diff --git a/library/debug_internal.h b/library/debug_internal.h
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+/**
+ * \file debug_internal.h
+ *
+ * \brief Internal part of the public "debug.h".
+ */
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+#ifndef MBEDTLS_DEBUG_INTERNAL_H
+#define MBEDTLS_DEBUG_INTERNAL_H
+
+#include "mbedtls/debug.h"
+
+/**
+ * \brief    Print a message to the debug output. This function is always used
+ *          through the MBEDTLS_SSL_DEBUG_MSG() macro, which supplies the ssl
+ *          context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the message has occurred in
+ * \param line      line number the message has occurred at
+ * \param format    format specifier, in printf format
+ * \param ...       variables used by the format specifier
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_msg(const mbedtls_ssl_context *ssl, int level,
+                             const char *file, int line,
+                             const char *format, ...) MBEDTLS_PRINTF_ATTRIBUTE(5, 6);
+
+/**
+ * \brief   Print the return value of a function to the debug output. This
+ *          function is always used through the MBEDTLS_SSL_DEBUG_RET() macro,
+ *          which supplies the ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      the name of the function that returned the error
+ * \param ret       the return code value
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_ret(const mbedtls_ssl_context *ssl, int level,
+                             const char *file, int line,
+                             const char *text, int ret);
+
+/**
+ * \brief   Output a buffer of size len bytes to the debug output. This function
+ *          is always used through the MBEDTLS_SSL_DEBUG_BUF() macro,
+ *          which supplies the ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      a name or label for the buffer being dumped. Normally the
+ *                  variable or buffer name
+ * \param buf       the buffer to be outputted
+ * \param len       length of the buffer
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_buf(const mbedtls_ssl_context *ssl, int level,
+                             const char *file, int line, const char *text,
+                             const unsigned char *buf, size_t len);
+
+#if defined(MBEDTLS_BIGNUM_C)
+/**
+ * \brief   Print a MPI variable to the debug output. This function is always
+ *          used through the MBEDTLS_SSL_DEBUG_MPI() macro, which supplies the
+ *          ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      a name or label for the MPI being output. Normally the
+ *                  variable name
+ * \param X         the MPI variable
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_mpi(const mbedtls_ssl_context *ssl, int level,
+                             const char *file, int line,
+                             const char *text, const mbedtls_mpi *X);
+#endif
+
+#if defined(MBEDTLS_ECP_LIGHT)
+/**
+ * \brief   Print an ECP point to the debug output. This function is always
+ *          used through the MBEDTLS_SSL_DEBUG_ECP() macro, which supplies the
+ *          ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      a name or label for the ECP point being output. Normally the
+ *                  variable name
+ * \param X         the ECP point
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_ecp(const mbedtls_ssl_context *ssl, int level,
+                             const char *file, int line,
+                             const char *text, const mbedtls_ecp_point *X);
+#endif
+
+#if defined(MBEDTLS_X509_CRT_PARSE_C) && !defined(MBEDTLS_X509_REMOVE_INFO)
+/**
+ * \brief   Print a X.509 certificate structure to the debug output. This
+ *          function is always used through the MBEDTLS_SSL_DEBUG_CRT() macro,
+ *          which supplies the ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      a name or label for the certificate being output
+ * \param crt       X.509 certificate structure
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_crt(const mbedtls_ssl_context *ssl, int level,
+                             const char *file, int line,
+                             const char *text, const mbedtls_x509_crt *crt);
+#endif
+
+/* Note: the MBEDTLS_ECDH_C guard here is mandatory because this debug function
+         only works for the built-in implementation. */
+#if defined(MBEDTLS_KEY_EXCHANGE_SOME_ECDH_OR_ECDHE_ANY_ENABLED) && \
+    defined(MBEDTLS_ECDH_C)
+typedef enum {
+    MBEDTLS_DEBUG_ECDH_Q,
+    MBEDTLS_DEBUG_ECDH_QP,
+    MBEDTLS_DEBUG_ECDH_Z,
+} mbedtls_debug_ecdh_attr;
+
+/**
+ * \brief   Print a field of the ECDH structure in the SSL context to the debug
+ *          output. This function is always used through the
+ *          MBEDTLS_SSL_DEBUG_ECDH() macro, which supplies the ssl context, file
+ *          and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param ecdh      the ECDH context
+ * \param attr      the identifier of the attribute being output
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_printf_ecdh(const mbedtls_ssl_context *ssl, int level,
+                               const char *file, int line,
+                               const mbedtls_ecdh_context *ecdh,
+                               mbedtls_debug_ecdh_attr attr);
+#endif /* MBEDTLS_KEY_EXCHANGE_SOME_ECDH_OR_ECDHE_ANY_ENABLED &&
+          MBEDTLS_ECDH_C */
+
+#endif /* MBEDTLS_DEBUG_INTERNAL_H */