Fix race condition related to watching DGL games.

It's possible for a dgamelaunch game to end and cause rlgwebd to stop watching
it before rlgwebd has started watching it.

Makefile

@@ -23,7 +23,7 @@ install: all
 	mkdir -p ${CHROOT}/var/www
 	cp ${WEBASSETS} ${CHROOT}/var/www
 	cp rlgwebd.service /usr/lib/systemd/system
-	if test ! -f /etc/rlgwebd.conf; cp rlgwebd.conf /etc; fi
+	if test ! -f /etc/rlgwebd.conf; then cp rlgwebd.conf /etc; fi
 
 # Libraries are not removed.  Something else might be using them.
 uninstall:

README.txt

@@ -5,12 +5,11 @@ browser.  It is intended to be compatible with dgamelaunch.
 
 Node
 ---
-RLGWebD currently works with Node v0.10.
+RLGWebD is currently being updated to work with Node v10.x.
 
-It requires the 'posix', 'pty.js', and 'websocket' modules.  Currently,
-it expects them to be installed in the global location, which is 
-"/usr/lib/node_modules".  It is planned to eventually use a different
-location so that npm will not need to run as root.
+It requires the 'posix', 'node-pty', and 'websocket' modules.  Currently,
+it expects them to be installed in "/var/local/lib/node_modules".  It
+is not recommended to run npm as root when installing the modules.
 
 init
 ---
@@ -22,14 +21,11 @@ a proper initscript, but it could form the basis of one.
 
 Configuration
 ---
-You can set some options by changing some variables in the first few
-lines of the rlgwebd script:
+A configuration file is installed at /etc/rlgwebd.conf.  It contains a
+list of options.
 
-Option		Variable	Default
-
-Chroot path	chrootDir	/var/dgl
-Username	dropToUser	rodney
-Server port	httpPort	8080
+If the domain_name option and the SSL-related options are set, rlgwebd
+will use HTTPS instead of insecure HTTP.
 
 If you change the chroot location, change it in the first line of the 
 Makefile too.
@@ -59,6 +55,7 @@ Running "make install" will:
   Copy the C programs and the libraries they need into the chroot
   Install the main RLGWebD script in /usr/local/bin
   Place the systemd unit file in the proper directory
+  Copy a configuration file into /etc
 
 If you don't use systemd, or want to change the installation locations,
 you will have to edit the Makefile.

initscript

@@ -1,8 +1,8 @@
 #!/bin/sh
 
-NODE_PATH=/usr/lib/node_modules
+NODE_PATH=/var/local/lib/node_modules
 LOGFILE=/var/log/rlgwebd.log
-CTLSOCKET=/var/run/rlgwebd.sock
+CTLSOCKET=/var/run/rlgwebd/rlgwebd.sock
 RLGWEBDJS=/usr/local/bin/rlgwebd
 
 export NODE_PATH

rlgwebd

@@ -1,35 +1,38 @@
 #!/usr/bin/env node
 
-var http = require('http');
-var https = require('https');
-var net = require('net');
-var url = require('url');
-var path = require('path');
-var fs = require('fs');
-var events = require('events');
-var child_process = require('child_process');
+const http = require('http');
+const https = require('https');
+const net = require('net');
+const url = require('url');
+const path = require('path');
+const fs = require('fs');
+const events = require('events');
+const child_process = require('child_process');
 // Dependencies
-var posix = require("posix");
-var pty = require("pty.js");
-var WebSocketServer = require("websocket").server;
+const posix = require("posix");
+const pty = require("node-pty");
+const WebSocketServer = require("websocket").server;
+
+const errorcodes = [ "Generic Error", "Not logged in", "Invalid data", 
+        "Login failed", "Already playing", "Game launch failed",
+        "Server shutting down", "Game not in progress" ];
 
