/src/gnutls/lib/record.c

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/*
 * Copyright (C) 2000-2018 Free Software Foundation, Inc.
 * Copyright (C) 2012-2018 Nikos Mavrogiannopoulos
 * Copyright (C) 2018 Red Hat, Inc.
 *
 * Author: Nikos Mavrogiannopoulos
 *
 * This file is part of GnuTLS.
 *
 * The GnuTLS is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>
 *
 */

/* Functions that are record layer specific, are included in this file.
 */

/* allocate this many bytes more when encrypting or decrypting, to
 * compensate for broken backends such as cryptodev.
 */
#define CIPHER_SLACK_SIZE 32

#include "gnutls_int.h"
#include "errors.h"
#include "debug.h"
#include "cipher.h"
#include "buffers.h"
#include "mbuffers.h"
#include "handshake.h"
#include "hash_int.h"
#include "cipher_int.h"
#include "algorithms.h"
#include "db.h"
#include "auth.h"
#include "num.h"
#include "record.h"
#include "datum.h"
#include "constate.h"
#include "tls13/key_update.h"
#include "ext/heartbeat.h"
#include "state.h"
#include "dtls.h"
#include "dh.h"
#include "random.h"
#include <xsize.h>
#include "locks.h"
#include "system/ktls.h"
#include <intprops.h>

struct tls_record_st {
  uint16_t header_size;
  uint8_t version[2];
  uint64_t sequence; /* DTLS */
  uint16_t length;
  uint16_t packet_size; /* header_size + length */
  content_type_t type;
  uint16_t epoch; /* valid in DTLS only */
#ifdef ENABLE_SSL2
  unsigned v2 : 1; /* whether an SSLv2 client hello */
#endif
  /* the data */
};

/**
 * gnutls_record_disable_padding:
 * @session: is a #gnutls_session_t type.
 *
 * Used to disabled padding in TLS 1.0 and above.  Normally you do not
 * need to use this function, but there are buggy clients that
 * complain if a server pads the encrypted data.  This of course will
 * disable protection against statistical attacks on the data.
 *
 * This function is defunct since 3.1.7. Random padding is disabled
 * by default unless requested using gnutls_record_send_range().
 *
 **/
void gnutls_record_disable_padding(gnutls_session_t session)
{
  return;
}

/**
 * gnutls_transport_set_ptr:
 * @session: is a #gnutls_session_t type.
 * @ptr: is the value.
 *
 * Used to set the first argument of the transport function (for push
 * and pull callbacks). In berkeley style sockets this function will set the
 * connection descriptor.
 *
 **/
void gnutls_transport_set_ptr(gnutls_session_t session,
            gnutls_transport_ptr_t ptr)
{
  session->internals.transport_recv_ptr = ptr;
  session->internals.transport_send_ptr = ptr;
}

/**
 * gnutls_transport_set_ptr2:
 * @session: is a #gnutls_session_t type.
 * @recv_ptr: is the value for the pull function
 * @send_ptr: is the value for the push function
 *
 * Used to set the first argument of the transport function (for push
 * and pull callbacks). In berkeley style sockets this function will set the
 * connection descriptor.  With this function you can use two different
 * pointers for receiving and sending.
 **/
void gnutls_transport_set_ptr2(gnutls_session_t session,
             gnutls_transport_ptr_t recv_ptr,
             gnutls_transport_ptr_t send_ptr)
{
  session->internals.transport_send_ptr = send_ptr;
  session->internals.transport_recv_ptr = recv_ptr;
}

/**
 * gnutls_transport_set_int2:
 * @session: is a #gnutls_session_t type.
 * @recv_fd: is socket descriptor for the pull function
 * @send_fd: is socket descriptor for the push function
 *
 * This function sets the first argument of the transport functions,
 * such as send() and recv() for the default callbacks using the
 * system's socket API. With this function you can set two different
 * descriptors for receiving and sending.
 *
 * This function is equivalent to calling gnutls_transport_set_ptr2()
 * with the descriptors, but requires no casts.
 *
 * Since: 3.1.9
 **/
void gnutls_transport_set_int2(gnutls_session_t session, int recv_fd,
             int send_fd)
{
  session->internals.transport_send_ptr =
    (gnutls_transport_ptr_t)(long)send_fd;
  session->internals.transport_recv_ptr =
    (gnutls_transport_ptr_t)(long)recv_fd;
}

#if 0
/* this will be a macro */
/**
 * gnutls_transport_set_int:
 * @session: is a #gnutls_session_t type.
 * @fd: is the socket descriptor for the connection.
 *
 * This function sets the first argument of the transport function, such
 * as send() and recv() for the default callbacks using the
 * system's socket API.
 *
 * This function is equivalent to calling gnutls_transport_set_ptr()
 * with the descriptor, but requires no casts.
 *
 * Since: 3.1.9
 *
 **/
void gnutls_transport_set_int(gnutls_session_t session, int fd)
{
  session->internals.transport_recv_ptr =
      (gnutls_transport_ptr_t) (long)fd;
  session->internals.transport_send_ptr =
      (gnutls_transport_ptr_t) (long)fd;
}
#endif

/**
 * gnutls_transport_get_ptr:
 * @session: is a #gnutls_session_t type.
 *
 * Used to get the first argument of the transport function (like
 * PUSH and PULL).  This must have been set using
 * gnutls_transport_set_ptr().
 *
 * Returns: The first argument of the transport function.
 **/
gnutls_transport_ptr_t gnutls_transport_get_ptr(gnutls_session_t session)
{
  return session->internals.transport_recv_ptr;
}

/**
 * gnutls_transport_get_ptr2:
 * @session: is a #gnutls_session_t type.
 * @recv_ptr: will hold the value for the pull function
 * @send_ptr: will hold the value for the push function
 *
 * Used to get the arguments of the transport functions (like PUSH
 * and PULL).  These should have been set using
 * gnutls_transport_set_ptr2().
 **/
void gnutls_transport_get_ptr2(gnutls_session_t session,
             gnutls_transport_ptr_t *recv_ptr,
             gnutls_transport_ptr_t *send_ptr)
{
  *recv_ptr = session->internals.transport_recv_ptr;
  *send_ptr = session->internals.transport_send_ptr;
}

/**
 * gnutls_transport_get_int2:
 * @session: is a #gnutls_session_t type.
 * @recv_int: will hold the value for the pull function
 * @send_int: will hold the value for the push function
 *
 * Used to get the arguments of the transport functions (like PUSH
 * and PULL).  These should have been set using
 * gnutls_transport_set_int2().
 *
 * Since: 3.1.9
 **/
void gnutls_transport_get_int2(gnutls_session_t session, int *recv_int,
             int *send_int)
{
  *recv_int = (long)session->internals.transport_recv_ptr;
  *send_int = (long)session->internals.transport_send_ptr;
}

/**
 * gnutls_transport_get_int:
 * @session: is a #gnutls_session_t type.
 *
 * Used to get the first argument of the transport function (like
 * PUSH and PULL).  This must have been set using
 * gnutls_transport_set_int().
 *
 * Returns: The first argument of the transport function.
 *
 * Since: 3.1.9
 **/
int gnutls_transport_get_int(gnutls_session_t session)
{
  return (long)session->internals.transport_recv_ptr;
}

/**
 * gnutls_bye:
 * @session: is a #gnutls_session_t type.
 * @how: is an integer
 *
 * Terminates the current TLS/SSL connection. The connection should
 * have been initiated using gnutls_handshake().  @how should be one
 * of %GNUTLS_SHUT_RDWR, %GNUTLS_SHUT_WR.
 *
 * In case of %GNUTLS_SHUT_RDWR the TLS session gets
 * terminated and further receives and sends will be disallowed.  If
 * the return value is zero you may continue using the underlying
 * transport layer. %GNUTLS_SHUT_RDWR sends an alert containing a close
 * request and waits for the peer to reply with the same message.
 *
 * In case of %GNUTLS_SHUT_WR the TLS session gets terminated
 * and further sends will be disallowed. In order to reuse the
 * connection you should wait for an EOF from the peer.
 * %GNUTLS_SHUT_WR sends an alert containing a close request.
 *
 * Note that not all implementations will properly terminate a TLS
 * connection.  Some of them, usually for performance reasons, will
 * terminate only the underlying transport layer, and thus not
 * distinguishing between a malicious party prematurely terminating
 * the connection and normal termination.
 *
 * This function may also return %GNUTLS_E_AGAIN or
 * %GNUTLS_E_INTERRUPTED; cf.  gnutls_record_get_direction().
 *
 * Returns: %GNUTLS_E_SUCCESS on success, or an error code, see
 *   function documentation for entire semantics.
 **/
int gnutls_bye(gnutls_session_t session, gnutls_close_request_t how)
{
  int ret = 0;

  switch (BYE_STATE) {
  case BYE_STATE0:
    if (!IS_KTLS_ENABLED(session, GNUTLS_KTLS_SEND))
      ret = _gnutls_io_write_flush(session);
    BYE_STATE = BYE_STATE0;
    if (ret < 0) {
      gnutls_assert();
      return ret;
    }
    FALLTHROUGH;
  case BYE_STATE1:
    ret = gnutls_alert_send(session, GNUTLS_AL_WARNING,
          GNUTLS_A_CLOSE_NOTIFY);
    BYE_STATE = BYE_STATE1;
    if (ret < 0) {
      gnutls_assert();
      return ret;
    }
    FALLTHROUGH;
  case BYE_STATE2:
    BYE_STATE = BYE_STATE2;
    if (how == GNUTLS_SHUT_RDWR) {
      if (IS_KTLS_ENABLED(session, GNUTLS_KTLS_SEND)) {
        do {
          ret = _gnutls_ktls_recv_int(
            session, GNUTLS_ALERT, NULL, 0);
        } while (ret == GNUTLS_E_GOT_APPLICATION_DATA);
      } else {
        do {
          ret = _gnutls_recv_int(
            session, GNUTLS_ALERT, NULL, 0,
            NULL,
            session->internals
              .record_timeout_ms);
        } while (ret == GNUTLS_E_GOT_APPLICATION_DATA);
      }

      if (ret >= 0)
        session->internals.may_not_read = 1;

      if (ret < 0) {
        gnutls_assert();
        return ret;
      }
    }
    BYE_STATE = BYE_STATE2;

    break;
  default:
    gnutls_assert();
    return GNUTLS_E_INTERNAL_ERROR;
  }

  BYE_STATE = BYE_STATE0;

  session->internals.may_not_write = 1;
  return 0;
}

inline static void session_unresumable(gnutls_session_t session)
{
  session->internals.resumable = false;
}

