I am developing a web app. which will generate a random link pointing to an image on my server. something like -http://dummy.com/Images/Image1.jpg?id=19234
Here this link can then be used by anybody on their site, now I just want to know how many sites are using my links, without anybody clicking on those links.
Can It be done using HTTPModule ??
Is this as simple as Googling? Search for
link:http://dummy.com/Images/Image1.jpg?id=19234
If you want to do this programmatically, you'll need to use the Google API.
The issue you'd have with an HttpHandler is that it will generally only kick in for requests that are being handled by the ASP.Net engine - the image requests will normally be handled by IIS without going through the handler.
Your web logs should be able to tell you who the referers for any given item on your servers are - assuming that you have them, and you hve something to process them - this will be more accurate than using Google.
Going forward, one of the ways I've done this in the past is to have the image generated by an HttpHandler (implementing IHttpHandler).
This will return the image as a stream (setting the content type to "image/jpeg"), and you can add further processing (such as logging where the request (referer) came from, etc).
The limitation I found with the HttpHandler, is that some services (PBBS for example) require an image link to have an image extension - I got around this by processing all 404's with an ASP.Net page that checks for the .jpg extension in the request. If it finds one, instead of returning the usual 404 page, it returns the requeted image. You'll need to configure the 404 handler in IIS though, as the web.config error handler only kicks in for ASP.Net requests (web services and .aspx type pages).
Example handler:
// Sample from the ASP.Net Personal Web Site Starter Kit
public class Handler : IHttpHandler
{
public bool IsReusable
{
get { return true; }
}
public void ProcessRequest(HttpContext context)
{
// Set up the response settings
context.Response.ContentType = "image/jpeg";
context.Response.Cache.SetCacheability(HttpCacheability.Public);
context.Response.BufferOutput = false;
// QueryString parameters are available here:
// context.Request.QueryString["QueryStringKey"]
// You can also access the Referrer object, and log the requests here.
Stream stream;
// Read your image into the stream, either from file system or DB
if (stream == null)
{
stream = PhotoManager.GetPhoto();
}
// Write image stream to the response stream
const int buffersize = 1024 * 16;
var buffer = new byte[buffersize];
int count = stream.Read(buffer, 0, buffersize);
while (count > 0)
{
context.Response.OutputStream.Write(buffer, 0, count);
count = stream.Read(buffer, 0, buffersize);
}
}
}
You can have similar code (or better yet, refactor the main image streaming code into a shared class) in the 404 page, that checks for the existence of the image extension, and renders the image out that way (again, setting the content type, etc).
Oddthinking is right. See http://code.google.com/intl/en/apis/ajaxsearch/documentation/#fonje_snippets or Google's API. They give examples for PHP and Java, but there are also AJAX frameworks for ASP.NET (http://www.asp.net/ajax/), and I'm sure C# as well.
You can change your image extension to an aspx extension (http://dummy.com/Images/Image1.aspx?id=19234), there is no problem in this, because this page the only thing it would do Response.OutputStream of the image. That is to say it would be similar to a jpg but with the advantage you can have some other code to process.
In this aspx (before outputing the image), we would ask about the http_referer and it would be stored in a data table if this registry does not exist.
This is really useful if for example you want to restrict the access to images. You could add some logic to forbid if they are not logged in.
Related
I have a web site (IIS, C#.Net, MVC4) where users are (forms-)authenticated and they upload media files (mostly .mp4) and authorize set of users to play back on demand. I store these files on local storage.
I play these files using jwplayer back to the authorized users on demand.
jwplayer expects I pass the url directly for it to play, but I didn't want to expose a direct url.
I really have to restrict unauthorized access to these files as they are private files.
I tried implementing a controller method to handle https://mysite/Video/Watch?VideoId=xyz, and return FileStream of the actual file. It works on a browser directly. (Though not sure how efficient it is for large files.)
