What are the security settings for PHP?

PHP security settings include: 1. Shield PHP error output; 2. Shield PHP version; 3. Close global variables; 4. File system restrictions; 5. Prohibit remote resource access; 6. Install extensions, etc. .

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I recently talked about PHP security-related issues with my colleagues and recorded them. Some insights.

Due to many reasons of scripting language and early version design, PHP projects have many security risks. From the configuration options, the following optimizations can be made.

#1. Shield PHP error output.
In /etc/php.ini (default configuration file location), change the following configuration value to Off

display_errors=Off

Do not output the error stack information directly to the web page , to prevent hackers from using relevant information.

The correct approach is:
Write the error log to the log file to facilitate troubleshooting.

#2. Block the PHP version.
By default, the PHP version will be displayed in the return header, such as:
Response Headers X-powered-by: PHP/7.2.0

Change the following configuration value in php.ini to Off

expose_php=Off

3. Close global variables.
If global variables are enabled, some form submitted data will be automatically registered as global variables. The code is as follows:

<form action="/login" method="post">
<input name="username" type="text">
<input name="password" type="password">
<input type="submit" value="submit" name="submit">
</form>

If global variables are enabled, the server-side PHP script can use $username and $password to obtain the username and password, which will cause great danger of script injection.

The method to enable it is to modify it in php.ini as follows:

register_globals=On

It is recommended to close it, the parameters are as follows:

register_globals=Off

When it is closed, it can only be accessed from $_POST and $_GET , Get relevant parameters in $_REQUEST.

4. File system restrictions
You can use open_basedir to limit the system directories that PHP can access.

If you use the following script code (hack.php) without restrictions, you can get the system password.

<?php
echo file_get_contents(&#39;/etc/passwd&#39;);

When set, an error will be reported and relevant information will no longer be displayed, so that system directory b will not be illegally accessed:

PHP Warning: file_get_contents(): open_basedir restriction in effect. File(/etc/passwd) is not within the allowed path(s): (/var/www) in /var/www/hack.php on line 3

Warning: file_get_contents(): open_basedir restriction in effect. File(/etc/passwd) is not within the allowed path(s): (/var/www) in /var/www/hack. php on line 3 PHP Warning: file_get_contents(/etc/passwd): failed to open stream: Operation not permitted in /var/www/hack.php on line 3

Warning: file_get_contents(/etc/passwd): failed to open stream: Operation not permitted in /var/www/hack.php on line 3

The setting method is as follows:

open_basedir=/var/www

5. Prohibit remote resource access.

allow_url_fopen=Off

allow_url_include=Off

Other third-party security extensions
6.Suhosin.
Suhosin is a protection system for PHP programs. It was originally designed to protect servers and users from known or unknown flaws in PHP programs and PHP core (it feels quite practical and can resist some minor attacks). Suhosin has two independent parts, which can be used separately or combined.

The first part is a patch for PHP core, which can resist buffer overflow or format string weaknesses (this is a must!);

The second part is a powerful PHP Extension (the extension mode is very good, easy to install...), including all other protection measures.

Install extension

wget http://download.suhosin.org/suhosin-0.9.37.1.tar.gztar zxvf suhosin-0.9.37.1.tar.gz
cd suhosin-0.9.37.1/phpize./configure  --with-php-config=/usr/local/bin/php-config
make
make install
在php.ini下加入suhosin.so即可

extension=suhosin.so

Features

##Emulator protected mode
Add two Functions sha256() and sha256_file() to the PHP core
All platforms, add CRYPT_BLOWFISH to the function crypt()
Turn on transparent protection for the phpinfo() page
SQL Database User Protection (Testing Phase)

Runtime Protection

1. 加密cookies
2. 防止不同种类的包含漏洞（不允许远程URL包含（黑/白名单）；不允许包含已上传的文件；防止目录穿越攻击）
3. 允许禁止preg_replace()
4. 允许禁止eval()函数
5. 通过配置一个最大执行深度，来防止无穷递归
6. 支持每个vhost配置黑白名单
7. 为代码执行提供分离的函数黑白名单
8. 防止HTTP响应拆分漏洞
9. 防止脚本控制memory_limit选项
10. 保护PHP的superglobals，如函数extract()，import_request_vars()
11. 防止mail()函数的新行攻击
12. 防止preg_replace()的攻击

