Bug 1846224 - Add a JavaScript per-realm locale override. r=jandem

Differential Revision: https://phabricator.services.mozilla.com/D184944

js/public/RealmOptions.h

@@ -18,6 +18,7 @@
 #include "jstypes.h"  // JS_PUBLIC_API
 
 #include "js/Class.h"  // JSTraceOp
+#include "js/RefCounted.h"
 
 struct JS_PUBLIC_API JSContext;
 class JS_PUBLIC_API JSObject;
@@ -60,6 +61,14 @@ enum class WeakRefSpecifier {
   EnabledWithoutCleanupSome
 };
 
+struct LocaleString : js::RefCounted<LocaleString> {
+  const char* chars_;
+
+  explicit LocaleString(const char* chars) : chars_(chars) {}
+
+  auto chars() const { return chars_; }
+};
+
 /**
  * RealmCreationOptions specifies options relevant to creating a new realm, that
  * are either immutable characteristics of that realm or that are discarded
@@ -259,6 +268,9 @@ class JS_PUBLIC_API RealmCreationOptions {
     return *this;
   }
 
+  RefPtr<LocaleString> locale() const { return locale_; }
+  RealmCreationOptions& setLocaleCopyZ(const char* locale);
+
   // Always use the fdlibm implementation of math functions instead of the
   // platform native libc implementations. Useful for fingerprinting protection
   // and cross-platform consistency.
@@ -282,6 +294,7 @@ class JS_PUBLIC_API RealmCreationOptions {
     Zone* zone_;
   };
   uint64_t profilerRealmID_ = 0;
+  RefPtr<LocaleString> locale_;
   WeakRefSpecifier weakRefs_ = WeakRefSpecifier::Disabled;
   bool invisibleToDebugger_ = false;
   bool preserveJitCode_ = false;

js/src/builtin/TestingFunctions.cpp

@@ -7813,34 +7813,12 @@ static bool SetDefaultLocale(JSContext* cx, unsigned argc, Value* vp) {
   }
 
   if (args[0].isString() && !args[0].toString()->empty()) {
-    Rooted<JSLinearString*> str(cx, args[0].toString()->ensureLinear(cx));
-    if (!str) {
-      return false;
-    }
-
-    if (!StringIsAscii(str)) {
-      ReportUsageErrorASCII(cx, callee,
-                            "First argument contains non-ASCII characters");
-      return false;
-    }
-
-    UniqueChars locale = JS_EncodeStringToASCII(cx, str);
+    RootedString str(cx, args[0].toString());
+    UniqueChars locale = StringToLocale(cx, callee, str);
     if (!locale) {
       return false;
     }
 
-    bool containsOnlyValidBCP47Characters =
-        mozilla::IsAsciiAlpha(locale[0]) &&
-        std::all_of(locale.get(), locale.get() + str->length(), [](auto c) {
-          return mozilla::IsAsciiAlphanumeric(c) || c == '-';
-        });
-
-    if (!containsOnlyValidBCP47Characters) {
-      ReportUsageErrorASCII(cx, callee,
-                            "First argument should be a BCP47 language tag");
-      return false;
-    }
-
     if (!JS_SetDefaultLocale(cx->runtime(), locale.get())) {
       ReportOutOfMemory(cx);
       return false;

js/src/builtin/TestingUtility.cpp

@@ -18,6 +18,7 @@
 #include "js/RootingAPI.h"          // JS::Rooted, JS::Handle
 #include "js/Utility.h"             // JS::UniqueChars
 #include "js/Value.h"               // JS::Value, JS::StringValue
+#include "vm/JSContext.h"           // JS::ReportUsageErrorASCII
 #include "vm/JSScript.h"
 
 bool js::ParseCompileOptions(JSContext* cx, JS::CompileOptions& options,
@@ -255,3 +256,36 @@ bool js::ParseDebugMetadata(JSContext* cx, JS::Handle<JSObject*> opts,
 
