PHP Prevent SQL Injection Implementation method

How SQL injection Works

Constructing a database query is a very straightforward process. Typically, it will follow the following ideas. Just to illustrate the problem, we will assume that you have a

Wine database Table "Wines", which has a field of "variety" (i.e. wine type):

1. Provide a form-allows users to submit certain content to search for. Let's assume that the user chooses to search for a wine of type "Lagrein".

2. Retrieve the user's search term and save it-by assigning it to a variable that looks like this:

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$variety = $_post[' variety '];

Therefore, the value of the variable $variety is now:

Lagrein

3. Then, use the variable to construct a database query in the WHERE clause:

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$query = "SELECT * FROM Wines WHERE variety= ' $variety '";

Therefore, the value of the variable $query now looks like this:

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SELECT * FROM Wines WHERE variety= ' Lagrein '

4. Submit the query to the MySQL server.

5. mysql returns all records in the wines table-where the value of the field variety is "Lagrein".

So far, this should be a familiar and very relaxing process. Unfortunately, sometimes the processes we know and feel comfortable with are easy

Cause us to be complacent. Now, let's re-examine the query we just built.

1. The fixed portion of the query you create ends with a single quote, which you will use to describe the beginning of the variable value:

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$query = "SELECT * FROM wines WHERE variety = '";

2. Use the original invariant part and the value that contains the user-submitted variable:

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$query. = $variety;

3. Then, you use another single quotation mark to connect to this result-to describe the end of the variable value:

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$ query. = "'";

Thus, the value of the $query is as follows:

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SELECT * FROM wines WHERE variety = ' Lagrein '

The success of this construct relies on the input of the user. In this example, you are using a single word (or maybe a group of words) to indicate a wine type.

As a result, the query is built without any problems, and the result will be what you would expect-a wine list with a wine type of "Lagrein". Is

In, let's imagine, since your users are not typing a simple type of wine that is "Lagrein", they enter the following content (note that the package

Enclose two punctuation marks):

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Lagrein ' or 1=1;

Now, you continue to construct your query using the previously fixed sections (here, we only show the result values of the $query variable):

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SELECT * FROM wines WHERE variety = '

You then connect to it using the value of the variable containing the user's input (here, in bold):

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SELECT * FROM wines WHERE variety = ' lagrein ' or 1=1;

Finally, add the following quote below:

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SELECT * FROM wines WHERE variety = ' lagrein ' or 1=1; '

Condensation of the above problems we write a function that can be prevented.

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/** +---------------------------------------------------------- * Anti-mount horse, anti-cross-site attack, anti-SQL injection function +------------- --------------------------------------------- * $date incoming arguments, if a variable or array; $ignore the magic Reference of the _magic_quotes variable +------- --------------------------------------------------- */ function in ($data, $ignore _magic_quotes=false) {  if (is_string ($data))  {    $data =trim (Htmlspecialchars ($data));//prevent horse from being hanged, cross station attack   if (($ignore _magic_quotes==true) | | (!GET_MAGIC_QUOTES_GPC ()))   {      $data = addslashes ($data);//Prevent SQL injection  &NBSP}    return  $data;  }  else if (Is_array ($data))//If the array uses recursive filtering  {   foreach ($data as $key => $value)   {     $data [$key]=in ($value);      return $data; &NBSP}  else  {   return $data;  }  }

When the above data is accepted we can prevent the horse from being hanged, cross station attack, prevent SQL injection waiting

Here's how to do security configuration on the server side

(1) Open PHP security mode

PHP's Safe mode is a very important embedded security mechanism that can control functions in PHP, such as System (),

At the same time, a lot of file operation functions are controlled by permissions, also do not allow some key file files, such as/etc/passwd,

But the default php.ini is not open safe mode, we turn it on:

Safe_mode = On

(2) User group security

When the Safe_mode is turned on, the Safe_mode_gid is turned off, so the PHP script can access the file and the same

Users of a group can also access files.

The recommended setting is:

Safe_mode_gid = Off

If you do not set it, we may not be able to operate on our server web directory files, such as we need

When you are working on a file.

(3) Safe Mode executable Program Home directory

If Safe mode is open, but you want to execute some programs, you can specify the home directory where you want to execute the program:

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Safe_mode_exec_dir = D:/usr/bin

In general, there is no program to perform, so it is recommended not to execute the System program directory, you can point to a directory,

Then copy the program that needs to be executed, such as:

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Safe_mode_exec_dir = D:/tmp/cmd

However, I recommend that you do not execute any programs, then you can point to our web directory:

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Safe_mode_exec_dir = d:/usr/www

(4) Include files in Safe mode

If you want to include some public files in Safe mode, modify the options:

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Safe_mode_include_dir = d:/usr/www/include/

In fact, the general PHP script contains files are in the program itself has been written, this can be set according to the specific needs.