/* returns 0 if session is valid
 */
inline static int session_is_valid(gnutls_session_t session)
{
  if (session->internals.invalid_connection != 0)
    return GNUTLS_E_INVALID_SESSION;

  return 0;
}

/* Copies the record version into the headers. The
 * version must have 2 bytes at least.
 */
inline static int copy_record_version(gnutls_session_t session,
              gnutls_handshake_description_t htype,
              uint8_t version[2])
{
  const version_entry_st *lver;

  lver = get_version(session);
  if (session->internals.initial_negotiation_completed ||
      htype != GNUTLS_HANDSHAKE_CLIENT_HELLO ||
      (session->internals.hsk_flags & HSK_HRR_RECEIVED) ||
      session->internals.default_record_version[0] == 0) {
    if (unlikely(lver == NULL))
      return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

    if (lver->tls13_sem) {
      version[0] = 0x03;
      version[1] = 0x03;
    } else {
      version[0] = lver->major;
      version[1] = lver->minor;
    }
  } else {
    version[0] = session->internals.default_record_version[0];
    version[1] = session->internals.default_record_version[1];
  }

  return 0;
}

/* Increments the sequence value
 */
inline static int sequence_increment(gnutls_session_t session, uint64_t *value)
{
  uint64_t snmax = UINT64_C(0xffffffffffffffff);

  if (IS_DTLS(session)) {
    uint64_t mask;

    snmax = UINT64_C(0xffffffffffff);
    mask = snmax;

    if ((*value & mask) == snmax)
      return -1;

    *value = ((*value & mask) + 1) | (*value & ~mask);
  } else {
    if (*value == snmax)
      return -1;

    (*value)++;
  }

  return 0;
}

/* This function behaves exactly like write(). The only difference is
 * that it accepts, the gnutls_session_t and the content_type_t of data to
 * send (if called by the user the Content is specific)
 * It is intended to transfer data, under the current session.
 *
 * @type: The content type to send
 * @htype: If this is a handshake message then the handshake type
 * @epoch_rel: %EPOCH_READ_* or %EPOCH_WRITE_*
 * @data: the data to be sent
 * @data_size: the size of the @data
 * @min_pad: the minimum required padding
 * @mflags: zero or %MBUFFER_FLUSH
 *
 * Oct 30 2001: Removed capability to send data more than MAX_RECORD_SIZE.
 * This makes the function much easier to read, and more error resistant
 * (there were cases were the old function could mess everything up).
 * --nmav
 *
 * This function may accept a NULL pointer for data, and 0 for size, if
 * and only if the previous send was interrupted for some reason.
 *
 */
ssize_t _gnutls_send_tlen_int(gnutls_session_t session, content_type_t type,
            gnutls_handshake_description_t htype,
            unsigned int epoch_rel, const void *_data,
            size_t data_size, size_t min_pad,
            unsigned int mflags)
{
  mbuffer_st *bufel;
  ssize_t cipher_size;
  int retval, ret;
  int send_data_size;
  uint8_t *headers;
  int header_size;
  const uint8_t *data = _data;
  record_parameters_st *record_params;
  size_t max_send_size;
  record_state_st *record_state;
  const version_entry_st *vers = get_version(session);

  ret = _gnutls_epoch_get(session, epoch_rel, &record_params);
  if (ret < 0)
    return gnutls_assert_val(ret);

  /* Safeguard against processing data with an incomplete cipher state. */
  if (!record_params->initialized)
    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  record_state = &record_params->write;

  /* Do not allow null pointer if the send buffer is empty.
   * If the previous send was interrupted then a null pointer is
   * ok, and means to resume.
   */
  if (session->internals.record_send_buffer.byte_length == 0 &&
      (data_size == 0 && _data == NULL)) {
    gnutls_assert();
    return GNUTLS_E_INVALID_REQUEST;
  }

  if (type != GNUTLS_ALERT) /* alert messages are sent anyway */
    if (session_is_valid(session) ||
        session->internals.may_not_write != 0) {
      gnutls_assert();
      return GNUTLS_E_INVALID_SESSION;
    }

  max_send_size = max_record_send_size(session);

  if (data_size > max_send_size) {
    if (IS_DTLS(session))
      return gnutls_assert_val(GNUTLS_E_LARGE_PACKET);

    send_data_size = max_send_size;
  } else
    send_data_size = data_size;

  /* Only encrypt if we don't have data to send
   * from the previous run. - probably interrupted.
   */
  if (mflags != 0 &&
      session->internals.record_send_buffer.byte_length > 0) {
    ret = _gnutls_io_write_flush(session);
    if (ret > 0)
      cipher_size = ret;
    else
      cipher_size = 0;

    retval = session->internals.record_send_buffer_user_size;
  } else {
    if (unlikely((send_data_size == 0 && min_pad == 0)))
      return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

    /* now proceed to packet encryption
     */
    cipher_size = max_record_send_size(session) +
            MAX_RECORD_SEND_OVERHEAD(session);

    bufel = _mbuffer_alloc_align16(
      cipher_size + CIPHER_SLACK_SIZE,
      get_total_headers2(session, record_params));
    if (bufel == NULL)
      return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

    headers = _mbuffer_get_uhead_ptr(bufel);
    if (vers->tls13_sem &&
        record_params->cipher->id != GNUTLS_CIPHER_NULL)
      headers[0] = GNUTLS_APPLICATION_DATA;
    else
      headers[0] = type;

    /* Use the default record version, if it is
     * set. */
    ret = copy_record_version(session, htype, &headers[1]);
    if (ret < 0)
      return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

    /* Adjust header length and add sequence for DTLS */
    if (IS_DTLS(session))
      _gnutls_write_uint64(record_state->sequence_number,
               &headers[3]);

    _gnutls_record_log(
      "REC[%p]: Preparing Packet %s(%d) with length: %d and min pad: %d\n",
      session, _gnutls_packet2str(type), type, (int)data_size,
      (int)min_pad);

    header_size = RECORD_HEADER_SIZE(session);
    _mbuffer_set_udata_size(bufel, cipher_size);
    _mbuffer_set_uhead_size(bufel, header_size);

    ret = _gnutls_encrypt(session, data, send_data_size, min_pad,
              bufel, type, record_params);
    if (ret <= 0) {
      gnutls_assert();
      if (ret == 0)
        ret = GNUTLS_E_ENCRYPTION_FAILED;
      gnutls_free(bufel);
      return ret; /* error */
    }

    cipher_size = _mbuffer_get_udata_size(bufel);
    retval = send_data_size;
    session->internals.record_send_buffer_user_size =
      send_data_size;

    /* increase sequence number
     */
    if (sequence_increment(session,
               &record_state->sequence_number) != 0) {
      session_invalidate(session);
      gnutls_free(bufel);
      return gnutls_assert_val(GNUTLS_E_RECORD_LIMIT_REACHED);
    }

    ret = _gnutls_io_write_buffered(session, bufel, mflags);
  }

  if (ret != cipher_size) {
    /* If we have sent any data then just return
     * the error value. Do not invalidate the session.
     */
    if (ret < 0 && gnutls_error_is_fatal(ret) == 0)
      return gnutls_assert_val(ret);

    if (ret > 0)
      ret = gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

    session_unresumable(session);
    session->internals.may_not_write = 1;
    return gnutls_assert_val(ret);
  }

  session->internals.record_send_buffer_user_size = 0;

  _gnutls_record_log(
    "REC[%p]: Sent Packet[%ld] %s(%d) in epoch %d and length: %d\n",
    session, (unsigned long)(record_state->sequence_number),
    _gnutls_packet2str(type), type, (int)record_params->epoch,
    (int)cipher_size);

  if (vers->tls13_sem &&
      !(session->internals.flags & GNUTLS_NO_AUTO_REKEY) &&
      !(record_params->cipher->flags & GNUTLS_CIPHER_FLAG_NO_REKEY)) {
    if (unlikely((record_state->sequence_number &
            UINT64_C(0xffffff)) == UINT64_C(0xfffffd))) {
      /* After we have sent 2^24 messages, mark the session
       * as needing a key update. */
      session->internals.rsend_state =
        RECORD_SEND_KEY_UPDATE_1;
    }
  }

  return retval;
}

inline static int check_recv_type(gnutls_session_t session,
          content_type_t recv_type)
{
  switch (recv_type) {
  case GNUTLS_CHANGE_CIPHER_SPEC:
  case GNUTLS_ALERT:
  case GNUTLS_HANDSHAKE:
  case GNUTLS_HEARTBEAT:
  case GNUTLS_APPLICATION_DATA:
    return 0;
  default:
    gnutls_assert();
    _gnutls_audit_log(session,
          "Received record packet of unknown type %u\n",
          (unsigned int)recv_type);
    return GNUTLS_E_UNEXPECTED_PACKET;
  }
}

