386 lines
16 KiB
Python
Executable File
386 lines
16 KiB
Python
Executable File
#!/usr/bin/python3
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#
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# Checks that the upstream DNS has been set correctly and that
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# SSL certificates have been signed, etc., and if not tells the user
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# what to do next.
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__ALL__ = ['check_certificate']
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import os, os.path, re, subprocess
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import dns.reversename, dns.resolver
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from dns_update import get_dns_zones
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from web_update import get_web_domains, get_domain_ssl_files
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from mailconfig import get_mail_domains, get_mail_aliases
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from utils import shell, sort_domains
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def run_checks(env):
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run_system_checks(env)
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run_domain_checks(env)
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def run_system_checks(env):
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print("System")
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print("======")
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# Check that SSH login with password is disabled.
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sshd = open("/etc/ssh/sshd_config").read()
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if re.search("\nPasswordAuthentication\s+yes", sshd) \
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or not re.search("\nPasswordAuthentication\s+no", sshd):
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print_error("""The SSH server on this machine permits password-based login. A more secure
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way to log in is using a public key. Add your SSH public key to $HOME/.ssh/authorized_keys, check
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that you can log in without a password, set the option 'PasswordAuthentication no' in
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/etc/ssh/sshd_config, and then restart the openssh via 'sudo service ssh restart'.""")
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else:
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print_ok("SSH disallows password-based login.")
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print()
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def run_domain_checks(env):
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# Get the list of domains we handle mail for.
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mail_domains = get_mail_domains(env)
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# Get the list of domains we serve DNS zones for (i.e. does not include subdomains).
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dns_zonefiles = dict(get_dns_zones(env))
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dns_domains = set(dns_zonefiles)
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# Get the list of domains we serve HTTPS for.
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web_domains = set(get_web_domains(env))
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# Check the domains.
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for domain in sort_domains(mail_domains | dns_domains | web_domains, env):
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print(domain)
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print("=" * len(domain))
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if domain == env["PRIMARY_HOSTNAME"]:
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check_primary_hostname_dns(domain, env)
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if domain in dns_domains:
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check_dns_zone(domain, env, dns_zonefiles)
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if domain in mail_domains:
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check_mail_domain(domain, env)
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if domain == env["PRIMARY_HOSTNAME"] or domain in web_domains:
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# We need a SSL certificate for PRIMARY_HOSTNAME because that's where the
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# user will log in with IMAP or webmail. Any other domain we serve a
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# website for also needs a signed certificate.
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check_ssl_cert(domain, env)
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print()
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def check_primary_hostname_dns(domain, env):
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# Check that the ns1/ns2 hostnames resolve to A records. This information probably
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# comes from the TLD since the information is set at the registrar.
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ip = query_dns("ns1." + domain, "A") + '/' + query_dns("ns2." + domain, "A")
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if ip == env['PUBLIC_IP'] + '/' + env['PUBLIC_IP']:
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print_ok("Nameserver IPs are correct at registrar. [ns1/ns2.%s => %s]" % (env['PRIMARY_HOSTNAME'], env['PUBLIC_IP']))
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else:
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print_error("""Nameserver IP addresses are incorrect. The ns1.%s and ns2.%s nameservers must be configured at your domain name
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registrar as having the IP address %s. They currently report addresses of %s. It may take several hours for
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public DNS to update after a change."""
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% (env['PRIMARY_HOSTNAME'], env['PRIMARY_HOSTNAME'], env['PUBLIC_IP'], ip))
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# Check that PRIMARY_HOSTNAME resolves to PUBLIC_IP in public DNS.
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ip = query_dns(domain, "A")
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if ip == env['PUBLIC_IP']:
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print_ok("Domain resolves to box's IP address. [%s => %s]" % (env['PRIMARY_HOSTNAME'], env['PUBLIC_IP']))
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else:
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print_error("""This domain must resolve to your box's IP address (%s) in public DNS but it currently resolves
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to %s. It may take several hours for public DNS to update after a change. This problem may result from other
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issues listed here."""
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% (env['PUBLIC_IP'], ip))
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# Check reverse DNS on the PRIMARY_HOSTNAME. Note that it might not be
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# a DNS zone if it is a subdomain of another domain we have a zone for.