(5) Control the directory that the PHP script can access

Using the Open_basedir option to control PHP scripts can only access the specified directory, so that you can avoid PHP script access

Files that should not be accessed, to some extent limit the harm of phpshell, we can generally set to access only the site directory:

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Open_basedir = d:/usr/www

(6) Close the dangerous function

If Safe mode is turned on, the function prohibition is not necessary, but we consider it for security. Like what

We don't feel like executing PHP functions that can execute commands, including system (), or can view PHP information

Phpinfo () and so on, then we can ban them:

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Disable_functions = System,passthru,exec,shell_exec,popen,phpinfo

If you want to disable the operation of any files and directories, you can turn off many file operations

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Disable_functions = Chdir,chroot,dir,getcwd,opendir,readdir,scandir,fopen,unlink,delete,copy,mkdir, Rmdir,rename,file,file_get_contents,fputs,fwrite,chgrp,chmod,chown

The above is just a list of not commonly used file processing functions, you can also perform the above command function and this function combined,

will be able to resist most of the Phpshell.

(7) Turn off the disclosure of PHP version information in HTTP headers

In order to prevent hackers from obtaining information about the PHP version of the server, you can turn off the information ramp in the HTTP header:

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expose_php = Off

For example, when the hacker in Telnet www.12345.com 80, then will not be able to see the PHP information.

(8) Turning off registration of global variables

Variables submitted in PHP, including those submitted using post or get, are automatically registered as global variables and can be accessed directly.

This is very unsafe for the server, so we cannot have it registered as a global variable and turn off the registration global variable option:

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Register_globals = Off

Of course, if you set this up, then you need to get the corresponding variable in a reasonable way, such as getting the variable var of get commit,

Then you need to use $_get[' var ' to get it, the PHP programmer should pay attention.

(9) Open MAGIC_QUOTES_GPC to prevent SQL injection

SQL injection is a very dangerous problem, small web site backstage was invaded, heavy the entire server fell,

So be sure to be careful. There is a setting in php.ini:

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MAGIC_QUOTES_GPC = Off

This default is turned off, and if it is turned on, it will automatically convert the user to the SQL query.

For example, the ' switch ' and so on, which has a significant effect on preventing SQL injection. So we recommend setting it to:

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MAGIC_QUOTES_GPC = On

(10) Error information control

General PHP is not connected to the database or other circumstances will be prompted error, the general error message will contain PHP script when

Before the path information or query SQL statements, such as information, such information provided to hackers, is not secure, so the general server recommended to prohibit error prompts:

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Display_errors = Off

If you are trying to display an error message, be sure to set the level at which the error is displayed, such as displaying only the information above the warning:

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error_reporting = e_warning & E_error

Of course, I recommend closing the error prompt.

(11) Error log

It is recommended that the error message can be logged after the display_errors is turned off to make it easier to find out why the server is running:

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Log_errors = On

Also set the directory where the error log is stored, and suggest that the log of the root Apache be present together:

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Error_log = D:/usr/local/apache2/logs/php_error.log

Note: You must allow the Apache users and groups to have write permissions to the file.

MySQL's Down right run

Create a new user like Mysqlstart

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NET user Mysqlstart Fuckmicrosoft/add net localgroup users Mysqlstart/del

Does not belong to any group

If MySQL is installed in D:mysql, then give Mysqlstart Full control of the permissions

Then in the system service settings, MySQL service properties, in the login attribute, select this user mysqlstart then enter the password, OK.

Restart the MySQL service, and MySQL runs under low privileges.

If you're building Apache under the WinDOS platform, we need to be aware that Apache runs by default is System privilege,

It was scary, and it made people feel uncomfortable. Then let's give Apache a drop in privileges.

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NET user Apache Fuckmicrosoft/add net localgroup users Apache/del

OK. We have established a user apche that does not belong to any group.

We open the Computer Manager, select the service, point Apache Service Properties, we select Log on, choose this account, we fill in the above established

's account and password,

Restart the Apache service, Ok,apache running under low privileges.

In fact, we can also set the permissions of each folder, so that the Apache users can only do what we want it to do, for each directory to create

A user who can read and write alone

This article from the program to the database and the final configuration of the Web server has been described, we refer to this article should be safe a lot of oh, the general injection

There is no way to achieve it.