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Right-To-Left Override Twitter Name

2020 Oct 21, 3:50

Its rare to find devs anticipating Unicode control characters showing up in user input. And the most fun when unanticipated is the Right-To-Left Override character U+202E. Unicode characters have an implicit direction so that for example by default Hebrew characters are rendered from right to left, and English characters are rendered left to right. The override characters force an explicit direction for all the text that follows.

I chose my Twitter display name to include the HTML encoding of the Right-To-Left Override character #x202E; as a sort of joke or shout out to my favorite Unicode control character. I did not anticipate that some Twitter clients in some of their UI would fail to encode it correctly. There's no way I can remove that from my display name now.


Try it on Amazon.


How about pages that want to tell you about the U+202E. 


PermalinkCommentsUnicode

Application Content URI Rule effects

2017 Jun 30, 3:01

Previously I described Application Content URI Rules (ACUR) parsing and ACUR ordering. This post describes what you get from putting a URI in ACUR.

URIs in the ACUR gain the following which is otherwise unavailable:

  • Geoloc API usage
  • Audio and video capture API usage
  • Pointer lock API usage
  • Web notifications API usage
  • IndexedDB API usage
  • Clipboard API usage
  • window.external.notify access from within webview
  • window.close the primary window
  • Top level navigation in the primary window
  • Cross origin XHR and fetch to ms-appx(-web) scheme URIs
  • Cross origin dirtied canvas read access if dirtied by ms-appx(-web) scheme URIs
  • Cross origin text track for video element for tracks from ms-appx(-web) scheme URIs

URIs in the ACUR that also have full WinRT access additionally gain the following:

  • Cross origin XHR and fetch
  • Cross origin dirtied canvas read access
  • Cross origin text track for video element
  • Local audio and video WinRT plugins work with media elements
PermalinkCommentsapplication-content-uri-rules coding javascript programming windows-store

JavaScript Microsoft Store app StartPage

2017 Jun 22, 8:58

JavaScript Microsoft Store apps have some details related to activation that are specific to JavaScript Store apps and that are poorly documented which I’ll describe here.

StartPage syntax

The StartPage attributes in the AppxManifest.xml (Package/Applications/Application/@StartPage, Package/Applications/Extensions/Extension/@StartPage) define the HTML page entry point for that kind of activation. That is, Application/@StartPage defines the entry point for tile activation, Extension[@Category="windows.protocol"]/@StartPage defines the entry point for URI handling activation, etc. There are two kinds of supported values in StartPage attributes: relative Windows file paths and absolute URIs. If the attribute doesn’t parse as an absolute URI then it is instead interpreted as relative Windows file path.

This implies a few things that I’ll declare explicitly here. Windows file paths, unlike URIs, don’t have a query or fragment, so if you are using a relative Windows file path for your StartPage attribute you cannot include anything like ‘?param=value’ at the end. Absolute URIs use percent-encoding for reserved characters like ‘%’ and ‘#’. If you have a ‘#’ in your HTML filename then you need to percent-encode that ‘#’ for a URI and not for a relative Windows file path.

If you specify a relative Windows file path, it is turned into an ms-appx URI by changing all backslashes to forward slashes, percent-encoding reserved characters, and combining the result with a base URI of ms-appx:///. Accordingly the relative Windows file paths are relative to the root of your package. If you are using a relative Windows file path as your StartPage and need to switch to using a URI so you can include a query or fragment, you can follow the same steps above.

StartPage validity

The validity of the StartPage is not determined before activation. If the StartPage is a relative Windows file path for a file that doesn’t exist, or an absolute URI that is not in the Application Content URI Rules, or something that doesn’t parse as a Windows file path or URI, or otherwise an absolute URI that fails to resolve (404, bad hostname, etc etc) then the JavaScript app will navigate to the app’s navigation error page (perhaps more on that in a future blog post). Just to call it out explicitly because I have personally accidentally done this: StartPage URIs are not automatically included in the Application Content URI Rules and if you forget to include your StartPage in your ACUR you will always fail to navigate to that StartPage.

StartPage navigation

When your app is activated for a particular activation kind, the StartPage value from the entry in your app’s manifest that corresponds to that activation kind is used as the navigation target. If the app is not already running, the app is activated, navigated to that StartPage value and then the Windows.UI.WebUI.WebUIApplication activated event is fired (more details on the order of various events in a moment). If, however, your app is already running and an activation occurs, we navigate or don’t navigate to the corresponding StartPage depending on the current page of the app. Take the app’s current top level document’s URI and if after removing the fragment it already matches the StartPage value then we won’t navigate and will jump straight to firing the WebUIApplication activated event.

Since navigating the top-level document means destroying the current JavaScript engine instance and losing all your state, this behavior might be a problem for you. If so, you can use the MSApp.pageHandlesAllApplicationActivations(true) API to always skip navigating to the StartPage and instead always jump straight to firing the WebUIApplication activated event. This does require of course that all of your pages all handle all activation kinds about which any part of your app cares.

