Click here to close now.

Welcome!

You will be redirected in 30 seconds or close now.

ColdFusion Authors: Yakov Fain, Maureen O'Gara, Nancy Y. Nee, Tad Anderson, Daniel Kaar

Related Topics: ColdFusion

ColdFusion: Article

Toward Better Error Handling

Toward Better Error Handling

We've all seen it: the dreaded "Error Occurred While Processing Request," which is the headline above a normal CF error message. As developers, of course, we relish the detail it offers: the CF error message, the line number and actual line of code in error, the name and path of the template in which it occurred, and so on. But is this the best thing to show our end users?

Probably not. What should they do with that information? Do they care about these details? Could a hacker use them for unintended purposes? And perhaps most important, how do you even know the error has occurred?

Several features - some old, some new in 4.5, but in either case often missed and misunderstood - can dramatically improve error handling in ColdFusion. In this series of articles I'll cover the basic solutions, CFTRY/CFCATCH, CFERROR (three forms of it) and Site Wide Error Handling, which may be new to you.

In this issue, though, we'll focus on some administrator settings that you may not have considered and that may be quite important to any effective error-handling strategy, depending on the other error-handling choices you make. I'll show how you can reduce the level of detail offered in error messages, as well as improve the ease with which errors may be reported to you when they occur. Along the way I'm confident even the most experienced CF coder will learn a thing or two as some aspects of these features are poorly documented and not obvious.

I'll discuss those other error-handling choices (CFTRY/CFCATCH, CFERROR, and Site Wide Error Handling) in forthcoming issues of CFDJ, and at the end I'll offer a clear list of things you should be doing to better handle errors in your applications.

By applying even one of these solutions, with just a few minutes work (or seconds, in some cases) you could dramatically improve not only your end users' experience, but also the security of your site and your awareness of errors that occur in your applications.

That Lovable, If Pesky, Error Message
The standard CF error message is a delight to the CF developer, with all that great detail. And if it's a SQL error, we even see the database error message, the name of the datasource in error and the SQL statement that was attempted. This is just great for debugging. An example is shown in Figure 1.

Clearly, the creators of CF were developers at heart and realized we'd need to see that info to solve problems. Quick Tip: When you get an error, do you jump back into the code and try to find and fix it? Most developers seem to...and fail to take full advantage of the text of the message. In some cases, though (see Figure 1), what's wrong isn't always obvious.

Even then, if you hop back into the code to scroll around looking for the line of code in error, you're missing a useful shortcut. Notice the line number that's offered (line 79 in this example). In Studio, type CTRL-G (or Edit>GoTo Line) to jump to that line of code. It's not a perfect solution, however; if you have any CFINCLUDEs above the line in error, the numbers in the Studio won't be in sync with the one reported in the error.

This detail is great for developers, but when you move your code to a production environment or, more simply, when an end user visits the site, is that error message an appropriate thing to offer them?

Is It the Right Thing for End Users?
There are several problems with letting users see an error message. First, of course, there's the compromise such errors make to your otherwise elegant user interface. How does it look when they go from your site's consistently blue background to the plain white CF error message page? And what are they going to do with this information? And again, how do you know the error has occurred for your users? Do you simply wait for a call and report it? And have you considered the security risks of showing the physical path of your templates and the SQL datasource name and statements of failed queries in this error message to users?

If you're like many CF developers, these are things you probably haven't thought about, or simply didn't know how to solve. As of Release 4.5, there are a host of options you can consider to limit, modify or hide the error message users see. You can even arrange to log the errors in a database and/or send your developers an e-mail indicating that an error has occurred.

But these enhancements generally require programming changes. We want to start off with some quick changes that can be made to assist the user in informing you that an error has occurred, as well as limiting what information is displayed.

Administrator Configuration Changes
In this article we'll consider three changes that can be made in the CF Administrator. They'll have an important impact on the information presented (or hidden) in the traditional CF error message.

Subsequent issues will cover modifying or completely hiding the display of the message as well as logging/e-mailing it to you automatically, with new "error-handling templates."

But even with those in place if you have them (or until we cover them next month), the changes discussed below have benefits. They'll improve both the ease of users reporting an error as well as the security of your site - especially if you won't be implementing error-handling templates.

