CVE-2021-29300: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') (CWE-78)
value: The @ronomon/opened library before 1.5.2 is vulnerable to a command injection vulnerability which would allow a remote attacker to execute commands on the system if the library was used with untrusted input.
CWE description: The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.
CVSS v3 base score: 9.8
Published: 2021-05-24T16:15Z
Repository: https://github.com/ronomon/opened
Language: JavaScript
Files changed: .gitignore, LICENSE, README.md, binding.cc, binding.gyp, index.js, package-lock.json, package.json, test-injection.js, test.js
Commit date: 2021-04-14 19:30:54 +0200
Commit message: Fix command injection vulnerability

@ronomon/opened was vulnerable to a command injection vulnerability
that would allow a remote attacker to execute commands on the system if
the library was used with untrusted input.

The root cause of the problem was line 87 in index.js which took
potential untrusted input as part of a string executed as a command
by `child_process.exec()`. While the arguments were escaped by
@ronomon/opened, an attacker could still bypass this sanitization
because `child_process.exec()` will also interpret the string as a
shell command.

This fix moves to `execFile` to spawn the binary with separate
arguments that will not also be interpreted as shell commands.

Thanks to Fábio Freitas, a security analyst at Checkmarx's CxSCA group,
for discovering and disclosing the vulnerability, providing clear steps
to reproduce and suggestions for mitigation.

