linux/crypto/eseqiv.c
<<
>>
Prefs
   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");
 270
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.