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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
""" Python code to start a RIPE Atlas UDM (User-Defined
Measurement). This one is for running DNS to resolve a name from many
places, in order to survey local cache poisonings, effect of
hijackings and other DNS rejuvenation effects.
You'll need an API key in ~/.atlas/auth.
After launching the measurement, it downloads the results and analyzes
them.
Stéphane Bortzmeyer <stephane+frama@bortzmeyer.org>
"""
import json
import sys
import time
import base64
import copy
import collections
# DNS Python http://www.dnspython.org/
import dns.message
import Blaeu
from Blaeu import Host_Type
config = Blaeu.Config()
# Default values
config.qtype = 'AAAA'
config.qclass = "IN"
config.display_resolvers = False
config.display_rtt = False
config.display_validation = False
config.edns_size = None
config.dnssec = False
config.dnssec_checking = True
config.nameserver = None
config.recursive = True
config.sort = False
config.nsid = False
config.ede = False
config.only_one_per_probe = True
config.protocol = "UDP"
config.tls = False
config.probe_id = False
config.answer_section = True
config.authority_section = False
config.additional_section = False
# Local values
edns_size = None
# Constants
MAXLEN = 80 # Maximum length of a displayed resource record
class Set():
def __init__(self):
self.total = 0
self.successes = 0
self.rtt = 0
def usage(msg=None):
print("Usage: %s domain-name" % sys.argv[0], file=sys.stderr)
config.usage(msg)
print("""Also:
--displayresolvers or -l : display the resolvers IP addresses (WARNING: big lists)
--norecursive or -Z : asks the resolver to NOT recurse (default is to recurse, note --norecursive works ONLY if asking a specific resolver, not with the default one)
--dnssec or -D : asks the resolver the DNSSEC records
--nsid : asks the resolver with NSID (name server identification)
--ede : displays EDE (Extended DNS Errors)
--ednssize=N or -B N : asks for EDNS with the "payload size" option (default is very old DNS, without EDNS)
--tcp: uses TCP (default is UDP)
--tls: uses TLS (implies TCP)
--checkingdisabled or -k : asks the resolver to NOT perform DNSSEC validation
--displayvalidation or -j : displays the DNSSEC validation status
--displayrtt : displays the average RTT
--authority : displays the Authority section of the answer
--additional : displays the Additional section of the answer
--sort or -S : sort the result sets
--type or -q : query type (default is %s)
--class : query class (default is %s)
--severalperprobe : count all the resolvers of each probe (default is to count only the first to reply)
--nameserver=name_or_IPaddr[,...] or -x name_or_IPaddr : query this name server (default is to query the probe's resolver)
--probe_id : prepend probe ID (and timestamp) to the domain name (default is to abstain)
""" % (config.qtype, config.qclass), file=sys.stderr)
def specificParse(config, option, value):
result = True
if option == "--type" or option == "-q":
config.qtype = value
elif option == "--class": # For Chaos, use "CHAOS", not "CH"
config.qclass = value
elif option == "--norecursive" or option == "-Z":
config.recursive = False
elif option == "--dnssec" or option == "-D":
config.dnssec = True
elif option == "--nsid":
config.nsid = True
elif option == "--ede":
config.ede = True
elif option == "--probe_id":
config.probe_id = True
elif option == "--ednssize" or option == "-B":
config.edns_size = int(value)
elif option == "--tcp":
config.protocol = "TCP"
elif option == "--tls":
config.tls = True
elif option == "--checkingdisabled" or option == "-k":
config.dnssec_checking = False
elif option == "--sort" or option == "-S":
config.sort = True
elif option == "--authority":
config.answer_section = False
config.authority_section = True
elif option == "--additional":
config.answer_section = False
config.additional_section = True
elif option == "--nameserver" or option == "-x":
config.nameserver = value
config.nameservers = config.nameserver.split(",")
elif option == "--displayresolvers" or option == "-l":
config.display_resolvers = True
