Download - SQL Injections Seminar Report

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Seminar on Information Technology Acts

A report on

‘SQL INJECTION’

Submitted In

Partial Fulfillment of

Bachelor of Technology Degree

In Computer Science & Engineering

Academic Session 2013-14

Supervisor Submitted By Mr. S. R. Dogiwal Prateek Chuahan

Reader Roll No: 10ESKCS738

Department of Computer Science & Engineering VIII Sem CS-II

Department of Computer Science & Engineering

Swami Keshvanand Institute of Technology, Management & Gramothan,

Jaipur

Rajasthan Technical University, Kota

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Candidate’s Declaration

I hereby declare that the work, which is being presented in the

dissertation, entitled “SQL INJECTION” in partial fulfillment for the award of

the Degree of Bachelor of Technology in Department of Computer Science and

Engineering submitted to Swami Keshvanand Institute of Technology,

Management and Gramothan, Jaipur, Rajasthan Technical University,

Kota is a record of my own investigations carried under the guidance of Mr.

S.R. Dogiwal (Reader), Department of Information Technology, Swami

Keshvanand Institute of Technology, Management and Gramothan, Jaipur.

I have not submitted the matter presented in this report elsewhere for the

award of any other Degree.

……………….

(Prateek Chauhan)

B.Tech (Computer Science)

Roll No.: 10ESKCS738

Swami Keshvanand Institute of Technology, Management and Gramothan, Jaipur

Counter Signed by

…………………

(Mr. S.R. DOGIWAL)

Reader, Department of information Technology Swami Keshvanand Institute of Technology, Management and Gramothan, Jaipur

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ACKNOWLEDGEMENT

I take this opportunity to express my gratitude to the people who have been

instrumental in the successful completion of this dissertation.

I would like to express my unbound gratitude to my guide Mr. S.R.

Dogiwal, Reader, Swami Keshvanand Institute of Technology,

Management and Gramothan, Jaipur for his guidance and help throughout

my dissertation.

I am greatly indebted to respected Dr. C.M. Choudhary, HOD, Computer

Science Department, Swami Keshvanand Institute of Technology,

Management and Gramothan, Jaipur for his motivation and guidance in

completing my dissertation successfully.

I am extremely thankful to respected Dr. S.L. Surana, Director Academics,

Swami Keshvanand Institute of Technology, Management and Gramothan,

Jaipur, for providing necessary facilities throughout this dissertation.

I am greatly indebted to all faculties of Swami Keshvanand Institute of

Technology, Management and Gramothan, Jaipur, for their scholarly

guidance, precious advice, direct supervision and constant encouragement for

carrying out this work successfully.

Prateek Chauhan

B. Tech. (Computer Science & Engineering)

Roll No: 10ESKCS738

Swami Keshvanand Institute of Technology, Management & Gramothan, Jaipur

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CONTENTS

S_NO. NAME PAGE_

NO.

(I) COVER PAGE 1

(II) CANDIDATE’S DECLARATION 2

(III) ACKNOWLEDGEMENT 3

(IV) CONTENTS 4

(V) ABBREVIATIONS & ACRONYMS 6

(VI) LIST OF TABLES 6

(VII) LIST OF IMAGES 6

(VIII) ABSTRACT 7

1. SQL INJECTION 8

1.1 INTRODUCTION 8

1.2 What Is Sql Injection? 9

1.3 Who’s Vulnerable? 10

1.4 Who’s Not Vulnerable? 10

2. WORKING 11

2.1 Working Of Sql Injection 11

3. TYPES OF ATTACKS 16

3.1 TYPES OF SQL INJECTION ATTACKS 16

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3.1.1 First Order Attacks 16

