1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 /* 3 * Diffie-Hellman secret to be used with kpp API along with helper functions 4 * 5 * Copyright (c) 2016, Intel Corporation 6 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com> 7 */ 8 #ifndef _CRYPTO_DH_ 9 #define _CRYPTO_DH_ 10 11 /** 12 * DOC: DH Helper Functions 13 * 14 * To use DH with the KPP cipher API, the following data structure and 15 * functions should be used. 16 * 17 * To use DH with KPP, the following functions should be used to operate on 18 * a DH private key. The packet private key that can be set with 19 * the KPP API function call of crypto_kpp_set_secret. 20 */ 21 22 /** 23 * struct dh - define a DH private key 24 * 25 * @key: Private DH key 26 * @p: Diffie-Hellman parameter P 27 * @g: Diffie-Hellman generator G 28 * @key_size: Size of the private DH key 29 * @p_size: Size of DH parameter P 30 * @g_size: Size of DH generator G 31 */ 32 struct dh { 33 const void *key; 34 const void *p; 35 const void *g; 36 unsigned int key_size; 37 unsigned int p_size; 38 unsigned int g_size; 39 }; 40 41 /** 42 * crypto_dh_key_len() - Obtain the size of the private DH key 43 * @params: private DH key 44 * 45 * This function returns the packet DH key size. A caller can use that 46 * with the provided DH private key reference to obtain the required 47 * memory size to hold a packet key. 48 * 49 * Return: size of the key in bytes 50 */ 51 unsigned int crypto_dh_key_len(const struct dh *params); 52 53 /** 54 * crypto_dh_encode_key() - encode the private key 55 * @buf: Buffer allocated by the caller to hold the packet DH 56 * private key. The buffer should be at least crypto_dh_key_len 57 * bytes in size. 58 * @len: Length of the packet private key buffer 59 * @params: Buffer with the caller-specified private key 60 * 61 * The DH implementations operate on a packet representation of the private 62 * key. 63 * 64 * Return: -EINVAL if buffer has insufficient size, 0 on success 65 */ 66 int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params); 67 68 /** 69 * crypto_dh_decode_key() - decode a private key 70 * @buf: Buffer holding a packet key that should be decoded 71 * @len: Length of the packet private key buffer 72 * @params: Buffer allocated by the caller that is filled with the 73 * unpacked DH private key. 74 * 75 * The unpacking obtains the private key by pointing @p to the correct location 76 * in @buf. Thus, both pointers refer to the same memory. 77 * 78 * Return: -EINVAL if buffer has insufficient size, 0 on success 79 */ 80 int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params); 81 82 /** 83 * __crypto_dh_decode_key() - decode a private key without parameter checks 84 * @buf: Buffer holding a packet key that should be decoded 85 * @len: Length of the packet private key buffer 86 * @params: Buffer allocated by the caller that is filled with the 87 * unpacked DH private key. 88 * 89 * Internal function providing the same services as the exported 90 * crypto_dh_decode_key(), but without any of those basic parameter 91 * checks conducted by the latter. 92 * 93 * Return: -EINVAL if buffer has insufficient size, 0 on success 94 */ 95 int __crypto_dh_decode_key(const char *buf, unsigned int len, 96 struct dh *params); 97 98 #endif 99