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…

dnsupdate.py

#!/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()

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 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 :)

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

Guys;
I am running the script on Centos 7.5 and got the error:
[root@nsserver1 zague]# ./dnsupdate.py -s nsserver1.kpt.com.mx -k /var/named/data/Kkpt.com.mx.+157+56738.key delete mail.kpt.com.mx. IN A Traceback (most recent call last): File "./dnsupdate.py", line 290, in <module> main() File "./dnsupdate.py", line 288, in main doUpdate(myArgs.Server, myArgs.Key, myArgs.Origin, myArgs.TimeToLive, myArgs.doPTR, myArgs.myInput) File "./dnsupdate.py", line 223, in doUpdate KeyRing, KeyAlgo = getKey(KeyFile) File "./dnsupdate.py", line 176, in getKey algo = keyfile[1].rsplit(' ')[1].replace(';','').replace('-','_').upper().strip() IndexError: list index out of range

Any Ideas

@ryanczak and @epleterte, thanks.

For those interested, the related blog post is archived at:

https://web.archive.org/web/20130322064416/http://planetfoo.org/blog/archive/2012/01/24/a-better-nsupdate/

Just wondering whether it works today as @vazquc reported above at https://gist.github.com/pklaus/4619865#gistcomment-2766052?!

Season's greetings and cheers,
/z

Hi,

Tried to use, but getting following error, no matter whether I specify -t flag or not:

$ python3 dnsupdate.py -s ns2.mydomain.net -k Kns2.mydomain.net.+165+00940.key add test.myzone.com 3600 A xx.yy.zz.abc
  File "dnsupdate.py", line 68
    print 'TTL:', TTL, 'is not valid'
               ^
SyntaxError: Missing parentheses in call to 'print'

Any input?

Cheers,
/z

@ryanczak and @epleterte, thanks.

For those interested, the related blog post is archived at:

https://web.archive.org/web/20130322064416/http://planetfoo.org/blog/archive/2012/01/24/a-better-nsupdate/

Just wondering whether it works today as @vazquc reported above at https://gist.github.com/pklaus/4619865#gistcomment-2766052?!

Season's greetings and cheers,
/z

I was not able to fix the error, fortunately I found this other script https://gist.github.com/4707775 and it's working perfectly.
Regards