Commit de3ea8e1 authored by Eric Biggers's avatar Eric Biggers
Browse files

crypto: x86/curve25519 - Remove unused kpp support 

Curve25519 is used only via the library API, not the crypto_kpp API.  In
preparation for removing the unused crypto_kpp API for Curve25519,
remove the unused "curve25519-x86" kpp algorithm.

Note that the underlying x86_64 optimized Curve25519 code remains fully
supported and accessible via the library API.

It's also worth noting that even if the kpp support for Curve25519 comes
back later, there is no need for arch-specific kpp glue code like this,
as a single kpp algorithm that wraps the library API is sufficient.

Link: https://lore.kernel.org/r/20250906213523.84915-5-ebiggers@kernel.org


Signed-off-by: default avatarEric Biggers <ebiggers@kernel.org>
parent 8c44847e

arch/x86/crypto/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -5,7 +5,6 @@ menu "Accelerated Cryptographic Algorithms for CPU (x86)" 
config CRYPTO_CURVE25519_X86

	tristate

	depends on 64BIT

	select CRYPTO_KPP

	select CRYPTO_LIB_CURVE25519_GENERIC

	select CRYPTO_ARCH_HAVE_LIB_CURVE25519

	default CRYPTO_LIB_CURVE25519_INTERNAL

arch/x86/crypto/curve25519-x86_64.c

+1 −97
Original line number Diff line number Diff line
@@ -5,14 +5,12 @@ 
 */



#include <crypto/curve25519.h>

#include <crypto/internal/kpp.h>



#include <linux/export.h>

#include <linux/types.h>

#include <linux/jump_label.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/scatterlist.h>



#include <asm/cpufeature.h>

#include <asm/processor.h>
@@ -1613,114 +1611,20 @@ void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE], 
}

EXPORT_SYMBOL(curve25519_base_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_generate_public_key(struct kpp_request *req)

{

	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);

	const u8 *secret = kpp_tfm_ctx(tfm);

	u8 buf[CURVE25519_KEY_SIZE];

	int copied, nbytes;



	if (req->src)

		return -EINVAL;



	curve25519_base_arch(buf, secret);



	/* 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 int curve25519_compute_shared_secret(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;



	if (!req->src)

		return -EINVAL;



	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;



	curve25519_arch(buf, secret, public_key);



	/* 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-x86",

	.base.cra_priority	= 200,

	.base.cra_module	= THIS_MODULE,

	.base.cra_ctxsize	= CURVE25519_KEY_SIZE,



	.set_secret		= curve25519_set_secret,

	.generate_public_key	= curve25519_generate_public_key,

	.compute_shared_secret	= curve25519_compute_shared_secret,

	.max_size		= curve25519_max_size,

};





static int __init curve25519_mod_init(void)

{

	if (boot_cpu_has(X86_FEATURE_BMI2) && boot_cpu_has(X86_FEATURE_ADX))

		static_branch_enable(&curve25519_use_bmi2_adx);

	else

	return 0;

	return IS_REACHABLE(CONFIG_CRYPTO_KPP) ?

		crypto_register_kpp(&curve25519_alg) : 0;

}



static void __exit curve25519_mod_exit(void)

{

	if (IS_REACHABLE(CONFIG_CRYPTO_KPP) &&

	    static_branch_likely(&curve25519_use_bmi2_adx))

		crypto_unregister_kpp(&curve25519_alg);

}



module_init(curve25519_mod_init);

module_exit(curve25519_mod_exit);



MODULE_ALIAS_CRYPTO("curve25519");

MODULE_ALIAS_CRYPTO("curve25519-x86");

MODULE_DESCRIPTION("Curve25519 algorithm, ADX optimized");

MODULE_LICENSE("GPL v2");

MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");