Session 保护

1. 加密session数据
2. 防止session被劫持
3. 防止超长的session id
4. 防止恶意的session id

SESSION里的数据通常在服务器上的明文存放的。这里通过在服务端来加解密$_SESSION。这样将Session的句柄存放在Memcache或数据库时,就不会被轻易攻破，很多时候我们的session数据会存放一些敏感字段。

这个特性在缺省情况下是启用的,也可以通过php.ini来修改：

suhosin.session.encrypt = On
suhosin.session.cryptkey = zuHywawAthLavJohyRilvyecyondOdjo
suhosin.session.cryptua = On
suhosin.session.cryptdocroot = On

;; IPv4 only
suhosin.session.cryptraddr = 0suhosin.session.checkraddr = 0

Cookie加密

Cookie在客户端浏览器的传输的HTTP头也是明文的。通过加密cookie，您可以保护您的应用程序对众多的攻击，如

• Cookie篡改：攻击者可能会尝试猜测其他合理的cookie值来攻击程序。
• 跨应用程序使用Cookie：不正确配置的应用程序可能具有相同的会话存储，如所有会话默认存储在/tmp目录下，一个应用程序的cookie可能永远不会被重新用于另一应用，只要加密密钥不同。

Cookie加密在php.ini中的配置：

suhosin.cookie.encrypt = On

;; the cryptkey should be generated, e.g. with 'apg -m 32'suhosin.cookie.cryptkey = oykBicmyitApmireipsacsumhylWaps1
suhosin.cookie.cryptua = On
suhosin.cookie.cryptdocroot = On

;; whitelist/blacklist (use only one)
;suhosin.cookie.cryptlist = WALLET,IDEAS
suhosin.cookie.plainlist = LANGUAGE

;; IPv4 only
suhosin.cookie.cryptraddr = 0suhosin.cookie.checkraddr = 0Blocking Functions
测试##默认PHP的Session保存在tmp路径下ll  -rt /tmp | grep sess##扩展未开启时查看某条sesson的数据cat  sess_ururh83qvkkhv0n51lg17r4aj6//记录是明文的##扩展开启后查看某条sesson 的数据cat  sess_ukkiiiheedupem8k4hheo0b0v4//记录是密文的可见加密对安全的重要性

阻断功能

白名单

##显式指定指定白名单列表
suhosin.executor.func.whitelist = htmlentities,htmlspecialchars,base64_encode
suhosin.executor.eval.whitelist = htmlentities,htmlspecialchars,base64_encode

<?php
echo htmlentities(&#39;<test>&#39;);
eval(&#39;echo htmlentities("<test>");&#39;);

黑名单

##显式指定指定黑名单列表
suhosin.executor.func.blacklist = assert,unserialize,exec,popen,proc_open,passthru,shell_exec,system,hail,parse_str,mt_srand
suhosin.executor.eval.whitelist = assert,unserialize,exec,popen,proc_open,passthru,shell_exec,system,hail,parse_str,mt_srand
通过日志来查看非法调用黑白名单

suhosin.simulation = 1
suhosin.log.file = 511
suhosin.log.file.name = /tmp/suhosin-alert.log

其他配置项

suhosin.executor.include.max_traversal    扩目录的最大深度，可以屏蔽切换到非法路径
suhosin.executor.include.whitelist        允许包含的URL，用逗号分隔
suhosin.executor.include.blacklist        禁止包含的URL，用逗号分隔
suhosin.executor.disable_eval = On        禁用eval函数

suhosin.upload.max_uploads
suhosin.upload.disallow_elf
suhosin.upload.disallow_binary
suhosin.upload.remove_binary
suhosin.upload.verification_script        上传文件检查脚本，可以来检测上传的内容是否包含webshell特征

使用Suhosin，你可以得到一些错误日志，你能把这些日志放到系统日志中，也可以同时写到其他任意的日志文件中去;

它还可以为每一个虚拟主机创建黑名单和白名单;

可以过滤GET和POST请求、文件上载和cookie;

你还能传送加密的会话和cookie，可以设置不能传送的存储上线等等;

它不像原始的PHP强化补丁，Suhosin是可以被像Zend Optimizer这样的第三方扩展软件所兼容的。

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