Diff: diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b4e05c7
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+.DS_Store
+binding.node
+build
+node_modules
+opened_fixtures
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..c632aff
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2017 Ronomon
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..74702dd
--- /dev/null
+++ b/README.md
@@ -0,0 +1,35 @@
+# opened
+Check if a file is open in another application on Windows, macOS and Linux. Linux requires privileges.
+
+## Installation
+```
+npm install @ronomon/opened
+```
+
+## Windows
+`Opened` uses a native binding on Windows to try and open an existing file with exclusive sharing mode (`dwShareMode`) and detect an `ERROR_SHARING_VIOLATION` error if another application already has an open handle to the file. This will detect any applications with open handles to the file, but not applications which have opened, buffered the file for display, and then closed the handle (i.e. applications which may be showing the file to the user, but which no longer have an open handle to the file).
+
+## Unix
+`Opened` uses `lsof` on macOS and on Linux. On Linux (but not on macOS), `lsof` requires sudo permissions to iterate across open file descriptors for the user, otherwise no files will be detected as open and no permissions error will be returned.
+
+## Usage
+
+```javascript
+var Opened = require('@ronomon/opened');
+var paths = [...];
+Opened.files(paths,
+  function(error, hashTable) {
+    if (error) throw error;
+    paths.forEach(
+      function(path) {
+        console.log(path + ' open=' + hashTable[path]);
+      }
+    );
+  }
+);
+```
+
+## Tests
+```
+node test.js
+```
diff --git a/binding.cc b/binding.cc
new file mode 100644
index 0000000..39719e0
--- /dev/null
+++ b/binding.cc
@@ -0,0 +1,82 @@
+#include <nan.h>
+#if defined(_WIN32)
+#include <io.h>
+#include <windows.h>
+#endif
+
+int open(const char* path) {
+#if defined(_WIN32)
+  int chars = MultiByteToWideChar(CP_UTF8, 0, path, -1, NULL, 0);
+  if (chars == 0) return GetLastError();
+  WCHAR* pathw = (WCHAR*) malloc(chars * sizeof(WCHAR));
+  if (pathw == NULL) return ERROR_OUTOFMEMORY;
+  MultiByteToWideChar(CP_UTF8, 0, path, -1, pathw, chars);
+  HANDLE handle = CreateFileW(
+    pathw,
+    FILE_GENERIC_READ | FILE_GENERIC_WRITE,
+    0L,
+    NULL,
+    OPEN_EXISTING,
+    NULL,
+    NULL
+  );
+  free(pathw);
+  if (handle == INVALID_HANDLE_VALUE) return GetLastError();
+  CloseHandle(handle);
+  return 0;
+#else
+  return -1;
+#endif
+}
+
+class OpenWorker : public Nan::AsyncWorker {
+ public:
+  OpenWorker(
+    v8::Local<v8::Object> &pathHandle,
+    Nan::Callback *callback
+  ) : Nan::AsyncWorker(callback) {
+        SaveToPersistent("pathHandle", pathHandle);
+        path = node::Buffer::Data(pathHandle);
+  }
+
+  ~OpenWorker() {}
+
+  void Execute() {
+    error = open(path);
+  }
+
+  void HandleOKCallback () {
+    Nan::HandleScope scope;
+    v8::Local<v8::Value> argv[] = {
+      Nan::New<v8::Number>(error)
+    };
+    callback->Call(1, argv, async_resource);
+  }
+
+ private:
+  const char* path;
+  int error;
+};
+
+NAN_METHOD(opened) {
+  if (
+    info.Length() != 2 ||
+    !node::Buffer::HasInstance(info[0]) ||
+    !info[1]->IsFunction()
+  ) {
+    return Nan::ThrowError(
+      "bad arguments, expected: (buffer path, function callback)"
+    );
+  }
+  v8::Local<v8::Object> pathHandle = info[0].As<v8::Object>();
+  Nan::Callback *callback = new Nan::Callback(info[1].As<v8::Function>());
+  Nan::AsyncQueueWorker(new OpenWorker(pathHandle, callback));
+}
+
+NAN_MODULE_INIT(Init) {
+  NAN_EXPORT(target, opened);
+}
+
+NODE_MODULE(binding, Init)
+
+// S.D.G.
diff --git a/binding.gyp b/binding.gyp
new file mode 100644
index 0000000..ad51e1f
--- /dev/null
+++ b/binding.gyp
@@ -0,0 +1,20 @@
+{
+  "targets": [
+    {
+      "target_name": "binding",
+      "sources": [ "binding.cc" ],
+      "include_dirs": [ "<!(node -e \"require('nan')\")" ]
+    },
+    {
+      "target_name": "copy",
+      "type": "none",
+      "dependencies": [ "binding" ],
+      "copies": [
+        {
+          'destination': '<(module_root_dir)',
+          'files': ['<(module_root_dir)/build/Release/binding.node']
+        }
+      ]
+    }
+  ]
+}
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..7714888
--- /dev/null
+++ b/index.js
@@ -0,0 +1,253 @@
+'use strict';
+
+var Node = {
+  child: require('child_process'),
+  fs: require('fs'),
+  path: require('path'),
+  process: process
+};
+
+var Queue = require('@ronomon/queue');
+
+function assertFunction(key, value) {
+  if (typeof value !== 'function') {
+    throw new Error(key + ' must be a function');
+  }
+}
+
+function assertPath(key, value) {
+  if (typeof value !== 'string') {
+    throw new Error(key + ' must be a string');
+  }
+  if (value.length === 0) {
+    throw new Error(key + ' must not be empty');
+  }
+  if (value.indexOf('\u0000') !== -1) {
+    throw new Error(key + ' must be a string without null bytes');
+  }
+  if (value.indexOf(assertPathBadSep) !== -1) {
+    throw new Error(key + ' must be a string without ' + assertPathBadSepName);
+  }
+}
+
+if (Node.process.platform === 'win32') {
+  var assertPathBadSep = '\/';
+  var assertPathBadSepName = 'forward slashes';
+} else {
+  var assertPathBadSep = '\\';
+  var assertPathBadSepName = 'backslashes';
+}
+
+function assertPaths(key, value) {
+  if (!value || value.constructor !== Array) {
+    throw new Error(key + ' must be an array');
+  }
+  for (var index = 0, length = value.length; index < length; index++) {
+    assertPath('path at index ' + index, value[index]);
+  }
+}
+
+function pathBuffer(path) {
+  var pathLong = Node.path._makeLong(path);
+  var buffer = Buffer.alloc(Buffer.byteLength(pathLong, 'utf-8') + 1);
+  buffer.write(pathLong, 0, buffer.length - 1, 'utf-8');
+  buffer[buffer.length - 1] = 0;
+  if (buffer.indexOf(0) !== buffer.length - 1) {
+    throw new Error('path must be a string without null bytes');
+  }
+  return buffer;
+}
+
+var Unix = {};
+
+Unix.file = function(path, end) {
+  var self = this;
+  assertPath('path', path);
+  assertFunction('end', end);
+  self.files([path],
+    function(error, files) {
+      if (error) return end(error);
+      end(undefined, files[path]);
+    }
+  );
+};
+
+Unix.files = function(paths, end) {
+  var self = this;
+  assertPaths('paths', paths);
+  assertFunction('end', end);
+  var files = {};
+  var queue = new Queue(1); // Concurrency yields no improvement with lsof.
+  queue.onData = function(paths, end) {
+    var command = 'lsof';
+    var args = ['-F', 'n', '--'].concat(paths);
+    var options = {
+      encoding: 'utf-8',
+      maxBuffer: 2 * 1024 * 1024
+    };
+    Node.child.execFile(command, args, options,
+      function(error, stdout, stderr) {
