writing Promise-using API's: http://bit.ly/1KsMQ7X - must read for all JavaScript and spec developers alike.
This is profoundly troubling, especially after learning that a recent
mass shooting was executed via such a gun. http://www.wired.com/2015/06/i-made-an-untraceable-ar-15-ghost-gun/ …
@rajcardwell @cstross Here's the specific letter in the files that screamed "Laundry!" at me. pic.twitter.com/FSYjc4OuQ0
Some time back while I was working on getting the Javascript Windows Store app platform running on Windows Phone (now available on the last Windows Phone release!) I had an interesting bug that in retrospect is amusing.
I had just finished a work item to get accessibility working for JS WinPhone apps when I got a new bug: With some set of JS apps, accessibility appeared to be totally broken. At that time in development the only mechanism we had to test accessibility was a test tool that runs on the PC, connects to the phone, and dumps out the accessibility tree of whatever app is running on the phone. In this bug, the tool would spin for a while and then timeout with an error and no accessibility information.
My first thought was this was an issue in my new accessibility code. However, debugging with breakpoints on my code I could see none of my code was run nor the code that should call it. The code that called that code was a more generic messaging system that hit my breakpoints constantly.
Rather than trying to work backward from the failure point, I decided to try and narrow down the repro and work forwards from there. One thing all the apps with the bug had in common was their usage of WinJS, but not all WinJS apps demonstrated the issue. Using a binary search approach on one such app I removed unrelated app code until all that was left was the app's usage of the WinJS AppBar and the bug still occurred. I replaced the WinJS AppBar usage with direct usage of the underlying AppBar WinRT APIs and continued.
Only some calls to the AppBar WinRT object produced the issue:
var appBar = Windows.UI.WebUI.Core.WebUICommandBar.getForCurrentView();
// appBar.opacity = 1;
// appBar.closeDisplayMode = Windows.UI.WebUI.Core.WebUICommandBarClosedDisplayMode.default;
appBar.backgroundColor = Windows.UI.Colors.white; // Bug!
I eventually realized that predefined WinRT color values like Windows.UI.Colors.aqua would cause the issue while JS literal based colors didn't cause the issue (Windows.UI.Color is a WinRT struct which projects in JS as a JS literal object with the struct members as JS
object properties so its easy to write something like {r: 0, g: 0, b: 0, a: 0} to make a color) and I had been mixing both in my tests without realizing there would be a difference.
I debugged into the backgroundColor property setter that consumed the WinRT color struct to see what was different between Windows.UI.Colors.black and {a: 1, r: 0, g: 0, b: 0} and
found the two structs to be byte wise exactly the same.
On a hunch I tried my test app with only a reference to the color and otherwise no interaction with the AppBar and not doing anything with the actual reference to the color:
Windows.UI.Colors.black;. This too caused the issue. I knew that the implementation for these WinRT const values live in a DLL and guessed that something in the code to create these
predefined colors was causing the issue. I debugged in and no luck. Now I also have experienced crusty code that would do exciting things in its DllMain, the function that's called when a DLL is loaded into the process so I tried modifying my
C++ code to simply LoadLibrary the DLL containing the WinRT color definition, windows.ui.xaml.dll and found the bug still occurred! A short lived moment of relief as the world seemed to make
sense again.
Debugging into DllMain nothing interesting happened. There were interesting calls in there to be sure, but all of them behind conditions that were false. I was again stumped. On another hunch I tried renaming the DLL and only LoadLibrary'ing it and the bug went away. I took a different DLL renamed it windows.ui.xaml.dll and tried LoadLibrary'ing that and the bug came back. Just the name of the DLL was causing the issue.
I searched for the DLL name in our source code index and found hits in the accessibility tool. Grinning I opened the source to find that the accessibility tool's phone side service was trying to determine if a process belonged to a XAML app or not because XAML apps had a different accessibility contract. It did this by checking to see if windows.ui.xaml.dll was loaded in the target process.
At this point I got to fix my main issue and open several new bugs for the variety of problems I had just run into. This is a how to on writing software that is difficult to debug.