 /* Default options */
 var rlgwebd_options = { 
-  control_socket: "/var/run/rlgwebd.sock",
-  http_port: 8080,
-  https_port: 8081,
+  control_socket: "/var/run/rlgwebd/rlgwebd.sock",
+  port: 8080,
   chrootDir: "/var/dgl/",
   username: "rodney",
   static_root: "/var/www/"
 };
 
 /* Read configuration from a file */
-var config_file = "/etc/rlgwebd.conf";
+const config_file = "/etc/rlgwebd.conf";
 var config_lines = read_or_die(config_file, "Configuration file").toString().split('\n');
 
-for (var i = 0; i < config_lines.length; i++) {
-  if (config_lines[i].length > 0 && config_lines[i][0] != '#') {
-    var config_fields = config_lines[i].split('=');
+for (let conf_line of config_lines) {
+  if (conf_line.length > 0 && conf_line[0] != '#') {
+    var config_fields = conf_line.split('=');
     if (config_fields.length < 2)
       continue;
     var option_name = config_fields[0].trim();
@@ -44,13 +47,13 @@ if ("domain_name" in rlgwebd_options && "keyfile" in rlgwebd_options &&
     "certfile" in rlgwebd_options)
   rlgwebd_options["use_https"] = true;
 
-var clearbufs = [
-  new Buffer([27, 91, 72, 27, 91, 50, 74]), // xterm: CSI H CSI 2J
-  new Buffer([27, 91, 72, 27, 91, 74]) // screen: CSI H CSI J
+const clearbufs = [
+  Buffer.from([27, 91, 72, 27, 91, 50, 74]), // xterm: CSI H CSI 2J
+  Buffer.from([27, 91, 72, 27, 91, 74]) // screen: CSI H CSI J
 ];
 
 /* Data on the games available. */
-var games = {
+const games = {
   "rogue3": {
     "name": "Rogue V3",
     "uname": "rogue3",
@@ -110,7 +113,7 @@ function BaseGame() {
   this.watchers = [];
   /* replaybuf holds the output since the last screen clear, so watchers can
    * begin with a complete screen. replaylen is the number of bytes stored. */
-  this.replaybuf = new Buffer(1024);
+  this.replaybuf = Buffer.alloc(1024);
   this.replaylen = 0;
   /* Time of last activity. */
   this.lasttime = new Date();
@@ -126,12 +129,12 @@ BaseGame.prototype.tag = function () {
 BaseGame.prototype.framepush = function(chunk) {
   /* If this chunk resets the screen, discard what preceded it. */
   if (isclear(chunk)) {
-    this.replaybuf = new Buffer(1024);
+    this.replaybuf = Buffer.alloc(1024);
     this.replaylen = 0;
   }
   /* Make sure there's space. */
   while (this.replaybuf.length < chunk.length + this.replaylen) {
-    var nbuf = new Buffer(this.replaybuf.length * 2);
+    var nbuf = Buffer.alloc(this.replaybuf.length * 2);
     this.replaybuf.copy(nbuf, 0, 0, this.replaylen);
     this.replaybuf = nbuf;
     if (this.replaybuf.length > 65536) {
@@ -211,7 +214,9 @@ function TermSession(gname, pname, wsReq) {
   var progressdir = path.join("/dgldir/inprogress", this.gname);
   this.lock = path.join(progressdir, this.pname + ":node:" + ts + ".ttyrec");
   var lmsg = this.term.pid.toString() + '\n' + this.h + '\n' + this.w + '\n'; 
-  fs.writeFile(this.lock, lmsg, "utf8"); 
+  fs.writeFile(this.lock, lmsg, "utf8", function (err) {
+    if (err) tslog("Locking failed: %s", err);
+  }); 
   var ttyrec = path.join("/dgldir/ttyrec", this.pname, this.gname, 
                ts + ".ttyrec");
   this.record = fs.createWriteStream(ttyrec, { mode: 0664 });
@@ -239,8 +244,8 @@ TermSession.prototype = new BaseGame();
 /* Currently this also sends to the player and any watchers. */
 TermSession.prototype.write_ttyrec = function (datastr) {
   this.lasttime = new Date();
-  var buf = new Buffer(datastr);
-  var chunk = new Buffer(buf.length + 12);
+  var buf = Buffer.from(datastr);
+  var chunk = Buffer.alloc(buf.length + 12);
   /* TTYREC headers */
   chunk.writeUInt32LE(Math.floor(this.lasttime.getTime() / 1000), 0);
   chunk.writeUInt32LE(1000 * (this.lasttime.getTime() % 1000), 4);
@@ -274,7 +279,7 @@ TermSession.prototype.input_msg = function (message) {
     if (hexstr.length % 2 != 0) {
       hexstr = hexstr.slice(0, -1);
     }
-    var keybuf = new Buffer(hexstr, "hex");
+    var keybuf = Buffer.from(hexstr, "hex");
     this.write(keybuf);
   }
 };
@@ -287,7 +292,9 @@ TermSession.prototype.close = function () {
 
