[api] Allow for "secure" option to be passed to nconf.stores.File t…

…o perform content encryption / decryption with `crypto.createCipher`.

lib/nconf/stores/file.js

@@ -26,11 +26,25 @@ var File = exports.File = function (options) {
 
   Memory.call(this, options);
 
-  this.type   = 'file';
-  this.file   = options.file;
-  this.dir    = options.dir    || process.cwd();
-  this.format = options.format || formats.json;
-  this.json_spacing = options.json_spacing || 2;
+  this.type    = 'file';
+  this.file    = options.file;
+  this.dir     = options.dir    || process.cwd();
+  this.format  = options.format || formats.json;
+  this.secure  = options.secure;
+  this.spacing = options.json_spacing
+    || options.spacing
+    || 2;
+
+  if (this.secure) {
+    this.secure.alg = this.secure.alg || 'aes-256-ctr';
+    if (this.secure.secretPath) {
+      this.secret = fs.readFileSync(this.secure.secretPath, 'utf8');
+    }
+
+    if (!this.secure.secret) {
+      throw new Error('secure.secret option is required');
+    }
+  }
 
   if (options.search) {
     this.search(this.dir);
@@ -53,9 +67,10 @@ File.prototype.save = function (value, callback) {
     value = null;
   }
 
-  fs.writeFile(this.file, this.format.stringify(this.store, null, this.json_spacing), function (err) {
-    return err ? callback(err) : callback();
-  });
+  var contents = this.format.stringify(this.store, null, this.spacing),
+      bytes = this.tryEncrypt(contents);
+
+  fs.writeFile(this.file, bytes, callback);
 };
 
 //
@@ -66,12 +81,10 @@ File.prototype.save = function (value, callback) {
 // using the format specified by `this.format` synchronously.
 //
 File.prototype.saveSync = function (value) {
-  try {
-    fs.writeFileSync(this.file, this.format.stringify(this.store, null, this.json_spacing));
-  }
-  catch (ex) {
-    throw(ex);
-  }
+  var contents = this.format.stringify(this.store, null, this.spacing),
+      bytes = this.tryEncrypt(contents);
+
+  fs.writeFileSync(this.file, bytes);
   return this.store;
 };
 
@@ -97,12 +110,14 @@ File.prototype.load = function (callback) {
       }
 
       try {
-        //deals with string that include BOM
+        // Deals with string that include BOM
         var stringData = data.toString();
+        if (stringData.charAt(0) === '\uFEFF') {
+          stringData = stringData.substr(1);
+        }
 
-        if (stringData.charAt(0) === '\uFEFF') stringData = stringData.substr(1);
-        self.store = self.format.parse(stringData);
-
+        var contents = self.tryDecrypt(stringData);
+        self.store = self.format.parse(contents);
       }
       catch (ex) {
         return callback(new Error("Error parsing your configuration file: [" + self.file + ']: ' + ex.message));
@@ -130,9 +145,11 @@ File.prototype.loadSync = function () {
     // Else, the path exists, read it from disk
     //
     try {
-      //deals with file that include BOM
+      // Deals with file that include BOM
       var fileData = fs.readFileSync(this.file, 'utf8');
-      if (fileData.charAt(0) === '\uFEFF') fileData = fileData.substr(1);
+      if (fileData.charAt(0) === '\uFEFF') {
+        fileData = fileData.substr(1);
+      }
 
       data = this.format.parse(fileData);
       this.store = data;
@@ -145,6 +162,40 @@ File.prototype.loadSync = function () {
   return data;
 };
 
+//
+// ### function tryEncrypt ()
+// Returns an encrypted version of the contents IIF
+// `this.secure` is enabled
+//
+File.prototype.tryEncrypt = function (contents) {
+  if (!this.secure) { return contents; }
+
+  //
+  // Contents have already been stringified by the format
+  // so no need to re-stringify here.
+  //
+  return cipherConvert(contents, {
+    alg: this.secure.alg,
+    secret: this.secure.secret,
+    encs: { input: 'utf8', output: 'hex' }
+  });
+};
+
+//
+// ### function tryDecrypt (contents)
+// Returns a decrypted version of the contents IFF
+// `this.secure` is enabled.
+//
+File.prototype.tryDecrypt = function (contents) {
+  if (!this.secure) { return contents; }
+
+  return cipherConvert(contents, {
+    alg: this.secure.alg,
+    secret: this.secure.secret,
+    encs: { input: 'hex', output: 'utf8' }
+  });
+};
+
 //
 // ### function search (base)
 // #### @base {string} Base directory (or file) to begin searching for the target file.
@@ -235,3 +286,15 @@ File.prototype.search = function (base) {
 
   return fullpath;
 };
+
+//
+// ### function cipherConvert (contents, opts)
+// Returns the result of the cipher operation
+// on the contents contents.
+//
+function cipherConvert(contents, opts) {
+  var encs = opts.encs;
+  var cipher = crypto.createCipher(opts.alg, opts.secret);
+  return cipher.update(contents, encs.input, encs.output)
+    + cipher.final(encs.output);
+}