Sunday, May 15, 2011

Appache server en security

Some hints and tips on security issues in setting up a web server. Some of the suggestions will be general, others specific to Apache.

■ Keep up to Date
The Apache HTTP Server has a good record for security and a developer community highly concerned about security issues. But it is inevitable that some problems -- small or large -- will be discovered in software after it is released. For this reason, it is crucial to keep aware of updates to the software. If you have obtained your version of the HTTP Server directly from Apache, we highly recommend you subscribe to the Apache HTTP Server Announcements List where you can keep informed of new releases and security updates. Similar services are available from most third-party distributors of Apache software.

Of course, most times that a web server is compromised, it is not because of problems in the HTTP Server code. Rather, it comes from problems in add-on code, CGI scripts, or the underlying Operating System. You must therefore stay aware of problems and updates with all the software on your system.

Permissions on ServerRoot Directories
In typical operation, Apache is started by the root user, and it switches to the user defined by the User directive to serve hits. As is the case with any command that root executes, you must take care that it is protected from modification by non-root users. Not only must the files themselves be writeable only by root, but so must the directories, and parents of all directories. For example, if you choose to place ServerRoot in /usr/local/apache then it is suggested that you create that directory as root, with commands like these:

mkdir /usr/local/apache
cd /usr/local/apache
mkdir bin conf logs
chown 0 . bin conf logs
chgrp 0 . bin conf logs
chmod 755 . bin conf logs

It is assumed that /, /usr, and /usr/local are only modifiable by root. When you install the httpd executable, you should ensure that it is similarly protected:

cp httpd /usr/local/apache/bin
chown 0 /usr/local/apache/bin/httpd
chgrp 0 /usr/local/apache/bin/httpd
chmod 511 /usr/local/apache/bin/httpd

You can create an htdocs subdirectory which is modifiable by other users -- since root never executes any files out of there, and shouldn't be creating files in there.

If you allow non-root users to modify any files that root either executes or writes on then you open your system to root compromises. For example, someone could replace the httpd binary so that the next time you start it, it will execute some arbitrary code. If the logs directory is writeable (by a non-root user), someone could replace a log file with a symlink to some other system file, and then root might overwrite that file with arbitrary data. If the log files themselves are writeable (by a non-root user), then someone may be able to overwrite the log itself with bogus data.

Server Side Includes
Server Side Includes (SSI) present a server administrator with several potential security risks.

The first risk is the increased load on the server. All SSI-enabled files have to be parsed by Apache, whether or not there are any SSI directives included within the files. While this load increase is minor, in a shared server environment it can become significant.

SSI files also pose the same risks that are associated with CGI scripts in general. Using the exec cmd element, SSI-enabled files can execute any CGI script or program under the permissions of the user and group Apache runs as, as configured in httpd.conf.

There are ways to enhance the security of SSI files while still taking advantage of the benefits they provide.

To isolate the damage a wayward SSI file can cause, a server administrator can enable suexec as described in the CGI in General section.

Enabling SSI for files with .html or .htm extensions can be dangerous. This is especially true in a shared, or high traffic, server environment. SSI-enabled files should have a separate extension, such as the conventional .shtml. This helps keep server load at a minimum and allows for easier management of risk.

Another solution is to disable the ability to run scripts and programs from SSI pages. To do this replace Includes with IncludesNOEXEC in the Options directive. Note that users may still use <--#include virtual="..." --> to execute CGI scripts if these scripts are in directories designated by a ScriptAlias directive.

CGI in General
First of all, you always have to remember that you must trust the writers of the CGI scripts/programs or your ability to spot potential security holes in CGI, whether they were deliberate or accidental. CGI scripts can run essentially arbitrary commands on your system with the permissions of the web server user and can therefore be extremely dangerous if they are not carefully checked.

All the CGI scripts will run as the same user, so they have potential to conflict (accidentally or deliberately) with other scripts e.g. User A hates User B, so he writes a script to trash User B's CGI database. One program which can be used to allow scripts to run as different users is suEXEC which is included with Apache as of 1.2 and is called from special hooks in the Apache server code. Another popular way of doing this is with CGIWrap.

Non Script Aliased CGI
Allowing users to execute CGI scripts in any directory should only be considered if:

•You trust your users not to write scripts which will deliberately or accidentally expose your system to an attack.
•You consider security at your site to be so feeble in other areas, as to make one more potential hole irrelevant.
•You have no users, and nobody ever visits your server.
Script Aliased CGI
Limiting CGI to special directories gives the admin control over what goes into those directories. This is inevitably more secure than non script aliased CGI, but only if users with write access to the directories are trusted or the admin is willing to test each new CGI script/program for potential security holes.

Most sites choose this option over the non script aliased CGI approach.

Other sources of dynamic content
Embedded scripting options which run as part of the server itself, such as mod_php, mod_perl, mod_tcl, and mod_python, run under the identity of the server itself (see the User directive), and therefore scripts executed by these engines potentially can access anything the server user can. Some scripting engines may provide restrictions, but it is better to be safe and assume not.

Protecting System Settings
To run a really tight ship, you'll want to stop users from setting up .htaccess files which can override security features you've configured. Here's one way to do it.

In the server configuration file, put

AllowOverride None

This prevents the use of .htaccess files in all directories apart from those specifically enabled.

Protect Server Files by Default
One aspect of Apache which is occasionally misunderstood is the feature of default access. That is, unless you take steps to change it, if the server can find its way to a file through normal URL mapping rules, it can serve it to clients.

