How to prevent sql injection?
一、SQL注入简介
SQL注入是比较常见的网络攻击方式之一，它不是利用操作系统的BUG来实现攻击，而是针对程序员编程时的疏忽，通过SQL语句，实现无帐号登录，甚至篡改数据库。
二、SQL注入攻击的总体思路
1.寻找到SQL注入的位置
2.判断服务器类型和后台数据库类型
3.针对不通的服务器和数据库特点进行SQL注入攻击
三、SQL注入攻击实例
比如在一个登录界面，要求输入用户名和密码：
可以这样输入实现免帐号登录：
用户名： ‘or 1 = 1 –
密 码：
点登陆,如若没有做特殊处理,那么这个非法用户就很得意的登陆进去了.(当然现在的有些语言的数据库API已经处理了这些问题)
这是为什么呢? 下面我们分析一下：
从理论上说，后台认证程序中会有如下的SQL语句：
String sql = "select * from user_table where username= ' "+userName+" ' and password=' "+password+" '";
当输入了上面的用户名和密码，上面的SQL语句变成：
SELECT * FROM user_table WHERE username= '’or 1 = 1 -- and password='’
分析SQL语句：
条件后面username=”or 1=1 用户名等于 ” 或1=1 那么这个条件一定会成功；
然后后面加两个-，这意味着注释，它将后面的语句注释，让他们不起作用，这样语句永远都能正确执行，用户轻易骗过系统，获取合法身份。
这还是比较温柔的，如果是执行
SELECT * FROM user_table WHERE username='' ;DROP DATABASE (DB Name) --' and password=''
….其后果可想而知…
四、应对方法
下面我针对JSP，说一下应对方法：
1.（简单又有效的方法）PreparedStatement
采用预编译语句集，它内置了处理SQL注入的能力，只要使用它的setXXX方法传值即可。
使用好处：
(1).代码的可读性和可维护性.
(2).PreparedStatement尽最大可能提高性能.
(3).最重要的一点是极大地提高了安全性.
原理：
sql注入只对sql语句的准备(编译)过程有破坏作用
而PreparedStatement已经准备好了,执行阶段只是把输入串作为数据处理,
而不再对sql语句进行解析,准备,因此也就避免了sql注入问题.
2.使用正则表达式过滤传入的参数
要引入的包：
import java.util.regex.*;
正则表达式：
private String CHECKSQL = “^(.+)\\sand\\s(.+)|(.+)\\sor(.+)\\s$”;
判断是否匹配：
Pattern.matches(CHECKSQL,targerStr);
下面是具体的正则表达式：
检测SQL meta-characters的正则表达式 ：
/(\%27)|(\’)|(\-\-)|(\%23)|(#)/ix
修正检测SQL meta-characters的正则表达式 ：/((\%3D)|(=))[^\n]*((\%27)|(\’)|(\-\-)|(\%3B)|(:))/i
典型的SQL 注入攻击的正则表达式 ：/\w*((\%27)|(\’))((\%6F)|o|(\%4F))((\%72)|r|(\%52))/ix
检测SQL注入，UNION查询关键字的正则表达式 ：/((\%27)|(\’))union/ix(\%27)|(\’)
检测MS SQL Server SQL注入攻击的正则表达式：
/exec(\s|\+)+(s|x)p\w+/ix
等等…..
3.字符串过滤
比较通用的一个方法：
（||之间的参数可以根据自己程序的需要添加）
public static boolean sql_inj(String str){
String inj_str = "'|and|exec|insert|select|delete|update|
count|*|%|chr|mid|master|truncate|char|declare|;|or|-|+|,";
String inj_stra[] = split(inj_str,"|");
for (int i=0 ; i < inj_stra.length ; i++ ){
if (str.indexOf(inj_stra[i])>=0){
return true;
}
}
return false;
}4.jsp中调用该函数检查是否包函非法字符
防止SQL从URL注入：
sql_inj.java代码：
package sql_inj;
import java.net.*;
import java.io.*;
import java.sql.*;
import java.text.*;
import java.lang.String;
public class sql_inj{
public static boolean sql_inj(String str){
String inj_str = "'|and|exec|insert|select|delete|update|
count|*|%|chr|mid|master|truncate|char|declare|;|or|-|+|,";
//这里的东西还可以自己添加
String[] inj_stra=inj_str.split("\\|");
for (int i=0 ; i < inj_stra.length ; i++ ){
if (str.indexOf(inj_stra[i])>=0){
return true;
}
}
return false;
}
}5.JSP页面判断代码：
使用javascript在客户端进行不安全字符屏蔽
功能介绍：检查是否含有”‘”,”\\”,”/”
参数说明：要检查的字符串
返回值：0：是1：不是
函数名是
function check(a){
return 1;
fibdn = new Array (”‘” ,”\\”,”/”);
i=fibdn.length;
j=a.length;
for (ii=0; ii＜i; ii++)
{ for (jj=0; jj＜j; jj++)
{ temp1=a.charAt(jj);
temp2=fibdn[ii];
if (tem’; p1==temp2)
{ return 0; }
}
}
return 1;
}总的说来，防范一般的SQL注入只要在代码规范上下点功夫就可以了。
凡涉及到执行的SQL中有变量时，用JDBC（或者其他数据持久层）提供的如：PreparedStatement就可以 ，切记不要用拼接字符串的方法就可以了。
本文主要讲了五种实现防止sql注入的方法，更多相关内容请关注php中文网。
相关推荐：
The above is the detailed content of How to prevent sql injection?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
What is the difference between HQL and SQL in Hibernate framework?
