Get_server_certificate Function Of SSL Module In Python

Function Name:

get_server_certificate

Function Signature:

get_server_certificate(addr, ssl_version, PROTOCOL_TLS, ca_certs=None)

Parameters:

addr – The address of the server as a tuple consisting of hostname and port. eg.,(example.org, 443)

ssl_version – The version of the SSL/secure protocol to be used for connecting with the server. The default value is PROTOCOL_TLS.

ca_certs – Certificates of the Certificate Authority also known as root certificates.

Return Value:

The digital certificate of the server host.

Overview:

  • The function get_server_certificate() retrieves the digital certificate of a server host and validates it if root certificates are provided.
  • Internally, the function creates an ssl.SSLContext instance with the specified SSL protocol and the CA certificates passed if any. Using an instance of ssl.SSLSocket, the function connects to the specified server and retrieves the digital certificate of the server host in PEM format through the method ssl.SSLSocket.getpeercert().
  • If passed a set of root certificates (i.e, CA certificates) the function will also validate the retrieved server certificate against the CA certificates.
  • If the validation of the certificate fails, the function get_server_certificate() raises an exception ssl.SSLCertVerificationError.

 

Example1 – Get the server certificate without validating it:

import ssl

 

# Server address

serverHost = "example.com";

serverPort = "443";

serverAddress = (serverHost, serverPort);

 

# Retrieve the server certificate in PEM format

cert = ssl.get_server_certificate(serverAddress);

print(cert);

 

Output:

-----BEGIN CERTIFICATE-----

MIIHQDCCBiigAwIBAgIQD9B43Ujxor1NDyupa2A4/jANBgkqhkiG9w0BAQsFADBN

MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMScwJQYDVQQDEx5E

aWdpQ2VydCBTSEEyIFNlY3VyZSBTZXJ2ZXIgQ0EwHhcNMTgxMTI4MDAwMDAwWhcN

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X6KjBtpdvp/aXabmL95YgBjT8WJ7pqOfrqhpcmOBZa6Cg6O1l4qbIFH/Gj9hQB5I

0Gs4+eH6F9h3SojmPTYkT+8KuZ9w84Mn+M8qBXUQoYoKgIjN

-----END CERTIFICATE-----

 

Example2 – Get the server certificate and validate it:

import certifi

 

host = "example.org";

port = "443";

address = (host, port);

 

# Retrieve the server certificate and validate

cert = ssl.get_server_certificate(address, ca_certs=os.path.relpath(certifi.where()));

print(cert);

 

Output:

-----BEGIN CERTIFICATE-----

MIIHQDCCBiigAwIBAgIQD9B43Ujxor1NDyupa2A4/jANBgkqhkiG9w0BAQsFADBN

MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMScwJQYDVQQDEx5E

aWdpQ2VydCBTSEEyIFNlY3VyZSBTZXJ2ZXIgQ0EwHhcNMTgxMTI4MDAwMDAwWhcN

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0Gs4+eH6F9h3SojmPTYkT+8KuZ9w84Mn+M8qBXUQoYoKgIjN

-----END CERTIFICATE-----

 


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