But the problem is, jwplayer looks for urls of pattern http(s)://domain/path/file.mp4[?parameter1=value1¶meter2=value2 and so on.]
When I give a url like https://mysite/Video/Watch?VideoId=xyz, it says 'No playable sources found' without even sending a HEAD request.
If I expose the urls directly, the files are available for anybody to download, which will break the privacy.
Worst case, I would at least want to avoid hot links which will live for ever.
I have also looked at www.jwplayer.com/blog/securing-your-content/ but did not find the solutions suitable.
My questions are,
Is there a way I can retain the pattern of the url http(s)://domain/path/file.mp4 and still control the access to the file?
If (1.) is not possible, how do I leverage the parameters that could be passed on the url. With the parameters, I can think of signed urls. What should I do on the server if I have to provide and handle/validate signed urls.
Just not to hinder the performance, after any validation, can I somehow get the iis to handle the filestream rather my code?
I implemented an HTTPModule to allow/block access to the file. This addresses my questions 1 & 3.
Code snippet below.
void context_PreRequestHandlerExecute(object sender, EventArgs e)
{
HttpApplication app = sender as HttpApplication;
//Get the file extension
string fileExt= Path.GetExtension(app.Request.Url.AbsolutePath);
//Check if the extension is mp4
bool requestForMP4 = fileExt.Equals(".mp4", StringComparison.InvariantCultureIgnoreCase);
//If the request is not for an mp4 file, we have nothing to do here
if (!requestForMP4)
return;
//Initially assume no access to media
bool allowAccessToMedia = false;
//....
// Logic to determine access
// If allowed set allowAccessToMedia = true
// otherwise, just return
//....
if(!allowAccessToMedia)
{
//Terminate the request with HTTP StatusCode 403.2 Forbidden: Read Access Forbidden
app.Response.StatusCode = (int)HttpStatusCode.Forbidden;
app.Response.SubStatusCode = 2;
app.CompleteRequest();
}
}
I have an application which intended to stream videos back from our local DB. I spent a lot of time yesterday attempting to return the data a either a RangeFileContentResult or RangeFileStreamResult without success.
In short, when I return the file as either of these two results I cannot seem to get a video to stream correctly (or play at all).
The request from the browser gets sent with the following headers:
Range: bytes=0-
And the response comes provided gives these headers as an example:
Accept-Ranges: bytes
Content-Range: bytes 0-5103295/5103296
In terms of network traffic, I get a series of 206's for partial results, then a 200 at the end (according to fiddler) which seems correct.
Chrome's network tab disagrees with this and see's an initial request (always 13 bytes which I assume is a handshake) then a couple more requests which have a status of either cancelled or pending.
As far as I understand, this is more or less correct, 206 - cancel, 206 - cancel etc. But the video never plays.
If I switch the result from my controller to a FileResult, the video plays and Chrome, IE10 and Firefox and appears to begin playing before the end of the download is completed (which feels a little like it's streaming! although I suspect it's not)
But with the range result I get nothing in chrome or IE and the entire video downloads in one drop in firefox.
As far as I understood, the RangeFileContentResult should handle responding to the client with a range of bytes to download (which mine doesn't seem to do, it just tells it to get the whole file (illustrated by the response above)). And the client should respond to that, which it doesn't seem to do.
Does anyone have any thoughts in this area? Specifically:
a) Should RangeFileContentResult be sending a range of bytes back to the client?
b) Is there any way I can explicitly control the range of bytes requested from the client side?
c) Is there any reason or anything I'm doing wrong here which would cause browsers not to load the video at all, when requesting a RangeFileContentResult?
