app-MAIL-temp/app/dns_utils.py

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from abc import ABC, abstractmethod
from typing import List, Tuple, Optional
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import dns.resolver
from app.config import NAMESERVERS
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_include_spf = "include:"
def is_mx_equivalent(
mx_domains: List[Tuple[int, str]], ref_mx_domains: List[Tuple[int, str]]
) -> bool:
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"""
Compare mx_domains with ref_mx_domains to see if they are equivalent.
mx_domains and ref_mx_domains are list of (priority, domain)
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The priority order is taken into account but not the priority number.
For example, [(1, domain1), (2, domain2)] is equivalent to [(10, domain1), (20, domain2)]
"""
mx_domains = sorted(mx_domains, key=lambda x: x[0])
ref_mx_domains = sorted(ref_mx_domains, key=lambda x: x[0])
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if len(mx_domains) < len(ref_mx_domains):
return False
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for i in range(len(ref_mx_domains)):
if mx_domains[i][1] != ref_mx_domains[i][1]:
return False
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return True
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class DNSClient(ABC):
@abstractmethod
def get_cname_record(self, hostname: str) -> Optional[str]:
pass
@abstractmethod
def get_mx_domains(self, hostname: str) -> List[Tuple[int, str]]:
pass
def get_spf_domain(self, hostname: str) -> List[str]:
"""
return all domains listed in *include:*
"""
try:
records = self.get_txt_record(hostname)
ret = []
for record in records:
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
except Exception:
return []
@abstractmethod
def get_txt_record(self, hostname: str) -> List[str]:
pass
class NetworkDNSClient(DNSClient):
def __init__(self, nameservers: List[str]):
self._resolver = dns.resolver.Resolver()
self._resolver.nameservers = nameservers
def get_cname_record(self, hostname: str) -> Optional[str]:
"""
Return the CNAME record if exists for a domain, WITHOUT the trailing period at the end
"""
try:
answers = self._resolver.resolve(hostname, "CNAME", search=True)
for a in answers:
ret = a.to_text()
return ret[:-1]
except Exception:
return None
def get_mx_domains(self, hostname: str) -> List[Tuple[int, str]]:
"""
return list of (priority, domain name) sorted by priority (lowest priority first)
domain name ends with a "." at the end.
"""
try:
answers = self._resolver.resolve(hostname, "MX", search=True)
ret = []
for a in answers:
record = a.to_text() # for ex '20 alt2.aspmx.l.google.com.'
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parts = record.split(" ")
ret.append((int(parts[0]), parts[1]))
return sorted(ret, key=lambda x: x[0])
except Exception:
return []
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def get_txt_record(self, hostname: str) -> List[str]:
try:
answers = self._resolver.resolve(hostname, "TXT", search=True)
ret = []
for a in answers: # type: dns.rdtypes.ANY.TXT.TXT
for record in a.strings:
ret.append(record.decode())
return ret
except Exception:
return []
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class InMemoryDNSClient(DNSClient):
def __init__(self):
self.cname_records: dict[str, Optional[str]] = {}
self.mx_records: dict[str, List[Tuple[int, str]]] = {}
self.spf_records: dict[str, List[str]] = {}
self.txt_records: dict[str, List[str]] = {}
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def set_cname_record(self, hostname: str, cname: str):
self.cname_records[hostname] = cname
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def set_mx_records(self, hostname: str, mx_list: List[Tuple[int, str]]):
self.mx_records[hostname] = mx_list
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def set_txt_record(self, hostname: str, txt_list: List[str]):
self.txt_records[hostname] = txt_list
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def get_cname_record(self, hostname: str) -> Optional[str]:
return self.cname_records.get(hostname)
def get_mx_domains(self, hostname: str) -> List[Tuple[int, str]]:
mx_list = self.mx_records.get(hostname, [])
return sorted(mx_list, key=lambda x: x[0])
def get_txt_record(self, hostname: str) -> List[str]:
return self.txt_records.get(hostname, [])
def get_network_dns_client() -> NetworkDNSClient:
return NetworkDNSClient(NAMESERVERS)
def get_mx_domains(hostname: str) -> [(int, str)]:
return get_network_dns_client().get_mx_domains(hostname)