Further explanations

More about RPM, Red Hat's package Manager

There is much discussion about installing packages in "RPM format". These files end in ".rpm" and usually one uses Red Hat's Red Hat Package Manager, rpm, to do this. To install file foo.rpm do

rpm -vhU foo.rpm

This also works for HTTP and FTP URLs similarly to

rpm -vhU http://www.wizbang.com/this/that/foo.rpm

rpm -vhU ftp://www.wizbang.com/this/that/foo.rpm

The rpm program can be used on non-Red Hat-derived Linux and UNIX distributions with some finagling. An alternative is to use the Bourne Shell script rpm2targz.sh to convert RPM files from, say, foo.rpm to foo.tar.gz. The foo.tar.gz file will contain all of the files that were in the foo.rpm file, except for signatures and installation and removal instructions.

For most "add on" software, the foo.tar.gz file can be extracted (with "tar -xzvf foo.tar.gz") into its own subdirectory. Then a cd to that directory, followed with "./configure", "make", "su" and "make install" will finish the installation. This is not to denigrate the RPM program; I think that it is a wonderfully innovative idea on Red Hat's part.

This script uses the rpmoffset.c program. The script and the program's source are on the book's web site. The signature files are rpm2targz.sh.sig and rpmoffset.c.sig.

The PPP protocol does not support broadcast addresses

Thus, in section 12.4.6 "Blocking external evil" on page 416, if your Internet connection is through PPP, there is no need to block broadcast addresses. The lines in rc.fw that refer to EXTBC should be commented out in this case (though they do no harm).

The ANI acronym

In section 10.7 "Cracking with a Laptop and a Pay Phone" on page 355, the acronym ANI is mentioned without explanation. It stands for Automatic Number Identification. It allows the owner of an 800 number service to see the number of someone calling in regardless of whether it is unlisted or if other techniques were used that normally block the recipient from seeing it.

Creating a VPN using SSH, PPP,and Perl

In section 12.1.5 "VPN Using SSH, PPP, and Perl" on page 386, a URL is given to download the ssh-ppp VPN script. There is explanation on how to use this script at

http://csociety.ecn.purdue.edu/~sigos/projects/ssh/forwarding/index.html#VPN

It is important to note that getting the routes correct can be challenging and that this may take some time. For example, suppose that you want to create a VPN to the 192.168.1.* subnet (with netmask 255.255.255.0). Typically the firewall/VPN for that subnet would be 192.168.1.1 and the VPN would be through network interface ppp0. Assume that the route to the 192.168.1.1 system is via eth0.

You would want to route 192.168.1.* traffic via interface ppp0 to get the VPN protection. However, the traffic to 192.168.1.1 must be via eth0 using the 192.168.1.1 system as a gateway. An additional complication is that if you attempt to use the route program to route the 192.168.1.* network via ppp0 with gateway 192.168.1.1, it will reject the command. This is because 192.168.1.1 is via a different interface. This might be considered a bug.

The solution is to create a temporary route to 192.168.1.1 via ppp0. Then issue the route command to route 192.168.1.* using 192.168.1.1 as the gateway via the ppp0 interface. If the first route to 192.168.1.1 is via eth0, that route will be used. However, for good practice, use route to delete the route to 192.168.1.1 via ppp0.

Note too that the noauth attribute to pppd must be added to the script on the pppd command line and that some distributions, such as Slackware 7.1, do not have all of the Perl modules required by this Perl program; they will need to be added. For SW7.1, the missing modules are contained in perllib.tar, which has the perllib.tar.sig signature. This tar file may be used for other distributions too and was taken from Mandrake 7.1.

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