Real-World PHP Security
PHP's Safe mode is something you should learn to work with whether you are a PHP developer or a system administrator. Safe mode is a set of configuration options that allow the system administrator to alter the behavior of the PHP interpreter by implementing security measures. From a system administrator's point of view, this means you must learn how to implement this feature properly, without making it impossible for developers to set up their applications on your server. From a developer's point of view, you must learn what possibly could get broken in your application if this feature is turned on.
Turning safe_mode on makes sense if you manage a shared server that serves PHP applications and the PHP developers using this server are not trusted. Enabling safe_mode in your php.ini file effectively makes any file-related operation in any of your scripts impossible unless the UID of the owner of the file is the same as the UID of the running script. PHP also gives you the ability to change this policy while safe_mode is on by turning on the safe_mode_gid option. In this case, PHP checks for the GID of the files you are trying to work with instead of their UID.
It also is good practice to not let your users execute any system binary they want; safe_mode_exec_dir comes into play here. This priceless feature lets you tell PHP not to perform any binary execution, through exec() or any other function, unless the binary is located in the safe_mode_exec_dir, such as /usr/local/php/bin.
Once you have familiarized yourself with the restrictions implemented by PHP when safe_mode is enabled, you should be able to develop software that doesn't break when it's run on servers with this directive enabled. Many ISPs use safe_mode. The simple guidelines to follow are:
Try to limit file operations, whether read or write, to the files you have provided with your application.
Do not rely on external software to be installed or executable by your script unless your project is running on only your servers.
System administrators also have at their disposal other powerful tools to ensure the overall security of their systems. These tools include disable_functions that prevent specified functions from being called, as well as options such as open_basedir, which limit any file operation to a specific directory.
The PHP documentation team has provided an extensive amount of literature on the subject. They also have provided documentation for every aspect of safe_mode and related functions and directives.
Mcrypt Extension: php.net/mcrypt
Mcrypt Project: mcrypt.sf.net
The MVC Paradigm: ootips.org/mvc-pattern.html
PHP Documentation: php.net/manual/en
PHP Security: www.php.net/manual/en/security.index.php
The PHPUnit Project: phpunit.sf.net
The Phrame Project: phrame.sf.net
Safe Mode: www.php.net/manal/en/features.safe-mode.php
Xavier Spriet has been developing software in PHP for the past four years. He is the lead developer at eliquidMEDIA International. You can reach Xavier at email@example.com.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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