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ipaddr_rev = dns.reversename.from_address(env['PUBLIC_IP'])
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existing_rdns = query_dns(ipaddr_rev, "PTR")
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if existing_rdns == domain:
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print_ok("Reverse DNS is set correctly at ISP. [%s => %s]" % (env['PUBLIC_IP'], env['PRIMARY_HOSTNAME']))
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else:
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print_error("""Your box's reverse DNS is currently %s, but it should be %s. Your ISP or cloud provider will have instructions
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on setting up reverse DNS for your box at %s.""" % (existing_rdns, domain, env['PUBLIC_IP']) )
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# Check that the hostmaster@ email address exists.
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check_alias_exists("hostmaster@" + domain, env)
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def check_alias_exists(alias, env):
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mail_alises = dict(get_mail_aliases(env))
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if alias in mail_alises:
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print_ok("%s exists as a mail alias [=> %s]" % (alias, mail_alises[alias]))
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else:
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print_error("""You must add a mail alias for %s and direct email to you or another administrator.""" % alias)
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def check_dns_zone(domain, env, dns_zonefiles):
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# We provide a DNS zone for the domain. It should have NS records set up
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# at the domain name's registrar pointing to this box.
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existing_ns = query_dns(domain, "NS")
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correct_ns = "ns1.BOX; ns2.BOX".replace("BOX", env['PRIMARY_HOSTNAME'])
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if existing_ns == correct_ns:
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print_ok("Nameservers are set correctly at registrar. [%s]" % correct_ns)
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else:
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print_error("""The nameservers set on this domain are incorrect. They are currently %s. Use your domain name registar's
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control panel to set the nameservers to %s."""
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% (existing_ns, correct_ns) )
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# See if the domain's A record resolves to our PUBLIC_IP. This is already checked
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# for PRIMARY_HOSTNAME, for which it is required. For other domains it is just nice
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# to have if we want web.
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if domain != env['PRIMARY_HOSTNAME']:
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ip = query_dns(domain, "A")
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if ip == env['PUBLIC_IP']:
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print_ok("Domain resolves to this box's IP address. [%s => %s]" % (domain, env['PUBLIC_IP']))
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else:
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print_error("""This domain should resolve to your box's IP address (%s) if you would like the box to serve
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webmail or a website on this domain. The domain currently resolves to %s in public DNS. It may take several hours for
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public DNS to update after a change. This problem may result from other issues listed here.""" % (env['PUBLIC_IP'], ip))
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# See if the domain has a DS record set.
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ds = query_dns(domain, "DS", nxdomain=None)
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ds_correct = open('/etc/nsd/zones/' + dns_zonefiles[domain] + '.ds').read().strip()
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ds_expected = re.sub(r"\S+\.\s+3600\s+IN\s+DS\s*", "", ds_correct)
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if ds == ds_expected:
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print_ok("DNS 'DS' record is set correctly at registrar.")
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elif ds == None:
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print_error("""This domain's DNS DS record is not set. The DS record is optional. The DS record activates DNSSEC.
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To set a DS record, you must follow the instructions provided by your domain name registrar and provide to them this information:""")
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print("")
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print(" " + ds_correct)
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print("")
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else:
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print_error("""This domain's DNS DS record is incorrect. The chain of trust is broken between the public DNS system
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and this machine's DNS server. It may take several hours for public DNS to update after a change. If you did not recently
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make a change, you must resolve this immediately by following the instructions provided by your domain name registrar and
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provide to them this information:""")
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print("")
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print(" " + ds_correct)
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print("")
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def check_mail_domain(domain, env):
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# Check the MX record.
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mx = query_dns(domain, "MX", nxdomain=None)
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expected_mx = "10 " + env['PRIMARY_HOSTNAME']
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if mx == expected_mx:
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print_ok("Domain's email is directed to this domain. [%s => %s]" % (domain, mx))
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elif mx == None:
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# A missing MX record is okay on the primary hostname because
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# the primary hostname's A record (the MX fallback) is... itself,
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# which is what we want the MX to be.