The issues we'll cover are setting the administrator e-mail, hiding the SQL and datasource name for query errors, and hiding the template path to the template in error. Even if you think you understand these options, there's more to them than is documented. Let's look at them in detail.

Defining the Administrator E-Mail Error-Handling Address
Some experienced developers may be surprised by my pointing this out, but it's one of the simplest improvements you can make, in the right circumstances, and it's easily implemented.

In the CF Administrator there's a place where you can define the administrator e-mail address for the server:

  • Take the "settings" link under the Logging area on the left nav bar.
  • Enter an e-mail address that should receive e-mails sent by users choosing an option that will be presented to them to send such messages.
Entering this address will from then on cause an additional line of display to be shown on the standard CF error page (the traditional unformatted one), at the bottom of the screen:

Please inform the site administrator that this error has occurred (be sure to include the contents of this page in your message to the administrator).

The "site administrator" link will now hold a hyperlink that when clicked will indicate to the browser that a mail message should be created to be sent to the e-mail address specified in that Administrator setting. (If the user's browser and e-mail client are properly configured to respond to such e-mail hyperlinks, the client's e-mail program will launch an e-mail message to the specified address - and the user can choose to fill in the subject and body of the message.)

Of course, we still have to hope they pay attention to the error message that states they should "include the contents of this page" in the message they send. And it's important to note that this doesn't mean that the "administrator e-mail" address will receive notification of every error that occurs - only when end users click the link offered in that message above. That's something we'll enable in the next issue.

Not Enough, But a Good First Step
This still doesn't solve the other problems of the less-than-attractive interface of the error message or getting an automatic notification. But it's a step in the right direction and, unless you're in a shared server environment where no one person is a suitable recipient of all notifications about error messages, it's probably the first thing you ought to do. (Just be sure to change that administrator setting should that person ever change or leave, lest messages be sent to someone who'll never get them.)

It's also useful when you do use site-wide error handling, as it becomes a variable you can refer to in the site-wide error template, covered next month.

Hiding the SQL and Datasource Name, and Template Path
I've already mentioned the potential security risk of showing the end user such details as the path to the template in error and the SQL code and datasource name in failed queries. In the next article I'll show how you can hide the entire error message from the user, so this point about hiding certain details of the message may become moot if you apply the other techniques. But it's important to understand, especially if you're not currently aware of the issue and may not soon implement those other techniques.

The Risk
Let's look closely at the information shown in the normal CF error message, focusing just on the SQL and Datasource name of a failed query, and the path to the template in error (see Figure 1).

Could someone take advantage of knowing your Datasource name (SomeDSN, in the example) and the SQL code of the failed queries? Or the template path (C:\INETPUB\WWWROOT\SOMEDIR\) to the page in error?

Well, perhaps not if they're just a user of your Web site. Of course, if such a user could break in, they could certainly take advantage of the information. But such break-ins are unlikely, or at least well beyond the scope of this article.

But what if you're on a shared Web server with others who aren't related to your application but can also put CF code on the server in other directories? This is certainly an issue in a commercially hosted Web site on a server shared by many users. It's also a possible concern for users on a corporate Web site having multiple unrelated applications. (One solution to this problem is to use CF's Advanced Security, but this isn't a trivial exercise and is beyond the scope of this article.)

As for the SQL and Datasource Name, if someone can place CF code on the same server as you, have you considered the risk to your data if he or she knew the datasource name for your database? What's to stop someone from running a query against your database? If you're not password protecting your database, any CF template that's running on that same CF server can write a query against your datasource. Password protecting the file may be trivial or challenging in your environment, but explaining it is a subject for another article.

There is yet another risk, as described in Allaire Security Bulletins ASB99-04 and ASB99-09. It's possible in some situations (if not otherwise protected using the suggestions in the bulletins) for a Web visitor to append to the end of a URL (in certain rather unusual situations) extra SQL commands to be executed against your database. This isn't really a CF bug but rather a database driver issue.

In both these cases, if someone can see the SQL statements (including table and column names) shown in an error message, that makes it all the easier to take advantage of any security hole or weaknesses in your environment. So let's hide that information.