3.1.2 Second Order Attacks 17

4 METHODS OF INJECTION 18

4.1 METHODS OF SQL INJECTION 18

4.1.1 Normal Sql Injection 18

4.1.2 Blind Sql Injection 19

5 CATEGORIES 20

5.1 CATEGORIES OF SQL INJECTION ATTACKS 20

5.1.1 Sql Manipulation 20

5.1.2 Code Injection 21

5.1.3 Function Call Injection 22

5.1.4 Buffer Overflows 24

6. DETECTION OF VULNERABILITY 25

7. PREVENTING SQL INJECTION ATTACKS 27

8. SCREENSHOTS OF SAMPLE APPLICATION 30

9. CONCLUSION 32

10. REFRENCES 33

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ABBREVIATIONS AND ACRONYMS

SQL: Structured Query Language

DB: Database

ODBC: Open Database Connectivity

JSP: Java Server Pages

ASP: Active Server Pages

PHP: Hypertext Pre Processor

Tz_offset: Time Zone Offset

To_timestamp_tz: timestamp to timezone

Bfilename, from_tz: from timezone to binary file

Numtoyminterval: number to year-month interval

Numtodsinterval: number to date seconds interval

LIST OF TABLES S_NO. TABLE_NO. TABLE_NAME PAGE

1. Table 1 Vulnerable characters

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LIST OF IMAGES

S_NO. IMAGE_NO. IMAGE_NAME PAGE

1. Fig 1 Vulnerability 10

2. Fig 2 Injecting SQL 11

3. Fig 3 Login Page 30

4. Fig 4 User’s home page 30

5. Fig 5 Injecting SQL 31

6. Fig 6 Unauthorized

access of data

31

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ABSTRACT

This report contains information about an extremely popular database attack.

Most of today’s web applications require dynamic content and input from users

to achieve the same appeal as traditional applications within the desktop

operating system.

This is achieved by using languages such as SQL, the most common being

MySQL. The attacker can gain unauthorized access to restricted data such as

usernames/ passwords/ email addresses etc.

Using SQL injections, attackers can add new data to the database. With some

more advanced queries and tricky techniques the attacker can:

Potentially bypass the authentication

Gain complete control over the web application and potentially the web

server.

Perform an INSERT in the injected SQL.

Modify data currently in the database.

Perform an UPDATE in the injected SQL.

Other can gain access to other user’s system capabilities by obtaining

their password.

Not only is it a threat easily instigated, it is also a threat that, with a little

common-sense and forethought can be almost totally prevented. This report will

look at a selection of the methods available to a SQL injection attacker and how

they are best defended against.

Keywords: sql injections, privacy issues, security issues.

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SQL INJECTION

1.1 Introduction

The World Wide Web has experienced remarkable growth in recent years.

Businesses, individuals, and governments have found that web applications can

offer effective, efficient and reliable solutions to the challenges of

communicating and conducting commerce in the Twenty-first century.

However, the security of Web applications has become increasingly important

in the last decade. With more and more Web-based applications deal with

sensitive financial and medical data, it is crucial to protect these applications

from hacker attacks. A security assessment by the Application Defence Centre,

which included more than 250 Web applications from e-commerce, online

banking, enterprise collaboration, and supply chain management sites,

concluded that at least 92% of Web applications are vulnerable to some form of

attack.

Much vulnerability in web applications is caused by permitting unchecked input

to take control of the application, which an attacker will turn to unexpected

purposes. SQL Injection is the most common type of technique used.

Beside SQL Injection the other type of attacks are:

· Shell injection.

· Scripting language injection.

· File inclusion.

· XML injection.

· SQL Injection

· XPath injection.

· LDAP injection.

· SMTP injection.

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1.2 What is SQL Injection?

SQL Injection is a technique to hack the database. It is a type of security exploit

in which the attacker adds a SQL code to a Web form input box to gain access

to resources or make changes to data.

Most of the time existing queries are edited to achieve the same results.

Transact SQL is easily changed by the placement of a single character in a

chosen spot causing the query to behave in malicious ways. The most

commonly used characters are back tick (`), double dash (--) and the semicolon

all of which have specified meaning in SQL.

A user of our form enters a piece of SQL code into it, and wraps it in special

characters in such a way that the data entered doesn't get used for the purpose

we had intended, instead it gets used to corrupt or destroy our database.

When attacker enters the data into the form, that data is directly used to build a

dynamic SQL query to retrieve the data from database. Such malicious code

injection is called as an SQL Injection attack.

The attacker is then free to extract, modify, add or delete content from the

database. In some circumstances, the attacker may even penetrate past the

database server and into the underlying operating system..

