cgi-bin/tdyndns.py

   1 #!/usr/bin/python2.7
   2 """Dynamic DNS script. Expects URLs from routers in the form
   3 http://dyndns.colgarra.priv.at/nic/update?username=<username>&password=<pass>&hostname=<domain>&myip=<ipaddr>
   4 """
   5 import os
   6 import re
   7 import cgi
   8 import pwd
   9 import base64
  10 from subprocess import call
  11 import ipaddr
  12
  13
  14 # Configuration
  15 PASSWORD = 'hygCithOrs5'
  16 DEBUG = False
  17
  18
  19 # Just for debugging:
  20 if DEBUG:
  21         import cgitb
  22         cgitb.enable()
  23
  24
  25 # Base class for our exceptions
  26 class DynDnsError(Exception):
  27         pass
  28
  29 class AuthError(DynDnsError):
  30         returncode = 'badauth'
  31
  32 class CredentialsMissing(AuthError):
  33         pass
  34
  35 class UsernameMissing(AuthError):
  36         pass
  37
  38 class UsernameInvalid(AuthError):
  39         pass
  40
  41 class PasswordMissing(AuthError):
  42         pass
  43
  44 class PasswordWrong(AuthError):
  45         pass
  46
  47 class AuthWrongMethod(AuthError):
  48         returncode = 'wrongauthmethod' # not documented at dyn.com
  49
  50 class AuthBasicError(AuthError):
  51         returncode = 'authbasicerror' # not documented at dyn.com
  52
  53 class HostnameError(DynDnsError):
  54         returncode = 'notfqdn'
  55
  56 class HostnameMissing(HostnameError):
  57         pass
  58
  59 class PasswordWrong(HostnameError):
  60         pass
  61
  62 class MyipError(DynDnsError):
  63         returncode = 'badip' # not documented at dyn.com
  64
  65 class MyipMissing(MyipError):
  66         pass
  67
  68 class MyipInvalid(MyipError):
  69         pass
  70
  71 class OfflineInvalid(DynDnsError):
  72         returncode = 'badparam' # not documented at dyn.com
  73
  74 class NsupdateError(DynDnsError):
  75         returncode = 'nohost'
  76
  77
  78 fields = cgi.FieldStorage()
  79
  80 # the following fields are supported by most dyndns providers
  81 # if a parameter is not provided, the .getvalue method returns None
  82 username = fields.getvalue('username')
  83 password = fields.getvalue('password')
  84 hostname = fields.getvalue('hostname')
  85 myip     = fields.getvalue('myip')
  86 wildcard = fields.getvalue('wildcard')
  87 mx       = fields.getvalue('mx')
  88 backmx   = fields.getvalue('backmx')
  89 offline  = fields.getvalue('offline')
  90 system   = fields.getvalue('system')
  91 url      = fields.getvalue('url')
  92
  93
  94 try:
  95         # Optional Auth Basic
  96         auth = os.environ.get('HTTP_AUTHORIZATION') # auth == 'Basic cGhpbGlwcDpka2ZhamRrZg=='
  97         if auth: # empty string if HTTP_AUTHORIZATION not present
  98                 auth_parts = auth.split(' ')
  99                 auth_method = 'Basic'
 100                 if len(auth_parts) != 2 or auth_parts[0] != auth_method:
 101                         raise AuthWrongMethod()
 102                 try:
 103                         auth_decoded = base64.b64decode(auth_parts[1]) # auth_decoded == 'philipp:dkfajdkf'
 104                 except TypeError:
 105                         raise AuthBasicError()
 106                 auth_decoded_parts = auth_decoded.split(':')
 107                 if len(auth_decoded_parts) != 2:
 108                         raise AuthBasicError()
 109                 username, password = auth_decoded_parts
 110
 111         # check username and password
 112         if username is None and password is None:
 113                 raise CredentialsMissing()
 114
 115         # check username
 116         if username is None:
 117                 raise UsernameMissing()
 118         try:
 119                 user_info = pwd.getpwnam(username)
 120         except KeyError:
 121                 raise UsernameInvalid()
 122         if user_info.pw_uid < 1000:
 123                 raise UsernameInvalid()
 124
 125         # check password
 126         if password is None:
 127                 raise PasswordMissing()
 128         if password != PASSWORD:
 129                 raise PasswordWrong()
 130
 131         # check hostname
 132         if hostname is None:
 133                 raise HostnameMissing()
 134         if re.match(r'[-0-9a-z]+(\.[-0-9a-z]+)*$', hostname) is None:
 135                 raise HostnameInvalid()
 136
 137         # strip zone
 138         hostname = hostname.strip()
 139
 140         # check offline
 141         if offline is None or offline.lower() == 'no':
 142                 offline = False
 143         elif offline.lower() == 'yes':
 144                 offline = True
 145         else:
 146                 raise OfflineInvalid()
 147
 148         # check IP address
 149         if not offline:
 150                 if myip is None:
 151                         # try HTTP_X_FORWARDED_FOR
 152                         myip = os.environ.get('HTTP_X_FORWARDED_FOR')
 153                         if not myip: # empty string if not present
 154                                 # try REMOTE_ADDR
 155                                 myip = os.environ.get('REMOTE_ADDR')
 156                                 if not myip: # empty string if not present
 157                                         raise MyipMissing()
 158         if not myip is None:
 159                 try:
 160                         ipaddr.IPAddress(myip) # throws an exception if the IP address is not valid
 161                 except ValueError:
 162                         raise MyipInvalid()
 163
 164         # update bind
 165         call_params = ['sudo', 'tdyndns_update']
 166         if offline:
 167                 call_params.append('--delete')
 168         if myip is not None:
 169                 call_params.extend(['--ip', myip])
 170         call_params.append(hostname)
 171         retcode = call(call_params)
 172         if retcode != 0:
 173                 raise NsupdateError()
 174
 175         # return success
 176         print "Content-Type: text/html"
 177         print
 178         print "good"
 179         # Note: we should return 'nochg' in case the IP has not changed, however we don't know yet.
 180
 181
 182 except CredentialsMissing as error:
 183         print "Content-Type: text/html"
 184         print "Status: 401 Unauthorized"
 185         print "WWW-Authenticate: Basic realm='tdyndns'"
 186         print
 187
 188 except DynDnsError as error:
 189         print "Content-Type: text/html"
 190         print "Status: 200 OK"
 191         print
 192         print error.returncode
 193