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 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
  75 fields = cgi.FieldStorage()
  76
  77 # the following fields are supported by most dyndns providers
  78 # if a parameter is not provided, the .getvalue method returns None
  79 username = fields.getvalue('username')
  80 password = fields.getvalue('password')
  81 hostname = fields.getvalue('hostname')
  82 myip     = fields.getvalue('myip')
  83 wildcard = fields.getvalue('wildcard')
  84 mx       = fields.getvalue('mx')
  85 backmx   = fields.getvalue('backmx')
  86 offline  = fields.getvalue('offline')
  87 system   = fields.getvalue('system')
  88 url      = fields.getvalue('url')
  89
  90
  91 try:
  92         # Optional Auth Basic
  93         auth = os.environ.get('HTTP_AUTHORIZATION') # auth == 'Basic cGhpbGlwcDpka2ZhamRrZg=='
  94         if auth: # empty string if HTTP_AUTHORIZATION not present
  95                 auth_parts = auth.split(' ')
  96                 auth_method = 'Basic'
  97                 if len(auth_parts) != 2 or auth_parts[0] != auth_method:
  98                         raise AuthWrongMethod()
  99                 try:
 100                         auth_decoded = base64.b64decode(auth_parts[1]) # auth_decoded == 'philipp:dkfajdkf'
 101                 except TypeError:
 102                         raise AuthBasicError()
 103                 auth_decoded_parts = auth_decoded.split(':')
 104                 if len(auth_decoded_parts) != 2:
 105                         raise AuthBasicError()
 106                 username, password = auth_decoded_parts
 107
 108         # check username and password
 109         if username is None and password is None:
 110                 raise CredentialsMissing()
 111
 112         # check username
 113         if username is None:
 114                 raise UsernameMissing()
 115         try:
 116                 user_info = pwd.getpwnam(username)
 117         except KeyError:
 118                 raise UsernameInvalid()
 119         if user_info.pw_uid < 1000:
 120                 raise UsernameInvalid()
 121
 122         # check password
 123         if password is None:
 124                 raise PasswordMissing()
 125         if password != PASSWORD:
 126                 raise PasswordWrong()
 127
 128         # check hostname
 129         if hostname is None:
 130                 raise HostnameMissing()
 131         if re.match(r'[-0-9a-z]+(\.[-0-9a-z]+)*$', hostname) is None:
 132                 raise HostnameInvalid()
 133
 134         # strip zone
 135         hostname = hostname.strip()
 136
 137         # check offline
 138         if offline is None or offline.lower() == 'no':
 139                 offline = False
 140         elif offline.lower() == 'yes':
 141                 offline = True
 142         else:
 143                 raise OfflineInvalid()
 144
 145         # check IP address
 146         if not offline:
 147                 if myip is None:
 148                         # try HTTP_X_FORWARDED_FOR
 149                         myip = os.environ.get('HTTP_X_FORWARDED_FOR')
 150                         if not myip: # empty string if not present
 151                                 # try REMOTE_ADDR
 152                                 myip = os.environ.get('REMOTE_ADDR')
 153                                 if not myip: # empty string if not present
 154                                         raise MyipMissing()
 155                 try:
 156                         ip = ipaddr.IPAddress(myip) # throws an exception if the IP address is not valid
 157                 except ValueError:
 158                         raise MyipInvalid()
 159                 if isinstance(ip, ipaddr.IPv4Address):
 160                         iptype = 'A'
 161                 elif isinstance(ip, ipaddr.IPv6Address):
 162                         iptype = 'AAAA'
 163                 else:
 164                         raise MyipInvalid() # should never happen
 165
 166         # update bind
 167         if offline:
 168                 call(['sudo', '/usr/local/bin/nsupdate_dyndns', '--delete', hostname])
 169         else:
 170                 call(['sudo', '/usr/local/bin/nsupdate_dyndns', '--ip', myip, hostname])
 171
 172         # return success
 173         print "Content-Type: text/html"
 174         print
 175         print "good"
 176         # Note: we should return 'nochg' in case the IP has not changed, however we don't know yet.
 177
 178
 179 except CredentialsMissing as error:
 180         print "Content-Type: text/html"
 181         print "Status: 401 Unauthorized"
 182         print "WWW-Authenticate: Basic realm='tdyndns'"
 183         print
 184
 185 except DynDnsError as error:
 186         print "Content-Type: text/html"
 187         print "Status: 200 OK"
 188         print
 189         print error.returncode
 190