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dnsupdate is meant to replace nsupdate, the standard DDNS update tool created by BIND authors ISC. While nsupdate does the job it is awkward to wrap in scripts and its usage in general is just not very intuitive. dnsupdate is meant to work well from the command line or from scripts and easy to use. It also does some nice things like automaticall…
#!/usr/bin/env python2.7
# Matt's DNS management tool
# Manage DNS using DDNS features
#
# See http://planetfoo.org/blog/archive/2012/01/24/a-better-nsupdate/
#
# Usage: dnsupdate -s server -k key -t ttl add _minecraft._tcp.mc.example.com SRV 0 0 25566 mc.example.com.
# -h HELP!
# -s the server
# -k the key
# -t the ttl
# the action (add, delete, replace) and record specific parameters
import argparse
import textwrap
import re
import dns.query
import dns.tsigkeyring
import dns.update
import dns.reversename
import dns.resolver
from dns.exception import DNSException, SyntaxError
Verbose = False
#
# Let's use argparser!
def getArgs():
# Setup a argument parser to collect the values we need
Args = argparse.ArgumentParser(usage='%(prog)s [-h] {-s} {-k} {-o} [-x] {add|delete|update} {Name} {TTL} [IN] {Type} {Target}', description='Add, Delete, Replace DNS records using DDNS.')
# -s - The Server
Args.add_argument('-s', dest='Server', required=True,
help='DNS server to update (Required)')
# -k - The Key
Args.add_argument('-k', dest='Key', required=True,
help='TSIG key. The TSIG key file should be in DNS KEY record format. (Required)')
# -o - The Origin
Args.add_argument('-o', dest='Origin', required=False,
help='Specify the origin. Optional, if not provided origin will be determined')
# -x - Add Reverse?
Args.add_argument('-x', dest='doPTR', action='store_true',
help='Also modify the PTR for a given A or AAAA record. Forward and reverse zones must be on the same server.')
# -v - Verbose?
Args.add_argument('-v', dest='Verbose', action='store_true',
help='Print the rcode returned with for each update')
# -t - The TTL
Args.add_argument('-t', dest='TimeToLive', required=False, default="600",
help='Specify the TTL. Optional, if not provided TTL will be default to 600.')
# myInput is a list of additional values required. Actual data varies based on action
Args.add_argument('myInput', action='store', nargs='+', metavar='add|delete|update',
help='{hostname} [IN] {Type} {Target}.')
myArgs = Args.parse_args()
return myArgs
#
# Is a valid TTL?
def isValidTTL(TTL):
try:
TTL = dns.ttl.from_text(TTL)
except:
print 'TTL:', TTL, 'is not valid'
exit()
return TTL
#
# Is a Valid PTR?
def isValidPTR(ptr):
if re.match(r'\b(?:\d{1,3}\.){3}\d{1,3}.in-addr.arpa\b', ptr):
return True
else:
print 'Error:', ptr, 'is not a valid PTR record'
exit()
#
# Is a valid IPV4 address?
def isValidV4Addr(Address):
try:
dns.ipv4.inet_aton(Address)
except socket.error:
print 'Error:', Address, 'is not a valid IPv4 address'
exit()
return True
#
# Is a valid IPv6 address?
def isValidV6Addr(Address):
try:
dns.ipv6.inet_aton(Address)
except SyntaxError:
print 'Error:', Address, 'is not a valid IPv6 address'
exit()
return True
def isValidName(Name):
if re.match(r'^(([a-zA-Z0-9]|[a-zA-Z0-9\_][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z]|[A-Za-z][A-Za-z0-9\-]*[A-Za-z0-9]\.?)$', Name):
return True
else:
print 'Error:', Name, 'is not a valid name'
exit()
def verifymyInput(myInput):
# Validate the host and domain name syntax
# We're going to make sure that the action and arguments in myInput are valid
action = myInput[0].lower()
if action != 'add' and action != 'delete' and action != 'del' and action != 'update':
print 'FATAL: Invalid action'