+        // lsof returns an error and a status code of 1 if a file is not open:
+        if (error && error.code === 1 && stderr.length === 0) error = undefined;
+        if (error) {
+          if (/No such file or directory/i.test(stderr)) {
+            error.code = 'ENOENT';
+          }
+          return end(error);
+        }
+        var lines = stdout.split('\n');
+        for (var index = 0, length = lines.length; index < length; index++) {
+          var line = lines[index];
+          if (line[0] != 'n') continue;
+          var candidate = self.unescape(line.slice(1));
+          if (files.hasOwnProperty(candidate)) files[candidate] = true;
+        }
+        end();
+      }
+    );
+  };
+  queue.onEnd = function(error) {
+    if (error) return end(error);
+    end(undefined, files);
+  };
+  // lsof performs in constant time regardless of the number of paths.
+  // We therefore batch calls to lsof to improve latency.
+  // We must be careful however not to exceed any limits on command length.
+  // 32 paths at 32768 bytes per path requires just over 1 MB.
+  // We assume we are safe up to 2 MB.
+  // See: xargs --show-limits
+  var batch = [];
+  for (var index = 0, length = paths.length; index < length; index++) {
+    var path = paths[index];
+    if (files.hasOwnProperty(path)) continue;
+    files[path] = false;
+    batch.push(path);
+    if (batch.length === 32) {
+      queue.push(batch);
+      batch = [];
+    }
+  }
+  if (batch.length) queue.push(batch);
+  queue.end();
+};
+
+Unix.unescape = function(sourceString) {
+  var self = this;
+  var source = Buffer.from(sourceString, 'utf-8');
+  var target;
+  var targetIndex;
+  var sourceIndex = 0;
+  var sourceLength = source.length;
+  while (sourceIndex < sourceLength) {
+    if (source[sourceIndex] === 92 && sourceIndex + 1 < sourceLength) { // "\\"
+      if (!target) {
+        target = Buffer.alloc(sourceLength);
+        targetIndex = source.copy(target, 0, 0, sourceIndex);
+      }
+      sourceIndex++;
+      target[targetIndex++] = self.unescapeTable[source[sourceIndex++]];
+    } else if (target) {
+      target[targetIndex++] = source[sourceIndex++];
+    } else {
+      sourceIndex++;
+    }
+  }
+  if (target) {
+    return target.toString('utf-8', 0, targetIndex);
+  } else {
+    return sourceString;
+  }
+};
+
+Unix.unescapeTable = (function() {
+  var table = Buffer.alloc(256);
+  for (var code = 0; code < 256; code++) table[code] = code;
+  table['b'.charCodeAt(0)] = '\b'.charCodeAt(0);
+  table['f'.charCodeAt(0)] = '\f'.charCodeAt(0);
+  table['t'.charCodeAt(0)] = '\t'.charCodeAt(0);
+  table['n'.charCodeAt(0)] = '\n'.charCodeAt(0);
+  table['r'.charCodeAt(0)] = '\r'.charCodeAt(0);
+  return table;
+})();
+
+var Windows = {};
+
+// See: https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382.aspx
+Windows.codes = {
+  1: 'EISDIR', // ERROR_INVALID_FUNCTION
+  2: 'ENOENT', // ERROR_FILE_NOT_FOUND
+  3: 'ENOENT', // ERROR_PATH_NOT_FOUND
+  4: 'EMFILE', // ERROR_TOO_MANY_OPEN_FILES
+  5: 'EPERM', // ERROR_ACCESS_DENIED
+  6: 'EBADF', // ERROR_INVALID_HANDLE
+  8: 'ENOMEM', // ERROR_NOT_ENOUGH_MEMORY
+  14: 'ENOMEM', // ERROR_OUTOFMEMORY
+  15: 'ENOENT', // ERROR_INVALID_DRIVE
+  32: 'ERROR_SHARING_VIOLATION',
+  33: 'ERROR_LOCK_VIOLATION'
+};
+
+if (Node.process.platform === 'win32') {
+  Windows.binding = require('./binding.node');
+}
+
+Windows.file = function(path, end) {
+  var self = this;
+  assertPath('path', path);
+  assertFunction('end', end);
+  self.binding.opened(pathBuffer(path),
+    function(result) {
+      if (result === 0) return end(undefined, false);
+      if (self.codes.hasOwnProperty(result)) {
+        var code = self.codes[result];
+      } else {
+        var code = 'ENOSYS';
+      }
+      if (
+        code === 'ERROR_SHARING_VIOLATION' ||
+        code === 'ERROR_LOCK_VIOLATION'
+      ) {
+        return end(undefined, true);
+      }
+      var error = new Error(code + ': -' + result + ', opened(' + path + ')');
+      error.code = code;
+      end(error);
+    }
+  );
+};
+
+Windows.files = function(paths, end) {
+  var self = this;
+  assertPaths('paths', paths);
+  assertFunction('end', end);
+  var files = {};
+  var queue = new Queue(4);
+  queue.onData = function(path, end) {
+    self.file(path,
+      function(error, opened) {
+        if (error) return end(error);
+        if (opened) files[path] = true;
+        end();
+      }
+    );
+  };
+  queue.onEnd = function(error) {
+    if (error) return end(error);
+    end(undefined, files);
+  };
+  for (var index = 0, length = paths.length; index < length; index++) {
+    var path = paths[index];
+    if (files.hasOwnProperty(path)) continue;
+    files[path] = false;
+    queue.push(path);
+  }
+  queue.end();
+};
+
+if (Node.process.platform === 'win32') {
+  module.exports = Windows;
+} else {
+  module.exports = Unix;
+}
+
+// S.D.G.
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..5b563bb
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,18 @@
+{
+  "name": "@ronomon/opened",
+  "version": "1.5.1",
+  "lockfileVersion": 1,
+  "requires": true,
+  "dependencies": {
+    "@ronomon/queue": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/@ronomon/queue/-/queue-3.0.0.tgz",
+      "integrity": "sha512-+Dnc8cNXa0mI1cD+YdA3mmQP8j1CjQKXfILiXgZGWAtauMIUxuhRgnOLgabKjEj+Wa8r2rQKsaNaDayxauImGQ=="
+    },
+    "nan": {
+      "version": "2.11.0",
+      "resolved": "https://registry.npmjs.org/nan/-/nan-2.11.0.tgz",
+      "integrity": "sha512-F4miItu2rGnV2ySkXOQoA8FKz/SR2Q2sWP0sbTxNxz/tuokeC8WxOhPMcwi0qIyGtVn/rrSeLbvVkznqCdwYnw=="
+    }
+  }
+}
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..87c4e1c
--- /dev/null
+++ b/package.json
@@ -0,0 +1,39 @@
+{
+  "name": "@ronomon/opened",
+  "version": "1.5.1",
+  "description": "Check if a file is open in another application on Windows, macOS and Linux.",
+  "main": "index.js",
+  "files": [
+    "binding.cc",
+    "binding.gyp",
+    "index.js",
+    "test.js"
+  ],
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/ronomon/opened.git"
+  },
+  "keywords": [
+    "exclusive",
+    "fd",
+    "file",
+    "fuser",
+    "lsof",
+    "open",
+    "opened"
+  ],
+  "author": "Joran Dirk Greef",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/ronomon/opened/issues"
+  },
+  "homepage": "https://github.com/ronomon/opened#readme",
+  "scripts": {
+    "postinstall": "node-gyp clean",
+    "test": "node test.js"
+  },
+  "dependencies": {
+    "@ronomon/queue": "^3.0.0",
+    "nan": "^2.11.0"
+  }
+}
diff --git a/test-injection.js b/test-injection.js
new file mode 100644
index 0000000..7989bce
--- /dev/null
+++ b/test-injection.js
@@ -0,0 +1,15 @@
+const assert = require('assert');
+const fs = require('fs');
+
+const Opened = require('./index.js');
+
+const paths = ['$(touch command_line_injection)'];
