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 (ecc_is_key_valid(ctx->curve_id, ctx->ndigits, 59 (const u8 *)params.key, params.key_size) < 0) 60 return -EINVAL; 61 62 memcpy(ctx->private_key, params.key, params.key_size); 63 64 return 0; 65 } 66 67 static int ecdh_compute_value(struct kpp_request *req) 68 { 69 int ret = 0; 70 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req); 71 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 72 size_t copied, nbytes; 73 void *buf; 74 75 nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; 76 77 if (req->src) { 78 copied = sg_copy_to_buffer(req->src, 1, ctx->public_key, 79 2 * nbytes); 80 if (copied != 2 * nbytes) 81 return -EINVAL; 82 83 ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits, 84 (const u8 *)ctx->private_key, 85 (const u8 *)ctx->public_key, 86 (u8 *)ctx->shared_secret); 87 88 buf = ctx->shared_secret; 89 } else { 90 ret = ecdh_make_pub_key(ctx->curve_id, ctx->ndigits, 91 (const u8 *)ctx->private_key, 92 (u8 *)ctx->public_key); 93 buf = ctx->public_key; 94 /* Public part is a point thus it has both coordinates */ 95 nbytes *= 2; 96 } 97 98 if (ret < 0) 99 return ret; 100 101 copied = sg_copy_from_buffer(req->dst, 1, buf, nbytes); 102 if (copied != nbytes) 103 return -EINVAL; 104 105 return ret; 106 } 107 108 static int ecdh_max_size(struct crypto_kpp *tfm) 109 { 110 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); 111 int nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; 112 113 /* Public key is made of two coordinates */ 114 return 2 * nbytes; 115 } 116 117 static void no_exit_tfm(struct crypto_kpp *tfm) 118 { 119 return; 120 } 121 122 static struct kpp_alg ecdh = { 123 .set_secret = ecdh_set_secret, 124 .generate_public_key = ecdh_compute_value, 125 .compute_shared_secret = ecdh_compute_value, 126 .max_size = ecdh_max_size, 127 .exit = no_exit_tfm, 128 .base = { 129 .cra_name = "ecdh", 130 .cra_driver_name = "ecdh-generic", 131 .cra_priority = 100, 132 .cra_module = THIS_MODULE, 133 .cra_ctxsize = sizeof(struct ecdh_ctx), 134 }, 135 }; 136 137 static int ecdh_init(void) 138 { 139 return crypto_register_kpp(&ecdh); 140 } 141 142 static void ecdh_exit(void) 143 { 144 crypto_unregister_kpp(&ecdh); 145 } 146 147 module_init(ecdh_init); 148 module_exit(ecdh_exit); 149 MODULE_ALIAS_CRYPTO("ecdh"); 150 MODULE_LICENSE("GPL"); 151 MODULE_DESCRIPTION("ECDH generic algorithm"); 152