linux/crypto/eseqiv.c
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   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 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
  79static 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
 158out:
 159        return err;
 160}
 161
 162static 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        int err = 0;
 167
 168        spin_lock_bh(&ctx->lock);
 169        if (crypto_ablkcipher_crt(geniv)->givencrypt != eseqiv_givencrypt_first)
 170                goto unlock;
 171
 172        crypto_ablkcipher_crt(geniv)->givencrypt = eseqiv_givencrypt;
 173        err = crypto_rng_get_bytes(crypto_default_rng, ctx->salt,
 174                                   crypto_ablkcipher_ivsize(geniv));
 175
 176unlock:
 177        spin_unlock_bh(&ctx->lock);
 178
 179        if (err)
 180                return err;
 181
 182        return eseqiv_givencrypt(req);
 183}
 184
 185static int eseqiv_init(struct crypto_tfm *tfm)
 186{
 187        struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
 188        struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
 189        unsigned long alignmask;
 190        unsigned int reqsize;
 191
 192        spin_lock_init(&ctx->lock);
 193
 194        alignmask = crypto_tfm_ctx_alignment() - 1;
 195        reqsize = sizeof(struct eseqiv_request_ctx);
 196
 197        if (alignmask & reqsize) {
 198                alignmask &= reqsize;
 199                alignmask--;
 200        }
 201
 202        alignmask = ~alignmask;
 203        alignmask &= crypto_ablkcipher_alignmask(geniv);
 204
 205        reqsize += alignmask;
 206        reqsize += crypto_ablkcipher_ivsize(geniv);
 207        reqsize = ALIGN(reqsize, crypto_tfm_ctx_alignment());
 208
 209        ctx->reqoff = reqsize - sizeof(struct eseqiv_request_ctx);
 210
 211        tfm->crt_ablkcipher.reqsize = reqsize +
 212                                      sizeof(struct ablkcipher_request);
 213
 214        return skcipher_geniv_init(tfm);
 215}
 216
 217static struct crypto_template eseqiv_tmpl;
 218
 219static struct crypto_instance *eseqiv_alloc(struct rtattr **tb)
 220{
 221        struct crypto_instance *inst;
 222        int err;
 223
 224        err = crypto_get_default_rng();
 225        if (err)
 226                return ERR_PTR(err);
 227
 228        inst = skcipher_geniv_alloc(&eseqiv_tmpl, tb, 0, 0);
 229        if (IS_ERR(inst))
 230                goto put_rng;
 231
 232        err = -EINVAL;
 233        if (inst->alg.cra_ablkcipher.ivsize != inst->alg.cra_blocksize)
 234                goto free_inst;
 235
 236        inst->alg.cra_ablkcipher.givencrypt = eseqiv_givencrypt_first;
 237
 238        inst->alg.cra_init = eseqiv_init;
 239        inst->alg.cra_exit = skcipher_geniv_exit;
 240
 241        inst->alg.cra_ctxsize = sizeof(struct eseqiv_ctx);
 242        inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
 243
 244out:
 245        return inst;
 246
 247free_inst:
 248        skcipher_geniv_free(inst);
 249        inst = ERR_PTR(err);
 250put_rng:
 251        crypto_put_default_rng();
 252        goto out;
 253}
 254
 255static void eseqiv_free(struct crypto_instance *inst)
 256{
 257        skcipher_geniv_free(inst);
 258        crypto_put_default_rng();
 259}
 260
 261static struct crypto_template eseqiv_tmpl = {
 262        .name = "eseqiv",
 263        .alloc = eseqiv_alloc,
 264        .free = eseqiv_free,
 265        .module = THIS_MODULE,
 266};
 267
 268static int __init eseqiv_module_init(void)
 269{
 270        return crypto_register_template(&eseqiv_tmpl);
 271}
 272
 273static void __exit eseqiv_module_exit(void)
 274{
 275        crypto_unregister_template(&eseqiv_tmpl);
 276}
 277
 278module_init(eseqiv_module_init);
 279module_exit(eseqiv_module_exit);
 280
 281MODULE_LICENSE("GPL");
 282MODULE_DESCRIPTION("Encrypted Sequence Number IV Generator");
 283