elif option == "--displayvalidation" or option == "-j":
config.display_validation = True
elif option == "--displayrtt":
config.display_rtt = True
elif option == "--severalperprobe":
config.only_one_per_probe = False
else:
result = False
return result
args, data = config.parse("q:ZDkSx:ljB:", ["type=", "class=", "ednssize=",
"displayresolvers", "probe_id",
"displayrtt", "displayvalidation",
"dnssec", "nsid", "ede", "norecursive",
"authority", "additional",
"tcp", "tls", "checkingdisabled",
"nameserver=", "sort",
"severalperprobe"], specificParse,
usage)
if len(args) != 1:
usage()
sys.exit(1)
domainname = args[0]
if config.tls:
config.protocol = "TCP"
# We don't set the port (853) but Atlas does it for us
data["definitions"][0]["type"] = "dns"
del data["definitions"][0]["size"]
del data["definitions"][0]["port"]
data["definitions"][0]["query_argument"] = domainname
data["definitions"][0]["description"] = ("DNS resolution of %s/%s" % (domainname, config.qtype)) + data["definitions"][0]["description"]
data["definitions"][0]["query_class"] = config.qclass
data["definitions"][0]["query_type"] = config.qtype
if config.edns_size is not None and config.protocol == "UDP":
data["definitions"][0]["udp_payload_size"] = config.edns_size
edns_size = config.edns_size
if config.dnssec or config.display_validation: # https://atlas.ripe.net/docs/api/v2/reference/#!/measurements/Dns_Type_Measurement_List_POST
data["definitions"][0]["set_do_bit"] = True
if config.edns_size is None and config.protocol == "UDP":
edns_size = 4096
if config.nsid:
data["definitions"][0]["set_nsid_bit"] = True
if config.edns_size is None and config.protocol == "UDP":
edns_size = 1024
if config.ede:
if config.edns_size is None and config.protocol == "UDP":
edns_size = 1024
if edns_size is not None and config.protocol == "UDP":
data["definitions"][0]["udp_payload_size"] = edns_size
if not config.dnssec_checking:
data["definitions"][0]["set_cd_bit"] = True
if config.recursive:
data["definitions"][0]["set_rd_bit"] = True
else:
data["definitions"][0]["set_rd_bit"] = False
if config.tls:
data["definitions"][0]["tls"] = True
if config.probe_id:
data["definitions"][0]["prepend_probe_id"] = True
data["definitions"][0]["protocol"] = config.protocol
if config.verbose and config.machine_readable:
usage("Specify verbose *or* machine-readable output")
sys.exit(1)
if (config.display_probes or config.display_probe_asns or config.display_resolvers or config.display_rtt) and config.machine_readable:
usage("Display probes/probeasns/resolvers/RTT *or* machine-readable output")
sys.exit(1)
if config.nameserver is None:
config.nameservers = [None,]
description = data["definitions"][0]["description"]
for nameserver in config.nameservers:
if nameserver is None:
data["definitions"][0]["use_probe_resolver"] = True
# Exclude probes which do not have at least one working resolver
data["probes"][0]["tags"]["include"].append("system-resolves-a-correctly")
data["probes"][0]["tags"]["include"].append("system-resolves-aaaa-correctly")
else:
data["definitions"][0]["use_probe_resolver"] = False
data["definitions"][0]["target"] = nameserver
serveraddr_type = Blaeu.host_type(nameserver)
data["definitions"][0]["description"] = description + (" via nameserver %s" % nameserver)
if serveraddr_type == Host_Type.IPv6:
config.ipv4 = False
data["definitions"][0]['af'] = 6
if config.include is not None:
data["probes"][0]["tags"]["include"] = copy.copy(config.include)
data["probes"][0]["tags"]["include"].append("system-ipv6-works")
else:
data["probes"][0]["tags"]["include"] = ["system-ipv6-works",]
elif serveraddr_type == Host_Type.IPv4:
config.ipv4 = True
data["definitions"][0]['af'] = 4
if config.include is not None:
data["probes"][0]["tags"]["include"] = copy.copy(config.include)
data["probes"][0]["tags"]["include"].append("system-ipv4-works")
else:
data["probes"][0]["tags"]["include"] = ["system-ipv4-works",]
else: # Probably an host name
pass
if config.measurement_id is None:
if config.verbose:
print(data)
try:
measurement = Blaeu.Measurement(data,
lambda delay: sys.stderr.write(
"Sleeping %i seconds...\n" % delay))
except Blaeu.RequestSubmissionError as error:
