/*
* eseqiv: Encrypted Sequence Number IV Generator
*
* This generator generates an IV based on a sequence number by xoring 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.
*
* 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 <crypto/scatterwalk.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/spinlock.h>
#include <linux/string.h>
struct eseqiv_request_ctx {
struct scatterlist src[2];
struct scatterlist dst[2];
char tail[];
};
struct eseqiv_ctx {
spinlock_t lock;
unsigned int reqoff;
char salt[];
};
static void eseqiv_complete2(struct skcipher_givcrypt_request *req)
{
struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);
memcpy(req->giv, PTR_ALIGN((u8 *)reqctx->tail,
crypto_ablkcipher_alignmask(geniv) + 1),
crypto_ablkcipher_ivsize(geniv));
}
static void eseqiv_complete(struct crypto_async_request *base, int err)
{
struct skcipher_givcrypt_request *req = base->data;
if (err)
goto out;
eseqiv_complete2(req);
out:
skcipher_givcrypt_complete(req, err);
}
static void eseqiv_chain(struct scatterlist *head, struct scatterlist *sg,
int chain)
{
if (chain) {
head->length += sg->length;
sg = scatterwalk_sg_next(sg);
}
if (sg)
scatterwalk_sg_chain(head, 2, sg);
else
sg_mark_end(head);
}
static int eseqiv_givencrypt(struct skcipher_givcrypt_request *req)
{
struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);
struct ablkcipher_request *subreq;
crypto_completion_t complete;
void *data;
struct scatterlist *osrc, *odst;
struct scatterlist *dst;
struct page *srcp;
struct page *dstp;
u8 *giv;
u8 *vsrc;
u8 *vdst;
__be64 seq;
unsigned int ivsize;
unsigned int len;
int err;
subreq = (void *)(reqctx->tail + ctx->reqoff);
ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
giv = req->giv;
complete = req->creq.base.complete;
data = req->creq.base.data;
osrc = req->creq.src;
odst = req->creq.dst;
srcp = sg_page(osrc);
dstp = sg_page(odst);
vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + osrc->offset;
vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + odst->offset;
ivsize = crypto_ablkcipher_ivsize(geniv);
if (vsrc != giv + ivsize && vdst != giv + ivsize) {
giv = PTR_ALIGN((u8 *)reqctx->tail,
crypto_ablkcipher_alignmask(geniv) + 1);
complete = eseqiv_complete;
data = req;
}
ablkcipher_request_set_callback(subreq, req->creq.base.flags, complete,
data);
sg_init_table(reqctx->src, 2);
sg_set_buf(reqctx->src, giv, ivsize);
eseqiv_chain(reqctx->src, osrc, vsrc == giv + ivsize);
dst = reqctx->src;
if (osrc != odst) {
sg_init_table(reqctx->dst, 2);
sg_set_buf(reqctx->dst, giv, ivsize);
eseqiv_chain(reqctx->dst, odst, vdst == giv + ivsize);
dst = reqctx->dst;
}
ablkcipher_request_set_crypt(subreq, reqctx->src, dst,
req->creq.nbytes, req->creq.info);
memcpy(req->creq.info, ctx->salt, ivsize);
len = ivsize;
if (ivsize > sizeof(u64)) {
memset(req->giv, 0, ivsize - sizeof(u64));
len = sizeof(u64);
}
seq = cpu_to_be64(req->seq);
memcpy(req->giv + ivsize - len, &seq, len);
err = crypto_ablkcipher_encrypt(subreq);
if (err)
goto out;
eseqiv_complete2(req);
out:
return err;
}
static int eseqiv_givencrypt_first(struct skcipher_givcrypt_request *req)
{
struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
spin_lock_bh(&ctx->lock);
if (crypto_ablkcipher_crt(geniv)->givencrypt != eseqiv_givencrypt_first)
goto unlock;
crypto_ablkcipher_crt(geniv)->givencrypt = eseqiv_givencrypt;
get_random_bytes(ctx->salt, crypto_ablkcipher_ivsize(geniv));
unlock:
spin_unlock_bh(&ctx->lock);
return eseqiv_givencrypt(req);
}
static int eseqiv_init(struct crypto_tfm *tfm)
{
struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
unsigned long alignmask;
unsigned int reqsize;
spin_lock_init(&ctx->lock);
alignmask = crypto_tfm_ctx_alignment() - 1;
reqsize = sizeof(struct eseqiv_request_ctx);
if (alignmask & reqsize) {
alignmask &= reqsize;
alignmask--;
}
alignmask = ~alignmask;
alignmask &= crypto_ablkcipher_alignmask(geniv);
reqsize += alignmask;
reqsize += crypto_ablkcipher_ivsize(geniv);
reqsize = ALIGN(reqsize, crypto_tfm_ctx_alignment());
ctx->reqoff = reqsize - sizeof(struct eseqiv_request_ctx);
tfm->crt_ablkcipher.reqsize = reqsize +
sizeof(struct ablkcipher_request);
return skcipher_geniv_init(tfm);
}
static struct crypto_template eseqiv_tmpl;
static struct crypto_instance *eseqiv_alloc(struct rtattr **tb)
{
struct crypto_instance *inst;
int err;
inst = skcipher_geniv_alloc(&eseqiv_tmpl, tb, 0, 0);
if (IS_ERR(inst))
goto out;
err = -EINVAL;
if (inst->alg.cra_ablkcipher.ivsize != inst->alg.cra_blocksize)
goto free_inst;
inst->alg.cra_ablkcipher.givencrypt = eseqiv_givencrypt_first;
inst->alg.cra_init = eseqiv_init;
inst->alg.cra_exit = skcipher_geniv_exit;
inst->alg.cra_ctxsize = sizeof(struct eseqiv_ctx);
inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
out:
return inst;
free_inst:
skcipher_geniv_free(inst);
inst = ERR_PTR(err);
goto out;
}
static struct crypto_template eseqiv_tmpl = {
.name = "eseqiv",
.alloc = eseqiv_alloc,
.free = skcipher_geniv_free,
.module = THIS_MODULE,
};
int __init eseqiv_module_init(void)
{
return crypto_register_template(&eseqiv_tmpl);
}
EXPORT_SYMBOL_GPL(eseqiv_module_init);
void __exit eseqiv_module_exit(void)
{
crypto_unregister_template(&eseqiv_tmpl);
}
EXPORT_SYMBOL_GPL(eseqiv_module_exit);