print 'Usage: dnsupdate [-o origin] -s server -k key [-t ttl] [add|delete|update] [Name] [Type] [Address]'
exit()
if action == 'delete' or action == 'del': # skip type checks
return 'del', None # Bail out early
# We need to know type in order to do some tests so we'll define it here
type = myInput[2].upper()
# Based on the type of record we're trying to update we'll run some tests
if type == 'A' or type == 'AAAA':
if len(myInput) < 4:
print 'FATAL: not enough options for an A record'
print 'Usage: dnsupdate -o origin -s server -k key [-t ttl] add|delete|update Name A Address'
exit()
isValidName(myInput[1])
if type == 'A':
isValidV4Addr(myInput[3])
elif type == 'AAAA':
isValidV6Addr(myInput[3])
if type == 'CNAME' or type == 'NS':
if len(myInput) < 4:
print 'FATAL: not enough options for a CNAME record'
print 'Usage: dnsupdate -o origin -s server -k key [-t ttl] add|delete|update Name CNAME Target'
exit()
isValidName(myInput[1])
isValidName(myInput[3])
if type == 'PTR':
if len(myInput) < 4:
print 'Error: not enough options for a PTR record'
print 'Usage: dnsupdate -o origin -s server -k key [-t ttl] add|delete|update Name PTR Target'
exit()
# isValidPTR(myInput[1])
isValidName(myInput[3])
if type == 'TXT':
# Wrap the TXT string in quotes since the quotes get stripped
myInput[3] = '"%s"' % myInput[3]
if type == 'MX':
if len(myInput) < 4:
print 'Error: not enough options for an MX record'
print 'Usage: dnsupdate -o origin -s server -k key [-t ttl] add|delete|update Name MX Weight Target'
if int(myInput[3]) > 65535 or int(myInput[3]) < 0:
print 'Error: Preference must be between 0 - 65535'
exit()
isValidName(myInput[1])
isValidName(myInput[5])
if type == 'SRV':
if len(myInput) < 6:
print 'Error: not enough options for a SRV record'
print 'Usage: dnsupdate -o origin -s server -k key [-t ttl] add|delete|update Name SRV Priority Weight Port Target'
if int(myInput[3]) > 65535 or int(myInput[3]) < 0:
print 'Error: Priority must be between 0 - 65535'
exit()
if int(myInput[4]) > 65535 or int(myInput[4]) < 0:
print 'Error: Weight must be between 0 - 65535'
exit()
if int(myInput[5]) > 65535 or int(myInput[5]) < 0:
print 'Error: Port must be between 0 - 65535'
exit()
isValidName(myInput[1])
isValidName(myInput[6])
return action, type
def getKey(FileName):
f = open(FileName)
keyfile = f.read().splitlines() # Fixed by Kamilion 7/7/13
f.close()
hostname = keyfile[0].rsplit(' ')[1].replace('"', '').strip()
algo = keyfile[1].rsplit(' ')[1].replace(';','').replace('-','_').upper().strip()
key = keyfile[2].rsplit(' ')[1].replace('}','').replace(';','').replace('"', '').strip()
k = {hostname:key}
try:
KeyRing = dns.tsigkeyring.from_text(k)
except:
print k, 'is not a valid key. The file should be in DNS KEY record format. See dnssec-keygen(8)'
exit()
return [KeyRing, algo]
def genPTR(Address):
try:
a = dns.reversename.from_address(Address)
except:
print 'Error:', Address, 'is not a valid IP adresss'
return a
def parseName(Origin, Name):
try:
n = dns.name.from_text(Name)
except:
print 'Error:', n, 'is not a valid name'
exit()
if Origin is None:
Origin = dns.resolver.zone_for_name(n)
Name = n.relativize(Origin)
return Origin, Name
else:
try:
Origin = dns.name.from_text(Origin)
except:
print 'Error:', Name, 'is not a valid origin'
exit()
Name = n - Origin
return Origin, Name
def doUpdate(Server, KeyFile, Origin, TimeToLive, doPTR, myInput):
# if the Class is defined (e.g. IN) strip it out
if len(myInput) > 2 and myInput[2].upper() == 'IN':
myInput.pop(2)
# Sanity check the data and get the action and record type
Action, Type = verifymyInput(myInput)
TTL = isValidTTL(TimeToLive)
