summaryrefslogtreecommitdiff
path: root/source4/scripting/bin/samba_dnsupdate
blob: b295224ddc67f561d0ce2be706f3a6a9715feb82 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
#!/usr/bin/env python
#
# update our DNS names using TSIG-GSS
#
# Copyright (C) Andrew Tridgell 2010
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.


import os
import fcntl
import sys
import tempfile

# ensure we get messages out immediately, so they get in the samba logs,
# and don't get swallowed by a timeout
os.putenv('PYTHONUNBUFFERED', '1')

# Find right directory when running from source tree
sys.path.insert(0, "bin/python")

import samba
import optparse
from samba import getopt as options
from ldb import SCOPE_BASE
from samba.auth import system_session
from samba.samdb import SamDB

samba.ensure_external_module("dns", "dnspython")
import dns.resolver as resolver

default_ttl = 900

parser = optparse.OptionParser("samba_dnsupdate")
sambaopts = options.SambaOptions(parser)
parser.add_option_group(sambaopts)
parser.add_option_group(options.VersionOptions(parser))
parser.add_option("--verbose", action="store_true")
parser.add_option("--all-interfaces", action="store_true")
parser.add_option("--use-file", type="string", help="Use a file, rather than real DNS calls")

creds = None
ccachename = None

opts, args = parser.parse_args()

if len(args) != 0:
    parser.print_usage()
    sys.exit(1)

lp = sambaopts.get_loadparm()

domain = lp.get("realm")
host = lp.get("netbios name")
if opts.all_interfaces:
    all_interfaces = True
else:
    all_interfaces = False

IPs = samba.interface_ips(lp, all_interfaces)
nsupdate_cmd = lp.get('nsupdate command')

if len(IPs) == 0:
    print "No IP interfaces - skipping DNS updates"
    sys.exit(0)



########################################################
# get credentials if we haven't got them already
def get_credentials(lp):
    from samba import credentials
    global ccachename, creds
    if creds is not None:
        return
    creds = credentials.Credentials()
    creds.guess(lp)
    creds.set_machine_account(lp)
    creds.set_krb_forwardable(credentials.NO_KRB_FORWARDABLE)
    (tmp_fd, ccachename) = tempfile.mkstemp()
    creds.get_named_ccache(lp, ccachename)


#############################################
# an object to hold a parsed DNS line
class dnsobj(object):
    def __init__(self, string_form):
        list = string_form.split()
        self.dest = None
        self.port = None
        self.ip = None
        self.existing_port = None
        self.existing_weight = None
        self.type = list[0]
        self.name = list[1]
        if self.type == 'SRV':
            self.dest = list[2]
            self.port = list[3]
        elif self.type == 'A':
            self.ip   = list[2] # usually $IP, which gets replaced
        elif self.type == 'CNAME':
            self.dest = list[2]
        else:
            print "Received unexpected DNS reply of type %s" % self.type
            raise

    def __str__(self):
        if d.type == "A":     return "%s %s %s" % (self.type, self.name, self.ip)
        if d.type == "SRV":   return "%s %s %s %s" % (self.type, self.name, self.dest, self.port)
        if d.type == "CNAME": return "%s %s %s" % (self.type, self.name, self.dest)


################################################
# parse a DNS line from
def parse_dns_line(line, sub_vars):
    subline = samba.substitute_var(line, sub_vars)
    d = dnsobj(subline)
    return d

############################################
# see if two hostnames match
def hostname_match(h1, h2):
    h1 = str(h1)
    h2 = str(h2)
    return h1.lower().rstrip('.') == h2.lower().rstrip('.')


