Firstly: I'm a lowly web designer who knows just enough PHP to be dangerous and just enough about server administration to be, well, nothing. I probably won't understand you unless you're very clear!
The setup: I've set up a website where the client uploads files to a specific directory, and those files are made available, through php, for download by users. The files are generally executable files over 50MB. The client does not want them zipped, as they feel their users aren't savvy enough to unzip them. I'm using the php below to force a download dialogue box and hide the directory where the files are located.
It's Linux server, if that makes a difference.
The problem: There is a certain file that becomes corrupt after the user tries to download it. It is an executable file, but when it's clicked on, a blank DOS window opens up. The original file, prior to download opens perfectly. There are several other similar files that go through the same exact download procedure, and all of those work just fine.
Things I've tried: I've tried uploading the file zipped, then unzipping it on the server to make sure it wasn't becoming corrupt during upload, and no luck.
I've also compared the binary code of the original file to the downloaded file that doesn't work, and they're exactly the same (so the php isn't accidentally inserting anything extra into the file).
Could it be an issue with the headers in my downloadFile function? I really am not sure how to troubleshoot this one…
This is the download php, if it's relevant ($filenamereplace is defined elsewhere):
downloadFile("../DIRECTORY/files/$filenamereplace","$filenamereplace");
function downloadFile($file,$filename){
if(file_exists($file)) {
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="'.$filename.'"');
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . filesize($file));
# flush();
readfile($file);
exit;
}
}
ETA Additonal Info:
- Tests for working/non-working files have been done on the same machine
- If it makes any difference, the original file has a custom icon. After download, the file has a generic blank document icon.
Additonal Info: I THINK THIS ONE'S IMPORTANT!
I just tried downloading the file directly (to bypass the download link that triggers the download function above). If I download the file by just going to its url and downloading it that way, the downloaded file WORKS. So I'm thinking it must have something to do with the download function. But what??
3/17 MAJOR CORRECTION —AND RESOLVED—
So I woke up this morning and it dawned on me that maybe I was comparing the files wrong. (I had re-saved them as binary text, and then compared them. I didn't realize the comparison program would take and compare actual exe files). This morning I tried comparing the actual exe files and there is a difference. There was one line of php code that was being injected into the first line of the file. I adjusted the php, and the problem was fixed. (It was from the if/else statement that defined teh $filenamereplace variable in the code I'd cited). Thanks again for all your help, and sorry for misleading you in insisting that the files' contents were identical!
"I've also compared the binary code of the original file to the downloaded file that doesn't work, and their exactly the same (so the php isn't accidentally inserting anything extra into the file)."
If that's really true, then the problem must be in how the exe is started after it has been downloaded. It should certainly not be a problem with your PHP code.
Perhaps they were corrupted on upload. This can happen if you transfer them via FTP in ASCII mode instead of BINARY.
Related
I am really close on this, but I can't quite get this last part to work.
I am trying to set up a web page to compile GBA game code for my students, some of their computers didn't like the compilers so I figured this would be the easiest way to set it up.
I have the compiling all done, and the file it creates works, I pulled it straight from the server to check it, but when it downloads through the browser it isn't working.
$file_url = 'directory/main.gba';
if(file_exists($file_url)){
header('Content-Type: application/download');
header("Content-Transfer-Encoding: Binary");
header('Content-Disposition: attachment; filename="'.basename($file_url).'"');
readfile($file_url);
}
I am not a PHP coder so I don't really know where to go from here, any advice would be appreciated!
PS: I did a diff on the files as well to confirm they are different
Edit: Just tested to see if it was actually seeing the file, when I changed it to a non-existent directory it did not download anything, so it is definitely seeing the file and trying to download it, but something is wrong with the file once it finishing downloading
Edit 2: Seen in comment: I used a hex editor to look at the broken file and it had the text that I echoed prepended to it. Is there a way I can avoid this?
I am currently stugling to understand just what is wrong with my app.
As I was unable to find a solution (more about that here: Codeigniter Download Helper corrupts .7z and .rar files help or alternative solutions?) I decided to take a different approach.
So the question is what causes downloaded files via the HTML request (if I said that right) to become corrupt even when they are not corrupted when downloaded via FTP. And a follow up is, what causes a specific type of extension to become corrupt. Since I can download zip files fine but 7z and rar files get corrupted.