/* Checks if there are pending data in the record buffers. If there are
 * then it copies the data.
 */
static int get_data_from_buffers(gnutls_session_t session, content_type_t type,
         uint8_t *data, int data_size, void *seq)
{
  if ((type == GNUTLS_APPLICATION_DATA || type == GNUTLS_HANDSHAKE ||
       type == GNUTLS_CHANGE_CIPHER_SPEC) &&
      _gnutls_record_buffer_get_size(session) > 0) {
    int ret;
    ret = _gnutls_record_buffer_get(type, session, data, data_size,
            seq);
    if (ret < 0) {
      if (IS_DTLS(session)) {
        if (ret == GNUTLS_E_UNEXPECTED_PACKET) {
          ret = GNUTLS_E_AGAIN;
        }
      }
      gnutls_assert();
      return ret;
    }

    return ret;
  }

  return 0;
}

/* Checks and retrieves any pending data in the application data record buffers.
 */
static int get_packet_from_buffers(gnutls_session_t session,
           content_type_t type, gnutls_packet_t *packet)
{
  if (_gnutls_record_buffer_get_size(session) > 0) {
    int ret;
    ret = _gnutls_record_buffer_get_packet(type, session, packet);
    if (ret < 0) {
      if (IS_DTLS(session)) {
        if (ret == GNUTLS_E_UNEXPECTED_PACKET) {
          ret = GNUTLS_E_AGAIN;
        }
      }
      gnutls_assert();
      return ret;
    }

    return ret;
  }

  *packet = NULL;
  return 0;
}

/* Here we check if the advertised version is the one we
 * negotiated in the handshake.
 */
inline static int record_check_version(gnutls_session_t session,
               gnutls_handshake_description_t htype,
               uint8_t version[2])
{
  const version_entry_st *vers = get_version(session);
  int diff = 0;

  if (vers->tls13_sem) {
    /* TLS 1.3 requires version to be 0x0303 */
    if (version[0] != 0x03 || version[1] != 0x03)
      diff = 1;
  } else {
    if (vers->major != version[0] || vers->minor != version[1])
      diff = 1;
  }

  if (!IS_DTLS(session)) {
    if (htype == GNUTLS_HANDSHAKE_CLIENT_HELLO ||
        htype == GNUTLS_HANDSHAKE_HELLO_RETRY_REQUEST ||
        htype == GNUTLS_HANDSHAKE_SERVER_HELLO) {
      if (version[0] != 3) {
        gnutls_assert();
        _gnutls_record_log(
          "REC[%p]: INVALID VERSION PACKET: (%d) %d.%d\n",
          session, htype, version[0], version[1]);
        return GNUTLS_E_UNSUPPORTED_VERSION_PACKET;
      }
    } else if (diff != 0) {
      /* Reject record packets that have a different version than the
       * one negotiated. Note that this version is not protected by any
       * mac. I don't really think that this check serves any purpose.
       */
      gnutls_assert();
      _gnutls_record_log(
        "REC[%p]: INVALID VERSION PACKET: (%d) %d.%d\n",
        session, htype, version[0], version[1]);

      return GNUTLS_E_UNSUPPORTED_VERSION_PACKET;
    }
  } else { /* DTLS */

    /* In DTLS the only information we have here is whether we
     * expect a handshake message or not.
     */
    if (htype == (gnutls_handshake_description_t)-1) {
      if (diff) {
        /* Reject record packets that have a different version than the
         * one negotiated. Note that this version is not protected by any
         * mac. I don't really think that this check serves any purpose.
         */
        gnutls_assert();
        _gnutls_record_log(
          "REC[%p]: INVALID VERSION PACKET: (%d) %d.%d\n",
          session, htype, version[0], version[1]);

        return GNUTLS_E_UNSUPPORTED_VERSION_PACKET;
      }
    } else if (vers->id > GNUTLS_DTLS1_0 && version[0] > 254) {
      gnutls_assert();
      _gnutls_record_log(
        "REC[%p]: INVALID DTLS VERSION PACKET: (%d) %d.%d\n",
        session, htype, version[0], version[1]);
      return GNUTLS_E_UNSUPPORTED_VERSION_PACKET;
    } else if (vers->id == GNUTLS_DTLS0_9 && version[0] > 1) {
      gnutls_assert();
      _gnutls_record_log(
        "REC[%p]: INVALID DTLS VERSION PACKET: (%d) %d.%d\n",
        session, htype, version[0], version[1]);
      return GNUTLS_E_UNSUPPORTED_VERSION_PACKET;
    }
  }

  return 0;
}

static int recv_hello_request(gnutls_session_t session, void *data,
            uint32_t data_size)
{
  uint8_t type;

  if (session->security_parameters.entity == GNUTLS_SERVER)
    return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);

  if (data_size < 1)
    return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);

  if (session->internals.handshake_in_progress)
    return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);

  type = ((uint8_t *)data)[0];
  if (type == GNUTLS_HANDSHAKE_HELLO_REQUEST) {
    if (IS_DTLS(session))
      session->internals.dtls.hsk_read_seq++;
    if (session->internals.flags & GNUTLS_AUTO_REAUTH) {
      session->internals.recv_state = RECV_STATE_REHANDSHAKE;
      return GNUTLS_E_AGAIN;
    } else {
      return GNUTLS_E_REHANDSHAKE;
    }
  } else {
    gnutls_assert();
    return GNUTLS_E_UNEXPECTED_PACKET;
  }
}

/* This function will check if the received record type is
 * the one we actually expect and adds it to the proper
 * buffer. The bufel will be deinitialized after calling
 * this function, even if it fails.
 */
static int record_add_to_buffers(gnutls_session_t session,
         struct tls_record_st *recv,
         content_type_t type,
         gnutls_handshake_description_t htype,
         uint64_t seq, mbuffer_st *bufel)
{
  int ret;
  const version_entry_st *ver = get_version(session);

  if ((recv->type == type) &&
      (type == GNUTLS_APPLICATION_DATA ||
       type == GNUTLS_CHANGE_CIPHER_SPEC || type == GNUTLS_HANDSHAKE)) {
    if (bufel->msg.size == 0) {
      if (type == GNUTLS_APPLICATION_DATA) {
        /* this is needed to distinguish an empty
         * message and EOF */
        ret = GNUTLS_E_AGAIN;
        goto cleanup;
      } else {
        ret = gnutls_assert_val(
          GNUTLS_E_UNEXPECTED_PACKET);
        goto unexpected_packet;
      }
    }

    /* application data cannot be inserted between (async) handshake
     * messages */
    if (type == GNUTLS_APPLICATION_DATA &&
        (session->internals.handshake_recv_buffer_size != 0 ||
         session->internals.handshake_header_recv_buffer.length !=
           0)) {
      ret = gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);
      goto unexpected_packet;
    }

    /* if the CCS has value other than 1 abort the connection,
     * unless old DTLS is negotiated, where CCS includes a sequence
     * number */
    if (type == GNUTLS_CHANGE_CIPHER_SPEC &&
        !(ver && ver->id == GNUTLS_DTLS0_9) &&
        (bufel->msg.size != 1 || bufel->msg.data[0] != 1)) {
      ret = gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);
      goto unexpected_packet;
    }

    _gnutls_record_buffer_put(session, type, seq, bufel);

    /* if we received application data as expected then we
     * deactivate the async timer */
    _dtls_async_timer_delete(session);
  } else {
    /* if the expected type is different than the received
     */
    switch (recv->type) {
    case GNUTLS_ALERT:
      if (bufel->msg.size < 2) {
        ret = gnutls_assert_val(
          GNUTLS_E_UNEXPECTED_PACKET);
        goto unexpected_packet;
      }

      _gnutls_record_log(
        "REC[%p]: Alert[%d|%d] - %s - was received\n",
        session, bufel->msg.data[0], bufel->msg.data[1],
        gnutls_alert_get_name((int)bufel->msg.data[1]));

      if (!session->internals.initial_negotiation_completed &&
          session->internals.handshake_in_progress &&
          STATE == STATE0) { /* handshake hasn't started */
        ret = gnutls_assert_val(
          GNUTLS_E_UNEXPECTED_PACKET);
        goto unexpected_packet;
      }

      session->internals.last_alert = bufel->msg.data[1];

      /* if close notify is received and
       * the alert is not fatal
       */
      if (bufel->msg.data[1] == GNUTLS_A_CLOSE_NOTIFY &&
          bufel->msg.data[0] != GNUTLS_AL_FATAL) {
        /* If we have been expecting for an alert do
         */
        session->internals.read_eof = 1;
        ret = GNUTLS_E_SESSION_EOF;
        goto cleanup;
      } else {
        /* if the alert is FATAL or WARNING
         * return the appropriate message
         */
        gnutls_assert();
        ret = GNUTLS_E_WARNING_ALERT_RECEIVED;
        if ((ver && ver->tls13_sem) ||
            bufel->msg.data[0] == GNUTLS_AL_FATAL) {
          session_unresumable(session);
          session_invalidate(session);
          ret = gnutls_assert_val(
            GNUTLS_E_FATAL_ALERT_RECEIVED);
        }
        goto cleanup;
      }
      break;

    case GNUTLS_CHANGE_CIPHER_SPEC:
      if (!(IS_DTLS(session))) {
        ret = gnutls_assert_val(
          GNUTLS_E_UNEXPECTED_PACKET);
        goto cleanup;
      }

      /* if the CCS has value other than 1 abort the
       * connection, unless old DTLS is negotiated, where CCS
       * includes a sequence number */
      if (!(ver && ver->id == GNUTLS_DTLS0_9) &&
          (bufel->msg.size != 1 || bufel->msg.data[0] != 1)) {
        ret = gnutls_assert_val(
          GNUTLS_E_UNEXPECTED_PACKET);
        goto unexpected_packet;
      }

      _gnutls_record_buffer_put(session, recv->type, seq,
              bufel);

      break;

#ifdef ENABLE_HEARTBEAT
    case GNUTLS_HEARTBEAT:
      ret = _gnutls_heartbeat_handle(session, bufel);
      goto cleanup;
#endif

    case GNUTLS_APPLICATION_DATA:
      if (session->internals.initial_negotiation_completed ==
          0) {
        ret = gnutls_assert_val(
          GNUTLS_E_UNEXPECTED_PACKET);
        goto unexpected_packet;
      }

      /* In TLS1.3 post-handshake authentication allow application
       * data error code. */
      if ((ver && ver->tls13_sem) &&
          type == GNUTLS_HANDSHAKE &&
          htype == GNUTLS_HANDSHAKE_CERTIFICATE_PKT &&
          session->internals.initial_negotiation_completed) {
        _gnutls_record_buffer_put(session, recv->type,
                seq, bufel);
        return gnutls_assert_val(
          GNUTLS_E_GOT_APPLICATION_DATA);
      }

      /* The got_application data is only returned
       * if expecting client hello (for rehandshake
       * reasons). Otherwise it is an unexpected packet
       */
      if (type == GNUTLS_ALERT ||
          ((htype == GNUTLS_HANDSHAKE_SERVER_HELLO ||
            htype == GNUTLS_HANDSHAKE_CLIENT_HELLO ||
            htype == GNUTLS_HANDSHAKE_HELLO_RETRY_REQUEST) &&
           type == GNUTLS_HANDSHAKE)) {
        /* even if data is unexpected put it into the buffer */
        _gnutls_record_buffer_put(session, recv->type,
                seq, bufel);
        return gnutls_assert_val(
          GNUTLS_E_GOT_APPLICATION_DATA);
      } else {
        ret = gnutls_assert_val(
          GNUTLS_E_UNEXPECTED_PACKET);
        goto unexpected_packet;
      }

      break;

    case GNUTLS_HANDSHAKE:
      /* In DTLS we might receive a handshake replay from the peer to indicate
       * the our last TLS handshake messages were not received.
       */
      if (IS_DTLS(session)) {
        if (type == GNUTLS_CHANGE_CIPHER_SPEC) {
          ret = gnutls_assert_val(
            GNUTLS_E_UNEXPECTED_PACKET);
          goto unexpected_packet;
        }

        if (_dtls_is_async(session) &&
            _dtls_async_timer_active(session)) {
          if (session->security_parameters.entity ==
                GNUTLS_SERVER &&
              bufel->htype ==
                GNUTLS_HANDSHAKE_CLIENT_HELLO) {
            /* client requested rehandshake. Delete the timer */
            _dtls_async_timer_delete(
              session);
          } else {
            session->internals.recv_state =
              RECV_STATE_DTLS_RETRANSMIT;
            ret = _dtls_retransmit(session);
            if (ret == 0) {
              session->internals
                .recv_state =
                RECV_STATE_0;
              ret = gnutls_assert_val(
                GNUTLS_E_AGAIN);
              goto unexpected_packet;
            }
            goto cleanup;
          }
        }
      }

