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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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Tweet from David Rousset

2016 Dec 6, 8:45
Creating an extension for all browsers: , , , & : https://www.davrous.com/2016/12/07/creating-an-extension-for-all-browsers-edge-chrome-firefox-opera-brave/ 
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Tweet from David Risney

2016 Aug 5, 3:20
I've put my WPAD DHCP server Fiddler extension up on GitHub https://deletethis.net/dave/2016-08/WPAD+Server+Fiddler+Extension+Source 
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WPAD Server Fiddler Extension Source

2016 Aug 5, 3:18

I've put my WPAD Fiddler extension source and the installer on GitHub.

Six years ago I made a WPAD DHCP server Fiddler extension (described previously and previously). The extension runs a WPAD DHCP server telling any clients that connect to connect to the running Fiddler instance. I've finally got around to putting the source on GitHub. I haven't touched it in five or so years so this is either for posterity or education or something.

PermalinkCommentsdhcp fiddler network security wpad

Let's Encrypt NearlyFreeSpeech.net Setup

2016 Feb 4, 2:48

2016-Nov-5: Updated post on using Let's Encrypt with NearlyFreeSpeech.net

I use NearlyFreeSpeech.net for my webhosting for my personal website and I've just finished setting up TLS via Let's Encrypt. The process was slightly more complicated than what you'd like from Let's Encrypt. So for those interested in doing the same on NearlyFreeSpeech.net, I've taken the following notes.

The standard Let's Encrypt client requires su/sudo access which is not available on NearlyFreeSpeech.net's servers. Additionally NFSN's webserver doesn't have any Let's Encrypt plugins installed. So I used the Let's Encrypt Without Sudo client. I followed the instructions listed on the tool's page with the addition of providing the "--file-based" parameter to sign_csr.py.

One thing the script doesn't produce is the chain file. But this topic "Let's Encrypt - Quick HOWTO for NSFN" covers how to obtain that:

curl -o domain.chn https://letsencrypt.org/certs/lets-encrypt-x1-cross-signed.pem

Now that you have all the required files, on your NFSN server make the directory /home/protected/ssl and copy your files into it. This is described in the NFSN topic provide certificates to NFSN. After copying the files and setting their permissions as described in the previous link you submit an assistance request. For me it was only 15 minutes later that everything was setup.

After enabling HTTPS I wanted to have all HTTP requests redirect to HTTPS. The normal Apache documentation on how to do this doesn't work on NFSN servers. Instead the NFSN FAQ describes it in "redirect http to https and HSTS". You use the X-Forwarded-Proto instead of the HTTPS variable because of how NFSN's virtual hosting is setup.

RewriteEngine on
RewriteCond %{HTTP:X-Forwarded-Proto} !https
RewriteRule ^.*$ https://%{SERVER_NAME}%{REQUEST_URI} [L,R=301]

Turning on HSTS is as simple as adding the HSTS HTTP header. However, the description in the above link didn't work because my site's NFSN realm isn't on the latest Apache yet. Instead I added the following to my .htaccess. After I'm comfortable with everything working well for a few days I'll start turning up the max-age to the recommended minimum value of 180 days.

Header set Strict-Transport-Security "max-age=3600;" 

Finally, to turn on CSP I started up Fiddler with my CSP Fiddler extension. It allows me to determine the most restrictive CSP rules I could apply and still have all resources on my page load. From there I found and removed inline script and some content loaded via http and otherwise continued tweaking my site and CSP rules.

After I was done I checked out my site on SSL Lab's SSL Test to see what I might have done wrong or needed improving. The first time I went through these steps I hadn't included the chain file which the SSL Test told me about. I was able to add that file to the same files I had already previously generated from the Let's Encrypt client and do another NFSN assistance request and 15 minutes later the SSL Test had upgraded me from 'B' to 'A'.

PermalinkCommentscertificate csp hsts https lets-encrypt nearlyfreespeech.net

Tweet from David_Risney

2015 Aug 3, 12:18
I watched ep1 of Murder in the First last night and Taye Diggs followed me this morning. Coincidence? Or maybe he's into my CSP extension.
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Retweet of troyhunt

2015 Aug 2, 10:14
Just gave the CSP Rule Collector Fiddler extension from @David_Risney a run. This is excellent, highly recommended! https://twitter.com/ericlaw/status/627572451015168000 …
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Retweet of grittygrease

2015 Jul 2, 9:53
TLS Client Puzzles Extension http://buff.ly/1GS4bke 
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David_Risney: Just put up CSP Fiddler extension to help figure out minimum required CSP rules for web pages.

