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// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
* Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*
* Based on public domain code from Daniel J. Bernstein and Peter Schwabe. This
* began from SUPERCOP's curve25519/neon2/scalarmult.s, but has subsequently been
* manually reworked for use in kernel space.
*/
#include <asm/hwcap.h>
#include <asm/neon.h>
#include <asm/simd.h>
#include <crypto/internal/kpp.h>
#include <crypto/internal/simd.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/jump_label.h>
#include <crypto/curve25519.h>
asmlinkage void curve25519_neon(u8 mypublic[CURVE25519_KEY_SIZE],
const u8 secret[CURVE25519_KEY_SIZE],
const u8 basepoint[CURVE25519_KEY_SIZE]);
static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
const u8 scalar[CURVE25519_KEY_SIZE],
const u8 point[CURVE25519_KEY_SIZE])
{
if (static_branch_likely(&have_neon) && crypto_simd_usable()) {
kernel_neon_begin();
curve25519_neon(out, scalar, point);
kernel_neon_end();
} else {
curve25519_generic(out, scalar, point);
}
}
EXPORT_SYMBOL(curve25519_arch);
static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
unsigned int len)
{
u8 *secret = kpp_tfm_ctx(tfm);
if (!len)
curve25519_generate_secret(secret);
else if (len == CURVE25519_KEY_SIZE &&
crypto_memneq(buf, curve25519_null_point, CURVE25519_KEY_SIZE))
memcpy(secret, buf, CURVE25519_KEY_SIZE);
else
return -EINVAL;
return 0;
}
static int curve25519_compute_value(struct kpp_request *req)
{
struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
const u8 *secret = kpp_tfm_ctx(tfm);
u8 public_key[CURVE25519_KEY_SIZE];
u8 buf[CURVE25519_KEY_SIZE];
int copied, nbytes;
u8 const *bp;
if (req->src) {
copied = sg_copy_to_buffer(req->src,
sg_nents_for_len(req->src,
CURVE25519_KEY_SIZE),
public_key, CURVE25519_KEY_SIZE);
if (copied != CURVE25519_KEY_SIZE)
return -EINVAL;
bp = public_key;
} else {
bp = curve25519_base_point;
}
curve25519_arch(buf, secret, bp);
/* might want less than we've got */
nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
nbytes),
buf, nbytes);
if (copied != nbytes)
return -EINVAL;
return 0;
}
static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
{
return CURVE25519_KEY_SIZE;
}
static struct kpp_alg curve25519_alg = {
.base.cra_name = "curve25519",
.base.cra_driver_name = "curve25519-neon",
.base.cra_priority = 200,
.base.cra_module = THIS_MODULE,
.base.cra_ctxsize = CURVE25519_KEY_SIZE,
.set_secret = curve25519_set_secret,
.generate_public_key = curve25519_compute_value,
.compute_shared_secret = curve25519_compute_value,
.max_size = curve25519_max_size,
};
static int __init mod_init(void)
{
if (elf_hwcap & HWCAP_NEON) {
static_branch_enable(&have_neon);
return IS_REACHABLE(CONFIG_CRYPTO_KPP) ?
crypto_register_kpp(&curve25519_alg) : 0;
}
return 0;
}
static void __exit mod_exit(void)
{
if (IS_REACHABLE(CONFIG_CRYPTO_KPP) && elf_hwcap & HWCAP_NEON)
crypto_unregister_kpp(&curve25519_alg);
}
module_init(mod_init);
module_exit(mod_exit);
MODULE_ALIAS_CRYPTO("curve25519");
MODULE_ALIAS_CRYPTO("curve25519-neon");
MODULE_LICENSE("GPL v2");
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