188 lines · c
1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * CBC: Cipher Block Chaining mode4 *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 15static 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 30static 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 49out:50 return nbytes;51}52 53static 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 else64 rem = crypto_cbc_encrypt_segment(cipher, src, dst, len, iv);65 66 return rem && final ? -EINVAL : rem;67}68 69static 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 90out:91 return nbytes;92}93 94static 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 118out:119 return nbytes;120}121 122static 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 else133 rem = crypto_cbc_decrypt_segment(cipher, src, dst, len, iv);134 135 return rem && final ? -EINVAL : rem;136}137 138static 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 if (inst->alg.co.statesize)152 goto out_free_inst;153 154 inst->alg.encrypt = crypto_cbc_encrypt;155 inst->alg.decrypt = crypto_cbc_decrypt;156 157 err = lskcipher_register_instance(tmpl, inst);158 if (err) {159out_free_inst:160 inst->free(inst);161 }162 163 return err;164}165 166static struct crypto_template crypto_cbc_tmpl = {167 .name = "cbc",168 .create = crypto_cbc_create,169 .module = THIS_MODULE,170};171 172static int __init crypto_cbc_module_init(void)173{174 return crypto_register_template(&crypto_cbc_tmpl);175}176 177static void __exit crypto_cbc_module_exit(void)178{179 crypto_unregister_template(&crypto_cbc_tmpl);180}181 182subsys_initcall(crypto_cbc_module_init);183module_exit(crypto_cbc_module_exit);184 185MODULE_LICENSE("GPL");186MODULE_DESCRIPTION("CBC block cipher mode of operation");187MODULE_ALIAS_CRYPTO("cbc");188