| 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"); |