crypto/cbc.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * CBC: Cipher Block Chaining mode
   4  *
   5  * Copyright (c) 2006-2016 Herbert Xu <herbert@gondor.apana.org.au>
   6  */
   7
   8 #include <crypto/algapi.h>
   9 #include <crypto/internal/cipher.h>
  10 #include <crypto/internal/skcipher.h>
  11 #include <linux/err.h>
  12 #include <linux/init.h>
  13 #include <linux/kernel.h>
  14 #include <linux/log2.h>
  15 #include <linux/module.h>
  16
  17 static int crypto_cbc_encrypt_segment(struct skcipher_walk *walk,
  18                                       struct crypto_skcipher *skcipher)
  19 {
  20         unsigned int bsize = crypto_skcipher_blocksize(skcipher);
  21         void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  22         unsigned int nbytes = walk->nbytes;
  23         u8 *src = walk->src.virt.addr;
  24         u8 *dst = walk->dst.virt.addr;
  25         struct crypto_cipher *cipher;
  26         struct crypto_tfm *tfm;
  27         u8 *iv = walk->iv;
  28
  29         cipher = skcipher_cipher_simple(skcipher);
  30         tfm = crypto_cipher_tfm(cipher);
  31         fn = crypto_cipher_alg(cipher)->cia_encrypt;
  32
  33         do {
  34                 crypto_xor(iv, src, bsize);
  35                 fn(tfm, dst, iv);
  36                 memcpy(iv, dst, bsize);
  37
  38                 src += bsize;
  39                 dst += bsize;
  40         } while ((nbytes -= bsize) >= bsize);
  41
  42         return nbytes;
  43 }
  44
  45 static int crypto_cbc_encrypt_inplace(struct skcipher_walk *walk,
  46                                       struct crypto_skcipher *skcipher)
  47 {
  48         unsigned int bsize = crypto_skcipher_blocksize(skcipher);
  49         void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  50         unsigned int nbytes = walk->nbytes;
  51         u8 *src = walk->src.virt.addr;
  52         struct crypto_cipher *cipher;
  53         struct crypto_tfm *tfm;
  54         u8 *iv = walk->iv;
  55
  56         cipher = skcipher_cipher_simple(skcipher);
  57         tfm = crypto_cipher_tfm(cipher);
  58         fn = crypto_cipher_alg(cipher)->cia_encrypt;
  59
  60         do {
  61                 crypto_xor(src, iv, bsize);
  62                 fn(tfm, src, src);
  63                 iv = src;
  64
  65                 src += bsize;
  66         } while ((nbytes -= bsize) >= bsize);
  67
  68         memcpy(walk->iv, iv, bsize);
  69
  70         return nbytes;
  71 }
  72
  73 static int crypto_cbc_encrypt(struct skcipher_request *req)
  74 {
  75         struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
  76         struct skcipher_walk walk;
  77         int err;
  78
  79         err = skcipher_walk_virt(&walk, req, false);
  80
  81         while (walk.nbytes) {
  82                 if (walk.src.virt.addr == walk.dst.virt.addr)
  83                         err = crypto_cbc_encrypt_inplace(&walk, skcipher);
  84                 else
  85                         err = crypto_cbc_encrypt_segment(&walk, skcipher);
  86                 err = skcipher_walk_done(&walk, err);
  87         }
  88
  89         return err;
  90 }
  91
  92 static int crypto_cbc_decrypt_segment(struct skcipher_walk *walk,
  93                                       struct crypto_skcipher *skcipher)
  94 {
  95         unsigned int bsize = crypto_skcipher_blocksize(skcipher);
  96         void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  97         unsigned int nbytes = walk->nbytes;
  98         u8 *src = walk->src.virt.addr;
  99         u8 *dst = walk->dst.virt.addr;
 100         struct crypto_cipher *cipher;
 101         struct crypto_tfm *tfm;
 102         u8 *iv = walk->iv;
 103
 104         cipher = skcipher_cipher_simple(skcipher);
 105         tfm = crypto_cipher_tfm(cipher);
