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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
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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 - SQL injections (Levels 0 & 3)

2012 Sep 5, 9:10

Stripe's web security CTF's level 0 and level 3 had SQL injection solutions described below.

Level 0

Code

app.get('/*', function(req, res) {
var namespace = req.param('namespace');

if (namespace) {
var query = 'SELECT * FROM secrets WHERE key LIKE ? || ".%"';
db.all(query, namespace, function(err, secrets) {

Issue

There's no input validation on the namespace parameter and it is injected into the SQL query with no encoding applied. This means you can use the '%' character as the namespace which is the wildcard character matching all secrets.

Notes

Code review red flag was using strings to query the database. Additional levels made this harder to exploit by using an API with objects to construct a query rather than strings and by running a query that only returned a single row, only ran a single command, and didn't just dump out the results of the query to the caller.

Level 3

Code

@app.route('/login', methods=['POST'])
def login():
username = flask.request.form.get('username')
password = flask.request.form.get('password')

if not username:
return "Must provide username\n"

if not password:
return "Must provide password\n"

conn = sqlite3.connect(os.path.join(data_dir, 'users.db'))
cursor = conn.cursor()

query = """SELECT id, password_hash, salt FROM users
WHERE username = '{0}' LIMIT 1""".format(username)
cursor.execute(query)

res = cursor.fetchone()
if not res:
return "There's no such user {0}!\n".format(username)
user_id, password_hash, salt = res

calculated_hash = hashlib.sha256(password + salt)
if calculated_hash.hexdigest() != password_hash:
return "That's not the password for {0}!\n".format(username)

Issue

There's little input validation on username before it is used to constrcut a SQL query. There's no encoding applied when constructing the SQL query string which is used to, given a username, produce the hashed password and the associated salt. Accordingly one can make username a part of a SQL query command which ensures the original select returns nothing and provide a new SELECT via a UNION that returns some literal values for the hash and salt. For instance the following in blue is the query template and the red is the username injected SQL code:

SELECT id, password_hash, salt FROM users WHERE username = 'doesntexist' UNION SELECT id, ('5e884898da28047151d0e56f8dc6292773603d0d6aabbdd62a11ef721d1542d8') AS password_hash, ('word') AS salt FROM users WHERE username = 'bob' LIMIT 1
In the above I've supplied my own salt and hash such that my salt (word) plus my password (pass) hashed produce the hash I provided above. Accordingly, by providing the above long and interesting looking username and password as 'pass' I can login as any user.

Notes

Code review red flag is again using strings to query the database. Although this level was made more difficult by using an API that returns only a single row and by using the execute method which only runs one command. I was forced to (as a SQL noob) learn the syntax of SELECT in order to figure out UNION and how to return my own literal values.

PermalinkCommentssecurity sql sql-injection technical web-security

Creating Accelerators for Other People's Web Services

2009 Aug 18, 4:19

Before we shipped IE8 there were no Accelerators, so we had some fun making our own for our favorite web services. I've got a small set of tips for creating Accelerators for other people's web services. I was planning on writing this up as an IE blog post, but Jon wrote a post covering a similar area so rather than write a full and coherent blog post I'll just list a few points:

PermalinkCommentstechnical accelerator ie8 ie

IE8 Search Providers, Accelerators, and Local Applications Hack

2009 Jul 25, 3:23

There's no easy way to use local applications on a PC as the result of an accelerator or a search provider in IE8 but there is a hack-y/obvious way, that I'll describe here. Both accelerators and search providers in IE8 fill in URL templates and navigate to the resulting URL when an accelerator or search provider is executed by the user. These URLs are limited in scheme to http and https but those pages may do anything any other webpage may do. If your local application has an ActiveX control you could use that, or (as I will provide examples for) if the local application has registered for an application protocol you can redirect to that URL. In any case, unfortunately this means that you must put a webpage on the Internet in order to get an accelerator or search provider to use a local application.

For examples of the app protocol case, I've created a callto accelerator that uses whatever application is registered for the callto scheme on your system, and a Windows Search search provider that opens Explorer's search with your search query. The callto accelerator navigates to my redirection page with 'callto:' followed by the selected text in the fragment and the redirection page redirects to that callto URL. In the Windows Search search provider case the same thing happens except the fragment contains 'search-ms:query=' followed by the selected text, which starts Windows Search on your system with the selected text as the query. I've looked into app protocols previously.