      /* retrieve async handshake messages */
      if (ver && ver->tls13_sem) {
        _gnutls_record_buffer_put(session, recv->type,
                seq, bufel);

        ret = _gnutls13_recv_async_handshake(session);
        if (ret < 0)
          return gnutls_assert_val(ret);

        /* bufel is now accounted */
        return GNUTLS_E_AGAIN;
      }

      /* This is legal if HELLO_REQUEST is received - and we are a client.
       * If we are a server, a client may initiate a renegotiation at any time.
       */
      if (session->security_parameters.entity ==
            GNUTLS_SERVER &&
          session->internals.handshake_in_progress == 0 &&
          bufel->htype == GNUTLS_HANDSHAKE_CLIENT_HELLO) {
        gnutls_assert();
        _gnutls_record_buffer_put(session, recv->type,
                seq, bufel);
        return GNUTLS_E_REHANDSHAKE;
      }

      /* If we are already in a handshake then a Hello
       * Request is illegal. But here we don't really care
       * since this message will never make it up here.
       */

      /* So we accept it, if it is a Hello. If not, this will
       * fail and trigger flight retransmissions after some time. */
      ret = recv_hello_request(session, bufel->msg.data,
             bufel->msg.size);
      goto unexpected_packet;
    default:

      _gnutls_record_log(
        "REC[%p]: Received unexpected packet %d (%s) expecting %d (%s)\n",
        session, recv->type,
        _gnutls_packet2str(recv->type), type,
        _gnutls_packet2str(type));

      gnutls_assert();
      ret = GNUTLS_E_UNEXPECTED_PACKET;
      goto unexpected_packet;
    }
  }

  return 0;

unexpected_packet:

  if (IS_DTLS(session) && ret != GNUTLS_E_REHANDSHAKE) {
    _mbuffer_xfree(&bufel);
    RETURN_DTLS_EAGAIN_OR_TIMEOUT(session, ret);
  }

cleanup:
  _mbuffer_xfree(&bufel);
  return ret;
}

/* Checks the record headers and returns the length, version and
 * content type.
 */
static void record_read_headers(gnutls_session_t session,
        uint8_t headers[MAX_RECORD_HEADER_SIZE],
        content_type_t type,
        gnutls_handshake_description_t htype,
        struct tls_record_st *record)
{
  /* Read the first two bytes to determine if this is a
   * version 2 message
   */

#ifdef ENABLE_SSL2
  if (htype == GNUTLS_HANDSHAKE_CLIENT_HELLO &&
      type == GNUTLS_HANDSHAKE && headers[0] > 127 &&
      !(IS_DTLS(session))) {
    /* if msb set and expecting handshake message
     * it should be SSL 2 hello
     */
    record->version[0] = 3; /* assume SSL 3.0 */
    record->version[1] = 0;

    record->length = (((headers[0] & 0x7f) << 8)) | headers[1];

    /* SSL 2.0 headers */
    record->header_size = record->packet_size = 2;
    record->type =
      GNUTLS_HANDSHAKE; /* we accept only v2 client hello
               */

    /* in order to assist the handshake protocol.
     * V2 compatibility is a mess.
     */
    record->v2 = 1;
    record->epoch = 0;
    memset(&record->sequence, 0, sizeof(record->sequence));

    _gnutls_record_log(
      "REC[%p]: SSL 2.0 %s packet received. Length: %d\n",
      session, _gnutls_packet2str(record->type),
      record->length);

  } else
#endif
  {
    /* dtls version 1.0 and TLS version 1.x */
#ifdef ENABLE_SSL2
    record->v2 = 0;
#endif

    record->type = headers[0];
    record->version[0] = headers[1];
    record->version[1] = headers[2];

    if (IS_DTLS(session)) {
      record->sequence = _gnutls_read_uint64(&headers[3]);
      record->length = _gnutls_read_uint16(&headers[11]);
      record->epoch = record->sequence >> 48;
    } else {
      memset(&record->sequence, 0, sizeof(record->sequence));
      record->length = _gnutls_read_uint16(&headers[3]);
      record->epoch = session->security_parameters.epoch_read;
    }

    _gnutls_record_log(
      "REC[%p]: SSL %d.%d %s packet received. Epoch %d, length: %d\n",
      session, (int)record->version[0],
      (int)record->version[1],
      _gnutls_packet2str(record->type), (int)record->epoch,
      record->length);
  }

  record->packet_size += record->length;
}

static int recv_headers(gnutls_session_t session,
      record_parameters_st *record_params,
      content_type_t type,
      gnutls_handshake_description_t htype,
      struct tls_record_st *record, unsigned int *ms)
{
  int ret;
  gnutls_datum_t raw; /* raw headers */
  /* Read the headers.
   */
  record->header_size = record->packet_size = RECORD_HEADER_SIZE(session);

  ret = _gnutls_io_read_buffered(session, record->header_size, -1, ms);
  if (ret != record->header_size) {
    if (ret < 0 && gnutls_error_is_fatal(ret) == 0)
      return ret;

    if (ret > 0)
      ret = GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
    else if (ret == 0)
      ret = GNUTLS_E_PREMATURE_TERMINATION;

    return gnutls_assert_val(ret);
  }

  ret = _mbuffer_linearize_align16(&session->internals.record_recv_buffer,
           get_total_headers2(session,
                  record_params));
  if (ret < 0)
    return gnutls_assert_val(ret);

  _mbuffer_head_get_first(&session->internals.record_recv_buffer, &raw);
  if (raw.size < RECORD_HEADER_SIZE(session))
    return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);

  record_read_headers(session, raw.data, type, htype, record);

  /* Check if the DTLS epoch is valid */
  if (IS_DTLS(session)) {
    if (_gnutls_epoch_is_valid(session, record->epoch) == 0) {
      _gnutls_audit_log(
        session,
        "Discarded message[%lu] with invalid epoch %u.\n",
        (unsigned long)record->sequence,
        (unsigned int)(record->sequence >> 48));
      gnutls_assert();
      /* doesn't matter, just a fatal error */
      return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
    }
  }

  /* Here we check if the Type of the received packet is
   * ok.
   */
  if ((ret = check_recv_type(session, record->type)) < 0)
    return gnutls_assert_val(ret);

  /* Here we check if the advertised version is the one we
   * negotiated in the handshake.
   */
  if ((ret = record_check_version(session, htype, record->version)) < 0)
    return gnutls_assert_val(ret);

  if (record->length == 0 ||
      record->length > max_record_recv_size(session)) {
    _gnutls_audit_log(
      session,
      "Received packet with illegal length: %u (max: %u)\n",
      (unsigned int)record->length,
      (unsigned)max_record_recv_size(session));

    if (record->length == 0) {
      /* Empty, unencrypted records are always unexpected. */
      if (record_params->cipher->id == GNUTLS_CIPHER_NULL)
        return gnutls_assert_val(
          GNUTLS_E_UNEXPECTED_PACKET);

      return gnutls_assert_val(GNUTLS_E_DECRYPTION_FAILED);
    }
    return gnutls_assert_val(GNUTLS_E_RECORD_OVERFLOW);
  }

  _gnutls_record_log("REC[%p]: Expected Packet %s(%d)\n", session,
         _gnutls_packet2str(type), type);
  _gnutls_record_log("REC[%p]: Received Packet %s(%d) with length: %d\n",
         session, _gnutls_packet2str(record->type),
         record->type, record->length);

  return 0;
}

/* @ms: is the number of milliseconds to wait for data. Use zero for indefinite.
 *
 * This will receive record layer packets and add them to
 * application_data_buffer and handshake_data_buffer.
 *
 * If the htype is not -1 then handshake timeouts
 * will be enforced.
 */
ssize_t _gnutls_recv_in_buffers(gnutls_session_t session, content_type_t type,
        gnutls_handshake_description_t htype,
        unsigned int ms)
{
  uint64_t packet_sequence;
  gnutls_datum_t ciphertext;
  mbuffer_st *bufel = NULL, *decrypted = NULL;
  gnutls_datum_t t;
  int ret;
  unsigned int n_retries = 0;
  record_parameters_st *record_params;
  record_state_st *record_state;
  struct tls_record_st record;
  const version_entry_st *vers = get_version(session);

begin:

  if (n_retries > DEFAULT_MAX_EMPTY_RECORDS) {
    gnutls_assert();
    return GNUTLS_E_TOO_MANY_EMPTY_PACKETS;
  }

  if (session->internals.read_eof != 0) {
    /* if we have already read an EOF
     */
    return 0;
  } else if (session_is_valid(session) != 0 ||
       session->internals.may_not_read != 0)
    return gnutls_assert_val(GNUTLS_E_INVALID_SESSION);

  /* get the record state parameters */
  ret = _gnutls_epoch_get(session, EPOCH_READ_CURRENT, &record_params);
  if (ret < 0)
    return gnutls_assert_val(ret);

  /* Safeguard against processing data with an incomplete cipher state. */
  if (!record_params->initialized)
    return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

  record_state = &record_params->read;

  /* receive headers */
  ret = recv_headers(
    session, record_params, type, htype, &record,
    (!(session->internals.flags & GNUTLS_NONBLOCK)) ? &ms : 0);
  if (ret < 0) {
    ret = gnutls_assert_val_fatal(ret);
    goto recv_error;
  }

  if (IS_DTLS(session))
    packet_sequence = record.sequence;
  else
    packet_sequence = record_state->sequence_number;