   return true;
 }
+
+JS::UniqueChars js::StringToLocale(JSContext* cx, JS::Handle<JSObject*> callee,
+                                   JS::Handle<JSString*> str_) {
+  Rooted<JSLinearString*> str(cx, str_->ensureLinear(cx));
+  if (!str) {
+    return nullptr;
+  }
+
+  if (!StringIsAscii(str)) {
+    ReportUsageErrorASCII(cx, callee,
+                          "First argument contains non-ASCII characters");
+    return nullptr;
+  }
+
+  UniqueChars locale = JS_EncodeStringToASCII(cx, str);
+  if (!locale) {
+    return nullptr;
+  }
+
+  bool containsOnlyValidBCP47Characters =
+      mozilla::IsAsciiAlpha(locale[0]) &&
+      std::all_of(locale.get(), locale.get() + str->length(), [](auto c) {
+        return mozilla::IsAsciiAlphanumeric(c) || c == '-';
+      });
+
+  if (!containsOnlyValidBCP47Characters) {
+    ReportUsageErrorASCII(cx, callee,
+                          "First argument should be a BCP47 language tag");
+    return nullptr;
+  }
+
+  return locale;
+}

js/src/builtin/TestingUtility.h

@@ -59,6 +59,10 @@ JSObject* CreateScriptPrivate(JSContext* cx,
     JS::MutableHandle<JS::Value> privateValue,
     JS::MutableHandle<JSString*> elementAttributeName);
 
+[[nodiscard]] JS::UniqueChars StringToLocale(JSContext* cx,
+                                             JS::Handle<JSObject*> callee,
+                                             JS::Handle<JSString*> str_);
+
 } /* namespace js */
 
 #endif /* builtin_TestingUtility_h */

js/src/jit-test/tests/resist-fingerprinting/locale.js

@@ -0,0 +1,19 @@
+// |jit-test| skip-if: typeof Intl === 'undefined'
+
+function test(locale, timeZone) {
+  let global = newGlobal({locale, forceUTC: true});
+
+  const constructors = ["Collator", "DateTimeFormat", "ListFormat",
+                        "NumberFormat", "PluralRules", "RelativeTimeFormat"];
+  for (const constructor of constructors) {
+    let intl = new global.Intl[constructor];
+    assertEq(intl.resolvedOptions().locale, locale);
+  }
+
+  const date = new global.Date(2012, 0, 10);
+  let tzRE = /\(([^\)]+)\)/;
+  assertEq(tzRE.exec(date)[1], timeZone)
+}
+
+test("de-CH", "Koordinierte Weltzeit");
+test("en", "Coordinated Universal Time");

js/src/jsapi.cpp

@@ -1722,6 +1722,24 @@ JS::RealmCreationOptions& JS::RealmCreationOptions::setCoopAndCoepEnabled(
   return *this;
 }
 
+JS::RealmCreationOptions& JS::RealmCreationOptions::setLocaleCopyZ(
+    const char* locale) {
+  const size_t size = strlen(locale) + 1;
+
+  AutoEnterOOMUnsafeRegion oomUnsafe;
+  char* memoryPtr = js_pod_malloc<char>(sizeof(LocaleString) + size);
+  if (!memoryPtr) {
+    oomUnsafe.crash("RealmCreationOptions::setLocaleCopyZ");
+  }
+
+  char* localePtr = memoryPtr + sizeof(LocaleString);
+  memcpy(localePtr, locale, size);
+
+  locale_ = new (memoryPtr) LocaleString(localePtr);
+
+  return *this;
+}
+
 const JS::RealmBehaviors& JS::RealmBehaviorsRef(JS::Realm* realm) {
   return realm->behaviors();
 }

