树莓派的 MQTT 问题，SSL：UNSUPPORTED_PROTOCOL] 不受支持的协议 (_ssl.c:1056)

Question

I am running an MQTT broker on an AWS server which functions as normal on mac and windows devices does not function as expected on my raspberry pi. My subscriber and publisher code works and has been tested on multiple operating systems. I believe the issue is with my raspberry pi settings however I am unable to resolve this.

The error I am receiving (with python3):

pi@raspberrypi:~/MQTT $ sudo python3 subscriber.py 
Traceback (most recent call last):
  File "subscriber.py", line 42, in <module>
    client.connect(brokerAddress,port,60)
  File "/usr/local/lib/python3.7/dist-packages/paho/mqtt/client.py", line 937, in connect
    return self.reconnect()
  File "/usr/local/lib/python3.7/dist-packages/paho/mqtt/client.py", line 1100, in reconnect
    sock.do_handshake()
  File "/usr/lib/python3.7/ssl.py", line 1117, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLError: [SSL: UNSUPPORTED_PROTOCOL] unsupported protocol (_ssl.c:1056)

The error I am receiving with python,

pi@raspberrypi:~/MQTT $ python subscriber.py 
Traceback (most recent call last):
  File "subscriber.py", line 42, in <module>
    client.connect(brokerAddress,port,60)
  File "/home/pi/.local/lib/python2.7/site-packages/paho/mqtt/client.py", line 937, in connect
    return self.reconnect()
  File "/home/pi/.local/lib/python2.7/site-packages/paho/mqtt/client.py", line 1100, in reconnect
    sock.do_handshake()
  File "/usr/lib/python2.7/ssl.py", line 828, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLError: [SSL: UNSUPPORTED_PROTOCOL] unsupported protocol (_ssl.c:727)

I have tried several things including using python vs python3, ensuring latest versions of paho is installed, rebooting, running the raspberry pi on another network, running as sudo, and some other things too.

This may be unrelated but I have had issues trying to run git clone before on this raspberry pi, and i think it may be related to ssl issues.

Other potentially useful things

pi@raspberrypi:~/MQTT $ openssl version
OpenSSL 1.1.1d  10 Sep 2019

the code, subscriber.py:

import paho.mqtt.client as mqtt
import sys
import time
import ssl

# The callback for when the client receives a conack response from the server.
def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe("test")
    printf("subscribed to test")

# When a message is received
def on_message(client, userdata, msg):
    print("INCOMING") #begin message
    print("TOPIC: \t\t"+msg.topic+"\nMESSAGE:\t"+str(msg.payload.decode()))

client = mqtt.Client("C1")
#declare loc of tls certificate
client.tls_set('/home/pi/MQTT/ca.crt',cert_reqs=ssl.CERT_NONE)

client.tls_insecure_set(True)
client.on_connect = on_connect
client.on_message = on_message

#plain text credentials
client.username_pw_set("myusername","mypassword")

#declare address and port
brokerAddress="my-ipv4-ip-address"
port=8883
client.connect(brokerAddress,port,60)
#continuous loop
client.loop_forever()

This exact code when run on my mac works, I can publish this message from my desktop (windows) and it displays as expected.

Please do let me know if there is any other information you need from me to help troubleshoot.

Answer 1

I experienced the same issue.
The certificate I generated where TLSv1.0 certificates. but these are by default not accepted by the RPi's openssl config.
I solved this by changing the minimum accepted protocol version from v1.2 to v1.0

in /etc/ssl/openssl.cnf
changed MinProtocol = TLSv1.2 to MinProtocol = TLSv1.0