  /* Read the packet data and insert it to record_recv_buffer.
   */
  ret = _gnutls_io_read_buffered(
    session, record.packet_size, record.type,
    (!(session->internals.flags & GNUTLS_NONBLOCK)) ? &ms : 0);
  if (ret != record.packet_size) {
    gnutls_assert();
    goto recv_error;
  }

  /* ok now we are sure that we have read all the data - so
   * move on !
   */
  ret = _mbuffer_linearize_align16(&session->internals.record_recv_buffer,
           get_total_headers2(session,
                  record_params));
  if (ret < 0)
    return gnutls_assert_val(ret);

  bufel = _mbuffer_head_get_first(&session->internals.record_recv_buffer,
          NULL);
  if (bufel == NULL)
    return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

  /* ignore CCS if TLS 1.3 is negotiated */
  if (record.type == GNUTLS_CHANGE_CIPHER_SPEC && vers &&
      vers->tls13_sem) {
    /* if the CCS has arrived after Finished, abort the
     * connection */
    if (!session->internals.handshake_in_progress) {
      return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);
    }
    _gnutls_read_log("discarding change cipher spec in TLS1.3\n");
    /* we use the same mechanism to retry as when
     * receiving multiple empty TLS packets */
    bufel = _mbuffer_head_pop_first(
      &session->internals.record_recv_buffer);
    _mbuffer_xfree(&bufel);
    n_retries++;
    goto begin;
  }

  /* We allocate the maximum possible to allow few compressed bytes to expand to a
   * full record. Moreover we add space for any pad and the MAC (in case
   * they are encrypted).
   */
  ret = max_decrypted_size(session) + MAX_PAD_SIZE + MAX_HASH_SIZE;
  decrypted = _mbuffer_alloc_align16(ret, 0);
  if (decrypted == NULL)
    return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

  _mbuffer_set_udata_size(decrypted, ret);
  ciphertext.data =
    (uint8_t *)_mbuffer_get_udata_ptr(bufel) + record.header_size;
  ciphertext.size = record.length;

  /* decrypt the data we got.
   */
  t.data = _mbuffer_get_udata_ptr(decrypted);
  t.size = _mbuffer_get_udata_size(decrypted);
  ret = _gnutls_decrypt(session, &ciphertext, &t, &record.type,
            record_params, packet_sequence);
  if (ret >= 0)
    _mbuffer_set_udata_size(decrypted, ret);

  _mbuffer_head_remove_bytes(&session->internals.record_recv_buffer,
           record.header_size + record.length);

  if (session->security_parameters.entity == GNUTLS_SERVER &&
      session->internals.hsk_flags & HSK_EARLY_DATA_IN_FLIGHT) {
    if (session->internals.hsk_flags & HSK_EARLY_DATA_ACCEPTED) {
      if (ret < 0 ||
          /* early data must always be encrypted, treat it
           * as decryption failure if otherwise */
          record_params->cipher->id == GNUTLS_CIPHER_NULL) {
        _gnutls_record_log(
          "REC[%p]: failed to decrypt early data, in epoch %d\n",
          session, record_params->epoch);
        ret = GNUTLS_E_DECRYPTION_FAILED;
        goto sanity_check_error;
      } else if (record.type == GNUTLS_APPLICATION_DATA) {
        size_t decrypted_length =
          _mbuffer_get_udata_size(decrypted);
        _gnutls_record_log(
          "REC[%p]: decrypted early data with length: %d, in epoch %d\n",
          session, (int)decrypted_length,
          record_params->epoch);
        if (decrypted_length >
            session->security_parameters
                .max_early_data_size -
              session->internals
                .early_data_received) {
          _gnutls_record_log(
            "REC[%p]: max_early_data_size exceeded\n",
            session);
          ret = GNUTLS_E_UNEXPECTED_PACKET;
          goto sanity_check_error;
        }

        _mbuffer_enqueue(
          &session->internals
             .early_data_recv_buffer,
          decrypted);
        session->internals.early_data_received +=
          decrypted_length;

        /* Increase sequence number. We do both for TLS and DTLS, since in
         * DTLS we also rely on that number (roughly) since it may get reported
         * to application via gnutls_record_get_state().
         */
        if (sequence_increment(
              session,
              &record_state->sequence_number) !=
            0) {
          session_invalidate(session);
          gnutls_assert();
          ret = GNUTLS_E_RECORD_LIMIT_REACHED;
          goto sanity_check_error;
        }

        /* decrypted is now accounted */
        return GNUTLS_E_AGAIN;
      }
    } else {
      /* We do not accept early data: skip decryption
       * failure up to max_early_data_size. Otherwise,
       * if the record is properly decrypted, treat it as
       * the start of client's second flight.
       */
      if (record.type == GNUTLS_APPLICATION_DATA &&
          (ret < 0 ||
           /* early data must always be encrypted, treat it
            * as decryption failure if otherwise */
           record_params->cipher->id == GNUTLS_CIPHER_NULL)) {
        if (record.length >
            session->security_parameters
                .max_early_data_size -
              session->internals
                .early_data_received) {
          _gnutls_record_log(
            "REC[%p]: max_early_data_size exceeded\n",
            session);
          ret = GNUTLS_E_UNEXPECTED_PACKET;
          goto sanity_check_error;
        }

        _gnutls_record_log(
          "REC[%p]: Discarded early data[%lu] due to invalid decryption, length: %u\n",
          session, (unsigned long)packet_sequence,
          (unsigned int)record.length);
        session->internals.early_data_received +=
          record.length;
        /* silently discard received data */
        _mbuffer_xfree(&decrypted);
        return gnutls_assert_val(GNUTLS_E_AGAIN);
      } else {
        session->internals.hsk_flags &=
          ~HSK_EARLY_DATA_IN_FLIGHT;
      }
    }
  }

  if (ret < 0) {
    gnutls_assert();
    _gnutls_audit_log(
      session,
      "Discarded message[%lu] due to invalid decryption\n",
      (unsigned long)packet_sequence);
    goto sanity_check_error;
  }

  if (IS_DTLS(session)) {
    /* check for duplicates. We check after the message
     * is processed and authenticated to avoid someone
     * messing with our windows. */
    if (likely(!(session->internals.flags &
           GNUTLS_NO_REPLAY_PROTECTION))) {
      ret = _dtls_record_check(record_params,
             packet_sequence);
      if (ret < 0) {
        _gnutls_record_log(
          "REC[%p]: Discarded duplicate message[%u.%lu]: %s\n",
          session,
          (unsigned int)(record.sequence >> 48),
          (unsigned long)(packet_sequence),
          _gnutls_packet2str(record.type));
        goto sanity_check_error;
      }
    }

    _gnutls_record_log(
      "REC[%p]: Decrypted Packet[%u.%lu] %s(%d) with length: %d\n",
      session, (unsigned int)(record.sequence >> 48),
      (unsigned long)packet_sequence,
      _gnutls_packet2str(record.type), record.type,
      (int)_mbuffer_get_udata_size(decrypted));

    /* store the last valid sequence number. We don't use that internally but
     * callers of gnutls_record_get_state() could take advantage of it. */
    record_state->sequence_number = record.sequence;
  } else {
    _gnutls_record_log(
      "REC[%p]: Decrypted Packet[%lu] %s(%d) with length: %d\n",
      session, (unsigned long)packet_sequence,
      _gnutls_packet2str(record.type), record.type,
      (int)_mbuffer_get_udata_size(decrypted));
  }

  /* Increase sequence number. We do both for TLS and DTLS, since in
   * DTLS we also rely on that number (roughly) since it may get reported
   * to application via gnutls_record_get_state().
   */
  if (sequence_increment(session, &record_state->sequence_number) != 0) {
    session_invalidate(session);
    gnutls_assert();
    ret = GNUTLS_E_RECORD_LIMIT_REACHED;
    goto sanity_check_error;
  }

  /* (originally for) TLS 1.0 CBC protection.
   * Actually this code is called if we just received
   * an empty packet. An empty TLS packet is usually
   * sent to protect some vulnerabilities in the CBC mode.
   * In that case we go to the beginning and start reading
   * the next packet.
   */
  if (_mbuffer_get_udata_size(decrypted) == 0 &&
      /* Under TLS 1.3, there are only AEAD ciphers and this
       * logic is meaningless. Moreover, the implementation need
       * to send correct alert upon receiving empty messages in
       * certain occasions. Skip this and leave
       * record_add_to_buffers() to handle the empty
       * messages. */
      !(vers && vers->tls13_sem)) {
    _mbuffer_xfree(&decrypted);
    n_retries++;
    goto begin;
  }

  if (_mbuffer_get_udata_size(decrypted) > max_decrypted_size(session)) {
    _gnutls_audit_log(session,
          "Received packet with illegal length: %u\n",
          (unsigned int)ret);

    ret = gnutls_assert_val(GNUTLS_E_RECORD_OVERFLOW);
    goto sanity_check_error;
  }

#ifdef ENABLE_SSL2
  if (record.v2) {
    decrypted->htype = GNUTLS_HANDSHAKE_CLIENT_HELLO_V2;
  } else
#endif
  {
    uint8_t *p = _mbuffer_get_udata_ptr(decrypted);
    decrypted->htype = p[0];
  }

  ret = record_add_to_buffers(session, &record, type, htype,
            packet_sequence, decrypted);

  /* decrypted is now either deinitialized or buffered somewhere else */

  if (ret < 0)
    return gnutls_assert_val(ret);

  return ret;

discard:
  session->internals.dtls.packets_dropped++;

  /* discard the whole received fragment. */
  bufel = _mbuffer_head_pop_first(&session->internals.record_recv_buffer);
  _mbuffer_xfree(&bufel);
  return gnutls_assert_val(GNUTLS_E_AGAIN);

sanity_check_error:
  if (IS_DTLS(session)) {
    session->internals.dtls.packets_dropped++;
    ret = gnutls_assert_val(GNUTLS_E_AGAIN);
    goto cleanup;
  }

  session_unresumable(session);
  session_invalidate(session);

cleanup:
  _mbuffer_xfree(&decrypted);
  return ret;

recv_error:
  if (ret < 0 &&
      (gnutls_error_is_fatal(ret) == 0 || ret == GNUTLS_E_TIMEDOUT))
    return ret;

  if (type == GNUTLS_ALERT) { /* we were expecting close notify */
    session_invalidate(session);
    gnutls_assert();
    return 0;
  }

  if (IS_DTLS(session) && (ret == GNUTLS_E_DECRYPTION_FAILED ||
         ret == GNUTLS_E_UNSUPPORTED_VERSION_PACKET ||
         ret == GNUTLS_E_UNEXPECTED_PACKET_LENGTH ||
         ret == GNUTLS_E_RECORD_OVERFLOW ||
         ret == GNUTLS_E_UNEXPECTED_PACKET ||
         ret == GNUTLS_E_ERROR_IN_FINISHED_PACKET ||
         ret == GNUTLS_E_UNEXPECTED_HANDSHAKE_PACKET)) {
    goto discard;
  }

  session_invalidate(session);
  session_unresumable(session);

  if (ret == 0)
    return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
  else
    return ret;
}

