Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 1 | /* Diffie-Hellman Key Agreement Method [RFC2631] |
| 2 | * |
| 3 | * Copyright (c) 2016, Intel Corporation |
| 4 | * Authors: Salvatore 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 Licence |
| 8 | * as published by the Free Software Foundation; either version |
| 9 | * 2 of the Licence, 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/dh.h> |
| 16 | #include <linux/mpi.h> |
| 17 | |
| 18 | struct dh_ctx { |
| 19 | MPI p; |
| 20 | MPI g; |
| 21 | MPI xa; |
| 22 | }; |
| 23 | |
Eric Biggers | aa15fe4 | 2017-11-05 18:30:44 -0800 | [diff] [blame] | 24 | static void dh_clear_ctx(struct dh_ctx *ctx) |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 25 | { |
| 26 | mpi_free(ctx->p); |
| 27 | mpi_free(ctx->g); |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 28 | mpi_free(ctx->xa); |
Eric Biggers | aa15fe4 | 2017-11-05 18:30:44 -0800 | [diff] [blame] | 29 | memset(ctx, 0, sizeof(*ctx)); |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 30 | } |
| 31 | |
| 32 | /* |
| 33 | * If base is g we compute the public key |
| 34 | * ya = g^xa mod p; [RFC2631 sec 2.1.1] |
| 35 | * else if base if the counterpart public key we compute the shared secret |
| 36 | * ZZ = yb^xa mod p; [RFC2631 sec 2.1.1] |
| 37 | */ |
| 38 | static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val) |
| 39 | { |
| 40 | /* val = base^xa mod p */ |
| 41 | return mpi_powm(val, base, ctx->xa, ctx->p); |
| 42 | } |
| 43 | |
| 44 | static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm) |
| 45 | { |
| 46 | return kpp_tfm_ctx(tfm); |
| 47 | } |
| 48 | |
| 49 | static int dh_check_params_length(unsigned int p_len) |
| 50 | { |
| 51 | return (p_len < 1536) ? -EINVAL : 0; |
| 52 | } |
| 53 | |
| 54 | static int dh_set_params(struct dh_ctx *ctx, struct dh *params) |
| 55 | { |
| 56 | if (unlikely(!params->p || !params->g)) |
| 57 | return -EINVAL; |
| 58 | |
| 59 | if (dh_check_params_length(params->p_size << 3)) |
| 60 | return -EINVAL; |
| 61 | |
| 62 | ctx->p = mpi_read_raw_data(params->p, params->p_size); |
| 63 | if (!ctx->p) |
| 64 | return -EINVAL; |
| 65 | |
| 66 | ctx->g = mpi_read_raw_data(params->g, params->g_size); |
Eric Biggers | aa15fe4 | 2017-11-05 18:30:44 -0800 | [diff] [blame] | 67 | if (!ctx->g) |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 68 | return -EINVAL; |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 69 | |
| 70 | return 0; |
| 71 | } |
| 72 | |
| 73 | static int dh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len) |
| 74 | { |
| 75 | struct dh_ctx *ctx = dh_get_ctx(tfm); |
| 76 | struct dh params; |
| 77 | |
Tudor-Dan Ambarus | 4a7e023 | 2017-05-25 10:18:07 +0300 | [diff] [blame] | 78 | /* Free the old MPI key if any */ |
Eric Biggers | aa15fe4 | 2017-11-05 18:30:44 -0800 | [diff] [blame] | 79 | dh_clear_ctx(ctx); |
Tudor-Dan Ambarus | 4a7e023 | 2017-05-25 10:18:07 +0300 | [diff] [blame] | 80 | |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 81 | if (crypto_dh_decode_key(buf, len, ¶ms) < 0) |
Eric Biggers | aa15fe4 | 2017-11-05 18:30:44 -0800 | [diff] [blame] | 82 | goto err_clear_ctx; |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 83 | |
| 84 | if (dh_set_params(ctx, ¶ms) < 0) |
