1 /* Diffie-Hellman Key Agreement Method [RFC2631]
3 * Copyright (c) 2016, Intel Corporation
4 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
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.
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>
24 static void dh_clear_ctx(struct dh_ctx *ctx)
29 memset(ctx, 0, sizeof(*ctx));
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]
38 static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
40 /* val = base^xa mod p */
41 return mpi_powm(val, base, ctx->xa, ctx->p);
44 static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm)
46 return kpp_tfm_ctx(tfm);
49 static int dh_check_params_length(unsigned int p_len)
51 return (p_len < 1536) ? -EINVAL : 0;
54 static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
56 if (unlikely(!params->p || !params->g))
59 if (dh_check_params_length(params->p_size << 3))
62 ctx->p = mpi_read_raw_data(params->p, params->p_size);
66 ctx->g = mpi_read_raw_data(params->g, params->g_size);
73 static int dh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len)
75 struct dh_ctx *ctx = dh_get_ctx(tfm);
78 /* Free the old MPI key if any */
81 if (crypto_dh_decode_key(buf, len, ¶ms) < 0)
84 if (dh_set_params(ctx, ¶ms) < 0)
87 ctx->xa = mpi_read_raw_data(params.key, params.key_size);
98 static int dh_compute_value(struct kpp_request *req)
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);
109 if (unlikely(!ctx->xa)) {
115 base = mpi_read_raw_from_sgl(req->src, req->src_len);
124 ret = _compute_val(ctx, base, val);
128 ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
142 static int dh_max_size(struct crypto_kpp *tfm)
144 struct dh_ctx *ctx = dh_get_ctx(tfm);
146 return mpi_get_size(ctx->p);
149 static void dh_exit_tfm(struct crypto_kpp *tfm)
151 struct dh_ctx *ctx = dh_get_ctx(tfm);
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,
164 .cra_driver_name = "dh-generic",
166 .cra_module = THIS_MODULE,
167 .cra_ctxsize = sizeof(struct dh_ctx),
171 static int dh_init(void)
173 return crypto_register_kpp(&dh);
176 static void dh_exit(void)
178 crypto_unregister_kpp(&dh);
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");