Promising new WIF tools

Vittorio Bertocci has shared some exciting news about the upcoming WIF tools for Visual Studio 11 on his blog. The tools look really nice, especially the local development STS. Here are the direct links (for future reference):

• WIF Tools for Visual Studio 11 Part I: Using The Local Development STS
• WIF Tools for Visual Studio 11 Part II: Manipulating Common WIF Settings From the UI
• WIF Tools for Visual Studio 11 Part III: Connecting With a Business STS (e.g. ADFS2)
• WIF Tools for Visual Studio 11 Part IV: Get an F5 Experience with ACS2

On the blog, you'll also find that the Identity team is hiring. I just checked the list of open positions at Microsoft, and they have 35 (!) open positions on their identity page. I expect we'll see more cool stuff from the identity team in the future!

If you're a .NET developer, now is the time to get on the WIF train. WIF will be an integral part of the .NET framework as of version 4.5, which is currently in beta (for those of us who went all-in on WIF last year, this is quite a relief).

IIS 500 errors leave clues in the log

Yesterday I was playing around with the validateIntegratedModeConfiguration="true" setting on IIS 7.5. To my surprise I got an empty response back, with no indication of what went wrong.

Looking at the response with Fiddler yields:

HTTP/1.1 500 Internal Server Error
Server: Microsoft-IIS/7.5
X-Powered-By: ASP.NET
Date: Mon, 05 Mar 2012 15:59:52 GMT
Content-Length: 0

There's not much to work with here! I checked the event log, there was nothing there. So I started looking around for an error log of some sort (I used to play with Apache back in the days) turns out there's no such thing in IIS.

Some googling led me to an in-depth article: Troubleshoot IIS7 errors like a pro. I enabled detailed error messages for my website, still no luck.

Finally, I figured out that the easiest way to get an indication of what's going on is to check the IIS log. In the default setup, IIS keeps the logs for each website in: C:\inetpub\logs\LogFiles. Here's a log entry from my logfile (shortened for readability):

How to enable WIF token replay detection

Windows Identity Foundation (WIF) is vulnerable to replay of security tokens in its default configuration. The "Replay Detection" article on MSDN presents a good example of how things can go wrong without the replay detection (why do everyone have to use online banking as their example?):

As another example, suppose that a user opens a browser on a public kiosk, logs on to a bank account using the bank’s Web site, logs off and leaves, but does not close the browser. The response to the user’s logon page, which contains the STS token, is still in the browser’s history. Another person could then browse back to that response page and replay it, which would repost the STS token to the bank’s Web site.

This scenario is very much real and it does not involve any fancy hacking techniques. All you need is a browser and a "back" button. You'll find some scattered references on the Internet to the solution of the problem, the tokenReplayDetection configuration setting. You'll find a mention of the configuration element in the WIF FAQ on Technet and in the WIF book, but you'll find the most helpful explanation in the ACS security guidelines.

I'll cut to the chase, here's the config to enable the token replay detection. Please don't use the parameters as is, read the security considerations and tweak the values accordingly. Seriously.

Multiline search and replace in Visual Studio

Today I had to add a new HttpModule to A LOT of web.configs. Adding it manually would be too tedious, so I had to figure out how to search for a single line in Visual Studio 2010 and replace it with two lines of text. If I could only find a way to search for some text, and replace it with several lines of text!

Google turned up some hints about the Regex search, but no apparent solutions. After playing around a bit with the regex search in Visual studio, I found that it supports multiline text in both the search and replace strings.

When you're using "Find and Replace" in Visual Studio you can enable Regular Expressions, under "Find options", as shown in the screenshot. The regular expressions let you represent newlines in the search or replace fields, by using a \n. Cool! I've included an example below the image.

But beware, when you enable regular expressions you need to escape special characters, in my case < and >,  with a backslash. Your "Find" statement will be interpreted as a regular expression. Check out the MSDN page on regular expressions in Visual Studio to learn more about which characters are special and which are not.