EDIT: Added a diagram to help describe what I'm seeing:
EDIT2: Ok, so the plot thickens. Whilst playing around with the RangedFile gubbins we needed to push another system test version out and I left the 'RangeFileContentResult' on my controller action as below:
private ActionResult RetrieveVideo(MediaItem media)
{
return new RangeFileContentResult(
media.Content,
media.MimeType,
media.Id.ToString(),
DateTime.Now);
}
Rather oddly, this now seems to work as expected on our Azure system test environment but still not on my local machine. I wonder if there's something IIS based which works happily on Azures IIS8, but not on my local 7.5 instance?
The reason of the issue described here is the value passed to modificationDate parameter of RangeFileContentResult constructor:
return new RangeFileContentResult(media.Content, media.MimeType, media.Id.ToString(), DateTime.Now);
This date is used by the RangeFileResult in order to create two headers:
ETag - This header is an identifier used by browser and server to make sure that they are speaking about the same entity.
Last-Modified - This header informs the browser about the last modification date of the entity.
The fact that a DateTime.Now is being passed every time the browser makes partial request might be a reason for ETag and Last-Modified headers values to change before the client will get the whole entity (usually if the entire process takes longer than one second).
In case described above, the browser is sending If-Range header with the request. This header is telling the server that the entire entity should be resend if the entity tag (or modification date because If-Range can carry either one of those two values) doesn't much. This is what happens in this case.
The fact that modification date is "dynamic" may also cause further issues if client decides to use one of following headers for verification: If-Modified-Since, If-Unmodified-Since, If-Match, If-None-Match.
The solution in this situation is to keep a modification date in database with the file to make sure it is consistent.
There is also a place for optimization here. Instead of grabbing the whole video from DB every time a partial request is being made, one can either cache it or grab only the relevant part (if the database engine which application is using allows such an operation). Such a mechanism can be used in order to create specialized action result by delivering from RangeFileResult and overwriting WriteEntireEntity and WriteEntityRange methods.
Ok So I didn't have enough time to look at RangeFileResult in details, but I have just downloaded the file (RangeFileContentResult) from
RangeFileContentResult
and modified my code so it looks like
public ActionResult Movie()
{
byte[] file = System.IO.File.ReadAllBytes(#"C:\HOME\asp\Java\Java EE. Programming Spring 3.0\01.avi");
return new RangeFileContentResult(file, "video/x-msvideo", "01.avi", DateTime.Now);
}
and again it works. However, I noticed that when I stop the video I have an exception and it happens in RangeFileResult
if (context.HttpContext.Response.IsClientConnected)
{
WriteEntityRange(context.HttpContext.Response, RangesStartIndexes[i], RangesEndIndexes[i]);
if (MultipartRequest)
context.HttpContext.Response.Write("\r\n");
context.HttpContext.Response.Flush();
}
So you better modify the code to handle it.In terms when users already disconnected , but you are still trying to send them a response.
Again, technically it's not a big difference whether you pass byte[] or Stream , because even when you pass Stream the code working with it
using (FileStream)
{
FileStream.Seek(rangeStartIndex, SeekOrigin.Begin);
int bytesRemaining = Convert.ToInt32(rangeEndIndex - rangeStartIndex) + 1;
byte[] buffer = new byte[_bufferSize];
while (bytesRemaining > 0)
{
int bytesRead = FileStream.Read(buffer, 0, _bufferSize < bytesRemaining ? _bufferSize : bytesRemaining);
response.OutputStream.Write(buffer, 0, bytesRead);
bytesRemaining -= bytesRead;
}
}
again reads data and puts them into an byte[] array!.... So it's up to you!
BUT... I suggest that you pay attention to a content type that you provide!!!
Point is that your browser must be able to handle it!So if you provide something unknown definitely you will have problems.To find your content type string please check
mime-types-by-content-type
Again I just gave a quick look and if you have problems I will help you later when come home.
mofiPlease just copy these two files in your mvc project
RangeFileResult
RangeFileStreamResult
public ActionResult Movie()
{
var path = new FileStream(#"C:\temp\01.avi", FileMode.Open);
return new RangeFileStreamResult(path, "video/x-msvideo", "01.avi", DateTime.Now);
}
Now run your project and open in chrome (for example: http://youraddress.com:45454/Main/Movie) you should see your file playing using a standard chrome video player. it's streaming and you can see it if you put a breakpoint at
return new RangeFileStreamResult(path, "video/x-msvideo", "01.avi", DateTime.Now);
Again the source is easy to modify to change the buffer size which is used for streaming!