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Retweet of BetaHorton

2016 Feb 12, 1:52
I want to live in a world where coding is as awesome as it appears in the movies #Hackers #NeedASkateboard pic.twitter.com/ai1JkrarTH
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Tweet from David_Risney

2016 Jan 27, 10:28
Identify coder from binary based on code style. https://freedom-to-tinker.com/blog/aylin/when-coding-style-survives-compilation-de-anonymizing-programmers-from-executable-binaries/ … Following company style guidelines is now a privacy issue.
PermalinkComments

Tweet from David_Risney

2015 Dec 14, 12:28
First thought was: How did a character encoding issue get that far? pic.twitter.com/TIxrbLcylO
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Retweet of codinghorror

2015 Mar 30, 1:19
Pastebin single-payment lifetime accounts on sale. Check out pastebin's greatest hits: http://pastebin.com/trends/all 
PermalinkComments

Retweet of codinghorror

2015 Mar 26, 9:13
How Punch-Out save game passwords work, including bugs http://tomorrowcorporation.com/posts/retro-game-internals-punch-out-passwords …
PermalinkComments

Tweet from David_Risney

2015 Mar 26, 4:20
Anyone know why Chrome percent-encodes single quote in URI query? http://jsfiddle.net/unLrqxso/1/  Its a reserved char so encoding changes URI.
PermalinkComments

Retweet of codinghorror

2015 Mar 18, 12:02
it is so much faster to find things on the internet than it is to find things on my local computer. Has been for years
PermalinkComments

Tweet from David_Risney

2015 Feb 12, 8:35
Unicode encoding holy wars via Mark Pilgrim / Emo Philips http://web.archive.org/web/20080209154953/http://diveintomark.org/archives/2004/07/06/nfc …
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David_Risney: Learn about ES6 template strings: I didn't know about tagged templates allowing for HTML encoding in template strings

2015 Jan 21, 12:15
David Risney @David_Risney :
Learn about ES6 template strings: http://updates.html5rocks.com/2015/01/ES6-Template-Strings … I didn't know about tagged templates allowing for HTML encoding in template strings
PermalinkComments

Image Manipulation in PowerShell - Windows PowerShell Blog - Site Home - MSDN Blogs

2015 Jan 5, 1:20

Great blog post and set of powershell scripts for manipulating images.

PermalinkCommentsprogramming coding powershell

Image Manipulation in PowerShell - Windows PowerShell Blog - Site Home - MSDN Blogs

2015 Jan 5, 1:20

Great blog post and set of powershell scripts for manipulating images.

PermalinkCommentsprogramming coding powershell

Live coding in VR with the Oculus Rift, Firefox WebVR,...

2014 Oct 6, 2:45


Live coding in VR with the Oculus Rift, Firefox WebVR, JavaScript and Three.js

“I built a live-coding web app for the Oculus Rift where you code in JavaScript using Three.js and watch the world change around you in real-time.”

PermalinkCommentsvideo programming javascript 3d vr oculus-rift technical

JS NICE: Statistical renaming, Type inference and Deobfuscation

2014 Jun 3, 9:36

JS NICE | Software Reliability Lab in ETH

JS NICE has indexed over 10,000 JavaScript projects from GitHub and then probabilistically infers newly suggested names and types for all of the local variables and function parameters of new JS.

PermalinkCommentstechnical javascript js coding

Very Serious Button

2014 May 17, 1:34

A physical big red button that is a USB keyboard with a configurable single key. This looks wonderful. I’ll take 26.

RT @codinghorror The Very Serious USB Button https://www.indiegogo.com/projects/very-serious-button/

PermalinkCommentshumor hardward big-red-button

Results of the Grand C++ Error Explosion Competition

2014 Jan 28, 4:58

tgceec:

After much deliberation, the winners of the Grand C++ Error Explosion Competition are finally selected. There are two different award categories. The winners of the first category are those submissions that produced the largest error with the smallest amount of source code. These entries contain a…

PermalinkCommentshumor technical c++ programming coding

URI functions in Windows Store Applications

2013 Jul 25, 1:00PermalinkCommentsc# c++ javascript technical uri windows windows-runtime windows-store

Stripe CTF - XSS, CSRF (Levels 4 & 6)

2012 Sep 10, 4:43

Level 4 and level 6 of the Stripe CTF had solutions around XSS.

Level 4

Code

> Registered Users 

    <%@registered_users.each do |user| %>
    <%last_active = user[:last_active].strftime('%H:%M:%S UTC') %>
    <%if @trusts_me.include?(user[:username]) %>

  • <%= user[:username] %>
    (password: <%= user[:password] %>, last active <%= last_active %>)
  • Issue

    The level 4 web application lets you transfer karma to another user and in doing so you are also forced to expose your password to that user. The main user page displays a list of users who have transfered karma to you along with their password. The password is not HTML encoded so we can inject HTML into that user's browser. For instance, we could create an account with the following HTML as the password which will result in XSS with that HTML:

    
    
    This HTML runs script that uses jQuery to post to the transfer URI resulting in a transfer of karma from the attacked user to the attacker user, and also the attacked user's password.

    Notes

    Code review red flags in this case included lack of encoding when using user controlled content to create HTML content, storing passwords in plain text in the database, and displaying passwords generally. By design the web app shows users passwords which is a very bad idea.

    Level 6

    Code

    
    

    ...

    def self.safe_insert(table, key_values)
    key_values.each do |key, value|
    # Just in case people try to exfiltrate
    # level07-password-holder's password
    if value.kind_of?(String) &&
    (value.include?('"') || value.include?("'"))
    raise "Value has unsafe characters"
    end
    end

    conn[table].insert(key_values)
    end

    Issue

    This web app does a much better job than the level 4 app with HTML injection. They use encoding whenever creating HTML using user controlled data, however they don't use encoding when injecting JSON data into script (see post_data initialization above). This JSON data is the last five most recent messages sent on the app so we get to inject script directly. However, the system also ensures that no strings we write contains single or double quotes so we can't get out of the string in the JSON data directly. As it turns out, HTML lets you jump out of a script block using no matter where you are in script. For instance, in the middle of a value in some JSON data we can jump out of script. But we still want to run script, so we can jump right back in. So the frame so far for the message we're going to post is the following:

    
    
    
    
PermalinkCommentscsrf encoding html internet javascript percent-encoding script security stripe-ctf technical web xss
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