root / pykota / trunk / SECURITY @ 2478

# $Id$

PyKota - Print Quotas for CUPS and LPRng

(c) 2003, 2004, 2005 Jerome Alet <alet@librelogiciel.com>
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 2 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, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

====================================================================

How to improve PyKota's security :
----------------------------------

  - Secure your printers :  
  
    This is the most important thing to do !
    
    Tell them to refuse any print job not coming from your print server. 
    Do this with telnet to set ACLs based on incoming IP addresses if 
    possible, or through any other way. 
        
    Put all your printers on a private unroutable subnet, different from 
    the subnet on which your client hosts will reside. Ensure that the 
    only machine allowed to access to this subnet is your print server. 
    
    
  - Secure your print servers :  
  
    Don't give shell access to your users on your print servers, and 
    don't let them execute unauthorized commands : they could very well 
    compile and/or execute tools like NetCat, and send datas directly to 
    the printer in the case the printer is networked, thus bypassing the 
    printing system and PyKota. 
        
    Ensure that no regular user can read PyKota administrator's 
    configuration file, but that both the PyKota Administrator and the 
    user the printing system is run as can read it. With CUPS under 
    Debian you may want to do : 
    
        $ chown pykota.pykota ~pykota/pykota.conf ~pykota/pykotadmin.conf    
        $ chmod 640 ~pykota/pykota.conf
        $ chmod 600 ~pykota/pykotadmin.conf
        
    Depending on your needs, you may want to put the user the printing 
    system is run as in the group 'pykota', and relax permissions a bit 
    so that this user can read the pykotadmin.conf file while printing. 
    For example : 
    
        $ chmod 640 ~pykota/pykotadmin.conf
        $ adduser lp pykota
          (this makes user 'lp' a member of group 'pykota')
    
    Another solution, needed on some systems :
    
        $ chmod a+rx ~pykota/
        $ chown lp.pykota ~pykota/pykota.conf ~pykota/pykotadmin.conf 
        
    Letting any user read PyKota administrator's configuration file may 
    expose passwords or database information which would allow write 
    access to the database, and so may transform your print quota 
    management in a nightmare. 
  
    If you want to let users generate their own print quota reports, 
    then ensure that /etc/pykota/pykota.conf is readable by these users. 
    To do this you can either put this users in the group 'pykota' while 
    ensuring they can't read pykotadmin.conf with 'chmod 600 pykotadmin.conf'
    or simply allow everyone to read pykota.conf with 'chmod 644 pykota.conf'
    
      
  - Secure your database connections :
  
    Depending on the database backend used, either PostgreSQL or LDAP, 
    you may have to take additionnal measures to render your database 
    more secure. Please refer to your database system's documentation 
    to learn how to do so. This is out of the scope of the present 
    document which will only give basic informations. 
    
    Keep in mind that if you use a centralized database, the first thing
    you may want to do is to restrict which hosts can access to it, i.e.
    only the print servers.
  
    PostgreSQL :
    
      For the PostgreSQL backend, PyKota already defines a user with 
      read/write access and another user with read-only access to the 
      Print Quota Database. PyKota doesn't set any passwords for these 
      users though, but doing so is recommended, and here's how to do :
      
      From the root shell do :
      
      $ su - postgres
      $ psql template1
      template1=# ALTER USER pykotauser WITH PASSWORD 'a.difficult.password';
      template1=# ALTER USER pykotaadmin WITH PASSWORD 'another.password';
      template1=# \q
      $ exit
      
      Now modify PostgreSQL's pg_hba.conf to restrict access to the PyKota
      database to PostgreSQL users 'pykotauser' and 'pykotaadmin' only, 
      and only if they connect from localhost and provide the correct 
      password. Here's an excerpt from our own pg_hba.conf :
        
