sslhandling.py

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import os
import sys
import ssl

import configparser


def ssl_settings(host, config_file, env=os.environ):
    """
    Function which generates SSL setting for cassandra.Cluster

    Params:
    * host .........: hostname of Cassandra node.
    * env ..........: environment variables. SSL factory will use, if passed,
                      SSL_CERTFILE and SSL_VALIDATE variables.
    * config_file ..: path to cqlsh config file (usually ~/.cqlshrc).
                      SSL factory will use, if set, certfile and validate
                      options in [ssl] section, as well as host to certfile
                      mapping in [certfiles] section.

    [certfiles] section is optional, 'validate' setting in [ssl] section is
    optional too. If validation is enabled then SSL certfile must be provided
    either in the config file or as an environment variable.
    Environment variables override any options set in cqlsh config file.
    """
    configs = configparser.ConfigParser()
    configs.read(config_file)

    def get_option(section, option):
        try:
            return configs.get(section, option)
        except configparser.Error:
            return None

    def get_best_tls_protocol(ssl_ver_str):
        if ssl_ver_str:
            print("Warning: Explicit SSL and TLS versions in the cqlshrc file or in SSL_VERSION environment property are ignored as the protocol is auto-negotiated.\n")
        return ssl.PROTOCOL_TLS_CLIENT

    ssl_validate = env.get('SSL_VALIDATE')
    if ssl_validate is None:
        ssl_validate = get_option('ssl', 'validate')
    ssl_validate = ssl_validate is None or ssl_validate.lower() != 'false'

    ssl_check_hostname = env.get('SSL_CHECK_HOSTNAME')
    if ssl_check_hostname is None:
        ssl_check_hostname = get_option('ssl', 'check_hostname')
    ssl_check_hostname = ssl_check_hostname is not None and ssl_check_hostname.lower() != 'false'

    if ssl_check_hostname and not ssl_validate:
        sys.exit("SSL certificate hostname checking "
                 "(`check_hostname` in the [ssl] section) must be turned off "
                 "if certificate `validate` is turned off.")
        
    ssl_version_str = env.get('SSL_VERSION')
    if ssl_version_str is None:
        ssl_version_str = get_option('ssl', 'version')

    ssl_version = get_best_tls_protocol(ssl_version_str)

    ssl_certfile = env.get('SSL_CERTFILE')
    if ssl_certfile is None:
        ssl_certfile = get_option('certfiles', host)
    if ssl_certfile is None:
        ssl_certfile = get_option('ssl', 'certfile')
    if ssl_validate and ssl_certfile is None:
        sys.exit("Validation is enabled; SSL transport factory requires a valid certfile "
                 "to be specified. Please provide path to the certfile in [ssl] section "
                 "as 'certfile' option in %s (or use [certfiles] section) or set SSL_CERTFILE "
                 "environment variable." % (config_file,))
    if ssl_certfile is not None:
        ssl_certfile = os.path.expanduser(ssl_certfile)

    userkey = get_option('ssl', 'userkey')
    if userkey:
        userkey = os.path.expanduser(userkey)
    usercert = get_option('ssl', 'usercert')
    if usercert:
        usercert = os.path.expanduser(usercert)

    ssl_context = ssl.SSLContext(ssl_version)
    ssl_context.check_hostname = ssl_check_hostname
    if usercert and userkey:
        ssl_context.load_cert_chain(certfile=usercert,
                                    keyfile=userkey)
    if (usercert and not userkey) or (userkey and not usercert):
        print("Warning: userkey and usercert from [ssl] section, should be both configured, otherwise won't be used")

    ssl_context.verify_mode = ssl.CERT_REQUIRED if ssl_validate else ssl.CERT_NONE
    if ssl_certfile:
        ssl_context.load_verify_locations(cafile=ssl_certfile)

    return ssl_context