Apr 17, 2024 pm 02:57 PM
HQL and SQL are compared in the Hibernate framework: HQL (1. Object-oriented syntax, 2. Database-independent queries, 3. Type safety), while SQL directly operates the database (1. Database-independent standards, 2. Complex executable queries and data manipulation).
Usage of division operation in Oracle SQL
Mar 10, 2024 pm 03:06 PM
"Usage of Division Operation in OracleSQL" In OracleSQL, division operation is one of the common mathematical operations. During data query and processing, division operations can help us calculate the ratio between fields or derive the logical relationship between specific values. This article will introduce the usage of division operation in OracleSQL and provide specific code examples. 1. Two ways of division operations in OracleSQL In OracleSQL, division operations can be performed in two different ways.
Comparison and differences of SQL syntax between Oracle and DB2
Mar 11, 2024 pm 12:09 PM
Oracle and DB2 are two commonly used relational database management systems, each of which has its own unique SQL syntax and characteristics. This article will compare and differ between the SQL syntax of Oracle and DB2, and provide specific code examples. Database connection In Oracle, use the following statement to connect to the database: CONNECTusername/password@database. In DB2, the statement to connect to the database is as follows: CONNECTTOdataba
Detailed explanation of the Set tag function in MyBatis dynamic SQL tags
Feb 26, 2024 pm 07:48 PM
Interpretation of MyBatis dynamic SQL tags: Detailed explanation of Set tag usage MyBatis is an excellent persistence layer framework. It provides a wealth of dynamic SQL tags and can flexibly construct database operation statements. Among them, the Set tag is used to generate the SET clause in the UPDATE statement, which is very commonly used in update operations. This article will explain in detail the usage of the Set tag in MyBatis and demonstrate its functionality through specific code examples. What is Set tag Set tag is used in MyBati
What does the identity attribute in SQL mean?
Feb 19, 2024 am 11:24 AM
What is Identity in SQL? Specific code examples are needed. In SQL, Identity is a special data type used to generate auto-incrementing numbers. It is often used to uniquely identify each row of data in a table. The Identity column is often used in conjunction with the primary key column to ensure that each record has a unique identifier. This article will detail how to use Identity and some practical code examples. The basic way to use Identity is to use Identit when creating a table.
How to implement Springboot+Mybatis-plus without using SQL statements to add multiple tables
Jun 02, 2023 am 11:07 AM
When Springboot+Mybatis-plus does not use SQL statements to perform multi-table adding operations, the problems I encountered are decomposed by simulating thinking in the test environment: Create a BrandDTO object with parameters to simulate passing parameters to the background. We all know that it is extremely difficult to perform multi-table operations in Mybatis-plus. If you do not use tools such as Mybatis-plus-join, you can only configure the corresponding Mapper.xml file and configure The smelly and long ResultMap, and then write the corresponding sql statement. Although this method seems cumbersome, it is highly flexible and allows us to
How to solve the 5120 error in SQL
Mar 06, 2024 pm 04:33 PM
Solution: 1. Check whether the logged-in user has sufficient permissions to access or operate the database, and ensure that the user has the correct permissions; 2. Check whether the account of the SQL Server service has permission to access the specified file or folder, and ensure that the account Have sufficient permissions to read and write the file or folder; 3. Check whether the specified database file has been opened or locked by other processes, try to close or release the file, and rerun the query; 4. Try as administrator Run Management Studio as etc.
How to use SQL statements for data aggregation and statistics in MySQL?
Dec 17, 2023 am 08:41 AM
How to use SQL statements for data aggregation and statistics in MySQL? Data aggregation and statistics are very important steps when performing data analysis and statistics. As a powerful relational database management system, MySQL provides a wealth of aggregation and statistical functions, which can easily perform data aggregation and statistical operations. This article will introduce the method of using SQL statements to perform data aggregation and statistics in MySQL, and provide specific code examples. 1. Use the COUNT function for counting. The COUNT function is the most commonly used