js/src/jsdate.cpp

@@ -156,7 +156,8 @@ class DateTimeHelper {
   static double UTC(DateTimeInfo::ForceUTC forceUTC, double t);
   static JSString* timeZoneComment(JSContext* cx,
                                    DateTimeInfo::ForceUTC forceUTC,
-                                   double utcTime, double localTime);
+                                   const char* locale, double utcTime,
+                                   double localTime);
 #if !JS_HAS_INTL_API
   static size_t formatTime(DateTimeInfo::ForceUTC forceUTC, char* buf,
                            size_t buflen, const char* fmt, double utcTime,
@@ -2944,8 +2945,8 @@ static bool date_toJSON(JSContext* cx, unsigned argc, Value* vp) {
 #if JS_HAS_INTL_API
 JSString* DateTimeHelper::timeZoneComment(JSContext* cx,
                                           DateTimeInfo::ForceUTC forceUTC,
-                                          double utcTime, double localTime) {
-  const char* locale = cx->runtime()->getDefaultLocale();
+                                          const char* locale, double utcTime,
+                                          double localTime) {
   if (!locale) {
     JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
                               JSMSG_DEFAULT_LOCALE_ERROR);
@@ -3018,7 +3019,8 @@ size_t DateTimeHelper::formatTime(DateTimeInfo::ForceUTC forceUTC, char* buf,
 
 JSString* DateTimeHelper::timeZoneComment(JSContext* cx,
                                           DateTimeInfo::ForceUTC forceUTC,
-                                          double utcTime, double localTime) {
+                                          const char* locale, double utcTime,
+                                          double localTime) {
   char tzbuf[100];
 
   size_t tzlen =
@@ -3055,7 +3057,7 @@ JSString* DateTimeHelper::timeZoneComment(JSContext* cx,
 enum class FormatSpec { DateTime, Date, Time };
 
 static bool FormatDate(JSContext* cx, DateTimeInfo::ForceUTC forceUTC,
-                       double utcTime, FormatSpec format,
+                       const char* locale, double utcTime, FormatSpec format,
                        MutableHandleValue rval) {
   if (!std::isfinite(utcTime)) {
     rval.setString(cx->names().Invalid_Date_);
@@ -3091,8 +3093,8 @@ static bool FormatDate(JSContext* cx, DateTimeInfo::ForceUTC forceUTC,
     // also means the time zone string may not fit into Latin-1.
 
     // Get a time zone string from the OS or ICU to include as a comment.
-    timeZoneComment =
-        DateTimeHelper::timeZoneComment(cx, forceUTC, utcTime, localTime);
+    timeZoneComment = DateTimeHelper::timeZoneComment(cx, forceUTC, locale,
+                                                      utcTime, localTime);
     if (!timeZoneComment) {
       return false;
     }
@@ -3142,9 +3144,12 @@ static bool FormatDate(JSContext* cx, DateTimeInfo::ForceUTC forceUTC,
 }
 
 #if !JS_HAS_INTL_API
-static bool ToLocaleFormatHelper(JSContext* cx, DateTimeInfo::ForceUTC forceUTC,
-                                 double utcTime, const char* format,
-                                 MutableHandleValue rval) {
+static bool ToLocaleFormatHelper(JSContext* cx, DateObject* unwrapped,
+                                 const char* format, MutableHandleValue rval) {
+  DateTimeInfo::ForceUTC forceUTC = unwrapped->forceUTC();
+  const char* locale = unwrapped->realm()->getLocale();
+  double utcTime = unwrapped->UTCTime().toNumber();
+
   char buf[100];
   if (!std::isfinite(utcTime)) {
     strcpy(buf, "InvalidDate");
@@ -3157,7 +3162,8 @@ static bool ToLocaleFormatHelper(JSContext* cx, DateTimeInfo::ForceUTC forceUTC,
 
     /* If it failed, default to toString. */
     if (result_len == 0) {
-      return FormatDate(cx, forceUTC, utcTime, FormatSpec::DateTime, rval);
+      return FormatDate(cx, forceUTC, locale, utcTime, FormatSpec::DateTime,
+                        rval);
     }
 