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if domain == env['PRIMARY_HOSTNAME']:
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print_ok("Domain's email is directed to this domain. [%s has no MX record, which is ok]" % (domain,))
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# And a missing MX record is okay on other domains if the A record
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# matches the A record of the PRIMARY_HOSTNAME. Actually this will
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# probably confuse DANE TLSA, but we'll let that slide for now.
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else:
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domain_a = query_dns(domain, "A", nxdomain=None)
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primary_a = query_dns(env['PRIMARY_HOSTNAME'], "A", nxdomain=None)
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if domain_a != None and domain_a == primary_a:
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print_ok("Domain's email is directed to this domain. [%s has no MX record but its A record is OK]" % (domain,))
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else:
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print_error("""This domain's DNS MX record is not set. It should be '%s'. Mail will not
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be delivered to this box. It may take several hours for public DNS to update after a
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change. This problem may result from other issues listed here.""" % (expected_mx,))
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else:
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print_error("""This domain's DNS MX record is incorrect. It is currently set to '%s' but should be '%s'. Mail will not
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be delivered to this box. It may take several hours for public DNS to update after a change. This problem may result from
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other issues listed here.""" % (mx, expected_mx))
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# Check that the postmaster@ email address exists.
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check_alias_exists("postmaster@" + domain, env)
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def query_dns(qname, rtype, nxdomain='[Not Set]'):
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resolver = dns.resolver.get_default_resolver()
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try:
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response = dns.resolver.query(qname, rtype)
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except (dns.resolver.NoNameservers, dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
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# Host did not have an answer for this query; not sure what the
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# difference is between the two exceptions.
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return nxdomain
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# There may be multiple answers; concatenate the response. Remove trailing
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# periods from responses since that's how qnames are encoded in DNS but is
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# confusing for us.
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return "; ".join(str(r).rstrip('.') for r in response)
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def check_ssl_cert(domain, env):
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# Check that SSL certificate is signed.
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# Skip the check if the A record is not pointed here.
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if query_dns(domain, "A") != env['PUBLIC_IP']: return
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# Where is the SSL stored?
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ssl_key, ssl_certificate, ssl_csr_path = get_domain_ssl_files(domain, env)
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if not os.path.exists(ssl_certificate):
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print_error("The SSL certificate file for this domain is missing.")
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return
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# Check that the certificate is good.
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cert_status = check_certificate(domain, ssl_certificate, ssl_key)
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if cert_status == "SELF-SIGNED":
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fingerprint = shell('check_output', [
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"openssl",
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"x509",
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"-in", ssl_certificate,
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"-noout",
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"-fingerprint"
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])
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fingerprint = re.sub(".*Fingerprint=", "", fingerprint).strip()
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if domain == env['PRIMARY_HOSTNAME']:
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print_error("""The SSL certificate for this domain is currently self-signed. You will get a security
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warning when you check or send email and when visiting this domain in a web browser (for webmail or
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static site hosting). You may choose to confirm the security exception, but check that the certificate
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fingerprint matches the following:""")
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print()
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print(" " + fingerprint)
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else:
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print_error("""The SSL certificate for this domain is currently self-signed. Visitors to a website on
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this domain will get a security warning. If you are not serving a website on this domain, then it is
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safe to leave the self-signed certificate in place.""")
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print()
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print_block("""You can purchase a signed certificate from many places. You will need to provide this Certificate Signing Request (CSR)
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to whoever you purchase the SSL certificate from:""")
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print()
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print(open(ssl_csr_path).read().strip())
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print()
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print_block("""When you purchase an SSL certificate you will receive a certificate in PEM format and possibly a file containing intermediate certificates in PEM format.
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If you receive intermediate certificates, use a text editor and paste your certificate on top and then the intermediate certificates
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below it. Save the file and place it onto this machine at %s. Then run "service nginx restart".""" % ssl_certificate)
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elif cert_status == "OK":
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print_ok("SSL certificate is signed & valid.")
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else:
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print_error("The SSL certificate has a problem:")
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print("")
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print(cert_status)
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print("")
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def check_certificate(domain, ssl_certificate, ssl_private_key):
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# Use openssl verify to check the status of a certificate.
