file page 29 - Dave's Blog

Search
My timeline on Mastodon

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

Web Intents

2012 Jun 15, 8:05

This page is a high-level overview of the project and provides guidence on how to implement the intents in your applications without the need for the you to understand the entire spec.

PermalinkCommentstechnical programming web web-intents html javascript

HTTP Compression Documentation Reference

2012 Jun 13, 3:08
There's a lot of name reuse in HTTP compression so I've made the following to help myself keep it straight.
HTTP Content Coding Token gzip deflate compress
An encoding format produced by the file compression program "gzip" (GNU zip) The "zlib" format as described in RFC 1950. The encoding format produced by the common UNIX file compression program "compress".
Data Format GZIP file format ZLIB Compressed Data Format The compress program's file format
Compression Method Deflate compression method LZW
Deflate consists of LZ77 and Huffman coding

Compress doesn't seem to be supported by popular current browsers, possibly due to its past with patents.

Deflate isn't done correctly all the time. Some servers would send the deflate data format instead of the zlib data format and at least some versions of Internet Explorer expect deflate data format instead of zlib data format.

PermalinkCommentscompress compression deflate gzip http http-header technical zlib

Unicode Character Set Mappings

2012 Jun 11, 2:36

A leaf directory in a whole set of files that map from character set byte value to Unicode code point.  This one is a set of Microsoft character set byte mappings, but there are other vendors in there too.

PermalinkCommentstechnical unicode charset

Changing Windows Live IDs

2012 Jun 6, 2:54

Use of my old Hotmail account has really snuck up on me as I end up caring more and more about all of the services with which it is associated. The last straw is Windows 8 login, but previous straws include Xbox, Zune, SkyDrive, and my Windows 7 Phone. I like the features and sync'ing associated with the Windows Live ID, but I don't like my old, spam filled, hotmail email address on the Live ID account.

A coworker told me about creating a Live ID from a custom domain, which sounded like just the ticket for me. Following the instructions above I was able to create a new deletethis.net Live ID but the next step of actually using this new Live ID was much more difficult. My first hope was there would be some way to link my new and old Live IDs so as to make them interchangeable. As it turns out there is a way to link Live IDs but all that does is make it easy to switch between accounts on Live Mail, SkyDrive and some other webpages.

Instead one must change over each service or start over depending on the service:

Xbox
In the Xbox 360 system menu you can change the Live ID associated with your gamertag. This worked fine for me and I got an email telling me about the transfer of my Microsoft Points.
Zune
There's no way to do this for the Zune specifically, however changing over your Xbox account also transfers over all your Zune purchased content. I don't have a Zune Pass so I can't confirm that, but all of my previously purchased television shows transferred over successfully.
Windows 7 Phone
To change the main Live ID associated with your phone, reset your phone to factory default and start over. All purchased applications are lost. Had I purchased any applications I would have been pissed, but instead I was just irritated that I had to reset my phone.
Mail
I don't use my Hotmail account for anything and it only sits and collects spam. Accordingly I didn't attempt switching this over.
SkyDrive
I didn't have much in my SkyDrive account. I downloaded all files as a zip and then manually uploaded them to the new account.
PermalinkCommentshotmail domain win8 skydrive technical windows live-id

Working with files in JavaScript, Part 5: Blobs

2012 Jun 5, 4:13

How to create Blobs directly and via BlobBuilder.

PermalinkCommentsblob javascript programming technical web web-browser

Code: Flickr Developer Blog » Parsing Exif client-side using JavaScript

2012 Jun 1, 2:51

Flickr parses the exif out of images using Web Workers, and Blob (File API)!

PermalinkCommentsjavascript blob exif image technical programming dom webworker web-browser

Working with files in JavaScript, Part 4: Object URLs

2012 Jun 1, 2:50

On the topic of blobs and createObjectURL.  Woo blobs!

PermalinkCommentsjavascript blob dom web-browser technical programming

Raising the bar on web uploads

2012 Apr 25, 5:00

Flickr’s new HTML5-ish photo upload feature technical overview.

PermalinkCommentstechnical html html5 javascript css3 css flickr file-upload

Image Error Level Analysis with HTML5

2012 Apr 16, 1:59

Javascript tool says if a photo is shopped. It can tell by looking at the pixels. Seriously. Links to cool presentation on the theory behind the algorithm behind the tool: http://www.wired.com/images_blogs/threatlevel/files/bh-usa-07-krawetz.pdf

PermalinkCommentstechnical javascript jpeg photoshop

How to collect JavaScript performance data for Windows Metro apps on a device that does not have Visual Studio installed

2012 Mar 16, 2:27

Documentation for the VS JS profiler for Win8 HTML Metro Apps on profiling apps running on remote machines. 

