher_geniv_alloc(&eseqiv_tmpl, tb, 0, 0);
 220         if (IS_ERR(inst))
 221                 goto out;
 222
 223         err = -EINVAL;
 224         if (inst->alg.cra_ablkcipher.ivsize != inst->alg.cra_blocksize)
 225                 goto free_inst;
 226
 227         inst->alg.cra_ablkcipher.givencrypt = eseqiv_givencrypt_first;
 228
 229         inst->alg.cra_init = eseqiv_init;
 230         inst->alg.cra_exit = skcipher_geniv_exit;
 231
 232         inst->alg.cra_ctxsize = sizeof(struct eseqiv_ctx);
 233         inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
 234
 235 out:
 236         return inst;
 237
 238 free_inst:
 239         skcipher_geniv_free(inst);
 240         inst = ERR_PTR(err);
 241         goto out;
 242 }
 243
 244 static struct crypto_template eseqiv_tmpl = {
 245         .name = "eseqiv",
 246         .alloc = eseqiv_alloc,
 247         .free = skcipher_geniv_free,
 248         .module = THIS_MODULE,
 249 };
 250
 251 int __init eseqiv_module_init(void)
 252 {
 253         return crypto_register_template(&eseqiv_tmpl);
 254 }
 255
 256 void __exit eseqiv_module_exit(void)
 257 {
 258         crypto_unregister_template(&eseqiv_tmpl);
 259 }