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| − | Web exploitation is the attacking and taking advantage of a [[vulnerability]] in a computer system through a [[web application]]. There are numerous ways to exploit [[vulnerability|vulnerabilities]] so only some of the basics will be covered here. Any of the topics covered below by themselves can be dangerous enough to cripple an entire server or website, gaining enough access to even remotely take over daemons and services enough to "spawn a shell," or gain enough access to gain system or root level access.
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| − | ====Escape Strings====
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| − | Null [[Byte|bytes]], escape strings, and [[SQL injection]] all work the same way. When a computer sees a combination of characters as user [[input]], it is called a string. In many languages strings are truncated by null [[Byte|bytes]], or by other escape sequences. In other words, if the computer sees a null [[byte|Byte]] in a combination of user [[input]], the computer assumes that the null [[byte|Byte]] is the end of the [[input]], allowing an attacker to inject malicious code into the space between the real end of the [[input]] and what the computer believes to be the end of the [[input]]. So for example, sometimes null [[[Byte|bytes]] are used to perform directory transversal. IIS web servers hold all of their information for their web serving in C:\InetPub; however the attacker wants to see just the C drive. As a result, the attacker requests:
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| − | /%00../
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| − | ====Directory Transversal & Null Bytes====
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| − | The “%00” is a null [[byte|Byte]]. The string of characters "../" is a request for a higher level directory. Ordinarily, the [[HTTP]] server would never show you the higher level directory, however because it doesn't realize that the higher level directory was asked for, the attacker is able to look at a higher level directory. The web server only sees the domain because the %00 blinds it to the %00 and everything after it, however when it processes the request to retrieve the file, the request is to view “../”, which is the higher level directory.
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| − | ====Other Escape Strings====
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| − | A null [[byte|Byte]] is a small example of an "escape string". An escape string is any character or combination thereof that a program will recognize as the end of user [[input]]. For example, the escape string used in [[SQL injection]] is usually an apostrophe ('), or %27, which is the bytecode representation of an apostrophe. Remote [[SQL injection]] vulnerabilities affect [[Database|databases]]. [[SQL]] is widely used by things like shopping carts, forums, dynamic web sites like MySpace, deviantart, facebook, and the like, as well as banks, credit unions, and other financial institutions. When [[SQL injection]] can be successfully exploited it is a critical [[vulnerability]] in the affected site and should be [[patched]] immediately, because it may lead to compromise or loss of customer data, employee data, financial data, or anything else stored in the [[SQL]] [[database]]. [[SQL injection]] has two attack vectors, one in a URL, the other in a web based form.
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| − | When penetration testing a site, it is different than penetration testing a network, and different than penetration testing a server. However, it is good to point out, that by compromising the [[web applications|web application]] layer sometimes the server can be compromised, and sometimes by compromising the server, the web application layer can be compromised.
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| − | ====Web Applications====
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| − | Another few steps back. Many web sites run [[web applications]] for the purpose of dynamic content. Usually this would include an [[SQL]] [[database]] backend of some sort, and web [[applications]] (like forums, talkboards, content management systems, and blogs) are generally written in (but not limited to) [[PHP]], [[python]], [[perl]], [[ASP]], [[ASPX (.NET 2.0+)]], [[ruby]], or other form of [[CGI]]. Other web exploitation includes [[XSS]], [[CSRF]], and [[file inclusion]].
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| − | ====Tools====
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| − | *Nikto
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| − | *Wikto
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| − | *Absinthe
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| − | [[Category:Attacks]]
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