/* Returns a value greater than zero (>= 0) if buffers should be checked
 * for data. */
static ssize_t check_session_status(gnutls_session_t session, unsigned ms)
{
  int ret;

  if (session->internals.read_eof != 0) {
    /* if we have already read an EOF
     */
    return 0;
  } else if (session_is_valid(session) != 0 ||
       session->internals.may_not_read != 0) {
    gnutls_assert();
    return GNUTLS_E_INVALID_SESSION;
  }

  switch (session->internals.recv_state) {
  case RECV_STATE_REAUTH:
    session->internals.recv_state = RECV_STATE_0;

    ret = gnutls_reauth(session, 0);
    if (ret < 0) {
      /* a temp or fatal error, make sure we reset the state
       * so we can resume on temp errors */
      session->internals.recv_state = RECV_STATE_REAUTH;
      return gnutls_assert_val(ret);
    }

    return 1;
  case RECV_STATE_REHANDSHAKE:
    session->internals.recv_state = RECV_STATE_0;

    ret = gnutls_handshake(session);
    if (ret < 0) {
      /* a temp or fatal error, make sure we reset the state
       * so we can resume on temp errors */
      session->internals.recv_state = RECV_STATE_REHANDSHAKE;
      return gnutls_assert_val(ret);
    }

    return 1;
  case RECV_STATE_ASYNC_HANDSHAKE:
    ret = _gnutls_recv_in_buffers(session, GNUTLS_HANDSHAKE, -1,
                ms);
    if (ret < 0 && ret != GNUTLS_E_SESSION_EOF)
      return gnutls_assert_val(ret);

    ret = _gnutls13_recv_async_handshake(session);
    if (ret < 0)
      return gnutls_assert_val(ret);

    return GNUTLS_E_AGAIN;
  case RECV_STATE_EARLY_START_HANDLING:
  case RECV_STATE_FALSE_START_HANDLING:
    return 1;
  case RECV_STATE_FALSE_START:
    /* if false start is not complete we always expect for handshake packets
     * prior to anything else. */
    if (session->security_parameters.entity != GNUTLS_CLIENT ||
        !(session->internals.flags & GNUTLS_ENABLE_FALSE_START))
      return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

    /* Attempt to complete handshake - we only need to receive */
    session->internals.recv_state = RECV_STATE_FALSE_START_HANDLING;
    ret = gnutls_handshake(session);
    if (ret < 0) {
      /* a temp or fatal error, make sure we reset the state
       * so we can resume on temp errors */
      session->internals.recv_state = RECV_STATE_FALSE_START;
      return gnutls_assert_val(ret);
    }

    session->internals.recv_state = RECV_STATE_0;
    return 1;
  case RECV_STATE_EARLY_START:
    /* if early start is not complete we always expect for handshake packets
     * prior to anything else. */
    if (session->security_parameters.entity != GNUTLS_SERVER ||
        !(session->internals.flags & GNUTLS_ENABLE_EARLY_START))
      return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

    /* Attempt to complete handshake - we only need to receive */
    session->internals.recv_state = RECV_STATE_EARLY_START_HANDLING;
    ret = gnutls_handshake(session);
    if (ret < 0) {
      /* a temp or fatal error, make sure we reset the state
       * so we can resume on temp errors */
      session->internals.recv_state = RECV_STATE_EARLY_START;
      return gnutls_assert_val(ret);
    }

    session->internals.recv_state = RECV_STATE_0;
    return 1;
  case RECV_STATE_DTLS_RETRANSMIT:
    ret = _dtls_retransmit(session);
    if (ret < 0)
      return gnutls_assert_val(ret);

    session->internals.recv_state = RECV_STATE_0;

    FALLTHROUGH;
  case RECV_STATE_0:

    _dtls_async_timer_check(session);
    return 1;
  default:
    return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
  }
}

/* This function behaves exactly like read(). The only difference is
 * that it accepts the gnutls_session_t and the content_type_t of data to
 * receive (if called by the user the Content is Userdata only)
 * It is intended to receive data, under the current session.
 */
ssize_t _gnutls_recv_int(gnutls_session_t session, content_type_t type,
       uint8_t *data, size_t data_size, void *seq,
       unsigned int ms)
{
  int ret;

  if ((type != GNUTLS_ALERT && type != GNUTLS_HEARTBEAT) &&
      (data_size == 0 || data == NULL))
    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  ret = check_session_status(session, ms);
  if (ret <= 0)
    return ret;

  /* If we have enough data in the cache do not bother receiving
   * a new packet. (in order to flush the cache)
   */
  ret = get_data_from_buffers(session, type, data, data_size, seq);
  if (ret != 0)
    return ret;

  ret = _gnutls_recv_in_buffers(session, type, -1, ms);
  if (ret < 0 && ret != GNUTLS_E_SESSION_EOF)
    return gnutls_assert_val(ret);

  return get_data_from_buffers(session, type, data, data_size, seq);
}

/**
 * gnutls_packet_get:
 * @packet: is a #gnutls_packet_t type.
 * @data: will contain the data present in the @packet structure (may be %NULL)
 * @sequence: the 8-bytes of the packet sequence number (may be %NULL)
 *
 * This function returns the data and sequence number associated with
 * the received packet.
 *
 * Since: 3.3.5
 **/

void gnutls_packet_get(gnutls_packet_t packet, gnutls_datum_t *data,
           unsigned char *sequence)
{
  if (unlikely(packet == NULL)) {
    gnutls_assert();
    if (data) {
      data->data = NULL;
      data->size = 0;
      return;
    }
  }

  assert(packet != NULL);

  if (sequence) {
    _gnutls_write_uint64(packet->record_sequence, sequence);
  }

  if (data) {
    data->size = packet->msg.size - packet->mark;
    data->data = packet->msg.data + packet->mark;
  }
}

/**
 * gnutls_packet_deinit:
 * @packet: is a pointer to a #gnutls_packet_st structure.
 *
 * This function will deinitialize all data associated with
 * the received packet.
 *
 * Since: 3.3.5
 **/
void gnutls_packet_deinit(gnutls_packet_t packet)
{
  gnutls_free(packet);
}

/**
 * gnutls_record_discard_queued:
 * @session: is a #gnutls_session_t type.
 *
 * This function discards all queued to be sent packets in a DTLS session.
 * These are the packets queued after an interrupted gnutls_record_send().
 *
 * This function can only be used with transports where send() is
 * an all-or-nothing operation (e.g., UDP). When partial writes are allowed
 * this function will cause session errors.
 *
 * Returns: The number of bytes discarded.
 *
 * Since: 3.4.0
 **/
size_t gnutls_record_discard_queued(gnutls_session_t session)
{
  size_t ret = session->internals.record_send_buffer.byte_length;
  _mbuffer_head_clear(&session->internals.record_send_buffer);
  return ret;
}

/**
 * gnutls_record_recv_packet:
 * @session: is a #gnutls_session_t type.
 * @packet: the structure that will hold the packet data
 *
 * This is a lower-level function than gnutls_record_recv() and allows
 * to directly receive the whole decrypted packet. That avoids a
 * memory copy, and is intended to be used by applications seeking high
 * performance.
 *
 * The received packet is accessed using gnutls_packet_get() and
 * must be deinitialized using gnutls_packet_deinit(). The returned
 * packet will be %NULL if the return value is zero (EOF).
 *
 * Returns: The number of bytes received and zero on EOF (for stream
 * connections).  A negative error code is returned in case of an error.
 *
 * Since: 3.3.5
 **/
ssize_t gnutls_record_recv_packet(gnutls_session_t session,
          gnutls_packet_t *packet)
{
  int ret;

  if (packet == NULL)
    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  ret = check_session_status(session,
           session->internals.record_timeout_ms);
  if (ret <= 0)
    return ret;

  ret = get_packet_from_buffers(session, GNUTLS_APPLICATION_DATA, packet);
  if (ret != 0)
    return ret;

  ret = _gnutls_recv_in_buffers(session, GNUTLS_APPLICATION_DATA, -1,
              session->internals.record_timeout_ms);
  if (ret < 0 && ret != GNUTLS_E_SESSION_EOF)
    return gnutls_assert_val(ret);

  return get_packet_from_buffers(session, GNUTLS_APPLICATION_DATA,
               packet);
}

static ssize_t append_data_to_corked(gnutls_session_t session, const void *data,
             size_t data_size)
{
  int ret;

  if (IS_DTLS(session)) {
    if (data_size +
          session->internals.record_presend_buffer.length >
        gnutls_dtls_get_data_mtu(session)) {
      return gnutls_assert_val(GNUTLS_E_LARGE_PACKET);
    }
  }

  ret = _gnutls_buffer_append_data(
    &session->internals.record_presend_buffer, data, data_size);
  if (ret < 0)
    return gnutls_assert_val(ret);

  return data_size;
}

/**
 * gnutls_record_send:
 * @session: is a #gnutls_session_t type.
 * @data: contains the data to send
 * @data_size: is the length of the data
 *
 * This function has the similar semantics with send().  The only
 * difference is that it accepts a GnuTLS session, and uses different
 * error codes.
 * Note that if the send buffer is full, send() will block this
 * function.  See the send() documentation for more information.
 *
 * You can replace the default push function which is send(), by using
 * gnutls_transport_set_push_function().
 *
 * If the EINTR is returned by the internal push function
 * then %GNUTLS_E_INTERRUPTED will be returned. If
 * %GNUTLS_E_INTERRUPTED or %GNUTLS_E_AGAIN is returned, you must
 * call this function again with the exact same parameters, or provide a
 * %NULL pointer for @data and 0 for @data_size, in order to write the
 * same data as before. If you wish to discard the previous data instead
 * of retrying, you must call gnutls_record_discard_queued() before
 * calling this function with different parameters. Note that the latter
 * works only on special transports (e.g., UDP).
 * cf. gnutls_record_get_direction().
 *
 * Note that in DTLS this function will return the %GNUTLS_E_LARGE_PACKET
 * error code if the send data exceed the data MTU value - as returned
 * by gnutls_dtls_get_data_mtu(). The errno value EMSGSIZE
 * also maps to %GNUTLS_E_LARGE_PACKET.
 * Note that since 3.2.13 this function can be called under cork in DTLS
 * mode, and will refuse to send data over the MTU size by returning
 * %GNUTLS_E_LARGE_PACKET.
 *
 * Returns: The number of bytes sent, or a negative error code.  The
 *   number of bytes sent might be less than @data_size.  The maximum
 *   number of bytes this function can send in a single call depends
 *   on the negotiated maximum record size.
 **/
ssize_t gnutls_record_send(gnutls_session_t session, const void *data,
         size_t data_size)
{
  return gnutls_record_send2(session, data, data_size, 0, 0);
}

