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#!/usr/bin/env python3
#
# Tests the DNS configuration of a Mail-in-a-Box.
#
# tests/dns.py ipaddr hostname
#
# where ipaddr is the IP address of your Mail-in-a-Box
# and hostname is the domain name to check the DNS for.
import sys, re, difflib
import dns.reversename, dns.resolver
if len(sys.argv) < 3:
print("Usage: tests/dns.py ipaddress hostname [primary hostname]")
sys.exit(1)
ipaddr, hostname = sys.argv[1:3]
primary_hostname = hostname
if len(sys.argv) == 4:
primary_hostname = sys.argv[3]
def test(server, description):
tests = [
(hostname, "A", ipaddr),
#(hostname, "NS", "ns1.%s.;ns2.%s." % (primary_hostname, primary_hostname)),
("ns1." + primary_hostname, "A", ipaddr),
("ns2." + primary_hostname, "A", ipaddr),
("www." + hostname, "A", ipaddr),
(hostname, "MX", "10 " + primary_hostname + "."),
(hostname, "TXT", "\"v=spf1 mx -all\""),
("mail._domainkey." + hostname, "TXT", "\"v=DKIM1; k=rsa; s=email; \" \"p=__KEY__\""),
#("_adsp._domainkey." + hostname, "TXT", "\"dkim=all\""),
("_dmarc." + hostname, "TXT", "\"v=DMARC1; p=quarantine\""),
]
return test2(tests, server, description)
def test_ptr(server, description):
ipaddr_rev = dns.reversename.from_address(ipaddr)
tests = [
(ipaddr_rev, "PTR", hostname+'.'),
]
return test2(tests, server, description)
def test2(tests, server, description):
first = True
resolver = dns.resolver.get_default_resolver()
resolver.nameservers = [server]
for qname, rtype, expected_answer in tests:
# do the query and format the result as a string
try:
response = dns.resolver.query(qname, rtype)
except dns.resolver.NoNameservers:
# host did not have an answer for this query
print("Could not connect to %s for DNS query." % server)
sys.exit(1)
except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
# host did not have an answer for this query; not sure what the
# difference is between the two exceptions
response = ["[no value]"]
response = ";".join(str(r) for r in response)
response = re.sub(r"(\"p=).*(\")", r"\1__KEY__\2", response) # normalize DKIM key
response = response.replace("\"\" ", "") # normalize TXT records (DNSSEC signing inserts empty text string components)
# is it right?
if response == expected_answer:
#print(server, ":", qname, rtype, "?", response)
continue
# show prolem
if first:
print("Incorrect DNS Response from", description)
print()
print("QUERY ", "RESPONSE ", "CORRECT VALUE", sep='\t')
first = False
print((qname + "/" + rtype).ljust(20), response.ljust(12), expected_answer, sep='\t')
return first # success
# Test the response from the machine itself.
if not test(ipaddr, "Mail-in-a-Box"):
print ()
print ("Please run the Mail-in-a-Box setup script on %s again." % hostname)
sys.exit(1)
else:
print ("The Mail-in-a-Box provided correct DNS answers.")
print ()
# If those settings are OK, also test Google's Public DNS
# to see if the machine is hooked up to recursive DNS properly.
if not test("8.8.8.8", "Google Public DNS"):
print ()
print ("Check that the nameserver settings for %s are correct at your domain registrar. It may take a few hours for Google Public DNS to update after changes on your Mail-in-a-Box." % hostname)
sys.exit(1)
else:
print ("Your domain registrar or DNS host appears to be configured correctly as well. Public DNS provides the same answers.")
print ()
# And if that's OK, also check reverse DNS (the PTR record).
if not test_ptr("8.8.8.8", "Google Public DNS (Reverse DNS)"):
print ()
print ("The reverse DNS for %s is not correct. Consult your ISP for how to set the reverse DNS (also called the PTR record) for %s to %s." % (hostname, hostname, ipaddr))
sys.exit(1)
else:
print ("And the reverse DNS for the domain is correct.")
print ()
print ("DNS is OK.")