Nginx: security vs conditionals

Question

I was reading around looking for some security steps that can be taken in Nginx to protect apps I'm serving using Nginx as a reverse proxy. I found this code which has some good things in it to protect sites, but it's full of conditionals and the documentation has discouraged me from using them.

My questions to Nginx experts:

Is there a better way to go about this?
Is there a commonly used snippet like this somewhere that ditches the conditionals?
Do I need this at all?

Advice appreciated.

## Block SQL injections
set $block_sql_injections 0;
if ($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 403;
}

## Block file injections
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 403;
}

## Block common exploits
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 403;
}

## Block spam
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|blue\spill|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 403;
}

## Block user agents
set $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 earlier
if ($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 ($block_user_agents = 1) {
    return 403;
}

Why don't you just use ModSecurity? – Michael Hampton Dec 23 '13 at 21:33 — Michael Hampton, Dec 23 '13 at 21:33

score 1 · Answer 1 · answered Apr 09 '14 at 08:32

This configuration checks only get parameters. But sqli or lfi cat be exploited via post, or cookie, or even http headers and files. The better way is use WAF(web application firewall), ex enter link description here.

But there is no ideal WAF, it is only one line of protection. Ensure that you validate users input, sanitize output, use prepared statements for SQL queries and follow other good practises

Nginx: security vs conditionals

1 Answers1