There are two forms of SQL Injection attacks:

1. Form Injection

2. URL Injection

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1.3 Who’s vulnerable?

A web application is vulnerable to SQL injection for only one reason – end user

string input is not properly validated and is passed to a dynamic SQL statement.

The string input is usually passed directly to the SQL statement. However, the

user input may be stored in the database and later passed to a dynamic SQL

statement. Because of the stateless nature of many web applications, it is

common to write data to the database between web pages. This indirect type of

attack is much more complex and requires in depth knowledge of the

application.

1.4 Who’s not vulnerable?

SQL Statements using bind variables are generally immune to SQL Injection

attacks as the Oracle database will use the value of the bind variable exclusively

and not interpret the contents of the variable in any way. PL/SQL and JDBC

allow for bind variables. Bind variables should be extensively used for both

security and performance reasons.

VULNERABILITY

What’s Vulnerable?

• MySQL

• SQL Server

• PostgreSQL

• HBase

• IBM DB2

• Apache Derby

• RBase

• ANY DBMS using SQL

What’s not Vulnerable?

• ORACLE

Figure 1. VULNERABILITY

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WORKING

2.1 Working of SQL Injection

The principles behind a SQL injection are simple and these types of attacks are

easy to execute and master. To exploit a SQL injection flaw, the attacker must

find a parameter that the web application passes through to a database. By

carefully embedding malicious SQL commands into the content of the

parameter, the attacker can trick the web application into forwarding a

malicious query to the database.

For example, consider the login form which accepts the username and password

from the user.

Figure 2. Injecting SQL

The values supplied in the field “Username” and “Password” are directly used

to build the SQL Query like:

SELECT * FROM customers

WHERE name = ‘ & name & ’ AND password = ‘ & password’

Now, Suppose the user supplied the Username =”Admin” and Password =

‘Magic’

The query will become:


WHERE name = ‘Admin’ AND password = ‘magic’

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This will work with no problem. But suppose the user supplied some poorly

devised string of code then that will allow the attacker to by-pass the

authentication and access the information from the database. i.e., if user

supplied username=’ OR 1=1— then the query will be passed as:


WHERE name = ‘’ OR 1=1--’ AND password = ‘ ’;

It Works as follows:

‘: Closes the user input field.

OR: Continues the SQL query so that the process should equal to what comes

before OR what comes after.

1=1: A statement which is always true.

--: Comments outs the rest of the lines so that it won’t be processed.

The data we're filling is used by the WHERE clause. And because the

application is not really thinking about the query - merely constructing a string -

our use of OR has turned a single-component WHERE clause into a two-

component one and the 1=1 clause are guaranteed to be true no matter what the

first clause is. The query means that:

“Select everything from the table customers if the name equals “nothing” Or

1=1. Ignore anything that follows on this line.

Seeing as 1 will always equal 1, the server has received a true statement and is

fooled into allowing an attacker more access than they should have. The code

that refers to the password input field is never run by the server and therefore

does not apply.

2.2 Some more examples:

Example 1: Getting a column name from database error message.

Consider the a login form supplied with following arguments:

Username: ' having 1=1 ---

Password: [Anything]

When the user clicks on the submit button to start the login process, the SQL

query causes ASP to spit the following error to the browser:

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“Microsoft OLE DB Provider for SQL Server (0x80040E14)

Column 'users.userName' is invalid in the select list because it is not

contained in an aggregate function and there is no GROUP BY clause.

/login.asp, line 16”

This error message now tells the unauthorized users the name of one field from

the database that application is trying to validate the login credentials against:

users.username. Using the name of this field, attacker can now use SQL Server's

LIKE clause to login with the following credentials:

Username: ' OR users.userName LIKE 'a%' --


This performs an injected SQL query against our users table:

SELECT userName

FROM users

WHERE userName='' OR users.userName LIKE 'a%' --' and userPass=''

The query grabs the userName field of the first row whose userName field starts

with ‘a’.

Example 2: Creating a new username and password.

