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"""Python implementation of DNSLink protocol.""" |
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# pylint: disable=multiple-statements |
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import dns.resolver |
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def resolve(domain, protocol=None, depth=16, resolver=None): |
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""" |
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Resolve a DNSLink TXT record. |
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:param str domain: a domain to resolve |
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:param str protocol: a record protocol |
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:param int depth: a recursion depth |
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:param dns.resolver.Resolver: a DNSPython resolver |
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:return: the DNSLink records |
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:rtype: list[str] |
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""" |
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# With `_dnslink` subdomain |
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if not domain.startswith('_dnslink.'): name = '_dnslink.' + domain |
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else: name = domain |
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records = _get_and_parse_record(name, protocol, depth, resolver) |
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if records: return records |
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# Without `_dnslink` subdomain |
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if domain.startswith('_dnslink.'): name = domain[9:] |
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else: name = domain |
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records = _get_and_parse_record(name, protocol, depth, resolver) |
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if records: return records |
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# Not found |
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return [] |
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def _get_and_parse_record(domain, protocol=None, depth=16, resolver=None): |
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""" |
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Get and parse DNSLink TXT record. |
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:param str domain: a domain to resolve |
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:param str protocol: a record protocol |
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:param int depth: a recursion depth |
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:param dns.resolver.Resolver: a DNSPython resolver |
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:return: the DNSLink records |
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:rtype: list[str] |
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""" |
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if not isinstance(resolver, dns.resolver.Resolver): |
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resolver = dns.resolver.get_default_resolver() |
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try: |
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answers = resolver.query(domain, 'TXT') |
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except dns.exception.DNSException: |
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return [] |
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records = [] |
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for rdata in answers: |
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for txt in rdata.strings: |
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record = txt.decode('utf-8') |
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# Not valid TXT record |
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if not record.count('=') == 1: |
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continue |
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content = record.split('/', 3) |
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# Not valid DNSLink record |
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if not len(content) >= 3 or not content[0] == 'dnslink=': |
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continue |
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# Chaining record |
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if content[1] == 'dnslink' and depth > 1: |
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records.extend([ |
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record + ('/' + content[3] if len(content) > 3 else '') |
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for record |
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in resolve(content[2], protocol, depth - 1, resolver) |
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]) |
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# Normal record |
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elif protocol in (content[1], None): |
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content[0] = '' |
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records.append('/'.join(content)) |
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return records |
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filips123 /
DNSLinkPy
