cgi-bin/dyndns.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 ZONE = '.dyn.colgarra.priv.at'
  17 DEBUG = False
  18
  19
  20 # Just for debugging:
  21 if DEBUG:
  22         import cgitb
  23         cgitb.enable()
  24
  25
  26 # Base class for our exceptions
  27 class DynDnsError(Exception):
  28         pass
  29
  30 class AuthError(DynDnsError):
  31         returncode = 'badauth'
  32
  33 class CredentialsMissing(AuthError):
  34         pass
  35
  36 class UsernameMissing(AuthError):
  37         pass
  38
  39 class UsernameInvalid(AuthError):
  40         pass
  41
  42 class PasswordMissing(AuthError):
  43         pass
  44
  45 class PasswordWrong(AuthError):
  46         pass
  47
  48 class AuthWrongMethod(AuthError):
  49         returncode = 'wrongauthmethod' # not documented at dyn.com
  50
  51 class AuthBasicError(AuthError):
  52         returncode = 'authbasicerror' # not documented at dyn.com
  53
  54 class HostnameError(DynDnsError):
  55         returncode = 'notfqdn'
  56
  57 class HostnameMissing(HostnameError):
  58         pass
  59
  60 class PasswordWrong(HostnameError):
  61         pass
  62
  63 class MyipError(DynDnsError):
  64         returncode = 'badip' # not documented at dyn.com
  65
  66 class MyipMissing(MyipError):
  67         pass
  68
  69 class MyipInvalid(MyipError):
  70         pass
  71
  72 class OfflineInvalid(DynDnsError):
  73         returncode = 'badparam' # not documented at dyn.com
  74
  75
  76 fields = cgi.FieldStorage()
  77
  78 # the following fields are supported by most dyndns providers
  79 # if a parameter is not provided, the .getvalue method returns None
  80 username = fields.getvalue('username')
  81 password = fields.getvalue('password')
  82 hostname = fields.getvalue('hostname')
  83 myip     = fields.getvalue('myip')
  84 wildcard = fields.getvalue('wildcard')
  85 mx       = fields.getvalue('mx')
  86 backmx   = fields.getvalue('backmx')
  87 offline  = fields.getvalue('offline')
  88 system   = fields.getvalue('system')
  89 url      = fields.getvalue('url')
  90
  91
  92 try:
  93         # Optional Auth Basic
  94         auth = os.environ.get('HTTP_AUTHORIZATION') # auth == 'Basic cGhpbGlwcDpka2ZhamRrZg=='
  95         if auth: # empty string if HTTP_AUTHORIZATION not present
  96                 auth_parts = auth.split(' ')
  97                 auth_method = 'Basic'
  98                 if len(auth_parts) != 2 or auth_parts[0] != auth_method:
  99                         raise AuthWrongMethod()
 100                 try:
 101                         auth_decoded = base64.b64decode(auth_parts[1]) # auth_decoded == 'philipp:dkfajdkf'
 102                 except TypeError:
 103                         raise AuthBasicError()
 104                 auth_decoded_parts = auth_decoded.split(':')
 105                 if len(auth_decoded_parts) != 2:
 106                         raise AuthBasicError()
 107                 username, password = auth_decoded_parts
 108
 109         # check username and password
 110         if username is None and password is None:
 111                 raise CredentialsMissing()
 112
 113         # check username
 114         if username is None:
 115                 raise UsernameMissing()
 116         try:
 117                 user_info = pwd.getpwnam(username)
 118         except KeyError:
 119                 raise UsernameInvalid()
 120         if user_info.pw_uid < 1000:
 121                 raise UsernameInvalid()
 122
 123         # check password
 124         if password is None:
 125                 raise PasswordMissing()
 126         if password != PASSWORD:
 127                 raise PasswordWrong()
 128
 129         # check hostname
 130         if hostname is None:
 131                 raise HostnameMissing()
 132         if re.match(r'[-0-9a-z]+(\.[-0-9a-z]+)*$', hostname) is None:
 133                 raise HostnameInvalid()
 134
 135         # strip zone
 136         hostname = hostname.strip()
 137         if hostname.endswith(ZONE):
 138                 hostname = hostname[:-len(ZONE)]
 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                 try:
 159                         ip = ipaddr.IPAddress(myip) # throws an exception if the IP address is not valid
 160                 except ValueError:
 161                         raise MyipInvalid()
 162                 if isinstance(ip, ipaddr.IPv4Address):
 163                         iptype = 'A'
 164                 elif isinstance(ip, ipaddr.IPv6Address):
 165                         iptype = 'AAAA'
 166                 else:
 167                         raise MyipInvalid() # should never happen
 168
 169         # update bind
 170         if offline:
 171                 call(['sudo', '/usr/local/bin/nsupdate_dyndns', '--delete', hostname])
 172         else:
 173                 call(['sudo', '/usr/local/bin/nsupdate_dyndns', '--ip', myip, hostname])
 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