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# First check that the certificate is for the right domain. The domain
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# must be found in the Subject Common Name (CN) or be one of the
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# Subject Alternative Names.
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cert_dump = shell('check_output', [
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"openssl", "x509",
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"-in", ssl_certificate,
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"-noout", "-text", "-nameopt", "rfc2253",
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])
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cert_dump = cert_dump.split("\n")
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certificate_names = set()
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while len(cert_dump) > 0:
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line = cert_dump.pop(0)
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# Grab from the Subject Common Name. We include the indentation
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# at the start of the line in case maybe the cert includes the
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# common name of some other referenced entity (which would be
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# indented, I hope).
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m = re.match(" Subject: CN=([^,]+)", line)
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if m:
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certificate_names.add(m.group(1))
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# Grab from the Subject Alternative Name, which is a comma-delim
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# list of names, like DNS:mydomain.com, DNS:otherdomain.com.
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m = re.match(" X509v3 Subject Alternative Name:", line)
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if m:
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names = re.split(",\s*", cert_dump.pop(0).strip())
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for n in names:
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m = re.match("DNS:(.*)", n)
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if m:
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certificate_names.add(m.group(1))
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if domain is not None and domain not in certificate_names:
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return "This certificate is for the wrong domain names. It is for %s." % \
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", ".join(sorted(certificate_names))
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# Second, check that the certificate matches the private key. Get the modulus of the
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# private key and of the public key in the certificate. They should match. The output
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# of each command looks like "Modulus=XXXXX".
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if ssl_private_key is not None:
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private_key_modulus = shell('check_output', [
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"openssl", "rsa",
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"-inform", "PEM",
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"-noout", "-modulus",
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"-in", ssl_private_key])
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cert_key_modulus = shell('check_output', [
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"openssl", "x509",
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"-in", ssl_certificate,
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"-noout", "-modulus"])
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if private_key_modulus != cert_key_modulus:
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return "The certificate installed at %s does not correspond to the private key at %s." % (ssl_certificate, ssl_private_key)
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# Next validate that the certificate is valid. This checks whether the certificate
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# is self-signed, that the chain of trust makes sense, that it is signed by a CA
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# that Ubuntu has installed on this machine's list of CAs, and I think that it hasn't
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# expired.
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# In order to verify with openssl, we need to split out any
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# intermediary certificates in the chain (if any) from our
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# certificate (at the top). They need to be passed separately.
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cert = open(ssl_certificate).read()
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m = re.match(r'(-*BEGIN CERTIFICATE-*.*?-*END CERTIFICATE-*)(.*)', cert, re.S)
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if m == None:
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return "The certificate file is an invalid PEM certificate."
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mycert, chaincerts = m.groups()
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# This command returns a non-zero exit status in most cases, so trap errors.
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retcode, verifyoutput = shell('check_output', [
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"openssl",
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"verify", "-verbose",
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"-purpose", "sslserver", "-policy_check",]
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+ ([] if chaincerts.strip() == "" else ["-untrusted", "/dev/stdin"])
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+ [ssl_certificate],
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input=chaincerts.encode('ascii'),
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trap=True)
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if "self signed" in verifyoutput:
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# Certificate is self-signed.
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return "SELF-SIGNED"
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elif retcode == 0:
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# Certificate is OK.
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return "OK"
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else:
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return verifyoutput.strip()
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def print_ok(message):
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print_block(message, first_line="✓ ")
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def print_error(message):
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print_block(message, first_line="✖ ")
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try:
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terminal_columns = int(shell('check_output', ['stty', 'size']).split()[1])
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except:
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terminal_columns = 76
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def print_block(message, first_line=" "):
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print(first_line, end='')
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message = re.sub("\n\s*", " ", message)
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words = re.split("(\s+)", message)
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linelen = 0
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for w in words:
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if linelen + len(w) > terminal_columns-1-len(first_line):
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print()
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print(" ", end="")
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linelen = 0
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if linelen == 0 and w.strip() == "": continue
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print(w, end="")
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linelen += len(w)
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if linelen > 0:
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print()
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if __name__ == "__main__":
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from utils import load_environment
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run_checks(load_environment())
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