For instance, consider the following example:

# cd /; ln -s / public_html
Accessing http://localhost/~root/

This would allow clients to walk through the entire filesystem. To work around this, add the following block to your server's configuration:

Order Deny,Allow
Deny from all

This will forbid default access to filesystem locations. Add appropriate Directory blocks to allow access only in those areas you wish. For example,

Order Deny,Allow
Allow from all

Order Deny,Allow
Allow from all

Pay particular attention to the interactions of Location and Directory directives; for instance, even if denies access, a directive might overturn it.

Also be wary of playing games with the UserDir directive; setting it to something like ./ would have the same effect, for root, as the first example above. If you are using Apache 1.3 or above, we strongly recommend that you include the following line in your server configuration files:

UserDir disabled root

Watching Your Logs
To keep up-to-date with what is actually going on against your server you have to check the Log Files. Even though the log files only reports what has already happened, they will give you some understanding of what attacks is thrown against the server and allow you to check if the necessary level of security is present.

A couple of examples:

grep -c "/jsp/source.jsp?/jsp/ /jsp/source.jsp??" access_log
grep "client denied" error_log | tail -n 10

The first example will list the number of attacks trying to exploit the Apache Tomcat Source.JSP Malformed Request Information Disclosure Vulnerability, the second example will list the ten last denied clients, for example:

[Thu Jul 11 17:18:39 2002] [error] [client] client denied by server configuration: /usr/local/apache/htdocs/.htpasswd

As you can see, the log files only report what already has happened, so if the client had been able to access the .htpasswd file you would have seen something similar to: - - [12/Jul/2002:01:59:13 +0200] "GET /.htpasswd HTTP/1.1"

in your Access Log. This means you probably commented out the following in your server configuration file:

Order allow,deny
Deny from all

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Copyright 2011 The Apache Software Foundation.
Licensed under the Apache License, Version 2

Wednesday, May 4, 2011

Data Breaches: 3 Lessons for Leaders

Healthcare Information Security ArticlesMay 4, 2011 - Upasana Gupta, Contributing Editor

In March, RSA, a trusted name in the security industry, suffered a major security breach of its SecurID product, proving that no organization is immune to such incidents.
Then, in April, the Epsilon e-mail breach exposed the risks of data security managed by a third-party service provider.

Two weeks later, Sony Corp announced that hackers had stolen names, addresses and possibly credit card details from 77 million user accounts of its PlayStation Network and Qriocity online service.

RSA, Epsilon and Sony: Three major security incidents that dominated the headlines and sent ripples throughout security organizations worldwide.

No one feels the pressure of such breaches more than the chief information security officer, who ultimately is responsible for protecting and securing the organization. How an organization plans for and responds to such incidents can make or break a CISO's career.

In the wake of these three high-profile breaches, we spoke to two global information security leaders -- Alessandro Moretti, executive director of IT security risk management at UBS Investment Bank, and Abbas Kudrati, head of information risk and security director for the kingdom of Bahrain -- and asked for their biggest lessons learned. Here's what they shared. [For more on leadership and incident response, see Why CISOs Must Care About Sony Breach.]

#1: Build Trust with Senior Management
An incident as significant as the RSA breach requires leaders to be agile and have the ability to redirect investment, projects and security controls within the shortest possible time if needed, says Moretti. This transition can only happen when IT security leaders have built trust with the business owners by establishing an open line of communication in which they discuss pervasive and forward- thinking issues on a continuous basis. Example: how to respond to unique events such as the recent Japanese earthquake or the RSA breach. Moretti picks up the phone and speaks with his executives at the bank as often as needed, bringing to their attention the risks, investment and options to be pursued within the threat landscape. "Leaders have to focus on how they get information across to senior management to do something more proactive," he says.
#2: Enhance Security Awareness
These high-profile breaches have reinforced the need for comprehensive employee training programs designed to help organizations build a more security conscious workforce. "It is still a big challenge for most organizations to implement a thorough security awareness program in their companies, as they lack insight into employee behavior and where, what and how to protect their information assets," says Kudrati. "This means awareness remains low, understanding of the risks stays incomplete, risk is not properly assessed, and the need for regulation is not created."
His response to these incidents has been to initiate a detailed awareness program, including providing the necessary education and tools to employees for a heightened awareness of corporate policies, procedures and guidelines; customizing email policy for different departments based on usage; conducting frequent social engineering and anti-phishing exercises to enable employees to carefully consider the security implications of their online activities. He also has automated regular checks on technical controls, infrastructure and internal vulnerabilities, allowing the organization to reduce the risk of exposing sensitive information and ultimately strengthening the risk management and data loss prevention policies.

"We are working progressively in reducing risks by pushing the basics, expanding our knowledge of threats and vulnerabilities and educating our employees," Kudrati says.

#3: Manage Risk with Vendors
IT security leaders can no longer just focus on controls and contracts in dealing with vendors that provide software, applications, network and core infrastructure solutions. Leaders have to ensure that "vendor management is built into the risk framework, so these providers know what risks they are managing for you," Moretti says. One must categorize vendors before assessing vendor risk, as not all service providers are the same. Also, IT leaders need to ensure they have a contingency plan in place to support their business should the worst happen to the vendor supporting their mission-critical systems and infrastructure .
Moretti says he has changed his attitude from a control mindset and instead works with vendors as partners of the organization in making them understand the impact of managing risks. The dialogue is now on risk management and mitigation.

Ultimately, Moretti says, "A leader's passive attitude to a security incident outside of their organization is no longer acceptable."