Hiding the SQL and Datasource Name in Query Errors
The good news is that it's easy to stop that information from showing in the standard error message (or the one available for display as a variable in one of the error-handling template approaches, discussed in the next issue). It's just a simple tick of a checkbox in the CF Administrator.

It may not be so easy to find, however. It's presented along with server-side debugging control options:

  • Take the "debugging" link under the Miscellaneous area on the left nav bar.
  • Make sure "Show SQL and data source name" is unchecked.
Doing this will reduce the amount of detail in the message above by removing the lines:

SQL = "select * from jobs where jobs.companyid = 499 and jobs.composite_ad_yn <> 1 and jobs.jobtitleid = jobtitles.jobtitleid and jobs.cityid = val_cities.cityid order by stateid,city, jobtitle, date_posted desc" Data Source = "SomeDSN"

That's another step in the right direction.
Now you might be worried about the loss of this useful information as a developer, but there's good news.

Interesting Behavior That May Confuse You
The text explaining this option in the Administrator screen suggests that it controls display, not only of the Datasource name but the SQL statement in error as well. You may find, however, that after doing this you'll still see the SQL statement in error. Is the feature broken? Will end users still see the SQL statement in error? That depends.

Although it's not documented anywhere, this option behaves in an interesting way, and it explains why this option is on the debugging options page. A user who can see the server-side debugging information will always see the SQL statement in error, regardless of whether the "show SQL and datasource name" is turned off.

This is a nice feature for developers as it gives them the detail they need. It's likely that you don't show end users the debugging information, so this makes it really safe to turn off the display of the SQL statement. Those who shouldn't see it won't, while those who should, will.

Hiding the Template Path
The security concerns don't stop there. Remember that display in the error message of the physical path to the template in error? That can also be used by hackers, or simply by others not associated with your project but located on the same server. A few tags available in CF, such as CFFILE and CFCONTENT, allow access to any file in the CF server.

The error occurred while processing an element with a general identifier of (CFQUERY), occupying document position (26:5) to (26:59).

If someone running code on your server (again, someone who has access to the server or, less likely, someone who's broken in) knows where your code resides, that person can use those tags to grab your source code...or possibly your database.

There are two broader solutions to that problem: one is to restrict access to those tags in the Administrator, which is an option under "Basic Security." Or you can configure Advanced Security, mentioned previously, to protect directories from access by other developers on the same server.

Beyond those security approaches, you can also lessen the risk caused by error messages showing the template path by simply preventing its display in the standard CF error message. Like the "SQL and Datasource Name" option, it too is embedded, curiously, among the server-side debugging control options:

  • Take the "debugging" link under the Miscellaneous area on the left nav bar.
  • Make sure "Display the template path in error messages" is unchecked.
Doing this, along with the SQL and Datasource Name option, will reduce the message detail by changing the last line in the message to:

The specific sequence of files included or processed is:
C:\inetpub\wwwroot\somedir\sometemplate.cfm

Additional Observations
Sadly, this option doesn't respond the way the SQL and Datasource Name option does: even if you're authorized to see server-side debugging information, once this option is turned on, the template name and path will no longer be displayed in error messages. This will make it a little harder for a developer to determine a template in error.

If you have development and production environments, it's certainly worth considering whether you really want to use this option to hide the template path in the development environment.

Some errors (unless otherwise handled by error-handling strategies to be discussed in the next issue) will still show the template path anyway. Compilation errors are an example. Consider this example: turn off the display of the template path and run a template with the code:

Cfif></cfif>

This compilation error will display the complete path in the error message, after the details about the compilation error itself, as in:

This doesn't happen in all classes of errors, but it's something to keep in mind.

Conclusion
We've covered a lot of ground, and hopefully you've learned some things about configuring the Administrator to improve error handling.

Next month I'll explain further the opportunity to have even greater control over the display of errors, or hide them entirely and simply e-mail them automatically to a support person with no interaction by the user, or perhaps even log them to a database. I'll provide two of the three alternatives: Site Wide Error Handling (new to 4.5) and application-level error handling (which has changed significantly in 4.5). In the final part I'll cover CFTRY and CFCATCH, which offer even finer levels of control over error handling within your code.

