diff --git a/library/ssl_tls13_invasive.h b/library/ssl_tls13_invasive.h
new file mode 100644
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--- /dev/null
+++ b/library/ssl_tls13_invasive.h
@@ -0,0 +1,63 @@
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+#ifndef MBEDTLS_SSL_TLS13_INVASIVE_H
+#define MBEDTLS_SSL_TLS13_INVASIVE_H
+
+#include "common.h"
+
+#if defined(MBEDTLS_PSA_CRYPTO_C)
+#include "psa/crypto.h"
+#endif
+
+#if defined(MBEDTLS_TEST_HOOKS)
+
+#if defined(MBEDTLS_PSA_CRYPTO_C)
+
+/**
+ *  \brief  Expand the supplied \p prk into several additional pseudorandom
+ *          keys, which is the output of the HKDF.
+ *
+ *  \param  alg       The HMAC algorithm to use (\c #PSA_ALG_HMAC( PSA_ALG_XXX )
+ *                    value such that PSA_ALG_XXX is a hash algorithm and
+ *                    #PSA_ALG_IS_HMAC(\p alg) is true).
+ *  \param  prk       A pseudorandom key of \p prk_len 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 * #PSA_HASH_LENGTH( \p alg ) bytes.
+ *
+ *  \return 0 on success.
+ *  \return #PSA_ERROR_INVALID_ARGUMENT when the parameters are invalid.
+ *  \return An PSA_ERROR_* error for errors returned from the underlying
+ *          PSA layer.
+ */
+psa_status_t mbedtls_psa_hkdf_expand( psa_algorithm_t alg,
+                                      const unsigned char *prk, size_t prk_len,
+                                      const unsigned char *info, size_t info_len,
+                                      unsigned char *okm, size_t okm_len );
+
+#endif /* MBEDTLS_PSA_CRYPTO_C */
+
+#endif /* MBEDTLS_TEST_HOOKS */
+
+#endif /* MBEDTLS_SSL_TLS13_INVASIVE_H */