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);