dnssec.py (5983B)
1 #!/usr/bin/env python 2 # 3 # Electrum - lightweight Bitcoin client 4 # Copyright (C) 2015 Thomas Voegtlin 5 # 6 # Permission is hereby granted, free of charge, to any person 7 # obtaining a copy of this software and associated documentation files 8 # (the "Software"), to deal in the Software without restriction, 9 # including without limitation the rights to use, copy, modify, merge, 10 # publish, distribute, sublicense, and/or sell copies of the Software, 11 # and to permit persons to whom the Software is furnished to do so, 12 # subject to the following conditions: 13 # 14 # The above copyright notice and this permission notice shall be 15 # included in all copies or substantial portions of the Software. 16 # 17 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 18 # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 19 # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 20 # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 21 # BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 22 # ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 23 # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 24 # SOFTWARE. 25 26 # Check DNSSEC trust chain. 27 # Todo: verify expiration dates 28 # 29 # Based on 30 # http://backreference.org/2010/11/17/dnssec-verification-with-dig/ 31 # https://github.com/rthalley/dnspython/blob/master/tests/test_dnssec.py 32 33 34 # import traceback 35 # import sys 36 import time 37 import struct 38 import hashlib 39 40 41 import dns.name 42 import dns.query 43 import dns.dnssec 44 import dns.message 45 import dns.resolver 46 import dns.rdatatype 47 import dns.rdtypes.ANY.NS 48 import dns.rdtypes.ANY.CNAME 49 import dns.rdtypes.ANY.DLV 50 import dns.rdtypes.ANY.DNSKEY 51 import dns.rdtypes.ANY.DS 52 import dns.rdtypes.ANY.NSEC 53 import dns.rdtypes.ANY.NSEC3 54 import dns.rdtypes.ANY.NSEC3PARAM 55 import dns.rdtypes.ANY.RRSIG 56 import dns.rdtypes.ANY.SOA 57 import dns.rdtypes.ANY.TXT 58 import dns.rdtypes.IN.A 59 import dns.rdtypes.IN.AAAA 60 61 from .logging import get_logger 62 63 64 _logger = get_logger(__name__) 65 66 67 # hard-coded trust anchors (root KSKs) 68 trust_anchors = [ 69 # KSK-2017: 70 dns.rrset.from_text('.', 1 , 'IN', 'DNSKEY', '257 3 8 AwEAAaz/tAm8yTn4Mfeh5eyI96WSVexTBAvkMgJzkKTOiW1vkIbzxeF3+/4RgWOq7HrxRixHlFlExOLAJr5emLvN7SWXgnLh4+B5xQlNVz8Og8kvArMtNROxVQuCaSnIDdD5LKyWbRd2n9WGe2R8PzgCmr3EgVLrjyBxWezF0jLHwVN8efS3rCj/EWgvIWgb9tarpVUDK/b58Da+sqqls3eNbuv7pr+eoZG+SrDK6nWeL3c6H5Apxz7LjVc1uTIdsIXxuOLYA4/ilBmSVIzuDWfdRUfhHdY6+cn8HFRm+2hM8AnXGXws9555KrUB5qihylGa8subX2Nn6UwNR1AkUTV74bU='), 71 # KSK-2010: 72 dns.rrset.from_text('.', 15202, 'IN', 'DNSKEY', '257 3 8 AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq QxA+Uk1ihz0='), 73 ] 74 75 76 def check_query(ns, sub, _type, keys): 77 q = dns.message.make_query(sub, _type, want_dnssec=True) 78 response = dns.query.tcp(q, ns, timeout=5) 79 assert response.rcode() == 0, 'No answer' 80 answer = response.answer 81 assert len(answer) != 0, ('No DNS record found', sub, _type) 82 assert len(answer) != 1, ('No DNSSEC record found', sub, _type) 83 if answer[0].rdtype == dns.rdatatype.RRSIG: 84 rrsig, rrset = answer 85 elif answer[1].rdtype == dns.rdatatype.RRSIG: 86 rrset, rrsig = answer 87 else: 88 raise Exception('No signature set in record') 89 if keys is None: 90 keys = {dns.name.from_text(sub):rrset} 91 dns.dnssec.validate(rrset, rrsig, keys) 92 return rrset 93 94 95 def get_and_validate(ns, url, _type): 96 # get trusted root key 97 root_rrset = None 98 for dnskey_rr in trust_anchors: 99 try: 100 # Check if there is a valid signature for the root dnskey 101 root_rrset = check_query(ns, '', dns.rdatatype.DNSKEY, {dns.name.root: dnskey_rr}) 102 break 103 except dns.dnssec.ValidationFailure: 104 # It's OK as long as one key validates 105 continue 106 if not root_rrset: 107 raise dns.dnssec.ValidationFailure('None of the trust anchors found in DNS') 108 keys = {dns.name.root: root_rrset} 109 # top-down verification 110 parts = url.split('.') 111 for i in range(len(parts), 0, -1): 112 sub = '.'.join(parts[i-1:]) 113 name = dns.name.from_text(sub) 114 # If server is authoritative, don't fetch DNSKEY 115 query = dns.message.make_query(sub, dns.rdatatype.NS) 116 response = dns.query.udp(query, ns, 3) 117 assert response.rcode() == dns.rcode.NOERROR, "query error" 118 rrset = response.authority[0] if len(response.authority) > 0 else response.answer[0] 119 rr = rrset[0] 120 if rr.rdtype == dns.rdatatype.SOA: 121 continue 122 # get DNSKEY (self-signed) 123 rrset = check_query(ns, sub, dns.rdatatype.DNSKEY, None) 124 # get DS (signed by parent) 125 ds_rrset = check_query(ns, sub, dns.rdatatype.DS, keys) 126 # verify that a signed DS validates DNSKEY 127 for ds in ds_rrset: 128 for dnskey in rrset: 129 htype = 'SHA256' if ds.digest_type == 2 else 'SHA1' 130 good_ds = dns.dnssec.make_ds(name, dnskey, htype) 131 if ds == good_ds: 132 break 133 else: 134 continue 135 break 136 else: 137 raise Exception("DS does not match DNSKEY") 138 # set key for next iteration 139 keys = {name: rrset} 140 # get TXT record (signed by zone) 141 rrset = check_query(ns, url, _type, keys) 142 return rrset 143 144 145 def query(url, rtype): 146 # 8.8.8.8 is Google's public DNS server 147 nameservers = ['8.8.8.8'] 148 ns = nameservers[0] 149 try: 150 out = get_and_validate(ns, url, rtype) 151 validated = True 152 except BaseException as e: 153 _logger.info(f"DNSSEC error: {repr(e)}") 154 out = dns.resolver.resolve(url, rtype) 155 validated = False 156 return out, validated