Simple hardening of Nginx

I finally got sick of ignoring my web server getting thrashed trying to serve a handful of sites, so I thought I’d harden it up … again.

Seems I’d done it at some stage in the past against common attack vectors, spam and bots. However I’d obviously dropped it in the file(s) said “good enough” and walked away, without confirming it was actually working.

Seems it wasn’t, though the solve was a simple one. In the nginx site configs the 403 redirects of bad actors was happening after the accept traffic blocks – i.e. not at all.

Oops.

Ref: block added to nginx sites (later will change it to live in a common file)

## 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;
}
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 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;
}

## 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 $block_user_agents 0;
# Disable Akeeba Remote Control 2.5 and earlier
if ($http_user_agent ~ "Indy Library") {
    set $block_user_agents 1;
}

if ($http_user_agent ~ "Adsbot|serpstatbot|SemrushBot|AhrefsBot") {
    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;
}