        --- CUT ---        
        local all    postgres                              ident sameuser
        local all    all                                   reject
        host  pykota pykotauser  127.0.0.1 255.255.255.255 crypt
        host  pykota pykotaadmin 127.0.0.1 255.255.255.255 crypt
        host  pykota all         127.0.0.1 255.255.255.255 reject
        --- CUT ---        
        
      As an alternative, which may depend on the default encryption setting  
      used by your version of PostgreSQL, you may want to use the following
      settings instead :

        --- CUT ---        
        local all    postgres                              ident sameuser
        local all    all                                   reject
        host  pykota pykotauser  127.0.0.1 255.255.255.255 md5
        host  pykota pykotaadmin 127.0.0.1 255.255.255.255 md5
        host  pykota all         127.0.0.1 255.255.255.255 reject
        --- CUT ---        
        
      Finally restart PostgreSQL so that the changes will be applied :
      
        $ /etc/init.d/postgresql restart
        
      Of course, depending on your needs, you may want to secure
      your database connections in a completely different way or 
      add other security layers on top of this. To do so please
      refer to PostgreSQL's documentation because this is out of
      the scope of the present document.
      
    LDAP :
    
      For the LDAP backend, you have to ensure that no regular user can 
      write to any PyKota specific attribute or objectClass. Otherwise 
      they could modify their quota at will. Here too you will have to 
      create two LDAP users which will be used for readonly and read+write
      access to PyKota's datas. PyKota currently doesn't do this, so
      you have to create an LDIF file this way (please adapt the
      DNs to your own environment) :
      
        --- CUT ---      
        dn: cn=pykotauser,dc=example,dc=com
        cn: pykotauser
        objectClass: simpleSecurityObject
        objectClass: organizationalRole
        description: PyKota ReadOnly User
        userPassword: {CRYPT}jfdsk653dsZFL
        
        dn: cn=pykotaadmin,dc=example,dc=com
        cn: pykotaadmin
        objectClass: simpleSecurityObject
        objectClass: organizationalRole
        description: PyKota Read+Write User
        userPassword: {CRYPT}kqsIu43Exoi5s
        --- CUT ---

      Then add these two users to your existing LDAP tree :
      
        $ ldapadd -W -x -D "cn=admin,dc=example,dc=com" -f users.ldif
    
      Now modify your LDAP server's configuration to respectively allow
      read+write and readonly access to the datas :
      
        --- CUT ---
        by dn="cn=pykotaadmin,dc=example,dc=com" write
        by dn="cn=pykotauser,dc=example,dc=com" read
        --- CUT ---

      Finally restart your LDAP server so that the changes will be applied :
      
        $ /etc/init.d/slapd restart
        
      Of course, depending on your needs, you may want to secure
      your database connections in a completely different way or 
      add other security layers on top of this. To do so please
      refer to your LDAP server's documentation because this is out 
      of the scope of the present document.
        
        
  - Secure your CGI scripts :    
  
    If you use printquota.cgi or dumpykota.cgi, ensure that the user 
    they are run as can read the pykota.conf file but NOT the 
    pykotadmin.conf file. 
        
    The particular user they will be run as depends on your web server's 
    settings. 
        
    If you want to further restrict the access to these CGI scripts, 
    please read your web server's documentation to add either 
    encryption, authentication or both. 
        
    The CGI scripts will honor the content of the REMOTE_USER CGI 
    environment variable which is set by your web server if an 
    authentication took place. If REMOTE_USER contains 'root' then, even 
    if you didn't authenticate using the real root account and password, 
    the scripts will consider they have been run by a PyKota 
    administrator and will report all datas if asked to do so. If 
    REMOTE_USER is not present, which means that you didn't chose to 
    secure access to your CGI scripts, the same will happen. If 
    REMOTE_USER contains something else, only datas pertaining to this 
    user will be made available through the web. 
    
    NB : In any case, the CGI scripts actually included in PyKota only
    do readonly accesses to PyKota's database.
    
====================================================================