I have a problematic bug in a production system, which I simply can’t find. Sometimes the system produces an invalid link. When the end-user clicks it I get an error report from the system, and the end-user gets an error message. The URL’s that fail are like this:
http://www.mysite.com/somepath/undefined/
The “undefined” part is the problem, which I think is produced by JavaScript, but I like to make sure it’s not from the back-end.
Is there a way to save every response to a file if it contains the string “/undefined/” using global.asax?
I’ve tried this:
protected void Application_EndRequest(object sender, EventArgs e)
{
TextReader t = new StreamReader(Response.OutputStream);
string content = t.ReadToEnd();
// look for "/undefined/" and save to a temp file is the easy part after this
}
But is says that OutputStream is not readable.
I don’t know for certain which page/ajax request that produces the faulty link, so I need to inspect every response.
You cannot read the response stream, but you can add a response filter to the output stream, and get a copy of it.
There are several related artiles on this:
Logging raw HTTP request/response in ASP.NET MVC & IIS7 here at
SO
Capturing and Transforming ASP.NET Output with
Response.Filter by Rick Strahl.
Hope, this will help you.
Juest check the IIS log file. I tracks all request with urls
I have a script, which by using several querystring variables provides an image. I am also using URL rewriting within IIS 7.5.
So images have an URL like this:
http://mydomain/pictures/ajfhajkfhal/44/thumb.jpg
or
http://mydomain/pictures/ajfhajkfhal/44.jpg
This is rewritten to:
http://mydomain/Picture.aspx?group=ajfhajkfhal&id=44&thumb=thumb.jpg
or
http://mydomain/Picture.aspx?group=ajfhajkfhal&id=44
I added caching rules to IIS to cache JPG images when they are requested. This works with my images that are REAL images on the disk. When images are provided through the script, they are somehow always requested through the script, without being cached.
The images do not change that often, so if the cache at least is being kept for 30 minutes (or until file change) that would be best.
I am using .NET/C# 4.0 for my website. I tried setting several cache options in C#, but I cant seem to find how to cache these images (client-side), while my static images are cached properly.
EDIT I use the following options to cache the image on the client side, where 'fileName' is the physical filename of the image (on disk).
context.Response.AddFileDependency(fileName);
context.Response.Cache.SetETagFromFileDependencies();
context.Response.Cache.SetLastModifiedFromFileDependencies();
context.Response.Cache.SetCacheability(HttpCacheability.Public);
context.Response.Cache.SetExpires(DateTime.Now.AddTicks(600));
context.Response.Cache.SetMaxAge(new TimeSpan(0, 5, 0));
context.Response.Cache.SetSlidingExpiration(true);
context.Response.Cache.SetValidUntilExpires(true);
context.Response.ContentType = "image/jpg";
EDIT 2 Thanks for pointing that out, that was indeed a very stupid mistake ;). I changed it to 30 minutes from now (DateTime.Now.AddMinutes(30)).
But this doesnt solve the problem. I am really thinking the problem lies with Firefox. I use Firebug to track each request and somehow, I am thinking I am doing something fundamentally wrong. Normal images (which are cached and static) give back an response code "304 (Not Modified)", while my page always gives back a "200 (OK)".
alt text http://images.depl0y.com/capture.jpg
If what you mean by "script" is the code in your Picture.aspx, I should point out that C# is not a scripting language, so it is technically not a script.
You can use the Caching API provided by ASP.NET.