/**
 * gnutls_record_send2:
 * @session: is a #gnutls_session_t type.
 * @data: contains the data to send
 * @data_size: is the length of the data
 * @pad: padding to be added to the record
 * @flags: must be zero
 *
 * This function is identical to gnutls_record_send() except that it
 * takes an extra argument to specify padding to be added the record.
 * To determine the maximum size of padding, use
 * gnutls_record_get_max_size() and gnutls_record_overhead_size().
 *
 * Note that in order for GnuTLS to provide constant time processing
 * of padding and data in TLS1.3, the flag %GNUTLS_SAFE_PADDING_CHECK
 * must be used in gnutls_init().
 *
 * Returns: The number of bytes sent, or a negative error code.  The
 *   number of bytes sent might be less than @data_size.  The maximum
 *   number of bytes this function can send in a single call depends
 *   on the negotiated maximum record size.
 *
 * Since: 3.6.3
 **/
ssize_t gnutls_record_send2(gnutls_session_t session, const void *data,
          size_t data_size, size_t pad, unsigned flags)
{
  const version_entry_st *vers = get_version(session);
  size_t max_pad = 0;
  int ret;

  if (unlikely(!session->internals.initial_negotiation_completed)) {
    /* this is to protect buggy applications from sending unencrypted
     * data. We allow sending however, if we are in false or early start
     * handshake state. */
    gnutls_mutex_lock(&session->internals.post_negotiation_lock);

    /* we intentionally re-check the initial_negotation_completed variable
     * to avoid locking during normal operation of gnutls_record_send2() */
    if (!session->internals.initial_negotiation_completed &&
        session->internals.recv_state != RECV_STATE_FALSE_START &&
        session->internals.recv_state !=
          RECV_STATE_FALSE_START_HANDLING &&
        session->internals.recv_state != RECV_STATE_EARLY_START &&
        session->internals.recv_state !=
          RECV_STATE_EARLY_START_HANDLING &&
        !(session->internals.hsk_flags &
          HSK_EARLY_DATA_IN_FLIGHT)) {
      gnutls_mutex_unlock(
        &session->internals.post_negotiation_lock);
      return gnutls_assert_val(
        GNUTLS_E_UNAVAILABLE_DURING_HANDSHAKE);
    }
    gnutls_mutex_unlock(&session->internals.post_negotiation_lock);
  }

  if (unlikely(!vers))
    return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

  if (vers->tls13_sem)
    max_pad = gnutls_record_get_max_size(session) -
        gnutls_record_overhead_size(session);

  if (pad > max_pad)
    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  switch (session->internals.rsend_state) {
  case RECORD_SEND_NORMAL:
    if (IS_KTLS_ENABLED(session, GNUTLS_KTLS_SEND)) {
      return _gnutls_ktls_send(session, data, data_size);
    } else {
      return _gnutls_send_tlen_int(session,
                 GNUTLS_APPLICATION_DATA,
                 -1, EPOCH_WRITE_CURRENT,
                 data, data_size, pad,
                 MBUFFER_FLUSH);
    }
  case RECORD_SEND_CORKED:
  case RECORD_SEND_CORKED_TO_KU:
    return append_data_to_corked(session, data, data_size);
  case RECORD_SEND_KEY_UPDATE_1:
    _gnutls_buffer_reset(
      &session->internals.record_key_update_buffer);

    ret = _gnutls_buffer_append_data(
      &session->internals.record_key_update_buffer, data,
      data_size);
    if (ret < 0)
      return gnutls_assert_val(ret);

    session->internals.rsend_state = RECORD_SEND_KEY_UPDATE_2;
    FALLTHROUGH;
  case RECORD_SEND_KEY_UPDATE_2:
    ret = gnutls_session_key_update(session, 0);
    if (ret < 0)
      return gnutls_assert_val(ret);

    session->internals.rsend_state = RECORD_SEND_KEY_UPDATE_3;
    FALLTHROUGH;
  case RECORD_SEND_KEY_UPDATE_3:
    if (IS_KTLS_ENABLED(session, GNUTLS_KTLS_SEND)) {
      return _gnutls_ktls_send(
        session,
        session->internals.record_key_update_buffer.data,
        session->internals.record_key_update_buffer
          .length);
    } else {
      ret = _gnutls_send_int(
        session, GNUTLS_APPLICATION_DATA, -1,
        EPOCH_WRITE_CURRENT,
        session->internals.record_key_update_buffer.data,
        session->internals.record_key_update_buffer
          .length,
        MBUFFER_FLUSH);
    }
    _gnutls_buffer_clear(
      &session->internals.record_key_update_buffer);
    session->internals.rsend_state = RECORD_SEND_NORMAL;
    if (ret < 0)
      gnutls_assert();

    return ret;
  default:
    return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
  }
}

/**
 * gnutls_record_send_early_data:
 * @session: is a #gnutls_session_t type.
 * @data: contains the data to send
 * @data_size: is the length of the data
 *
 * This function can be used by a client to send data early in the
 * handshake processes when resuming a session.  This is used to
 * implement a zero-roundtrip (0-RTT) mode.  It has the same semantics
 * as gnutls_record_send().
 *
 * There may be a limit to the amount of data sent as early data.  Use
 * gnutls_record_get_max_early_data_size() to check the limit.  If the
 * limit exceeds, this function returns
 * %GNUTLS_E_RECORD_LIMIT_REACHED.
 *
 * Returns: The number of bytes sent, or a negative error code.  The
 *   number of bytes sent might be less than @data_size.  The maximum
 *   number of bytes this function can send in a single call depends
 *   on the negotiated maximum record size.
 *
 * Since: 3.6.5
 **/
ssize_t gnutls_record_send_early_data(gnutls_session_t session,
              const void *data, size_t data_size)
{
  int ret;

  if (session->security_parameters.entity != GNUTLS_CLIENT)
    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  if (data_size == 0) {
    return 0;
  }

  if (xsum(session->internals.early_data_presend_buffer.length,
     data_size) > session->security_parameters.max_early_data_size)
    return gnutls_assert_val(GNUTLS_E_RECORD_LIMIT_REACHED);

  ret = _gnutls_buffer_append_data(
    &session->internals.early_data_presend_buffer, data, data_size);
  if (ret < 0)
    return gnutls_assert_val(ret);

  session->internals.flags |= GNUTLS_ENABLE_EARLY_DATA;

  return ret;
}

/**
 * gnutls_record_send_file:
 * @session: is a #gnutls_session_t type.
 * @fd: file descriptor from which to read data.
 * @offset: Is relative to file offset, denotes the starting location for
 *          reading.  after function returns, it point to position following
 *          last read byte.
 * @count: is the length of the data in bytes to be read from file and send.
 *
 * This function sends data from @fd. If KTLS (kernel TLS) is enabled, it will
 * use the sendfile() system call to avoid overhead of copying data between user
 * space and the kernel. Otherwise, this functionality is merely emulated by
 * calling read() and gnutls_record_send(). If this implementation is
 * suboptimal, check whether KTLS is enabled using
 * gnutls_transport_is_ktls_enabled().
 *
 * If @offset is NULL then file offset is incremented by number of bytes send,
 * otherwise file offset remains unchanged.
 *
 * Returns: The number of bytes sent, or a negative error code.
 **/
ssize_t gnutls_record_send_file(gnutls_session_t session, int fd, off_t *offset,
        size_t count)
{
  ssize_t ret;
  size_t buf_len;
  size_t sent = 0;
  uint8_t *buf;
  off_t saved_offset = 0;

  if (IS_KTLS_ENABLED(session, GNUTLS_KTLS_SEND)) {
    return _gnutls_ktls_send_file(session, fd, offset, count);
  }

  if (offset != NULL) {
    saved_offset = lseek(fd, 0, SEEK_CUR);
    if (saved_offset == (off_t)-1) {
      return GNUTLS_E_FILE_ERROR;
    }
    if (lseek(fd, *offset, SEEK_CUR) == -1) {
      return GNUTLS_E_FILE_ERROR;
    }
  }

  buf_len = MIN(count, MAX(max_record_send_size(session), 512));

  buf = gnutls_malloc(buf_len);
  if (buf == NULL) {
    gnutls_assert();
    ret = GNUTLS_E_MEMORY_ERROR;
    goto end;
  }

  while (sent < count) {
    ret = read(fd, buf, MIN(buf_len, count - sent));
    if (ret == 0) {
      break;
    } else if (ret == -1) {
      if (errno == EAGAIN) {
        ret = GNUTLS_E_AGAIN;
        goto end;
      }
      ret = GNUTLS_E_FILE_ERROR;
      goto end;
    }

    ret = gnutls_record_send(session, buf, ret);
    if (ret < 0) {
      goto end;
    }
    if (INT_ADD_OVERFLOW(sent, ret)) {
      gnutls_assert();
      ret = GNUTLS_E_RECORD_OVERFLOW;
      goto end;
    }
    sent += ret;
  }

  ret = sent;

end:
  if (offset != NULL) {
    if (likely(!INT_ADD_OVERFLOW(*offset, sent))) {
      *offset += sent;
    } else {
      gnutls_assert();
      ret = GNUTLS_E_RECORD_OVERFLOW;
    }
    lseek(fd, saved_offset, SEEK_SET);
  }
  gnutls_free(buf);
  return ret;
}

