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/*
* chainiv: Chain IV Generator
*
* Generate IVs simply be using the last block of the previous encryption.
* This is mainly useful for CBC with a synchronous algorithm.
*
* Copyright (c) 2007 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/internal/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/spinlock.h>
#include <linux/string.h>
struct chainiv_ctx {
spinlock_t lock;
char iv[];
};
static int chainiv_givencrypt(struct skcipher_givcrypt_request *req)
{
struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
unsigned int ivsize;
int err;
ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
ablkcipher_request_set_callback(subreq, req->creq.base.flags &
~CRYPTO_TFM_REQ_MAY_SLEEP,
req->creq.base.complete,
req->creq.base.data);
ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
req->creq.nbytes, req->creq.info);
spin_lock_bh(&ctx->lock);
ivsize = crypto_ablkcipher_ivsize(geniv);
memcpy(req->giv, ctx->iv, ivsize);
memcpy(subreq->info, ctx->iv, ivsize);
err = crypto_ablkcipher_encrypt(subreq);
if (err)
goto unlock;
memcpy(ctx->iv, subreq->info, ivsize);
unlock:
spin_unlock_bh(&ctx->lock);
return err;
}
static int chainiv_givencrypt_first(struct skcipher_givcrypt_request *req)
{
struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
spin_lock_bh(&ctx->lock);
if (crypto_ablkcipher_crt(geniv)->givencrypt !=
chainiv_givencrypt_first)
goto unlock;
crypto_ablkcipher_crt(geniv)->givencrypt = chainiv_givencrypt;
get_random_bytes(ctx->iv, crypto_ablkcipher_ivsize(geniv));
unlock:
spin_unlock_bh(&ctx->lock);
return chainiv_givencrypt(req);
}
static int chainiv_init(struct crypto_tfm *tfm)
{
struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
spin_lock_init(&ctx->lock);
tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request);
return skcipher_geniv_init(tfm);
}
static struct crypto_template chainiv_tmpl;
static struct crypto_instance *chainiv_alloc(struct rtattr **tb)
{
struct crypto_instance *inst;
inst = skcipher_geniv_alloc(&chainiv_tmpl, tb, 0,
CRYPTO_ALG_ASYNC);
if (IS_ERR(inst))
goto out;
inst->alg.cra_ablkcipher.givencrypt = chainiv_givencrypt_first;
inst->alg.cra_init = chainiv_init;
inst->alg.cra_exit = skcipher_geniv_exit;
inst->alg.cra_ctxsize = sizeof(struct chainiv_ctx) +
inst->alg.cra_ablkcipher.ivsize;
out:
return inst;
}
static struct crypto_template chainiv_tmpl = {
.name = "chainiv",
.alloc = chainiv_alloc,
.free = skcipher_geniv_free,
.module = THIS_MODULE,
};
static int __init chainiv_module_init(void)
{
return crypto_register_template(&chainiv_tmpl);
}
static void __exit chainiv_module_exit(void)
{
crypto_unregister_template(&chainiv_tmpl);
}
module_init(chainiv_module_init);
module_exit(chainiv_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Chain IV Generator");
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