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 unsigned int ecdh_supported_curve(unsigned int curve_id) 27 { 28 switch (curve_id) { 29 case ECC_CURVE_NIST_P192: return ECC_CURVE_NIST_P192_DIGITS; 30 case ECC_CURVE_NIST_P256: return ECC_CURVE_NIST_P256_DIGITS; 31 default: return 0; 32 } 33 } 34 35 static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf, 36 unsigned int len) 37 { 38 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 39 struct ecdh params; 40 unsigned int ndigits; 41 42 if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0 || 43 params.key_size > sizeof(ctx->private_key)) 44 return -EINVAL; 45 46 ndigits = ecdh_supported_curve(params.curve_id); 47 if (!ndigits) 48 return -EINVAL; 49 50 ctx->curve_id = params.curve_id; 51 ctx->ndigits = ndigits; 52 53 if (!params.key || !params.key_size) 54 return ecc_gen_privkey(ctx->curve_id, ctx->ndigits, 55 ctx->private_key); 56 57 memcpy(ctx->private_key, params.key, params.key_size); 58 59 if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits, 60 ctx->private_key, params.key_size) < 0) { 61 memzero_explicit(ctx->private_key, params.key_size); 62 return -EINVAL; 63 } 64 return 0; 65 } 66 67 static int ecdh_compute_value(struct kpp_request *req) 68 { 69 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req); 70 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 71 u64 *public_key; 72 u64 *shared_secret = NULL; 73 void *buf; 74 size_t copied, nbytes, public_key_sz; 75 int ret = -ENOMEM; 76 77 nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; 78 /* Public part is a point thus it has both coordinates */ 79 public_key_sz = 2 * nbytes; 80 81 public_key = kmalloc(public_key_sz, GFP_KERNEL); 82 if (!public_key) 83 return -ENOMEM; 84 85 if (req->src) { 86 shared_secret = kmalloc(nbytes, GFP_KERNEL); 87 if (!shared_secret) 88 goto free_pubkey; 89 90 /* from here on it's invalid parameters */ 91 ret = -EINVAL; 92 93 /* must have exactly two points to be on the curve */ 94 if (public_key_sz != req->src_len) 95 goto free_all; 96 97 copied = sg_copy_to_buffer(req->src, 98 sg_nents_for_len(req->src, 99 public_key_sz), 100 public_key, public_key_sz); 101 if (copied != public_key_sz) 102 goto free_all; 103 104 ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits, 105 ctx->private_key, public_key, 106 shared_secret); 107 108 buf = shared_secret; 109 } else { 110 ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits, 111 ctx->private_key, public_key); 112 buf = public_key; 113 nbytes = public_key_sz; 114 } 115 116 if (ret < 0) 117 goto free_all; 118 119 /* might want less than we've got */ 120 nbytes = min_t(size_t, nbytes, req->dst_len); 121 copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst, 122 nbytes), 123 buf, nbytes); 124 if (copied != nbytes) 125 ret = -EINVAL; 126 127 /* fall through */ 128 free_all: 129 kfree_sensitive(shared_secret); 130 free_pubkey: 131 kfree(public_key); 132 return ret; 133 } 134 135 static unsigned int ecdh_max_size(struct crypto_kpp *tfm) 136 { 137 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 138 139 /* Public key is made of two coordinates, add one to the left shift */ 140 return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1); 141 } 142 143 static struct kpp_alg ecdh = { 144 .set_secret = ecdh_set_secret, 145 .generate_public_key = ecdh_compute_value, 146 .compute_shared_secret = ecdh_compute_value, 147 .max_size = ecdh_max_size, 148 .base = { 149 .cra_name = "ecdh", 150 .cra_driver_name = "ecdh-generic", 151 .cra_priority = 100, 152 .cra_module = THIS_MODULE, 153 .cra_ctxsize = sizeof(struct ecdh_ctx), 154 }, 155 }; 156 157 static int ecdh_init(void) 158 { 159 return crypto_register_kpp(&ecdh); 160 } 161 162 static void ecdh_exit(void) 163 { 164 crypto_unregister_kpp(&ecdh); 165 } 166 167 subsys_initcall(ecdh_init); 168 module_exit(ecdh_exit); 169 MODULE_ALIAS_CRYPTO("ecdh"); 170 MODULE_LICENSE("GPL"); 171 MODULE_DESCRIPTION("ECDH generic algorithm"); 172