SQL injection attack

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Transcript SQL injection attack

 SQL Injection is a very old security attack. It first came
into existence in the early 1990's
 ex: ”Hackers” movie hero does SQL Injection to hack
into the database
 SQL injection is still pervasive. One of the security
magzine claimed that more than a million sites are still
vulnerable to SQL Injections
What is SQL Injection Attack?
 Definition: Injecting SQL statements in to the
vulnerable spots with a malicious intention
 It refers to one of the code injection attacks where in
data provided by the user is included in a SQL query
such that part of the user’s input is treated as SQL
 Most of the cyber crimes are pertaining stealing credit
card numbers and stealing money using SQL Injection
in the wake of this decade.
Attack intents
 Extracting data
 Adding or modifying data
 Performing Denial-Of-Service attack
 Bypassing authentication
 Privilege escalation, etc
Injection Mechanisms
 Injection through user inputs
 Injection through cookies
 Injection through server variables
 Second order injection
The query behind such a login
screen will be
WHERE username=‘”+usrname+”’
and password=‘”+pass+”’;
 If the user enters username as x’ or 1=1- - and anything as
 The statement that will be evaluated is,
WHERE username=‘x’ or 1=1 - -’ and password=‘anything’;
This query will be true for each and every tuple of the table
and the attacker will be successful in logging into the
application as administrator (first user in the table).
 Any tautology works
 1 OR 1=1
 1' OR '1'='1
 x' OR greg LIKE '%re%'
 admin' OR 1<4
 admin' OR 4>2
 x' OR 'select' > 's'
 x' OR 'select' < x'
Blind SQL Injection Attack
In this attack cracker/hacker tries to enter wrong
data deliberately to figure out the database
structure and its properties
www.site.com/userid=22 or 1=1 UNION select null,
null, null, null.......
Denial of Service
 If the attacker gives input as
“ ’ ; SHUTDOWN; - -”
The query will be
WHERE username=’ ‘; SHUTDOWN; - -’ and
The database gets shutdown and which will lead to a
DoS attack on the web application.
Evasion Techniques
 White space manipulation
the white spaces can be replaced by tab, carriage
return or line feed, which goes undetected by any
firewall, IDS,etc
 Comment exploitation
 The sql style comment - - is detected by a no of
applications these days, but it can be replaced by C style
comment /**/. Eg UN/*comment*/ION, the sql parsing
engines nowadays strip off all comments before
submitting query for execution, thus evasion can be
 Encoding techniques
 The easiest method of defeating detection
 Most common encodings are
URL encoding
Hex encoding
char() function
Mitigation Techniques
 The root cause of SQL injection vulnerabilities is
insufficient input validation.
 The mitigation can be Defensive coding practices like
 Input type checking
 Encoding of inputs
 Positive pattern matching
 Identification of all input sources
This the best way of preventing SQLIAs but its
application is problematic in practice.
 Use static analysis and also runtime analysis
 Have java script to validate input at the client side
 Thoroughly parse all the statements that are generated
at the runtime using tools like AMNESIA
Demo on a real website
Praveenkumar G Hoolimath
 It is a specification based approach, specifications here
are the different types of queries that the web
application is expected to execute.
 These specifications help to build rules.
 The SQL queries will be intercepted and checked with
these rules.
 The queries violating these rules will be discarded.
Different phases
Phase 1: Definition of specifications (using EBNF)
Phase 2: Interception of SQL statements
Phase 3: Lexical analysis
Phase 4: Syntactical verification of SQL statements
Phase 5: Forwarding valid SQL statements to the
Phase 6: Logging
System Architecture
Specification using EBNF
WHERE userid=‘”+username+”’ and password=‘”+pass+”’;
<Query specification> := SELECT <Select List> <From
Clause> <Where Clause>
<Select List> := <Table Column> (<COMMA> <Table
<From Clause> := FROM <Table reference>
<Where Clause> := WHERE <search condition> AND
<search condition>
<search condition> := <Table Column> "=" <STRING
Salient Features
 It prevents all forms of SQL injection attacks
 Its effectiveness is independent of any particular target
system, application environment, or DBMS
 There is no need to modify the source code of existing
web applications to apply the new protection scheme
to them.
Vasanth Raja
 The solution is based on validation at run time.
 Checks the statement structure before the inclusion of
the user input and after the inclusion of user input.
 This method aims at
 1) Minimizing the effort required by the programmer
 2) Eliminate the possibility of the attack
 3) Minimize the runtime overhead
username=? AND password=?
After including user input
 This method is not disallowing the program from
using tautologies. Eliminating tautologies is not the
 Let the tautology be there in the user input but find
the structure at run time and stop the query to be fed
to database engine
 This method allows the programmer to include the
comments in the SQL statements
Query structure including
comments as tokens
Class structure of the System
Thank you