PermalinkCommentswin8 programming technical js vs

Privacy through Obscurity

2012 Mar 9, 3:30

With Facebook changing its privacy policy and settings so frequently and just generally the huge amount of social sites out there, for many of us it is far too late to ensure our name doesn't show up with unfortunate results in web searches. Information is too easily copyable and archive-able to make removing these results a viable option, so clearly the solution is to create more data.

Create fake profiles on Facebook using your name but with a different photo, different date of birth, and different hometown. Create enough doppelgangers to add noise to the search results for your name. And have them share embarrassing stories on their blogs. The goal is to ensure that the din of your alternates drowns out anything embarrassing showing up for you.

Although it will look suspicious if you're the only name on Google with such chaff. So clearly you must also do this for your friends and family. Really you'll be doing them a favor.

PermalinkCommentstechnical facebook stupid internet privacy

paulftompkins: shahruz: Promo on IFC for the upcoming Comedy...

2012 Feb 29, 10:13
[Flash 10 is required to watch video.]

paulftompkins:

shahruz:

Promo on IFC for the upcoming Comedy Bang Bang TV show!!!

BE EXCITED.

I am excited Paul.

PermalinkCommentshumor video comedy-bang-bang

Using CSS without HTML (mathiasbynens.be)

2012 Feb 20, 6:11

Implied HTML elements, CSS before/after content, and the link HTTP header combines to make a document that displays something despite having a 0 byte HTML file.  Demo only in Opera/FireFox due to link HTTP header support.

PermalinkCommentstechnical humor hack css http html

Blackmail DRM - Stolen Thoughts

2012 Feb 13, 4:00

Most existing DRM attempts to only allow the user to access the DRM'ed content with particular applications or with particular credentials so that if the file is shared it won't be useful to others. A better solution is to encode any of the user's horrible secrets into unique versions of the DRM'ed content so that the user won't want to share it. Entangle the users and the content provider's secrets together in one document and accordingly their interests. I call this Blackmail DRM. For an implementation it is important to point out that the user's horrible secret doesn't need to be verified as accurate, but merely verified as believable.

Apparently I need to get these blog posts written faster because only recently I read about Social DRM which is a light weight version of my idea but with a misleading name. Instead of horrible secrets, they say they'll use personal information like the user's name in the DRM'ed content. More of my thoughts stolen and before I even had a chance to think of it first!

PermalinkCommentsdrm blackmail blackmail-drm technical humor social-drm

FBI: Carrier IQ files used for "law enforcement purposes" (muckrock.com)

2011 Dec 14, 6:40PermalinkComments

Indicating Character Encoding and Language for HTTP Header Field Parameters

2011 Nov 24, 7:45

From the document: ‘Appendix B. Implementation Report: The encoding defined in this document currently is used for two different HTTP header fields: “Content-Disposition”, defined in [RFC6266], and “Link”, defined in [RFC5988]. As the encoding is a profile/clarification of the one defined in [RFC2231] in 1997, many user agents already supported it for use in “Content-Disposition” when [RFC5987] got published.

Since the publication of [RFC5987], two more popular desktop user agents have added support for this encoding; see http://purl.org/
   NET/http/content-disposition-tests#encoding-2231-char for details. At this time, only one major desktop user agent (Safari) does not support it.

Note that the implementation in Internet Explorer 9 does not support the ISO-8859-1 encoding; this document revision acknowledges that UTF-8 is sufficient for expressing all code points, and removes the requirement to support ISO-8859-1.’

Yay for UTF-8!

PermalinkCommentstechnical http http-headers ie9 internationalization utf-8 encoding

NYTimes Sues US For Refusing To Reveal Secret Interpretation Of Patriot Act (techdirt.com)

2011 Oct 20, 6:52
Wow, FTA: "Given all of this, reporter Charlie Savage of the NY Times filed a Freedom of Information Act request to find out the federal government's interpretation of its own law... and had it refused. According to the federal government, its own interpretation of the law is classified."
PermalinkCommentstechnical

manifestR - offline web apps made easy (well easier)

2011 Jul 14, 7:34A bookmarklet to help you create an appcache manifest: "...click the manifestR button, and it will create an HTML5 appcache manifest file for that page."PermalinkCommentsdevelopment javascript tools html5 cache technical

David Risney - Google Profile

2011 Jul 1, 5:52Hooking up my authorship tags: http://googlewebmastercentral.blogspot.com/2011/06/authorship-markup-and-web-search.htmlPermalinkCommentsprofile me
Older EntriesNewer Entries Creative Commons License Some rights reserved.