136 lines
5.7 KiB
C
136 lines
5.7 KiB
C
/**
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* \file hkdf.h
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*
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* \brief This file contains the HKDF interface.
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*
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* The HMAC-based Extract-and-Expand Key Derivation Function (HKDF) is
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* specified by RFC 5869.
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*/
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/*
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* Copyright (C) 2016-2018, ARM Limited, All Rights Reserved
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*/
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#ifndef MBEDTLS_HKDF_H
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#define MBEDTLS_HKDF_H
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#include "md.h"
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/**
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* \name HKDF Error codes
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* \{
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*/
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#define MBEDTLS_ERR_HKDF_BAD_INPUT_DATA -0x5F80 /**< Bad input parameters to function. */
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/* \} name */
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* \brief This is the HMAC-based Extract-and-Expand Key Derivation Function
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* (HKDF).
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*
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* \param md A hash function; md.size denotes the length of the hash
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* function output in bytes.
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* \param salt An optional salt value (a non-secret random value);
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* if the salt is not provided, a string of all zeros of
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* md.size length is used as the salt.
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* \param salt_len The length in bytes of the optional \p salt.
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* \param ikm The input keying material.
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* \param ikm_len The length in bytes of \p ikm.
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* \param info An optional context and application specific information
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* string. This can be a zero-length string.
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* \param info_len The length of \p info in bytes.
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* \param okm The output keying material of \p okm_len bytes.
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* \param okm_len The length of the output keying material in bytes. This
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* must be less than or equal to 255 * md.size bytes.
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*
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* \return 0 on success.
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* \return #MBEDTLS_ERR_HKDF_BAD_INPUT_DATA when the parameters are invalid.
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* \return An MBEDTLS_ERR_MD_* error for errors returned from the underlying
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* MD layer.
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*/
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int mbedtls_hkdf( const mbedtls_md_info_t *md, const unsigned char *salt,
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size_t salt_len, const unsigned char *ikm, size_t ikm_len,
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const unsigned char *info, size_t info_len,
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unsigned char *okm, size_t okm_len );
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/**
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* \brief Take the input keying material \p ikm and extract from it a
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* fixed-length pseudorandom key \p prk.
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*
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* \warning This function should only be used if the security of it has been
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* studied and established in that particular context (eg. TLS 1.3
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* key schedule). For standard HKDF security guarantees use
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* \c mbedtls_hkdf instead.
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*
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* \param md A hash function; md.size denotes the length of the
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* hash function output in bytes.
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* \param salt An optional salt value (a non-secret random value);
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* if the salt is not provided, a string of all zeros
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* of md.size length is used as the salt.
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* \param salt_len The length in bytes of the optional \p salt.
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* \param ikm The input keying material.
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* \param ikm_len The length in bytes of \p ikm.
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* \param[out] prk A pseudorandom key of at least md.size bytes.
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*
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* \return 0 on success.
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* \return #MBEDTLS_ERR_HKDF_BAD_INPUT_DATA when the parameters are invalid.
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* \return An MBEDTLS_ERR_MD_* error for errors returned from the underlying
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* MD layer.
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*/
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int mbedtls_hkdf_extract( const mbedtls_md_info_t *md,
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const unsigned char *salt, size_t salt_len,
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const unsigned char *ikm, size_t ikm_len,
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unsigned char *prk );
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/**
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* \brief Expand the supplied \p prk into several additional pseudorandom
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* keys, which is the output of the HKDF.
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*
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* \warning This function should only be used if the security of it has been
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* studied and established in that particular context (eg. TLS 1.3
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* key schedule). For standard HKDF security guarantees use
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* \c mbedtls_hkdf instead.
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*
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* \param md A hash function; md.size denotes the length of the hash
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* function output in bytes.
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* \param prk A pseudorandom key of at least md.size bytes. \p prk is
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* usually the output from the HKDF extract step.
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* \param prk_len The length in bytes of \p prk.
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* \param info An optional context and application specific information
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* string. This can be a zero-length string.
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* \param info_len The length of \p info in bytes.
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* \param okm The output keying material of \p okm_len bytes.
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* \param okm_len The length of the output keying material in bytes. This
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* must be less than or equal to 255 * md.size bytes.
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*
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* \return 0 on success.
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* \return #MBEDTLS_ERR_HKDF_BAD_INPUT_DATA when the parameters are invalid.
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* \return An MBEDTLS_ERR_MD_* error for errors returned from the underlying
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* MD layer.
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*/
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int mbedtls_hkdf_expand( const mbedtls_md_info_t *md, const unsigned char *prk,
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size_t prk_len, const unsigned char *info,
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size_t info_len, unsigned char *okm, size_t okm_len );
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#ifdef __cplusplus
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}
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#endif
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#endif /* hkdf.h */
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