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/skcipher.h>
  14 #include <linux/err.h>
  15 #include <linux/init.h>
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18
  19 static int crypto_pcbc_encrypt_segment(struct skcipher_request *req,
  20                                        struct skcipher_walk *walk,
  21                                        struct crypto_cipher *tfm)
  22 {
  23         int bsize = crypto_cipher_blocksize(tfm);
  24         unsigned int nbytes = walk->nbytes;
  25         u8 *src = walk->src.virt.addr;
  26         u8 *dst = walk->dst.virt.addr;
  27         u8 * const iv = walk->iv;
  28
  29         do {
  30                 crypto_xor(iv, src, bsize);
  31                 crypto_cipher_encrypt_one(tfm, dst, iv);
  32                 crypto_xor_cpy(iv, dst, src, bsize);
  33
  34                 src += bsize;
  35                 dst += bsize;
  36         } while ((nbytes -= bsize) >= bsize);
  37
  38         return nbytes;
  39 }
  40
  41 static int crypto_pcbc_encrypt_inplace(struct skcipher_request *req,
  42                                        struct skcipher_walk *walk,
  43                                        struct crypto_cipher *tfm)
  44 {
  45         int bsize = crypto_cipher_blocksize(tfm);
  46         unsigned int nbytes = walk->nbytes;
  47         u8 *src = walk->src.virt.addr;
  48         u8 * const iv = walk->iv;
  49         u8 tmpbuf[MAX_CIPHER_BLOCKSIZE];
  50
  51         do {
  52                 memcpy(tmpbuf, src, bsize);
  53                 crypto_xor(iv, src, bsize);
  54                 crypto_cipher_encrypt_one(tfm, src, iv);
  55                 crypto_xor_cpy(iv, tmpbuf, src, bsize);
  56
  57                 src += bsize;
  58         } while ((nbytes -= bsize) >= bsize);
  59
  60         return nbytes;
  61 }
  62
  63 static int crypto_pcbc_encrypt(struct skcipher_request *req)
  64 {
  65         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  66         struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
  67         struct skcipher_walk walk;
  68         unsigned int nbytes;
  69         int err;
  70
  71         err = skcipher_walk_virt(&walk, req, false);
  72
  73         while ((nbytes = walk.nbytes)) {
  74                 if (walk.src.virt.addr == walk.dst.virt.addr)
  75                         nbytes = crypto_pcbc_encrypt_inplace(req, &walk,
  76                                                              cipher);
  77                 else
  78                         nbytes = crypto_pcbc_encrypt_segment(req, &walk,
  79                                                              cipher);
  80                 err = skcipher_walk_done(&walk, nbytes);
  81         }
  82
  83         return err;
  84 }
  85
  86 static int crypto_pcbc_decrypt_segment(struct skcipher_request *req,
  87                                        struct skcipher_walk *walk,
  88                                        struct crypto_cipher *tfm)
  89 {
  90         int bsize = crypto_cipher_blocksize(tfm);
  91         unsigned int nbytes = walk->nbytes;
  92         u8 *src = walk->src.virt.addr;
  93         u8 *dst = walk->dst.virt.addr;
  94         u8 * const iv = walk->iv;
  95
  96         do {
  97                 crypto_cipher_decrypt_one(tfm, dst, src);
  98                 crypto_xor(dst, iv, bsize);
  99                 crypto_xor_cpy(iv, dst, src, bsize);
 100
 101                 src += bsize;
 102                 dst += bsize;
 103         } while ((nbytes -= bsize) >= bsize);
 104
 105         return nbytes;
 106 }
 107
 108 static int crypto_pcbc_decrypt_inplace(struct skcipher_request *req,
 109                                        struct skcipher_walk *walk,
 110                                        struct crypto_cipher *tfm)
 111 {
 112         int bsize = crypto_cipher_blocksize(tfm);
 113         unsigned int nbytes = walk->nbytes;
 114         u8 *src = walk->src.virt.addr;
 115         u8 * const iv = walk->iv;
 116         u8 tmpbuf[MAX_CIPHER_BLOCKSIZE] __aligned(__alignof__(u32));
 117
 118         do {
 119                 memcpy(tmpbuf, src, bsize);
 120                 crypto_cipher_decrypt_one(tfm, src, src);
 121                 crypto_xor(src, iv, bsize);
 122                 crypto_xor_cpy(iv, src, tmpbuf, bsize);
 123
 124                 src += bsize;
 125         } while ((nbytes -= bsize) >= bsize);
 126
 127         return nbytes;
 128 }
 129
 130 static int crypto_pcbc_decrypt(struct skcipher_request *req)
 131 {
 132         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 133         struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
 134         struct skcipher_walk walk;
 135         unsigned int nbytes;
 136         int err;
 137
 138         err = skcipher_walk_virt(&walk, req, false);
 139
 140         while ((nbytes = walk.nbytes)) {
 141                 if (walk.src.virt.addr == walk.dst.virt.addr)
 142                         nbytes = crypto_pcbc_decrypt_inplace(req, &walk,
 143                                                              cipher);
 144                 else
 145                         nbytes = crypto_pcbc_decrypt_segment(req, &walk,
 146                                                              cipher);
 147                 err = skcipher_walk_done(&walk, nbytes);
 148         }
 149
 150         return err;
 151 }
 152
 153 static int crypto_pcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
 154 {
 155         struct skcipher_instance *inst;
 156         struct crypto_alg *alg;
 157         int err;
 158
 159         inst = skcipher_alloc_instance_simple(tmpl, tb, &alg);
 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         crypto_mod_put(alg);
 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");