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/*
* echainiv: Encrypted Chain IV Generator
*
* This generator generates an IV based on a sequence number by multiplying
* it with a salt and then encrypting it with the same key as used to encrypt
* the plain text. This algorithm requires that the block size be equal
* to the IV size. It is mainly useful for CBC.
*
* This generator can only be used by algorithms where authentication
* is performed after encryption (i.e., authenc).
*
* Copyright (c) 2015 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/geniv.h>
#include <crypto/scatterwalk.h>
#include <crypto/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
static int echainiv_encrypt(struct aead_request *req)
{
struct crypto_aead *geniv = crypto_aead_reqtfm(req);
struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
struct aead_request *subreq = aead_request_ctx(req);
__be64 nseqno;
u64 seqno;
u8 *info;
unsigned int ivsize = crypto_aead_ivsize(geniv);
int err;
if (req->cryptlen < ivsize)
return -EINVAL;
aead_request_set_tfm(subreq, ctx->child);
info = req->iv;
if (req->src != req->dst) {
SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);
skcipher_request_set_tfm(nreq, ctx->sknull);
skcipher_request_set_callback(nreq, req->base.flags,
NULL, NULL);
skcipher_request_set_crypt(nreq, req->src, req->dst,
req->assoclen + req->cryptlen,
NULL);
err = crypto_skcipher_encrypt(nreq);
if (err)
return err;
}
aead_request_set_callback(subreq, req->base.flags,
req->base.complete, req->base.data);
aead_request_set_crypt(subreq, req->dst, req->dst,
req->cryptlen, info);
aead_request_set_ad(subreq, req->assoclen);
memcpy(&nseqno, info + ivsize - 8, 8);
seqno = be64_to_cpu(nseqno);
memset(info, 0, ivsize);
scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
do {
u64 a;
memcpy(&a, ctx->salt + ivsize - 8, 8);
a |= 1;
a *= seqno;
memcpy(info + ivsize - 8, &a, 8);
} while ((ivsize -= 8));
return crypto_aead_encrypt(subreq);
}
static int echainiv_decrypt(struct aead_request *req)
{
struct crypto_aead *geniv = crypto_aead_reqtfm(req);
struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
struct aead_request *subreq = aead_request_ctx(req);
crypto_completion_t compl;
void *data;
unsigned int ivsize = crypto_aead_ivsize(geniv);
if (req->cryptlen < ivsize)
return -EINVAL;
aead_request_set_tfm(subreq, ctx->child);
compl = req->base.complete;
data = req->base.data;
aead_request_set_callback(subreq, req->base.flags, compl, data);
aead_request_set_crypt(subreq, req->src, req->dst,
req->cryptlen - ivsize, req->iv);
aead_request_set_ad(subreq, req->assoclen + ivsize);
scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
return crypto_aead_decrypt(subreq);
}
static int echainiv_aead_create(struct crypto_template *tmpl,
struct rtattr **tb)
{
struct aead_instance *inst;
struct crypto_aead_spawn *spawn;
struct aead_alg *alg;
int err;
inst = aead_geniv_alloc(tmpl, tb, 0, 0);
if (IS_ERR(inst))
return PTR_ERR(inst);
spawn = aead_instance_ctx(inst);
alg = crypto_spawn_aead_alg(spawn);
err = -EINVAL;
if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
goto free_inst;
inst->alg.encrypt = echainiv_encrypt;
inst->alg.decrypt = echainiv_decrypt;
inst->alg.init = aead_init_geniv;
inst->alg.exit = aead_exit_geniv;
inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
inst->alg.base.cra_ctxsize += inst->alg.ivsize;
inst->free = aead_geniv_free;
err = aead_register_instance(tmpl, inst);
if (err)
goto free_inst;
out:
return err;
free_inst:
aead_geniv_free(inst);
goto out;
}
static void echainiv_free(struct crypto_instance *inst)
{
aead_geniv_free(aead_instance(inst));
}
static struct crypto_template echainiv_tmpl = {
.name = "echainiv",
.create = echainiv_aead_create,
.free = echainiv_free,
.module = THIS_MODULE,
};
static int __init echainiv_module_init(void)
{
return crypto_register_template(&echainiv_tmpl);
}
static void __exit echainiv_module_exit(void)
{
crypto_unregister_template(&echainiv_tmpl);
}
module_init(echainiv_module_init);
module_exit(echainiv_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Encrypted Chain IV Generator");
MODULE_ALIAS_CRYPTO("echainiv");
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