To create a new user record, the attacker must have the information about the

table name and column names it that table. For that the user might use the

following technique. First the user supplies an input at username field like:

Username: ' having 1=1--

This provokes the following error:

Microsoft OLE DB Provider for ODBC Drivers error '80040e14'

[Microsoft][ODBC SQL Server Driver][SQL Server]Column 'users.id' is

invalid in the select list because it is not contained in an aggregate

function and there is no GROUP BY clause.

/process_login.asp, line 35

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So the attacker now knows the table name and column name of the first column

in the query. They can continue through the columns by introducing each field

into a 'group by' clause, as follows:

Username: ' group by users.id having 1=1--

The above input generates the following error:


[Microsoft][ODBC SQL Server Driver][SQL Server]Column

'users.username' is invalid in the select list because it is not contained in

either an aggregate function or the GROUP BY clause.


Eventually the attacker arrives at the following Username:

' group by users.id, users.username, users.password, users.privs having 1=1—

which produces no error, and is functionally equivalent to:

select * from users where username = ''

So the attacker now knows that the query is referencing only the 'users' table,

and is using the columns 'id, username, password, privates', in that order.

It would be useful if he could determine the types of each column. This can be

achieved using a 'type conversion' error message, like this:

Username: ' union select sum(username) from users--

This takes advantage of the fact that SQL server attempts to apply the 'sum'

clause before determining whether the number of fields in the two row sets is

equal. Attempting to calculate the 'sum' of a textual field results in this message:


[Microsoft][ODBC SQL Server Driver][SQL Server]The sum or

averageaggregate operation cannot take a varchar data type as an

argument. /process_login.asp, line 35

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which tells us that the 'username' field has type 'varchar'. If, on the other hand,

we attempt to calculate the sum () of a numeric type, we get an error message

telling us that the number of fields in the two row sets don't match:

Username: ' union select sum(id) from users--


[Microsoft][ODBC SQL Server Driver][SQL Server]All queries in an SQL

statement containing a UNION operator must have an equal number of

expressions in their target lists.


We can use this technique to approximately determine the type of any column

of any table in the database.

This allows the attacker to create a well - formed 'insert' query, like this:

Username: '; insert into users values( 666, 'attacker', 'foobar', 0xffff )--

Example 3: Dropping a table from database.

Several databases use semicolon (;) to delimit a query. The use of a semi-colon

allows multiple queries to be submitted as one batch and executed sequentially.

The attacker might use this to inject the database. For example,

Username: ' OR 1=1; DROP TABLE users; --


Then the query would execute in two parts. Firstly, it would select the

userName field for all rows in the users table. Secondly, it would delete the

users table, so that when we went to login next time, we would see the

following error:

Microsoft OLE DB Provider for SQL Server (0x80040E37)

Invalid object name 'users'.

/login.asp, line 16

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TYPES OF ATTACKS

3.1 Types of SQL Injection attacks

The SQL Injection attacks are basically divided into 2 types:

1. First Order attacks

2. Second Order attacks

3.1.1 First Order attacks

First order attacks are those attacks when the attacker receives the desired result

immediately, either by direct response from the application they are interacting

with or through some other response mechanism, such as e-mail.

For example, suppose a form ask the email id of the user. If the user provided

the correct email id with no extra code then the query will run properly. But

suppose if the user enter a “LIKE” clause with the email id then the database

will return the matching criteria to the user immediately.

SELECT email, passed, login_id, full_name

FROM members

WHERE email=’ x’ OR full_name LIKE ‘%Bob%’;

Here, the database will return information of any user where the name starts

with “Bob”.

As, the attacker is getting the result immediately, this type of attacks are called

first order attacks.

3.1.2 Second Order attacks

A Second order attack can be classified as the process in which the malicious

code is injected into a web-based application and not immediately executed, but

is stored by application (e.g. temporarily cached, logged, stored in database) and

then later retrieved, rendered or executed by the victim.

This type of attacks often occurs because once data is in the database; it is often

thought of as being clean and is not checked again. However, the data is

frequently used in queries where it can still cause harm.

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Consider an application that permits the users to set up some favourite search

criteria.