+
+Opened.files(paths,
+  function(error, hashTable) {
+    assert(!!error);
+    assert(fs.existsSync('command_line_injection') === false);
+    console.log('PASS');
+  }
+);
+
diff --git a/test.js b/test.js
new file mode 100644
index 0000000..c585ff8
--- /dev/null
+++ b/test.js
@@ -0,0 +1,269 @@
+var Node = {
+  fs: require('fs'),
+  path: require('path'),
+  process: process
+};
+var random = Math.random.bind(Math);
+var Queue = require('@ronomon/queue');
+
+var namespace = 'Opened';
+
+var Test = {};
+
+Test.equal = function(value, expected, namespace, description) {
+  value = JSON.stringify(value) + '';
+  expected = JSON.stringify(expected) + '';
+  if (value === expected) {
+    Test.pass(namespace, description, expected);
+  } else {
+    Test.fail(namespace, description, value + ' !== ' + expected);
+  }
+};
+
+Test.fail = function(namespace, description, message) {
+  console.log('');
+  throw 'FAIL: ' + Test.message(namespace, description, message);
+};
+
+Test.message = function(namespace, description, message) {
+  if ((namespace = namespace || '')) namespace += ': ';
+  if ((description = description || '')) description += ': ';
+  return namespace + description + (message || '');
+};
+
+Test.pass = function(namespace, description, message) {
+  console.log('PASS: ' + Test.message(namespace, description, message));
+};
+
+var root = Node.path.resolve(module.filename, '..');
+if (!root) throw new Error('root must not be empty');
+
+var fixtures = Node.path.join(root, 'opened_fixtures');
+
+var binding = require(Node.path.join(root, 'index.js'));
+
+var ALPHABET = '';
+ALPHABET += 'abcdefghijklmnopqrstuvwxyz';
+ALPHABET += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
+ALPHABET += '0123456789';
+ALPHABET += 'àáâäæãåāèéêëēėę';
+if (Node.process.platform === 'win32') {
+  ALPHABET += '   ';
+} else {
+  ALPHABET += '\b\f\t\n\r   ';
+}
+
+function close(fds) {
+  fds.forEach(
+    function(fd) {
+      Node.fs.closeSync(fd);
+    }
+  );
+}
+
+function createPath(path) {
+  Node.fs.writeFileSync(path, '');
+}
+
+function createPaths(paths) {
+  paths.forEach(
+    function(path) {
+      createPath(path);
+    }
+  );
+}
+
+function generatePath() {
+  var chars = 1 + Math.floor(random() * 16);
+  var string = '';
+  while (string.length < chars) {
+    string += ALPHABET[Math.floor(random() * ALPHABET.length)];
+    if (string.trim() === string) continue;
+    string += ALPHABET[Math.floor(random() * ALPHABET.length)];
+    if (string.trim() === string) continue;
+    string += ALPHABET[Math.floor(random() * ALPHABET.length)];
+    string = string.trim(); // Avoid leading/trailing space on Windows.
+  }
+  if (random() < 0.5) {
+    if (random() < 0.5) {
+      string = string.normalize('NFC');
+    } else {
+      string = string.normalize('NFD');
+    }
+  }
+  return Node.path.join(fixtures, string);
+}
+
+function generatePaths() {
+  var paths = [];
+  var keys = {};
+  if (random() < 0.01) return paths;
+  var length = Math.floor(random() * 128);
+  while (length--) {
+    var path = generatePath();
+    var key = path.toUpperCase().normalize('NFC');
+    if (keys.hasOwnProperty(key)) continue;
+    keys[key] = 1;
+    paths.push(path);
+  }
+  return paths;
+}
+
+function openPath(path, expect, fds) {
+  if (random() < 0.5) {
+    expect[path] = false;
+  } else {
+    expect[path] = true;
+    fds.push(Node.fs.openSync(path, 'r+'));
+  }
+}
+
+function openPaths(paths, expect, fds) {
+  paths.forEach(
+    function(path) {
+      openPath(path, expect, fds);
+    }
+  );
+}
+
+function removeFixtures(callback) {
+  function remove() {
+    try {
+      var names = Node.fs.readdirSync(fixtures);
+    } catch (error) {
+      if (error.code !== 'ENOENT') throw error;
+      var names = [];
+    }
+    names.forEach(
+      function(name) {
+        Node.fs.unlinkSync(Node.path.join(fixtures, name));
+      }
+    );
+    try {
+      Node.fs.rmdirSync(fixtures);
+    } catch (error) {
+      if (error.code !== 'ENOENT') throw error;
+    }
+  }
+  if (callback) {
+    setTimeout(
+      function() {
+        remove();
+        callback();
+      },
+      // Wait for handles to be released by antivirus:
+      Node.process.platform === 'win32' ? 2000 : 0
+    );
+  } else {
+    remove();
+  }
+}
+
+function removePath(path) {
+  try {
+    Node.fs.unlinkSync(path, '');
+  } catch (error) {
+    // Ignore
+  }
+}
+
+function removePaths(paths) {
+  paths.forEach(
+    function(path) {
+      removePath(path);
+    }
+  );
+}
+
+removeFixtures();
+
+try {
+  Node.fs.mkdirSync(fixtures);
+} catch (error) {
+  if (error.code !== 'EEXIST') throw error;
+}
+
+var count = 0;
+var elapsed = 0;
+var maxCount = 0;
+var maxBatch = 0;
+var queue = new Queue(1);
+queue.onData = function(test, end) {
+  var paths = generatePaths();
+  var expect = {};
+  var fds = [];
+  createPaths(paths);
+  openPaths(paths, expect, fds);
+  var enoent = false;
+  if (random() < 0.2) {
+    enoent = generatePath();
+    paths.push(enoent);
+  }
+  var now = Date.now();
+  binding.files(paths,
+    function(error, actual) {
+      var time = Date.now() - now;
+      count += paths.length;
+      elapsed += time;
+      if (time > maxBatch) {
+        maxCount = paths.length;
+        maxBatch = time;
+      }
+      try {
+        if (enoent) {
+          Test.equal(error.code, 'ENOENT', namespace, 'error');
+          close(fds);
+          removePaths(paths);
+          return end();
+        } else {
+          Test.equal(error === undefined, true, namespace, 'error undefined');
+        }
+        if (error) throw error;
+        for (var a in actual) {
+          Test.equal(
+            expect.hasOwnProperty(a),
+            true,
+            namespace,
+            JSON.stringify(a) + ': name'
+          );
+          Test.equal(
+            actual[a],
+            expect[a],
+            namespace,
+            JSON.stringify(a) + ': open'
+          );
+        }
+        var x = Object.keys(actual).sort().join('');
+        var y = Object.keys(expect).sort().join('');
+        if (y !== x) {
+          Test.equal(x, y, namespace, 'names');
+        }
+      } catch (error) {
+        close(fds);
+        removePaths(paths);
+        return end(error);
+      }
+      close(fds);
+      removePaths(paths);
+      end();
+    }
+  );
+};
+queue.onEnd = function(error) {
+  removeFixtures(
+    function() {
+      if (error) throw error;
+      var avg = (elapsed / count).toFixed(5);
+      console.log(
+        avg + 'ms per file, ' + maxBatch + 'ms per ' + maxCount + ' file batch.'
+      );
+      console.log('================');
+      console.log('PASSED ALL TESTS');
+      console.log('================');
+    }
+  );
+};
+for (var test = 0; test < 10; test++) {
+  queue.push(test);
+}
+queue.end();

