Tiptop Software Company

Sometimes, nothing is more convenient than to do a port scan on a machine to find out what services it offers. The nmap command is very useful to do this:


nmap -sS 192.168.1.1
Starting Nmap 4.53 ( http://insecure.org ) at 2009-06-12 10:11 MDT
Interesting ports on 192.168.1.1 (192.168.1.1):
Not shown: 1683 closed ports
PORT STATE SERVICE
1/tcp filtered tcpmux
4/tcp filtered unknown
7/tcp filtered echo
8/tcp filtered unknown
10/tcp filtered unknown
13/tcp filtered daytime
14/tcp filtered unknown
18/tcp filtered msp
19/tcp filtered chargen
21/tcp open ftp
22/tcp open ssh
23/tcp filtered telnet
25/tcp filtered smtp
53/tcp filtered domain
80/tcp open http
110/tcp open pop3
137/tcp filtered netbios-ns
194/tcp filtered irc
445/tcp filtered microsoft-ds
529/tcp filtered irc
873/tcp open rsync
994/tcp filtered ircs
1026/tcp filtered LSA-or-nterm
1434/tcp filtered ms-sql-m
4000/tcp open remoteanything
6000/tcp filtered X11
6662/tcp filtered radmind
6667/tcp filtered irc
6669/tcp filtered irc
7000/tcp filtered afs3-fileserver
32773/tcp filtered sometimes-rpc9

Nmap done: 1 IP address (1 host up) scanned in 4.500 seconds


Writing in Flex was a nice experience because it’s so Java-like.   Then I started writing Ruby on Rail apps.

Don’t get me wrong, I definitely appreciate the power that the ruby language and RoR framework provides.   But, face it, if you’re used to Java, the ruby syntax can be …hmmm…. unfamiliar.

My first obstacle was figuring out file extensions:

• .erb are embedded ruby tags, e.g. <%.  May see an html.erb file.
• .rb are ruby scripts or RoR class files
• .rhtml - ruby on rails script (application/x-httpd-eruby)

That’s when I found a helpful site called filext.com which is pretty good for looking up file extensions.

A common problem for people is running an executable and having it fail because it cannot find some shared library need for the executable. The best way to make sure that an executable has access to all the shared libraries it needs is the ldd command. Just run it:

terry@c103:~$ ldd /bin/bash
linux-gate.so.1 => (0xffffe000)
libncurses.so.5 => /lib/libncurses.so.5 (0xb7f07000)
libdl.so.2 => /lib/tls/i686/cmov/libdl.so.2 (0xb7f03000)
libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0xb7dc1000)
/lib/ld-linux.so.2 (0xb7f59000)
terry@c103:~$

If any of the libraries are not found, they will show up as missing. Use the LD_LIBRARY_PATH environment variable to add in the path to the missing libraries.
terry@c103:~$ export LD_LIBRARY_PATH=~/lib
terry@c103:~$ env | grep LD
LD_LIBRARY_PATH=/home/terry/lib
terry@c103:~$

The sox program is a nice simple utility for converting audio data files from one format to another. After conversion, you can use many different audio editing utilities to modify the sound and use sox to convert the sound file back to your desired format. Using this for a telephony application, you have a wav file you have edited and you want to convert it back to 1 channel of 8000 samples/sec 16bit raw audio data:

sox -t wav recv0.wav -c 1 -r 8000 -s -w recv0.raw

The sox program is available under Ubuntu as an optional package. Adobe has a nice audio editing utility, but there are some good free ones as well. Two that I’ve used include Audacity and there is an audio studio program on Sourceforge. The audio studio program is a front end for sox and very simple, but it does the job for simple work.

When i get on a Redhat machine, I’m always trying to remember the commands to start and stop services and configure the /etc/rc*.d directories. Supposedly, if you just create your own links or remove your own links, the operating systems can revert your work. You should use the chkconfig command to enable and disable services. For example:

chkconfig mysqld on

The service command can be used to start or stop services.

service mysqld start

instead of the old

/etc/init.d/mysqld start

The service command is not too useful, but the chkconfig command is.

I’ve ripped a bunch of my CDs onto my computer over the years and many of them ore in the open OGG format which doesn’t work with my iPod or Treo. I wrote a simple little script to convert the OGG files to MP3 for my phone. Since Real Player on my phone only seems to support a flat directory structure, I created the file names out of artist and song name. I just mount up the SD card, change directory to it and run the script passing the songs I want to copy on the command like. Using wild cards makes it easy. For example:

cd /media/sdcard ;
ogg2mp3 /home/terry/jukebox/Yeah_Yeah_Yeahs/Show_Your_Bones/*

The script looks like this…

USAGE=false
if [ ! -f "$1" ]
then
echo "Usage $0 sourceFiles ..."
exit 1
fi TMPFILE=/tmp/tmp$$.wav
while [ $# -gt 0 ]
do
ogg123 -d wav -f $TMPFILE "$1"
DIRNAME=`dirname "$1"`
ALBUM=`basename $DIRNAME`
TMP=`dirname $DIRNAME`
ARTIST=`basename $TMP`
MP3FILE=`basename "$1" | sed -e 's/.ogg/.mp3/' | sed -e     's/^[0-9][0-9] - //'`
OUTFILE="${ARTIST}_${MP3FILE}"
echo "-------------$OUTFILE"
lame $TMPFILE "$OUTFILE"
shift
done
rm -f $TMPFILE

I’m trying to generate some generic SSL certificate code for Postfix and other products. This is customized for Postfix, but it is easy to change the output files. I’ve put this together to be a cut and paste, just set the environment variables.

keyfile=/etc/ssl/private/smtpd.key
certfile=/etc/ssl/certs/smtpd.crt
pemfile= /etc/ssl/certs/cacert.pem
pass=superSecret
openssl genrsa -des3 -rand /etc/hosts -passout "pass:$pass" -out $keyfile 1024
chmod 600 $keyfile
openssl req -new -passin "pass:$pass" -passout "pass:$pass" -key $keyfile -out /tmp/.server.csr
openssl x509 -req -days 3650 -passin "pass:$pass" -passout "pass:$pass" -in /tmp/.server.csr -signkey $keyfile -out $certfile
openssl rsa -passin "pass:$pass" -in $keyfile -out /tmp/.server.unencrypted
mv -f /tmp/.key.unencrypted $keyfile
openssl req -new -x509 -extensions v3_ca -keyout cakey.pem -out $pemfile -days 3650

If you run a server on the Internet and you do any type of security logging, you know people are constantly trying to find vulnerabilities to your site through ssh. You’ll get pages and pages of PAM authentication errors. Avoiding this is not difficult, just change the port your sshd listens on. Modify the Port parameter in /etc/ssh/sshd_conf and run /etc/init.d/ssh restart. When you log into the system, specify the port on the command line with the -p option.

ssh -p 404 www.tiptopsoftwarecompany.com