server {
 listen 80;
 server_name site1.test.com;
 root /var/wwwroot/site1;
 index index.html;

 location / {
 }
}

server {
 listen 80;
 server_name site2.test.com;
 root /var/wwwroot/site2;
 index index.html;

 location / {
 }
}

mkdir /var/wwwroot
cd /var/wwwroot
mkdir site1
mkdir site2
echo -e "<h1>site1</h1><img src='1.jpg'>"  site1/index.html
echo -e "<h1>site2</h1><img src='http://site1.test.com/1.jpg'>"  site2/index.html

systemctl restart nginx
netstat -anpt | grep nginx

setenforce 0
firewall-cmd --zone=public --add-port=80/tcp --permanent
firewall-cmd --reload

server {
 listen 80;
 server_name site1.test.com;
 root /var/wwwroot/site1;
 index index.html;

 location / {
 }

 location ~ \.(jpg|png|gif|jpeg)$ {
  valid_referers site1.test.com;
  if ($invalid_referer) {
   return 403;
  }
 }
}
server {
 listen 80;
 server_name site2.test.com;
 root /var/wwwroot/site2;
 index index.html;

 location / {
 }
}

server {
 listen 80;
 server_name site1.test.com;
 root /var/wwwroot/site1;
 index index.html;
 location / {
 }
 location ~ \.(jpg|png|gif|jpeg)$ {
  valid_referers site1.test.com;
  if ($invalid_referer) {
   rewrite ^/ http://site3.test.com/notfound.jpg;
   #return 403;
  }
 }
}
server {
 listen 80;
 server_name site2.test.com;
 root /var/wwwroot/site2;
 index index.html;
 location / {
 }
}
server {
 listen 80;
 server_name site3.test.com;
 root /var/wwwroot/site3;
 index index.html;
 location / {
 }
}

cd /var/wwwroot
mkdir site3
echo -e "<h1>site3</h1><img src='notfound.jpg'>"  site3/index.html