Publishers of technology books, eBooks, and videos for creative people

Home > Articles > Web Design & Development > PHP/MySQL/Scripting

Security Techniques

  • Print
  • + Share This
This chapter is from the book

With more and more personal information being stored on the Web—credit card data, social security numbers, maiden names, favorite pets—today's PHP developer cannot afford to be ignorant when it comes to security. Sadly, most beginning programmers fail to understand the truth about security: there is no such thing as "secure" or "insecure." The wise programmer knows that the real question is how secure a site is. Once any piece of data is stored in a database, in a text file, or on a Post-it note in your office, its security is compromised. The focus in this chapter is therefore how to make your applications more secure.

This chapter will begin by rehashing the fundamentals of secure PHP programming. These are the basic things that I hope/assume you're already doing. After that a quick example shows ways to validate different kinds of data that might come from an HTML form. The third topic is the new-to-PHP 5 PECL library called Filter. Its usage isn't very programmer-friendly, but the way it wraps all of the customary data filtering and sanitizing methods into one interface makes it worth knowing. After that, two different uses of the PEAR Auth package show an alternative way to implement authorization in your Web applications. The chapter will conclude with coverage of the MCrypt library, demonstrating how to encrypt and decrypt data.

Remembering the Basics

Before getting into demonstrations of more particular security techniques, I want to take a moment to go over the basics: those fundamental rules that every PHP programmer should abide by all of the time.

To ensure a basic level of security

  1. Do not rely upon register_globals.

    The advent of register_globals once made PHP so easy to use, while also making it less secure (convenience often weakens security). The recommendation is to program as if register_globals is off. This is particularly important because register_globals will likely disappear in future versions of PHP.

  2. Initialize variables prior to using them.

    If register_globals is still enabled—even if you aren't using them—a malicious user could use holes created by noninitialized variables to hack your system. For example:

    if (condition) {
         $auth = TRUE;
    }
    If $auth is not preset to FALSE prior to this code, then a user could easily make themselves authorized by passing $_GET['auth'], $_POST['auth'], or $_COOKIE['auth'] to this script.
  3. Verify and purify all incoming data.

    How you verify and purify the data depends greatly upon the type of data. You'll see many different techniques in this chapter and the book.

  4. Be careful if you use variables for included files.

    If your code does something like

    require($page);

    then you should either make sure that $page does not come from an outside source (like $_GET) or, if it does, that you've made certain that it has an appropriate value. See the technique in Chapter 2, "Developing Web Applications."

  5. Be extra, extra careful when using any function that runs commands on the server.

    This includes eval(), exec(), system(), passthru(), popen(), and the backticks (``). Because each of these runs commands on the server itself, they should never be used casually. And if you must use a variable as part of the command to execute, perform any and all security checks on that variable first. Also use the escapeshellarg() and escapeshellcmd() functions as an extra precaution.

  6. Consider changing the default session directory or using a database to store session data.

    An example as to how you would do this is discussed in Chapter 3, "Advanced Database Concepts."

  7. Do not use browser-supplied filenames for storing uploaded files on the server.

    When you move a file onto your server, rename it to something safe, preferably something not guessable.

  8. Watch for HTML (and more important, JavaScript) in submitted data if it will be redisplayed in a Web page.

    Use the strip_tags() or similar functions to clear HTML and potential JavaScript from submitted text.

  9. Do not reveal PHP errors on live sites.

    One of the most common ways to hack a site is to try to "break" it—do something unexpected to cause errors—in the hopes that the errors reveal important behind-the-scenes information.

  10. Nullify the possibility of SQL injection attacks.

    Use a language-specific database escaping function, like mysqli_real_escape_data(), to ensure that submitted values will not break your queries.

  11. Program with error reporting on its highest level.

    While not strictly a security issue, programming with error reporting on its highest level can often show potential holes in your code.

  12. Never keep phpinfo() scripts on the server.

    Although vital for developing and debugging PHP applications, phpinfo() scripts reveal too much information and are too easily found if left on a live site.

  • + Share This
  • 🔖 Save To Your Account

Peachpit Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Peachpit and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Peachpit products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email ask@peachpit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by Adobe Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.peachpit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020