# Frontend API server that:
# 1. Acts as the HTTPS termination point.
# 2. Authorizes HTTP requests with secret token header
#    and forwards to BDB backend.
# 3. Forwards BDB WS requests to BDB backend.
# 4. Does health check with LB.

worker_processes 2;
daemon off;
user nobody nogroup;
pid /tmp/nginx.pid;
error_log /dev/stderr;

events {
  # Each worker handles up to 512 connections. Increase this for heavy
  # workloads.
  worker_connections 512;
  accept_mutex on;
  use epoll;
}

http {
  access_log /dev/stdout combined buffer=16k flush=5s;

  # Allow 10 req/sec from the same IP address, and store the counters in a
  # `zone` or shared memory location tagged as 'one'.
  limit_req_zone $binary_remote_addr zone=one:10m rate=10r/s;

  # Enable logging when requests are being throttled.
  limit_req_log_level notice;

  # HTTP status code that is returned to the client; 429 is for TooManyRequests,
  # ref. RFC 6585
  limit_req_status 429;

  # Limit requests from the same client, allow `burst` to 20 r/s,
  # `nodelay` or drop connection immediately in case it exceeds this
  # threshold.
  limit_req zone=one burst=20 nodelay;

  # `slowloris` attack mitigation settings.
  client_body_timeout 10s;
  client_header_timeout 10s;

  # Do not expose nginx data/version number in error response and header
  server_tokens off;

  # To prevent cross-site scripting
  add_header X-XSS-Protection "1; mode=block";

  # DNS resolver to use for all the backend names specified in this configuration.
  resolver DNS_SERVER valid=30s ipv6=off;

  keepalive_timeout 60s;

  # The following map blocks enable lazy-binding to the backend at runtime,
  # rather than binding as soon as NGINX starts.
  map $remote_addr $bdb_backend {
    default PLANETMINT_BACKEND_HOST;
  }

  # Frontend server for the external clients; acts as HTTPS termination point.
  server {
    listen NODE_FRONTEND_PORT ssl;
    server_name "NODE_FQDN";

    ssl_certificate /etc/nginx/ssl/cert.pem;
    ssl_certificate_key /etc/nginx/ssl/cert.key;
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_ciphers HIGH:!aNULL:!MD5;

    underscores_in_headers on;

    # Forward websockets directly to backend BDB.
    location /api/v1/streams/valid_transactions {
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

      proxy_pass http://$bdb_backend:PLANETMINT_WS_PORT;
      proxy_read_timeout 600s;
      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection "upgrade";
    }

    # Forward other URL paths as per business logic/use case to BDB or
    # OpenResty instance.
    location / {
      set $auth_check 1; #Flag to authorize POST requests
      proxy_ignore_client_abort on;
      proxy_set_header X-Real-IP  $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

      # max client request body size: avg transaction size.
      client_max_body_size 15k;

      if ($request_method = 'OPTIONS') {
          add_header 'Access-Control-Allow-Origin' '*';
          add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
          add_header 'Access-Control-Allow-Headers' 'DNT,X-Secret-Access-Token,User-Agent';
          add_header 'Access-Control-Max-Age' 43200;
          add_header 'Content-Type' 'text/plain charset=UTF-8';
          add_header 'Content-Length' 0;
          return 204;
      }

      if ( $http_x_secret_access_token != "SECRET_ACCESS_TOKEN" ) {
          set $auth_check 0;
      }
      if ($request_method = POST ) {
          set $auth_check "${auth_check}1";
      }

      if ( $auth_check = "01" ) {
          return 403;
      }

      # No auth for GETs, forward directly to BDB.
      if ($request_method = GET) {
        proxy_pass http://$bdb_backend:PLANETMINT_API_PORT;
      }

      if ($request_method = POST ) {
          proxy_pass http://$bdb_backend:PLANETMINT_API_PORT;
      }

      # Only return this reponse if request_method is neither POST|GET|OPTIONS
      if ($request_method !~ ^(GET|OPTIONS|POST)$) {
          return 444;
      }
    }
  }

  # Frontend server for the load balancer to respond to health checks.
  server {
    listen HEALTH_CHECK_PORT;

    location = /health {
      return 200;
    }
  }

  # Frontend server for the external clients; returns a pretty error message
  # when an HTTP request is sent instead of HTTPS.
  server {
    listen 80;
    server_name "NODE_FQDN";

    location / {
        add_header Upgrade "TLS/1.2, HTTP/1.1" always;
        default_type text/plain;
        return 426 'Consider using the HTTPS protocol next time!';
    }
  }
}

# NGINX stream block for TCP and UDP proxies.
stream {
  log_format bdb_log '[$time_iso8601] $realip_remote_addr $remote_addr '
                     '$proxy_protocol_addr $proxy_protocol_port '
                     '$protocol $status $session_time $bytes_sent '
                     '$bytes_received "$upstream_addr" "$upstream_bytes_sent" '
                     '"$upstream_bytes_received" "$upstream_connect_time" ';

  access_log /dev/stdout bdb_log buffer=16k flush=5s;

  # Define a zone 'two' of size 10 megabytes to store the counters
  # that hold number of TCP connections from a specific IP address.
  limit_conn_zone $binary_remote_addr zone=two:10m;

  # Enable logging when connections are being throttled.
  limit_conn_log_level notice;

  # Allow 256 connections from the same IP address.
  limit_conn two 256;

  # DNS resolver to use for all the backend names specified in this configuration.
  resolver DNS_SERVER valid=30s ipv6=off;

  # The following map blocks enable lazy-binding to the backend at runtime,
  # rather than binding as soon as NGINX starts.
  map $remote_addr $bdb_backend {
    default PLANETMINT_BACKEND_HOST;
  }

  # Server to forward connection to nginx instance hosting
  # tendermint node public key.
  server {
    listen TM_PUB_KEY_ACCESS_PORT;
    proxy_pass $bdb_backend:TM_PUB_KEY_ACCESS_PORT;
  }

  # Server to forward p2p connections to Tendermint instance.
  server {
    listen TM_P2P_PORT so_keepalive=3m:1m:5;
    preread_timeout 60s;
    tcp_nodelay on;
    proxy_pass $bdb_backend:TM_P2P_PORT;
  }
}