When the user defines the search parameters, the application escapes out all the

apostrophes so that a first-order attack cannot occur when the data for the

favourite is inserted into the database. However, when the user comes to

perform the search, the data is taken from the database and used to form a

second query which then performs the actual search. It is this second query

which is the victim of the attack.

For example, if the user types the following as the search criteria:

'; DELETE Orders;--

The application takes this input and escapes out apostrophe so that the final

SQL statement might look like this:

INSERT INTO favourites (UserID, FriendlyName, Criteria)

VALUES(123, 'My Attack', ''';DELETE Orders;--')

which is entered into the database without problems. However, when the user

selects their favourite search, the data is retrieved to the application, which

forms a new SQL command and executes that.

The second query to the database, when fully expanded, now looks like this:

SELECT * FROM Products

WHERE ProductName = ''; DELETE Orders;--

It will return no results for the expected query, but the company has just lost all

of their orders. These types of attacks are known as second order attacks.

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METHODS OF INJECTION

4.1 Methods of SQL Injection

There are two methods for attacking through SQL Injection. They are

1. Normal SQL Injection

2. Blind SQL Injection

4.1.1 Normal SQL Injection

In this type of attacks, when an attacker tries to execute SQL Query, sometimes

the server returns an error page to the user which describes the type and cause

of the error in detail.

Thus, the attacker can try to match his query with the developers query by using

the information contained in the error messages returned in response by the

database server.

By appending a union select statement to the parameter, the attacker can test to

see if he can gain access to the database: For example,

http://example/article.asp?ID=2+union+all+select+name+from+sysobjects

The SQL server then may return the database error similar to this:


[Microsoft] [ODBC SQL Server Driver] [SQL Server] All queries in the

SQL statement containing a UNION operator must have an equal number of

expressions in their target lists.

This tells the attacker that he must now guess the correct number of columns for

his SQL statement to work.

4.1.2 Blind SQL Injection

Blind SQL injection is identical to normal SQL Injection except that when an

attacker attempts to exploit an application, rather than getting a useful error

message, they get a generic page specified by the developer instead. This makes

exploiting a potential SQL Injection attack more difficult but not impossible. An

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attacker can still steal data by asking a series of True and False questions

through SQL statements.

Detecting Blind SQL Injection

Executing the following request to a web site:

http://example/article.asp?ID=2+and+1=1

Should return the same web page as:

http://example/article.asp?ID=2

because the SQL statement 'and 1=1' is always true.

Executing the following request to a web site:

http://example/article.asp?ID=2+and+1=0

would then cause the web site to return a friendly error or no page at all. This is

because the SQL statement "and 1=0" is always false.

Once the attacker discovers that a site is susceptible to Blind SQL Injection, he

can exploit this vulnerability more easily, in some cases, than by using normal

SQL Injection.

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CATEGORIES

5.1 Categories of SQL Injection Attacks

There are four main categories of SQL Injection attacks against databases. They

are:

1. SQL Manipulation

2. Code Injection

3. Function Call Injection

4. Buffer Overflows

5.1.1 SQL Manipulation

The most common type of SQL Injection attack is SQL manipulation. The

attacker attempts to modify the existing SQL statement by adding elements to

the WHERE clause or extending the SQL statement with set operators like

UNION, INTERSECT, or MINUS. There are other possible variations, but

these are the most significant examples.

The classic SQL manipulation is during the login authentication. A simplistic

web application may check user authentication by executing the following

query and checking to see if any rows were returned –

SELECT * FROM users

WHERE username = 'bob'

And PASSWORD = 'mypassword'

The attacker attempts to manipulate the SQL statement to execute as:

SELECT * FROM users


AND Password = 'mypassword' or 'a' = 'a'—

Based on operator precedence, the WHERE clause is true for every row and the

attacker has gained access to the application.

The set operator UNION is frequently used in SQL injection attacks. The goal is

to manipulate a SQL statement into returning rows from another table. A web

form may execute the following query to return a list of available products:

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SELECT product_name

FROM all_products

WHERE product_name like '%Chairs%'

The attacker attempts to manipulate the SQL statement to execute as:

SELECT product_name FROM all_products

WHERE product_name like '%Chairs'

UNION

SELECT username FROM dba_users

WHERE username like '%';

The list returned to the web form will include all the selected products, but also

all the database users in the application.

