//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.servlets;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.io.OutputStreamWriter;
  import java.io.Writer;
  import java.nio.charset.Charset;
  import java.util.Enumeration;
  import java.util.HashMap;
  import java.util.Locale;
  import java.util.Map;
  
  import javax.servlet.AsyncContext;
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.eclipse.jetty.http.HttpMethod;
  import org.eclipse.jetty.util.IO;
  import org.eclipse.jetty.util.MultiMap;
  import org.eclipse.jetty.util.StringUtil;
  import org.eclipse.jetty.util.UrlEncoded;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  /**
   * CGI Servlet.
   * <p>
   * The following init parameters are used to configure this servlet:
   * <dl>
   * <dt>cgibinResourceBase</dt>
   * <dd>Path to the cgi bin directory if set or it will default to the resource base of the context.</dd>
   * <dt>resourceBase</dt>
   * <dd>An alias for cgibinResourceBase.</dd>
   * <dt>cgibinResourceBaseIsRelative</dt>
   * <dd>If true then cgibinResourceBase is relative to the webapp (eg "WEB-INF/cgi")</dd>
   * <dt>commandPrefix</dt>
   * <dd>may be used to set a prefix to all commands passed to exec. This can be used on systems that need assistance to execute a
   * particular file type. For example on windows this can be set to "perl" so that perl scripts are executed.</dd>
   * <dt>Path</dt>
   * <dd>passed to the exec environment as PATH.</dd>
   * <dt>ENV_*</dt>
   * <dd>used to set an arbitrary environment variable with the name stripped of the leading ENV_ and using the init parameter value</dd>
   * <dt>useFullPath</dt>
   * <dd>If true, the full URI path within the context is used for the exec command, otherwise a search is done for a partial URL that matches an exec Command</dd>
   * <dt>ignoreExitState</dt>
   * <dd>If true then do not act on a non-zero exec exit status")</dd>
   * </dl>
   */
  public class CGI extends HttpServlet
  {
      private static final long serialVersionUID = -6182088932884791074L;
  
      private static final Logger LOG = Log.getLogger(CGI.class);
  
      private boolean _ok;
      private File _docRoot;
      private boolean _cgiBinProvided;
      private String _path;
      private String _cmdPrefix;
      private boolean _useFullPath;
      private EnvList _env;
      private boolean _ignoreExitState;
      private boolean _relative;
  
      @Override
      public void init() throws ServletException
      {
          _env = new EnvList();
          _cmdPrefix = getInitParameter("commandPrefix");
          _useFullPath = Boolean.parseBoolean(getInitParameter("useFullPath"));
          _relative = Boolean.parseBoolean(getInitParameter("cgibinResourceBaseIsRelative"));
  
          String tmp = getInitParameter("cgibinResourceBase");
          if (tmp != null)
              _cgiBinProvided = true;
          else
          {
             tmp = getInitParameter("resourceBase");
             if (tmp != null)
                 _cgiBinProvided = true;
             else
                 tmp = getServletContext().getRealPath("/");
         }
 
         if (_relative && _cgiBinProvided)
         {
             tmp = getServletContext().getRealPath(tmp);
         }
 
         if (tmp == null)
         {
             LOG.warn("CGI: no CGI bin !");
             return;
         }
 
         File dir = new File(tmp);
         if (!dir.exists())
         {
             LOG.warn("CGI: CGI bin does not exist - " + dir);
             return;
         }
 
         if (!dir.canRead())
         {
             LOG.warn("CGI: CGI bin is not readable - " + dir);
             return;
         }
 
         if (!dir.isDirectory())
         {
             LOG.warn("CGI: CGI bin is not a directory - " + dir);
             return;
         }
 
         try
         {
             _docRoot = dir.getCanonicalFile();
         }
         catch (IOException e)
         {
             LOG.warn("CGI: CGI bin failed - " + dir, e);
             return;
         }
 
         _path = getInitParameter("Path");
         if (_path != null)
             _env.set("PATH", _path);
 
