1/*
2 * Copyright (c) 2016, Intel Corporation
3 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
4 *
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License
7 * as published by the Free Software Foundation; either version
8 * 2 of the License, or (at your option) any later version.
9 */
10#include <linux/kernel.h>
11#include <linux/export.h>
12#include <linux/err.h>
13#include <linux/string.h>
14#include <crypto/dh.h>
15#include <crypto/kpp.h>
16
17#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 4 * sizeof(int))
18
19static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
20{
21 if (!dst || size > end - dst)
22 return NULL;
23 memcpy(dst, src, size);
24 return dst + size;
25}
26
27static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
28{
29 memcpy(dst, src, size);
30 return src + size;
31}
32
33static inline unsigned int dh_data_size(const struct dh *p)
34{
35 return p->key_size + p->p_size + p->q_size + p->g_size;
36}
37
38unsigned int crypto_dh_key_len(const struct dh *p)
39{
40 return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
41}
42EXPORT_SYMBOL_GPL(crypto_dh_key_len);
43
44int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
45{
46 u8 *ptr = buf;
47 u8 * const end = ptr + len;
48 struct kpp_secret secret = {
49 .type = CRYPTO_KPP_SECRET_TYPE_DH,
50 .len = len
51 };
52
53 if (unlikely(!len))
54 return -EINVAL;
55
56 ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
57 ptr = dh_pack_data(ptr, end, &params->key_size,
58 sizeof(params->key_size));
59 ptr = dh_pack_data(ptr, end, &params->p_size, sizeof(params->p_size));
60 ptr = dh_pack_data(ptr, end, &params->q_size, sizeof(params->q_size));
61 ptr = dh_pack_data(ptr, end, &params->g_size, sizeof(params->g_size));
62 ptr = dh_pack_data(ptr, end, params->key, params->key_size);
63 ptr = dh_pack_data(ptr, end, params->p, params->p_size);
64 ptr = dh_pack_data(ptr, end, params->q, params->q_size);
65 ptr = dh_pack_data(ptr, end, params->g, params->g_size);
66 if (ptr != end)
67 return -EINVAL;
68 return 0;
69}
70EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
71
72int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
73{
74 const u8 *ptr = buf;
75 struct kpp_secret secret;
76
77 if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
78 return -EINVAL;
79
80 ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
81 if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
82 return -EINVAL;
83
84 ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
85 ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
86 ptr = dh_unpack_data(&params->q_size, ptr, sizeof(params->q_size));
87 ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
88 if (secret.len != crypto_dh_key_len(params))
89 return -EINVAL;
90
91 /*
92 * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
93 * some drivers assume otherwise.
94 */
95 if (params->key_size > params->p_size ||
96 params->g_size > params->p_size || params->q_size > params->p_size)
97 return -EINVAL;
98
99 /* Don't allocate memory. Set pointers to data within
100 * the given buffer
101 */
102 params->key = (void *)ptr;
103 params->p = (void *)(ptr + params->key_size);
104 params->q = (void *)(ptr + params->key_size + params->p_size);
105 params->g = (void *)(ptr + params->key_size + params->p_size +
106 params->q_size);
107
108 /*
109 * Don't permit 'p' to be 0. It's not a prime number, and it's subject
110 * to corner cases such as 'mod 0' being undefined or
111 * crypto_kpp_maxsize() returning 0.
112 */
113 if (memchr_inv(params->p, 0, params->p_size) == NULL)
114 return -EINVAL;
115
116 /* It is permissible to not provide Q. */
117 if (params->q_size == 0)
118 params->q = NULL;
119
120 return 0;
121}
122EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
123