Chapter 30. Network Programming

#!/bin/bash# test-cgi.sh# by Michael Zick# Used with permission# May have to change the location for your site.# (At the ISP's servers, Bash may not be in the usual place.)# Other places: /usr/bin or /usr/local/bin# Might even try it without any path in sha-bang.# Disable filename globbing.set -f# Header tells browser what to expect.echo Content-type: text/plainechoecho CGI/1.0 test script report:echoecho environment settings:setechoecho whereis bash?whereis bashechoecho who are we?echo ${BASH_VERSINFO[*]}echoecho argc is $#. argv is "$*".echo# CGI/1.0 expected environment variables.echo SERVER_SOFTWARE = $SERVER_SOFTWAREecho SERVER_NAME = $SERVER_NAMEecho GATEWAY_INTERFACE = $GATEWAY_INTERFACEecho SERVER_PROTOCOL = $SERVER_PROTOCOLecho SERVER_PORT = $SERVER_PORTecho REQUEST_METHOD = $REQUEST_METHODecho HTTP_ACCEPT = "$HTTP_ACCEPT" echo PATH_INFO = "$PATH_INFO" echo PATH_TRANSLATED = "$PATH_TRANSLATED" echo SCRIPT_NAME = "$SCRIPT_NAME" echo QUERY_STRING = "$QUERY_STRING" echo REMOTE_HOST = $REMOTE_HOSTecho REMOTE_ADDR = $REMOTE_ADDRecho REMOTE_USER = $REMOTE_USERecho AUTH_TYPE = $AUTH_TYPEecho CONTENT_TYPE = $CONTENT_TYPEecho CONTENT_LENGTH = $CONTENT_LENGTHexit 0# Here document to give short instructions.:<<-'_test_CGI_'1) Drop this in your http://domain.name/cgi-bin directory.2) Then, open http://domain.name/cgi-bin/test-cgi.sh._test_CGI_

#!/bin/bash# ip-addresses.sh# List the IP addresses your computer is connected to.#  Inspired by Greg Bledsoe's ddos.sh script,#  Linux Journal, 09 March 2011.# URL:#  http://www.linuxjournal.com/content/back-dead-simple-bash-complex-ddos#  Greg licensed his script under the GPL2,#+ and as a derivative, this script is likewise GPL2.connection_type=TCP  # Also try UDP.field=2   # Which field of the output we're interested in.no_match=LISTEN   # Filter out records containing this. Why?lsof_args=-ni # -i lists Internet-associated files.  # -n preserves numerical IP addresses.  # What happens without the -n option? Try it.router="[0-9][0-9][0-9][0-9][0-9]->" #   Delete the router info.lsof "$lsof_args" | grep $connection_type | grep -v "$no_match" |  awk '{print $9}' | cut -d : -f $field | sort | uniq |  sed s/"^$router"//#  Bledsoe's script assigns the output of a filtered IP list,#  (similar to lines 19-22, above) to a variable.#  He checks for multiple connections to a single IP address,#  then uses:## iptables -I INPUT -s $ip -p tcp -j REJECT --reject-with tcp-reset##  ... within a 60-second delay loop to bounce packets from DDOS attacks.#  Exercise:#  --------#  Use the 'iptables' command to extend this script#+ to reject connection attempts from well-known spammer IP domains.