# Get the hostname and the origin
Origin, Name = parseName(Origin, myInput[1])
# Validate and setup the Key
KeyRing, KeyAlgo = getKey(KeyFile)
# Start constructing the DDNS Query
Update = dns.update.Update(Origin, keyring=KeyRing, keyalgorithm=getattr(dns.tsig, KeyAlgo)) # fixed by Kamilion 7/7/13
# Put the payload together.
myPayload = '' # Start with an empty payload.
if Type == 'A' or Type == 'AAAA':
myPayload = myInput[3]
if doPTR == True:
ptrTarget = Name.to_text() + '.' + Origin.to_text()
ptrOrigin, ptrName = parseName(None, genPTR(myPayload).to_text())
ptrUpdate = dns.update.Update(ptrOrigin, keyring=KeyRing)
if Action != 'del' and Type == 'CNAME' or Type == 'NS' or Type == 'TXT' or Type == 'PTR':
myPayload = myInput[3]
do_PTR = False
elif Type == 'SRV':
myPayload = myInput[3]+' '+myInput[4]+' '+myInput[5]+' '+myInput[6]
do_PTR = False
elif Type == 'MX':
myPayload = myInput[3]+' '+myInput[4]
do_PTR = False
# Build the update
if Action == 'add':
Update.add(Name, TTL, Type, myPayload)
if doPTR == True:
ptrUpdate.add(ptrName, TTL, 'PTR', ptrTarget)
elif Action == 'delete' or Action == 'del':
if myPayload != '':
Update.delete(Name, Type, myPayload)
else:
Update.delete(Name)
if doPTR == True:
ptrUpdate.delete(ptrName, 'PTR', ptrTarget)
elif Action == 'update':
Update.replace(Name, TTL, Type, myPayload)
if doPTR == True:
ptrUpdate.replace(ptrName, TTL, 'PTR', ptrTarget)
# Do the update
try:
Response = dns.query.tcp(Update, Server)
except dns.tsig.PeerBadKey:
print 'ERROR: The server is refusing our key'
exit()
except dns.tsig.PeerBadSignature:
print 'ERROR: Something is wrong with the signature of the key'
exit()
if Verbose == True:
print 'Manipulating', Type, 'record for', Name, 'resulted in:', dns.rcode.to_text(Response.rcode())
if doPTR == True:
try:
ptrResponse = dns.query.tcp(ptrUpdate, Server)
except dns.tsig.PeerBadKey:
print 'ERROR: The server is refusing our key'
exit()
except dns.tsig.PeerBadSignature:
print 'ERROR: Something is wrong with the signature of the key'
exit()
if Verbose == True:
print 'Creating PTR record for', Name, 'resulted in:', dns.rcode.to_text(Response.rcode())
#print 'completed.'
def main():
myArgs = getArgs()
global Verbose
if myArgs.Verbose == True:
Verbose = True
doUpdate(myArgs.Server, myArgs.Key, myArgs.Origin, myArgs.TimeToLive, myArgs.doPTR, myArgs.myInput)
main()
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ryanczak Feb 9, 2016

Funny to see this here. I guess it came from my old blog? Happy to see that it is useful to someone. Perhaps I should commit some of my other scripts to github....

ryanczak commented Feb 9, 2016

Funny to see this here. I guess it came from my old blog? Happy to see that it is useful to someone. Perhaps I should commit some of my other scripts to github....

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epleterte Mar 4, 2016

@ryanczak If your blog post used to live at http://planetfoo.org/blog/archive/2012/01/24/a-better-nsupdate/ it's mentioned in the header of the script, but I am getting 'connection refused' from that site.
Anyway, thanks y'all - I'll see if I can make use of this :)

@ryanczak If your blog post used to live at http://planetfoo.org/blog/archive/2012/01/24/a-better-nsupdate/ it's mentioned in the header of the script, but I am getting 'connection refused' from that site.
Anyway, thanks y'all - I'll see if I can make use of this :)

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ryanczak Jun 1, 2016

My blog died from neglect :) Something lives on though so 👍

ryanczak commented Jun 1, 2016

My blog died from neglect :) Something lives on though so 👍

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