The etag was introduced to provide a more flexible mechanism for validating entities than the lastmodified date. This tool performs test against web servers making requests for multiple items. How to determine server banners using netcat, nikto, and. For picture delivery we use our media servers, which are using a dfs in the backend. Every inode has a number which uniquely identifies it. Without a page rule, cloudflare preserves strong etags set by the origin web server if. Nikto is a free and open source web server analysis tool that will perform checks for many of the common vulnerabilities we mentioned at the beginning of this section and discussed earlier in the chapter when we went over server side security issues. Nikto will index all the files and directories it can see on the target web server, a process commonly referred to as spidering, and will then. When a cached response is expired and it has an etag header, it returns a response with the appropriate ifnonematch header.
If for example a component is different based on the useragent or acceptlanguage headers, the state of the entity can be reflected in the etag. Reece fowells blog the home of a lot of crapola nikto server auditing and resolving issues. Scan your web server for vulnerabilities, misconfiguration in free with nikto. Using etag headers with cloudflare cloudflare help center. Nginx doesnt include inodes in etags, only file size and mod time, and apache can be configured to do the same with a fileetag mtime size directive, yet nikto still reports it as leaking inodes. I will say, however, that many of them are incorrect. Apache web server etag header information disclosure weakness solution. Etag is a validator which can be used instead of, or in addition to, the lastmodified header. Novell has released tid10090670 to advise users to apply the available workaround of disabling the directive. Nikto is a free and open source web server analysis tool that will perform checks for many of the common vulnerabilities we mentioned at the beginning of this section and discussed earlier in the chapter when we went over serverside security issues. Here are the headers from a couple of firefox requests for the same file.
The etag header is a unique identifier for a specific version of a document. I store the etag values in application local settings. For busy sites with multiple servers, etags can cause identical resources to not be cached, degrading performance. Nikto is an open source gpl web server scanner which performs. This header makes sure the web servers always sends the correct version of a file. The etag header is used for web cache validation, and enables a web server to not have to send a full response if no changes have been made to the content. Etag is a standard used for determining whether the client web browser already has the latest version of a document. If the client wants to access the same resource again it will send the given string within some ifnonematch header in the. We recently had a scan done on our system and one of the findings was the title of this question. Browser requests can use an etag and an ifmatch header to check whether a resource has been modified since it was served, providing an efficient caching facility that relies on content rather than on timeouts. Information security department of my company found that, 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. Server leaks inodes via etags header found with file. Using mutillidae as the target, this video looks at 3 ways to find web.
But if you found this blog, its probably because you have read some of these articles, as well as a number of blogs and forums on how you can disable iis from sending the etag response. Apache server etag header had an information discloser. How to determine server banners using netcat, nikto, and w3af author. The browser can access it just fine, but when nikto tries it says no web server found on. So, dont remove etag headers unless you are sure your website is not hosted on a highavailability cluster. Go ahead and play around with the nikto software and if interested in. Entitytagheadervalue with get, set public property etag as entitytagheadervalue property value. Nikto web scanner is an another good to have tool for any linux. Pentesting web servers with nikto in backtrack and kali. How to scan for web server vulnerabilities with nikto2 in kali linux. Pentesting web servers with nikto in backtrack and kali linux.
Nikto a web application vulnerability and cgi scanner for web. Os version windows server 2012 r2 standard 9600 domain securelabsondem smb. The lastmodified response header specifies the last time a change was made in the returned content, in the form of a time stamp. Also lastmodified can be understood by the clients, whereas, etag is entirely understood and used on the serverside logic. Alternatively, you can launch a terminal window directly in the nikto directory from the.
Using nikto to better secure servers, and understanding output. More than 1250 outdated version for several web servers. When the app wants to get some data, i perform a get request including the etag as the ifnonematch header. Apache web server etag header information disclosure weakness. The server includes an etag in the response for a resource which represents a unique value for the version of the resource. Server leaks inodes via etags header found with file fields 0x43e55aecf dcf10 from nt 2580 at itt tech. Think of an etag as a unique value that a web server assigns to each cached element.