/**
 * gnutls_record_recv_early_data:
 * @session: is a #gnutls_session_t type.
 * @data: the buffer that the data will be read into
 * @data_size: the number of requested bytes
 *
 * This function can be used by a server to retrieve data sent early
 * in the handshake processes when resuming a session.  This is used
 * to implement a zero-roundtrip (0-RTT) mode.  It has the same
 * semantics as gnutls_record_recv().
 *
 * This function can be called either in a handshake hook, or after
 * the handshake is complete.
 *
 * Returns: The number of bytes received and zero when early data
 * reading is complete.  A negative error code is returned in case of
 * an error.  If no early data is received during the handshake, this
 * function returns %GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE.  The
 * number of bytes received might be less than the requested
 * @data_size.
 *
 * Since: 3.6.5
 **/
ssize_t gnutls_record_recv_early_data(gnutls_session_t session, void *data,
              size_t data_size)
{
  mbuffer_st *bufel;
  gnutls_datum_t msg;
  size_t length;

  if (session->security_parameters.entity != GNUTLS_SERVER)
    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  bufel = _mbuffer_head_get_first(
    &session->internals.early_data_recv_buffer, &msg);
  if (bufel == NULL)
    return gnutls_assert_val(GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE);

  length = MIN(msg.size, data_size);
  memcpy(data, msg.data, length);
  _mbuffer_head_remove_bytes(&session->internals.early_data_recv_buffer,
           length);

  return length;
}

/**
 * gnutls_record_cork:
 * @session: is a #gnutls_session_t type.
 *
 * If called, gnutls_record_send() will no longer send any records.
 * Any sent records will be cached until gnutls_record_uncork() is called.
 *
 * This function is safe to use with DTLS after GnuTLS 3.3.0.
 *
 * Since: 3.1.9
 **/
void gnutls_record_cork(gnutls_session_t session)
{
  session->internals.rsend_state = RECORD_SEND_CORKED;
}

/**
 * gnutls_record_uncork:
 * @session: is a #gnutls_session_t type.
 * @flags: Could be zero or %GNUTLS_RECORD_WAIT
 *
 * This resets the effect of gnutls_record_cork(), and flushes any pending
 * data. If the %GNUTLS_RECORD_WAIT flag is specified then this
 * function will block until the data is sent or a fatal error
 * occurs (i.e., the function will retry on %GNUTLS_E_AGAIN and
 * %GNUTLS_E_INTERRUPTED).
 *
 * If the flag %GNUTLS_RECORD_WAIT is not specified and the function
 * is interrupted then the %GNUTLS_E_AGAIN or %GNUTLS_E_INTERRUPTED
 * errors will be returned. To obtain the data left in the corked
 * buffer use gnutls_record_check_corked().
 *
 * Returns: On success the number of transmitted data is returned, or
 * otherwise a negative error code.
 *
 * Since: 3.1.9
 **/
int gnutls_record_uncork(gnutls_session_t session, unsigned int flags)
{
  int ret;
  ssize_t total = 0;
  record_send_state_t orig_state = session->internals.rsend_state;

  if (orig_state == RECORD_SEND_CORKED)
    session->internals.rsend_state = RECORD_SEND_NORMAL;
  else if (orig_state == RECORD_SEND_CORKED_TO_KU)
    session->internals.rsend_state = RECORD_SEND_KEY_UPDATE_1;
  else
    return 0; /* nothing to be done */

  while (session->internals.record_presend_buffer.length > 0) {
    if (flags == GNUTLS_RECORD_WAIT) {
      do {
        ret = gnutls_record_send(
          session,
          session->internals.record_presend_buffer
            .data,
          session->internals.record_presend_buffer
            .length);
      } while (ret < 0 && (ret == GNUTLS_E_AGAIN ||
               ret == GNUTLS_E_INTERRUPTED));
    } else {
      ret = gnutls_record_send(
        session,
        session->internals.record_presend_buffer.data,
        session->internals.record_presend_buffer.length);
    }
    if (ret < 0)
      goto fail;

    session->internals.record_presend_buffer.data += ret;
    session->internals.record_presend_buffer.length -= ret;
    total += ret;
  }

  return total;

fail:
  session->internals.rsend_state = orig_state;
  return ret;
}

/**
 * gnutls_record_recv:
 * @session: is a #gnutls_session_t type.
 * @data: the buffer that the data will be read into
 * @data_size: the number of requested bytes
 *
 * This function has the similar semantics with recv().  The only
 * difference is that it accepts a GnuTLS session, and uses different
 * error codes.
 * In the special case that the peer requests a renegotiation, the
 * caller will receive an error code of %GNUTLS_E_REHANDSHAKE.  In case
 * of a client, this message may be simply ignored, replied with an alert
 * %GNUTLS_A_NO_RENEGOTIATION, or replied with a new handshake,
 * depending on the client's will. A server receiving this error code
 * can only initiate a new handshake or terminate the session.
 *
 * If %EINTR is returned by the internal pull function (the default
 * is recv()) then %GNUTLS_E_INTERRUPTED will be returned.  If
 * %GNUTLS_E_INTERRUPTED or %GNUTLS_E_AGAIN is returned, you must
 * call this function again to get the data.  See also
 * gnutls_record_get_direction().
 *
 * Returns: The number of bytes received and zero on EOF (for stream
 * connections).  A negative error code is returned in case of an error.
 * The number of bytes received might be less than the requested @data_size.
 **/
ssize_t gnutls_record_recv(gnutls_session_t session, void *data,
         size_t data_size)
{
  if (unlikely(!session->internals.initial_negotiation_completed)) {
    /* this is to protect buggy applications from sending unencrypted
     * data. We allow sending however, if we are in false start handshake
     * state. */
    if (session->internals.recv_state != RECV_STATE_FALSE_START &&
        session->internals.recv_state != RECV_STATE_EARLY_START)
      return gnutls_assert_val(
        GNUTLS_E_UNAVAILABLE_DURING_HANDSHAKE);
  }

  if (IS_KTLS_ENABLED(session, GNUTLS_KTLS_RECV)) {
    return _gnutls_ktls_recv(session, data, data_size);
  } else {
    return _gnutls_recv_int(session, GNUTLS_APPLICATION_DATA, data,
          data_size, NULL,
          session->internals.record_timeout_ms);
  }
}

/**
 * gnutls_record_recv_seq:
 * @session: is a #gnutls_session_t type.
 * @data: the buffer that the data will be read into
 * @data_size: the number of requested bytes
 * @seq: is the packet's 64-bit sequence number. Should have space for 8 bytes.
 *
 * This function is the same as gnutls_record_recv(), except that
 * it returns in addition to data, the sequence number of the data.
 * This is useful in DTLS where record packets might be received
 * out-of-order. The returned 8-byte sequence number is an
 * integer in big-endian format and should be
 * treated as a unique message identification.
 *
 * Returns: The number of bytes received and zero on EOF.  A negative
 *   error code is returned in case of an error.  The number of bytes
 *   received might be less than @data_size.
 *
 * Since: 3.0
 **/
ssize_t gnutls_record_recv_seq(gnutls_session_t session, void *data,
             size_t data_size, unsigned char *seq)
{
  return _gnutls_recv_int(session, GNUTLS_APPLICATION_DATA, data,
        data_size, seq,
        session->internals.record_timeout_ms);
}

/**
 * gnutls_record_set_timeout:
 * @session: is a #gnutls_session_t type.
 * @ms: is a timeout value in milliseconds
 *
 * This function sets the receive timeout for the record layer
 * to the provided value. Use an @ms value of zero to disable
 * timeout (the default), or %GNUTLS_INDEFINITE_TIMEOUT, to
 * set an indefinite timeout.
 *
 * This function requires to set a pull timeout callback. See
 * gnutls_transport_set_pull_timeout_function().
 *
 * Since: 3.1.7
 **/
void gnutls_record_set_timeout(gnutls_session_t session, unsigned int ms)
{
  session->internals.record_timeout_ms = ms;
}

/**
 * gnutls_handshake_write:
 * @session: is a #gnutls_session_t type.
 * @level: the current encryption level for reading a handshake message
 * @data: the (const) handshake data to be processed
 * @data_size: the size of data
 *
 * This function processes a handshake message in the encryption level
 * specified with @level. Prior to calling this function, a handshake
 * read callback must be set on @session. Use
 * gnutls_handshake_set_read_function() to do this.
 *
 * Since: 3.7.0
 */
int gnutls_handshake_write(gnutls_session_t session,
         gnutls_record_encryption_level_t level,
         const void *data, size_t data_size)
{
  record_parameters_st *record_params;
  record_state_st *record_state;
  mbuffer_st *bufel;
  uint8_t *p;
  int ret;

  /* DTLS is not supported */
  if (IS_DTLS(session))
    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  /* Nothing to do */
  if (data_size == 0)
    return gnutls_assert_val(0);

  /* When using this, the outgoing handshake messages should
   * also be handled manually unless KTLS is enabled exclusively
   * in GNUTLS_KTLS_RECV mode in which case the outgoing messages
   * are handled by GnuTLS.
   */
  if (!session->internals.h_read_func &&
      !IS_KTLS_ENABLED(session, GNUTLS_KTLS_RECV))
    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  if (session->internals.initial_negotiation_completed) {
    const version_entry_st *vers = get_version(session);
    if (unlikely(vers == NULL || !vers->tls13_sem))
      return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
  }

  ret = _gnutls_epoch_get(session, EPOCH_READ_CURRENT, &record_params);
  if (ret < 0)
    return gnutls_assert_val(ret);

  record_state = &record_params->read;
  if (record_state->level > level)
    return gnutls_assert_val(GNUTLS_E_DECRYPTION_FAILED);

  bufel = _mbuffer_alloc_align16(data_size, 0);
  if (bufel == NULL)
    return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

  memcpy(_mbuffer_get_udata_ptr(bufel), data, data_size);
  _mbuffer_set_udata_size(bufel, data_size);
  p = _mbuffer_get_udata_ptr(bufel);
  bufel->htype = p[0];

  if (sequence_increment(session, &record_state->sequence_number) != 0) {
    _mbuffer_xfree(&bufel);
    return gnutls_assert_val(GNUTLS_E_RECORD_LIMIT_REACHED);
  }

  _gnutls_record_buffer_put(session, GNUTLS_HANDSHAKE,
          record_state->sequence_number, bufel);

  if (session->internals.initial_negotiation_completed)
    return _gnutls13_recv_async_handshake(session);

  return 0;
}

Coverage Report

Created: 2025-03-18 06:55