 TermSession.prototype.destroy = function () {
   var tag = this.tag();
-  fs.unlink(this.lock);
+  fs.unlink(this.lock, function (err) {
+    if (err) tslog("Lock removal failed: %s", err);
+  });
   this.record.end();
   var watchsocks = this.watchers;
   this.watchers = [];
@@ -356,7 +363,7 @@ DglSession.prototype.startchunk = function () {
   if (this.reading)
     return;
   this.reading = true;
-  var header = new Buffer(12);
+  var header = Buffer.alloc(12);
   fs.read(this.fd, header, 0, 12, this.rpos, this.datachunk.bind(this));
 };
 
@@ -377,7 +384,7 @@ DglSession.prototype.datachunk = function (err, n, buf) {
     // Something is probably wrong...
     tslog("DGL %s: looking for %d bytes", this.tag(), datalen);
   }
-  var databuf = new Buffer(datalen);
+  var databuf = Buffer.alloc(datalen);
   fs.read(this.fd, databuf, 0, datalen, this.rpos, this.handledata.bind(this));
 };
 
@@ -394,9 +401,9 @@ DglSession.prototype.handledata = function (err, n, buf) {
   /* Process the data */
   this.framepush(buf);
   var wmsg = JSON.stringify({"t": "d", "d": buf.toString("hex")});
-  for (var i = 0; i < this.watchers.length; i++) {
-    if (this.watchers[i].connected)
-      this.watchers[i].sendUTF(wmsg);
+  for (let watcher of this.watchers) {
+    if (watcher.connected)
+      watcher.sendUTF(wmsg);
   }
   this.emit("data", buf);
   /* Recurse. */
@@ -411,6 +418,8 @@ DglSession.prototype.notifier = function (ev, finame) {
 };
 
 DglSession.prototype.close = function () {
+  /* The watcher might not be open yet. */
+  if ("recwatcher" in this)
     this.recwatcher.close();
   /* Ensure all data is handled before quitting. */
   this.startchunk();
@@ -420,7 +429,9 @@ DglSession.prototype.close = function () {
     if (connlist[i].connected)
       connlist[i].close();
   }
-  fs.close(this.fd);
+  fs.close(this.fd, function (err) {
+    if (err) tslog("PTY close failed: %s", err);
+  });
   this.emit("close");
   gamemux.emit('end', this.gname, this.pname);
   tslog("DGL %s: closed", this.tag());
@@ -487,8 +498,11 @@ function checksaved(user, game, callback, args) {
   var savedirc = game.uname + "save";
   var basename = String(pwent.uid) + "-" + user + game.suffix;
   var savefile = path.join("/var/games/roguelike", savedirc, basename);
-  fs.exists(savefile, function (exist) {
-    args.unshift(exist);
+  fs.access(savefile, function (err) {
+    if (err)
+      args.unshift(false);
+    else
+      args.unshift(true);
     callback.apply(null, args);
   });
 }
@@ -567,8 +581,8 @@ function bufncmp(buf1, buf2, n) {
 }
 