Fixed code: .DS_Store
binding.node
build
node_modules
opened_fixtures
The MIT License (MIT)

Copyright (c) 2017 Ronomon

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
# opened
Check if a file is open in another application on Windows, macOS and Linux. Linux requires privileges.

## Installation
```
npm install @ronomon/opened
```

## Windows
`Opened` uses a native binding on Windows to try and open an existing file with exclusive sharing mode (`dwShareMode`) and detect an `ERROR_SHARING_VIOLATION` error if another application already has an open handle to the file. This will detect any applications with open handles to the file, but not applications which have opened, buffered the file for display, and then closed the handle (i.e. applications which may be showing the file to the user, but which no longer have an open handle to the file).

## Unix
`Opened` uses `lsof` on macOS and on Linux. On Linux (but not on macOS), `lsof` requires sudo permissions to iterate across open file descriptors for the user, otherwise no files will be detected as open and no permissions error will be returned.

## Usage

```javascript
var Opened = require('@ronomon/opened');
var paths = [...];
Opened.files(paths,
  function(error, hashTable) {
    if (error) throw error;
    paths.forEach(
      function(path) {
        console.log(path + ' open=' + hashTable[path]);
      }
    );
  }
);
```

## Tests
```
node test.js
```
#include <nan.h>
#if defined(_WIN32)
#include <io.h>
#include <windows.h>
#endif

int open(const char* path) {
#if defined(_WIN32)
  int chars = MultiByteToWideChar(CP_UTF8, 0, path, -1, NULL, 0);
  if (chars == 0) return GetLastError();
  WCHAR* pathw = (WCHAR*) malloc(chars * sizeof(WCHAR));
  if (pathw == NULL) return ERROR_OUTOFMEMORY;
  MultiByteToWideChar(CP_UTF8, 0, path, -1, pathw, chars);
  HANDLE handle = CreateFileW(
    pathw,
    FILE_GENERIC_READ | FILE_GENERIC_WRITE,
    0L,
    NULL,
    OPEN_EXISTING,
    NULL,
    NULL
  );
  free(pathw);
  if (handle == INVALID_HANDLE_VALUE) return GetLastError();
  CloseHandle(handle);
  return 0;
#else
  return -1;
#endif
}

class OpenWorker : public Nan::AsyncWorker {
 public:
  OpenWorker(
    v8::Local<v8::Object> &pathHandle,
    Nan::Callback *callback
  ) : Nan::AsyncWorker(callback) {
        SaveToPersistent("pathHandle", pathHandle);
        path = node::Buffer::Data(pathHandle);
  }

  ~OpenWorker() {}

  void Execute() {
    error = open(path);
  }

  void HandleOKCallback () {
    Nan::HandleScope scope;
    v8::Local<v8::Value> argv[] = {
      Nan::New<v8::Number>(error)
    };
    callback->Call(1, argv, async_resource);
  }

 private:
  const char* path;
  int error;
};

NAN_METHOD(opened) {
  if (
    info.Length() != 2 ||
    !node::Buffer::HasInstance(info[0]) ||
    !info[1]->IsFunction()
  ) {
    return Nan::ThrowError(
      "bad arguments, expected: (buffer path, function callback)"
    );
  }
  v8::Local<v8::Object> pathHandle = info[0].As<v8::Object>();
  Nan::Callback *callback = new Nan::Callback(info[1].As<v8::Function>());
  Nan::AsyncQueueWorker(new OpenWorker(pathHandle, callback));
}

NAN_MODULE_INIT(Init) {
  NAN_EXPORT(target, opened);
}

NODE_MODULE(binding, Init)

