/* * CBC: Cipher Block Chaining mode * * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au> * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the Free * Software Foundation; either version 2 of the License, or (at your option) * any later version. * */ #include <crypto/algapi.h> #include <linux/err.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/log2.h> #include <linux/module.h> #include <linux/scatterlist.h> #include <linux/slab.h> struct crypto_cbc_ctx { struct crypto_cipher *child; }; static int crypto_cbc_setkey(struct crypto_tfm *parent, const u8 *key, unsigned int keylen) { struct crypto_cbc_ctx *ctx = crypto_tfm_ctx(parent); struct crypto_cipher *child = ctx->child; int err; crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) & CRYPTO_TFM_REQ_MASK); err = crypto_cipher_setkey(child, key, keylen); crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) & CRYPTO_TFM_RES_MASK); return err; } static int crypto_cbc_encrypt_segment(struct blkcipher_desc *desc, struct blkcipher_walk *walk, struct crypto_cipher *tfm) { void (*fn)(struct crypto_tfm *, u8 *, const u8 *) = crypto_cipher_alg(tfm)->cia_encrypt; int bsize = crypto_cipher_blocksize(tfm); unsigned int nbytes = walk->nbytes; u8 *src = walk->src.virt.addr; u8 *dst = walk->dst.virt.addr; u8 *iv = walk->iv; do { crypto_xor(iv, src, bsize); fn(crypto_cipher_tfm(tfm), dst, iv); memcpy(iv, dst, bsize); src += bsize; dst += bsize; } while ((nbytes -= bsize) >= bsize); return nbytes; } static int crypto_cbc_encrypt_inplace(struct blkcipher_desc *desc, struct blkcipher_walk *walk, struct crypto_cipher *tfm) { void (*fn)(struct crypto_tfm *, u8 *, const u8 *) = crypto_cipher_alg(tfm)->cia_encrypt; int bsize = crypto_cipher_blocksize(tfm); unsigned int nbytes = walk->nbytes; u8 *src = walk->src.virt.addr; u8 *iv = walk->iv; do { crypto_xor(src, iv, bsize); fn(crypto_cipher_tfm(tfm), src, src); iv = src; src += bsize; } while ((nbytes -= bsize) >= bsize); memcpy(walk->iv, iv, bsize); return nbytes; } static int crypto_cbc_encrypt(struct blkcipher_desc *desc, struct scatterlist *dst, struct scatterlist *src, unsigned int nbytes) { struct blkcipher_walk walk; struct crypto_blkcipher *tfm = desc->tfm; struct crypto_cbc_ctx *ctx = crypto_blkcipher_ctx(tfm); struct crypto_cipher *child = ctx->child; int err; blkcipher_walk_init(&walk, dst, src, nbytes); err = blkcipher_walk_virt(desc, &walk); while ((nbytes = walk.nbytes)) { if (walk.src.virt.addr == walk.dst.virt.addr) nbytes = crypto_cbc_encrypt_inplace(desc, &walk, child); else nbytes = crypto_cbc_encrypt_segment(desc, &walk, child); err = blkcipher_walk_done(desc, &walk, nbytes); } return err; } static int crypto_cbc_decrypt_segment(struct blkcipher_desc *desc, struct blkcipher_walk *walk, struct crypto_cipher *tfm) { void (*fn)(struct crypto_tfm *, u8 *, const u8 *) = crypto_cipher_alg(tfm)->cia_decrypt; int bsize = crypto_cipher_blocksize(tfm); unsigned int nbytes = walk->nbytes; u8 *src = walk->src.virt.addr; u8 *dst = walk->dst.virt.addr; u8 *iv = walk->iv; do { fn(crypto_cipher_tfm(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 blkcipher_desc *desc, struct blkcipher_walk *walk, struct crypto_cipher *tfm) { void (*fn)(struct crypto_tfm *, u8 *, const u8 *) = crypto_cipher_alg(tfm)->cia_decrypt; int bsize = crypto_cipher_blocksize(tfm); unsigned int nbytes = walk->nbytes; u8 *src = walk->src.virt.addr; u8 last_iv[bsize]; /* Start of the last block. */ src += nbytes - (nbytes & (bsize - 1)) - bsize; memcpy(last_iv, src, bsize); for (;;) { fn(crypto_cipher_tfm(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 blkcipher_desc *desc, struct scatterlist *dst, struct scatterlist *src, unsigned int nbytes) { struct blkcipher_walk walk; struct crypto_blkcipher *tfm = desc->tfm; struct crypto_cbc_ctx *ctx = crypto_blkcipher_ctx(tfm); struct crypto_cipher *child = ctx->child; int err; blkcipher_walk_init(&walk, dst, src, nbytes); err = blkcipher_walk_virt(desc, &walk); while ((nbytes = walk.nbytes)) { if (walk.src.virt.addr == walk.dst.virt.addr) nbytes = crypto_cbc_decrypt_inplace(desc, &walk, child); else nbytes = crypto_cbc_decrypt_segment(desc, &walk, child); err = blkcipher_walk_done(desc, &walk, nbytes); } return err; } static int crypto_cbc_init_tfm(struct crypto_tfm *tfm) { struct crypto_instance *inst = (void *)tfm->__crt_alg; struct crypto_spawn *spawn = crypto_instance_ctx(inst); struct crypto_cbc_ctx *ctx = crypto_tfm_ctx(tfm); struct crypto_cipher *cipher; cipher = crypto_spawn_cipher(spawn); if (IS_ERR(cipher)) return PTR_ERR(cipher); ctx->child = cipher; return 0; } static void crypto_cbc_exit_tfm(struct crypto_tfm *tfm) { struct crypto_cbc_ctx *ctx = crypto_tfm_ctx(tfm); crypto_free_cipher(ctx->child); } static struct crypto_instance *crypto_cbc_alloc(struct rtattr **tb) { struct crypto_instance *inst; struct crypto_alg *alg; int err; err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER); if (err) return ERR_PTR(err); alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, CRYPTO_ALG_TYPE_MASK); if (IS_ERR(alg)) return ERR_PTR(PTR_ERR(alg)); inst = ERR_PTR(-EINVAL); if (!is_power_of_2(alg->cra_blocksize)) goto out_put_alg; inst = crypto_alloc_instance("cbc", alg); if (IS_ERR(inst)) goto out_put_alg; inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER; inst->alg.cra_priority = alg->cra_priority; inst->alg.cra_blocksize = alg->cra_blocksize; inst->alg.cra_alignmask = alg->cra_alignmask; inst->alg.cra_type = &crypto_blkcipher_type; /* We access the data as u32s when xoring. */ inst->alg.cra_alignmask |= __alignof__(u32) - 1; inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize; inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize; inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize; inst->alg.cra_ctxsize = sizeof(struct crypto_cbc_ctx); inst->alg.cra_init = crypto_cbc_init_tfm; inst->alg.cra_exit = crypto_cbc_exit_tfm; inst->alg.cra_blkcipher.setkey = crypto_cbc_setkey; inst->alg.cra_blkcipher.encrypt = crypto_cbc_encrypt; inst->alg.cra_blkcipher.decrypt = crypto_cbc_decrypt; out_put_alg: crypto_mod_put(alg); return inst; } static void crypto_cbc_free(struct crypto_instance *inst) { crypto_drop_spawn(crypto_instance_ctx(inst)); kfree(inst); } static struct crypto_template crypto_cbc_tmpl = { .name = "cbc", .alloc = crypto_cbc_alloc, .free = crypto_cbc_free, .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); } module_init(crypto_cbc_module_init); module_exit(crypto_cbc_module_exit); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("CBC block cipher algorithm");