The Wall Street Journal was first to report that The Federal Communications Commission will propose new open Internet rules this Thursday that will allow content companies to pay Internet service providers “for special access to consumers.” Under the new rules, service providers may not block or discriminate against specific websites, but they can charge certain sites or services for preferential traffic treatment if the ISPs’ discrimination is “commercially reasonable.” Bye-bye, Net Neutrality, and the internet as we know it.
In IE10 and other new browsers one may create MessageChannel objects that have two MessagePorts each connected (w3c spec calls it entangled) to one another such that postMessage on one port results in the message event firing on the other. You can pass an array of ports as the last parameter to postMessage and they show up in the ports property of the message event arg.
The postMessage here is like the worker postMessage and unlike the window and iframe postMessage in that it applies no origin checking:
Unfortunately the origin isn't an optional parameter at the end to make the two postMessages have the same signature.
On the event handler side, the event arg always has an origin property. But in the no origin case it is always the empty string.
There is also a source property on the message event arg which if set is an object that has a postMessage property allowing you to post back to your caller. It is set for the origin case, however, in the no origin case this property is null. This is somewhat reasonable because in the case of MessagePort and Workers there are only two endpoints so you always know the source of a message implicitly. Unlike the origin case in which any iframe or window can be calling postMessage on any other iframe or window and the caller is unknown. So not unreasonable but it would be nice if the source property was always set for consistency.
When a MessageChannel is created it has two MessagePorts, but until those ports are started they will queue up any messages they receive. Once started they will dispatch all queued messages. Ports don't have to be started to send messages.
A port may be started in two ways, either by explicitly calling the start method on the port, or by setting the onmessage callback property on the port. However, adding an event listener via addEventListener("message", does not start the port. It works this way in IE and Chrome and the spec states this as well.
The justification is that since you can have only one callback via onmessage that once set you must implicitly be ready to receive messages and its fine to start the port. As opposed to the addEventListener in which case the user agent cannot start implicitly because it doesn't know how many event listeners will be added. I found Hixie stating this justification in geoloc meeting notes.
My third completed Windows Store app is Percent Clock which displays portions of a time span like the time of the day or time until your next birthday, as a percentage. This was a small project I had previously started as a webpage and converted and finished as an HTML JavaScript Windows Store app.
The only somewhat interesting aspect of this app is that its the first app for which I tried charging. I picked the minimum amount for price 1.49 USD as it is a simple app and unsurprisingly it has sold very poorly. I'm considering releasing new instances of the app for specific scenarios:
The Windows Runtime API Windows.Foundation.Collections.PropertySet class is a nice string name to object value map that has a changed event that fires when the contents of the map is modified. Be careful with this event because it fires synchronously from the thread on which the PropertySet was modified. If modified from the UI thread, the UI thread will then wait as it synchronously dispatches the changed event to all listeners which could lead to performance issues or especially from the UI thread deadlock. For instance, deadlock if you have two threads both trying to tell each other about changed events for different PropertySets.
If you want to represent a value larger than 32bits in an enum in MSVC++ you can use C++0x style syntax to tell the compiler exactly what kind of integral type to store the enum values. Unfortunately by default an enum is always 32bits, and additionally while you can specify constants larger than 32bits for the enum values, they are silently truncated to 32bits.
For instance the following doesn't compile because Lorem::a and Lorem::b have the same value of '1':
enum Lorem {
a = 0x1,
b = 0x100000001
} val;
switch (val) {
case Lorem::a:
break;
case Lorem::b:
break;
}
Unfortunately it is not an error to have b's constant truncated, and the previous without the switch statement does compile just fine:
enum Lorem {
a = 0x1,
b = 0x100000001
} val;
But you can explicitly specify that the enum should be represented by a 64bit value and get expected compiling behavior with the following:
enum Lorem : UINT64 {
a = 0x1,
b = 0x100000001
} val;
switch (val) {
case Lorem::a:
break;
case Lorem::b:
break;
}
What It All Means: All Your Communications are Belong to U.S. In sum, if you use encryption they’ll keep your data forever. If you use Tor, they’ll keep your data for at least five years. If an American talks with someone outside the US, they’ll keep your data for five years. If you’re talking to your attorney, you don’t have any sense of privacy. And the NSA can hand over you information to the FBI for evidence of any crime, not just terrorism. All without a warrant or even a specific FISA order.
