1 // SPDX-License-Identifier: GPL-2.0 OR MIT
2 /*
3 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
4 *
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.
8 */
9
10 #include <asm/hwcap.h>
11 #include <asm/neon.h>
12 #include <asm/simd.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>
21
22 asmlinkage void curve25519_neon(u8 mypublic[CURVE25519_KEY_SIZE],
23 const u8 secret[CURVE25519_KEY_SIZE],
24 const u8 basepoint[CURVE25519_KEY_SIZE]);
25
26 static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
27
28 void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
29 const u8 scalar[CURVE25519_KEY_SIZE],
30 const u8 point[CURVE25519_KEY_SIZE])
31 {
32 if (static_branch_likely(&have_neon) && crypto_simd_usable()) {
33 kernel_neon_begin();
34 curve25519_neon(out, scalar, point);
35 kernel_neon_end();
36 } else {
37 curve25519_generic(out, scalar, point);
38 }
39 }
40 EXPORT_SYMBOL(curve25519_arch);
41
42 void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
43 const u8 secret[CURVE25519_KEY_SIZE])
44 {
45 return curve25519_arch(pub, secret, curve25519_base_point);
46 }
47 EXPORT_SYMBOL(curve25519_base_arch);
48
49 static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
50 unsigned int len)
51 {
52 u8 *secret = kpp_tfm_ctx(tfm);
53
54 if (!len)
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);
59 else
60 return -EINVAL;
61 return 0;
62 }
63
64 static int curve25519_compute_value(struct kpp_request *req)
65 {
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];
70 int copied, nbytes;
71 u8 const *bp;
72
73 if (req->src) {
74 copied = sg_copy_to_buffer(req->src,
75 sg_nents_for_len(req->src,
76 CURVE25519_KEY_SIZE),
77 public_key, CURVE25519_KEY_SIZE);
78 if (copied != CURVE25519_KEY_SIZE)
79 return -EINVAL;
80 bp = public_key;
81 } else {
82 bp = curve25519_base_point;
83 }
84
85 curve25519_arch(buf, secret, bp);
86
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,
90 nbytes),
91 buf, nbytes);
92 if (copied != nbytes)
93 return -EINVAL;
94 return 0;
95 }
96
97 static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
98 {
99 return CURVE25519_KEY_SIZE;
100 }
101
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,
108
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,
113 };
114
115 static int __init arm_curve25519_init(void)
116 {
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;
121 }
122 return 0;
123 }
124
125 static void __exit arm_curve25519_exit(void)
126 {
127 if (IS_REACHABLE(CONFIG_CRYPTO_KPP) && elf_hwcap & HWCAP_NEON)
128 crypto_unregister_kpp(&curve25519_alg);
129 }
130
131 module_init(arm_curve25519_init);
132 module_exit(arm_curve25519_exit);
133
134 MODULE_ALIAS_CRYPTO("curve25519");
135 MODULE_ALIAS_CRYPTO("curve25519-neon");
136 MODULE_DESCRIPTION("Public key crypto: Curve25519 (NEON-accelerated)");
137 MODULE_LICENSE("GPL v2");
138
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