This is the header list that codeiniter's download helper uses:
header('Content-Type: "'.$mime.'"');
header('Content-Disposition: attachment; filename="'.$filename.'"');
header("Content-Transfer-Encoding: binary");
header('Expires: 0');
header('Pragma: no-cache');
header("Content-Length: ".strlen($data));
The helper uses file_get_contents() in order to determine content-length and send. I tried to use filesize() and to send a file via readfile() but the result was the same.
I also tried different mimes, from the all inclusive application/octet-stream to the spefic ones depending on the type (application/x-7z-compressed etc) but it had little effect.
So at this point I have no idea what causes some extensions to work while others do not.
Any suggestion is welcome.
Is there some php, or apache or any tweak, property I can use to change this?
EDIT:
I noticed that for some reason when I open a file there is a added number that represents an ID of the download i have no idea how it got here or how to stop it, but this have put me on the right track. Thanks so very much, i will update this one as I progress.
Also how to prevent php to append something on top of my file?
EDIT:
FOUND IT!
It was an obscure echo that I simply didn't see, I was just so tired. But now that it is gone everything works fine. I've spend around hours truing to find out what was wrong, I am pissed of at myself, but right now I am glat it is over. Thanks so very much helping me find the problem :)
I have a htaccess password protected folder with several files in it. Users are not allowed to access all files, but are allowed to download their own.
Since i can't direct link the file and since copying / removing isn't a real solution, i thought i'd just open the file using file_get_contents and echo it back into the page using the right header. But.. i don't get it working.. Here is my code. The error i am getting is that when opening the file i get a "file is damaged" error from Acrobat.
<?php
$file = "cms/docs/5641-1.pdf";
header('Content-Description: File Transfer');
header('Content-type: application/pdf');
header('Content-Disposition: attachment; filename='.basename("exoticfilename.pdf"));
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . filesize($file));
if (file_exists($file))
{
echo file_get_contents($file);
}
?>
Also, in this example I am just using a PDF file, but there are several types of files. Therefore i should probably change the header depending on the file type. Is there a solution for that, or should i just use a very long if / else statement?
If there is another, better way, I am open for that.
UPDATE
The above works, but not with all files. Older PDF's (Acrobat 6) don't work, but Acrobat X files do. Same counts for the docx files. Some work, others don't. Very weird, since I am able to open all directly on my PC. I assume it has something to do with the application/pdf line (or application/vnd.openxmlformats-officedocument.wordprocessingml.document' for docx). All others, like images, work.
Since you are using htaccess/htpasswd to protect the directory from hot-linking leeches. You are inadvertanly blocking access to the files from an outside source such as a browser from the client side. Since the directory requires authentication to access the files within it, you need to script around it. In a sense authenticating through the script. I have seen it done before, and you can find one of many references on the subject here
http://koivi.com/php-http-auth/
but bottom line is htaccess and htpasswd over run your scripts even if on the same host machine, as they are in a lack of better description server level, ran before even php starts its process on a page load.
I'm developing a web service. With this service, user's will upload their .php files, and service will remove UTF8 BOM characters from php file. And then, There will be a link like this :
Download Your File
But when i click this link, browser browsing to this file. I don't want browse it, i want to download it. So , when user click this link, downloading will start.
Any ideas ?
(P.S. I don't want modify uploadedfile.php file, also i read 5 questions about this, but still i have problem.)
You need to supply this HTTP header:
Content-Disposition: attachment; filename=example.txt
You can usually specify this for entire directories at a time by configuring your web server appropriately. If you mention which web server you are using, somebody may be able to suggest how to do this.
The problem is that you're allowing people to upload PHP files on your server, then giving them a link to execute that PHP file. The web server is automatically treating those uploaded PHP files like any other PHP file, i.e. executing it, which opens you up to a massive security hole.
Whatever purpose your web service has, I'd suggest renaming the file on your server when it is uploaded (something 'random' is best, without an extension), then having a PHP script feed it back out with the appropriate headers set when it is requested.