Configure or eliminate etags chapter 9 advanced web performance optimization. Tomcat does return etag headers with static resources, and does not return the etag with 304 responses. However, if youre nitpicky about the test result, this can be fixed easily. The browser renders the resource and at the same time caches the resource copy along with header information. How to find web server vulnerabilities with nikto scanner geekflare. To reproduce the etag response, use a browser with a proxy owasp zap or other or curl to generate a request for yourdomainrobots. It is used by clients to validate clientcached content to avoid requesting it again. The etag header is used for effective caching of server side resources by the client. Nikto is an open source gpl web server scanner which performs comprehensive tests against web servers for multiple items, including over 6500 potentially dangerous filescgis, checks for outdated versions of over 1250 servers, and version specific problems on over 270 servers. The suggestion to fix the issue is modify the etag header of the web server to not include file inodes in the etag header calculation. That seems wrong according to the quoted part of the spec. Etag values are unique identifiers generated by the server and changed every time the object is modified.
Looking at the code if there is an etag header and it contains a, nikto reports. An inode is a data structure used by the linux file system. To remove the complete etag info then use fileetag none to hide only inode info then use fileetag inode by removing the etag header, you disable caches and browsers from being able to validate files, so they are forced to rely on your cachecontrol and expires header. Nikto reports this issue server leaks inodes via etags if there is a dash in the etag header, which is by itself not an indication of anything. Nikto will index all the files and directories it can see on the target web server, a process commonly referred to as. The response header etag and the request header ifnonematch are used to cache resources on the clients. The server performs a comparison between the etag of the asset and the etag sent by the client, if the etags match then the server will return a 304 not modified header which instructs the browser to use its cached version of the asset. Contribute to sullonikto development by creating an account on github.
Nikto scan for over 6700 items to detect misconfiguration, risky files, etc. How do i use cache control and etag to set headers. Nikto is an open source gpl web server scanner which performs comprehensive tests against web servers for multiple items, including over 6700 potentially dangerous filesprograms, checks for outdated versions of over 1250 servers, and version specific problems on over 270 servers. In lib2, an etag is considered when using a cached response when the cache is considered stale. Hacking with nikto a tutorial for beginners binarytides. This is potentially interesting, but normal and not a. Heres an example apache 3element etag i found using inode, size, mtime.
The origin server specifies the components etag using the etag response header. If they do not match the server will return the asset. How to scan and check a wordpress website security using. Securityfocus is designed to facilitate discussion on computer security related topics, create computer security awareness, and to provide the internets largest and most comprehensive database of computer security knowledge and resources to the public. Default account found for phpmyadmin setup at phpmyadminsetup id, pw 0000. In general, you can ignore this if youre using iis 7 or later as its not affecting much of iis performance tuning. How to make sure that etags are not used to track you on. We would like to use the etag header as caching header instead of expires. This unique value is then compared in consecutive visits by the server to determine whether the cached file needs to be replaced.
Once an etag header is set, subsequent attempts to set it fail and an exception is thrown. Note the first response is a 200 with an etag, the second is a 304 without an etag. Use this code to setup etags on your server, using following htaccess. Nikto always reports etags as leaking inodes, even when they do not. Nikto is an open source scanner written by chris sullo, and you can use with any web servers apache, nginx, ihs, ohs, litespeed, etc. Notice that the etag performs the same service that lastmodified header performs. Apache web server etag header information disclosure sas. Our security team found that apache server etag header information disclosure, we have been asked to remediate, so we are disabling the etag.
Security scan result server leaks inodes via etags information. Server leaks inodes via etags, header found with file, inode. Perform the following command on the server in the appropriate location. Openbsd has released a patch to address this issue. Nikto penetration testing tools kali tools kali linux. Nikto is an open source web server vulnerabilities scanner, it is written. Server includes the header etag with its value in the response. Every file and directory has an inode which stores its name, size and other data. Leveraging etag caching in windows phone and windows apps. Comparing to lastmodifiedheader, using etag is a more generic and efficient way to cache resources. How to find web server vulnerabilities with nikto scanner. Sounds like a perfect inhouse tool for web server scanning. By sending a etag, the server promises that the content is not changed until the etag changes for a specific resource.
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