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Hacks From Pax:
PHP Web Application Security
By: Pax Dickinson
Today on Hacks From Pax we'll be discussing PHP web application security. PHP is a great language for rapidly developing web applications, and is very friendly to beginning programmers, but some of its design can make it difficult to write web apps that are properly secure. We'll discuss some of the main security "gotchas" when developing PHP web applications, from proper user input sanitization to avoiding SQL injection vulnerabilities.
Many PHP application vulnerabilities are caused by not properly initializing variables. This is an example of how PHP, by not requiring the developer to initialize a variable before using it, sacrifices security for ease of use. For example, the following code is easily exploitable.
if (user_auth()) {
$access = true;
}
if ($access) {
do_sensitive_things();
}
This could be exploited by tacking an ?access=true to the end of the url, and the if ($access) test would be passed despite the user_auth() function returning false. This hole could be closed easily by adding a $access = false; at the top of the script, but not all security holes are this easy to spot.
Thankfully, PHP now defaults the register_globals option to off. This setting would pass the access variable sent by the url to the script as $_GET[access] rather than just $access. This closes off many of these types of vulnerabilities, but when writing PHP code, especially code for distribution, you should never assume that this option will be set correctly, and always initialize your PHP variables. Users in a shared hosting environment may not have the ability to set these options to their most secure setting.
- Always initialize PHP variables before using them.
- Always set register_globals to off, but never write code that assumes this setting.
- You can use the ini_get() function to determine if register_globals is set at runtime.
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Thank you for reading the LinuxSecurity.com weekly security newsletter. The purpose of this document is to provide our readers with a quick summary of each week's most relevant Linux security headline.
| Fedora Core 4 Update: yaboot-1.3.12-10 | ||
4th, August, 2005
Updated package. advisories/fedora/fedora-core-4-update-yaboot-1312-10-11-21-00-120028 |
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| Fedora Core 4 Update: ttmkfdir-3.0.9-16.1 | ||
5th, August, 2005
This update fixes a problem with ttmkfdir not including native encodings of Asian TrueType fonts in fonts.scale files used by the X font server. Users of Chinese, Japanese, and Korean fonts are recommended to reinstall the font packages for these languages after updating ttmkfdir. advisories/fedora/fedora-core-4-update-ttmkfdir-309-161-11-22-00-120037 |
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| Fedora Core 3 Update: ttmkfdir-3.0.9-14.1 | ||
5th, August, 2005
This update fixes a problem with ttmkfdir not including native encodings of Asian TrueType fonts in fonts.scale files used by the X font server. Users of Chinese, Japanese, and Korean fonts are recommended to reinstall the font packages for these languages after updating ttmkfdir. advisories/fedora/fedora-core-3-update-ttmkfdir-309-141-11-22-00-120038 |
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| Fedora Core 4 Update: selinux-policy-targeted-1.25.3-12 | ||
5th, August, 2005
Updated package. advisories/fedora/fedora-core-4-update-selinux-policy-targeted-1253-12-16-38-00-120040 |
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| Gentoo: Netpbm Arbitrary code execution in pstopnm | ||
5th, August, 2005
The pstopnm utility, part of the Netpbm tools, contains a vulnerability which can potentially result in the execution of arbitrary code. |
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| Gentoo: Heartbeat Insecure temporary file creation | ||
7th, August, 2005
Heartbeat is vulnerable to symlink attacks, potentially allowing a local user to overwrite arbitrary files. |
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| RedHat: Moderate: ruby security update | ||
5th, August, 2005
Updated ruby packages that fix an arbitrary command execution issue are now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-ruby-security-update-81302 |
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| RedHat: Moderate: squirrelmail security update | ||
5th, August, 2005
An updated squirrelmail package that fixes two security issues is now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-squirrelmail-security-update-90811 |
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| RedHat: Low: sysreport security update | ||
9th, August, 2005
An updated sysreport package that fixes an insecure temporary file flaw is now available. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-sysreport-security-update-RHSA-2005-598-01 |
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| RedHat: Moderate: xpdf security update | ||
9th, August, 2005
An updated xpdf package that fixes a security issue is now available for Red Hat Enterprise Linux 4. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-xpdf-security-update-RHSA-2005-670-01 |
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| RedHat: Moderate: kdegraphics security update | ||
9th, August, 2005
Updated kdegraphics packages that resolve a security issue in kpdf are now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-kdegraphics-security-update-3388 |
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| RedHat: Important: cups security update | ||
9th, August, 2005
Updated CUPS packages that fix a security issue are now available for Red Hat Enterprise Linux. This update has been rated as having important security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-important-cups-security-update-82866 |
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| RedHat: Low: ucd-snmp security update | ||
9th, August, 2005
Updated ucd-snmp packages that a security issue are now available for Red Hat Enterprise Linux 2.1. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-ucd-snmp-security-update-RHSA-2005-720-01 |
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| RedHat: Critical: gaim security update | ||
10th, August, 2005
An updated gaim package that fixes a buffer overflow security issue is now available. This update has been rated as having critical security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-critical-gaim-security-update-82918 |
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| RedHat: Critical: gaim security update | ||
10th, August, 2005
An updated gaim package that fixes multiple security issues is now available. This update has been rated as having critical security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-critical-gaim-security-update-82918 |
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| RedHat: Moderate: ethereal security update | ||
10th, August, 2005
Updated Ethereal packages that fix various security vulnerabilities are now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-ethereal-security-update-43419 |
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| RedHat: Moderate: gpdf security update | ||
10th, August, 2005
An updated gpdf package that fixes a security issue is now available for Red Hat Enterprise Linux 4. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-gpdf-security-update-RHSA-2005-708-01 |
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