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
19static 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
25static 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
31static inline int dh_data_size(const struct dh *p)
32{
33	return p->key_size + p->p_size + p->g_size;
34}
35
36int crypto_dh_key_len(const struct dh *p)
37{
38	return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
39}
40EXPORT_SYMBOL_GPL(crypto_dh_key_len);
41
42int 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}
66EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
67
68int 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	/* Don't allocate memory. Set pointers to data within
87	 * the given buffer
88	 */
89	params->key = (void *)ptr;
90	params->p = (void *)(ptr + params->key_size);
91	params->g = (void *)(ptr + params->key_size + params->p_size);
92
93	return 0;
94}
95EXPORT_SYMBOL_GPL(crypto_dh_decode_key);