As for the recommendations to take from this article, consider the following as a summary of the Administrator changes available to you:

  • Set the Administrator e-mail address (if you're on a server where all the applications are related and one person is appropriately ready to handle all such messages).
  • Turn off the display of the Datasource Name and SQL for queries in error, and the template path to the template in error, in anything other than a pure testing/development environment.
As for some of the security best practices we alluded to:
  • Password protect your databases (even in Access) so users running code on a shared server with you need more than just the datasource name and knowledge of your tables and column names to access your data.
  • Read the two Allaire security bulletins about further protecting your data from end users who might be able to take advantage of certain security issues in some database drivers and with some templates.
  • Consider the "Tag Restriction" options in the Administrator to further prevent the likelihood of abuse among unrelated developers on a shared server.
  • Set the Administrator debugging options to prevent server-side debug information from showing to your users, which allows the hide "SQL and Datasource Name" option described above to indeed hide the SQL in error.
For all these options, see the Allaire documentation for more information. All the administrator configuration options presented in this article are discussed in the manual Administering ColdFusion Server.

More Stories By Charlie Arehart

A veteran ColdFusion developer since 1997, Charlie Arehart is a long-time contributor to the community and a recognized Adobe Community Expert. He's a certified Advanced CF Developer and Instructor for CF 4/5/6/7 and served as tech editor of CFDJ until 2003. Now an independent contractor (carehart.org) living in Alpharetta, GA, Charlie provides high-level troubleshooting/tuning assistance and training/mentoring for CF teams. He helps run the Online ColdFusion Meetup (coldfusionmeetup.com, an online CF user group), is a contributor to the CF8 WACK books by Ben Forta, and is frequently invited to speak at developer conferences and user groups worldwide.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at @ThingsExpo, James Kirkland, Red Hat's Chief Architect for the Internet of Things and Intelligent Systems, described how to revolutionize your archit...
SYS-CON Events announced today that Dyn, the worldwide leader in Internet Performance, will exhibit at SYS-CON's 17th International Cloud Expo®, which will take place on November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Dyn is a cloud-based Internet Performance company. Dyn helps companies monitor, control, and optimize online infrastructure for an exceptional end-user experience. Through a world-class network and unrivaled, objective intelligence into Internet conditions, Dyn ensures traffic gets delivered faster, safer, and more reliably than ever.
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo in Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal an...
To many people, IoT is a buzzword whose value is not understood. Many people think IoT is all about wearables and home automation. In his session at @ThingsExpo, Mike Kavis, Vice President & Principal Cloud Architect at Cloud Technology Partners, discussed some incredible game-changing use cases and how they are transforming industries like agriculture, manufacturing, health care, and smart cities. He will discuss cool technologies like smart dust, robotics, smart labels, and much more. Prepare to be blown away with a glimpse of the future.
"We have a tagline - "Power in the API Economy." What that means is everything that is built in applications and connected applications is done through APIs," explained Roberto Medrano, Executive Vice President at Akana, in this SYS-CON.tv interview at 16th Cloud Expo, held June 9-11, 2015, at the Javits Center in New York City.
WebRTC converts the entire network into a ubiquitous communications cloud thereby connecting anytime, anywhere through any point. In his session at WebRTC Summit,, Mark Castleman, EIR at Bell Labs and Head of Future X Labs, will discuss how the transformational nature of communications is achieved through the democratizing force of WebRTC. WebRTC is doing for voice what HTML did for web content.
The 17th International Cloud Expo has announced that its Call for Papers is open. 17th International Cloud Expo, to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, APM, APIs, Microservices, Security, Big Data, Internet of Things, DevOps and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit your speaking proposal today!
The 5th International DevOps Summit, co-located with 17th International Cloud Expo – being held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA – announces that its Call for Papers is open. Born out of proven success in agile development, cloud computing, and process automation, DevOps is a macro trend you cannot afford to miss. From showcase success stories from early adopters and web-scale businesses, DevOps is expanding to organizations of all sizes, including the world's largest enterprises – and delivering real results. Among the proven benefits, DevOps is corr...
17th Cloud Expo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterprises are using some form of XaaS – software, platform, and infrastructure as a service.
