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