crypto/pcbc.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * PCBC: Propagating Cipher Block Chaining mode
   4  *
   5  * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
   6  * Written by David Howells (dhowells@redhat.com)
   7  *
   8  * Derived from cbc.c
   9  * - Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
  10  */
  11
  12 #include <crypto/algapi.h>
  13 #include <crypto/internal/cipher.h>
  14 #include <crypto/internal/skcipher.h>
  15 #include <linux/err.h>
  16 #include <linux/init.h>
  17 #include <linux/kernel.h>
  18 #include <linux/module.h>
  19
  20 static int crypto_pcbc_encrypt_segment(struct skcipher_request *req,
  21                                        struct skcipher_walk *walk,
  22                                        struct crypto_cipher *tfm)
  23 {
  24         int bsize = crypto_cipher_blocksize(tfm);
  25         unsigned int nbytes = walk->nbytes;
  26         u8 *src = walk->src.virt.addr;
  27         u8 *dst = walk->dst.virt.addr;
  28         u8 * const iv = walk->iv;
  29
  30         do {
  31                 crypto_xor(iv, src, bsize);
  32                 crypto_cipher_encrypt_one(tfm, dst, iv);
  33                 crypto_xor_cpy(iv, dst, src, bsize);
  34
  35                 src += bsize;
  36                 dst += bsize;
  37         } while ((nbytes -= bsize) >= bsize);
  38
  39         return nbytes;
  40 }
  41
  42 static int crypto_pcbc_encrypt_inplace(struct skcipher_request *req,
  43                                        struct skcipher_walk *walk,
  44                                        struct crypto_cipher *tfm)
  45 {
  46         int bsize = crypto_cipher_blocksize(tfm);
  47         unsigned int nbytes = walk->nbytes;
  48         u8 *src = walk->src.virt.addr;
  49         u8 * const iv = walk->iv;
  50         u8 tmpbuf[MAX_CIPHER_BLOCKSIZE];
  51
  52         do {
  53                 memcpy(tmpbuf, src, bsize);
  54                 crypto_xor(iv, src, bsize);
  55                 crypto_cipher_encrypt_one(tfm, src, iv);
  56                 crypto_xor_cpy(iv, tmpbuf, src, bsize);
  57
  58                 src += bsize;
  59         } while ((nbytes -= bsize) >= bsize);
  60
  61         return nbytes;
  62 }
  63
  64 static int crypto_pcbc_encrypt(struct skcipher_request *req)
  65 {
  66         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  67         struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
  68         struct skcipher_walk walk;
  69         unsigned int nbytes;
  70         int err;
  71
  72         err = skcipher_walk_virt(&walk, req, false);
  73
  74         while ((nbytes = walk.nbytes)) {
  75                 if (walk.src.virt.addr == walk.dst.virt.addr)
  76                         nbytes = crypto_pcbc_encrypt_inplace(req, &walk,
  77                                                              cipher);
  78                 else
  79                         nbytes = crypto_pcbc_encrypt_segment(req, &walk,
  80                                                              cipher);
  81                 err = skcipher_walk_done(&walk, nbytes);
  82         }
  83
  84         return err;
  85 }
  86
  87 static int crypto_pcbc_decrypt_segment(struct skcipher_request *req,
  88                                        struct skcipher_walk *walk,
  89                                        struct crypto_cipher *tfm)
  90 {
  91         int bsize = crypto_cipher_blocksize(tfm);
  92         unsigned int nbytes = walk->nbytes;
  93         u8 *src = walk->src.virt.addr;
  94         u8 *dst = walk->dst.virt.addr;
  95         u8 * const iv = walk->iv;
  96
  97         do {
  98                 crypto_cipher_decrypt_one(tfm, dst, src);
  99                 crypto_xor(dst, iv, bsize);
 100                 crypto_xor_cpy(iv, dst, src, bsize);
 101
 102                 src += bsize;
 103                 dst += bsize;
 104         } while ((nbytes -= bsize) >= bsize);
 105
 106         return nbytes;
 107 }
 108
 109 static int crypto_pcbc_decrypt_inplace(struct skcipher_request *req,
 110                                        struct skcipher_walk *walk,
 111                                        struct crypto_cipher *tfm)
 112 {
 113         int bsize = crypto_cipher_blocksize(tfm);
 114         unsigned int nbytes = walk->nbytes;
 115         u8 *src = walk->src.virt.addr;
 116         u8 * const iv = walk->iv;
 117         u8 tmpbuf[MAX_CIPHER_BLOCKSIZE] __aligned(__alignof__(u32));
 118
 119         do {
 120                 memcpy(tmpbuf, src, bsize);
 121                 crypto_cipher_decrypt_one(tfm, src, src);
 122                 crypto_xor(src, iv, bsize);
 123                 crypto_xor_cpy(iv, src, tmpbuf, bsize);
 124
 125                 src += bsize;
 126         } while ((nbytes -= bsize) >= bsize);
 127
 128         return nbytes;
 129 }
 130
 131 static int crypto_pcbc_decrypt(struct skcipher_request *req)
 132 {
 133         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 134         struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
 135         struct skcipher_walk walk;
 136         unsigned int nbytes;
 137         int err;
 138
 139         err = skcipher_walk_virt(&walk, req, false);
 140
 141         while ((nbytes = walk.nbytes)) {
 142                 if (walk.src.virt.addr == walk.dst.virt.addr)
 143                         nbytes = crypto_pcbc_decrypt_inplace(req, &walk,
 144                                                              cipher);
 145                 else
 146                         nbytes = crypto_pcbc_decrypt_segment(req, &walk,
 147                                                              cipher);
 148                 err = skcipher_walk_done(&walk, nbytes);
 149         }
 150
 151         return err;
 152 }
 153
 154 static int crypto_pcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
 155 {
 156         struct skcipher_instance *inst;
 157         int err;
 158
 159         inst = skcipher_alloc_instance_simple(tmpl, tb);
 160         if (IS_ERR(inst))
 161                 return PTR_ERR(inst);
 162
 163         inst->alg.encrypt = crypto_pcbc_encrypt;
 164         inst->alg.decrypt = crypto_pcbc_decrypt;
 165
 166         err = skcipher_register_instance(tmpl, inst);
 167         if (err)
 168                 inst->free(inst);
 169
 170         return err;
 171 }
 172
 173 static struct crypto_template crypto_pcbc_tmpl = {
 174         .name = "pcbc",
 175         .create = crypto_pcbc_create,
 176         .module = THIS_MODULE,
 177 };
 178
 179 static int __init crypto_pcbc_module_init(void)
 180 {
 181         return crypto_register_template(&crypto_pcbc_tmpl);
 182 }
 183
 184 static void __exit crypto_pcbc_module_exit(void)
 185 {
 186         crypto_unregister_template(&crypto_pcbc_tmpl);
 187 }
 188
 189 subsys_initcall(crypto_pcbc_module_init);
 190 module_exit(crypto_pcbc_module_exit);
 191
 192 MODULE_LICENSE("GPL");
 193 MODULE_DESCRIPTION("PCBC block cipher mode of operation");
 194 MODULE_ALIAS_CRYPTO("pcbc");
 195 MODULE_IMPORT_NS(CRYPTO_INTERNAL);