path: root/crypto/dh_helper.c (plain)
blob: 14539904416e93cebb370db4418a3e038382b958

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 Licence
7	* as published by the Free Software Foundation; either version
8	* 2 of the Licence, 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) + 3 * sizeof(int))
18
19	static inline u8 *dh_pack_data(void *dst, const void *src, size_t size)
20	{
21	memcpy(dst, src, size);
22	return dst + size;
23	}
24
25	static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
26	{
27	memcpy(dst, src, size);
28	return src + size;
29	}
30
31	static inline int dh_data_size(const struct dh *p)
32	{
33	return p->key_size + p->p_size + p->g_size;
34	}
35
36	int crypto_dh_key_len(const struct dh *p)
37	{
38	return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
39	}
40	EXPORT_SYMBOL_GPL(crypto_dh_key_len);
41
42	int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
43	{
44	u8 *ptr = buf;
45	struct kpp_secret secret = {
46	.type = CRYPTO_KPP_SECRET_TYPE_DH,
47	.len = len
48	};
49
50	if (unlikely(!buf))
51	return -EINVAL;
52
53	if (len != crypto_dh_key_len(params))
54	return -EINVAL;
55
56	ptr = dh_pack_data(ptr, &secret, sizeof(secret));
57	ptr = dh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
58	ptr = dh_pack_data(ptr, &params->p_size, sizeof(params->p_size));
59	ptr = dh_pack_data(ptr, &params->g_size, sizeof(params->g_size));
60	ptr = dh_pack_data(ptr, params->key, params->key_size);
61	ptr = dh_pack_data(ptr, params->p, params->p_size);
62	dh_pack_data(ptr, params->g, params->g_size);
63
64	return 0;
65	}
66	EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
67
68	int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
69	{
70	const u8 *ptr = buf;
71	struct kpp_secret secret;
72
73	if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
74	return -EINVAL;
75
76	ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
77	if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
78	return -EINVAL;
79
80	ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
81	ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
82	ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
83	if (secret.len != crypto_dh_key_len(params))
84	return -EINVAL;
85
86	/*
87	* Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
88	* some drivers assume otherwise.
89	*/
90	if (params->key_size > params->p_size ||
91	params->g_size > params->p_size)
92	return -EINVAL;
93
94	/* Don't allocate memory. Set pointers to data within
95	* the given buffer
96	*/
97	params->key = (void *)ptr;
98	params->p = (void *)(ptr + params->key_size);
99	params->g = (void *)(ptr + params->key_size + params->p_size);
100
101	/*
102	* Don't permit 'p' to be 0. It's not a prime number, and it's subject
103	* to corner cases such as 'mod 0' being undefined or
104	* crypto_kpp_maxsize() returning 0.
105	*/
106	if (memchr_inv(params->p, 0, params->p_size) == NULL)
107	return -EINVAL;
108
109	return 0;
110	}
111	EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
112