CentOS: Install PHP 5.2 with t1lib support

The first step is to vanilla install PHP 5.2 (to handle any dependency issues) and then recompile it with the t1lib option. So enable the testing repo of CentOS 5. Change to root user first, then create the repo:

su -
vi /etc/yum.repos.d/CentOS-Testing.repo

Enter insert mode (hit i) and paste the following into the new file:

# CentOS-Testing:
# !!!! CAUTION !!!!
# This repository is a proving grounds for packages on their way to CentOSPlus and CentOS Extras.
# They may or may not replace core CentOS packages, and are not guaranteed to function properly.
# These packages build and install, but are waiting for feedback from testers as to
# functionality and stability. Packages in this repository will come and go during the
# development period, so it should not be left enabled or used on production systems without due
# consideration.
name=CentOS-5 Testing

Then update PHP and restart Apache (yum will double-check you want to go ahead):

yum update php*
service httpd restart

PHP is now updated, but the t1lib is not installed or compiled into PHP. So let’s download and install it (you’ll need make and gcc installed):

cd ~admin/software
wget ftp://sunsite.unc.edu/pub/Linux/libs/graphics/t1lib-5.1.2.tar.gz
tar zxfv t1lib-5.1.2.tar.gz
cd t1lib-5.1.2
make && make install

If it exits with a latex error, install latex:

yum -y install tetex-latex

Installing t1lib can also be accomplished if you have the rpmforge repo installed (see previous post step 6) with: yum --enablerepo=rpmforge install t1lib
If you upgrade your software in the future and get an error about libt1.so.5()(64bit) then install t1lib again using this method and then service httpd restart

Then run the make commands again. T1lib is now installed. Next step is to recompile PHP. Firstly, set up a build environment (still as root) and install some software that we’ll need to compile:

mkdir -p /usr/src/redhat/{SRPMS,RPMS,SPECS,BUILD,SOURCES}
chmod 777 /usr/src/redhat/{SRPMS,RPMS,SPECS,BUILD,SOURCES}
yum -y install rpm-build re2c bison flex

Now, we need to lose our root privileges to compile the software, so we need to run exit or logout to drop back to the admin user (make sure this is the right version of PHP you have just installed, use rpm -q php to check).

cd ~admin/software
wget http://dev.centos.org/centos/5/testing/SRPMS/php-5.2.10-1.el5.centos.src.rpm
rpm --install php-5.2.10-1.el5.centos.src.rpm
vi /usr/src/redhat/SPECS/php.spec

Technically, we should edit the release line to reflect the changes we are making, but that creates dependency issues, so we’ll ignore that and edit the configure lines. Scroll to where is says %configure with various includes after the line. Remove the line that says --disable-rpath \ which will stop the compile working (this is PHP bug #48172) and add at the end: --with-t1lib \

Exit insert mode, save and exit (hit Esc, then ZZ). Now rebuild the RPM files:

rpmbuild -bb /usr/src/redhat/SPECS/php.spec

It’s highly likely that you will now get a list of failed dependencies. All of them need to be installed. The following is my list – yours may be different. Su to the root user and install them, then logout back to the admin user after this command:

su -
yum -y --skip-broken install bzip2-devel curl-devel db4-devel expat-devel gmp-devel aspell-devel httpd-devel libjpeg-devel libpng-devel pam-devel libstdc++-devel sqlite-devel pcre-devel readline-devel libtool gcc-c++ libc-client-devel cyrus-sasl-devel openldap-devel postgresql-devel unixODBC-devel libxml2-devel net-snmp-devel libxslt-devel libxml2-devel ncurses-devel gd-devel freetype-devel

Then run the rpmbuild command again. If you get a GD error after the T1_StrError line, try running this command as root:

su -
ldconfig /usr/local/lib

Run the rpmbuild command again (as non-root). When it finishes (will take a while), install the resultant RPM files as root user:

su -
cd /usr/src/redhat/RPMS/x86_64/
rpm -Uhv --nodeps --force *.rpm
service httpd restart

Your path to the RPMs may be different depending on your architecture.

