I'm currently applying security fixes for a vulnerability which was found by a third party software. This is the issue (Often Misused: HTTP Method Override vulnerability).
The request from the software was similar to:
POST /Home/ViewProfile HTTP/1.1
Referer: https://somesite.com/Home/ViewProfile?qrystr=blahblah
[...]
X-HTTP-METHOD: PUT
X-HTTP-Method-Override: PUT
X-METHOD-OVERRIDE: PUT
[...]
And the response was:
HTTP/1.1 200 OK
[...]
The web application is not a RESTful API, it's just a an ASP.NET MVC site which only has GET and POST actions.
I have a few questions:
Is this a false positive given the type of app?
By default, does ASP.NET do anything with these headers X-HTTP-Method, X-HTTP-Method-Override, X-METHOD-OVERRIDE if not explicitly told to do so such as in this example?
Regarding the first linked issue above, what is the best way to go about achieving the recommended remediations if they're necessary/applicable based on my case:
"Ensure that only the required headers are allowed, and that the allowed headers are properly configured."
and
"Ensure that no workarounds are implemented to bypass security measures implemented by user-agents, frameworks, or web servers."
Another thing to note is I don't have access to modify IIS settings, but I can modify the Web.Config.
I had the same problem with a scan from my security team. What I did was limiting the size of those requests to zero (0) in the web.config. The server then returns a "HTTP Error 431.0 - Request Header Fields Too Large", effectively blocking the overrides.
</system.webServer>
...
<security>
<requestFiltering>
<requestLimits>
<headerLimits>
<add header="X-Http-Method-Override" sizeLimit="0" />
<add header="X-Method-Override" sizeLimit="0" />
<add header="X-HTTP-Method" sizeLimit="0" />
</headerLimits>
</requestLimits>
...
</requestFiltering>
</security>
...
</system.webServer>
However, I haven't checked yet if this effectively cancels the alert by the security scanner. I suspect it might still show, but I'm ready to report back as a false positive because the server is blocking all calls with those headers. I'll let you know as soon as I get a response from the security team.
Related
I'm trying to appease a PCI scan failure we recently had done, in which it states:
Microsoft ASP.NET MS-DOS Device Name DoS
Synopsis :
A framework used by the remote web server has a denial of service vulnerability.
Impact:
The web server running on the remote host appears to be using Microsoft
ASP.NET, and may be affected by a denial of service vulnerability. Requesting a URL
containing an MS-DOS device name can cause the web server to become
temporarily unresponsive.
In a nutshell, we visit a URL on our app such as /AUX/.aspx we get a 500 error.
I'm using RequestFiltering to filter these requests out, and return 404's instead, without the server trying to process the request.
An excerpt of my web.config is below:
<system.webServer>
<security>
<requestFiltering>
<denyUrlSequences>
<add sequence="/AUX/.aspx" />
</denyUrlSequences>
</requestFiltering>
</security>
</system.webServer>
However, this isn't working, it's still returning a 500.
I would expect it to return a 404.
If I add the following catch-all url to the denyUrlSequences then the whole site produces the expected 404.
<add sequence="/" />
It's worth mentioning the application in question is an MVC app running on IIS 7.5 (Windows 2008 R2)
Just had to solve this problem.
My solution was to disable .Net Error Pages and enable IIS Error Pages.
When you move the custom error handling from the higher .Net level to the lower IIS level the HTTP response code changes from 500 to 404.
PCI Test Passed :-)
I struggled with this for quite some time myself. I think the 500 response code is correct for MS-DOS names in the URL, and you do not need to add anything to request filtering.
You'll notice that you will get a 500 error if you use any of the MS-DOS names (https://support.microsoft.com/en-us/kb/74496) without doing anything to your configuration. However, if you add a RequestFiltering denySequence for something else, like "foo", then you will see the 404.5 error when browsing to /foo.
If you add relaxedUrlToFileSystemMapping="true" to the httpRuntime element along with your request filtering denySequence entries, then you will get the 404.5 for MS-DOS names.
But disabling the default asp.net configuration just so you can get something other then a 500 response for a URL with MS-DOS name is a rediculous request from a PCI compliance check.
So I'm reading up on these and am a little confused. I'm using an iframe of a site on another domain. I get No 'Access-Control-Allow-Origin' header is present on the requested resource.” Reading up on this I can just set the header in the web.config. However, I want multiple specific domains and not just the wildcard "*". I was reading up on the cross domain policy. Creating an xml file Is this by any means related or are these two completely different things?
This xml policy
<?xml version="1.0"?>
<cross-domain-policy>
<allow-access-from domain="domain1.com"/>
<allow-access-from domain="domain2.com"/>
</cross-domain-policy>
vs this in the web.config
<system.webServer>
<httpProtocol>
<customHeaders>
<add name="Access-Control-Allow-Origin" value="site1.com" />
</customHeaders>
</httpProtocol>
</system.webServer>
CORS works by adding a special header to responses from a server to the client. If a response contains the Access-Control-Allow-Origin header, and if the browser supports CORS, then there is a chance you can load the resource directly with Ajax no need for a proxy.
When you set, Access-Control-Allow-Origin value as “site1.com”.
With this configuration, only scripts that originate from http://site1.com are allowed to load resources. Any other domain trying to use Ajax to load resources will be given the standard security error message. In this way, site owners can limit which domains are allowed to load their resources with CORS.