PermalinkCommentstechnical callto hack accelerator search ie8

PowerShell Scanning Script

2009 Jun 27, 3:42

I've hooked up the printer/scanner to the Media Center PC since I leave that on all the time anyway so we can have a networked printer. I wanted to hook up the scanner in a somewhat similar fashion but I didn't want to install HP's software (other than the drivers of course). So I've written my own script for scanning in PowerShell that does the following:

  1. Scans using the Windows Image Acquisition APIs via COM
  2. Runs OCR on the image using Microsoft Office Document Imaging via COM (which may already be on your PC if you have Office installed)
  3. Converts the image to JPEG using .NET Image APIs
  4. Stores the OCR text into the EXIF comment field using .NET Image APIs (which means Windows Search can index the image by the text in the image)
  5. Moves the image to the public share

Here's the actual code from my scan.ps1 file:

param([Switch] $ShowProgress, [switch] $OpenCompletedResult)

$filePathTemplate = "C:\users\public\pictures\scanned\scan {0} {1}.{2}";
$time = get-date -uformat "%Y-%m-%d";

[void]([reflection.assembly]::loadfile( "C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Drawing.dll"))

$deviceManager = new-object -ComObject WIA.DeviceManager
$device = $deviceManager.DeviceInfos.Item(1).Connect();

foreach ($item in $device.Items) {
        $fileIdx = 0;
        while (test-path ($filePathTemplate -f $time,$fileIdx,"*")) {
                [void](++$fileIdx);
        }

        if ($ShowProgress) { "Scanning..." }

        $image = $item.Transfer();
        $fileName = ($filePathTemplate -f $time,$fileIdx,$image.FileExtension);
        $image.SaveFile($fileName);
        clear-variable image

        if ($ShowProgress) { "Running OCR..." }

        $modiDocument = new-object -comobject modi.document;
        $modiDocument.Create($fileName);
        $modiDocument.OCR();
        if ($modiDocument.Images.Count -gt 0) {
                $ocrText = $modiDocument.Images.Item(0).Layout.Text.ToString().Trim();
                $modiDocument.Close();
                clear-variable modiDocument

                if (!($ocrText.Equals(""))) {
                        $fileAsImage = New-Object -TypeName system.drawing.bitmap -ArgumentList $fileName
                        if (!($fileName.EndsWith(".jpg") -or $fileName.EndsWith(".jpeg"))) {
                                if ($ShowProgress) { "Converting to JPEG..." }

                                $newFileName = ($filePathTemplate -f $time,$fileIdx,"jpg");
                                $fileAsImage.Save($newFileName, [System.Drawing.Imaging.ImageFormat]::Jpeg);
                                $fileAsImage.Dispose();
                                del $fileName;

                                $fileAsImage = New-Object -TypeName system.drawing.bitmap -ArgumentList $newFileName 
                                $fileName = $newFileName
                        }

                        if ($ShowProgress) { "Saving OCR Text..." }

                        $property = $fileAsImage.PropertyItems[0];
                        $property.Id = 40092;
                        $property.Type = 1;
                        $property.Value = [system.text.encoding]::Unicode.GetBytes($ocrText);
                        $property.Len = $property.Value.Count;
                        $fileAsImage.SetPropertyItem($property);
                        $fileAsImage.Save(($fileName + ".new"));
                        $fileAsImage.Dispose();
                        del $fileName;
                        ren ($fileName + ".new") $fileName
                }
        }
        else {
                $modiDocument.Close();
                clear-variable modiDocument
        }

        if ($ShowProgress) { "Done." }

        if ($OpenCompletedResult) {
                . $fileName;
        }
        else {
                $result = dir $fileName;
                $result | add-member -membertype noteproperty -name OCRText -value $ocrText
                $result
        }
}

I ran into a few issues:

PermalinkCommentstechnical scanner ocr .net modi powershell office wia

Thoughts on registerProtocolHandler in HTML 5

2009 Apr 7, 9:02

I'm a big fan of the concept of registerProtocolHandler in HTML 5 and in FireFox 3, but not quite the implementation. From a high level, it allows web apps to register themselves as handlers of an URL scheme so for (the canonical) example, GMail can register for the mailto URL scheme. I like the concept:

However, the way its currently spec'ed out I don't like the following: PermalinkCommentsurl template registerprotocolhandler firefox technical url scheme protocol boring html5 uri urn

Set Gmail as Default Mail Client in Ubuntu :: the How-To Geek

2008 Apr 3, 6:48The comments have info on URI template for gmail message composition: "https://mail.google.com/mail?view=cm&tf=0&to=`echo $1 | sed 's/mailto://'`"PermalinkCommentsgmail mail uri howto reference google

"How do I search my Gmail mailbox?": Tech Support from Ask Dave Taylor!

2008 Apr 3, 2:49Looking for URI template to search over my gmail and found it in the comments: "http://gmail.google.com/gmail?search=query&view=tl&fs=1&q=%s"PermalinkCommentsgmail email google reference uri search howto

WebSlices now appearing in a Wikipedia article near you - istartedsomething

2008 Mar 28, 10:07"Trust the open-source lovin' contributors at Wikipedia to be early adopters of Microsoft web technologies. Beginning just a couple of days ago, Wikipedia user "Soum Yasch" began building Wiki templates to support the new content-subscription featurPermalinkCommentsie8 ie browser wikipedia article

Reusing Internet Explorer's Builtin CSS

2008 Jan 29, 9:32

When throwing together an HTML page at work that other people will view, I stick the following line in for style. Its IE's error page CSS and contaits a subtle gradient background that I like.

