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/internal/skcipher.h>
   9 #include <linux/err.h>
  10 #include <linux/init.h>
  11 #include <linux/kernel.h>
  12 #include <linux/log2.h>
  13 #include <linux/module.h>
  14
  15 static int crypto_cbc_encrypt_segment(struct crypto_lskcipher *tfm,
  16                                       const u8 *src, u8 *dst, unsigned nbytes,
  17                                       u8 *iv)
  18 {
  19         unsigned int bsize = crypto_lskcipher_blocksize(tfm);
  20
  21         for (; nbytes >= bsize; src += bsize, dst += bsize, nbytes -= bsize) {
  22                 crypto_xor(iv, src, bsize);
  23                 crypto_lskcipher_encrypt(tfm, iv, dst, bsize, NULL);
  24                 memcpy(iv, dst, bsize);
  25         }
  26
  27         return nbytes;
  28 }
  29
  30 static int crypto_cbc_encrypt_inplace(struct crypto_lskcipher *tfm,
  31                                       u8 *src, unsigned nbytes, u8 *oiv)
  32 {
  33         unsigned int bsize = crypto_lskcipher_blocksize(tfm);
  34         u8 *iv = oiv;
  35
  36         if (nbytes < bsize)
  37                 goto out;
  38
  39         do {
  40                 crypto_xor(src, iv, bsize);
  41                 crypto_lskcipher_encrypt(tfm, src, src, bsize, NULL);
  42                 iv = src;
  43
  44                 src += bsize;
  45         } while ((nbytes -= bsize) >= bsize);
  46
  47         memcpy(oiv, iv, bsize);
  48
  49 out:
  50         return nbytes;
  51 }
  52
  53 static int crypto_cbc_encrypt(struct crypto_lskcipher *tfm, const u8 *src,
  54                               u8 *dst, unsigned len, u8 *iv, u32 flags)
  55 {
  56         struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
  57         bool final = flags & CRYPTO_LSKCIPHER_FLAG_FINAL;
  58         struct crypto_lskcipher *cipher = *ctx;
  59         int rem;
  60
  61         if (src == dst)
  62                 rem = crypto_cbc_encrypt_inplace(cipher, dst, len, iv);
  63         else
  64                 rem = crypto_cbc_encrypt_segment(cipher, src, dst, len, iv);
  65
  66         return rem && final ? -EINVAL : rem;
  67 }
  68
  69 static int crypto_cbc_decrypt_segment(struct crypto_lskcipher *tfm,
  70                                       const u8 *src, u8 *dst, unsigned nbytes,
  71                                       u8 *oiv)
  72 {
  73         unsigned int bsize = crypto_lskcipher_blocksize(tfm);
  74         const u8 *iv = oiv;
  75
  76         if (nbytes < bsize)
  77                 goto out;
  78
  79         do {
  80                 crypto_lskcipher_decrypt(tfm, src, dst, bsize, NULL);
  81                 crypto_xor(dst, iv, bsize);
  82                 iv = src;
  83
  84                 src += bsize;
  85                 dst += bsize;
  86         } while ((nbytes -= bsize) >= bsize);
  87
  88         memcpy(oiv, iv, bsize);
  89
  90 out:
  91         return nbytes;
  92 }
  93
  94 static int crypto_cbc_decrypt_inplace(struct crypto_lskcipher *tfm,
  95                                       u8 *src, unsigned nbytes, u8 *iv)
  96 {
  97         unsigned int bsize = crypto_lskcipher_blocksize(tfm);
  98         u8 last_iv[MAX_CIPHER_BLOCKSIZE];
  99
 100         if (nbytes < bsize)
 101                 goto out;
 102
 103         /* Start of the last block. */
 104         src += nbytes - (nbytes & (bsize - 1)) - bsize;
 105         memcpy(last_iv, src, bsize);
 106
 107         for (;;) {
 108                 crypto_lskcipher_decrypt(tfm, src, src, bsize, NULL);
 109                 if ((nbytes -= bsize) < bsize)
 110                         break;
 111                 crypto_xor(src, src - bsize, bsize);
 112                 src -= bsize;
 113         }
 114
 115         crypto_xor(src, iv, bsize);
 116         memcpy(iv, last_iv, bsize);
 117
 118 out:
 119         return nbytes;
 120 }
 121
 122 static int crypto_cbc_decrypt(struct crypto_lskcipher *tfm, const u8 *src,
 123                               u8 *dst, unsigned len, u8 *iv, u32 flags)
 124 {
 125         struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
 126         bool final = flags & CRYPTO_LSKCIPHER_FLAG_FINAL;
 127         struct crypto_lskcipher *cipher = *ctx;
 128         int rem;
 129
 130         if (src == dst)
 131                 rem = crypto_cbc_decrypt_inplace(cipher, dst, len, iv);
 132         else
 133                 rem = crypto_cbc_decrypt_segment(cipher, src, dst, len, iv);
 134
 135         return rem && final ? -EINVAL : rem;
 136 }
 137
 138 static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
 139 {
 140         struct lskcipher_instance *inst;
 141         int err;
 142
 143         inst = lskcipher_alloc_instance_simple(tmpl, tb);
 144         if (IS_ERR(inst))
 145                 return PTR_ERR(inst);
 146
 147         err = -EINVAL;
 148         if (!is_power_of_2(inst->alg.co.base.cra_blocksize))
 149                 goto out_free_inst;
 150
 151         inst->alg.encrypt = crypto_cbc_encrypt;
 152         inst->alg.decrypt = crypto_cbc_decrypt;
 153
 154         err = lskcipher_register_instance(tmpl, inst);
 155         if (err) {
 156 out_free_inst:
 157                 inst->free(inst);
 158         }
 159
 160         return err;
 161 }
 162
 163 static struct crypto_template crypto_cbc_tmpl = {
 164         .name = "cbc",
 165         .create = crypto_cbc_create,
 166         .module = THIS_MODULE,
 167 };
 168
 169 static int __init crypto_cbc_module_init(void)
 170 {
 171         return crypto_register_template(&crypto_cbc_tmpl);
 172 }
 173
 174 static void __exit crypto_cbc_module_exit(void)
 175 {
 176         crypto_unregister_template(&crypto_cbc_tmpl);
 177 }
 178
 179 subsys_initcall(crypto_cbc_module_init);
 180 module_exit(crypto_cbc_module_exit);
 181
 182 MODULE_LICENSE("GPL");
 183 MODULE_DESCRIPTION("CBC block cipher mode of operation");
 184 MODULE_ALIAS_CRYPTO("cbc");