Update Sep. 2012: This post deals with Visual Studio 2010. Regular expressions have changed in VS 2012, as you'll see from the link above. See the comments on this post for a new example of multiline search and replace for both VS 2010 and VS 2012.

How not to hash passwords in .NET

In connection with a bug in TransformTool, I've been looking into how text encoding is handled in the .NET framework. Turns out there are some caveats that can affect the correctness of a program, and when used in e.g. password validation they might turn out to be severe security issues.

This post assumes you are somewhat familiar with how character encodings work. You might want to check out my Introduction to character encoding if you're not. I wrote it mainly because I didn't want to explain the basics of encodings in this post.

The encoding issues/features I discuss here are all well documented in the article Character Encoding in the .NET Framework, but I believe that the issues aren't that well known. Stack overflow, blogs, and discussion forums are riddled with insecure code samples. Do a Google search for "ASCII.GetBytes" password, and you'll get a lot of results. I even found insecure code examples in a text book, the C# 2008 Programmer's Reference (page 344). So I definitely believe we need to raise awareness of these issues in the .NET community.

Encoding subtleties
In the MSDN article on character encoding you'll find that the first suggestion on how to use the encoding objects in .NET is: 

Use the static properties of the Encoding class, which return objects that represent the standard character encodings available in the .NET Framework (ASCII, UTF-7, UTF-8, UTF-16, and UTF-32). For example, the Encoding.Unicode property returns a UnicodeEncoding object. Each object uses replacement fallback to handle strings that it cannot encode and bytes that it cannot decode.

And people love to use the static properties! But if you don't read this carefully and pause with the "replacement fallback", you might get into trouble. "Replacement fallback" means that every character that cannot be encoded to bytes will be replaced with the "?" character silently. But what does that mean? Time for a demo using the ASCII encoding:

Introduction to character encoding

"FACE WITH TEARS OF JOY" (U+1F602)

Text encoding is a persistent source of pain and problems, especially when you need to communicate textual information across different systems. Every time you read or create an xml-file, a text file, a web page, or an e-mail, the text is encoded in some way. If the encoding is messed up along the way, the receiver will be looking at strange characters instead of the ori�inal t□xt. (ba-da-bing :)

I've been fighting with characters sets on several occasions throughout the years. Just recently, I had a bug in TransformTool related to character encoding and how errors are handled in the .NET framework. While writing about the bug I needed a reference to a basic introduction to character encoding — only to discover that most are very technically focused and dive right into the characters' hex codes. Here, I'll try to fill that gap and explain only the basics. I'll include pointers to more detailed resources in case you decide to dig deeper into the dark world of character encodings.

How encodings work
The Unicode Consortium has a great explanation of how it really works:

Fundamentally, computers just deal with numbers. They store letters and other characters by assigning a number for each one.

IE auto-upgrades, plugins next?

Last week the IE team announced that they'll soon start to automatically upgrade IE across Windows 7, XP, and Vista through Windows Update. A follow up from Microsoft's IT pro team details that IE 6 and IE 7 will be upgraded to IE 8 on Windows XP, while Vista and Windows 7 users will get IE 9. With Microsoft joining the herd of auto-upgraders the final pieces of the puzzle start to fall into place, now "everybody" does it. Other major browser manufacturers (Opera, Chrome, and Firefox) have been auto-upgrading their installations for some time already. Apple's Safari now stands out in the crowd and it will be interesting to see whether they'll stick to their current update regime.

For Microsoft, this is yet another important step to kill of IE 6 which still has a considerable user base. Up til now they have been running campaigns urging users to upgrade their browsers. They actually have a website dedicated to kill of the browser, www.ie6countdown.com (I have to point out that Norway is leading the pack, with only 0.2% IE 6 users). Hopefully the automatic upgrades will have a notable impact on the remaining IE 6 installations.

In two earlier posts (one and two) I've advocated silent auto-upgrades as an important strategy to keep Internet users safe by providing them with timely security patches. Recently I came across an interesting study on the effectiveness of different Web browsers update mechanisms. It's definitely worth a read. (*Surprise*, it aligns just fine with my views so I can safely link to it).