1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (c) 2016, Intel Corporation
4 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
5 */
6#include <linux/kernel.h>
7#include <linux/export.h>
8#include <linux/err.h>
9#include <linux/string.h>
10#include <crypto/dh.h>
11#include <crypto/kpp.h>
12
13#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))
14
15static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
16{
17	if (!dst || size > end - dst)
18		return NULL;
19	memcpy(dst, src, size);
20	return dst + size;
21}
22
23static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
24{
25	memcpy(dst, src, size);
26	return src + size;
27}
28
29static inline unsigned int dh_data_size(const struct dh *p)
30{
31	return p->key_size + p->p_size + p->g_size;
32}
33
34unsigned int crypto_dh_key_len(const struct dh *p)
35{
36	return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
37}
38EXPORT_SYMBOL_GPL(crypto_dh_key_len);
39
40int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
41{
42	u8 *ptr = buf;
43	u8 * const end = ptr + len;
44	struct kpp_secret secret = {
45		.type = CRYPTO_KPP_SECRET_TYPE_DH,
46		.len = len
47	};
48
49	if (unlikely(!len))
50		return -EINVAL;
51
52	ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
53	ptr = dh_pack_data(ptr, end, &params->key_size,
54			   sizeof(params->key_size));
55	ptr = dh_pack_data(ptr, end, &params->p_size, sizeof(params->p_size));
56	ptr = dh_pack_data(ptr, end, &params->g_size, sizeof(params->g_size));
57	ptr = dh_pack_data(ptr, end, params->key, params->key_size);
58	ptr = dh_pack_data(ptr, end, params->p, params->p_size);
59	ptr = dh_pack_data(ptr, end, params->g, params->g_size);
60	if (ptr != end)
61		return -EINVAL;
62	return 0;
63}
64EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
65
66int __crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
67{
68	const u8 *ptr = buf;
69	struct kpp_secret secret;
70
71	if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
72		return -EINVAL;
73
74	ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
75	if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
76		return -EINVAL;
77
78	ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
79	ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
80	ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
81	if (secret.len != crypto_dh_key_len(params))
82		return -EINVAL;
83
84	/* Don't allocate memory. Set pointers to data within
85	 * the given buffer
86	 */
87	params->key = (void *)ptr;
88	params->p = (void *)(ptr + params->key_size);
89	params->g = (void *)(ptr + params->key_size + params->p_size);
90
91	return 0;
92}
93
94int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
95{
96	int err;
97
98	err = __crypto_dh_decode_key(buf, len, params);
99	if (err)
100		return err;
101
102	/*
103	 * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
104	 * some drivers assume otherwise.
105	 */
106	if (params->key_size > params->p_size ||
107	    params->g_size > params->p_size)
108		return -EINVAL;
109
110	/*
111	 * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
112	 * to corner cases such as 'mod 0' being undefined or
113	 * crypto_kpp_maxsize() returning 0.
114	 */
115	if (memchr_inv(params->p, 0, params->p_size) == NULL)
116		return -EINVAL;
117
118	return 0;
119}
120EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
121