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 
dh_pack_data(u8 * dst,u8 * end,const void * src,size_t size)15 static 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 
dh_unpack_data(void * dst,const void * src,size_t size)23 static 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 
dh_data_size(const struct dh * p)29 static inline unsigned int dh_data_size(const struct dh *p)
30 {
31 	return p->key_size + p->p_size + p->g_size;
32 }
33 
crypto_dh_key_len(const struct dh * p)34 unsigned int crypto_dh_key_len(const struct dh *p)
35 {
36 	return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
37 }
38 EXPORT_SYMBOL_GPL(crypto_dh_key_len);
39 
crypto_dh_encode_key(char * buf,unsigned int len,const struct dh * params)40 int 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 }
64 EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
65 
__crypto_dh_decode_key(const char * buf,unsigned int len,struct dh * params)66 int __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 
crypto_dh_decode_key(const char * buf,unsigned int len,struct dh * params)94 int 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 }
120 EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
121