         _ignoreExitState = "true".equalsIgnoreCase(getInitParameter("ignoreExitState"));
         Enumeration<String> e = getInitParameterNames();
         while (e.hasMoreElements())
         {
             String n = e.nextElement();
             if (n != null && n.startsWith("ENV_"))
                 _env.set(n.substring(4), getInitParameter(n));
         }
         if (!_env.envMap.containsKey("SystemRoot"))
         {
             String os = System.getProperty("os.name");
             if (os != null && os.toLowerCase(Locale.ENGLISH).contains("windows"))
             {
                 _env.set("SystemRoot", "C:\\WINDOWS");
             }
         }
 
         _ok = true;
     }
 
     @Override
     public void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException
     {
         if (!_ok)
         {
             res.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
             return;
         }
 
         if (LOG.isDebugEnabled())
         {
             LOG.debug("CGI: ContextPath : " + req.getContextPath());
             LOG.debug("CGI: ServletPath : " + req.getServletPath());
             LOG.debug("CGI: PathInfo    : " + req.getPathInfo());
             LOG.debug("CGI: _docRoot    : " + _docRoot);
             LOG.debug("CGI: _path       : " + _path);
             LOG.debug("CGI: _ignoreExitState: " + _ignoreExitState);
         }
 
         // pathInContext may actually comprises scriptName/pathInfo...We will
         // walk backwards up it until we find the script - the rest must
         // be the pathInfo;
         String pathInContext = (_relative ? "" : StringUtil.nonNull(req.getServletPath())) + StringUtil.nonNull(req.getPathInfo());
         File execCmd = new File(_docRoot, pathInContext);
         String pathInfo = pathInContext;
 
         if (!_useFullPath)
         {
             String path = pathInContext;
             String info = "";
 
             // Search docroot for a matching execCmd
             while ((path.endsWith("/") || !execCmd.exists()) && path.length() >= 0)
             {
                 int index = path.lastIndexOf('/');
                 path = path.substring(0, index);
                 info = pathInContext.substring(index, pathInContext.length());
                 execCmd = new File(_docRoot, path);
             }
 
             if (path.length() == 0 || !execCmd.exists() || execCmd.isDirectory() || !execCmd.getCanonicalPath().equals(execCmd.getAbsolutePath()))
             {
                 res.sendError(404);
             }
 
             pathInfo = info;
         }
         exec(execCmd, pathInfo, req, res);
     }
 
     /**
      * executes the CGI process
      *
      * @param command  the command to execute, this command is prefixed by
      *                 the context parameter "commandPrefix".
      * @param pathInfo The PATH_INFO to process,
      *                 see http://docs.oracle.com/javaee/6/api/javax/servlet/http/HttpServletRequest.html#getPathInfo%28%29. Cannot be null
      * @param req the HTTP request
      * @param res the HTTP response
      * @throws IOException if the execution of the CGI process throws
      */
     private void exec(File command, String pathInfo, HttpServletRequest req, HttpServletResponse res) throws IOException
     {
         assert req != null;
         assert res != null;
         assert pathInfo != null;
         assert command != null;
 
         if (LOG.isDebugEnabled())
         {
             LOG.debug("CGI: script is " + command);
             LOG.debug("CGI: pathInfo is " + pathInfo);
         }
 
         String bodyFormEncoded = null;
         if ((HttpMethod.POST.is(req.getMethod()) || HttpMethod.PUT.is(req.getMethod())) && "application/x-www-form-urlencoded".equals(req.getContentType()))
         {
             MultiMap<String> parameterMap = new MultiMap<>();
             Enumeration<String> names = req.getParameterNames();
             while (names.hasMoreElements())
             {
                 String parameterName = names.nextElement();
                 parameterMap.addValues(parameterName, req.getParameterValues(parameterName));
             }
             bodyFormEncoded = UrlEncoded.encode(parameterMap, Charset.forName(req.getCharacterEncoding()), true);
         }
 
         EnvList env = new EnvList(_env);
         // these ones are from "The WWW Common Gateway Interface Version 1.1"
         // look at :
         // http://Web.Golux.Com/coar/cgi/draft-coar-cgi-v11-03-clean.html#6.1.1
         env.set("AUTH_TYPE", req.getAuthType());
 
         int contentLen = req.getContentLength();
         if (contentLen < 0)
             contentLen = 0;
         if (bodyFormEncoded != null)
         {
             env.set("CONTENT_LENGTH", Integer.toString(bodyFormEncoded.length()));
         }
         else
         {
             env.set("CONTENT_LENGTH", Integer.toString(contentLen));
         }
         env.set("CONTENT_TYPE", req.getContentType());
         env.set("GATEWAY_INTERFACE", "CGI/1.1");
         if (pathInfo.length() > 0)
         {
             env.set("PATH_INFO", pathInfo);
         }
 