5.1.2 Code Injection

Code injection attacks attempt to add additional SQL statements or commands

to the existing SQL statement. This type of attack is frequently used against

Microsoft SQL Server applications, but seldom works with an Oracle database.

The EXECUTE statement in SQL Server is a frequent target of SQL injection

attacks – there is no corresponding statement in Oracle.

In PL/SQL and Java, Oracle does not support multiple SQL statements per

database request.

Thus, the following common injection attack will not work against an Oracle

database via a PL/SQL or Java application. This statement will result in an

error:

SELECT *

FROM users


AND Password = 'mypassword';

DELETE FROM users

WHERE username = 'admin';

However, some programming languages or APIs may allow for multiple SQL

statements to be executed.

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PL/SQL and Java applications can dynamically execute anonymous PL/SQL

blocks, which are vulnerable to code injection. The following is an example of a

PL/SQL block executed in a web application –

BEGIN ENCRYPT_PASSWORD('bob', 'mypassword'); END;

The above example PL/SQL block executes an application stored procedure that

encrypts and saves the user’s password. An attacker will attempt to manipulate

the PL/SQL block to execute as –

BEGIN ENCRYPT_PASSWORD('bob', 'mypassword');

DELETE FROM users

WHERE upper(username) = upper('admin'); END;

5.1.3 Function Call Injection

Function call injection is the insertion of Oracle database functions or custom

functions into a vulnerable SQL statement. These function calls can be used to

make operating system calls or manipulate data in the database.

The Oracle database allows functions or functions in packages to be executed as

part of a SQL statement. By default, Oracle supplies over 1,000 functions in

about 175 standard database packages, although only a few of these functions

may be useful in a SQL injection attack. Some of these functions do perform

network activities which can be exploited. Any custom function or function

residing in a custom package can also be executed in a SQL statement.

Functions executed as part of a SQL SELECT statement cannot make any

changes to the database unless the function is marked as “PRAGMA

TRANSACTION”.

None of the standard Oracle functions are executed as autonomous transactions.

Functions executed in INSERT, UPDATE, or DELETE statements are able to

modify data in the database.

Using the standard Oracle functions, an attacker can send information from the

database to a remote computer or execute other attacks from the database server.

Many native Oracle applications leverage database packages which can be

exploited by an attacker.

These custom packages may include functions to change passwords or perform

other sensitive application transactions.

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The issue with function call injection is that any dynamically generated SQL

statement is vulnerable. Even the simplest SQL statements can be effectively

exploited.

The following example demonstrates even the most simple of SQL statements

can be vulnerable. Application developers will sometimes use database

functions instead of native code (e.g., Java) to perform common tasks. There is

no direct equivalent of the TRANSLATE database function in Java, so the

programmer decided to use a SQL statement.

SELECT TRANSLATE('user input',

'0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ',

'0123456789')

FROM dual;

This SQL statement is not vulnerable to other types of injection attacks, but is

easily manipulated through a function injection attack. The attacker attempts to

manipulate the SQL statement to execute as:

SELECT TRANSLATE('' || UTL_HTTP.REQUEST('http://192.168.1.1/') || '',


'0123456789')

FROM dual;

The changed SQL statement will request a page from a web server. The attacker

could manipulate the string and URL to include other functions in order to

retrieve useful information from the database server and send it to the web

server in the URL. Since the Oracle database server is most likely behind a

firewall, it could also be used to attack other servers on the internal network.

Custom functions and functions in custom packages can also be executed. An

example would be a custom application has the function ADDUSER in the

custom package MYAPPADMIN. The developer marked the function as

“PRAGMA TRANSACTION”, so it could be executed under any special

circumstances that the application might encounter. Since it is marked

“PRAGMA TRANSACTION”, it can write to the database even in a SELECT

statement.

SELECT TRANSLATE('' || myappadmin.adduser('admin', 'newpass') || '',


'0123456789') FROM dual;

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Executing the above SQL statement, the attacker is able to create new

application users

5.1.4 Buffer Overflows

A number of standard Oracle database functions are susceptible to buffer

overflows, which can be exploited through a SQL injection attack in an un-

patched database.

