# cd /usr/local/src
  # wget https://github.com/cfsego/file-md5/archive/master.zip -O file-md5-master.zip
  # unzip file-md5-master.zip

  # wget http://nginx.org/download/nginx-1.4.2.tar.gz
  # tar -xzf nginx-1.4.2.tar.gz
  # cd nginx-1.4.2
  # ./configure --prefix=/usr/local/nginx-1.4.2 --add-module=../file-md5-master
  # make
  # make isntall

  server {
    listen    80;
    server_name test.ttlsa.com;
    root /data/site/test.ttlsa.com;
  
    # for add content-md5 to http header
    location ~ /download
    {
        add_header  Content-MD5  $file_md5;
    }
  }

  # curl -I test.ttlsa.com/download/1.exe  
  HTTP/1.1 200 OK
  Server: nginx
  Date: Wed, 26 Feb 2014 03:00:05 GMT
  Content-Type: application/octet-stream
  Content-Length: 1535488
  Last-Modified: Mon, 24 Feb 2014 10:08:10 GMT
  Connection: keep-alive
  ETag: "530b1a0a-176e00"
  Content-MD5: 6adda4a06dbad3ac9b53a08f4ff9c4f8
  Accept-Ranges: bytes

  server {
    listen    80;
    server_name test.ttlsa.com;
    root /data/site/test.ttlsa.com;
 
    # for add content-md5 to http header
    location ~ /download
    {
      if ( $arg_md5 ~* "true" ){
        echo $file_md5;
      }
    }
  }

  # curl test.ttlsa.com/download/1.exe?md5=true  
  6adda4a06dbad3ac9b53a08f4ff9c4f8

location /
 {
 ...
 proxy_max_temp_file_size 2048m;
 ...
 }

# /usr/local/nginx-1.7.0/sbin/nginx -s reload