Secure new CentOs install

Step 1: Secure SSH

Log in as root to your server and type the following commands to backup and then edit the SSH configuration:

cp /etc/ssh/ssh_config /etc/ssh/ssh_config.bak; cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak
vi /etc/ssh/ssh_config

Hit the i key to enter insert mode. Then uncomment all the lines after (and including) Host * (i.e. remove the hashes) and change Protocol 2,1 to 2 only. Hit Esc to exit insert mode and type ZZ to quit saving the changes. Then type the following command:

vi /etc/ssh/sshd_config

As before, in insert mode, uncomment the Port, Protocol (and change to 2 only if not already) and ListenAddress statements. Also uncomment and change PermitRootLogin to: no. Quit and save (Esc, ZZ). Then restart the SSH service:

service sshd restart

Since we have now prevented the root user from logging in remotely (as a security measure – the root user has full access to the entire system and can break things very easily), the final step is to create a user who can log in remotely. Type in:

useradd -g wheel admin
passwd admin

Next time when you log in you can switch to the root user using the following command (enter the root password at the prompt):

su -

Step 2: Install ChkRootKit (rootkit finder)

Create a directory to hold downloaded or compiled sofware, then install some tools we will need (these may well already be installed):

mkdir -p ~admin/software
cd ~admin/software
yum -y install gcc make wget vixie-cron perl

Download and install ChkRootKit:

wget ftp://ftp.pangeia.com.br/pub/seg/pac/chkrootkit.tar.gz
tar zxfv chkrootkit.tar.gz
cd chkrootkit-*
make sense

Then add a cron entry to run the script automatically (this is still done as the root user):

crontab -e

Tell it to run every day at 3am and email you the errors – add the following line (use the same commands as when using vim above):

0 3 * * * /home/admin/software/chkrootkit-*/chkrootkit -q 2>&1 | mail -s "ChkRootKit Output from `hostname`" your@email.com

You could do that bit of editing entirely on the command line by creating a temporary file and then adding that to the crontab like this:

touch crontab_temp
crontab -l > crontab_temp
echo "0 3 * * * /home/admin/software/chkrootkit-*/chkrootkit -q 2>&1 | mail -s \"ChkRootKit Output from \`hostname\`\" your@email.com" >> crontab_temp
cat crontab_temp | crontab
rm -f crontab_temp

Step 3: Install Portsentry (check for people sniffing/scanning your ports and block them)

cd ~admin/software

32-bit version – use this if your OS is 32-bit – download and install the existing package:

wget ftp://ftp.pbone.net/mirror/ftp.falsehope.net/home/tengel/centos/4/te/i386/RPMS/portsentry-1.2-1.te.i386.rpm
rpm -Uhv portsentry-1.2-1.te.i386.rpm
/etc/rc.d/init.d/portsentry start
echo "/etc/rc.d/init.d/portsentry" >> /etc/rc.d/rc.local

64-bit version – use this if your OS is 64-bit – we need to compile the original program, but there is an error in one of the files we need to fix first:

wget http://downloads.sourceforge.net/project/sentrytools/portsentry%201.x/portsentry-1.2/portsentry-1.2.tar.gz
tar zxfv portsentry-1.2.tar.gz
cd portsentry_beta
vi portsentry.c

The error is on line 1584 and will prevent the program from compiling. To see line numbers, type in :set number
Find line 1584 and remove the line break in the middle of that sentence. Then install:

make linux
make install

Next we need to create a script to control the service:

vi /etc/init.d/portsentry

Start insert mode and paste this all this into the file (careful of linebreaks – then save and quit):


case "$1" in
echo "Starting Portsentry..."
ps ax | grep -iw '/usr/local/psionic/portsentry/portsentry -atcp' | grep -iv 'grep' > /dev/null
if [ $? != 0 ]; then
/usr/local/psionic/portsentry/portsentry -atcp
ps ax | grep -iw '/usr/local/psionic/portsentry/portsentry -audp' | grep -iv 'grep' > /dev/null
if [ $? != 0 ]; then
/usr/local/psionic/portsentry/portsentry -audp
echo "Portsentry is now up and running!"
echo "Shutting down Portsentry..."
array=(`ps ax | grep -iw '/usr/local/psionic/portsentry/portsentry' | grep -iv 'grep' \
| awk '{print $1}' | cut -f1 -d/ | tr '\n' ' '`)
while [ "$index" -lt "$element_count" ]
kill -9 ${array[$index]}
let "index = $index + 1"
echo "Portsentry stopped!"
$0 stop && sleep 3
$0 start
echo "Usage: $0 {start|stop|restart}"
exit 1
exit 0