 function isclear(buf) {
-  for (var i = 0; i < clearbufs.length; i++) {
-    if (bufncmp(buf, clearbufs[i], clearbufs[i].length))
+  for (let clearer of clearbufs) {
+    if (bufncmp(buf, clearer, clearer.length))
       return true;
   }
   return false;
@@ -688,10 +702,15 @@ function login(req, res, formdata) {
 function regsetup(username) {
   function regsetup_l2(err) {
     for (var g in games) {
-      fs.mkdir(path.join("/dgldir/ttyrec", username, games[g].uname), 0755);
+      fs.mkdir(path.join("/dgldir/ttyrec", username, games[g].uname), 0755,
+        function (err) {
+          if (err) tslog("ttyrec mkdir failed: %s", err);
+      });
     }
   }
-  fs.mkdir(path.join("/dgldir/userdata", username), 0755);
+  fs.mkdir(path.join("/dgldir/userdata", username), 0755, function (err) {
+    if (err) tslog("Userdata mkdir failed: %s", err);
+  });
   fs.mkdir(path.join("/dgldir/ttyrec/", username), 0755, regsetup_l2);
 }
 
@@ -779,7 +798,9 @@ function stopgame(res, formdata) {
         if (err.code == "ESRCH") {
           var nodere = RegExp("^" + pname + ":node:");
           if (fname.match(nodere)) {
-            fs.unlink(fullfile);
+            fs.unlink(fullfile, function (err) {
+              if (err) tslog("Stale lock removal failed: %s", err);
+            });
           }
         }
       }
@@ -832,6 +853,8 @@ function startProgressWatcher() {
 }
 
 function serveStatic(req, res, fname) {
+  if (fname[0] !== "/")
+    fname = "/" + fname;
   var nname = path.normalize(fname);
   if (nname == "" || nname == "/")
     nname = "index.html";
@@ -839,9 +862,9 @@ function serveStatic(req, res, fname) {
     path.join(nname, "index.html"); /* it was a directory */
   var realname = path.join(rlgwebd_options.static_root, nname);
   var extension = path.extname(realname);
-  fs.exists(realname, function (exists) {
+  fs.access(realname, function (access_err) {
     var resheaders = {};
-    if (!exists || !extension || extension == ".html")
+    if (access_err || !extension || extension == ".html")
       resheaders["Content-Type"] = "text/html; charset=utf-8";
     else if (extension == ".png")
       resheaders["Content-Type"] = "image/png";
@@ -853,7 +876,7 @@ function serveStatic(req, res, fname) {
       resheaders["Content-Type"] = "image/svg+xml";
     else
       resheaders["Content-Type"] = "application/octet-stream";
-    if (exists) {
+    if (!access_err) {
       fs.readFile(realname, function (error, data) {
         if (error) {
           res.writeHead(500, {});
@@ -1024,10 +1047,6 @@ function setuinfo(req, res, postdata) {
   }
 }
 
-var errorcodes = [ "Generic Error", "Not logged in", "Invalid data", 
-        "Login failed", "Already playing", "Game launch failed",
-        "Server shutting down", "Game not in progress" ];
-
 function sendError(res, ecode, msg, box) {
   res.writeHead(200, { "Content-Type": "application/json" });
   var edict = {"t": "E"};
@@ -1264,6 +1283,21 @@ if (rlgwebd_options.use_https) {
     tls_options.ca = read_or_die(rlgwebd_options.cafile, "CA file");
 };
 
