Bug 1723674 - Implement crypto.randomUUID(). r=keeler,nika

Google shipped crypto.randomUUID() in Chrome 92.

WICG draft specification for crypto.randomUUID():
https://wicg.github.io/uuid/

Differential Revision: https://phabricator.services.mozilla.com/D124313

dom/base/Crypto.cpp

@@ -3,11 +3,13 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
 #include "Crypto.h"
 #include "js/ScalarType.h"
 #include "js/experimental/TypedData.h"  // JS_GetArrayBufferViewType
 #include "nsCOMPtr.h"
 #include "nsIRandomGenerator.h"
+#include "nsReadableUtils.h"
 
 #include "mozilla/dom/CryptoBinding.h"
 #include "mozilla/dom/SubtleCrypto.h"
@@ -90,6 +92,18 @@ void Crypto::GetRandomValues(JSContext* aCx, const ArrayBufferView& aArray,
   aRetval.set(view);
 }
 
+void Crypto::RandomUUID(nsAString& aRetVal) {
+  // NSID_LENGTH == 39 == 36 UUID chars + 2 curly braces + 1 NUL byte
+  static_assert(NSID_LENGTH == 39);
+
+  nsIDToCString uuidString(nsID::GenerateUUID());
+  MOZ_ASSERT(strlen(uuidString.get()) == NSID_LENGTH - 1);
+
+  // Convert UUID chars to UTF-16 retval, omitting the curly braces and NUL.
+  CopyASCIItoUTF16(Substring(uuidString.get() + 1, NSID_LENGTH - 3), aRetVal);
+  MOZ_ASSERT(aRetVal.Length() == NSID_LENGTH - 3);
+}
+
 SubtleCrypto* Crypto::Subtle() {
   if (!mSubtle) {
     mSubtle = new SubtleCrypto(GetParentObject());

dom/base/Crypto.h

@@ -3,12 +3,13 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
 #ifndef mozilla_dom_Crypto_h
 #define mozilla_dom_Crypto_h
 
 #include "mozilla/dom/SubtleCrypto.h"
 #include "nsIGlobalObject.h"
-
+#include "nsString.h"
 #include "nsWrapperCache.h"
 #include "mozilla/dom/TypedArray.h"
 
@@ -31,6 +32,8 @@ class Crypto final : public nsISupports, public nsWrapperCache {
   void GetRandomValues(JSContext* aCx, const ArrayBufferView& aArray,
                        JS::MutableHandle<JSObject*> aRetval, ErrorResult& aRv);
 
+  void RandomUUID(nsAString& aRetVal);
+
   SubtleCrypto* Subtle();
 
   nsIGlobalObject* GetParentObject() const { return mParent; }

dom/webidl/Crypto.webidl

@@ -19,4 +19,7 @@ interface Crypto {
 
   [Throws]
   ArrayBufferView getRandomValues(ArrayBufferView array);
+
+  [SecureContext, Pref="dom.crypto.randomUUID.enabled"]
+  DOMString randomUUID();
 };

modules/libpref/init/StaticPrefList.yaml

@@ -1871,6 +1871,11 @@
   value: false
   mirror: always
 
+- name: dom.crypto.randomUUID.enabled
+  type: RelaxedAtomicBool
+  value: true
+  mirror: always
+
 # Is support for CSSPseudoElement enabled?
 - name: dom.css_pseudo_element.enabled
   type: bool