Bug 1870570 - Only allow exact matches for time zone and AM/PM keywords r=arai

Differential Revision: https://phabricator.services.mozilla.com/D196941

js/src/jsdate.cpp

@@ -1093,6 +1093,23 @@ bool IsPrefixOfKeyword(const CharT* s, size_t len, const char* keyword) {
   return len == 0;
 }
 
+template <typename CharT>
+bool MatchesKeyword(const CharT* s, size_t len, const char* keyword) {
+  while (len > 0) {
+    MOZ_ASSERT(IsAsciiAlpha(*s));
+    MOZ_ASSERT(IsAsciiLowercaseAlpha(*keyword));
+
+    if (unicode::ToLowerCase(static_cast<Latin1Char>(*s)) != *keyword) {
+      return false;
+    }
+
+    ++s, ++keyword;
+    --len;
+  }
+
+  return *keyword == '\0';
+}
+
 static constexpr const char* const month_prefixes[] = {
     "jan", "feb", "mar", "apr", "may", "jun",
     "jul", "aug", "sep", "oct", "nov", "dec",
@@ -1318,19 +1335,15 @@ struct CharsAndAction {
   int action;
 };
 
+static constexpr const char* const days_of_week[] = {
+    "monday", "tuesday",  "wednesday", "thursday",
+    "friday", "saturday", "sunday"};
+
 static constexpr CharsAndAction keywords[] = {
     // clang-format off
   // AM/PM
   { "am", -1 },
   { "pm", -2 },
-  // Days of week.
-  { "monday", 0 },
-  { "tuesday", 0 },
-  { "wednesday", 0 },
-  { "thursday", 0 },
-  { "friday", 0 },
-  { "saturday", 0 },
-  { "sunday", 0 },
   // Time zone abbreviations.
   { "gmt", 10000 + 0 },
   { "z", 10000 + 0 },
@@ -1650,6 +1663,21 @@ static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
         return false;
       }
 
+      // Completely ignore days of the week, and don't derive any semantics
+      // from them.
+      bool isLateWeekday = false;
+      for (const char* weekday : days_of_week) {
+        if (IsPrefixOfKeyword(s + start, index - start, weekday)) {
+          isLateWeekday = true;
+          seenLateWeekday = true;
+          break;
+        }
+      }
+      if (isLateWeekday) {
+        prevc = 0;
+        continue;
+      }
+
       size_t k = std::size(keywords);
       while (k-- > 0) {
         // Record a month if it is a month name. Note that some numbers are
@@ -1692,21 +1720,13 @@ static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
 
         const CharsAndAction& keyword = keywords[k];
 
-        // If the field isn't a prefix of the keyword (an exact match is *not*
-        // required), try the next one.
-        if (!IsPrefixOfKeyword(s + start, index - start, keyword.chars)) {
+        // If the field doesn't match the keyword, try the next one.
+        if (!MatchesKeyword(s + start, index - start, keyword.chars)) {
           continue;
         }
 
         int action = keyword.action;
 
-        // Completely ignore days of the week, and don't derive any semantics
-        // from them.
-        if (action == 0) {
-          seenLateWeekday = true;
-          break;
-        }
-
         if (action == 10000) {
           seenGmtAbbr = true;
         }

js/src/tests/non262/Date/parse-keywords.js

@@ -0,0 +1,49 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* 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/. */
+
+const accepted = {
+  "Sep 26 1995 UT": "1995-09-26T00:00:00Z",
+  "Sep 26 1995 UTC": "1995-09-26T00:00:00Z",
+  "Sep 26 1995 GMT": "1995-09-26T00:00:00Z",
+  "Sep 26 1995 EST": "1995-09-26T00:00:00-0500",
+  "Sep 26 1995 est": "1995-09-26T00:00:00-0500",
+  "Sep 26 1995 10:00 am": "1995-09-26T10:00:00",
+  "Sep 26 1995 10:00 AM": "1995-09-26T10:00:00",
+  "Sep 26 1995 10:00 pm": "1995-09-26T22:00:00",
+  "Sep 26 Thurs 1995 Mon 10:thursday:00": "1995-09-26T10:00:00",
+};
+const rejected = [
+  "Sep 26 1995 G",
+  "Sep 26 1995 GM",
+  "Sep 26 1995 E",
+  "Sep 26 1995 ES",
+  "Sep 26 1995 10:00 a",
+  "Sep 26 1995 10:00 p",
+];
+
+for (const [test, expected] of Object.entries(accepted)) {
+  const testDate = new Date(test);
+  const expectedDate = new Date(expected);
+
+  assertEq(
+    false, isNaN(testDate),
+    `${test} should be accepted.`
+  );
+
+  assertEq(
+    testDate.getTime(), expectedDate.getTime(),
+    `"${test}" should be ${expectedDate} (got ${testDate}).`
+  );
+}
+
+for (const reject of rejected) {
+  assertEq(
+    true, isNaN(new Date(reject)),
+    `"${reject}" should be rejected.`
+  );
+}
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);