+/* Make sure the socket directory is secure. */
+var socket_dir = path.dirname(rlgwebd_options.control_socket);
+try {
+  fs.mkdirSync(socket_dir, 0o700);
+}
+catch (err) {
+  if (err.code == "EEXIST") {
+    fs.chownSync(socket_dir, 0, 0);
+    fs.chmodSync(socket_dir, 0o700);
+  }
+  else {
+    throw err;
+  }
+}
+
 /* Open the control socket before chrooting where it can't be found */
 var ctlServer = net.createServer(function (sock) {
   sock.on('data', consoleHandler);
@@ -1288,19 +1322,21 @@ ctlServer.listen(rlgwebd_options.control_socket, function () {
     tslog("Could not drop permissions: %s", err);
     process.exit(1);
   }
+  if (rlgwebd_options.use_https) {
+    httpServer = https.createServer(tls_options, webHandler);
+    httpServer.listen(rlgwebd_options.port);
+    tslog('rlgwebd running on port %d (TLS)', rlgwebd_options.port); 
+    wsServer = new WebSocketServer({"httpServer": httpServer});
+    wsServer.on("request", wsHandler);
+    tslog('Secure WebSockets are online'); 
+  }
+  else {
     httpServer = http.createServer(webHandler);
-  httpServer.listen(rlgwebd_options.http_port);
-  tslog('rlgwebd running on port %d', rlgwebd_options.http_port); 
+    httpServer.listen(rlgwebd_options.port);
+    tslog('rlgwebd running on port %d', rlgwebd_options.port); 
     wsServer = new WebSocketServer({"httpServer": httpServer});
     wsServer.on("request", wsHandler);
     tslog('WebSockets are online'); 
-  if (rlgwebd_options.use_https) {
-    var httpsServer = https.createServer(tls_options, webHandler);
-    httpsServer.listen(rlgwebd_options.https_port);
-    tslog('TLS running on port %d', rlgwebd_options.https_port); 
-    var wssServer = new WebSocketServer({"httpServer": httpsServer});
-    wssServer.on("request", wsHandler);
-    tslog('Secure WebSockets are online'); 
   }
   progressWatcher = startProgressWatcher();
   setInterval(pushStatus, 40000);

rlgwebd-stop

@@ -1,22 +1,19 @@
 #!/usr/bin/env node
 
 var net = require('net');
-var domain = require('domain');
-var sockpath = "/var/run/rlgwebd.sock";
+var sockpath = "/var/run/rlgwebd/rlgwebd.sock";
 
-var dom = domain.create();
+var sock = new net.Socket();
 
-dom.on('error', function (err) {
+sock.on('error', function (err) {
   console.log("Cannot connect to " + sockpath + ", rlgwebd already stopped.");
   process.exit(0);
 });
 
-dom.run(function () {
-  var sock = net.connect(sockpath, function () {
-    sock.on('close', function () {
+sock.connect(sockpath, function () {
+  sock.on('close', function (had_error) {
     if (process.argv[2] == "debug")
       console.log("Control socket closed");
   });
   sock.write("quit\n");
 });
-});

rlgwebd.conf

@@ -3,11 +3,9 @@
 
 # These values are set by default:
 # Location of the socket for start/stop commands
-#control_socket = /var/run/rlgwebd.sock
+#control_socket = /var/run/rlgwebd/rlgwebd.sock
 # Port number to bind
-#http_port = 8080
-# Port number for HTTPS
-#https_port = 8081
+#port = 8080
 # Path to the dgamelaunch installation to chroot into
 # If you change this, change the Makefile too
 #chrootDir = /var/dgl/

rlgwebd.service

@@ -4,7 +4,7 @@ After=network.target syslog.target
 
 [Service]
 Type=simple
-Environment=NODE_PATH=/usr/lib/node_modules
+Environment=NODE_PATH=/var/local/lib/node_modules
 ExecStart=/usr/local/bin/rlgwebd
 ExecStop=/usr/local/bin/rlgwebd-stop
 Restart=on-failure

