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diff --git a/include/mbedtls/hkdf.h b/include/mbedtls/hkdf.h
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+/**
+ * \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 */