I assume you alread have a method which contains something like this. Here is how you can use the Caching API:
string fileName = ... // The name of your file
byte[] bytes = null;
if (HttpContext.Current.Cache[fileName] != null)
{
bytes = (byte[])HttpContext.Current.Cache[fileName];
}
else
{
bytes = ... // Retrieve your image's bytes
HttpContext.Current.Cache[fileName] = bytes; // Set the cache
}
// Send it to the client
Response.BinaryWrite(bytes);
Response.Flush();
Note that the keys you use in the cache must be unique to each cached item, so it might not be enough to just use the name of the file for this purpose.
EDIT:
If you want to enable caching the content on the client side, use the following:
Response.Cache.SetCacheability(HttpCacheability.Public);
You can experiment with the different HttpCacheability values. With this, you can specify how and where the content should be cached. (Eg. on the server, on proxies, and on the client)
This will make ASP.NET to send the client the caching rules with the appropriate HTTP headers.
This will not guarantee that the client will actually cache it (it depends on browser settings, for example), but it will tell the browser "You should cache this!"
The best practice would be to use caching on both the client and the server side.
EDIT 2:
The problem with your code is the SetExpires(DateTime.Now.AddTicks(600)). 600 ticks is only a fraction of a second... (1 second = 10000000 ticks)
Basically, the content gets cached but expires the moment it gets to the browser.
Try these:
context.Response.Cache.SetExpires(DateTime.Now.AddMinutes(5));
context.Response.Cache.SetMaxAge(TimeSpan.FromMinutes(5));
(The TimeSpan.FromMinutes is also more readable than new TimeSpan(...).)
I need to get the free Google charts working over SSL without any security errors. I am using c# and asp.net.
As Google charts does not support SSL by default, I am looking for a robust method of using there charts but ensuring my user doesn't get any security warnings over their browser.
One thought was to use a handler to call the charts api and then generate the output my site needs.
Similar to Pants are optional blog post. I haven't been able to get this example working at this stage.
Any suggestions, or samples are welcome.
Thanks
the Google Charts API is now available over HTTPS at via https at chart.googleapis.com.
Source: http://www.imperialviolet.org/2010/11/29/charthttps.html
We do this automatically in the NetQuarry Platform - it's pretty simple, although you do force the image to come through your site vs. charts.google.com, making your browser run the request through a single connection.
Since a chart is just a link to an image, what we do is to build the link to the chart (a much more complex process, obviously), then add the whole link to the query string on an internal handler (handler.ashx?req=chart& ). So the new link looks like this:
handler.ashx?act=chrt&req=chart&cht=p3&chs=450x170&chd=s:HAR9GBA&chl=New|In%20Progress|Responded|Won't%20Respond|On%20Hold|Future|Review|&chg=20,20,1,5&chg=10,25,1,5&chco=0A477D
Then, we simply download the image data and write it back as the response.
Here's the code:
Blockquote
private void GoogleChart(HttpContext cxt)
{
const string csPrefix = "?act=chrt&req=chart&";
HttpRequest req = cxt.Request;
HttpResponse rsp = cxt.Response;
string sUrl = cxt.Request.RawUrl;
int nStart = sUrl.IndexOf(csPrefix, StringComparison.OrdinalIgnoreCase);
rsp.Clear();
if (nStart > 0)
{
sUrl = "http://chart.apis.google.com/chart?" + sUrl.Substring(nStart + csPrefix.Length);
System.Net.WebClient wc = new System.Net.WebClient();
byte[] buffer = wc.DownloadData(sUrl);
cxt.Response.ClearContent();
cxt.Response.ClearHeaders();
cxt.Response.ContentType = "application/octet-stream";
cxt.Response.AppendHeader("content-length", buffer.Length.ToString());
cxt.Response.BinaryWrite(buffer);
}
}
I Have a partial solution that has one issue.
here is the link to my new post asking for help with a specific problem regarding my solution
My Attempt at a SSL handler