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 License
  7 * as published by the Free Software Foundation; either version
  8 * 2 of the License, 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 unsigned int dh_data_size(const struct dh *p)
 32{
 33	return p->key_size + p->p_size + p->g_size;
 34}
 35
 36unsigned int 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	/*
 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}
111EXPORT_SYMBOL_GPL(crypto_dh_decode_key);