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