12-30-2003
Hi,
I don't know if I understood your question...
If your default rule is to block everything, then you have to specify exactly what you want to access ( or what you want to access you ! )... so, if your default rule is to block all, then you have to specify that you want to allow traffic in and out... otherwise, you don't need any of them, all traffic will be allowed...
Let me try to explain the "keep state" and see if it fits on your solution...
You have SSHd ( for example ), running on the server A and you want all clients to be able to use it... you only need to specify one rule, the "in" rule, and the filter will be able to detect that the connection that goes out, belongs to the same connection that was started before... you have to specify on the server that you want to allow port 22 in, keeping state... instead of specifing that you want to allow connection in and out on that port...
If it doesn't look simple, it's because english is not my first language, because it is simple... :-)
Good luck !
Last edited by jsilva; 12-30-2003 at 05:47 AM..
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LEARN ABOUT DEBIAN
ypserv.conf
YPSERV.CONF(5) Reference Manual YPSERV.CONF(5)
NAME
ypserv.conf - configuration file for ypserv and rpc.ypxfrd
DESCRIPTION
ypserv.conf is an ASCII file which contains some options for ypserv. It also contains a list of rules for special host and map access for
ypserv and rpc.ypxfrd. This file will be read by ypserv and rpc.ypxfrd at startup, or when receiving a SIGHUP signal.
There is one entry per line. If the line is a option line, the format is:
option: <argument>
The line for an access rule has the format:
host:domain:map:security
All rules are tried one by one. If no match is found, access to a map is allowed.
Following options exist:
files: 30
This option specifies, how many database files should be cached by ypserv. If 0 is specified, caching is disabled. Decreasing this
number is only possible, if ypserv is restarted.
trusted_master: server
When a map is pushed to a slave, the slave normally only accepts updates to existing maps, and then only from the real master. If
this option is set on a slave server, new (not yet existing) maps from the host server will be accepted. The default is that no
trusted master is set and new maps will not be accepted.
Example:
trusted_master: ypmaster.example.org
slp: [yes|<no>|domain]
If this option is enabled and SLP support compiled in, the NIS server registers itself on a SLP server. If the variable is set to
domain, an attribute domain with a comma seperated list of supported domainnames is set. Else this attribute will not be set.
xfr_check_port: [<yes>|no]
With this option enabled, the NIS master server has to run on a priviliged port (< 1024). The default is "yes" (enabled).
The field descriptions for the access rule lines are:
host IP address. Wildcards are allowed.
Examples:
131.234. = 131.234.0.0/255.255.0.0
131.234.214.0/255.255.254.0
domain specifies the domain, for which this rule should be applied. An asterix as wildcard is allowed.
map name of the map, or asterisk for all maps.
security
one of none, port, deny:
none always allow access.
port allow access if the client request originates from a priviliged port (< 1024). Otherwise do not allow access.
deny deny access to this map.
You can add /mangle:field to the none or port security keywords. The :field part is optional. It will replace field number field (the
default is 2, the password field of the passwd and shadow maps) with the value x for client requests from non-priviliged ports (>= 1024)
for the port security keyword and in all cases for the none security keyword.
FILES
/etc/ypserv.conf
SEE ALSO
ypserv(8), rpc.ypxfrd(8)
WARNINGS
The access rules for special maps are no real improvement in security, but they make the life a little bit harder for a potential hacker.
BUGS
Solaris clients don't use privileged ports. All security options that depend on privileged ports cause big problems on Solaris clients.
AUTHOR
Thorsten Kukuk <kukuk@suse.de>
YP Server December 2003 YPSERV.CONF(5)