Robert Cummings wrote:

Michael A. Peters wrote:
Robert Cummings wrote:
Michael A. Peters wrote:
Manuel Aude wrote:
I'm giving a PHP course next semester (3 hours all saturdays for 22 weeks) and I just realized that PHP 5.3 is coming very soon (2 days now!). So, my plans of teaching PHP 5.2 are starting to change, and I think it's a good
idea to teach them 5.3 already.

While the majority of the students use Windows, I'm aware that a vast amount
will be using Ubuntu/Debian (and some use Gentoo, Fedora and Arch)
distributions of Linux, so I'm hoping there won't be too many problems on
installation. I don't want to waste the entire first class fixing
installation problems, because that kills the student's motivation.

The course starts on August, but I'm preparing it during the last two weeks of July. You think that installation packages will be bulletproof by then? Or should I just teach 5.2 and wait for another semester before starting on 5.3? I mean, most hosts will remain with PHP 5.2 for the rest of the year,
so I'm a bit confused on what I should do.

I'm just a university student that wants to spread PHP, for I've been using
it for many years now =)

Thanks for the advices,

Many hosts are still on php 5.1.x (IE RHEL based hosts).
I would be worried that many popular classes and apps might be quirky under 5.3.

I've not played with it at all, and probably won't for some time, but I've been bitten by that more than once.

Nice thing about 5.2.x as far as linux goes anyway, installing it is cake from the package repositories. Using package repositories for php installs is suggested as security fixes can be updated with ease.

As someone running a newer version of php (5.2.9) than what my distro ships with, here are some of the issues:

A) I needed to create packages so that I could RPM install various stuff, like Squirelmail, etc. - and get the security updates for them from my OS vendor (CentOS or EPEL repods). So to do that, I used the Fedora src.rpm.

B) When building php rpm's on my system, the %check portion of the spec file (runs make test I believe) fails sometimes if there is an existing php install. To solve that, you have to build it in mock.

C) Mock needs a lot of disk space and will download a lot of packages, if you don't local mirror the update repositories, it can be really time consuming. Furthermore, occasionally the build list for mock is broken making it un-usable for package building.

I have to use 5.2.x because I need a pecl extension that does not work with 5.1.x - and building rpm myself lets me add suhosin patch (to the fedora spec file) but unless your Linux students want to do absolutely everything php by source and not have anything installed from the package managers that rely on php, I would highly suggest that they use whatever version of php their distro of choice has in its stable repositories.


Since you are teaching students, one pet peeve of mine that I see in web app after web app after web app - they have an admin interface that writes a php file which the app then parses as php. Often they even instruct the person installing the web app to have 777 permissions of directories and/or files within the web root.

There's a better way. Either store the configuration settings in a database (obviously can't store database connection setting in the database ...) or store them in an xml file, not php.

You can write and read the xml file with any number of existing php functions. And the config file should not be in the web root, nothing the web server can write to should be in the document root.

Applications (like Gallery and I think joomla and wordpress) often want write permission to the document root so they can have a web interface to install/update their modules - but it creates a security risk. It's better to install the modules you want from a distro vendor repository so you can keep them up to date that way, and hence, it's better to use a packaged php install so that the dependencies are met.

Sorry for rambling, but the trend of web server having write permissions to files the web server then executes (and often in the web root) is a trend that needs to stop. So flunk the students that do it ;)
And how do you propose people get around open_basedir restrictions which is common in many Plesk environments?

There is nothing wrong with having the above mentioned write access if it is properly protected.

Nothing wrong other than any vulnerability in apache (or a module apache loads or cgi/server script code) that allows a malicious user to write data as the apache user can now do so inside the web root where they can then request it causing php/perl/python/whatever to execute the code they just wrote.

This is fear mongering.

No. It is not.
The web root should be read only.

I could make the same argument that making use of a webserver opens you up to any vulnerability in the webserver that may provide access to the entire filesystem. The intended purpose of the webserver is not to allow such access when configured properly, and so it is an exceptional circumstance when such security is compromised.

These compromises do happen, which is why the web root should be read only to the web server and any data the web server has write access to should be validated before it is used.

It isn't hard to do.

It is common practice to use .htaccess to lock off sensitive areas of a website such as where any writeable documents live. if you set permissions appropriately on the filesystem then the web process should only be able to read those areas where you don't want it to write. Writeable and executable permissions may pose a special problem, but one can merely enable the rights when updating the modules and revoke them afterwards.

Yes you can, but people don't.
You can also have specific directories outside the web root where the web server has write permission for things like file and image uploads, and use a wrapper inside the web root that is used to read and send (and validate when necessary) the data as needed, and avoid the risk of write permission within the web root.

Just as an example, I was looking for a simplistic blog to add to my website. The install script didn't even work because it used system and exec calls which many servers (including mine) do not allow. What it did with those calls is create directories that were 777 permission inside the web root. One directory for flat file comments (odd, as it used MySQL for the actual blog entries, why it didn't have a table for comments I don't understand) and one for images. No validation of the images was done, not even by extension, meaning I could upload evil.php and it would happily upload and be placed inside the web root, allowing me to then call the file from my browser and php would happily execute the code.

Yes, it was crap code, I've now started writing blog software of my own as that seems faster than fixing any of the apps I found - but the reality is that there's a lot of crap code out there, and there's even good code that has vulnerabilities (including binary php modules), so one should have a strict policy of never having directories or files inside the web root that the web server has write permission to.

What if a current (or future) bug in FileInfo exists that allows a carefully crafted file to be reported as a file type it's not? Then even validating the file type could result in arbitrary code on the server that could potentially be executed as part of an attack.

Web server administrators should not allow the web server to have write permission to the web root and web app developers should not instruct the user to install software with write permission in the web root.

Installation of apps may need a slightly more detailed readme and require a few extra install steps, but people who can't read and follow the instructions have no business running a web server, and if the application is good, it will sooner or later be packaged by a quality package repository making secure installation a snap.

Updates to web app modules can be handled by an update manager, such as yum or apt, from a gpg signed package repository.

I don't know what package managers there are for windows, but vast majority of web applications that need module (or core) updates are packaged already for Fedora and Ubuntu and even many for RHEL (in EPEL) in their mainstream repositories, and updating them can even be automated, eliminating the need for manual updates through a web interface that require insecure write permissions and usually do not have any kind of signature checking on what they download and install.


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