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# This software is provided 'as-is', without any express or implied
# warranty. In no event will the author be held liable for any damages
# arising from the use of this software.
#
# Permission is granted to anyone to use this software for any purpose,
# including commercial applications, and to alter it and redistribute it
# freely, subject to the following restrictions:
#
# 1. The origin of this software must not be misrepresented; you must not
# claim that you wrote the original software. If you use this software
# in a product, an acknowledgment in the product documentation would be
# appreciated but is not required.
# 2. Altered source versions must be plainly marked as such, and must not be
# misrepresented as being the original software.
# 3. This notice may not be removed or altered from any source distribution.
#
# Copyright (c) 2008 Greg Hewgill http://hewgill.com
#
# This has been modified from the original software.
# Copyright (c) 2011 William Grant <me@williamgrant.id.au>
__all__ = [
'get_txt'
]
def get_txt_dnspython(name, timeout=5):
"""Return a TXT record associated with a DNS name."""
import dkim
try:
a = dns.resolver.resolve(name, dns.rdatatype.TXT,raise_on_no_answer=False, lifetime=timeout, search=True)
for r in a.response.answer:
if r.rdtype == dns.rdatatype.TXT:
return b"".join(list(r.items)[0].strings)
except dns.resolver.NXDOMAIN: pass
except dns.resolver.NoNameservers: pass
except dns.resolver.NoResolverConfiguration as e:
raise dkim.DnsTimeoutError('dns.resolver.NoResolverConfiguration: {0}'.format(e))
except dns.exception.Timeout as e:
raise dkim.DnsTimeoutError('dns.exception.Timeout: {0}'.format(e))
return None
def get_txt_pydns(name, timeout=5):
"""Return a TXT record associated with a DNS name."""
# Older pydns releases don't like a trailing dot.
if name.endswith('.'):
name = name[:-1]
response = DNS.DnsRequest(name, qtype='txt', timeout=timeout).req()
if not response.answers:
return None
for answer in response.answers:
if answer['typename'].lower() == 'txt':
return b''.join(answer['data'])
return None
# No longer used since it doesn't support timeout
def get_txt_Milter_dns(name, timeout=5):
"""Return a TXT record associated with a DNS name."""
# Older pydns releases don't like a trailing dot.
if name.endswith('.'):
name = name[:-1]
sess = Session()
a = sess.dns(name.encode('idna'),'TXT')
if a: return b''.join(a[0])
return None
# Prefer dnspython if it's there, otherwise use pydns.
try:
import dns.resolver
_get_txt = get_txt_dnspython
except ImportError:
try:
import DNS
DNS.DiscoverNameServers()
_get_txt = get_txt_pydns
except:
raise
def get_txt(name, timeout=5):
"""Return a TXT record associated with a DNS name.
@param name: The bytestring domain name to look up.
"""
# pydns needs Unicode, but DKIM's d= is ASCII (already punycoded).
try:
unicode_name = name.decode('UTF-8')
except UnicodeDecodeError:
return None
txt = _get_txt(unicode_name, timeout)
if type(txt) is str:
txt = txt.encode('utf-8')
return txt
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