print(Blaeu.format_error(error), file=sys.stderr)
sys.exit(1)
if not config.machine_readable and config.verbose:
print("Measurement #%s for %s/%s uses %i probes" % \
(measurement.id, domainname, config.qtype, measurement.num_probes))
old_measurement = measurement.id
results = measurement.results(wait=True)
else:
measurement = Blaeu.Measurement(data=None, id=config.measurement_id)
results = measurement.results(wait=False)
if config.verbose:
print("%i results from already-done measurement %s" % (len(results), measurement.id))
if len(results) == 0:
print("Warning: zero results. Measurement not terminated? May be retry later with --measurement-ID=%s ?" % (measurement.id), file=sys.stderr)
probes = 0
successes = 0
qtype_num = dns.rdatatype.from_text(config.qtype) # Raises dns.rdatatype.UnknownRdatatype if unknown
sets = collections.defaultdict(Set)
if config.display_probes:
probes_sets = collections.defaultdict(set)
if config.display_probe_asns:
probe_asns_sets = collections.defaultdict(set)
if config.display_resolvers:
resolvers_sets = collections.defaultdict(set)
for result in results:
probes += 1
probe_id = result["prb_id"]
if config.display_probe_asns:
_probe = Blaeu.ProbeCache.cache_probe_id(config.cache_probes, probe_id) if config.cache_probes else Blaeu.Probe(probe_id)
first_error = ""
probe_resolves = False
resolver_responds = False
all_timeout = True
if "result" in result:
result_set = [{'result': result['result']},]
elif "resultset" in result:
result_set = result['resultset']
elif "error" in result:
result_set = []
myset = []
if "timeout" in result['error']:
myset.append("TIMEOUT")
elif "socket" in result['error']:
all_timeout = False
myset.append("NETWORK PROBLEM WITH RESOLVER")
elif "TUCONNECT" in result['error']:
all_timeout = False
myset.append("TUCONNECT (may be a TLS negotiation error or a TCP connection issue)")
else:
all_timeout = False
myset.append("NO RESPONSE FOR UNKNOWN REASON at probe %s" % probe_id)
else:
raise Blaeu.WrongAssumption("Neither result not resultset member")
if len(result_set) == 0:
myset.sort()
set_str = " ".join(myset)
sets[set_str].total += 1
if config.display_probes:
probes_sets[set_str].add(probe_id)
if config.display_probe_asns:
probe_asns_sets[set_str].add(getattr(_probe, "asn_v%i" % (4 if config.ipv4 else 6), None))
for result_i in result_set:
try:
if "dst_addr" in result_i:
resolver = str(result_i['dst_addr'])
elif "dst_name" in result_i: # Apparently, used when there was a problem
resolver = str(result_i['dst_name'])
elif "dst_addr" in result: # Used when specifying a name server
resolver = str(result['dst_addr'])
elif "dst_name" in result: # Apparently, used when there was a problem
resolver = str(result['dst_name'])
else:
resolver = "UNKNOWN RESOLUTION ERROR"
myset = []
if "result" not in result_i:
if config.only_one_per_probe:
continue
else:
if "timeout" in result_i['error']:
myset.append("TIMEOUT")
elif "socket" in result_i['error']:
all_timeout = False
myset.append("NETWORK PROBLEM WITH RESOLVER")
else:
all_timeout = False
myset.append("NO RESPONSE FOR UNKNOWN REASON at probe %s" % probe_id)
else:
all_timeout = False
resolver_responds = True
answer = result_i['result']['abuf'] + "=="
content = base64.b64decode(answer)
msg = dns.message.from_wire(content)
if config.ede:
if hasattr(dns.edns, 'EDE'): # Appeared in DNS Python in 2024?
opt_ede = next((opt for opt in msg.options if opt.otype == dns.edns.EDE), None)
if opt_ede:
ede = opt_ede.to_text()
myset.append(ede)
if config.nsid:
opt_nsid = next((opt for opt in msg.options if opt.otype == dns.edns.NSID), None)
# dnspython handles NSID with version >=
# 2.6. Before that, we have to do it.
if opt_nsid and hasattr(opt_nsid, "data"): # < 2.6
nsid = opt_nsid.data.decode()
elif opt_nsid and hasattr(opt_nsid, "nsid"): # > 2.6
nsid = opt_nsid.to_text()
if nsid.startswith("NSID "):
nsid = nsid[5:] # Remove the "NSID " prefix
else: # NSID option not found or could not be parsed
nsid = None
myset.append("NSID: %s;" % nsid)
successes += 1
if msg.rcode() == dns.rcode.NOERROR:
probe_resolves = True
if config.answer_section:
if result_i['result']['ANCOUNT'] == 0 and config.verbose:
