CCT-176: Handle incorrectly closed TLS connections

* Card ID: CCT-176
* Card ID: RHEL-17345

Some servers, like Quarkus, do not send the `close_notify` alert before
closing their connection by default. This would cause
subscription-manager to freeze until the TLS connection timeout was
reached.

This patch ensures we set our own timeout equal to 3x the response time
of the connection, to kill the connection if we don't get a response
back.

src/rhsm/connection.py

@@ -15,12 +15,15 @@
 #
 
 import base64
+import math
+
 from rhsm import certificate
 import datetime
 import dateutil.parser
 import locale
 import logging
 import os
+import signal
 import socket
 import sys
 import time
@@ -666,23 +669,53 @@ def __init__(
             self.headers["Authorization"] = "Bearer " + token
 
     def close_connection(self) -> None:
+        """Try to close connection to the server.
+
+        Because the server's TLS stack may misbehave (there are behavioral
+        differences between 1.2 and 1.3, for example), we handle timeouts of
+        closing TLS connection manually. If the server does not respond within
+        '3 * average return time' seconds, we force the connection down.
+
+        After TLS connection has been closed, we close the TCP connection.
         """
-        Try to close connection to server
-        :return: None
-        """
-        if self.__conn is not None:
-            # Do proper TLS shutdown handshake (TLS tear down) first
-            if self.__conn.sock is not None:
-                log.debug(f"Closing HTTPS connection {self.__conn.sock}")
-                try:
-                    self.__conn.sock.unwrap()
-                except ssl.SSLError as err:
-                    log.debug(f"Unable to close TLS connection properly: {err}")
-                else:
-                    log.debug("TLS connection closed")
-            # Then it is possible to close TCP connection
+        if self.__conn is None:
+            return
+
+        if self.__conn.sock is None:
+            log.debug(f"Closing TCP connection to {self.__conn.host}")
             self.__conn.close()
+            self.__conn = None
+            log.debug("TCP connection has been closed")
+            return
+
+        log.debug(f"Closing TLS connection {self.__conn.sock}")
+
+        # The server may not send the `close_notify` alert when it closes the
+        # connection on its side.
+        # Here we set a timeout equal to three times the measured response time
+        # to prevent the connection from waiting until TCP timeout.
+        # See RHEL-17345.
+        response_time: float = self.smoothed_rt or 0.5
+        timeout_time: int = math.ceil(response_time * 3)
+
+        def on_timeout(signum, frame) -> None:
+            raise TimeoutError(f"Did not get response in {timeout_time}s")
+
+        signal.signal(signalnum=signal.SIGALRM, handler=on_timeout)
+        signal.alarm(timeout_time)
+
+        try:
+            self.__conn.sock.unwrap()
+        except (ssl.SSLError, TimeoutError) as err:
+            log.debug(f"TLS connection could not be closed: {err}")
+        else:
+            signal.alarm(0)
+            log.debug("TLS connection has been closed")
+
+        log.debug(f"Closing TCP connection to {self.__conn.host}")
+        self.__conn.close()
         self.__conn = None
+        log.debug("TCP connection has been closed")
 
     def _get_cert_key_list(self) -> List[Tuple[str, str]]:
         """
@@ -1227,7 +1260,10 @@ def _update_smoothed_response_time(self, response_time: float):
             self.smoothed_rt = response_time
         else:
             self.smoothed_rt = (self.ALPHA * self.smoothed_rt) + ((1 - self.ALPHA) * response_time)
-        log.debug("Response time: %s, Smoothed response time: %s" % (response_time, self.smoothed_rt))
+        log.debug(
+            f"Latest response time was {response_time:.5f}s, "
+            f"smoothed response time is {self.smoothed_rt:.5f}s"
+        )
 
     def validateResult(self, result: dict, request_type: str = None, handler: str = None) -> None:
         """