termemu.js

@@ -71,6 +71,7 @@ var termemu = {
   scrB: 0, // init() will set this properly
   c: null,   // Contains cursor position and text attributes
   offedge: false, // Going off the edge doesn't mean adding a new line
+  lastcode: 0, // Last printed character
   clearAttrs: function () {
     /* Make sure to reset ALL attribute properties and NOTHING else. */
     this.c.bold = false;
@@ -460,6 +461,7 @@ var termemu = {
       this.screen.replaceChild(this.makeRow(), this.screen.childNodes[i]);
     }
     this.flipCursor(); // make it appear in the new row
+    this.lastcode = 0;
     return;
   },
   write: function (codes) {
@@ -531,6 +533,10 @@ var termemu = {
             debug(1, "Unrecognized sequence ESC " + codes[i].toString(16));
             this.comseq = [];
           }
+          if (this.comseq.length == 0) {
+            // A complete sequence was processed, clear lastcode.
+            this.lastcode = 0;
+          }
         }
         else if (this.comseq.length == 2 && this.comseq[0] == 27) {
           /* An ESC C N sequence.  Not implemented. Doesn't check validity 
@@ -555,6 +561,7 @@ var termemu = {
                   String.fromCharCode(this.comseq[1]) + " 0x" + 
                   codes[i].toString(16));
           this.comseq = [];
+          this.lastcode = 0;
         }
         else if (this.comseq[0] == 157) {
           /* Commands beginning with OSC */
@@ -566,6 +573,7 @@ var termemu = {
             debug(0, "Got " + (this.comseq.length - 1) + "-byte OSC sequence");
             this.oscProcess();
             this.comseq = [];
+            this.lastcode = 0;
           }
           else
             this.comseq.push(codes[i]);
@@ -582,15 +590,17 @@ var termemu = {
               /* Chars in csiPre can only occur right after the CSI */
               debug(1, "Invalid CSI sequence: misplaced prefix");
               this.comseq = [];
+              this.lastcode = 0;
             }
             else
               this.comseq.push(codes[i]);
           }
           else if (csiPost.indexOf(this.comseq[this.comseq.length - 1]) >= 0 && 
                    !csiFinal(codes[i])) {
-            /* Chars is csiPost must come right before the final char */
+            /* Chars in csiPost must come right before the final char */
             debug(1, "Invalid CSI sequence: misplaced postfix");
             this.comseq = [];
+            this.lastcode = 0;
           }
           else if ((codes[i] >= 48 && codes[i] <= 57) || codes[i] == 59 || 
                     csiPost.indexOf(codes[i]) >= 0) {
@@ -605,30 +615,49 @@ var termemu = {
           else {
             debug(1, "Invalid CSI sequence: unknown code " + codes[i].toString(16));
             this.comseq = [];
+            this.lastcode = 0;
           }
         }
         else {
           debug(1, "Unknown sequence with " + this.comseq[0].toString(16));
           this.comseq = [];
+          this.lastcode = 0;
         }
-        continue;
       }
-      /* Treat it as a single character. */
-      if (codes[i] == 5) {
+      else if ((codes[i] >= 32 && codes[i] < 127) || codes[i] >= 160) {
+        /* If it's ASCII, it's printable; take a risk on anything higher */
+        if ((this.c.cset == "0") && (codes[i] in decChars)) {
+          // DEC special character set
+          this.lastcode = decChars[codes[i]];
+        }
+        else {
+          this.lastcode = codes[i];
+        }
+        this.placechar(String.fromCharCode(this.lastcode));
+      }
+      else {
+        /* Treat it as a single control character. */
+        this.singleCtl(codes[i]);
+      }
+    }
+    return;
+  },
+  singleCtl: function (ctlcode) {
+    if (ctlcode == 5) {
       sendback("06");
     }
-      else if (codes[i] == 7) {
+    else if (ctlcode == 7) {
       /* bell */
       bell(true);
     }
-      else if (codes[i] == 8) {
+    else if (ctlcode == 8) {
       /* backspace */
       if (this.offedge)
         this.offedge = false;
       else if (this.c.x > 0)
