eegrok

# generally speaking if you run ssh -X <remotehost>
# you'll be able to run X applications on the remote host, displaying them on your machine
# if you need to run them as a different user, there are a couple things you need to setup as the new user
# after su'ing to the new user, you need to: 
# (note that the .Xauthority file must be readable by the su'd to user -- or else you need to copy the file somewhere it is readable)
# export XAUTHORITY=/home/[the original user]/.Xauthority
# export DISPLAY=(whatever the DISPLAY property was before you su'd -- probably localhost:10.0)
# the .Xauthority file needs to be readable by the new user as well (when I've done it, I've just copied ~/.Xauthority to /tmp or something for a bit -- of course this means anyone can display on your screen who sees that file -- so caution is a good thing.

eegrok

# if you are dropping packets using iptables, you can use a couple commands to log those blocked packets
# for example, to log & block all traffic incoming to 172.25.0.1, you could use the following:
iptables -A INPUT -p tcp -d 172.25.0.1 -j LOG --log-prefix "blocked 172.25.0.1 :"
iptables -A INPUT -p tcp -d 172.25.0.1 -j DROP

eegrok

# I currently have the following aliases on mac osx, that I use to allow a bunch of different port forwarding through ssh
# the 10.0.2.16 alias appears to work fine without the route add -host call for it
# but the 10.0.2.18 alias doesn't.
# test (order important?)
# test (more than 2?)
# look at netstat -nr to see routes


alias aliasip='sudo ifconfig en1 alias 10.0.2.16 255.255.255.0; sudo ifconfig en1 alias 10.0.2.18 255.255.255.0; sudo route add -host 10.0.2.18 -interface 127.0.0.1'
alias unaliasip='sudo ifconfig en1 -alias 10.0.2.16; sudo route delete -host 10.0.2.18 -interface 127.0.0.1; sudo ifconfig en1 -alias 10.0.2.18'

eegrok

// create a file named setuid_script.cpp with the following contents:

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <unistd.h>


int main(int argc, const char* argv[]) {
    printf(

eegrok

# so recently I had an issue where I wanted to send email sent to a local user root (from logwatch, e.g.) to a different email address
# simple enough -- just add a ~root/.forward file, with the contents [email protected]
# all the email gets sent there...
# but the email shows up with a to: header of [email protected]
# what I really want is the to: header to be [email protected]
# so I can filter emails, etc...  below is how to do that.

#uncomment the following line in /etc/postfix/main.cf
#header_checks = regexp:/etc/postfix/header_checks

eegrok

#command-line capture packets for viewing in wireshark
tcpdump -i <interface> -s 65535 -w <some-file>


# see how many prerouting packets received / etc...
iptables -t nat --list --verbose
# can compare this with filter packets
iptables -t filter --list --verbose

eegrok

# from http://www.debuntu.org/how-to-redirecting-network-traffic-a-new-ip-using-iptables

# enable ip forwarding until reboot
echo 1 > /proc/sys/net/ipv4/ip_forward
# enable ip forwarding after reboot
# edit /etc/sysctl.conf
# uncomment line: #net.ipv4.ip_forward=1

eegrok

#on redhat based linux's
service iptables save

#on debian based linux's
#put the following 2 lines in your /etc/network/interfaces file
post-up iptables-restore < /etc/iptables.rules
post-down iptables-save > /etc/iptables.rules

# it'll then automatically save -- if you want to guard against a possible hard powerdown (power plug pulled, e.g.)
# you can manually save them then using

eegrok

#partially from: http://www.throx.net/2008/04/13/openvpn-and-centos-5-installation-and-configuration-guide/
wget http://swupdate.openvpn.net/community/releases/openvpn-2.1.4.tar.gz
wget http://openvpn.net/release/lzo-1.08-4.rf.src.rpm
wget http://www.opensc-project.org/files/pkcs11-helper/pkcs11-helper-1.08.tar.bz2
wget ftp://fr2.rpmfind.net/linux/dag/redhat/el5/en/x86_64/dag/RPMS/pkcs11-helper-devel-1.08-1.el5.rf.x86_64.rpm
wget ftp://rpmfind.net/linux/dag/redhat/el5/en/x86_64/dag/RPMS/pkcs11-helper-1.08-1.el5.rf.x86_64.rpm

yum install rpm-build
yum install autoconf.noarch
yum install zlib-devel

eegrok

#modify the remote myremote.mydomain to be the server address
remote myremote.mydomain
dev tun
ifconfig 172.23.0.2 172.23.0.1
secret /etc/openvpn/static.key
# uncomment this to keep this connection alive if you need to connect from the server to the client sometimes
# keepalive 10 120