// S.D.G.
{
  "targets": [
    {
      "target_name": "binding",
      "sources": [ "binding.cc" ],
      "include_dirs": [ "<!(node -e \"require('nan')\")" ]
    },
    {
      "target_name": "copy",
      "type": "none",
      "dependencies": [ "binding" ],
      "copies": [
        {
          'destination': '<(module_root_dir)',
          'files': ['<(module_root_dir)/build/Release/binding.node']
        }
      ]
    }
  ]
}
'use strict';

var Node = {
  child: require('child_process'),
  fs: require('fs'),
  path: require('path'),
  process: process
};

var Queue = require('@ronomon/queue');

function assertFunction(key, value) {
  if (typeof value !== 'function') {
    throw new Error(key + ' must be a function');
  }
}

function assertPath(key, value) {
  if (typeof value !== 'string') {
    throw new Error(key + ' must be a string');
  }
  if (value.length === 0) {
    throw new Error(key + ' must not be empty');
  }
  if (value.indexOf('\u0000') !== -1) {
    throw new Error(key + ' must be a string without null bytes');
  }
  if (value.indexOf(assertPathBadSep) !== -1) {
    throw new Error(key + ' must be a string without ' + assertPathBadSepName);
  }
}

if (Node.process.platform === 'win32') {
  var assertPathBadSep = '\/';
  var assertPathBadSepName = 'forward slashes';
} else {
  var assertPathBadSep = '\\';
  var assertPathBadSepName = 'backslashes';
}

function assertPaths(key, value) {
  if (!value || value.constructor !== Array) {
    throw new Error(key + ' must be an array');
  }
  for (var index = 0, length = value.length; index < length; index++) {
    assertPath('path at index ' + index, value[index]);
  }
}

function pathBuffer(path) {
  var pathLong = Node.path._makeLong(path);
  var buffer = Buffer.alloc(Buffer.byteLength(pathLong, 'utf-8') + 1);
  buffer.write(pathLong, 0, buffer.length - 1, 'utf-8');
  buffer[buffer.length - 1] = 0;
  if (buffer.indexOf(0) !== buffer.length - 1) {
    throw new Error('path must be a string without null bytes');
  }
  return buffer;
}

var Unix = {};

Unix.file = function(path, end) {
  var self = this;
  assertPath('path', path);
  assertFunction('end', end);
  self.files([path],
    function(error, files) {
      if (error) return end(error);
      end(undefined, files[path]);
    }
  );
};

Unix.files = function(paths, end) {
  var self = this;
  assertPaths('paths', paths);
  assertFunction('end', end);
  var files = {};
  var queue = new Queue(1); // Concurrency yields no improvement with lsof.
  queue.onData = function(paths, end) {
    var command = 'lsof';
    var args = ['-F', 'n', '--'].concat(paths);
    var options = {
      encoding: 'utf-8',
      maxBuffer: 2 * 1024 * 1024
    };
    Node.child.execFile(command, args, options,
      function(error, stdout, stderr) {
        // lsof returns an error and a status code of 1 if a file is not open:
        if (error && error.code === 1 && stderr.length === 0) error = undefined;
        if (error) {
          if (/No such file or directory/i.test(stderr)) {
            error.code = 'ENOENT';
          }
          return end(error);
        }
        var lines = stdout.split('\n');
        for (var index = 0, length = lines.length; index < length; index++) {
          var line = lines[index];
          if (line[0] != 'n') continue;
          var candidate = self.unescape(line.slice(1));
          if (files.hasOwnProperty(candidate)) files[candidate] = true;
        }
        end();
      }
    );
  };
  queue.onEnd = function(error) {
    if (error) return end(error);
    end(undefined, files);
  };
  // lsof performs in constant time regardless of the number of paths.
  // We therefore batch calls to lsof to improve latency.
  // We must be careful however not to exceed any limits on command length.
  // 32 paths at 32768 bytes per path requires just over 1 MB.
  // We assume we are safe up to 2 MB.
  // See: xargs --show-limits
  var batch = [];
  for (var index = 0, length = paths.length; index < length; index++) {
    var path = paths[index];
    if (files.hasOwnProperty(path)) continue;
    files[path] = false;
    batch.push(path);
    if (batch.length === 32) {
      queue.push(batch);
      batch = [];
    }
  }
  if (batch.length) queue.push(batch);
  queue.end();
};

Unix.unescape = function(sourceString) {
  var self = this;
  var source = Buffer.from(sourceString, 'utf-8');
  var target;
  var targetIndex;
  var sourceIndex = 0;
  var sourceLength = source.length;
  while (sourceIndex < sourceLength) {
    if (source[sourceIndex] === 92 && sourceIndex + 1 < sourceLength) { // "\\"
      if (!target) {
        target = Buffer.alloc(sourceLength);
        targetIndex = source.copy(target, 0, 0, sourceIndex);
      }
      sourceIndex++;
      target[targetIndex++] = self.unescapeTable[source[sourceIndex++]];
    } else if (target) {
      target[targetIndex++] = source[sourceIndex++];
    } else {
      sourceIndex++;
    }
  }
  if (target) {
    return target.toString('utf-8', 0, targetIndex);
  } else {
    return sourceString;
  }
};

Unix.unescapeTable = (function() {
  var table = Buffer.alloc(256);
  for (var code = 0; code < 256; code++) table[code] = code;
  table['b'.charCodeAt(0)] = '\b'.charCodeAt(0);
  table['f'.charCodeAt(0)] = '\f'.charCodeAt(0);
  table['t'.charCodeAt(0)] = '\t'.charCodeAt(0);
  table['n'.charCodeAt(0)] = '\n'.charCodeAt(0);
  table['r'.charCodeAt(0)] = '\r'.charCodeAt(0);
  return table;
})();

var Windows = {};

