防止sql注入最好的办法是对于提交后台的所有数据都进行过滤转义。
对于简单的情况，比如包含单引号' , 分号;, <, >, 等字符可通过rewrite直接重订向到404页面来避免。
用rewrite有个前提需要知道，一般用rewrite进行正则匹配只能匹配到网页的URI，也就是url中?前部分，?以后部分是请求参数。
问号后面的请求参数，在nginx用$query_string表 示，不能在rewrite中匹配到，需要用if判断
例如，对于参数中带有单引号的'进行匹配然后定向到错误页面，
/plus/list.php?tid=19&mid=1124'rewrite ^.*([;'<>]).* /error.html break;
直接写这样的一条重写肯定不会正确匹配，因为rewrite参数只会匹配请求的uri，也就是/plus/list.php部分。
需要使用$query_string 借助if进行判断，如果查询串种包含特殊字符，返回404。
if ( $query_string ~* ".*[;'<>].*" ){return 404;} 下面来分享一个配置文件实例：
server {## 禁SQL注入 Block SQL injectionsset $block_sql_injections 0;if ($query_string ~ “union.*select.*(“) {set $block_sql_injections 1;}if ($query_string ~ “union.*all.*select.*”) {set $block_sql_injections 1;}if ($query_string ~ “concat.*(“) {set $block_sql_injections 1;}if ($block_sql_injections = 1) {return 444;}## 禁掉文件注入set $block_file_injections 0;if ($query_string ~ “[a-zA-Z0-9_]=http://”) {set $block_file_injections 1;}if ($query_string ~ “[a-zA-Z0-9_]=(..//?)+”) {set $block_file_injections 1;}if ($query_string ~ “[a-zA-Z0-9_]=/([a-z0-9_.]//?)+”) {set $block_file_injections 1;}if ($block_file_injections = 1) {return 444;}## 禁掉溢出攻击set $block_common_exploits 0;if ($query_string ~ “(<|%3C).*script.*(>|%3E)”) {set $block_common_exploits 1;}if ($query_string ~ “GLOBALS(=|[|%[0-9A-Z]{0,2})”) {set $block_common_exploits 1;}if ($query_string ~ “_REQUEST(=|[|%[0-9A-Z]{0,2})”) {set $block_common_exploits 1;}if ($query_string ~ “proc/self/environ”) {set $block_common_exploits 1;}if ($query_string ~ “mosConfig_[a-zA-Z_]{1,21}(=|%3D)”) {set $block_common_exploits 1;}if ($query_string ~ “base64_(en|de)code(.*)”) {set $block_common_exploits 1;}if ($block_common_exploits = 1) {return 444;}## 禁spam字段set $block_spam 0;if ($query_string ~ “b(ultram|unicauca|valium|viagra|vicodin|xanax|ypxaieo)b”) {set $block_spam 1;}if ($query_string ~ “b(erections|hoodia|huronriveracres|impotence|levitra|libido)b”) {set $block_spam 1;}if ($query_string ~ “b(ambien|bluespill|cialis|cocaine|ejaculation|erectile)b”) {set $block_spam 1;}if ($query_string ~ “b(lipitor|phentermin|pro[sz]ac|sandyauer|tramadol|troyhamby)b”) {set $block_spam 1;}if ($block_spam = 1) {return 444;}## 禁掉user-agentsset $block_user_agents 0;# Don't disable wget if you need it to run cron jobs!#if ($http_user_agent ~ “Wget”) {# set $block_user_agents 1;#}# Disable Akeeba Remote Control 2.5 and earlierif ($http_user_agent ~ “Indy Library”) {set $block_user_agents 1;}# Common bandwidth hoggers and hacking tools.if ($http_user_agent ~ “libwww-perl”) {set $block_user_agents 1;}if ($http_user_agent ~ “GetRight”) {set $block_user_agents 1;}if ($http_user_agent ~ “GetWeb!”) {set $block_user_agents 1;}if ($http_user_agent ~ “Go!Zilla”) {set $block_user_agents 1;}if ($http_user_agent ~ “Download Demon”) {set $block_user_agents 1;}if ($http_user_agent ~ “Go-Ahead-Got-It”) {set $block_user_agents 1;}if ($http_user_agent ~ “TurnitinBot”) {set $block_user_agents 1;}if ($http_user_agent ~ “GrabNet”) {set $block_user_agents 1;} if ($http_user_agent ~ "WebBench") { set $block_user_agents 1; } if ($http_user_agent ~ "ApacheBench") { set $block_user_agents 1; } if ($http_user_agent ~ ^$) { set $block_user_agents 1; } if ($http_user_agent ~ "Python-urllib") { set $block_user_agents 1; }if ($block_user_agents = 1) {return 444;}} 