         String pathTranslated = req.getPathTranslated();
         if ((pathTranslated == null) || (pathTranslated.length() == 0))
             pathTranslated = pathInfo;
         env.set("PATH_TRANSLATED", pathTranslated);
         env.set("QUERY_STRING", req.getQueryString());
         env.set("REMOTE_ADDR", req.getRemoteAddr());
         env.set("REMOTE_HOST", req.getRemoteHost());
 
         // The identity information reported about the connection by a
         // RFC 1413 [11] request to the remote agent, if
         // available. Servers MAY choose not to support this feature, or
         // not to request the data for efficiency reasons.
         // "REMOTE_IDENT" => "NYI"
         env.set("REMOTE_USER", req.getRemoteUser());
         env.set("REQUEST_METHOD", req.getMethod());
 
         String scriptPath;
         String scriptName;
         // use docRoot for scriptPath, too
         if (_cgiBinProvided)
         {
             scriptPath = command.getAbsolutePath();
             scriptName = scriptPath.substring(_docRoot.getAbsolutePath().length());
         }
         else
         {
             String requestURI = req.getRequestURI();
             scriptName = requestURI.substring(0, requestURI.length() - pathInfo.length());
             scriptPath = getServletContext().getRealPath(scriptName);
         }
         env.set("SCRIPT_FILENAME", scriptPath);
         env.set("SCRIPT_NAME", scriptName);
 
         env.set("SERVER_NAME", req.getServerName());
         env.set("SERVER_PORT", Integer.toString(req.getServerPort()));
         env.set("SERVER_PROTOCOL", req.getProtocol());
         env.set("SERVER_SOFTWARE", getServletContext().getServerInfo());
 
         Enumeration<String> enm = req.getHeaderNames();
         while (enm.hasMoreElements())
         {
             String name = enm.nextElement();
             if (name.equalsIgnoreCase("Proxy"))
                 continue;
             String value = req.getHeader(name);
             env.set("HTTP_" + name.toUpperCase(Locale.ENGLISH).replace('-', '_'), value);
         }
 
         // these extra ones were from printenv on www.dev.nomura.co.uk
         env.set("HTTPS", (req.isSecure() ? "ON" : "OFF"));
         // "DOCUMENT_ROOT" => root + "/docs",
         // "SERVER_URL" => "NYI - http://us0245",
         // "TZ" => System.getProperty("user.timezone"),
 
         // are we meant to decode args here? or does the script get them
         // via PATH_INFO? if we are, they should be decoded and passed
         // into exec here...
         String absolutePath = command.getAbsolutePath();
         String execCmd = absolutePath;
 
         // escape the execCommand
         if (execCmd.length() > 0 && execCmd.charAt(0) != '"' && execCmd.contains(" "))
             execCmd = "\"" + execCmd + "\"";
 
         if (_cmdPrefix != null)
             execCmd = _cmdPrefix + " " + execCmd;
 
         LOG.debug("Environment: " + env.getExportString());
         LOG.debug("Command: " + execCmd);
 
         final Process p = Runtime.getRuntime().exec(execCmd, env.getEnvArray(), _docRoot);
 
         // hook processes input to browser's output (async)
         if (bodyFormEncoded != null)
             writeProcessInput(p, bodyFormEncoded);
         else if (contentLen > 0)
             writeProcessInput(p, req.getInputStream(), contentLen);
 
         // hook processes output to browser's input (sync)
         // if browser closes stream, we should detect it and kill process...
         OutputStream os = null;
         AsyncContext async = req.startAsync();
         try
         {
             async.start(new Runnable()
             {
                 @Override
                 public void run()
                 {
                     try
                     {
                         IO.copy(p.getErrorStream(), System.err);
                     }
                     catch (IOException e)
                     {
                         LOG.warn(e);
                     }
                 }
             });
 
             // read any headers off the top of our input stream
             // NOTE: Multiline header items not supported!
             String line = null;
             InputStream inFromCgi = p.getInputStream();
 
