#!/usr/bin/python2.4
"""
Python CGI script to update the DNS databases via NSUpdate
"""
#Copyright (c) 2006 Erich Schubert erich@debian.org

#Permission is hereby granted, free of charge, to any person obtaining a copy
#of this software and associated documentation files (the "Software"), to deal
#in the Software without restriction, including without limitation the rights
#to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
#copies of the Software, and to permit persons to whom the Software is
#furnished to do so, subject to the following conditions:

#The above copyright notice and this permission notice shall be included in
#all copies or substantial portions of the Software.

#THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
#AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
#LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
#OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
#SOFTWARE.
import os, sys, cgi, re, random, string, subprocess
import kid
# enable debugging
import cgitb; cgitb.enable()

#### CONFIGURATION
zones = [ "0.100.10.in-addr.arpa" ]
ns = "10.0.0.1"
nskey="Kdhcpdkey"

class Digger:
	def __init__(self):
		"""
		Constructor, generate some RE objects
		"""
		self.zonecheck = re.compile(r"^[a-zA-Z0-9_.-]+$")
		self.filter = re.compile(r"^([^\s]+)\s+(\d+)\s+IN\s+(PTR|A|NS|MX|SOA|SRV|CNAME|TXT)\s+([^\s]*)$",re.M)

	def run(self, cmd):
		"""
		Execute a dig command.
		"""
		p = subprocess.Popen(cmd, stdout=subprocess.PIPE)
		return p.communicate()[0]
	
	def stripZone(self, data, zone):
		"""
		Strip the zone itself (likely to be tailed with a trailing dot)
		from the entry, for more compact display.
		"""
		zone = ".%s" % zone
		l = len(zone)
		if data[-l:] == zone:
			return data[:-l]
		if data[-l-1:-1] == zone:
			return data[:-l-1]
		return data

	def getZone(self, zone):
		"""
		Load a specific zone.
		"""
		if not self.zonecheck.match(zone):
			raise Exception, "Zone does not match pattern"
		# fetch the zone
		out = self.run(["dig", "+nostats", "+nocmd", "-t", "AXFR",
			zone, "@%s" % ns])
		results = self.filter.finditer(out)
		list = []
		for match in results:
			e = {
				"name": self.stripZone(match.group(1), zone),
				"time": match.group(2),
				"type": match.group(3),
				"data": match.group(4),
				"maydel": (match.group(3) != "SOA")
			}
			list.append(e)

		def sorter(x,y):
			"""
			Sort IPs by integer when possible...
			Should be a real sort-backwards thing...
			"""
			try:
				return int(x["name"])-int(y["name"])
			except ValueError:
				if x["name"][-1] == ".":
					if y["name"][-1] != ".":
						return -1
				elif y["name"][-1] == ".":
					return +1
				return cmp(x["name"],y["name"])
		list.sort(sorter)
		return list
	
	def addRecord(self, zone, name, time, type, data):
		"""
		Add a new record to DNS
		"""
		# all kinds of safety checks.
		if not self.zonecheck.match(zone):
			raise Exception, "Zone does not match pattern."
		if not self.zonecheck.match(name):
			raise Exception, "Name does not match pattern."
		if not int(time):
			raise Excpetion, "Time value not ok."
		time = int(time)
		if not type in ["A", "TXT", "PTR", "CNAME", "NS", "MX", "SRV"]:
			raise Exception, "Type not allowed."
		if name[-1]==".":
			if name[-len(zone)-1:-1] != zone:
				raise Exception, "Name ends in a dot, "+\
					"but is from a different zone!"
		if ('\\' in data) or ('\n' in data):
			raise Exception, "Double quotes, newlines and "+\
			  " backslashes are not allowed in data part for now!"
		name = self.stripZone(name, zone)
		# run the nsupdate command
		cmd = ["nsupdate", "-k", nskey]
		p = subprocess.Popen(cmd, close_fds=True,
			stdin=subprocess.PIPE,
			stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
		p.stdin.write("server %s\n" % ns)
		p.stdin.write("zone %s\n" % zone)
		p.stdin.write("update add %s.%s. %d %s %s\n" %
			(name, zone, time, type, data))
		p.stdin.write("send\n\n")
		result = p.communicate()[0]
		if result and result != "":
			sys.stderr.write("%s\n" % result)
		return result

	def delRecord(self, zone, name, type):
		"""
		Delete a new record to DNS
		"""
		# all kinds of safety checks.
		if not self.zonecheck.match(zone):
			raise Exception, "Zone does not match pattern."
		if not self.zonecheck.match(name):
			raise Exception, "Name does not match pattern."
		if not type in ["A", "TXT", "PTR", "CNAME", "NS", "MX", "SRV"]:
			raise Exception, "Type not allowed."
		if name[-1]==".":
			if name[-len(zone)-1:-1] != zone:
				raise Exception, "Name ends in a dot, "+\
					"but is from a different zone!"
		name = self.stripZone(name, zone)
		# run the nsupdate command
		cmd = ["nsupdate", "-k", nskey]
		p = subprocess.Popen(cmd, close_fds=True,
			stdin=subprocess.PIPE,
			stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
		p.stdin.write("server %s\n" % ns)
		p.stdin.write("zone %s\n" % zone)
		p.stdin.write("update delete %s.%s. %s\n" %
			(name, zone, type))
		p.stdin.write("send\n\n")
		result = p.communicate()[0]
		if result and result != "":
			sys.stderr.write("%s\n" % result)
		return result

# get CGI variables
form = cgi.FieldStorage()
# load template
tpl = kid.Template(file="template.kid")
zones.sort()
tpl.zones = zones
tpl.result = None
digger = Digger()

if form.has_key("zone"):
	zone = form["zone"].value
	if zone not in zones:
		raise Exception, "Unknown zone specified!"
	if form.has_key("del"):
		tpl.result = digger.delRecord(zone,
		  form.getvalue("name",None),
		  form.getvalue("type",None)
		)
	if form.has_key("add"):
		tpl.result = digger.addRecord(zone,
		  form.getvalue("name",None),
		  form.getvalue("time",None),
		  form.getvalue("type",None),
		  form.getvalue("data",None)
		)
	zonedata = digger.getZone(zone)
	tpl.zone = zone
	tpl.zonedata = zonedata
else:
	tpl.zone = None

# output result
print "Content-Type: text/html\n\n"
print tpl.serialize()