1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* ECDH key-agreement protocol 3 * 4 * Copyright (c) 2016, Intel Corporation 5 * Authors: Salvator Benedetto <salvatore.benedetto@intel.com> 6 */ 7 8 #include <linux/module.h> 9 #include <crypto/internal/kpp.h> 10 #include <crypto/kpp.h> 11 #include <crypto/ecdh.h> 12 #include <linux/scatterlist.h> 13 #include "ecc.h" 14 15 struct ecdh_ctx { 16 unsigned int curve_id; 17 unsigned int ndigits; 18 u64 private_key[ECC_MAX_DIGITS]; 19 }; 20 21 static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm) 22 { 23 return kpp_tfm_ctx(tfm); 24 } 25 26 static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf, 27 unsigned int len) 28 { 29 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 30 struct ecdh params; 31 32 if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0 || 33 params.key_size > sizeof(u64) * ctx->ndigits) 34 return -EINVAL; 35 36 if (!params.key || !params.key_size) 37 return ecc_gen_privkey(ctx->curve_id, ctx->ndigits, 38 ctx->private_key); 39 40 memcpy(ctx->private_key, params.key, params.key_size); 41 42 if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits, 43 ctx->private_key, params.key_size) < 0) { 44 memzero_explicit(ctx->private_key, params.key_size); 45 return -EINVAL; 46 } 47 return 0; 48 } 49 50 static int ecdh_compute_value(struct kpp_request *req) 51 { 52 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req); 53 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 54 u64 *public_key; 55 u64 *shared_secret = NULL; 56 void *buf; 57 size_t copied, nbytes, public_key_sz; 58 int ret = -ENOMEM; 59 60 nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; 61 /* Public part is a point thus it has both coordinates */ 62 public_key_sz = 2 * nbytes; 63 64 public_key = kmalloc(public_key_sz, GFP_KERNEL); 65 if (!public_key) 66 return -ENOMEM; 67 68 if (req->src) { 69 shared_secret = kmalloc(nbytes, GFP_KERNEL); 70 if (!shared_secret) 71 goto free_pubkey; 72 73 /* from here on it's invalid parameters */ 74 ret = -EINVAL; 75 76 /* must have exactly two points to be on the curve */ 77 if (public_key_sz != req->src_len) 78 goto free_all; 79 80 copied = sg_copy_to_buffer(req->src, 81 sg_nents_for_len(req->src, 82 public_key_sz), 83 public_key, public_key_sz); 84 if (copied != public_key_sz) 85 goto free_all; 86 87 ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits, 88 ctx->private_key, public_key, 89 shared_secret); 90 91 buf = shared_secret; 92 } else { 93 ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits, 94 ctx->private_key, public_key); 95 buf = public_key; 96 nbytes = public_key_sz; 97 } 98 99 if (ret < 0) 100 goto free_all; 101 102 /* might want less than we've got */ 103 nbytes = min_t(size_t, nbytes, req->dst_len); 104 copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst, 105 nbytes), 106 buf, nbytes); 107 if (copied != nbytes) 108 ret = -EINVAL; 109 110 /* fall through */ 111 free_all: 112 kfree_sensitive(shared_secret); 113 free_pubkey: 114 kfree(public_key); 115 return ret; 116 } 117 118 static unsigned int ecdh_max_size(struct crypto_kpp *tfm) 119 { 120 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 121 122 /* Public key is made of two coordinates, add one to the left shift */ 123 return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1); 124 } 125 126 static int ecdh_nist_p192_init_tfm(struct crypto_kpp *tfm) 127 { 128 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 129 130 ctx->curve_id = ECC_CURVE_NIST_P192; 131 ctx->ndigits = ECC_CURVE_NIST_P192_DIGITS; 132 133 return 0; 134 } 135 136 static struct kpp_alg ecdh_nist_p192 = { 137 .set_secret = ecdh_set_secret, 138 .generate_public_key = ecdh_compute_value, 139 .compute_shared_secret = ecdh_compute_value, 140 .max_size = ecdh_max_size, 141 .init = ecdh_nist_p192_init_tfm, 142 .base = { 143 .cra_name = "ecdh-nist-p192", 144 .cra_driver_name = "ecdh-generic", 145 .cra_priority = 100, 146 .cra_module = THIS_MODULE, 147 .cra_ctxsize = sizeof(struct ecdh_ctx), 148 }, 149 }; 150 151 static int ecdh_nist_p256_init_tfm(struct crypto_kpp *tfm) 152 { 153 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 154 155 ctx->curve_id = ECC_CURVE_NIST_P256; 156 ctx->ndigits = ECC_CURVE_NIST_P256_DIGITS; 157 158 return 0; 159 } 160 161 static struct kpp_alg ecdh_nist_p256 = { 162 .set_secret = ecdh_set_secret, 163 .generate_public_key = ecdh_compute_value, 164 .compute_shared_secret = ecdh_compute_value, 165 .max_size = ecdh_max_size, 166 .init = ecdh_nist_p256_init_tfm, 167 .base = { 168 .cra_name = "ecdh-nist-p256", 169 .cra_driver_name = "ecdh-generic", 170 .cra_priority = 100, 171 .cra_module = THIS_MODULE, 172 .cra_ctxsize = sizeof(struct ecdh_ctx), 173 }, 174 }; 175 176 static bool ecdh_nist_p192_registered; 177 178 static int ecdh_init(void) 179 { 180 int ret; 181 182 ret = crypto_register_kpp(&ecdh_nist_p192); 183 ecdh_nist_p192_registered = ret == 0; 184 185 return crypto_register_kpp(&ecdh_nist_p256); 186 } 187 188 static void ecdh_exit(void) 189 { 190 if (ecdh_nist_p192_registered) 191 crypto_unregister_kpp(&ecdh_nist_p192); 192 crypto_unregister_kpp(&ecdh_nist_p256); 193 } 194 195 subsys_initcall(ecdh_init); 196 module_exit(ecdh_exit); 197 MODULE_ALIAS_CRYPTO("ecdh"); 198 MODULE_LICENSE("GPL"); 199 MODULE_DESCRIPTION("ECDH generic algorithm"); 200