 106         fn = crypto_cipher_alg(cipher)->cia_decrypt;
 107
 108         do {
 109                 fn(tfm, dst, src);
 110                 crypto_xor(dst, iv, bsize);
 111                 iv = src;
 112
 113                 src += bsize;
 114                 dst += bsize;
 115         } while ((nbytes -= bsize) >= bsize);
 116
 117         memcpy(walk->iv, iv, bsize);
 118
 119         return nbytes;
 120 }
 121
 122 static int crypto_cbc_decrypt_inplace(struct skcipher_walk *walk,
 123                                       struct crypto_skcipher *skcipher)
 124 {
 125         unsigned int bsize = crypto_skcipher_blocksize(skcipher);
 126         void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
 127         unsigned int nbytes = walk->nbytes;
 128         u8 *src = walk->src.virt.addr;
 129         u8 last_iv[MAX_CIPHER_BLOCKSIZE];
 130         struct crypto_cipher *cipher;
 131         struct crypto_tfm *tfm;
 132
 133         cipher = skcipher_cipher_simple(skcipher);
 134         tfm = crypto_cipher_tfm(cipher);
 135         fn = crypto_cipher_alg(cipher)->cia_decrypt;
 136
 137         /* Start of the last block. */
 138         src += nbytes - (nbytes & (bsize - 1)) - bsize;
 139         memcpy(last_iv, src, bsize);
 140
 141         for (;;) {
 142                 fn(tfm, src, src);
 143                 if ((nbytes -= bsize) < bsize)
 144                         break;
 145                 crypto_xor(src, src - bsize, bsize);
 146                 src -= bsize;
 147         }
 148
 149         crypto_xor(src, walk->iv, bsize);
 150         memcpy(walk->iv, last_iv, bsize);
 151
 152         return nbytes;
 153 }
 154
 155 static int crypto_cbc_decrypt(struct skcipher_request *req)
 156 {
 157         struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
 158         struct skcipher_walk walk;
 159         int err;
 160
 161         err = skcipher_walk_virt(&walk, req, false);
 162
 163         while (walk.nbytes) {
 164                 if (walk.src.virt.addr == walk.dst.virt.addr)
 165                         err = crypto_cbc_decrypt_inplace(&walk, skcipher);
 166                 else
 167                         err = crypto_cbc_decrypt_segment(&walk, skcipher);
 168                 err = skcipher_walk_done(&walk, err);
 169         }
 170
 171         return err;
 172 }
 173
 174 static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
 175 {
 176         struct skcipher_instance *inst;
 177         struct crypto_alg *alg;
 178         int err;
 179
 180         inst = skcipher_alloc_instance_simple(tmpl, tb);
 181         if (IS_ERR(inst))
 182                 return PTR_ERR(inst);
 183
 184         alg = skcipher_ialg_simple(inst);
 185
 186         err = -EINVAL;
 187         if (!is_power_of_2(alg->cra_blocksize))
 188                 goto out_free_inst;
 189
 190         inst->alg.encrypt = crypto_cbc_encrypt;
 191         inst->alg.decrypt = crypto_cbc_decrypt;
 192
 193         err = skcipher_register_instance(tmpl, inst);
 194         if (err) {
 195 out_free_inst:
 196                 inst->free(inst);
 197         }
 198
 199         return err;
 200 }
 201
 202 static struct crypto_template crypto_cbc_tmpl = {
 203         .name = "cbc",
 204         .create = crypto_cbc_create,
 205         .module = THIS_MODULE,
 206 };
 207
 208 static int __init crypto_cbc_module_init(void)
 209 {
 210         return crypto_register_template(&crypto_cbc_tmpl);
 211 }
 212
 213 static void __exit crypto_cbc_module_exit(void)
 214 {
 215         crypto_unregister_template(&crypto_cbc_tmpl);
 216 }
 217
 218 subsys_initcall(crypto_cbc_module_init);
 219 module_exit(crypto_cbc_module_exit);
 220
 221 MODULE_LICENSE("GPL");
 222 MODULE_DESCRIPTION("CBC block cipher mode of operation");
 223 MODULE_ALIAS_CRYPTO("cbc");