2015 Jan 24, 5:32
David Risney @David_Risney :
Just put up CSP Fiddler extension https://github.com/david-risney/CSP-Fiddler-Extension … to help figure out minimum required CSP rules for web pages.
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URI Design and Ownership - IETF Draft

2014 May 21, 2:06

URI Design & Ownership - On the issues with and alternatives to requiring well known filenames and extensions in URIs. You must love the draft’s URI.

PermalinkCommentstechnical uri

Stripe CTF - Level 7

2012 Sep 13, 5:00

Level 7 of the Stripe CTF involved running a length extension attack on the level 7 server's custom crypto code.

Code

@app.route('/logs/')
@require_authentication
def logs(id):
rows = get_logs(id)
return render_template('logs.html', logs=rows)

...

def verify_signature(user_id, sig, raw_params):
# get secret token for user_id
try:
row = g.db.select_one('users', {'id': user_id})
except db.NotFound:
raise BadSignature('no such user_id')
secret = str(row['secret'])

h = hashlib.sha1()
h.update(secret + raw_params)
print 'computed signature', h.hexdigest(), 'for body', repr(raw_params)
if h.hexdigest() != sig:
raise BadSignature('signature does not match')
return True

Issue

The level 7 web app is a web API in which clients submit signed RESTful requests and some actions are restricted to particular clients. The goal is to view the response to one of the restricted actions. The first issue is that there is a logs path to display the previous requests for a user and although the logs path requires the client to be authenticatd, it doesn't restrict the logs you view to be for the user for which you are authenticated. So you can manually change the number in the '/logs/[#]' to '/logs/1' to view the logs for the user ID 1 who can make restricted requests. The level 7 web app can be exploited with replay attacks but you won't find in the logs any of the restricted requests we need to run for our goal. And we can't just modify the requests because they are signed.

However they are signed using their own custom signing code which can be exploited by a length extension attack. All Merkle–Damgård hash algorithms (which includes MD5, and SHA) have the property that if you hash data of the form (secret + data) where data is known and the length but not content of secret is known you can construct the hash for a new message (secret + data + padding + newdata) where newdata is whatever you like and padding is determined using newdata, data, and the length of secret. You can find a sha-padding.py script on VNSecurity blog that will tell you the new hash and padding per the above. With that I produced my new restricted request based on another user's previous request. The original request was the following.

count=10&lat=37.351&user_id=1&long=%2D119.827&waffle=eggo|sig:8dbd9dfa60ef3964b1ee0785a68760af8658048c
The new request with padding and my new content was the following.
count=10&lat=37.351&user_id=1&long=%2D119.827&waffle=eggo%80%02%28&waffle=liege|sig:8dbd9dfa60ef3964b1ee0785a68760af8658048c
My new data in the new request is able to overwrite the waffle parameter because their parser fills in a map without checking if the parameter existed previously.

Notes

Code review red flags included custom crypto looking code. However I am not a crypto expert and it was difficult for me to find the solution to this level.

PermalinkCommentshash internet length-extension security sha1 stripe-ctf technical web

Stripe CTF - Input validation (Levels 1 & 2)

2012 Sep 6, 5:00

Stripe's web security CTF's Level 1 and level 2 of the Stripe CTF had issues with missing input validation solutions described below.

Level 1

Code

          $filename = 'secret-combination.txt';
extract($_GET);
if (isset($attempt)) {
$combination = trim(file_get_contents($filename));
if ($attempt === $combination) {

Issue

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.

Notes

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.

Level 2

Code

    $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.

";
}

Issue

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:


Notes

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.

