Update: generate and apply header values when key wrapping (#189)

lib/algorithms/aes-gcm.js

@@ -6,22 +6,43 @@
 "use strict";
 
 var helpers = require("./helpers.js"),
+    util = require("../util"),
     CONSTANTS = require("./constants.js"),
     GCM = require("../deps/ciphermodes/gcm");
 
-function gcmEncryptFN(size) {
+function gcmEncryptFN(size, wrap) {
   function commonChecks(key, iv) {
     if (size !== (key.length << 3)) {
        throw new Error("invalid key size");
     }
-    if (12 !== iv.length) {
+    if (!iv && !wrap) {
+      throw new Error("invalid iv");
+    }
+    if (iv && 12 !== iv.length) {
       throw new Error("invalid iv");
     }
   }
 
+  function prepareResults(results) {
+    if (wrap) {
+      var iv = util.base64url.encode(results.iv);
+      var tag = util.base64url.encode(results.tag);
+
+      results = {
+        data: results.data,
+        header: {
+          iv: iv,
+          tag: tag
+        }
+      };
+    }
+
+    return results;
+  }
+
   // ### 'fallback' implementation -- uses forge
   var fallback = function(key, pdata, props) {
-    var iv = props.iv || Buffer.alloc(0),
+    var iv = props.iv,
         adata = props.aad || props.adata || Buffer.alloc(0),
         cipher,
         cdata;
@@ -33,6 +54,8 @@ function gcmEncryptFN(size) {
       return Promise.reject(err);
     }
 
+    iv = iv || util.randomBytes(12);
+
     // setup cipher
     cipher = GCM.createCipher({
       key: key,
@@ -69,10 +92,11 @@ function gcmEncryptFN(size) {
 
         // resolve with output
         var tag = cipher.tag;
-        resolve({
+        resolve(prepareResults({
           data: cdata,
+          iv: iv,
           tag: tag
-        });
+        }));
       })();
     });
 
@@ -82,7 +106,7 @@ function gcmEncryptFN(size) {
   // ### WebCryptoAPI implementation
   // TODO: cache CryptoKey sooner
   var webcrypto = function(key, pdata, props) {
-    var iv = props.iv || Buffer.alloc(0),
+    var iv = props.iv,
         adata = props.aad || props.adata || Buffer.alloc(0);
 
     try {
@@ -91,6 +115,8 @@ function gcmEncryptFN(size) {
       return Promise.reject(err);
     }
 
+    iv = iv || util.randomBytes(12);
+
     var alg = {
       name: "AES-GCM"
     };
@@ -114,18 +140,19 @@ function gcmEncryptFN(size) {
       var cdata = result.slice(0, tagStart);
       cdata = Buffer.from(cdata);
 
-      return {
+      return prepareResults({
         data: cdata,
+        iv: iv,
         tag: tag
-      };
+      });
     });
 
     return promise;
   };
 
   // ### NodeJS implementation
   var nodejs = function(key, pdata, props) {
-    var iv = props.iv || Buffer.alloc(0),
+    var iv = props.iv,
         adata = props.aad || props.adata || Buffer.alloc(0);
 
     try {
@@ -134,6 +161,8 @@ function gcmEncryptFN(size) {
       return Promise.reject(err);
     }
 
+    iv = iv || util.randomBytes(12);
+
     var alg = "aes-" + (key.length * 8) + "-gcm";
     var cipher;
     try {
@@ -154,14 +183,16 @@ function gcmEncryptFN(size) {
     ]);
     var tag = cipher.getAuthTag();
 
-    return {
+    return prepareResults({
       data: cdata,
+      iv: iv,
       tag: tag
-    };
+    });
   };
 
   return helpers.setupFallback(nodejs, webcrypto, fallback);
 }
+
 function gcmDecryptFN(size) {
   function commonChecks(key, iv, tag) {
     if (size !== (key.length << 3)) {
@@ -331,10 +362,12 @@ var aesGcm = {};
   "A192GCMKW",
   "A256GCMKW"
 ].forEach(function(alg) {
-  var size = parseInt(/A(\d+)GCM(?:KW)?/g.exec(alg)[1]);
+  var parts = /A(\d+)GCM(KW)?/g.exec(alg);
+  var size = parseInt(parts[1]);
+  var wrap = (parts[2] === "KW");
   aesGcm[alg] = {
-    encrypt: gcmEncryptFN(size),
-    decrypt: gcmDecryptFN(size)
+    encrypt: gcmEncryptFN(size, wrap),
+    decrypt: gcmDecryptFN(size, wrap)
   };
 });