Reliable Penguin

Need to block am IP address from your server? Here's an IPTables command:

/sbin/iptables -I INPUT -s w.x.y.z -j DROP

where w.x.y.z is the IP address to be blocked.

Here's a way to block and address with just the route command:

/sbin/route add -host w.x.y.z reject

The National Security Agency publishes a great collection of documents that provide detailed security configuration guidelines. The full index can be found here:

http://www.nsa.gov/ia/guidance/security_configuration_guides/index.shtml

We particularly like the guides for RedHat EL5:

“Hardening Tips For Default Installation of Red Hat Enterprise Linux 5”
http://www.nsa.gov/ia/_files/factsheets/rhel5-pamphlet-i731.pdf

“Guide to the Secure Configuration of Red Hat Enterprise Linux 5”
http://www.nsa.gov/ia/_files/os/redhat/rhel5-guide-i731.pdf

Here's how to filter or block ICMP timestamp requests and replies.

On Redhat/CentOS, edit /etc/sysconfig/iptables and add the following lines

-A RH-Firewall-1-INPUT -p ICMP --icmp-type timestamp-request -j DROP
-A RH-Firewall-1-INPUT -p ICMP --icmp-type timestamp-reply -j DROP

and then run:

/sbin/iptables restart

Or run the following commands:

/sbin/iptables -I RH-Firewall-1-INPUT 1 -p ICMP --icmp-type timestamp-request -j DROP
/sbin/iptables -I RH-Firewall-1-INPUT 1 -p ICMP --icmp-type timestamp-reply -j DROP
/sbin/service iptables save

Recently on an Ubantu server we just added these lines to /etc/rc.local:

/sbin/iptables -I INPUT 1 -p ICMP --icmp-type timestamp-request -j DROP
/sbin/iptables -I INPUT 1 -p ICMP --icmp-type timestamp-reply -j DROP

lftp support ftps (different from sftp). ftps is ftp over an explicit TLS (SSL) connection. We've seen a few sites running MS IIS that require ftps and getting lftp to work has been tricky. To make it work verify that your lftp build has gnutls support compiled in with:

lftp -v

This build does not:

Libraries used: Readline 5.1, Expat 1.95.8, OpenSSL 0.9.8d 28 Sep 2006

Here's one that does:

Libraries used: Readline 5.1, Expat 1.95.8, GnuTLS 2.6.6, zlib 1.2.3

Once you have have TLS support in your lftp build then you can put a file with something like this:

lftp -c 'open -e "set ftps:initial-prot ""; \
   set ftp:ssl-force true; \
   set ftp:ssl-protect-data true; \
   put test.txt; " \
   -u "USERNAME","PASSWORD" \
   ftps://HOSTNAME:990 '

The option sets are critical as lftp wants to do "PROT C" by default but Windows wants to see "PROT P".

RHEL5 replaced the old smbmount command with mount.cifs so to mount a shared Windows drive do something like:


mount -t cifs //servername/sharename /mnt/mountpoint \
-o username=myusername,password=mypassword