This uses the res URI scheme. You can see the other interesting IE resources using my resource list tool.PermalinkCommentsresource technical css internet-explorer ie res

XSL Identity Transfom

2007 Oct 12, 4:08As noted in the XSL Transformations spec you can create the identity transform using the xsl:copy element. With the MSXML implementation of xsl:copy the example the spec gives produces slightly ugly elements. For instance given it produces . In order to ensure empty elements turn out pretty I've modified the example as follows:
    
        
            
                
                    
                
            
            
                
                    
                
            
        
    

This got me thinking about inverting XSLTs. Clearly in general an XSLT isn't invertible since an XSLT can completely ignore the input XML and produce something else entirely but then the above is an example of an XSLT that is invertible. So there is a subset of XSLTs that are invertible, how might you produce the inverse of an XSLT, and would this ever be useful?PermalinkCommentsxml msxml inverse xlst xsl

XSL Transforms in JavaScript

2007 Oct 7, 4:12In a previous post I mentioned an xsltproc like js file I made. As noted in that post, on Windows you can write console script files in JavaScript, name them foo.js, and execute them from the command prompt. I later found that MSDN has an XSLT javascript sample which looks similar to mine, but I like mine better for the XSLT parameter support and having a non-ridiculous way of interpreting filenames. The code for my xsltproc.js follows. The script is very simple and demonstrates the ease with which you can manipulate these system objects and all it takes is opening up notepad.
var createNewXMLObj = function() {
   var result = new ActiveXObject("MSXML2.FreeThreadedDOMDocument");
   result.validateOnParse = false;
   result.async = false;
   return result;
}

var args = WScript.arguments;
var ofs = WScript.CreateObject("Scripting.FileSystemObject");

var xslParams = [];
var xmlStyle = null;
var xmlInput = null;
var inputFile = null;
var outputFile = null;
var error = false;

for (var idx = 0; idx < args.length && !error; ++idx)
   if (args.item(idx) == "-o") {
      if (idx + 1 < args.length) {
         outputFile = ofs.GetAbsolutePathName(args.item(idx + 1));
         ++idx;
      }
      else
         error = true;
   }
   else if (args.item(idx) == "--param" || args.item(idx) == "-param") {
      if (idx + 2 < args.length) {
         xslParams[args.item(idx + 1)] = args.item(idx + 2);
         idx += 2;
      }
      else
         error = true;
   }
   else if (xmlStyle == null) {
      xmlStyle = createNewXMLObj();
      xmlStyle.load(ofs.GetAbsolutePathName(args.item(idx)));
   }
   else if (xmlInput == null) {
      inputFile = ofs.GetAbsolutePathName(args.item(idx));
      xmlInput = createNewXMLObj();
      xmlInput.load(inputFile);
   }

if (xmlStyle == null || xmlInput == null || error) {
   WScript.Echo('Usage:\n\t"xsltproc" xsl-stylesheet input-file\n\t\t["-o" output-file] *["--param" name value]');
}
else {
   var xslt = new ActiveXObject("MSXML2.XSLTemplate.3.0");
   xslt.stylesheet = xmlStyle;
   var xslProc = xslt.createProcessor();
   xslProc.input = xmlInput;

   for (var keyVar in xslParams)
      xslProc.addParameter(keyVar, xslParams[keyVar]);

   xslProc.transform();

   if (outputFile == null)
      WScript.Echo(xslProc.output);
   else {
      var xmlOutput = createNewXMLObj();
      xmlOutput.loadXML(xslProc.output);
      xmlOutput.save(outputFile);
   }
}
PermalinkCommentsjs xml jscript windows xslt technical xsltproc wscript xsl javascript

New XSLT - IE7 XML Source View Upgrade Part 2

2007 May 11, 8:55Last time, I had written some resource tools to allow me to view and modify Windows module resources in my ultimate and noble quest to implement the XML content-type fragment in IE7. Using the resource tools I found that MSXML3.DLL isn't signed and that I can replace the XSLT embedded resource with my own, which is great news and means I could continue in my endevour. In the following I discuss how I came up with this replacement for IE7's XML source view.

At first I thought I could just modify the existing XSLT but it turns out that it isn't exactly an XSLT, rather its an IE5 XSL. I tried using the XSL to XSLT converter linked to on MSDN, however the resulting document still requires manual modification. But I didn't want to muck about in their weird language and I figured I could write my own XSLT faster than I could figure out how theirs worked.