The URL for such a script would look like:
http://www.example.com/get_uploaded_file.php?id=jgh3h8gjdj2389
It would link the value in id with the file on the server, and if you've saved the original filename somewhere (flat file, DB), you can serve it out using its original name, so long as you set the right HTTP headers.
Linking directly to the PHP file may end up executing it. One way is (like somebody above suggested) to rename it. Or, you can have a downloader.php which does below:
<?php
header('Cache-Control: no-cache, must-revalidate');
header('Expires: Mon, 01 Jan 2000 01:00:00 GMT'); // some date in past
header('Content-type: text/plain');
header('Content-Disposition: attachment; filename='.basename($filepath));
header('Content-Length: ' . filesize($filepath));
flush(); // or any other flush function/mechanism you use.
readfile($filepath);
and link it something like:
Download
This method will let you retain the .php extension. Also, if the PHP file is big and connection is slow, they progress-bar would be accurate (because you've flushed the content length upfront.
I have a php file that acts as a gatekeeper for all the files I want people to download, who ahve sufficient privilages.
The code I use throw the file to the user is
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header("Content-disposition: attachment; filename=\"".$public_filename."\"");
header("Content-Transfer-Encoding: Binary");
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header("Content-length: ".$f_filesize);
readfile($file_path);
Most files are fairly large.... 400mb-10GB.
What would be a good way to do this, and keep the true locations + filenames secret, so people cant just link to the files directly, but HAVE to link thru my download.php?file=ID gatekeeper?
Thanks
EDIT: Im not asking how to do user authentication, all that is done. Im just asking if my way of doing it, is a good idea on a large scale. Seems like it could cause memory problems if I keep reading 10GB files.
Ok, having php send files of around 400Mb–10Gb is not good. You need to somehow let whatever webserver you're using actually serve the files.
This really comes down to how secure you need it to be. The easiest solution that comes to mind (but far from the most secure) is using symbolic links with long random names that link to the original file. After a certain time the symbolic links expire and are removed. Each user get their own symbolic link (or "token") to the file they're downloading. I'm not sure how this plays out in Windows-environment, but on unix it's fairly straightforward anyway.
Here's some pseudo code:
if($user->isAllowedToDownload($file)){
$token = md5($user->name . $file->name . time() . $someGoodRandomValue);
symlink($file, $download_path . $token);
header("Location: $download_url$token");
}
Then you need a cron job that cleans out old symbolic links. You also need to make sure the webserver is set to follow symbolic links, preferably only for that folder where these download tokens are created.
So when the user maybe requests domain.com/download?file=bigfile.mp4 a symbolic link is created in the webservers public space that points to the real file outside the webservers public space. The user gets redirected to maybe domain.com/getFile/ab739babec890103bdbca72 which in turn causes the webserver to serve the file. Now it's very hard for users to try and guess what an URL is for a file, and that's the "security".
You're already doing that - the $public_filename is what you want it called, the readfile($file_path) part is the file - it's location isn't made public. Past that, it could be above the document root.
Put the files somewhere that is not accessible via HTTP.
Create a database table of file IDs with file paths.
Link to the files via file ID (as you noted above, download.php?fileID=0000).
???
Profit.
As someone who did this previously (many years ago), you need to consider the memory impact this will have on your server. The readfile function was not available then, so it is possible you may not need to do anything special for memory considerations.
You'll want to somehow authenticate them (an HTML form, HTTP basic auth, whatever), then set a session flag, which your download.php script can check. Note that this doesn't prevent people from downloading the file, then distributing it themselves.
You should configure your web server so the real files are not directly accessible.
It's not going to cause memory problems per se. readfile does not read the file into memory. However, using PHP will create overhead. You can eliminate some of this delay by using X-Sendfile.
Your method will cause memory problems, however it is possible to read and output the file in chunks. You will need to use flush() function after you echo each chunk of file. You can also make resuming downloads to work with a little more effort. Still this is an CPU hungry approach.
The easier and better solution is to use "x-sendfile" header tag supported by both apache and lighttpd through their modules. All you'll have to do is just specify file name in your header, similar to this:
header('X-Sendfile: filename-on-your-file-system');
Link for lighttpd:
http://redmine.lighttpd.net/projects/lighttpd/wiki/X-LIGHTTPD-send-file