Known buffer overflows exist in the standard database functions like:

tz_offset

to_timestamp_tz

bfilename, from_tz

numtoyminterval

numtodsinterval.

A buffer overflow attack using tz_offset, to_timestamp_tz, bfilename, from_tz,

numtoyminterval, or numtodsinterval is executed using the function injection

methods described previously. By exploiting the buffer overflow via a SQL

injection attack, remote access to the operating system can be achieved.

In addition, most application and web servers do not gracefully handle the loss

of a database connection due to a buffer overflow. Usually, the web process will

hang until the connection to the client is terminated, thus making this a very

effective denial of service attack.

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DETECTION OF VULNERABILITY

To detect whether your application is vulnerable to SQL injection attacks,

follow the given steps:

Step 1: Open the Web site in a browser.

Step 2: Mouse over the links of the Web site with your cursor while paying

attention to the bottom status bar. You will notice the URLs that the links point

to.

Try to find a URL with parameters in it

(Ex.http://www.site.com/articleid.asp?id=42).

Most SQL injection problems are present when the file extensions are “.asp” or

“.cfm”.

When trying to test a site for SQL injection vulnerabilities, look for these files

specifically. And if you don’t see any URLs in the status bar, then just click on

links, and watch the address bar until you find a URL that has parameters.

Step 3: Once a URL with parameters has been found, click the link, and go to

that page. In the address bar, you should now see the URL that was seen in the

status bar, one having parameter values.

Step 4: Here is where the actual testing for hacker protection takes place. There

are 2 methods for testing script for SQL injection. Be sure to test each

parameter value one at a time with both methods.

Method 1: Go to the address bar, click your cursor, and highlight a parameter

value (Ex. Highlight the word value in “name=value”), and replace it with a

single quote (‘). It should now look like “name=’ ”.

Method 2: Go to the address bar, click your cursor, and put a single quote (‘) in

the middle of the value. It should now look like “name=val’ue”

Step 5: Click the ‘GO’ button to send your request to the Web Server.

Step 6: Analyse the response from the Web server for any error messages. Most

database error messages will look similar like:

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Example Error 1:

Microsoft OLE DB Provider for SQL Server error

'80040e14'Unclosed quotation mark before the character string '51

ORDER BY

some_name'./some_directory/some_file.asp, line 5

Example Error 2:

ODBC Error Code = S1000 (General error

[Oracle][ODBC][Ora]ORA-00933: SQL command not properly ended.

Step 7: Sometimes the error message is not obvious and is hidden in the source

of the page. To look for it, you must view the HTML source of the page and

search for the error. To do this in Internet Explorer, click the ‘View’ menu, and

select the ‘Source’option. This will cause Notepad to open with the HTML

source of the page. In Notepad, click the ‘Edit’ menu, and select ‘Find’. A

dialog box will appear that will ask you to 'Find What’. Type the phrase

‘Microsoft OLEDB’ (ODBC), in the text box and then click ‘Find Next’.

If Either Step 6 or 7 is successful, then the Web site is vulnerable to SQL

injection.

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PREVENTING SQL INJECTION ATTACKS

SQL Injection attacks normally occur due to unfiltered user input or some over-

privileged database logins. Some of the common mistakes which make your

application susceptible to SQL Injection attacks are:

Weak input validation.

Dynamic construction of SQL statements with out use of proper type safe

parameters.

Use of over privileged database logins.

SQL Injection attacks can be easily defeated with simple programming changes,

however, developers must be disciplined enough to apply the following

methods to every web accessible procedure and function. Every dynamic SQL

statement must be protected. A single unprotected SQL statement can result in

comprising of the application, data or database server.

Following are some techniques that can be used to prevent SQL Injection

attacks:

7.1 Use Bind Variables

The most powerful protection against SQL injection attacks is the use of bind

variables. Using bind variables will also improve application performance.

Application coding standards should require the use of bind variables in all SQL

statements. No SQL statement should be created by concatenating together

strings and passed parameters. Bind variables should be used for every SQL

statement regardless of when or where the SQL statement is executed. This is

Oracle’s internal coding standard and should also be your organization’s

standard. A very complex SQL injection attack could possibly exploit an

application by storing an attack string in the database, which would be later

executed by a dynamic SQL statement.

