I am wondering if there is a safer way to use ColdFusion CFFILE to upload files to Of course, you only perform the image tests if the file uploaded is an image. You may want to use a third party tool like Alagad Image CFC or ColdFusion 8’s built in image support to not only confirm that the file is indeed. On UNIX systems should also restrict access to the uploaded file by specifying the mode attribute, preferably so that only the ColdFusion process can read.
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Allowing someone to upload a file on to your web server is a common requirement, but also a very risky operation. So here are some tips to help make this process more secure. The accept attribute gives a terrible false sense of security. The cffile accept attribute uses the mime type that your browser sends to the server.
It’s very easy to spoof the mime type. For this reason you need to ensure that cffile. Use a file extension whitelist rather uplowd a blacklist, in other words you don’t just check to make sure it is not a. This way if someone installs PHP on your server, you don’t have to update the code to block that file extension as well.
It supports jpg, gif, pdf, tiff, and more. If you do use IsImageFile just make sure that you have upgraded your JVM to one that doesn’t have the issue that can cause an image file to crash your server. See Mark Kruger’s blog entry for details. Suppose I ran the same hack above with cfhttp but you now have upooad in place to delete the file if the extension is incorrect. There is fcfile slight chance that I could execute that file before you can delete it if you uploaded it into the web root and I could predict where it would be placed.
If possible keep uploaded files outside of the web root and serve them with cfcontent.
ColdFusion CFFILE to limit text file upload – Stack Overflow
In some cases this is not possible, but seriously consider this as it does ease the risk significantly. Remove execute permissions from upload directories The reason for this should be obvious, but is something we often forget to do. If possible upload content to a server other than the application server, a server that only serves static content for example Amazon S3. Cfcile best to strip out non alpha numeric characters perhaps with the exception of dash and underscore.
The first setting is the maximum size of a POST, and therefor also a file upload. The default mb is probably bigger than needed for most web apps, you can lower it to mitigate DOS potential.
Chances are your web server is also capable of limiting the post size, on apache you can use the LimitRequestBody directive to do this. Cftile next setting Request Crfile Threshold should probably be lowered to 1MB, this puts any request larger than 1mb into a throttle for synchronous processing. The third setting Request Throttle Memory is the maximum size of request throttle queue. The default is kind of high, if you don’t have a lot of large file uploads going on at the same time this should be lowered to say 50mb it shouldn’t be lower than the Maximum size of post data, or the Request Throttle Threshold, but it could be equal to the max size.
If you are using the Enterprise edition of ColdFusion you can setup a sandbox for your file upload directory, and remove execute permission.
Use you should limit your uploads directory to only allow static files to be requested. Blog Consulting Products Contact Me. Don’t rely on cffile accept attribute The accept attribute gives a terrible false sense of security.
Always upload to a temp uplkad outside of the Web Root Suppose I ran the same hack above with cfhttp but you now have code in place to delete the file if the extension is incorrect. Once you have validated the upload, you can move it to its desired location. Keep uploaded files outside the web root If possible keep uploaded files outside of the web root and serve them with cfcontent. Upload to a static content server If possible upload content to a server other than the application server, a server that only serves static content for example Amazon S3.
Permalink Add Comment add to del. Useful Very Useful Not Useful. This may be a cffule question, but if someone is uploading from a Mac, will it still be able to cdfile from the extension if there isn’t one? I think the browser may be able to send the appropriate mime type if there is ypload file extension I would have to look into that furtherbut remember you can’t trust what the browser sends anyways, it could be spoofed.
Disabling execute permissions on uploads directory is really nice. Great set of tips; I’d also suggest that if you have Apache, watch out for any uploaded files that have multiple file extensions e.
By default, Apache will run the file with the PHP handler even though cffil last extension is something else. I’m revisiting an app that allows customer file uploading, and one approach I’m considering is using CreatUUID to generate a server side file name and stick the customer provided filename in a related database entry going through cfqueryparam, of course.
Thanks for the tips. I’ve been meaning to blog about this myself. Ohly beat me to it. But you also covered quite a lot that I cfflle know, so thank you for that. When I upload files, there are two things I always to before it gets to the action page or code block.
The more people who read about it the better. Great tips, thanks for sharing, Pete.
I’m comforted by the fact that I tend to follow all suggestions you’ve made, with the exception of a static content server. I really do like that idea and intend to leverage Amazon S3 for static content whenever possible in the future. It’s worth noting that you could achieve similar security on your own server, if needed, by leveraging Apache and creating a static content virtual host.
Jamie thanks, yes that is worth noting. I didn’t intend to suggest that S3, or some third party CDN was the only way. Just so I’m clear: If so, placing an Application. Or am I missing something? Sean – They don’t necessarily have to be able to predict it, the application may disclose it in an image tag, or link. Extending the sandbox design: We protect uploads from getting downloaded, without the application running more CFMX code to authorize: OS permissions allow only j2ee to write, any can read.
OS permissions allow only ohly project owner to write, any can read. Now Uploadd code can ohly the backend directory and authorize what the user can see. Meanwhile Apache can’t leak the files on its own. Application code must decide uload to read from those directories, and decide what to send to who. And it’s late, so I’m too tired to clean the grammar.
Tips for Secure File Uploads with ColdFusion
And how to defend yourself and your server and hostingprovider? My Gravatar is enabled via my Hotmail address – any chance you’ll allow those mail-extensions in the future? Sean, You make an excellent point I haven’t thought about. You can effectively disable CF from ever executing from that folder with the right application logic.
Marllon Yes as Jamie mentioned you need to upload the file to a dir outside of the web root and then check the file extension. Otherwise the only way you could do this before calling cffile would cfrile to use a Servlet Filter, or something else that runs before the CFML engine.
I’d cfile like to point out, in response to the first commenter, that Mac OS X files do indeed have file extensions. By default they are hidden to the user but upon sending a file out as up,oad this case they do apply. I just wanted to chime in to remind people that the same goes for emails which attachments that are downloaded by CFpop.
My two faults here are A: Very old app, but Jeeze!
Hi, I’ve seen comments about checking for a double file extensions. Does anybody have any code that would allow me to do this. Does anyone have any suggestions for virus scanning on ColdFusion file uploads? We want to allow trusted sources to upload files to us, but we are worried about files with viruses being accidentally uploaded.
Pete is a husband and father located in scenic Central New York area. Read more about pete here.