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/*
* seqiv: Sequence Number IV Generator
*
* This generator generates an IV based on a sequence number by xoring it
* with a salt. This algorithm is mainly useful for CTR and similar modes.
*
* 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/kernel.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/spinlock.h>
#include <linux/string.h>
struct seqiv_ctx {
spinlock_t lock;
u8 salt[] __attribute__ ((aligned(__alignof__(u32))));
};
static void seqiv_complete2(struct skcipher_givcrypt_request *req, int err)
{
struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
struct crypto_ablkcipher *geniv;
if (err == -EINPROGRESS)
return;
if (err)
goto out;
geniv = skcipher_givcrypt_reqtfm(req);
memcpy(req->creq.info, subreq->info, crypto_ablkcipher_ivsize(geniv));
out:
kfree(subreq->info);
}
static void seqiv_complete(struct crypto_async_request *base, int err)
{
struct skcipher_givcrypt_request *req = base->data;
seqiv_complete2(req, err);
skcipher_givcrypt_complete(req, err);
}
static int seqiv_givencrypt(struct skcipher_givcrypt_request *req)
{
struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
crypto_completion_t complete;
void *data;
u8 *info;
__be64 seq;
unsigned int ivsize;
unsigned int len;
int err;
ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
complete = req->creq.base.complete;
data = req->creq.base.data;
info = req->creq.info;
ivsize = crypto_ablkcipher_ivsize(geniv);
if (unlikely(!IS_ALIGNED((unsigned long)info,
crypto_ablkcipher_alignmask(geniv) + 1))) {
info = kmalloc(ivsize, req->creq.base.flags &
CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL:
GFP_ATOMIC);
if (!info)
return -ENOMEM;
complete = seqiv_complete;
data = req;
}
ablkcipher_request_set_callback(subreq, req->creq.base.flags, complete,
data);
ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
req->creq.nbytes, info);
len = ivsize;
if (ivsize > sizeof(u64)) {
memset(info, 0, ivsize - sizeof(u64));
len = sizeof(u64);
}
seq = cpu_to_be64(req->seq);
memcpy(info + ivsize - len, &seq, len);
crypto_xor(info, ctx->salt, ivsize);
memcpy(req->giv, info, ivsize);
err = crypto_ablkcipher_encrypt(subreq);
if (unlikely(info != req->creq.info))
seqiv_complete2(req, err);
return err;
}
static int seqiv_givencrypt_first(struct skcipher_givcrypt_request *req)
{
struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
spin_lock_bh(&ctx->lock);
if (crypto_ablkcipher_crt(geniv)->givencrypt != seqiv_givencrypt_first)
goto unlock;
crypto_ablkcipher_crt(geniv)->givencrypt = seqiv_givencrypt;
get_random_bytes(ctx->salt, crypto_ablkcipher_ivsize(geniv));
unlock:
spin_unlock_bh(&ctx->lock);
return seqiv_givencrypt(req);
}
static int seqiv_init(struct crypto_tfm *tfm)
{
struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
struct seqiv_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 seqiv_tmpl;
static struct crypto_instance *seqiv_alloc(struct rtattr **tb)
{
struct crypto_instance *inst;
inst = skcipher_geniv_alloc(&seqiv_tmpl, tb, 0, 0);
if (IS_ERR(inst))
goto out;
inst->alg.cra_ablkcipher.givencrypt = seqiv_givencrypt_first;
inst->alg.cra_init = seqiv_init;
inst->alg.cra_exit = skcipher_geniv_exit;
inst->alg.cra_alignmask |= __alignof__(u32) - 1;
inst->alg.cra_ctxsize = sizeof(struct seqiv_ctx);
inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
out:
return inst;
}
static struct crypto_template seqiv_tmpl = {
.name = "seqiv",
.alloc = seqiv_alloc,
.free = skcipher_geniv_free,
.module = THIS_MODULE,
};
static int __init seqiv_module_init(void)
{
return crypto_register_template(&seqiv_tmpl);
}
static void __exit seqiv_module_exit(void)
{
crypto_unregister_template(&seqiv_tmpl);
}
module_init(seqiv_module_init);
module_exit(seqiv_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Sequence Number IV Generator");
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