crypto/pcbc.c

   1 /*
   2  * PCBC: Propagating Cipher Block Chaining mode
   3  *
   4  * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  *
   7  * Derived from cbc.c
   8  * - Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
   9  *
  10  * This program is free software; you can redistribute it and/or modify it
  11  * under the terms of the GNU General Public License as published by the Free
  12  * Software Foundation; either version 2 of the License, or (at your option)
  13  * any later version.
  14  *
  15  */
  16
  17 #include <crypto/algapi.h>
  18 #include <linux/err.h>
  19 #include <linux/init.h>
  20 #include <linux/kernel.h>
  21 #include <linux/module.h>
  22 #include <linux/scatterlist.h>
  23 #include <linux/slab.h>
  24
  25 struct crypto_pcbc_ctx {
  26         struct crypto_cipher *child;
  27 };
  28
  29 static int crypto_pcbc_setkey(struct crypto_tfm *parent, const u8 *key,
  30                               unsigned int keylen)
  31 {
  32         struct crypto_pcbc_ctx *ctx = crypto_tfm_ctx(parent);
  33         struct crypto_cipher *child = ctx->child;
  34         int err;
  35
  36         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  37         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  38                                 CRYPTO_TFM_REQ_MASK);
  39         err = crypto_cipher_setkey(child, key, keylen);
  40         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  41                              CRYPTO_TFM_RES_MASK);
  42         return err;
  43 }
  44
  45 static int crypto_pcbc_encrypt_segment(struct blkcipher_desc *desc,
  46                                        struct blkcipher_walk *walk,
  47                                        struct crypto_cipher *tfm)
  48 {
  49         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  50                 crypto_cipher_alg(tfm)->cia_encrypt;
  51         int bsize = crypto_cipher_blocksize(tfm);
  52         unsigned int nbytes = walk->nbytes;
  53         u8 *src = walk->src.virt.addr;
  54         u8 *dst = walk->dst.virt.addr;
  55         u8 *iv = walk->iv;
  56
  57         do {
  58                 crypto_xor(iv, src, bsize);
  59                 fn(crypto_cipher_tfm(tfm), dst, iv);
  60                 memcpy(iv, dst, bsize);
  61                 crypto_xor(iv, src, bsize);
  62
  63                 src += bsize;
  64                 dst += bsize;
  65         } while ((nbytes -= bsize) >= bsize);
  66
  67         return nbytes;
  68 }
  69
  70 static int crypto_pcbc_encrypt_inplace(struct blkcipher_desc *desc,
  71                                        struct blkcipher_walk *walk,
  72                                        struct crypto_cipher *tfm)
  73 {
  74         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  75                 crypto_cipher_alg(tfm)->cia_encrypt;
  76         int bsize = crypto_cipher_blocksize(tfm);
  77         unsigned int nbytes = walk->nbytes;
  78         u8 *src = walk->src.virt.addr;
  79         u8 *iv = walk->iv;
  80         u8 tmpbuf[bsize];
  81
  82         do {
  83                 memcpy(tmpbuf, src, bsize);
  84                 crypto_xor(iv, src, bsize);
  85                 fn(crypto_cipher_tfm(tfm), src, iv);
  86                 memcpy(iv, tmpbuf, bsize);
  87                 crypto_xor(iv, src, bsize);
  88
  89                 src += bsize;
  90         } while ((nbytes -= bsize) >= bsize);
  91
  92         memcpy(walk->iv, iv, bsize);
  93
  94         return nbytes;
  95 }
  96
  97 static int crypto_pcbc_encrypt(struct blkcipher_desc *desc,
  98                                struct scatterlist *dst, struct scatterlist *src,
  99                                unsigned int nbytes)
 100 {
 101         struct blkcipher_walk walk;
 102         struct crypto_blkcipher *tfm = desc->tfm;
 103         struct crypto_pcbc_ctx *ctx = crypto_blkcipher_ctx(tfm);
 104         struct crypto_cipher *child = ctx->child;
 105         int err;
 106
 107         blkcipher_walk_init(&walk, dst, src, nbytes);
 108         err = blkcipher_walk_virt(desc, &walk);
 109
 110         while ((nbytes = walk.nbytes)) {
 111                 if (walk.src.virt.addr == walk.dst.virt.addr)
 112                         nbytes = crypto_pcbc_encrypt_inplace(desc, &walk,
 113                                                              child);
 114                 else
 115                         nbytes = crypto_pcbc_encrypt_segment(desc, &walk,
 116                                                              child);
 117                 err = blkcipher_walk_done(desc, &walk, nbytes);
 118         }
 119
 120         return err;
 121 }
 122
 123 static int crypto_pcbc_decrypt_segment(struct blkcipher_desc *desc,
 124                                        struct blkcipher_walk *walk,
 125                                        struct crypto_cipher *tfm)
 126 {
 127         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
 128                 crypto_cipher_alg(tfm)->cia_decrypt;
 129         int bsize = crypto_cipher_blocksize(tfm);
 130         unsigned int nbytes = walk->nbytes;
 131         u8 *src = walk->src.virt.addr;
 132         u8 *dst = walk->dst.virt.addr;
 133         u8 *iv = walk->iv;
 134
 135         do {
 136                 fn(crypto_cipher_tfm(tfm), dst, src);
 137                 crypto_xor(dst, iv, bsize);
 138                 memcpy(iv, src, bsize);
 139                 crypto_xor(iv, dst, bsize);
 140
 141                 src += bsize;
 142                 dst += bsize;
 143         } while ((nbytes -= bsize) >= bsize);
