The Most Common OpenSSL Commands

One of the most versatile SSL tools is OpenSSL which is an open source implementation of the SSL protocol. There are versions of OpenSSL for nearly every platform, including Windows, Linux, and Mac OS X. OpenSSL is commonly used to create the CSR and private key for many different platforms, including Apache. However, it also has hundreds of different functions that allow you to view the details of a CSR or certificate, compare an MD5 hash of the certificate and private key (to make sure they match), verify that a certificate is installed properly on any website, and convert the certificate to a different format.

Continua”The Most Common OpenSSL Commands”

This week we had a major problem with one of our webserver. A roge IP address in Asia was sending hundreds of requests to our search page on our site. The UserAgent showed Mozilla but this could’ve been software that faked the user agent.

Basically these requests overwhelmed Apache and the server load got as hight as 150. I was able to parse the log files in apache and noticed the multiple connections coming from the IP address that I had already found using Netstat.

I firewalled the IP address and that solved the issue but I wanted to find a way to stop these attacks automatically.

I found this cool entry using google and here is a good idea that I am going to try to implement to stop these attacks.

It uses Ruby on Rails but I can use PHP and then use Bash to automatically firewall these IP addresses.

Continua”A Cool Idea to Stop Bad Robots Attacking Your Webserver”

# ELITE HTACCESS FOR WEBDEVELOPERS
##############################################
AuthName “SiteName Administration”
AuthUserFile /home/sitename.com/.htpasswd
AuthType basic
Require valid-user
Order deny,allow
Deny from all
Allow from 24\.205\.23\.222
Allow from w3.org htmlhelp.com
Allow from googlebot.com
Satisfy Any
Each code snippet has been copied from htaccesselite. Additional and detailed info on each htaccess code snippet can be found at askapache.com

NOTE: Most of these snippets can be used with a Files or Filesmatch directive to only apply to certain files.

NOTE: Any htaccess rewrite examples should always begin with:

Continua”Elite htaccess hacks”

Yesterday I wrote about increasing local port range with net.ipv4.ip_local_port_range proc file. There is also /proc/sys/kernel/pid_max file, which specifies the value at which PIDs wrap around (i.e., the value in this file is one greater than the maximum PID). The default value for this file, 32768, results in the same range of PIDs as on earlier kernels (<=2.4). The value in this file can be set to any value up to 2^22 (PID_MAX_LIMIT, approximately 4 million).

Increasing the value will help on large Linux system or clusters to ease process identification and process management. You can easily prevent fork() failures error message with this hack.
Display Current Process Identifiers Limit
Type the following command at shell prompt:

$ sysctl kernel.pid_max

OR

$ cat /proc/sys/kernel/pid_max

Output:
kernel.pid_max = 32768

Allow for more PIDs
Type the following command

# sysctl -w kernel.pid_max=4194303
You need to append the following to your /etc/sysctl.conf:
kernel.pid_max = 4194303

Please note that this hack is only useful for large and busy server, don’t try this on old kernel or desktop systems.

This is a good table that tells you the differences between all the redhat versions.
good for job interviews.