http://www.hardened-php.net/suhosin/
Hardened-PHP 最近推出了 Suhosin 測試版（beta version），這是一個從原始碼層面提升 PHP 安全性的系統，所以不論是已知和尚未發現的安全性漏洞，不論這些漏洞出現在應用程式還是在 PHP 的核心部分，Suhosin 的安全關卡都可以防止這些漏洞做成破壞。
Suhosin 是一個韓語的音譯，意思大約是守護天使，但是別誤會 Hardened-PHP 是由韓國人組成，它其實是由三名知名的 PHP 保安專家和 PHP 核心編程人員合作的網站。
Suhosin 由兩部分組成，第一部份是 PHP 核心的補丁，提供低階的安全保護，例如緩衝區溢滿等，第二部分是一個 PHP 擴充模組，提供多項保護功能，包括：
- 自動把 cookies 加密／解密
- 容許關閉 preg_replace() 中的 /e 選項
- 容許關閉 eval()
- 透過設定函式呼叫層數的限制，避免出現無窮遞歸（infinite recursion）
- 防止應用程式修改 memory_limit
- 保護 mail() 免受「newline 攻擊」
- 保護 preg_replace() 免受「/0 攻擊」
- 自動加密／解密 session 數據
- 保護 session 免受騎劫
- 若果用戶呈交的資料包含 GLOBALS、_GET、_COOKIE 等敏感名稱，一律過濾掉
- 容許設定用戶呈交的資料的數量和長度上限
- 從上載檔案中自動禁止那些可以在伺服器上執行的程式
http://blog.m6699.com/diomedea/article/29073.html
http://www.93198.com/Article/wl/Php/3707.html
http://www.jefflei.com/post/295.html
當apache的errorlog出現configured request variable name length limit exceeded
之前在寫Picasa2Wordpress的時候，測試的時候，遇到一個詭異的問題，在我有權限能access的機器們上面跑，就是有一台跑不起來，後來查了一下apache2的log才發現，原來是php suhosin module的問題，預設最大的POST及GET變數名稱最大只能夠是64字元，但是Picasa POST出去的卻遠超過，所以就被檔下來了。
解決方法很簡單，編輯/etc/php5/apache2/conf.d/suhosin.ini，加上下面這三行即可:
suhosin.request.max_varname_length=128
suhosin.get.max_name_length=128
suhosin.post.max_name_length=128
搞定收工。
http://advosys.ca/papers/web/62-php-hardening-suhosin.html
I've always compiled Suhosin with any of the Apache builds I've made in WHM on production/public servers. On every server CodeCall has been on, it has been there. The purpose of Suhosin is to protect servers and users from known flaws in PHP.
I never had a problem with it before. I've seen it strip variables and prevent server requests in the log files and it always seemed to help. Last night I ran into something annoying: Suhosin limits the character length for any request variable. It doesn't truncate the value as you might expect, it drops the variable completely.
I needed the ability to post considerably long string queries for ASCIIBin. For some reason the variables were being dropped and an empty BIN was being created. I couldn't figure out why. It worked fine on my test box (which didn't have suhosin) and I could see the data before actual POST using JavaScript. After some time I came to realize that Suhosin was the culprit.
The Fix
Taking a look at the documentation for Suhosin, you can figure out fairly quick that post.max_value_length is the configuration variable limiting character size.
The default character limit is 65,000.
Method 1: Obviously, you can just disable Suhosin to fix the problem. Remove the suhosin.o file from your php.ini config file and restart Apache.
Method 2: You probably want to keep Suhosin around so a different approach is to edit the configuration file. The file is named suhosin.ini, following the PHP ini configuration system. I added these lines:
suhosin.post.max_vars = 5000 suhosin.post.max_value_length = 500000 suhosin.request.max_vars = 5000 suhosin.request.max_value_length = 500000
Restart apache.
Method 3: Alternatively, you can change these values per user using .htaccess. Edit the .htaccess file in the user directory and set the parameters to what you want. Here is an example:
php_value suhosin.post.max_vars 5000 php_value suhosin.post.max_value_length 500000 php_value suhosin.request.max_vars 5000 php_value suhosin.request.max_value_length 500000
Conclusion
I hope this helps you if you ever run into the same situation. Perhaps it will save you some time. I know if there had been a post labeled "PHP POST character limit" and was indexed by google, I would have an hour of my time saved. Alas, there isn't so I'm making one.
