| 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 | 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) { |
| 159 | out_free_inst: |
| 160 | inst->free(inst); |
| 161 | } |
| 162 | |
| 163 | return err; |
| 164 | } |
| 165 | |
| 166 | static struct crypto_template crypto_cbc_tmpl = { |
| 167 | .name = "cbc", |
| 168 | .create = crypto_cbc_create, |
| 169 | .module = THIS_MODULE, |
| 170 | }; |
| 171 | |
| 172 | static int __init crypto_cbc_module_init(void) |
| 173 | { |
| 174 | return crypto_register_template(&crypto_cbc_tmpl); |
| 175 | } |
| 176 | |
| 177 | static void __exit crypto_cbc_module_exit(void) |
| 178 | { |
| 179 | crypto_unregister_template(&crypto_cbc_tmpl); |
| 180 | } |
| 181 | |
| 182 | subsys_initcall(crypto_cbc_module_init); |
| 183 | module_exit(crypto_cbc_module_exit); |
| 184 | |
| 185 | MODULE_LICENSE("GPL"); |
| 186 | MODULE_DESCRIPTION("CBC block cipher mode of operation"); |
| 187 | MODULE_ALIAS_CRYPTO("cbc"); |