| /** |
| * \file hkdf.h |
| * |
| * \brief This file contains the HKDF interface. |
| * |
| * The HMAC-based Extract-and-Expand Key Derivation Function (HKDF) is |
| * specified by RFC 5869. |
| */ |
| /* |
| * Copyright The Mbed TLS Contributors |
| * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later |
| */ |
| #ifndef MBEDTLS_HKDF_H |
| #define MBEDTLS_HKDF_H |
| |
| #include "mbedtls/build_info.h" |
| |
| #include "mbedtls/md.h" |
| |
| /** |
| * \name HKDF Error codes |
| * \{ |
| */ |
| /** Bad input parameters to function. */ |
| #define MBEDTLS_ERR_HKDF_BAD_INPUT_DATA -0x5F80 |
| /** \} name */ |
| |
| #ifdef __cplusplus |
| extern "C" { |
| #endif |
| |
| /** |
| * \brief This is the HMAC-based Extract-and-Expand Key Derivation Function |
| * (HKDF). |
| * |
| * \param md A hash function; md.size denotes the length of the hash |
| * function output in bytes. |
| * \param salt An optional salt value (a non-secret random value); |
| * if the salt is not provided, a string of all zeros of |
| * md.size length is used as the salt. |
| * \param salt_len The length in bytes of the optional \p salt. |
| * \param ikm The input keying material. |
| * \param ikm_len The length in bytes of \p ikm. |
| * \param info An optional context and application specific information |
| * string. This can be a zero-length string. |
| * \param info_len The length of \p info in bytes. |
| * \param okm The output keying material of \p okm_len bytes. |
| * \param okm_len The length of the output keying material in bytes. This |
| * must be less than or equal to 255 * md.size bytes. |
| * |
| * \return 0 on success. |
| * \return #MBEDTLS_ERR_HKDF_BAD_INPUT_DATA when the parameters are invalid. |
| * \return An MBEDTLS_ERR_MD_* error for errors returned from the underlying |
| * MD layer. |
| */ |
| int mbedtls_hkdf(const mbedtls_md_info_t *md, const unsigned char *salt, |
| size_t salt_len, const unsigned char *ikm, size_t ikm_len, |
| const unsigned char *info, size_t info_len, |
| unsigned char *okm, size_t okm_len); |
| |
| /** |
| * \brief Take the input keying material \p ikm and extract from it a |
| * fixed-length pseudorandom key \p prk. |
| * |
| * \warning This function should only be used if the security of it has been |
| * studied and established in that particular context (eg. TLS 1.3 |
| * key schedule). For standard HKDF security guarantees use |
| * \c mbedtls_hkdf instead. |
| * |
| * \param md A hash function; md.size denotes the length of the |
| * hash function output in bytes. |
| * \param salt An optional salt value (a non-secret random value); |
| * if the salt is not provided, a string of all zeros |
| * of md.size length is used as the salt. |
| * \param salt_len The length in bytes of the optional \p salt. |
| * \param ikm The input keying material. |
| * \param ikm_len The length in bytes of \p ikm. |
| * \param[out] prk A pseudorandom key of at least md.size bytes. |
| * |
| * \return 0 on success. |
| * \return #MBEDTLS_ERR_HKDF_BAD_INPUT_DATA when the parameters are invalid. |
| * \return An MBEDTLS_ERR_MD_* error for errors returned from the underlying |
| * MD layer. |
| */ |
| int mbedtls_hkdf_extract(const mbedtls_md_info_t *md, |
| const unsigned char *salt, size_t salt_len, |
| const unsigned char *ikm, size_t ikm_len, |
| unsigned char *prk); |
| |
| /** |
| * \brief Expand the supplied \p prk into several additional pseudorandom |
| * keys, which is the output of the HKDF. |
| * |
| * \warning This function should only be used if the security of it has been |
| * studied and established in that particular context (eg. TLS 1.3 |
| * key schedule). For standard HKDF security guarantees use |
| * \c mbedtls_hkdf instead. |
| * |
| * \param md A hash function; md.size denotes the length of the hash |
| * function output in bytes. |
| * \param prk A pseudorandom key of at least md.size bytes. \p prk is |
| * usually the output from the HKDF extract step. |
| * \param prk_len The length in bytes of \p prk. |
| * \param info An optional context and application specific information |
| * string. This can be a zero-length string. |
| * \param info_len The length of \p info in bytes. |
| * \param okm The output keying material of \p okm_len bytes. |
| * \param okm_len The length of the output keying material in bytes. This |
| * must be less than or equal to 255 * md.size bytes. |
| * |
| * \return 0 on success. |
| * \return #MBEDTLS_ERR_HKDF_BAD_INPUT_DATA when the parameters are invalid. |
| * \return An MBEDTLS_ERR_MD_* error for errors returned from the underlying |
| * MD layer. |
| */ |
| int mbedtls_hkdf_expand(const mbedtls_md_info_t *md, const unsigned char *prk, |
| size_t prk_len, const unsigned char *info, |
| size_t info_len, unsigned char *okm, size_t okm_len); |
| |
| #ifdef __cplusplus |
| } |
| #endif |
| |
| #endif /* hkdf.h */ |