             // br=new BufferedReader(new InputStreamReader(inFromCgi));
             // while ((line=br.readLine())!=null)
             while ((line = getTextLineFromStream(inFromCgi)).length() > 0)
             {
                 if (!line.startsWith("HTTP"))
                 {
                     int k = line.indexOf(':');
                     if (k > 0)
                     {
                         String key = line.substring(0, k).trim();
                         String value = line.substring(k + 1).trim();
                         if ("Location".equals(key))
                         {
                             res.sendRedirect(res.encodeRedirectURL(value));
                         }
                         else if ("Status".equals(key))
                         {
                             String[] token = value.split(" ");
                             int status = Integer.parseInt(token[0]);
                             res.setStatus(status);
                         }
                         else
                         {
                             // add remaining header items to our response header
                             res.addHeader(key, value);
                         }
                     }
                 }
             }
             // copy cgi content to response stream...
             os = res.getOutputStream();
             IO.copy(inFromCgi, os);
             p.waitFor();
 
             if (!_ignoreExitState)
             {
                 int exitValue = p.exitValue();
                 if (0 != exitValue)
                 {
                     LOG.warn("Non-zero exit status (" + exitValue + ") from CGI program: " + absolutePath);
                     if (!res.isCommitted())
                         res.sendError(500, "Failed to exec CGI");
                 }
             }
         }
         catch (IOException e)
         {
             // browser has probably closed its input stream - we
             // terminate and clean up...
             LOG.debug("CGI: Client closed connection!", e);
         }
         catch (InterruptedException ie)
         {
             LOG.debug("CGI: interrupted!");
         }
         finally
         {
             if (os != null)
             {
                 try
                 {
                     os.close();
                 }
                 catch (Exception e)
                 {
                     LOG.debug(e);
                 }
             }
             p.destroy();
             // LOG.debug("CGI: terminated!");
             async.complete();
         }
     }
 
     private static void writeProcessInput(final Process p, final String input)
     {
         new Thread(new Runnable()
         {
             @Override
             public void run()
             {
                 try
                 {
                     try (Writer outToCgi = new OutputStreamWriter(p.getOutputStream()))
                     {
                         outToCgi.write(input);
                     }
                 }
                 catch (IOException e)
                 {
                     LOG.debug(e);
                 }
             }
         }).start();
     }
 
     private static void writeProcessInput(final Process p, final InputStream input, final int len)
     {
         if (len <= 0) return;
 
         new Thread(new Runnable()
         {
             @Override
             public void run()
             {
                 try
                 {
                     OutputStream outToCgi = p.getOutputStream();
                     IO.copy(input, outToCgi, len);
                     outToCgi.close();
                 }
                 catch (IOException e)
                 {
                     LOG.debug(e);
                 }
             }
         }).start();
     }
 
     /**
      * Utility method to get a line of text from the input stream.
      *
      * @param is the input stream
      * @return the line of text
      * @throws IOException if reading from the input stream throws
      */
     private static String getTextLineFromStream(InputStream is) throws IOException
     {
         StringBuilder buffer = new StringBuilder();
         int b;
 
         while ((b = is.read()) != -1 && b != '\n')
         {
             buffer.append((char)b);
         }
         return buffer.toString().trim();
     }
 
     /**
      * private utility class that manages the Environment passed to exec.
      */
     private static class EnvList
     {
         private Map<String, String> envMap;
 
         EnvList()
         {
             envMap = new HashMap<>();
         }
 
         EnvList(EnvList l)
         {
             envMap = new HashMap<>(l.envMap);
         }
 
         /**
          * Set a name/value pair, null values will be treated as an empty String
          *
          * @param name the name
          * @param value the value
          */
         public void set(String name, String value)
         {
             envMap.put(name, name + "=" + StringUtil.nonNull(value));
         }
 
         /** 
          * Get representation suitable for passing to exec. 
          *
          * @return the env map as an array 
          */
         public String[] getEnvArray()
         {
             return envMap.values().toArray(new String[envMap.size()]);
         }
 
         public String getExportString()
         {
             StringBuilder sb = new StringBuilder();
             for (String variable : getEnvArray())
             {
                 sb.append("export \"");
                 sb.append(variable);
                 sb.append("\"; ");
             }
             return sb.toString();
         }
 
         @Override
         public String toString()
         {
             return envMap.toString();
         }
     }
 }