PermalinkCommentsinput-validation php security technical

Stripe Web Security CTF Summary

2012 Aug 30, 5:00

I was the 546th person to complete Stripe's web security CTF and again had a ton of fun applying my theoretical knowledge of web security issues to the (semi-)real world. As I went through the levels I thought about what red flags jumped out at me (or should have) that I could apply to future code reviews:

Level Issue Code Review Red Flags
0 Simple SQL injection No encoding when constructing SQL command strings. Constructing SQL command strings instead of SQL API
1 extract($_GET); No input validation.
2 Arbitrary PHP execution No input validation. Allow file uploads. File permissions modification.
3 Advanced SQL injection Constructing SQL command strings instead of SQL API.
4 HTML injection, XSS and CSRF No encoding when constructing HTML. No CSRF counter measures. Passwords stored in plain text. Password displayed on site.
5 Pingback server doesn't need to opt-in n/a - By design protocol issue.
6 Script injection and XSS No encoding while constructing script. Deny list (of dangerous characters). Passwords stored in plain text. Password displayed on site.
7 Length extension attack Custom crypto code. Constructing SQL command string instead of SQL API.
8 Side channel attack Password handling code. Timing attack mitigation too clever.

More about each level in the future.

PermalinkCommentscode-review coding csrf html internet programming script security sql stripe technical web xss

A Dad’s Plea To Developers Of iPad Apps For Children (smashingmagazine.com)

2012 Mar 12, 7:02

Set of issues run into by children using iPad apps.  Should be generally appropriate though:

Designing apps for children is extremely hard. Not only is quality, age-appropriate content hard to create, but designing the flow and interaction of these apps is made more difficult because designers must refrain from implementing advanced gestures, which would only confuse and frustrate kids (and, by extension, their parents). Yet all apps can and should adhere to certain basics. Hopefully, the four guidelines discussed here can become fixtures of all children’s apps.

PermalinkCommentstechnical ui ipad design children programming

"Forwarded HTTP Extension" - Andreas Petersson, Martin Nilsson

2012 Jan 27, 9:41PermalinkCommentstechnical http http-header proxy ietf standard

"Forwarded HTTP Extension" - Andreas Petersson, Martin Nilsson

2011 Nov 17, 3:30

Describes forward HTTP headers to explicitly list proxying information that might otherwise be lost.

PermalinkCommentstechnical ietf http http-header proxy

WPAD Server Fiddler Extension Update v1.0.1

2011 Jun 12, 3:34
As it turns out the WPAD Server Fiddler Extension I made a while back actually has a non-malicious purpose. Apparently its useful for debugging HTTP on the WP7 phone (or so I'm told). Anyway I took some requests and I've fixed a few minor bugs (start button not updating correctly), changed the dialog to be a Fiddler tab so you can use it non-modally, and the WPAD server is now always off when Fiddler starts.
PermalinkCommentsextension fiddler technical update wpad

RFC 5987 - Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters

2010 Aug 13, 11:47Other characters sets for HTTP headers: "By default, message header field parameters in Hypertext Transfer Protocol (HTTP) messages cannot carry characters outside the ISO-8859-1 character set. RFC 2231 defines an encoding mechanism for use in Multipurpose Internet Mail Extensions (MIME) headers. This document specifies an encoding suitable for use in HTTP header fields that is compatible with a profile of the encoding defined in RFC 2231."PermalinkCommentsrfc language localization charset http technical reference http-header

PowerShell Integration Into Visual Studio

2010 Jun 22, 1:49"The PowerGUI Visual Studio Extension adds PowerShell IntelliSense support to Visual Studio."PermalinkCommentstechnical powershell visual-studio microsoft programming shell ide

Shepard Fairey - Interview Magazine

2010 May 10, 8:59Iggy Pop interviews Shepard Fairey, including his Obama HOPE poster and AP lawsuit:

"... but the American public is generally pretty superficial, so an image like that just allows them to project whatever limited idea they have onto it. Obviously, not everyone is like that—I actually think there were a lot of people who were bummed by the image because they felt it was shallow propaganda."

"If I spend time conceiving and making a piece of art and somebody else sees that it has market value and replicates it in order to steal part of my market, then that’s not cool. But the way I make art—the way a lot of people make art—is as an extension of language and communication, where references are incredibly important. It’s about making a work that is inspired by something preexisting but changes it to have a new value and meaning that doesn’t in any way take away from the original—and, in fact, might provide the original with a second life or a new audience."
PermalinkCommentsart legal law ip shepard-fairey obey interview
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