*
* Copyright (C) 2018 ARM Limited or its affiliates.
* All rights reserved.
- *
- * Based loosely on public domain code gleaned from libtomcrypt
- * (https://github.com/libtom/libtomcrypt).
*/
#include <crypto/algapi.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
-#include <linux/scatterlist.h>
-#include <linux/slab.h>
-
-struct crypto_ofb_ctx {
- struct crypto_cipher *child;
- int cnt;
-};
-
-static int crypto_ofb_setkey(struct crypto_skcipher *parent, const u8 *key,
- unsigned int keylen)
+static int crypto_ofb_crypt(struct skcipher_request *req)
{
- struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(parent);
- struct crypto_cipher *child = ctx->child;
+ struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+ struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
+ const unsigned int bsize = crypto_cipher_blocksize(cipher);
+ struct skcipher_walk walk;
int err;
- crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
- crypto_cipher_set_flags(child, crypto_skcipher_get_flags(parent) &
- CRYPTO_TFM_REQ_MASK);
- err = crypto_cipher_setkey(child, key, keylen);
- crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(child) &
- CRYPTO_TFM_RES_MASK);
- return err;
-}
-
-static int crypto_ofb_encrypt_segment(struct crypto_ofb_ctx *ctx,
- struct skcipher_walk *walk,
- struct crypto_cipher *tfm)
-{
- int bsize = crypto_cipher_blocksize(tfm);
- int nbytes = walk->nbytes;
-
- u8 *src = walk->src.virt.addr;
- u8 *dst = walk->dst.virt.addr;
- u8 *iv = walk->iv;
-
- do {
- if (ctx->cnt == bsize) {
- if (nbytes < bsize)
- break;
- crypto_cipher_encrypt_one(tfm, iv, iv);
- ctx->cnt = 0;
- }
- *dst = *src ^ iv[ctx->cnt];
- src++;
- dst++;
- ctx->cnt++;
- } while (--nbytes);
- return nbytes;
-}
-
-static int crypto_ofb_encrypt(struct skcipher_request *req)
-{
- struct skcipher_walk walk;
- struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
- unsigned int bsize;
- struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm);
- struct crypto_cipher *child = ctx->child;
- int ret = 0;
+ err = skcipher_walk_virt(&walk, req, false);
- bsize = crypto_cipher_blocksize(child);
- ctx->cnt = bsize;
+ while (walk.nbytes >= bsize) {
+ const u8 *src = walk.src.virt.addr;
+ u8 *dst = walk.dst.virt.addr;
+ u8 * const iv = walk.iv;
+ unsigned int nbytes = walk.nbytes;
- ret = skcipher_walk_virt(&walk, req, false);
+ do {
+ crypto_cipher_encrypt_one(cipher, iv, iv);
+ crypto_xor_cpy(dst, src, iv, bsize);
+ dst += bsize;
+ src += bsize;
+ } while ((nbytes -= bsize) >= bsize);
- while (walk.nbytes) {
- ret = crypto_ofb_encrypt_segment(ctx, &walk, child);
- ret = skcipher_walk_done(&walk, ret);
+ err = skcipher_walk_done(&walk, nbytes);
}
- return ret;
-}
-
-/* OFB encrypt and decrypt are identical */
-static int crypto_ofb_decrypt(struct skcipher_request *req)
-{
- return crypto_ofb_encrypt(req);
-}
-
-static int crypto_ofb_init_tfm(struct crypto_skcipher *tfm)
-{
- struct skcipher_instance *inst = skcipher_alg_instance(tfm);
- struct crypto_spawn *spawn = skcipher_instance_ctx(inst);
- struct crypto_ofb_ctx *ctx = crypto_skcipher_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_ofb_exit_tfm(struct crypto_skcipher *tfm)
-{
- struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm);
-
- crypto_free_cipher(ctx->child);
-}
-
-static void crypto_ofb_free(struct skcipher_instance *inst)
-{
- crypto_drop_skcipher(skcipher_instance_ctx(inst));
- kfree(inst);
+ if (walk.nbytes) {
+ crypto_cipher_encrypt_one(cipher, walk.iv, walk.iv);
+ crypto_xor_cpy(walk.dst.virt.addr, walk.src.virt.addr, walk.iv,
+ walk.nbytes);
+ err = skcipher_walk_done(&walk, 0);
+ }
+ return err;
}
static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb)
{
struct skcipher_instance *inst;
- struct crypto_attr_type *algt;
- struct crypto_spawn *spawn;
struct crypto_alg *alg;
- u32 mask;
int err;
- err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER);
- if (err)
- return err;
-
- inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
- if (!inst)
- return -ENOMEM;
-
- algt = crypto_get_attr_type(tb);
- err = PTR_ERR(algt);
- if (IS_ERR(algt))
- goto err_free_inst;
-
- mask = CRYPTO_ALG_TYPE_MASK |
- crypto_requires_off(algt->type, algt->mask,
- CRYPTO_ALG_NEED_FALLBACK);
+ inst = skcipher_alloc_instance_simple(tmpl, tb, &alg);
+ if (IS_ERR(inst))
+ return PTR_ERR(inst);
- alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, mask);
- err = PTR_ERR(alg);
- if (IS_ERR(alg))
- goto err_free_inst;
+ /* OFB mode is a stream cipher. */
+ inst->alg.base.cra_blocksize = 1;
- spawn = skcipher_instance_ctx(inst);
- err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
- CRYPTO_ALG_TYPE_MASK);
- crypto_mod_put(alg);
- if (err)
- goto err_free_inst;
-
- err = crypto_inst_setname(skcipher_crypto_instance(inst), "ofb", alg);
- if (err)
- goto err_drop_spawn;
-
- inst->alg.base.cra_priority = alg->cra_priority;
- inst->alg.base.cra_blocksize = alg->cra_blocksize;
- inst->alg.base.cra_alignmask = alg->cra_alignmask;
-
- /* We access the data as u32s when xoring. */
- inst->alg.base.cra_alignmask |= __alignof__(u32) - 1;
+ /*
+ * To simplify the implementation, configure the skcipher walk to only
+ * give a partial block at the very end, never earlier.
+ */
+ inst->alg.chunksize = alg->cra_blocksize;
- inst->alg.ivsize = alg->cra_blocksize;
- inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize;
- inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize;
-
- inst->alg.base.cra_ctxsize = sizeof(struct crypto_ofb_ctx);
-
- inst->alg.init = crypto_ofb_init_tfm;
- inst->alg.exit = crypto_ofb_exit_tfm;
-
- inst->alg.setkey = crypto_ofb_setkey;
- inst->alg.encrypt = crypto_ofb_encrypt;
- inst->alg.decrypt = crypto_ofb_decrypt;
-
- inst->free = crypto_ofb_free;
+ inst->alg.encrypt = crypto_ofb_crypt;
+ inst->alg.decrypt = crypto_ofb_crypt;
err = skcipher_register_instance(tmpl, inst);
if (err)
- goto err_drop_spawn;
+ inst->free(inst);
-out:
+ crypto_mod_put(alg);
return err;
-
-err_drop_spawn:
- crypto_drop_spawn(spawn);
-err_free_inst:
- kfree(inst);
- goto out;
}
static struct crypto_template crypto_ofb_tmpl = {
module_exit(crypto_ofb_module_exit);
MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("OFB block cipher algorithm");
+MODULE_DESCRIPTION("OFB block cipher mode of operation");
MODULE_ALIAS_CRYPTO("ofb");
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