app-MAIL-temp/app/dns_utils.py
2020-11-16 19:16:06 +01:00

98 lines
2.2 KiB
Python

from typing import Optional
import dns.resolver
def _get_dns_resolver():
my_resolver = dns.resolver.Resolver()
# 1.1.1.1 is CloudFlare's public DNS server
my_resolver.nameservers = ["1.1.1.1"]
return my_resolver
def get_ns(hostname) -> [str]:
try:
answers = _get_dns_resolver().resolve(hostname, "NS")
except:
return []
return [a.to_text() for a in answers]
def get_cname_record(hostname) -> Optional[str]:
"""Return the CNAME record if exists for a domain, WITHOUT the trailing period at the end"""
try:
answers = _get_dns_resolver().query(hostname, "CNAME")
except Exception:
return None
for a in answers:
ret = a.to_text()
return ret[:-1]
return None
def get_mx_domains(hostname) -> [(int, str)]:
"""return list of (priority, domain name).
domain name ends with a "." at the end.
"""
try:
answers = _get_dns_resolver().query(hostname, "MX")
except Exception:
return []
ret = []
for a in answers:
record = a.to_text() # for ex '20 alt2.aspmx.l.google.com.'
parts = record.split(" ")
ret.append((int(parts[0]), parts[1]))
return ret
_include_spf = "include:"
def get_spf_domain(hostname) -> [str]:
"""return all domains listed in *include:*"""
try:
answers = _get_dns_resolver().query(hostname, "TXT")
except Exception:
return []
ret = []
for a in answers: # type: dns.rdtypes.ANY.TXT.TXT
for record in a.strings:
record = record.decode() # record is bytes
if record.startswith("v=spf1"):
parts = record.split(" ")
for part in parts:
if part.startswith(_include_spf):
ret.append(part[part.find(_include_spf) + len(_include_spf) :])
return ret
def get_txt_record(hostname) -> [str]:
"""return all domains listed in *include:*"""
try:
answers = _get_dns_resolver().query(hostname, "TXT")
except Exception:
return []
ret = []
for a in answers: # type: dns.rdtypes.ANY.TXT.TXT
for record in a.strings:
record = record.decode() # record is bytes
ret.append(record)
return ret