     /* Hacked check against undesired 2-digit year 00/00/00 form. */
@@ -3212,9 +3218,7 @@ static bool date_toLocaleString(JSContext* cx, unsigned argc, Value* vp) {
 #  endif
       ;
 
-  return ToLocaleFormatHelper(cx, unwrapped->forceUTC(),
-                              unwrapped->UTCTime().toNumber(), format,
-                              args.rval());
+  return ToLocaleFormatHelper(cx, unwrapped, format, args.rval());
 }
 
 static bool date_toLocaleDateString(JSContext* cx, unsigned argc, Value* vp) {
@@ -3240,9 +3244,7 @@ static bool date_toLocaleDateString(JSContext* cx, unsigned argc, Value* vp) {
 #  endif
       ;
 
-  return ToLocaleFormatHelper(cx, unwrapped->forceUTC(),
-                              unwrapped->UTCTime().toNumber(), format,
-                              args.rval());
+  return ToLocaleFormatHelper(cx, unwrapped, format, args.rval());
 }
 
 static bool date_toLocaleTimeString(JSContext* cx, unsigned argc, Value* vp) {
@@ -3256,9 +3258,7 @@ static bool date_toLocaleTimeString(JSContext* cx, unsigned argc, Value* vp) {
     return false;
   }
 
-  return ToLocaleFormatHelper(cx, unwrapped->forceUTC(),
-                              unwrapped->UTCTime().toNumber(), "%X",
-                              args.rval());
+  return ToLocaleFormatHelper(cx, unwrapped, "%X", args.rval());
 }
 #endif /* !JS_HAS_INTL_API */
 
@@ -3272,8 +3272,9 @@ static bool date_toTimeString(JSContext* cx, unsigned argc, Value* vp) {
     return false;
   }
 
-  return FormatDate(cx, unwrapped->forceUTC(), unwrapped->UTCTime().toNumber(),
-                    FormatSpec::Time, args.rval());
+  return FormatDate(cx, unwrapped->forceUTC(), unwrapped->realm()->getLocale(),
+                    unwrapped->UTCTime().toNumber(), FormatSpec::Time,
+                    args.rval());
 }
 
 static bool date_toDateString(JSContext* cx, unsigned argc, Value* vp) {
@@ -3286,8 +3287,9 @@ static bool date_toDateString(JSContext* cx, unsigned argc, Value* vp) {
     return false;
   }
 
-  return FormatDate(cx, unwrapped->forceUTC(), unwrapped->UTCTime().toNumber(),
-                    FormatSpec::Date, args.rval());
+  return FormatDate(cx, unwrapped->forceUTC(), unwrapped->realm()->getLocale(),
+                    unwrapped->UTCTime().toNumber(), FormatSpec::Date,
+                    args.rval());
 }
 
 static bool date_toSource(JSContext* cx, unsigned argc, Value* vp) {
@@ -3323,8 +3325,9 @@ bool date_toString(JSContext* cx, unsigned argc, Value* vp) {
     return false;
   }
 
-  return FormatDate(cx, unwrapped->forceUTC(), unwrapped->UTCTime().toNumber(),
-                    FormatSpec::DateTime, args.rval());
+  return FormatDate(cx, unwrapped->forceUTC(), unwrapped->realm()->getLocale(),
+                    unwrapped->UTCTime().toNumber(), FormatSpec::DateTime,
+                    args.rval());
 }
 
 bool js::date_valueOf(JSContext* cx, unsigned argc, Value* vp) {
@@ -3480,8 +3483,8 @@ static bool NewDateObject(JSContext* cx, const CallArgs& args, ClippedTime t) {
 }
 
