GNU Linux-libre 4.19.211-gnu1
[releases.git] / crypto / ecdh.c
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 };
24
25 static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm)
26 {
27         return kpp_tfm_ctx(tfm);
28 }
29
30 static unsigned int ecdh_supported_curve(unsigned int curve_id)
31 {
32         switch (curve_id) {
33         case ECC_CURVE_NIST_P192: return ECC_CURVE_NIST_P192_DIGITS;
34         case ECC_CURVE_NIST_P256: return ECC_CURVE_NIST_P256_DIGITS;
35         default: return 0;
36         }
37 }
38
39 static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
40                            unsigned int len)
41 {
42         struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
43         struct ecdh params;
44         unsigned int ndigits;
45
46         if (crypto_ecdh_decode_key(buf, len, &params) < 0 ||
47             params.key_size > sizeof(ctx->private_key))
48                 return -EINVAL;
49
50         ndigits = ecdh_supported_curve(params.curve_id);
51         if (!ndigits)
52                 return -EINVAL;
53
54         ctx->curve_id = params.curve_id;
55         ctx->ndigits = ndigits;
56
57         if (!params.key || !params.key_size)
58                 return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
59                                        ctx->private_key);
60
61         memcpy(ctx->private_key, params.key, params.key_size);
62
63         if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
64                              ctx->private_key, params.key_size) < 0) {
65                 memzero_explicit(ctx->private_key, params.key_size);
66                 return -EINVAL;
67         }
68         return 0;
69 }
70
71 static int ecdh_compute_value(struct kpp_request *req)
72 {
73         struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
74         struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
75         u64 *public_key;
76         u64 *shared_secret = NULL;
77         void *buf;
78         size_t copied, nbytes, public_key_sz;
79         int ret = -ENOMEM;
80
81         nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
82         /* Public part is a point thus it has both coordinates */
83         public_key_sz = 2 * nbytes;
84
85         public_key = kmalloc(public_key_sz, GFP_KERNEL);
86         if (!public_key)
87                 return -ENOMEM;
88
89         if (req->src) {
90                 shared_secret = kmalloc(nbytes, GFP_KERNEL);
91                 if (!shared_secret)
92                         goto free_pubkey;
93
94                 /* from here on it's invalid parameters */
95                 ret = -EINVAL;
96
97                 /* must have exactly two points to be on the curve */
98                 if (public_key_sz != req->src_len)
99                         goto free_all;
100
101                 copied = sg_copy_to_buffer(req->src,
102                                            sg_nents_for_len(req->src,
103                                                             public_key_sz),
104                                            public_key, public_key_sz);
105                 if (copied != public_key_sz)
106                         goto free_all;
107
108                 ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
109                                                 ctx->private_key, public_key,
110                                                 shared_secret);
111
112                 buf = shared_secret;
113         } else {
114                 ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits,
115                                        ctx->private_key, public_key);
116                 buf = public_key;
117                 nbytes = public_key_sz;
118         }
119
120         if (ret < 0)
121                 goto free_all;
122
123         /* might want less than we've got */
124         nbytes = min_t(size_t, nbytes, req->dst_len);
125         copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
126                                                                 nbytes),
127                                      buf, nbytes);
128         if (copied != nbytes)
129                 ret = -EINVAL;
130
131         /* fall through */
132 free_all:
133         kzfree(shared_secret);
134 free_pubkey:
135         kfree(public_key);
136         return ret;
137 }
138
139 static unsigned int ecdh_max_size(struct crypto_kpp *tfm)
140 {
141         struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
142
143         /* Public key is made of two coordinates, add one to the left shift */
144         return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1);
145 }
146
147 static struct kpp_alg ecdh = {
148         .set_secret = ecdh_set_secret,
149         .generate_public_key = ecdh_compute_value,
150         .compute_shared_secret = ecdh_compute_value,
151         .max_size = ecdh_max_size,
152         .base = {
153                 .cra_name = "ecdh",
154                 .cra_driver_name = "ecdh-generic",
155                 .cra_priority = 100,
156                 .cra_module = THIS_MODULE,
157                 .cra_ctxsize = sizeof(struct ecdh_ctx),
158         },
159 };
160
161 static int ecdh_init(void)
162 {
163         return crypto_register_kpp(&ecdh);
164 }
165
166 static void ecdh_exit(void)
167 {
168         crypto_unregister_kpp(&ecdh);
169 }
170
171 module_init(ecdh_init);
172 module_exit(ecdh_exit);
173 MODULE_ALIAS_CRYPTO("ecdh");
174 MODULE_LICENSE("GPL");
175 MODULE_DESCRIPTION("ECDH generic algorithm");