Not sure if this is saying all Tor data is collected or saying if someone uses Tor then start collecting that someone’s communication.
This is essentially an AV exploit against Super Mario World that results in running the end game code. Watch the video. “…there’s a glitch that’s been known for a while, where Yoshi can end up in the “I have an item in my mouth” state, but not actually have an item in his mouth. When he spits out this nothingness, the game crashes. …That address did not contain code, and so the system crashed. But wait a second. What if, by some sheer coincidence, that address did contain code? The specific address dropped him in somewhere amongst various data for the game’s internal random number generator, and the random number generator can be manipulated in a TAS. Could the game be coerced into running arbitrary code?…”
A Slower Speed of Light Official Trailer — MIT Game Lab (by Steven Schirra)
“A Slower Speed of Light is a first-person game in which players navigate a 3D space while picking up orbs that reduce the speed of light in increments. A custom-built, open-source relativistic
graphics engine allows the speed of light in the game to approach the player’s own maximum walking speed. Visual effects of special relativity gradually become apparent to the player, increasing
the challenge of gameplay. These effects, rendered in realtime to vertex accuracy, include the Doppler effect; the searchlight effect; time dilation; Lorentz transformation; and the runtime
effect.
A production of the MIT Game Lab.
Play now for Mac and PC! http://gamelab.mit.edu/games/a-slower-speed-of-light/”
Moral: laws should cover behavior not specific technologies. The implementation can change, laws shouldn’t take such dependencies.
Welcome news. Glad to hear they’re looking for improvements.
… the USPTO has also worked with Stack Exchange, … to create a new site called Ask Patents. … Examiners or others looking for prior art can post questions about a specific application, and members of the general public can respond with evidence that an applicant was not the first to invent the subject matter of the application.
Stripe's web security CTF's Level 1 and level 2 of the Stripe CTF had issues with missing input validation solutions described below.
$filename = 'secret-combination.txt';
extract($_GET);
if (isset($attempt)) {
$combination = trim(file_get_contents($filename));
if ($attempt === $combination) {The issue here is the usage of the extract php method which extracts name value pairs from the map input parameter and creates corresponding local variables. However this code uses $_GET which contains a map of name value pairs passed in the query of the URI. The expected behavior is to get an attempt variable out, but since no input validation is done I can provide a filename variable and overwrite the value of $filename. Providing an empty string gives an empty string $combination which I can match with an empty string $attempt. So without knowing the combination I can get past the combination check.
Code review red flag in this case was the direct use of $_GET with no validation. Instead of using extract the developer could try to extract specifically the attempt variable manually without using extract.
$dest_dir = "uploads/";
$dest = $dest_dir . basename($_FILES["dispic"]["name"]);
$src = $_FILES["dispic"]["tmp_name"];
if (move_uploaded_file($src, $dest)) {
$_SESSION["dispic_url"] = $dest;
chmod($dest, 0644);
echo "Successfully uploaded your display picture.
";
}
This code accepts POST uploads of images but with no validation to ensure it is not an arbitrary file. And even though it uses chmod to ensure the file is not executable, things like PHP don't require a file to be executable in order to run them. Accordingly, one can upload a PHP script, then navigate to that script to run it. My PHP script dumped out the contents of the file we're interested in for this level:
Code review red flags include manual file management, chmod, and use of file and filename inputs without any kind of validation. If this code controlled the filename and ensured that the extension was one of a set of image extensions, this would solve this issue. Due to browser mime sniffing its additionally a good idea to serve a content-type that starts with "image/" for these uploads to ensure browsers treat these as images and not sniff for script or HTML.
Stripe is running a web security capture the flag - a series of increasingly difficult web security exploit challenges. I've finished it and had a lot of fun. Working on a web browser I knew the theory of these various web based attacks, but this was my first chance to put theory into practice with:
Here's a blog post on the CTF behind the scenes setup which has many impressive features including phantom users that can be XSS/CSRF'ed.
I'll have another post on my difficulties and answers for the CTF levels after the contest is over on Wed, but if you're looking for hints, try out the CTF chatroom or the level specific CTF chatroom.
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