1 /* ECDH key-agreement protocol 2 * 3 * Copyright (c) 2016, Intel Corporation 4 * Authors: Salvator Benedetto <salvatore.benedetto@intel.com> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #include <linux/module.h> 13 #include <crypto/internal/kpp.h> 14 #include <crypto/kpp.h> 15 #include <crypto/ecdh.h> 16 #include <linux/scatterlist.h> 17 #include "ecc.h" 18 19 struct ecdh_ctx { 20 unsigned int curve_id; 21 unsigned int ndigits; 22 u64 private_key[ECC_MAX_DIGITS]; 23 u64 public_key[2 * ECC_MAX_DIGITS]; 24 u64 shared_secret[ECC_MAX_DIGITS]; 25 }; 26 27 static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm) 28 { 29 return kpp_tfm_ctx(tfm); 30 } 31 32 static unsigned int ecdh_supported_curve(unsigned int curve_id) 33 { 34 switch (curve_id) { 35 case ECC_CURVE_NIST_P192: return 3; 36 case ECC_CURVE_NIST_P256: return 4; 37 default: return 0; 38 } 39 } 40 41 static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf, 42 unsigned int len) 43 { 44 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 45 struct ecdh params; 46 unsigned int ndigits; 47 48 if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0) 49 return -EINVAL; 50 51 ndigits = ecdh_supported_curve(params.curve_id); 52 if (!ndigits) 53 return -EINVAL; 54 55 ctx->curve_id = params.curve_id; 56 ctx->ndigits = ndigits; 57 58 if (!params.key || !params.key_size) 59 return ecc_gen_privkey(ctx->curve_id, ctx->ndigits, 60 ctx->private_key); 61 62 if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits, 63 (const u64 *)params.key, params.key_size) < 0) 64 return -EINVAL; 65 66 memcpy(ctx->private_key, params.key, params.key_size); 67 68 return 0; 69 } 70 71 static int ecdh_compute_value(struct kpp_request *req) 72 { 73 int ret = 0; 74 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req); 75 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 76 size_t copied, nbytes; 77 void *buf; 78 79 nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; 80 81 if (req->src) { 82 copied = sg_copy_to_buffer(req->src, 1, ctx->public_key, 83 2 * nbytes); 84 if (copied != 2 * nbytes) 85 return -EINVAL; 86 87 ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits, 88 ctx->private_key, 89 ctx->public_key, 90 ctx->shared_secret); 91 92 buf = ctx->shared_secret; 93 } else { 94 ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits, 95 ctx->private_key, ctx->public_key); 96 buf = ctx->public_key; 97 /* Public part is a point thus it has both coordinates */ 98 nbytes *= 2; 99 } 100 101 if (ret < 0) 102 return ret; 103 104 copied = sg_copy_from_buffer(req->dst, 1, buf, nbytes); 105 if (copied != nbytes) 106 return -EINVAL; 107 108 return ret; 109 } 110 111 static unsigned int ecdh_max_size(struct crypto_kpp *tfm) 112 { 113 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 114 115 /* Public key is made of two coordinates, add one to the left shift */ 116 return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1); 117 } 118 119 static void no_exit_tfm(struct crypto_kpp *tfm) 120 { 121 return; 122 } 123 124 static struct kpp_alg ecdh = { 125 .set_secret = ecdh_set_secret, 126 .generate_public_key = ecdh_compute_value, 127 .compute_shared_secret = ecdh_compute_value, 128 .max_size = ecdh_max_size, 129 .exit = no_exit_tfm, 130 .base = { 131 .cra_name = "ecdh", 132 .cra_driver_name = "ecdh-generic", 133 .cra_priority = 100, 134 .cra_module = THIS_MODULE, 135 .cra_ctxsize = sizeof(struct ecdh_ctx), 136 }, 137 }; 138 139 static int ecdh_init(void) 140 { 141 return crypto_register_kpp(&ecdh); 142 } 143 144 static void ecdh_exit(void) 145 { 146 crypto_unregister_kpp(&ecdh); 147 } 148 149 module_init(ecdh_init); 150 module_exit(ecdh_exit); 151 MODULE_ALIAS_CRYPTO("ecdh"); 152 MODULE_LICENSE("GPL"); 153 MODULE_DESCRIPTION("ECDH generic algorithm"); 154