// See: https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382.aspx
Windows.codes = {
  1: 'EISDIR', // ERROR_INVALID_FUNCTION
  2: 'ENOENT', // ERROR_FILE_NOT_FOUND
  3: 'ENOENT', // ERROR_PATH_NOT_FOUND
  4: 'EMFILE', // ERROR_TOO_MANY_OPEN_FILES
  5: 'EPERM', // ERROR_ACCESS_DENIED
  6: 'EBADF', // ERROR_INVALID_HANDLE
  8: 'ENOMEM', // ERROR_NOT_ENOUGH_MEMORY
  14: 'ENOMEM', // ERROR_OUTOFMEMORY
  15: 'ENOENT', // ERROR_INVALID_DRIVE
  32: 'ERROR_SHARING_VIOLATION',
  33: 'ERROR_LOCK_VIOLATION'
};

if (Node.process.platform === 'win32') {
  Windows.binding = require('./binding.node');
}

Windows.file = function(path, end) {
  var self = this;
  assertPath('path', path);
  assertFunction('end', end);
  self.binding.opened(pathBuffer(path),
    function(result) {
      if (result === 0) return end(undefined, false);
      if (self.codes.hasOwnProperty(result)) {
        var code = self.codes[result];
      } else {
        var code = 'ENOSYS';
      }
      if (
        code === 'ERROR_SHARING_VIOLATION' ||
        code === 'ERROR_LOCK_VIOLATION'
      ) {
        return end(undefined, true);
      }
      var error = new Error(code + ': -' + result + ', opened(' + path + ')');
      error.code = code;
      end(error);
    }
  );
};

Windows.files = function(paths, end) {
  var self = this;
  assertPaths('paths', paths);
  assertFunction('end', end);
  var files = {};
  var queue = new Queue(4);
  queue.onData = function(path, end) {
    self.file(path,
      function(error, opened) {
        if (error) return end(error);
        if (opened) files[path] = true;
        end();
      }
    );
  };
  queue.onEnd = function(error) {
    if (error) return end(error);
    end(undefined, files);
  };
  for (var index = 0, length = paths.length; index < length; index++) {
    var path = paths[index];
    if (files.hasOwnProperty(path)) continue;
    files[path] = false;
    queue.push(path);
  }
  queue.end();
};

if (Node.process.platform === 'win32') {
  module.exports = Windows;
} else {
  module.exports = Unix;
}

// S.D.G.
{
  "name": "@ronomon/opened",
  "version": "1.5.1",
  "lockfileVersion": 1,
  "requires": true,
  "dependencies": {
    "@ronomon/queue": {
      "version": "3.0.0",
      "resolved": "https://registry.npmjs.org/@ronomon/queue/-/queue-3.0.0.tgz",
      "integrity": "sha512-+Dnc8cNXa0mI1cD+YdA3mmQP8j1CjQKXfILiXgZGWAtauMIUxuhRgnOLgabKjEj+Wa8r2rQKsaNaDayxauImGQ=="
    },
    "nan": {
      "version": "2.11.0",
      "resolved": "https://registry.npmjs.org/nan/-/nan-2.11.0.tgz",
      "integrity": "sha512-F4miItu2rGnV2ySkXOQoA8FKz/SR2Q2sWP0sbTxNxz/tuokeC8WxOhPMcwi0qIyGtVn/rrSeLbvVkznqCdwYnw=="
    }
  }
}
{
  "name": "@ronomon/opened",
  "version": "1.5.1",
  "description": "Check if a file is open in another application on Windows, macOS and Linux.",
  "main": "index.js",
  "files": [
    "binding.cc",
    "binding.gyp",
    "index.js",
    "test.js"
  ],
  "repository": {
    "type": "git",
    "url": "git+https://github.com/ronomon/opened.git"
  },
  "keywords": [
    "exclusive",
    "fd",
    "file",
    "fuser",
    "lsof",
    "open",
    "opened"
  ],
  "author": "Joran Dirk Greef",
  "license": "MIT",
  "bugs": {
    "url": "https://github.com/ronomon/opened/issues"
  },
  "homepage": "https://github.com/ronomon/opened#readme",
  "scripts": {
    "postinstall": "node-gyp clean",
    "test": "node test.js"
  },
  "dependencies": {
    "@ronomon/queue": "^3.0.0",
    "nan": "^2.11.0"
  }
}
const assert = require('assert');
const fs = require('fs');

const Opened = require('./index.js');

const paths = ['$(touch command_line_injection)'];

Opened.files(paths,
  function(error, hashTable) {
    assert(!!error);
    assert(fs.existsSync('command_line_injection') === false);
    console.log('PASS');
  }
);

var Node = {
  fs: require('fs'),
  path: require('path'),
  process: process
};
var random = Math.random.bind(Math);
var Queue = require('@ronomon/queue');

var namespace = 'Opened';

var Test = {};

Test.equal = function(value, expected, namespace, description) {
  value = JSON.stringify(value) + '';
  expected = JSON.stringify(expected) + '';
  if (value === expected) {
    Test.pass(namespace, description, expected);
  } else {
    Test.fail(namespace, description, value + ' !== ' + expected);
  }
};

Test.fail = function(namespace, description, message) {
  console.log('');
  throw 'FAIL: ' + Test.message(namespace, description, message);
};

Test.message = function(namespace, description, message) {
  if ((namespace = namespace || '')) namespace += ': ';
  if ((description = description || '')) description += ': ';
  return namespace + description + (message || '');
};