7.2 Validate the Input

Every passed string parameter should be validated. Input validation should be

applied first at the client level. The data passed from the client form must be

checked for input validation at the server level before submitting the query to

the database server for execution. If the data fails to pass the validation process,

it should be rejected and error message should be returned to the user.

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Many web applications use hidden fields and other techniques, which also must

be validated. If a bind variable is not being used, special database characters

must be removed or escaped.

For Oracle databases, the only character at issue is a single quote. The simplest

method is to escape all single quotes – Oracle interprets consecutive single

quotes as a literal single quote.

The use of bind variables and escaping of single quotes should not be done for

the same string. A bind variable will store the exact input string in the database

and escaping any single quotes will result in double quotes being stored in the

database.

7.3 Function Security

Standard and custom database functions can be exploited in SQL injection

attacks. Many of these functions can be used effectively in an attack. Oracle is

delivered with hundreds of standard functions and by default all have grants to

PUBLIC. The application may have additional functions which perform

operations like changing passwords or creating users that could be exploited.

All functions that are not absolutely necessary to the application should be

restricted.

7.4 Limit the Open-Ended Input

Try to limit the open-ended input wherever possible, by using select boxes

instead of Text boxes. Application must apply client side validation for all

inputs. For validation only the option in the select box should be taken up and

any other option should be rejected.

7.5 Verify the Type of Data

Verify the data type using ISNUMERIC or equivalent function before passing it

into a SQL statement. For string data replace single quotes with two single

quotes using the replace function or equivalent.

Good string = replace(input string,','');

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7.6 Use Stored Procedures

Use stored procedures avoid direct access to the table. Stored procedures that

are not being used may be deleted such as: master_xp_cmdshell, xp_sendmail,

xp_startmail, sp_makewebtask.

1. Never build dynamic SQL statement directly from the user input and never

concatenate user input, with SQL statements, which is not validated.

2. Filter out characters like slash, backslash, extended characters like NULL,

carry return, new line in all strings from user input and parameters from

URL.

3. Privileges of the user account used in the application for executing SQL

statements on the database must be defined.

4. Length of the user input should be limited.

5. Whenever possible reject input that contains following potentially

dangerous characters.

Table 1. Dangerous characters

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SCREENSHOTS OF SAMPLE APPLICATION

Figure 3. Login Page

Figure 4. User's Home Page

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Figure 5. Injecting SQL

Figure 6. Unauthorized access of data

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CONCLUSION

SQL Injection is an attack methodology that targets the data residing in a

database through the firewall that shields it.

It attempts to modify the parameters of a Web -based application in order to

alter the SQL statements that are parsed to retrieve data from the database.

Database foot printing is the process of mapping out the tables on the database

and is a crucial tool in the hands of an attacker. Exploits occur due to coding

errors as well as inadequate validation checks.

Prevention involves enforcing better coding practices and database

administration procedures.

Remember always patch and update holes because exploits are found commonly

and the attacker is not going to wait.

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REFRENCES

https://www.owasp.org/index.php/Preventing_SQL_Injection_in_Java

http://www.hdm-stuttgart.de/~ms096/SQLInjectionWhitePaper.pdf

http://www.nextgenss.com/papers/advanced_sql_injection.pdf

http://www.appsecinc.com/presentations/Manipulating_SQL_Server_Using_

SQL_Injection.pdf

http://www.w3schools.com/sql/sql_injection.asp

Microsoft. "SQL Injection". Retrieved 2013-08-04. "SQL injection is an

attack in which malicious code is inserted into strings that are later passed to

an instance of SQL Server for parsing and execution. Any procedure that

constructs SQL statements should be reviewed for injection vulnerabilities

because SQL Server will execute all syntactically valid queries that it

receives. Even parameterized data can be manipulated by a skilled and

determined attacker.

We Are Anonymous: Inside the Hacker World of LulzSec". Little, Brown

and Company.

Download - SQL Injections Seminar Report

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