Alternatively, site owners can grant wide-open access with the always ready to party asterisk:
Access-Control-Allow-Origin: *.
Now, any site that wants to load a resource directly using Ajax can do so without getting the browser security error. It's a very helpful technique for modern apps that often load data using JavaScript, and hopefully more modern web APIs will start to support CORS.
I have a server that sits behind an Incapsula Web App Firewall, which alters the headers sent to IIS. When I perform a specific request I get the following error from IIS: The server committed a protocol violation. Section=ResponseHeader Detail=CR must be followed by LF. This behavior is also described in: http://www.dragonblogger.com/fix-live-writer-protocol-violation-error-cr-lf/
According to this page http://msdn.microsoft.com/en-us/library/65ha8tzh%28v=vs.80%29.aspx I should be able to accept these headers by setting the useUnsafeHeaderParsing to true. So I tried adding this to the web.config in the virtual directory from which the specific request should be handled:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.net>
<settings>
<httpWebRequest useUnsafeHeaderParsing="true" />
</settings>
</system.net>
</configuration>
After restarting IIS it still does not work. I also tried adding this to the c:\windows\Microsoft.NET\framework\config\web.conf but it did not work either.
Does anyone have any idea what I am missing?
Thanks!
When trying to connect Azure Application Insights to one of our websites (also "protected" by Incapsula) we encountered the same response header violation. Setting the useUnsafeHeaderParsing to true didn't work either.
Consulting the Incapsula support desk helped us out: it seems that Incapsula is adding an irregular cookie to the response to identify the visitor as a bot or as a human visitor. The addition of the irregular cookie the to the response can be the cause of the response header violation. Incapsula also has Javascript classification, so we let them disable the irregular cookie and enable the Javascript classification.
This is how we solved the violation error.
We have to send a large packet to an ASP.Net web service through the URL. We cannot use POST for certain reasons, so we are URL encoding an XML package and we make a GET request to the service.
http://service.example.com/collect?content=AAAAAAAA...(+5000 characters)
The service responds with
Error 404 - File or directory not found.
I have read that there is no error code for max-content-length-exceeded so IIS sends back this 404 error. Knowing that, I have changed the configuration in the following way to allow large requests:
Changed query string length, max URL length, max request length and deactivated validation
<httpRuntime
requestValidationMode="2.0"
maxQueryStringLength="262144000"
maxUrlLength="262144000"
maxRequestLength="262144000" />
...
<pages validateRequest="false" />
...
<system.webServer>
<validation validateIntegratedModeConfiguration="false" />
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="262144000" />
</requestFiltering>
</security>
</system.webServer>
I still receive the same error. How do I make a request to my web service with an extremely large/long URL?
Update 1
I am not sending images. The content is something like:
<packet date="1243235246436">
<param type="1" id="45">
5
</param>
</packet>
without the new line characters and URL encoded.
Update 2
After setting the limits to a larger number in the IIS Request Filtering the 404 is now transformed to
HTTP Error 400. The size of the request headers is too long.
This is because the size of the headers is too large now. Tried to follow the instructions from this article by adding the MaxFieldLength and MaxRequestBytes registry entries, but I am still capped at 16k URL length.
What can I do to be able to send 1,000,000 long URLs? Is this even possible? What can I do to send at least 65k long URLs? This is the max length a header can have, but my settings are not taken into consideration.
The MSDN documentation of maxQueryStringLength also talks about IIS filtering in case of very long URLs. Have you checked this ?
The property names mentioned there are a bit different: maxQueryString, maxUrl.
A GET request is only limited by a browser's limit on the length of the URL string.
In IE it is 2,083 characters, minus the number of characters in the actual path. Other browsers do not have a clearly defined limit on the length of the URL string. These articles might be helpful to you.
http://www.boutell.com/newfaq/misc/urllength.html
http://support.microsoft.com/kb/q208427
RFC 2616, "Hypertext Transfer Protocol -- HTTP/1.1," does not specify any requirement for URL length, so browsers are free to stipulate what they deem fit.
I can't seem to receive HTTP OPTIONS requests in my IIS6 hosted ASP.NET application. I'm testing it using a debug breakpoint (and file-log) in my Global.asax's Application_BeginRequest method. The breakpoint is never hit and the client gets a HTTP 403 Forbidden, I'm assuming from IIS6 directly (GETs and POSTs work fine btw).
I've tried several things in the web.config, including adding the following line to either and both the <system.webServer><handlers> and <system.web><httpHandlers> sections.
<add name="OptionsHandler" verb="OPTIONS" path="*" type="System.Web.DefaultHttpHandler"/>
I've also played with the <system.webServer><security><requestFiltering><verbs> settings and allowUnlisted="true" and <add verb="OPTIONS" allowed="true"/>.
Also, I'm not using URLScan or any other tools that might intercept the calls. In case you're interested in IISLogs:
2011-07-11 20:26:05 W3SVC1215124377 127.0.0.1 OPTIONS /test.aspx - 80 - 127.0.0.1 Mozilla/5.0+(Windows+NT+5.2;+rv:5.0)+Gecko/20100101+Firefox/5.0 403 1 0
Is there a way to receive OPTIONS request in an ASP.NET Application?
For IIS6, you will have to enable the OPTIONS verb explicitly in the management console, and you will also need to map it to be handlded by ASP .NET. Only then, you will be able to register your handler in <system.web> and get the request processed by ASP .NET.
(Note, <system.webServer> settings only applies to IIS7).