Test.pass = function(namespace, description, message) {
  console.log('PASS: ' + Test.message(namespace, description, message));
};

var root = Node.path.resolve(module.filename, '..');
if (!root) throw new Error('root must not be empty');

var fixtures = Node.path.join(root, 'opened_fixtures');

var binding = require(Node.path.join(root, 'index.js'));

var ALPHABET = '';
ALPHABET += 'abcdefghijklmnopqrstuvwxyz';
ALPHABET += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
ALPHABET += '0123456789';
ALPHABET += 'àáâäæãåāèéêëēėę';
if (Node.process.platform === 'win32') {
  ALPHABET += '   ';
} else {
  ALPHABET += '\b\f\t\n\r   ';
}

function close(fds) {
  fds.forEach(
    function(fd) {
      Node.fs.closeSync(fd);
    }
  );
}

function createPath(path) {
  Node.fs.writeFileSync(path, '');
}

function createPaths(paths) {
  paths.forEach(
    function(path) {
      createPath(path);
    }
  );
}

function generatePath() {
  var chars = 1 + Math.floor(random() * 16);
  var string = '';
  while (string.length < chars) {
    string += ALPHABET[Math.floor(random() * ALPHABET.length)];
    if (string.trim() === string) continue;
    string += ALPHABET[Math.floor(random() * ALPHABET.length)];
    if (string.trim() === string) continue;
    string += ALPHABET[Math.floor(random() * ALPHABET.length)];
    string = string.trim(); // Avoid leading/trailing space on Windows.
  }
  if (random() < 0.5) {
    if (random() < 0.5) {
      string = string.normalize('NFC');
    } else {
      string = string.normalize('NFD');
    }
  }
  return Node.path.join(fixtures, string);
}

function generatePaths() {
  var paths = [];
  var keys = {};
  if (random() < 0.01) return paths;
  var length = Math.floor(random() * 128);
  while (length--) {
    var path = generatePath();
    var key = path.toUpperCase().normalize('NFC');
    if (keys.hasOwnProperty(key)) continue;
    keys[key] = 1;
    paths.push(path);
  }
  return paths;
}

function openPath(path, expect, fds) {
  if (random() < 0.5) {
    expect[path] = false;
  } else {
    expect[path] = true;
    fds.push(Node.fs.openSync(path, 'r+'));
  }
}

function openPaths(paths, expect, fds) {
  paths.forEach(
    function(path) {
      openPath(path, expect, fds);
    }
  );
}

function removeFixtures(callback) {
  function remove() {
    try {
      var names = Node.fs.readdirSync(fixtures);
    } catch (error) {
      if (error.code !== 'ENOENT') throw error;
      var names = [];
    }
    names.forEach(
      function(name) {
        Node.fs.unlinkSync(Node.path.join(fixtures, name));
      }
    );
    try {
      Node.fs.rmdirSync(fixtures);
    } catch (error) {
      if (error.code !== 'ENOENT') throw error;
    }
  }
  if (callback) {
    setTimeout(
      function() {
        remove();
        callback();
      },
      // Wait for handles to be released by antivirus:
      Node.process.platform === 'win32' ? 2000 : 0
    );
  } else {
    remove();
  }
}

function removePath(path) {
  try {
    Node.fs.unlinkSync(path, '');
  } catch (error) {
    // Ignore
  }
}

function removePaths(paths) {
  paths.forEach(
    function(path) {
      removePath(path);
    }
  );
}

removeFixtures();

try {
  Node.fs.mkdirSync(fixtures);
} catch (error) {
  if (error.code !== 'EEXIST') throw error;
}

var count = 0;
var elapsed = 0;
var maxCount = 0;
var maxBatch = 0;
var queue = new Queue(1);
queue.onData = function(test, end) {
  var paths = generatePaths();
  var expect = {};
  var fds = [];
  createPaths(paths);
  openPaths(paths, expect, fds);
  var enoent = false;
  if (random() < 0.2) {
    enoent = generatePath();
    paths.push(enoent);
  }
  var now = Date.now();
  binding.files(paths,
    function(error, actual) {
      var time = Date.now() - now;
      count += paths.length;
      elapsed += time;
      if (time > maxBatch) {
        maxCount = paths.length;
        maxBatch = time;
      }
      try {
        if (enoent) {
          Test.equal(error.code, 'ENOENT', namespace, 'error');
          close(fds);
          removePaths(paths);
          return end();
        } else {
          Test.equal(error === undefined, true, namespace, 'error undefined');
        }
        if (error) throw error;
        for (var a in actual) {
          Test.equal(
            expect.hasOwnProperty(a),
            true,
            namespace,
            JSON.stringify(a) + ': name'
          );
          Test.equal(
            actual[a],
            expect[a],
            namespace,
            JSON.stringify(a) + ': open'
          );
        }
        var x = Object.keys(actual).sort().join('');
        var y = Object.keys(expect).sort().join('');
        if (y !== x) {
          Test.equal(x, y, namespace, 'names');
        }
      } catch (error) {
        close(fds);
        removePaths(paths);
        return end(error);
      }
      close(fds);
      removePaths(paths);
      end();
    }
  );
};
queue.onEnd = function(error) {
  removeFixtures(
    function() {
      if (error) throw error;
      var avg = (elapsed / count).toFixed(5);
      console.log(
        avg + 'ms per file, ' + maxBatch + 'ms per ' + maxCount + ' file batch.'
      );
      console.log('================');
      console.log('PASSED ALL TESTS');
      console.log('================');
    }
  );
};
for (var test = 0; test < 10; test++) {
  queue.push(test);
}
queue.end();