1 // SPDX-License-Identifier: GPL-2.0 OR MIT
3 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
5 * Based on public domain code from Daniel J. Bernstein and Peter Schwabe. This
6 * began from SUPERCOP's curve25519/neon2/scalarmult.s, but has subsequently been
7 * manually reworked for use in kernel space.
10 #include <asm/hwcap.h>
13 #include <crypto/internal/kpp.h>
14 #include <crypto/internal/simd.h>
15 #include <linux/types.h>
16 #include <linux/module.h>
17 #include <linux/init.h>
18 #include <linux/jump_label.h>
19 #include <linux/scatterlist.h>
20 #include <crypto/curve25519.h>
22 asmlinkage void curve25519_neon(u8 mypublic[CURVE25519_KEY_SIZE],
23 const u8 secret[CURVE25519_KEY_SIZE],
24 const u8 basepoint[CURVE25519_KEY_SIZE]);
26 static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
28 void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
29 const u8 scalar[CURVE25519_KEY_SIZE],
30 const u8 point[CURVE25519_KEY_SIZE])
32 if (static_branch_likely(&have_neon) && crypto_simd_usable()) {
34 curve25519_neon(out, scalar, point);
37 curve25519_generic(out, scalar, point);
40 EXPORT_SYMBOL(curve25519_arch);
42 void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
43 const u8 secret[CURVE25519_KEY_SIZE])
45 return curve25519_arch(pub, secret, curve25519_base_point);
47 EXPORT_SYMBOL(curve25519_base_arch);
49 static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
52 u8 *secret = kpp_tfm_ctx(tfm);
55 curve25519_generate_secret(secret);
56 else if (len == CURVE25519_KEY_SIZE &&
57 crypto_memneq(buf, curve25519_null_point, CURVE25519_KEY_SIZE))
58 memcpy(secret, buf, CURVE25519_KEY_SIZE);
64 static int curve25519_compute_value(struct kpp_request *req)
66 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
67 const u8 *secret = kpp_tfm_ctx(tfm);
68 u8 public_key[CURVE25519_KEY_SIZE];
69 u8 buf[CURVE25519_KEY_SIZE];
74 copied = sg_copy_to_buffer(req->src,
75 sg_nents_for_len(req->src,
77 public_key, CURVE25519_KEY_SIZE);
78 if (copied != CURVE25519_KEY_SIZE)
82 bp = curve25519_base_point;
85 curve25519_arch(buf, secret, bp);
87 /* might want less than we've got */
88 nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
89 copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
97 static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
99 return CURVE25519_KEY_SIZE;
102 static struct kpp_alg curve25519_alg = {
103 .base.cra_name = "curve25519",
104 .base.cra_driver_name = "curve25519-neon",
105 .base.cra_priority = 200,
106 .base.cra_module = THIS_MODULE,
107 .base.cra_ctxsize = CURVE25519_KEY_SIZE,
109 .set_secret = curve25519_set_secret,
110 .generate_public_key = curve25519_compute_value,
111 .compute_shared_secret = curve25519_compute_value,
112 .max_size = curve25519_max_size,
115 static int __init mod_init(void)
117 if (elf_hwcap & HWCAP_NEON) {
118 static_branch_enable(&have_neon);
119 return IS_REACHABLE(CONFIG_CRYPTO_KPP) ?
120 crypto_register_kpp(&curve25519_alg) : 0;
125 static void __exit mod_exit(void)
127 if (IS_REACHABLE(CONFIG_CRYPTO_KPP) && elf_hwcap & HWCAP_NEON)
128 crypto_unregister_kpp(&curve25519_alg);
131 module_init(mod_init);
132 module_exit(mod_exit);
134 MODULE_ALIAS_CRYPTO("curve25519");
135 MODULE_ALIAS_CRYPTO("curve25519-neon");
136 MODULE_LICENSE("GPL v2");