How to allow python to trust my server's TLS self-signed certificate: ssl.SSLError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed

Question

This is not a duplicate for this post . I tried the solutions there and nothing works in my case.

I am using Windows and Python 3.6.5. I have a python script for a TLS client. The server I need to connect to uses a self-signed certificate. When I try to connect to it using my script, I get this error:

ssl.SSLError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:833)

I need to parse the certificate. I tried to add my server's certificate .pem content to file named: cacert.pem which is in: C:\\Python36\\Lib\\site-packages\\certifi and run the program again. Nothing change. Here is my scripot. Please help me to make the client make exception for this server as I trust its certificate.

import socket, ssl
import itertools

context = ssl.SSLContext() 
context.verify_mode = ssl.CERT_OPTIONAL 
context.check_hostname = False

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
domain="192.168.56.3" # my server
ssl_sock = context.wrap_socket(s, server_hostname=domain)
ssl_sock.connect((domain, 443))

print("====== peer's certificate ======")
try:
    cert = ssl_sock.getpeercert()
    print(cert)
except SSLError as e:
    print("Error: ",e)
ssl_sock.close()

Answer 1

This question has been idle for a while, but in case somebody is still struggling with connecting to a server with a self-signed certificate via Python ssl library:

You can use the load_verify_locations method of SSLContext to specify custom self-signed root certs (see Python Docs for load_verify_locations ).

The forementioned code could be extended as follows:

...

context = ssl.SSLContext() 
context.verify_mode = ssl.CERT_OPTIONAL 
context.check_hostname = False

context.load_verify_locations(cafile='/path/to/your/cacert.pem')

...

Be aware that you also need to include public root certs in case you want to connect to other servers with public certificates with the same client/context. (you could for example append your cacert.pem content to the certifi root certificates and reference that folder / path instead).

See also this Python docs paragraph for more information: client-side operations .