// SPDX-License-Identifier: GPL-2.0-or-later /* * CBC: Cipher Block Chaining mode * * Copyright (c) 2006-2016 Herbert Xu <herbert@gondor.apana.org.au> */ #include <crypto/algapi.h> #include <crypto/internal/cipher.h> #include <crypto/internal/skcipher.h> #include <linux/err.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/log2.h> #include <linux/module.h> static int crypto_cbc_encrypt_segment(struct skcipher_walk *walk, struct crypto_skcipher *skcipher) { unsigned int bsize = crypto_skcipher_blocksize(skcipher); void (*fn)(struct crypto_tfm *, u8 *, const u8 *); unsigned int nbytes = walk->nbytes; u8 *src = walk->src.virt.addr; u8 *dst = walk->dst.virt.addr; struct crypto_cipher *cipher; struct crypto_tfm *tfm; u8 *iv = walk->iv; cipher = skcipher_cipher_simple(skcipher); tfm = crypto_cipher_tfm(cipher); fn = crypto_cipher_alg(cipher)->cia_encrypt; do { crypto_xor(iv, src, bsize); fn(tfm, dst, iv); memcpy(iv, dst, bsize); src += bsize; dst += bsize; } while ((nbytes -= bsize) >= bsize); return nbytes; } static int crypto_cbc_encrypt_inplace(struct skcipher_walk *walk, struct crypto_skcipher *skcipher) { unsigned int bsize = crypto_skcipher_blocksize(skcipher); void (*fn)(struct crypto_tfm *, u8 *, const u8 *); unsigned int nbytes = walk->nbytes; u8 *src = walk->src.virt.addr; struct crypto_cipher *cipher; struct crypto_tfm *tfm; u8 *iv = walk->iv; cipher = skcipher_cipher_simple(skcipher); tfm = crypto_cipher_tfm(cipher); fn = crypto_cipher_alg(cipher)->cia_encrypt; do { crypto_xor(src, iv, bsize); fn(tfm, src, src); iv = src; src += bsize; } while ((nbytes -= bsize) >= bsize); memcpy(walk->iv, iv, bsize); return nbytes; } static int crypto_cbc_encrypt(struct skcipher_request *req) { struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req); struct skcipher_walk walk; int err; err = skcipher_walk_virt(&walk, req, false); while (walk.nbytes) { if (walk.src.virt.addr == walk.dst.virt.addr) err = crypto_cbc_encrypt_inplace(&walk, skcipher); else err = crypto_cbc_encrypt_segment(&walk, skcipher); err = skcipher_walk_done(&walk, err); } return err; } static int crypto_cbc_decrypt_segment(struct skcipher_walk *walk, struct crypto_skcipher *skcipher) { unsigned int bsize = crypto_skcipher_blocksize(skcipher); void (*fn)(struct crypto_tfm *, u8 *, const u8 *); unsigned int nbytes = walk->nbytes; u8 *src = walk->src.virt.addr; u8 *dst = walk->dst.virt.addr; struct crypto_cipher *cipher; struct crypto_tfm *tfm; u8 *iv = walk->iv; cipher = skcipher_cipher_simple(skcipher); tfm = crypto_cipher_tfm(cipher); fn = crypto_cipher_alg(cipher)->cia_decrypt; do { fn(tfm, dst, src); crypto_xor(dst, iv, bsize); iv = src; src += bsize; dst += bsize; } while ((nbytes -= bsize) >= bsize); memcpy(walk->iv, iv, bsize); return nbytes; } static int crypto_cbc_decrypt_inplace(struct skcipher_walk *walk, struct crypto_skcipher *skcipher) { unsigned int bsize = crypto_skcipher_blocksize(skcipher); void (*fn)(struct crypto_tfm *, u8 *, const u8 *); unsigned int nbytes = walk->nbytes; u8 *src = walk->src.virt.addr; u8 last_iv[MAX_CIPHER_BLOCKSIZE]; struct crypto_cipher *cipher; struct crypto_tfm *tfm; cipher = skcipher_cipher_simple(skcipher); tfm = crypto_cipher_tfm(cipher); fn = crypto_cipher_alg(cipher)->cia_decrypt; /* Start of the last block. */ src += nbytes - (nbytes & (bsize - 1)) - bsize; memcpy(last_iv, src, bsize); for (;;) { fn(tfm, src, src); if ((nbytes -= bsize) < bsize) break; crypto_xor(src, src - bsize, bsize); src -= bsize; } crypto_xor(src, walk->iv, bsize); memcpy(walk->iv, last_iv, bsize); return nbytes; } static int crypto_cbc_decrypt(struct skcipher_request *req) { struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req); struct skcipher_walk walk; int err; err = skcipher_walk_virt(&walk, req, false); while (walk.nbytes) { if (walk.src.virt.addr == walk.dst.virt.addr) err = crypto_cbc_decrypt_inplace(&walk, skcipher); else err = crypto_cbc_decrypt_segment(&walk, skcipher); err = skcipher_walk_done(&walk, err); } return err; } static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb) { struct skcipher_instance *inst; struct crypto_alg *alg; int err; inst = skcipher_alloc_instance_simple(tmpl, tb); if (IS_ERR(inst)) return PTR_ERR(inst); alg = skcipher_ialg_simple(inst); err = -EINVAL; if (!is_power_of_2(alg->cra_blocksize)) goto out_free_inst; inst->alg.encrypt = crypto_cbc_encrypt; inst->alg.decrypt = crypto_cbc_decrypt; err = skcipher_register_instance(tmpl, inst); if (err) { out_free_inst: inst->free(inst); } return err; } static struct crypto_template crypto_cbc_tmpl = { .name = "cbc", .create = crypto_cbc_create, .module = THIS_MODULE, }; static int __init crypto_cbc_module_init(void) { return crypto_register_template(&crypto_cbc_tmpl); } static void __exit crypto_cbc_module_exit(void) { crypto_unregister_template(&crypto_cbc_tmpl); } subsys_initcall(crypto_cbc_module_init); module_exit(crypto_cbc_module_exit); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("CBC block cipher mode of operation"); MODULE_ALIAS_CRYPTO("cbc");