Then we need to make that script executable, add portsentry to the startup scripts and start it up:

chmod 755 /etc/init.d/portsentry
ln -s /etc/init.d/portsentry /etc/rc2.d/S20portsentry
ln -s /etc/init.d/portsentry /etc/rc3.d/S20portsentry
ln -s /etc/init.d/portsentry /etc/rc4.d/S20portsentry
ln -s /etc/init.d/portsentry /etc/rc5.d/S20portsentry
ln -s /etc/init.d/portsentry /etc/rc0.d/K20portsentry
ln -s /etc/init.d/portsentry /etc/rc1.d/K20portsentry
ln -s /etc/init.d/portsentry /etc/rc6.d/K20portsentry
/etc/init.d/portsentry start

Step 4: Install LibSafe (prevents buffer overflow exploits)

cd ~admin/software

Download for 32-bit:

wget http://pubs.research.avayalabs.com/src/libsafe-2.0-16.i386.rpm

Or for 64-bit:

wget ftp://ftp.pbone.net/mirror/archive.fedoraproject.org/fedora/linux/extras/3/x86_64/libsafe-2.0-16.fdr.1.rh80.x86_64.rpm

Then install:

rpm -Uhv libsafe-2.0-16*.rpm

Step 5: Install Hogwash (inline packet scrubber)

Download, install and configure Hogwash:

cd ~admin/software
wget http://hogwash.sourceforge.net/devel-0.5-latest.tgz
tar zxfv devel-0.5-latest.tgz
cd distro/devel-0.5/devel-0.5
cp hogwash /sbin
mkdir /var/log/hogwash
mkdir /etc/hogwash
cd rules
cp *.rules /etc/hogwash
cd ..
cp *.config /etc/hogwash
cp /etc/hogwash/stock.config /etc/hogwash/live.config

We need to create another control script, but we can do this on the command line:

touch Hog
echo '#!/bin/sh' >> Hog # needs single quotes
echo "#chkconfig: 2345 11 89" >> Hog
echo "#description: Automates Hogwash packet filter" >> Hog
echo "/sbin/hogwash -d -c /etc/hogwash/live.config -r /etc/hogwash/live.rules -l /var/log/hogwash" >> Hog
chmod 700 Hog

Make sure it starts at boot time:

cp Hog /etc/rc.d/init.d
chkconfig --add Hog

Step 6: Install DenyHosts (blocks brute force login attempts)

cd ~admin/software

Install the RPMForge repo – for 32-bit:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.1-1.el5.rf.i386.rpm

Or for 64-bit:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.1-1.el5.rf.x86_64.rpm

Install, configure and make sure your own address is not blocked (substitute your IP address in the code below)

rpm -i rpmforge-release-0.5.1-1.el5.rf.*.rpm
yum check-update
yum -y install denyhosts
echo "sshd:" >> /etc/hosts.allow
perl -pi -e "s/PURGE_DENY =/PURGE_DENY = 7d/g;" /etc/denyhosts/denyhosts.cfg
chkconfig denyhosts on
service denyhosts start

Step 7: Install RootKit Hunter (yes, another one)

Download and configure RkHunter, then set up the cronjob to execute automatically (as above) and email you if there are warnings:

yum -y install rkhunter
cd ~admin/software
perl -pi -e "s/MAIL-ON-WARNING=\"\"/MAIL-ON-WARNING=\"your\@email.com\"/g;" /etc/rkhunter.conf
touch crontab_temp
crontab -l > crontab_temp
echo "0 4 * * * /usr/bin/rkhunter --cronjob 2>&1" >> crontab_temp
echo "@monthly /usr/bin/rkhunter --update" >> crontab_temp
cat crontab_temp | crontab
rm -f crontab_temp


There are a couple of other things I always do when setting up a server.

• Disable the weak ciphers in the SSH server:
sshd -T | grep ciphers | sed -e "s/\(3des-cbc\|aes128-cbc\|aes192-cbc\|aes256-cbc\|arcfour\|arcfour128\|arcfour256\|blowfish-cbc\|cast128-cbc\|rijndael-cbc@lysator.liu.se\)\,\?//g" >> /etc/ssh/sshd_config
service sshd restart

• Disable Apache mod_status (see httpd.conf or 00-base.conf in /etc/httpd/conf/)
• Turn off TRACK|TRACE in Apache:
echo "TraceEnable Off" >> /etc/httpd/conf/httpd.conf
service httpd reload

• If Webmin is installed tweak the SSL Options and only allow the following ciphers: ALL:!ADH:!LOW:!MEDIUM:!SSLv2:!EXP:+HIGH