# If we test an authoritative server, and it returns a delegation, we won't see anything...
print("Warning: reply at probe %s has no answers: may be the server returned a delegation, or does not have data of type %s? For the first case, you may want to use --authority." % (probe_id, config.qtype), file=sys.stderr)
interesting_section = msg.answer
elif config.authority_section:
interesting_section = msg.authority
elif config.additional_section:
interesting_section = msg.additional
for rrset in interesting_section:
for rdata in rrset:
if rdata.rdtype == qtype_num:
myset.append(str(rdata)[0:MAXLEN].lower()) # We truncate because DNSKEY can be very long
if config.display_validation and (msg.flags & dns.flags.AD):
myset.append(" (Authentic Data flag) ")
if (msg.flags & dns.flags.TC):
if edns_size is not None:
myset.append(" (TRUNCATED - EDNS buffer size was %d ) " % edns_size)
else:
myset.append(" (TRUNCATED - May have to use --ednssize) ")
else:
if msg.rcode() == dns.rcode.REFUSED: # Not SERVFAIL since
# it can be legitimate (DNSSEC problem, for instance)
if config.only_one_per_probe and len(result_set) > 1: # It
# does not handle the case where there
# are several resolvers and all say
# REFUSED (probably a rare case).
if first_error == "":
first_error = "ERROR: %s" % dns.rcode.to_text(msg.rcode())
continue # Try again
else:
probe_resolves = True # NXDOMAIN or SERVFAIL are legitimate
myset.append("ERROR: %s" % dns.rcode.to_text(msg.rcode()))
myset.sort() # Not ideal since the alphabetical sort
# will, for instance, put EDE before
# ERROR. We should create myset more
# intelligently.
set_str = " ".join(myset)
sets[set_str].total += 1
if "error" not in result_i:
sets[set_str].successes += 1
if config.display_probes:
probes_sets[set_str].add(probe_id)
if config.display_probe_asns:
_res_af = result_i.get("af") or result.get("af")
if _res_af:
probe_asns_sets[set_str].add(getattr(_probe, "asn_v%i" % _res_af))
if config.display_resolvers:
resolvers_sets[set_str].add(resolver)
if config.display_rtt:
if "error" not in result_i:
if "result" not in result_i:
sets[set_str].rtt += result_i['rt']
else:
sets[set_str].rtt += result_i['result']['rt']
except dns.name.BadLabelType:
if not config.machine_readable:
print("Probe %s failed (bad label in name)" % probe_id, file=sys.stderr)
except dns.message.TrailingJunk:
if not config.machine_readable:
print("Probe %s failed (trailing junk)" % probe_id, file=sys.stderr)
except dns.exception.FormError:
if not config.machine_readable:
print("Probe %s failed (malformed DNS message)" % probe_id, file=sys.stderr)
if config.only_one_per_probe:
break
if not probe_resolves and first_error != "" and config.verbose:
print("Warning, probe %s has no working resolver (first error is \"%s\")" % (probe_id, first_error), file=sys.stderr)
if not resolver_responds:
if all_timeout and not config.only_one_per_probe:
if config.verbose:
print("Warning, probe %s never got reply from any resolver" % (probe_id), file=sys.stderr)
set_str = "TIMEOUT(S) on all resolvers"
sets[set_str].total += 1
else:
myset.sort()
set_str = " ".join(myset)
if config.sort:
sets_data = sorted(sets, key=lambda s: sets[s].total, reverse=True)
else:
sets_data = sets
details = []
if not config.machine_readable and config.nameserver is not None:
print("Nameserver %s" % nameserver)
if not config.answer_section:
if config.authority_section:
print("Authority section of the DNS responses")
elif config.additional_section:
print("Additional section of the DNS responses")
else:
print("INTERNAL PROBLEM: no section to display?")
for myset in sets_data:
detail = ""
if config.display_probes:
detail = "(probes %s)" % probes_sets[myset]
if config.display_probe_asns:
detail = "(probe asns %s)" % probe_asns_sets[myset]
if config.display_resolvers:
detail += "(resolvers %s)" % resolvers_sets[myset]
if config.display_rtt and sets[myset].successes > 0:
detail += "Average RTT %i ms" % (sets[myset].rtt/sets[myset].successes)
if not config.machine_readable:
print("[%s] : %i occurrences %s" % (myset, sets[myset].total, detail))
else:
details.append("[%s];%i" % (myset, sets[myset].total))
if not config.machine_readable:
print(("Test #%s done at %s" % (measurement.id, time.strftime("%Y-%m-%dT%H:%M:%SZ", measurement.time))))
print("")
else:
if config.nameserver is None:
ns = "DEFAULT RESOLVER"
else:
ns = config.nameserver
print(",".join([domainname, config.qtype, str(measurement.id), "%s/%s" % (len(results), measurement.num_probes), \
time.strftime("%Y-%m-%dT%H:%M:%SZ", measurement.time), ns] + details))
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