# $Id: SECURITY 3561 2013-01-04 22:34:24Z jerome $ PyKota - Print Quotas for CUPS (c) 2003-2013 Jerome Alet 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 . ==================================================================== 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, 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 already sets default passwords for these users, but you can change them later and 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. ====================================================================