 static bool ToDateString(JSContext* cx, const CallArgs& args, ClippedTime t) {
-  return FormatDate(cx, ForceUTC(cx->realm()), t.toDouble(),
-                    FormatSpec::DateTime, args.rval());
+  return FormatDate(cx, ForceUTC(cx->realm()), cx->realm()->getLocale(),
+                    t.toDouble(), FormatSpec::DateTime, args.rval());
 }
 
 static bool DateNoArguments(JSContext* cx, const CallArgs& args) {

js/src/shell/js.cpp

@@ -6776,6 +6776,9 @@ static bool WrapWithProto(JSContext* cx, unsigned argc, Value* vp) {
 }
 
 static bool NewGlobal(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject callee(cx, &args.callee());
+
   JS::RealmOptions options;
   JS::RealmCreationOptions& creationOptions = options.creationOptions();
   JS::RealmBehaviors& behaviors = options.behaviors();
@@ -6794,7 +6797,6 @@ static bool NewGlobal(JSContext* cx, unsigned argc, Value* vp) {
 
   JS::AutoHoldPrincipals principals(cx);
 
-  CallArgs args = CallArgsFromVp(argc, vp);
   if (args.length() == 1 && args[0].isObject()) {
     RootedObject opts(cx, &args[0].toObject());
     RootedValue v(cx);
@@ -6914,6 +6916,18 @@ static bool NewGlobal(JSContext* cx, unsigned argc, Value* vp) {
     if (v.isBoolean()) {
       creationOptions.setAlwaysUseFdlibm(v.toBoolean());
     }
+
+    if (!JS_GetProperty(cx, opts, "locale", &v)) {
+      return false;
+    }
+    if (v.isString()) {
+      RootedString str(cx, v.toString());
+      UniqueChars locale = StringToLocale(cx, callee, str);
+      if (!locale) {
+        return false;
+      }
+      creationOptions.setLocaleCopyZ(locale.get());
+    }
   }
 
   if (!CheckRealmOptions(cx, options, principals.get())) {

js/src/vm/Realm.cpp

@@ -488,6 +488,14 @@ void Realm::clearScriptCounts() { zone()->clearScriptCounts(this); }
 
 void Realm::clearScriptLCov() { zone()->clearScriptLCov(this); }
 
+const char* Realm::getLocale() const {
+  if (RefPtr<LocaleString> locale = creationOptions_.locale()) {
+    return locale->chars();
+  }
+
+  return runtime_->getDefaultLocale();
+}
+
 void ObjectRealm::addSizeOfExcludingThis(
     mozilla::MallocSizeOf mallocSizeOf, size_t* innerViewsArg,
     size_t* objectMetadataTablesArg,

js/src/vm/Realm.h

@@ -673,6 +673,9 @@ class JS::Realm : public JS::shadow::Realm {
 
   bool shouldCaptureStackForThrow();
 
+  // Returns the locale for this realm. (Pointer must NOT be freed!)
+  const char* getLocale() const;
+
   // Initializes randomNumberGenerator if needed.
   mozilla::non_crypto::XorShift128PlusRNG& getOrCreateRandomNumberGenerator();
 

js/src/vm/SelfHosting.cpp

@@ -1593,7 +1593,7 @@ static bool intrinsic_RuntimeDefaultLocale(JSContext* cx, unsigned argc,
   CallArgs args = CallArgsFromVp(argc, vp);
   MOZ_ASSERT(args.length() == 0);
 
-  const char* locale = cx->runtime()->getDefaultLocale();
+  const char* locale = cx->realm()->getLocale();
   if (!locale) {
     JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
                               JSMSG_DEFAULT_LOCALE_ERROR);
@@ -1622,7 +1622,7 @@ static bool intrinsic_IsRuntimeDefaultLocale(JSContext* cx, unsigned argc,
     return true;
   }
 
-  const char* locale = cx->runtime()->getDefaultLocale();
+  const char* locale = cx->realm()->getLocale();
   if (!locale) {
     JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
                               JSMSG_DEFAULT_LOCALE_ERROR);