 144
 145         memcpy(walk->iv, iv, bsize);
 146
 147         return nbytes;
 148 }
 149
 150 static int crypto_pcbc_decrypt_inplace(struct blkcipher_desc *desc,
 151                                        struct blkcipher_walk *walk,
 152                                        struct crypto_cipher *tfm)
 153 {
 154         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
 155                 crypto_cipher_alg(tfm)->cia_decrypt;
 156         int bsize = crypto_cipher_blocksize(tfm);
 157         unsigned int nbytes = walk->nbytes;
 158         u8 *src = walk->src.virt.addr;
 159         u8 *iv = walk->iv;
 160         u8 tmpbuf[bsize];
 161
 162         do {
 163                 memcpy(tmpbuf, src, bsize);
 164                 fn(crypto_cipher_tfm(tfm), src, src);
 165                 crypto_xor(src, iv, bsize);
 166                 memcpy(iv, tmpbuf, bsize);
 167                 crypto_xor(iv, src, bsize);
 168
 169                 src += bsize;
 170         } while ((nbytes -= bsize) >= bsize);
 171
 172         memcpy(walk->iv, iv, bsize);
 173
 174         return nbytes;
 175 }
 176
 177 static int crypto_pcbc_decrypt(struct blkcipher_desc *desc,
 178                                struct scatterlist *dst, struct scatterlist *src,
 179                                unsigned int nbytes)
 180 {
 181         struct blkcipher_walk walk;
 182         struct crypto_blkcipher *tfm = desc->tfm;
 183         struct crypto_pcbc_ctx *ctx = crypto_blkcipher_ctx(tfm);
 184         struct crypto_cipher *child = ctx->child;
 185         int err;
 186
 187         blkcipher_walk_init(&walk, dst, src, nbytes);
 188         err = blkcipher_walk_virt(desc, &walk);
 189
 190         while ((nbytes = walk.nbytes)) {
 191                 if (walk.src.virt.addr == walk.dst.virt.addr)
 192                         nbytes = crypto_pcbc_decrypt_inplace(desc, &walk,
 193                                                              child);
 194                 else
 195                         nbytes = crypto_pcbc_decrypt_segment(desc, &walk,
 196                                                              child);
 197                 err = blkcipher_walk_done(desc, &walk, nbytes);
 198         }
 199
 200         return err;
 201 }
 202
 203 static int crypto_pcbc_init_tfm(struct crypto_tfm *tfm)
 204 {
 205         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 206         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 207         struct crypto_pcbc_ctx *ctx = crypto_tfm_ctx(tfm);
 208         struct crypto_cipher *cipher;
 209
 210         cipher = crypto_spawn_cipher(spawn);
 211         if (IS_ERR(cipher))
 212                 return PTR_ERR(cipher);
 213
 214         ctx->child = cipher;
 215         return 0;
 216 }
 217
 218 static void crypto_pcbc_exit_tfm(struct crypto_tfm *tfm)
 219 {
 220         struct crypto_pcbc_ctx *ctx = crypto_tfm_ctx(tfm);
 221         crypto_free_cipher(ctx->child);
 222 }
 223
 224 static struct crypto_instance *crypto_pcbc_alloc(struct rtattr **tb)
 225 {
 226         struct crypto_instance *inst;
 227         struct crypto_alg *alg;
 228         int err;
 229
 230         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 231         if (err)
 232                 return ERR_PTR(err);
 233
 234         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 235                                   CRYPTO_ALG_TYPE_MASK);
 236         if (IS_ERR(alg))
 237                 return ERR_CAST(alg);
 238
 239         inst = crypto_alloc_instance("pcbc", alg);
 240         if (IS_ERR(inst))
 241                 goto out_put_alg;
 242
 243         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 244         inst->alg.cra_priority = alg->cra_priority;
 245         inst->alg.cra_blocksize = alg->cra_blocksize;
 246         inst->alg.cra_alignmask = alg->cra_alignmask;
 247         inst->alg.cra_type = &crypto_blkcipher_type;
 248
 249         /* We access the data as u32s when xoring. */
 250         inst->alg.cra_alignmask |= __alignof__(u32) - 1;
 251
 252         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 253         inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
 254         inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
 255
 256         inst->alg.cra_ctxsize = sizeof(struct crypto_pcbc_ctx);
 257
 258         inst->alg.cra_init = crypto_pcbc_init_tfm;
 259         inst->alg.cra_exit = crypto_pcbc_exit_tfm;
 260
 261         inst->alg.cra_blkcipher.setkey = crypto_pcbc_setkey;
 262         inst->alg.cra_blkcipher.encrypt = crypto_pcbc_encrypt;
 263         inst->alg.cra_blkcipher.decrypt = crypto_pcbc_decrypt;
 264
 265 out_put_alg:
 266         crypto_mod_put(alg);
 267         return inst;
 268 }
 269
 270 static void crypto_pcbc_free(struct crypto_instance *inst)
 271 {
 272         crypto_drop_spawn(crypto_instance_ctx(inst));
 273         kfree(inst);
 274 }
 275
 276 static struct crypto_template crypto_pcbc_tmpl = {
 277         .name = "pcbc",
 278         .alloc = crypto_pcbc_alloc,
 279         .free = crypto_pcbc_free,
 280         .module = THIS_MODULE,
 281 };
 282
 283 static int __init crypto_pcbc_module_init(void)
 284 {
 285         return crypto_register_template(&crypto_pcbc_tmpl);
 286 }
 287
 288 static void __exit crypto_pcbc_module_exit(void)
 289 {
 290         crypto_unregister_template(&crypto_pcbc_tmpl);
 291 }
 292
 293 module_init(crypto_pcbc_module_init);
 294 module_exit(crypto_pcbc_module_exit);
 295
 296 MODULE_LICENSE("GPL");
 297 MODULE_DESCRIPTION("PCBC block cipher algorithm");