The 4th International Internet of @ThingsExpo, co-located with the 17th International Cloud Expo - to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA - announces that its Call for Papers is open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than
SYS-CON Events announced today that Secure Infrastructure & Services will exhibit at SYS-CON's 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Secure Infrastructure & Services (SIAS) is a managed services provider of cloud computing solutions for the IBM Power Systems market. The company helps mid-market firms built on IBM hardware platforms to deploy new levels of reliable and cost-effective computing and high availability solutions, leveraging the cloud and the benefits of Infrastructure-as-a-Service (IaaS...
SYS-CON Events announced today that ProfitBricks, the provider of painless cloud infrastructure, will exhibit at SYS-CON's 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. ProfitBricks is the IaaS provider that offers a painless cloud experience for all IT users, with no learning curve. ProfitBricks boasts flexible cloud servers and networking, an integrated Data Center Designer tool for visual control over the cloud and the best price/performance value available. ProfitBricks was named one of the coolest Clo...
Internet of Things is moving from being a hype to a reality. Experts estimate that internet connected cars will grow to 152 million, while over 100 million internet connected wireless light bulbs and lamps will be operational by 2020. These and many other intriguing statistics highlight the importance of Internet powered devices and how market penetration is going to multiply many times over in the next few years.
The basic integration architecture, as defined by ESBs, hasn’t changed for more than a decade. Most cloud integration providers still rely on an ESB architecture and their proprietary connectors. As a result, enterprise integration projects suffer from constraints of availability and reliability of these connectors that are not re-usable across other integration vendors. However, the rapid adoption of APIs and almost ubiquitous availability of APIs amongst most SaaS and Cloud applications are rapidly redefining traditional integration approaches and their reliance on proprietary connectors. ...
Today air travel is a minefield of delays, hassles and customer disappointment. Airlines struggle to revitalize the experience. GE and M2Mi will demonstrate practical examples of how IoT solutions are helping airlines bring back personalization, reduce trip time and improve reliability. In their session at @ThingsExpo, Shyam Varan Nath, Principal Architect with GE, and Dr. Sarah Cooper, M2Mi’s VP Business Development and Engineering, will explore the IoT cloud-based platform technologies driving this change including privacy controls, data transparency and integration of real time context wi...
Buzzword alert: Microservices and IoT at a DevOps conference? What could possibly go wrong? In this Power Panel at DevOps Summit, moderated by Jason Bloomberg, the leading expert on architecting agility for the enterprise and president of Intellyx, panelists peeled away the buzz and discuss the important architectural principles behind implementing IoT solutions for the enterprise. As remote IoT devices and sensors become increasingly intelligent, they become part of our distributed cloud environment, and we must architect and code accordingly. At the very least, you'll have no problem fillin...
The Internet of Things is not only adding billions of sensors and billions of terabytes to the Internet. It is also forcing a fundamental change in the way we envision Information Technology. For the first time, more data is being created by devices at the edge of the Internet rather than from centralized systems. What does this mean for today's IT professional? In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists addressed this very serious issue of profound change in the industry.
Internet of Things (IoT) will be a hybrid ecosystem of diverse devices and sensors collaborating with operational and enterprise systems to create the next big application. In their session at @ThingsExpo, Bramh Gupta, founder and CEO of robomq.io, and Fred Yatzeck, principal architect leading product development at robomq.io, discussed how choosing the right middleware and integration strategy from the get-go will enable IoT solution developers to adapt and grow with the industry, while at the same time reduce Time to Market (TTM) by using plug and play capabilities offered by a robust IoT ...
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society-changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his session at @ThingsExpo, Jason Mondanaro, Director, Product Management at Metanga, discussed how you can plan to cooperate, partner, and form lasting all-star teams to change the world and it starts with business models and monetization strategies.
SYS-CON Events announced today that BMC will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. BMC delivers software solutions that help IT transform digital enterprises for the ultimate competitive business advantage. BMC has worked with thousands of leading companies to create and deliver powerful IT management services. From mainframe to cloud to mobile, BMC pairs high-speed digital innovation with robust IT industrialization – allowing customers to provide amazing user experiences with optimized IT per...