/* * 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/module.h> #include <linux/scatterlist.h> #include <linux/slab.h> struct crypto_cbc_ctx { struct crypto_cipher *child; void (*xor)(u8 *dst, const u8 *src, unsigned int bs); }; 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 (*xor)(u8 *, const u8 *, unsigned int)) { 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 { 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 (*xor)(u8 *, const u8 *, unsigned int)) { 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 { 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; void (*xor)(u8 *, const u8 *, unsigned int bs) = ctx->xor; 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, xor); else nbytes = crypto_cbc_encrypt_segment(desc, &walk, child, xor); 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 (*xor)(u8 *, const u8 *, unsigned int)) { 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); 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 (*xor)(u8 *, const u8 *, unsigned int)) { void (*fn)(struct crypto_tfm *, u8 *, const u8 *) = crypto_cipher_alg(tfm)->cia_decrypt; int bsize = crypto_cipher_blocksize(tfm); unsigned long alignmask = crypto_cipher_alignmask(tfm); unsigned int nbytes = walk->nbytes; u8 *src = walk->src.virt.addr; u8 stack[bsize + alignmask]; u8 *first_iv = (u8 *)ALIGN((unsigned long)stack, alignmask + 1); memcpy(first_iv, walk->iv, bsize); /* Start of the last block. */ src += nbytes - nbytes % bsize - bsize; memcpy(walk->iv, src, bsize); for (;;) { fn(crypto_cipher_tfm(tfm), src, src); if ((nbytes -= bsize) < bsize) break; xor(src, src - bsize, bsize); src -= bsize; } xor(src, first_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; void (*xor)(u8 *, const u8 *, unsigned int bs) = ctx->xor; 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, xor); else nbytes = crypto_cbc_decrypt_segment(desc, &walk, child, xor); err = blkcipher_walk_done(desc, &walk, nbytes); } return err; } static void xor_byte(u8 *a, const u8 *b, unsigned int bs) { do { *a++ ^= *b++; } while (--bs); } static void xor_quad(u8 *dst, const u8 *src, unsigned int bs) { u32 *a = (u32 *)dst; u32 *b = (u32 *)src; do { *a++ ^= *b++; } while ((bs -= 4)); } static void xor_64(u8 *a, const u8 *b, unsigned int bs) { ((u32 *)a)[0] ^= ((u32 *)b)[0]; ((u32 *)a)[1] ^= ((u32 *)b)[1]; } static void xor_128(u8 *a, const u8 *b, unsigned int bs) { ((u32 *)a)[0] ^= ((u32 *)b)[0]; ((u32 *)a)[1] ^= ((u32 *)b)[1]; ((u32 *)a)[2] ^= ((u32 *)b)[2]; ((u32 *)a)[3] ^= ((u32 *)b)[3]; } 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; switch (crypto_tfm_alg_blocksize(tfm)) { case 8: ctx->xor = xor_64; break; case 16: ctx->xor = xor_128; break; default: if (crypto_tfm_alg_blocksize(tfm) % 4) ctx->xor = xor_byte; else ctx->xor = xor_quad; } 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(void *param, unsigned int len) { struct crypto_instance *inst; struct crypto_alg *alg; alg = crypto_get_attr_alg(param, len, CRYPTO_ALG_TYPE_CIPHER, CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_ASYNC); if (IS_ERR(alg)) return ERR_PTR(PTR_ERR(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; if (!(alg->cra_blocksize % 4)) inst->alg.cra_alignmask |= 3; 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");