         this.cmove(null, this.c.x - 1);
     }
-      else if (codes[i] == 9) {
+    else if (ctlcode == 9) {
       /* tab */
       var xnew;
       if (this.c.x < this.w - 1) {
@@ -641,55 +670,47 @@ var termemu = {
         this.offedge = true;
       }
     }
-      else if (codes[i] >= 10 && codes[i] <= 12) {
+    else if (ctlcode >= 10 && ctlcode <= 12) {
       /* newline, vertical tab, form feed */
       if (this.offedge)
         this.newline(true);
       else
         this.newline(false);
     }
-      else if (codes[i] == 13) {
+    else if (ctlcode == 13) {
       /* carriage return \r */
       this.cmove(null, 0);
     }
-      else if (codes[i] == 14) {
+    else if (ctlcode == 14) {
       /* shift out */
       // Currently assuming that G1 is DEC Special & Line Drawing
       this.c.cset = "0";
       debug(0, "Using DEC graphics charset.");
     }
-      else if (codes[i] == 15) {
+    else if (ctlcode == 15) {
       /* shift in */
       // Currently assuming that G0 is ASCII
       this.c.cset = "B";
       debug(0, "Using ASCII charset.");
     }
-      else if (codes[i] == 27) {
+    else if (ctlcode == 27) {
       /* escape */
-        this.comseq.push(codes[i]);
-      }
-      else if (codes[i] < 32 || (codes[i] >= 127 && codes[i] < 160)) {
-        /* Some kind of control character. */
-        debug(1, "Unprintable character 0x" + codes[i].toString(16));
+      this.comseq.push(27);
     }
     else {
-        /* If it's ASCII, it's printable; take a risk on anything higher */
-        if ((this.c.cset == "0") && (codes[i] in decChars)) {
-          // DEC special character set
-          this.placechar(String.fromCharCode(decChars[codes[i]]));
+      debug(1, "Unprintable character 0x" + ctlcode.toString(16));
     }
-        else {
-          this.placechar(String.fromCharCode(codes[i]));
+    if (ctlcode != 27) {
+      // Sequences should preserve lastcode until they are completed
+      this.lastcode = 0;
     }
-      }
-    }
-    return;
   },
   csiProcess: function () {
     /* Processes the CSI sequence in this.comseq */
     var c = this.comseq[this.comseq.length - 1];
     if (this.comseq[0] != 155 || !csiFinal(c))
       return;
+    var printed = false;
     var comstr = "";
     for (var i = 1; i < this.comseq.length; i++)
       comstr += String.fromCharCode(this.comseq[i]);
@@ -698,6 +719,7 @@ var termemu = {
     var matchCSI = comstr.match(reCSI);
     if (!matchCSI) {
       debug(1, "Unrecognized CSI sequence: " + comstr);
+      this.lastcode = 0;
       return;
     }
     var prefix = null;
@@ -725,6 +747,7 @@ var termemu = {
       /* @ - insert spaces at cursor */
       if (prefix || postfix) {
         debug(1, "Invalid CSI @ sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       /* The cursor stays still, but characters move out from under it. */
@@ -745,6 +768,7 @@ var termemu = {
       /* E - next line, F - previous line, G - to column */
       if (prefix || postfix) {
         debug(1, "Invalid CSI sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       /* These may be out of range, but cmove will take care of that. */
@@ -769,6 +793,7 @@ var termemu = {
       var y = 0;
       if (prefix || postfix) {
         debug(1, "Invalid CSI H sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       if (params[0])
@@ -787,6 +812,7 @@ var termemu = {
       var x = this.c.x;
       if (prefix || postfix) {
         debug(1, "Invalid CSI I sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       while (count > 0) {
@@ -808,6 +834,7 @@ var termemu = {
         debug(1, "Warning: CSI ?J not implemented");
       else if (prefix || postfix) {
         debug(1, "Invalid CSI J sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       if (!params[0]) {
@@ -828,6 +855,7 @@ var termemu = {
       }
       else {
         debug(1, "Unimplemented parameter in CSI J sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       for (var nrow = start; nrow <= end; nrow++) {
@@ -855,6 +883,7 @@ var termemu = {
