Impact of SQL Injection

   Retrieval of Crucial Data
   Data Manupulation
   Alter database State
   Revoke Database Service

Developers are ignorant that their above query can be misused to an extent that it can list login names and passwords, which is relevant and crucial information for an organization. An invader can give input as
Code :

p'or upper(s_empname) like'%
p'or'p'='p

Code sql:

SELECT USERNAME, PASSWORD FROM USERS
WHERE USERNAME = ''
OR 1=1

SQL Injection: Example

A procedure P_GET_SAL was created to get the salary of input Employee Id.

Code sql:

CREATE OR REPLACE PROCEDURE P_GET_SAL  (P_ENAME VARCHAR2 DEFAULT NULL)
AS
CUR SYS_REFCURSOR;
V_ENAME VARCHAR2(100);
V_SAL NUMBER;
BEGIN
  V_STMT := 'SELECT ENAME, SALARY FROM EMPLOYEE  WHERE ENAME = '''|| P_ENAME || '''';
  DBMS_OUTPUT.PUT_LINE(V_STMT); 
  OPEN CUR FOR V_STMT;
  LOOP
    FETCH CUR INTO V_ENAME, V_SAL;
    EXIT WHEN CUR%NOTFOUND;
    DBMS_OUTPUT.PUT_LINE('Employee : '||V_ENAME||' draws '||TO_CHAR(V_SAL));
  END LOOP;
  CLOSE CUR;
END;



Code sql:

SQL> EXEC P_GET_SAL(‘KING’);
Employee KING draws 4500

PL/SQL PROCEDURE successfully completed.


Code sql:

SQL> EXEC P_GET_SAL('KING'' UNION SELECT ENAME, SALARY FROM EMPLOYEE WHERE 1=1');
Employee KING draws 4500
Employee ALLEN draws 1200
Employee MIKE draws 3400
Employee KATE draws 2300
Employee PAUL draws 6400
Employee TOMY draws 2700
Employee JENNY draws 6200
Employee JAKES draws 4600

PL/SQL PROCEDURE successfully completed.



Several strategies can be adopted to safeguard the SQL code and eradicate the impacts of SQL injection in applications. Some of them are listed below.

1. Use of Static SQL
2. Using Invoker’s rights
3. Use of Dynamic SQL with bind arguments
4. Validate and sanitize input using DBMS_ASSERT

-------

ESCAPE With LIKE Operator

ESCAPE With LIKE Operator

select ename from scott.emp where ename like '%_%';

But you will be surprised to see the results:

ENAME
------------
Will dispaly all Data in the Table

it is because _ is a wild card character. That is _ stands for any character. So the query yielded all the rows.

modified query to get the desired output as below:


select ename from scott.emp where ename like '%#_%' escape '#';

ENAME
------------
FRA_KLIN

Tuning the LIKE-clause

Tuning the LIKE-clause (by using reverse key indexes)

For tuning Like operator (like '%SON') is to create a REVERSE index - and then programmatically reverse the LIKE-clause to read LIKE 'NOS%'

Steps:

CREATE INDEX Cust_Name_reverese_idx
ON customer(Cust_Name) REVERSE;

2. Programmatically reverse the SQL LIKE-clause to read '%saliV%':

SELECT * FROM customer WHERE Cust_Name LIKE '%Vilas%'

New Query:

SELECT * FROM customer WHERE Cust_Name LIKE '%saliV%';