linux/crypto/ecdh.c
Tudor-Dan Ambarus 952035baed crypto: ecdh - fix concurrency on shared secret and pubkey
ecdh_ctx contained static allocated data for the shared secret
and public key.

The shared secret and the public key were doomed to concurrency
issues because they could be shared by multiple crypto requests.

The concurrency is fixed by replacing per-tfm shared secret and
public key with per-request dynamically allocated shared secret
and public key.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2017-08-03 13:47:22 +08:00

169 lines
3.8 KiB
C

/* ECDH key-agreement protocol
*
* Copyright (c) 2016, Intel Corporation
* Authors: Salvator Benedetto <salvatore.benedetto@intel.com>
*
* 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 <linux/module.h>
#include <crypto/internal/kpp.h>
#include <crypto/kpp.h>
#include <crypto/ecdh.h>
#include <linux/scatterlist.h>
#include "ecc.h"
struct ecdh_ctx {
unsigned int curve_id;
unsigned int ndigits;
u64 private_key[ECC_MAX_DIGITS];
};
static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm)
{
return kpp_tfm_ctx(tfm);
}
static unsigned int ecdh_supported_curve(unsigned int curve_id)
{
switch (curve_id) {
case ECC_CURVE_NIST_P192: return 3;
case ECC_CURVE_NIST_P256: return 4;
default: return 0;
}
}
static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
unsigned int len)
{
struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
struct ecdh params;
unsigned int ndigits;
if (crypto_ecdh_decode_key(buf, len, &params) < 0)
return -EINVAL;
ndigits = ecdh_supported_curve(params.curve_id);
if (!ndigits)
return -EINVAL;
ctx->curve_id = params.curve_id;
ctx->ndigits = ndigits;
if (!params.key || !params.key_size)
return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
ctx->private_key);
if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
(const u64 *)params.key, params.key_size) < 0)
return -EINVAL;
memcpy(ctx->private_key, params.key, params.key_size);
return 0;
}
static int ecdh_compute_value(struct kpp_request *req)
{
struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
u64 *public_key;
u64 *shared_secret = NULL;
void *buf;
size_t copied, nbytes, public_key_sz;
int ret = -ENOMEM;
nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
/* Public part is a point thus it has both coordinates */
public_key_sz = 2 * nbytes;
public_key = kmalloc(public_key_sz, GFP_KERNEL);
if (!public_key)
return -ENOMEM;
if (req->src) {
shared_secret = kmalloc(nbytes, GFP_KERNEL);
if (!shared_secret)
goto free_pubkey;
copied = sg_copy_to_buffer(req->src, 1, public_key,
public_key_sz);
if (copied != public_key_sz) {
ret = -EINVAL;
goto free_all;
}
ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
ctx->private_key, public_key,
shared_secret);
buf = shared_secret;
} else {
ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits,
ctx->private_key, public_key);
buf = public_key;
nbytes = public_key_sz;
}
if (ret < 0)
goto free_all;
copied = sg_copy_from_buffer(req->dst, 1, buf, nbytes);
if (copied != nbytes)
ret = -EINVAL;
/* fall through */
free_all:
kzfree(shared_secret);
free_pubkey:
kfree(public_key);
return ret;
}
static unsigned int ecdh_max_size(struct crypto_kpp *tfm)
{
struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
/* Public key is made of two coordinates, add one to the left shift */
return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1);
}
static void no_exit_tfm(struct crypto_kpp *tfm)
{
return;
}
static struct kpp_alg ecdh = {
.set_secret = ecdh_set_secret,
.generate_public_key = ecdh_compute_value,
.compute_shared_secret = ecdh_compute_value,
.max_size = ecdh_max_size,
.exit = no_exit_tfm,
.base = {
.cra_name = "ecdh",
.cra_driver_name = "ecdh-generic",
.cra_priority = 100,
.cra_module = THIS_MODULE,
.cra_ctxsize = sizeof(struct ecdh_ctx),
},
};
static int ecdh_init(void)
{
return crypto_register_kpp(&ecdh);
}
static void ecdh_exit(void)
{
crypto_unregister_kpp(&ecdh);
}
module_init(ecdh_init);
module_exit(ecdh_exit);
MODULE_ALIAS_CRYPTO("ecdh");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ECDH generic algorithm");