Eric Biggers | aa15fe4 | 2017-11-05 18:30:44 -0800 | [diff] [blame] | 85 | goto err_clear_ctx; |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 86 | |
| 87 | ctx->xa = mpi_read_raw_data(params.key, params.key_size); |
Eric Biggers | aa15fe4 | 2017-11-05 18:30:44 -0800 | [diff] [blame] | 88 | if (!ctx->xa) |
| 89 | goto err_clear_ctx; |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 90 | |
| 91 | return 0; |
Eric Biggers | aa15fe4 | 2017-11-05 18:30:44 -0800 | [diff] [blame] | 92 | |
| 93 | err_clear_ctx: |
| 94 | dh_clear_ctx(ctx); |
| 95 | return -EINVAL; |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 96 | } |
| 97 | |
| 98 | static int dh_compute_value(struct kpp_request *req) |
| 99 | { |
| 100 | struct crypto_kpp *tfm = crypto_kpp_reqtfm(req); |
| 101 | struct dh_ctx *ctx = dh_get_ctx(tfm); |
| 102 | MPI base, val = mpi_alloc(0); |
| 103 | int ret = 0; |
| 104 | int sign; |
| 105 | |
| 106 | if (!val) |
| 107 | return -ENOMEM; |
| 108 | |
| 109 | if (unlikely(!ctx->xa)) { |
| 110 | ret = -EINVAL; |
| 111 | goto err_free_val; |
| 112 | } |
| 113 | |
| 114 | if (req->src) { |
| 115 | base = mpi_read_raw_from_sgl(req->src, req->src_len); |
| 116 | if (!base) { |
| 117 | ret = EINVAL; |
| 118 | goto err_free_val; |
| 119 | } |
| 120 | } else { |
| 121 | base = ctx->g; |
| 122 | } |
| 123 | |
| 124 | ret = _compute_val(ctx, base, val); |
| 125 | if (ret) |
| 126 | goto err_free_base; |
| 127 | |
Herbert Xu | 9b45b7b | 2016-06-29 19:32:21 +0800 | [diff] [blame] | 128 | ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign); |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 129 | if (ret) |
| 130 | goto err_free_base; |
| 131 | |
| 132 | if (sign < 0) |
| 133 | ret = -EBADMSG; |
| 134 | err_free_base: |
| 135 | if (req->src) |
| 136 | mpi_free(base); |
| 137 | err_free_val: |
| 138 | mpi_free(val); |
| 139 | return ret; |
| 140 | } |
| 141 | |
| 142 | static int dh_max_size(struct crypto_kpp *tfm) |
| 143 | { |
| 144 | struct dh_ctx *ctx = dh_get_ctx(tfm); |
| 145 | |
| 146 | return mpi_get_size(ctx->p); |
| 147 | } |
| 148 | |
| 149 | static void dh_exit_tfm(struct crypto_kpp *tfm) |
| 150 | { |
| 151 | struct dh_ctx *ctx = dh_get_ctx(tfm); |
| 152 | |
Eric Biggers | aa15fe4 | 2017-11-05 18:30:44 -0800 | [diff] [blame] | 153 | dh_clear_ctx(ctx); |
Salvatore Benedetto | 802c7f1 | 2016-06-22 17:49:14 +0100 | [diff] [blame] | 154 | } |
| 155 | |
| 156 | static struct kpp_alg dh = { |
| 157 | .set_secret = dh_set_secret, |
| 158 | .generate_public_key = dh_compute_value, |
| 159 | .compute_shared_secret = dh_compute_value, |
| 160 | .max_size = dh_max_size, |
| 161 | .exit = dh_exit_tfm, |
| 162 | .base = { |
| 163 | .cra_name = "dh", |
| 164 | .cra_driver_name = "dh-generic", |
| 165 | .cra_priority = 100, |
| 166 | .cra_module = THIS_MODULE, |
| 167 | .cra_ctxsize = sizeof(struct dh_ctx), |
| 168 | }, |
| 169 | }; |
| 170 | |
| 171 | static int dh_init(void) |
| 172 | { |
| 173 | return crypto_register_kpp(&dh); |
| 174 | } |
| 175 | |
| 176 | static void dh_exit(void) |
| 177 | { |
| 178 | crypto_unregister_kpp(&dh); |
| 179 | } |
| 180 | |
| 181 | module_init(dh_init); |
| 182 | module_exit(dh_exit); |
| 183 | MODULE_ALIAS_CRYPTO("dh"); |
| 184 | MODULE_LICENSE("GPL"); |
| 185 | MODULE_DESCRIPTION("DH generic algorithm"); |