         debug(1, "Warning: CSI ?K not implemented");
       else if (prefix || postfix) {
         debug(1, "Invalid CSI K sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       /* 0 (default): right, 1: left, 2: all.  Include cursor position. */
@@ -885,11 +914,14 @@ var termemu = {
        * M - delete current lines */
       if (prefix || postfix) {
         debug(1, "Invalid CSI sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       /* CSI LM have no effect outside of the scrolling region */
-      if (this.c.y < this.scrT || this.c.y > this.scrB)
+      if (this.c.y < this.scrT || this.c.y > this.scrB) {
+        this.lastcode = 0;
         return;
+      }
       this.flipCursor();
       while (count > 0) {
         var blankrow = this.makeRow();
@@ -915,6 +947,7 @@ var termemu = {
       /* P - delete at active position, causing cells on the right to shift. */
       if (prefix || postfix) {
         debug(1, "Invalid CSI P sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       var cursrow = this.screen.childNodes[this.c.y];
@@ -930,6 +963,7 @@ var termemu = {
       /* S - scroll up, T - scroll down */
       if (prefix || postfix) {
         debug(1, "Invalid CSI sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       if (c == 83)
@@ -941,6 +975,7 @@ var termemu = {
       /* X - erase characters */
       if (prefix || postfix) {
         debug(1, "Invalid CSI sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       var row = this.screen.childNodes[this.c.y];
@@ -954,6 +989,7 @@ var termemu = {
       var x = this.c.x;
       if (prefix || postfix) {
         debug(1, "Invalid CSI Z sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       while (count > 0) {
@@ -970,14 +1006,26 @@ var termemu = {
       /* ` - go to col */
       if (prefix || postfix) {
         debug(1, "Invalid CSI ` sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       this.cmove(null, count - 1);
     }
+    else if (c == 98) {
+      /* b - repeat previous character */
+      if (this.lastcode !== 0) {
+        while (count > 0) {
+          this.placechar(String.fromCharCode(this.lastcode));
+          count--;
+        }
+        printed = true;
+      }
+    }
     else if (c == 99) {
       /* c - query terminal attributes */
       if (prefix !== null) {
         debug(1, "Unimplemented CSI sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       /* "CSI ? 1 ; 2 c" - VT100 */
@@ -987,6 +1035,7 @@ var termemu = {
       /* d - go to row */
       if (prefix || postfix) {
         debug(1, "Invalid CSI d sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       this.cmove(count - 1, null);
@@ -997,6 +1046,7 @@ var termemu = {
       var y = 0;
       if (prefix || postfix) {
         debug(1, "Invalid CSI f sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       if (params[0])
@@ -1009,6 +1059,7 @@ var termemu = {
       /* h - set modes */
       if (prefix != '?') {
         debug(1, "Unimplemented CSI sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       for (var i = 0; i < params.length; i++) {
@@ -1047,6 +1098,7 @@ var termemu = {
         }
         else {
           debug(1, "Unimplemented CSI sequence: " + comstr);
+          this.lastcode = 0;
           return;
         }
       }
@@ -1080,6 +1132,7 @@ var termemu = {
       /* m - character attributes */
       if (prefix !== null) {
         debug(1, "Unimplemented CSI sequence: " + comstr);
+        this.lastcode = 0;
         return;
       }
       if (params.length == 0)
@@ -1133,15 +1186,18 @@ var termemu = {
         t = params[0] - 1;
       if (params[1] && params[1] <= this.h)
         b = params[1] - 1;
-      if (b <= t)
-        return;
+      if (b > t) {
         this.scrT = t;
         this.scrB = b;
         this.cmove(0, 0);
       }
+    }
     else {
       debug(1, "Unimplemented CSI sequence: " + comstr);
     }
+    if (!printed) {
+      this.lastcode = 0;
+    }
     return;
   },
   oscProcess: function () {