I began work on the new XSLT and found it relatively easy to produce. First I got indenting working with all the XML nodes represented appropriately and different CSS classes attached to them to make it easy to do syntax highlighting. Next I added in some javascript to allow for closing and opening of elements. At this point my XSLT had the same features as the original XSL.

Next was the XML mimetype fragment which uses XPointer, a framework around various different schemes for naming parts of an XML document. I focused on the XPointer scheme which is an extended version of XPath. So I named my first task as getting XPaths working. Thankfully javascript running in the HTML document produced by running my XSLT on an XML document has access to the original XML document object via the document.XMLDocument property. From this this I can execute XPaths, however there's no builtin way to map from the XML nodes selected by the XPath to the HTML elements that I produced to represent them. So I created a recursive javascript function and XSLT named-template that both produce the same unique strings based on an XML node's position in the document. For instance 'a3-e2-e' is the name produced for the 3rd attribute of the second element of the root element of the XML document. When producing the HTML for an XML node, I add an 'id' attribute to the HTML with the unique string of the XML node. Then in javascript when I execute an XPath I can discover the unique string of each node in the selected set and map each of them to their corresponding positions in the HTML.

With the hard part out of the way I changed the onload to get the fragment of the URI of the current document, interpret it as an XPath and highlight and navigate to the selected nodes. I also added an interactive floating bar from which you can enter your own XPaths and do the same. On a related note, I found that when accessing XML files via the file URI scheme the fragment is stripped off and not available to the javascript.

The next steps are of course to actually implement XPointer framework parsing as well as the limited number of schemes that the XPointer framework specifies.PermalinkCommentsxml xpointer msxml res xpath xslt resource ie7 technical browser ie xsl

Missing Bee Roundup

2007 Apr 15, 4:06For the past several months I've seen various articles suggesting why bees are disappearing. At first I thought this was another crackpot's article that somehow made it onto digg.com. But they keep coming and sometimes from credible sources. After the article I saw tonight I thought I should go back and put together the various articles I've read on this topic. Bees may be disappearing due to pesticides, new organic pathogens, genetically modified crops, mobile phones, or climate change. Apparently, the US hasn't been keeping accurate counts of its bees so we don't know the extent of the situation. There's an interview with Maryann Frazier, M.S., of the Dept. of Etymology at Penn State and a congressional hearing on the matter.

I know this is all very serious and could signal the end of our ecosystem as we know it, but I can't help throwing in the following links as well. The bees could be hiding in this Florida couple's kitchen. Or perhaps they're laying low while being trained by the government to fight terrorism. Or they're hiding in extra dimensions that we mere humans can't perceive (I'm fairly certain that's what this article is suggesting. Really. Read it. Seriously. Its awesome.)PermalinkCommentsroundup personal bees nontechnical

Delicious shortcut tag

2007 Apr 8, 3:05Shortcut Tag?
I just saw this on another user's delicious links: a link to ESV search that's tagged with, among other things, "shortcut:esv". When viewed on del.icio.us there's a text box that lets you search using that link. I hadn't seen this before, but it seems pretty cool and I'm surprised I hadn't seen it previously. A delicious post with such a tag ends up looking like the following: I tried searching for information on this and I've found other delicious users doing the same thing, but nothing about the tag itself. If you know any information especially official information from del.icio.us itself please post links in reply to this post. So without further preface here's what I've learned about the del.icio.us shortcut tag.

How-to
To get a search box in your del.icio.us links make a post that satisfies the following requirements:
  1. One of the tags must begin with the text 'shortcut:'. You can have more text following that in the tag if you like but it must at least start with 'shortcut:'.
  2. The 'url' you post must be a shortcut url rather than an actual URL. It must contain a '%s' with a lowercase 's'. When you enter text into the textbox on the del.icio.us page the text will replace the '%s' after being percent-encoded. For example 'http://www.google.com/search?hl=en&q=%s' is the shortcut url for Google and if you type 'foo bar' into the textbox the URI you will navigate to would be 'http://www.google.com/search?hl=en&q=foo%20bar'.


Complaints
This is neat but I do have a few complaints:
  1. The text from the textbox is percent-encoded before replacing the '%s'. Most sites use application/x-www-form-urlencoded which encodes spaces as '+' rather than '%20'.
  2. The shortcut url format seems to be taken from Mozilla's Firefox Custom Keywords. Its a shame it wasn't based on something more adaptable like the OpenSearch URL template syntax.
  3. A '%s' in the url means technically what you're submitting to del.icio.us isn't a URI as defined by the standard.
  4. Allowing text after 'shortcut:' means you can't look at all of a user's shortcut using this tag.


The next step is to create a tool to sync my IE7 search providers with my shortcuts saved to delicious...PermalinkCommentstechnical howto tagging tool tag delicious

Index: The Standard Template Library

2005 Apr 22, 12:45PermalinkCommentsreference stl development
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