What is ETag in Apache?

What is ETag in Apache?

ETag is a server response header that allows browsers to make conditional requests and perform cache validation efficiently. On the other hand, it poses security risks in case it gets leaked by your code, and can result in cache poisoning attack on your website.

Should I disable ETag?

Etag and Last-Modified have nothing to do with compression, they are cache’ing options. Which is OK to unset anyway because they conflict with Cache-Control , which is a better cache method. So yes, you may disable it. If you are looking for compression, look into Apache’s mod_deflate , mod_gzip or mod_brotli .

How do I turn off ETag headers?

You might expect you can easily remove Entity tags, or Etag headers , in IIS by using in the customHeaders node of the web. config configuration file. Luckily you can use an IIS URL Rewrite Outbound Rule in Windows Server to rewrite, and remove, the ETags response header.

How do I know if Apache cache is working?

You can check if your apache is really caching content or not by confirming below points.

  1. check size of /var/cache directory. It should be growing in size after some time when there is hit on your apache.
  2. You can check in logs, there should response code 302 instead of 200.

How do I disable Apache cache?

How To Disable Apache Cache

  1. Open . htaccess file. There are many ways to disable Apache cache.
  2. Disable Apache Cache. Let’s say you want to disable caching html, js, css files only, then add the following lines to your .
  3. Restart Apache Server. Restart Apache Server to apply changes $ sudo service apache2 restart.

What is ETag header vulnerability?

Description. The remote web server is affected by an information disclosure vulnerability due to the ETag header providing sensitive information that could aid an attacker, such as the inode number of requested files.

What is the ETag header?

The ETag (or entity tag) HTTP response header is an identifier for a specific version of a resource. It lets caches be more efficient and save bandwidth, as a web server does not need to resend a full response if the content was not changed.

What is ETag inode?

The ETag is an identifier which should uniquely identify a file on the webserver, and the inode number is a number which uniquely identifies a file on the filesystem, so it seemed to make sense to use one for the other.

Is ETag exploitable?

There are no exploits on exploit DB which use the ETag header.

Why can’t I extract the inode number from the ETag header?

This means that the inode number should not be extractable from the ETag header because it should stay secret. This was fixed with Apache 1.3.27 (long ago), i.e. the inode number is still used to compute the ETag but in a way that it cannot be extracted from the ETag value.

What is the value of the header in an ETag?

Often the value of the header is just a hash over the content of the resource which is not a problem at all. But for example the Apache web server can base the ETag on the inode number, last modification time and/or size of the file.

Is there any ETag inode information leakage on IBM HTTP Server?

Our IBM HTTP Server is running with the version Our security scanner revealed that there were some ETag Inode Information Leakage vulnerabilities on our IHS with CVE-2003-1418. I see suggestion to add below line to our http.conf:

How does ETag work in http?

The server send an ETag header in the HTTP response to some string and the client caches the response content and associates the string given in the ETag header with it.