xref: /openbmc/linux/crypto/dh_helper.c (revision 4f2c0a4acffbec01079c28f839422e64ddeff004)
12874c5fdSThomas Gleixner // SPDX-License-Identifier: GPL-2.0-or-later
2802c7f1cSSalvatore Benedetto /*
3802c7f1cSSalvatore Benedetto  * Copyright (c) 2016, Intel Corporation
4802c7f1cSSalvatore Benedetto  * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
5802c7f1cSSalvatore Benedetto  */
6802c7f1cSSalvatore Benedetto #include <linux/kernel.h>
7802c7f1cSSalvatore Benedetto #include <linux/export.h>
8802c7f1cSSalvatore Benedetto #include <linux/err.h>
9802c7f1cSSalvatore Benedetto #include <linux/string.h>
10802c7f1cSSalvatore Benedetto #include <crypto/dh.h>
11802c7f1cSSalvatore Benedetto #include <crypto/kpp.h>
12802c7f1cSSalvatore Benedetto 
1348c6d8b8SNicolai Stange #define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))
14802c7f1cSSalvatore Benedetto 
dh_pack_data(u8 * dst,u8 * end,const void * src,size_t size)15d6e43798SEric Biggers static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
16802c7f1cSSalvatore Benedetto {
17d6e43798SEric Biggers 	if (!dst || size > end - dst)
18d6e43798SEric Biggers 		return NULL;
19802c7f1cSSalvatore Benedetto 	memcpy(dst, src, size);
20802c7f1cSSalvatore Benedetto 	return dst + size;
21802c7f1cSSalvatore Benedetto }
22802c7f1cSSalvatore Benedetto 
dh_unpack_data(void * dst,const void * src,size_t size)23802c7f1cSSalvatore Benedetto static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
24802c7f1cSSalvatore Benedetto {
25802c7f1cSSalvatore Benedetto 	memcpy(dst, src, size);
26802c7f1cSSalvatore Benedetto 	return src + size;
27802c7f1cSSalvatore Benedetto }
28802c7f1cSSalvatore Benedetto 
dh_data_size(const struct dh * p)29cb195b36STudor-Dan Ambarus static inline unsigned int dh_data_size(const struct dh *p)
30802c7f1cSSalvatore Benedetto {
3148c6d8b8SNicolai Stange 	return p->key_size + p->p_size + p->g_size;
32802c7f1cSSalvatore Benedetto }
33802c7f1cSSalvatore Benedetto 
crypto_dh_key_len(const struct dh * p)345b3f3a8bSTudor-Dan Ambarus unsigned int crypto_dh_key_len(const struct dh *p)
35802c7f1cSSalvatore Benedetto {
36802c7f1cSSalvatore Benedetto 	return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
37802c7f1cSSalvatore Benedetto }
38802c7f1cSSalvatore Benedetto EXPORT_SYMBOL_GPL(crypto_dh_key_len);
39802c7f1cSSalvatore Benedetto 
crypto_dh_encode_key(char * buf,unsigned int len,const struct dh * params)40802c7f1cSSalvatore Benedetto int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
41802c7f1cSSalvatore Benedetto {
42802c7f1cSSalvatore Benedetto 	u8 *ptr = buf;
43d6e43798SEric Biggers 	u8 * const end = ptr + len;
44802c7f1cSSalvatore Benedetto 	struct kpp_secret secret = {
45802c7f1cSSalvatore Benedetto 		.type = CRYPTO_KPP_SECRET_TYPE_DH,
46802c7f1cSSalvatore Benedetto 		.len = len
47802c7f1cSSalvatore Benedetto 	};
48802c7f1cSSalvatore Benedetto 
49d6e43798SEric Biggers 	if (unlikely(!len))
50802c7f1cSSalvatore Benedetto 		return -EINVAL;
51802c7f1cSSalvatore Benedetto 
52d6e43798SEric Biggers 	ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
53d6e43798SEric Biggers 	ptr = dh_pack_data(ptr, end, &params->key_size,
54d6e43798SEric Biggers 			   sizeof(params->key_size));
55d6e43798SEric Biggers 	ptr = dh_pack_data(ptr, end, &params->p_size, sizeof(params->p_size));
56d6e43798SEric Biggers 	ptr = dh_pack_data(ptr, end, &params->g_size, sizeof(params->g_size));
57d6e43798SEric Biggers 	ptr = dh_pack_data(ptr, end, params->key, params->key_size);
58d6e43798SEric Biggers 	ptr = dh_pack_data(ptr, end, params->p, params->p_size);