############################################
# check that a DNS entry exists
def check_dns_name(d):
    normalised_name = d.name.rstrip('.') + '.'
    if opts.verbose:
        print "Looking for DNS entry %s as %s" % (d, normalised_name)
 
    if opts.use_file is not None:
        try:
            dns_file = open(opts.use_file, "r")
        except IOError:
            return False
        
        for line in dns_file:
            line = line.strip()
            if line == '' or line[0] == "#":
                continue
            if line.lower() == str(d).lower():
                return True
        return False

    try:
        ans = resolver.query(normalised_name, d.type)
    except resolver.NXDOMAIN:
        return False
    if d.type == 'A':
        # we need to be sure that our IP is there
        for rdata in ans:
            if str(rdata) == str(d.ip):
                return True
    if d.type == 'CNAME':
        for i in range(len(ans)):
            if hostname_match(ans[i].target, d.dest):
                return True
    if d.type == 'SRV':
        for rdata in ans:
            if opts.verbose:
                print "Checking %s against %s" % (rdata, d)
            if hostname_match(rdata.target, d.dest):
                if str(rdata.port) == str(d.port):
                    return True
                else:
                    d.existing_port     = str(rdata.port)
                    d.existing_weight = str(rdata.weight)
    if opts.verbose:
        print "Failed to find DNS entry %s" % d

    return False


###########################################
# get the list of substitution vars
def get_subst_vars():
    global lp
    vars = {}

    samdb = SamDB(url=lp.get("sam database"), session_info=system_session(),
                  lp=lp)

    vars['DNSDOMAIN'] = lp.get('realm').lower()
    vars['HOSTNAME']  = lp.get('netbios name').lower() + "." + vars['DNSDOMAIN']
    vars['NTDSGUID']  = samdb.get_ntds_GUID()
    vars['SITE']      = samdb.server_site_name()
    res = samdb.search(base=None, scope=SCOPE_BASE, attrs=["objectGUID"])
    guid = samdb.schema_format_value("objectGUID", res[0]['objectGUID'][0])
    vars['DOMAINGUID'] = guid
    return vars


############################################
# call nsupdate for an entry
def call_nsupdate(d):
    global ccachename, nsupdate_cmd

    if opts.verbose:
        print "Calling nsupdate for %s" % d

    if opts.use_file is not None:
        wfile = open(opts.use_file, 'a')
        fcntl.lockf(wfile, fcntl.LOCK_EX)
        wfile.write(str(d)+"\n")
        fcntl.lockf(wfile, fcntl.LOCK_UN)
        return

    (tmp_fd, tmpfile) = tempfile.mkstemp()
    f = os.fdopen(tmp_fd, 'w')
    if d.type == "A":
        f.write("update add %s %u A %s\n" % (d.name, default_ttl, d.ip))
    if d.type == "SRV":
        if d.existing_port is not None:
            f.write("update delete %s SRV 0 %s %s %s\n" % (d.name, d.existing_weight,
                                                           d.existing_port, d.dest))
        f.write("update add %s %u SRV 0 100 %s %s\n" % (d.name, default_ttl, d.port, d.dest))
    if d.type == "CNAME":
        f.write("update add %s %u CNAME %s\n" % (d.name, default_ttl, d.dest))
    if opts.verbose:
        f.write("show\n")
    f.write("send\n")
    f.close()

    os.putenv("KRB5CCNAME", ccachename)
    os.system("%s %s" % (nsupdate_cmd, tmpfile))
    os.unlink(tmpfile)


# get the list of DNS entries we should have
dns_update_list = lp.private_path('dns_update_list')

file = open(dns_update_list, "r")

# get the substitution dictionary
sub_vars = get_subst_vars()

# build up a list of update commands to pass to nsupdate
update_list = []
dns_list = []

# read each line, and check that the DNS name exists
for line in file:
    line = line.strip()
    if line == '' or line[0] == "#":
        continue
    d = parse_dns_line(line, sub_vars)
    dns_list.append(d)

# now expand the entries, if any are A record with ip set to $IP
# then replace with multiple entries, one for each interface IP
for d in dns_list:
    if d.type == 'A' and d.ip == "$IP":
        d.ip = IPs[0]
        for i in range(len(IPs)-1):
            d2 = d
            d2.ip = IPs[i+1]
            dns_list.append(d2)

# now check if the entries already exist on the DNS server
for d in dns_list:
    if not check_dns_name(d):
        update_list.append(d)

if len(update_list) == 0:
    if opts.verbose:
        print "No DNS updates needed"
    sys.exit(0)

# get our krb5 creds
get_credentials(lp)

# ask nsupdate to add entries as needed
for d in update_list:
    call_nsupdate(d)

# delete the ccache if we created it
if ccachename is not None:
    os.unlink(ccachename)