59d6e43798SEric Biggers 	ptr = dh_pack_data(ptr, end, params->g, params->g_size);
60d6e43798SEric Biggers 	if (ptr != end)
61802c7f1cSSalvatore Benedetto 		return -EINVAL;
62802c7f1cSSalvatore Benedetto 	return 0;
63802c7f1cSSalvatore Benedetto }
64802c7f1cSSalvatore Benedetto EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
65802c7f1cSSalvatore Benedetto 
__crypto_dh_decode_key(const char * buf,unsigned int len,struct dh * params)66*fae19893SNicolai Stange int __crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
67802c7f1cSSalvatore Benedetto {
68802c7f1cSSalvatore Benedetto 	const u8 *ptr = buf;
69802c7f1cSSalvatore Benedetto 	struct kpp_secret secret;
70802c7f1cSSalvatore Benedetto 
71802c7f1cSSalvatore Benedetto 	if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
72802c7f1cSSalvatore Benedetto 		return -EINVAL;
73802c7f1cSSalvatore Benedetto 
74802c7f1cSSalvatore Benedetto 	ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
75802c7f1cSSalvatore Benedetto 	if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
76802c7f1cSSalvatore Benedetto 		return -EINVAL;
77802c7f1cSSalvatore Benedetto 
78802c7f1cSSalvatore Benedetto 	ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
79802c7f1cSSalvatore Benedetto 	ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
80802c7f1cSSalvatore Benedetto 	ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
81802c7f1cSSalvatore Benedetto 	if (secret.len != crypto_dh_key_len(params))
82802c7f1cSSalvatore Benedetto 		return -EINVAL;
83802c7f1cSSalvatore Benedetto 
84*fae19893SNicolai Stange 	/* Don't allocate memory. Set pointers to data within
85*fae19893SNicolai Stange 	 * the given buffer
86*fae19893SNicolai Stange 	 */
87*fae19893SNicolai Stange 	params->key = (void *)ptr;
88*fae19893SNicolai Stange 	params->p = (void *)(ptr + params->key_size);
89*fae19893SNicolai Stange 	params->g = (void *)(ptr + params->key_size + params->p_size);
90*fae19893SNicolai Stange 
91*fae19893SNicolai Stange 	return 0;
92*fae19893SNicolai Stange }
93*fae19893SNicolai Stange 
crypto_dh_decode_key(const char * buf,unsigned int len,struct dh * params)94*fae19893SNicolai Stange int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
95*fae19893SNicolai Stange {
96*fae19893SNicolai Stange 	int err;
97*fae19893SNicolai Stange 
98*fae19893SNicolai Stange 	err = __crypto_dh_decode_key(buf, len, params);
99*fae19893SNicolai Stange 	if (err)
100*fae19893SNicolai Stange 		return err;
101*fae19893SNicolai Stange 
102ccd9888fSEric Biggers 	/*
103ccd9888fSEric Biggers 	 * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
104ccd9888fSEric Biggers 	 * some drivers assume otherwise.
105ccd9888fSEric Biggers 	 */
106ccd9888fSEric Biggers 	if (params->key_size > params->p_size ||
10748c6d8b8SNicolai Stange 	    params->g_size > params->p_size)
108ccd9888fSEric Biggers 		return -EINVAL;
109ccd9888fSEric Biggers 
110199512b1SEric Biggers 	/*
111199512b1SEric Biggers 	 * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
112199512b1SEric Biggers 	 * to corner cases such as 'mod 0' being undefined or
113199512b1SEric Biggers 	 * crypto_kpp_maxsize() returning 0.
114199512b1SEric Biggers 	 */
115199512b1SEric Biggers 	if (memchr_inv(params->p, 0, params->p_size) == NULL)
116199512b1SEric Biggers 		return -EINVAL;
117199512b1SEric Biggers 
118802c7f1cSSalvatore Benedetto 	return 0;
119802c7f1cSSalvatore Benedetto }
120802c7f1cSSalvatore Benedetto EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
121