Purge QRegExp use in QDateTime's rfcDateImpl()

Replace with a parser which actually does the job right, fixing
various infelicities in the parsing in the process.
Make the parser strict about formatting.

Adjusted tests to match. Fixed some QTime invalidity tests to each
test only one invalidity at a time (the invalid year and day tests
also used an invalid month).

[ChangeLog][QtCore][QDateTime] The parser for the Qt::RFC2822Date
format is now stricter, requiring the text to exactly match the form
of one of the relevant formats. A valid date or time will still be
parsed, even if the other part of the content is invalid, as long as
it (and any offset, if present) has the right form. In particular, the
parser now rejects texts with trailing cruft (other than space).

Fixes: QTBUG-80038
Change-Id: Id25675afd75f82f6351f20e79f0154f3ceda35ac
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 126 insertions, 28 deletions

diff --git a/src/corelib/time/qdatetime.cpp b/src/corelib/time/qdatetime.cpp
index e116e539b9..14e36b59ca 100644
--- a/src/corelib/time/qdatetime.cpp
+++ b/src/corelib/time/qdatetime.cpp
@@ -51,7 +51,6 @@
 #if QT_CONFIG(timezone)
 #include "qtimezoneprivate_p.h"
 #endif
-#include "qregexp.h"
 #include "qdebug.h"
 #ifndef Q_OS_WIN
 #include <locale.h>
@@ -135,8 +134,6 @@ static int qt_monthNumberFromShortName(QStringView shortName)
     }
     return -1;
 }
-static int qt_monthNumberFromShortName(const QString &shortName)
-{ return qt_monthNumberFromShortName(QStringView(shortName)); }
 
 static int fromShortMonthName(QStringView monthName, int year)
 {
@@ -153,43 +150,144 @@ static int fromShortMonthName(QStringView monthName, int year)
 }
 #endif // textdate
 
-#if QT_CONFIG(datestring)
+#if QT_CONFIG(datestring) // depends on, so implies, textdate
 struct ParsedRfcDateTime {
     QDate date;
     QTime time;
     int utcOffset;
 };
 
+static int shortDayFromName(QStringView name)
+{
+    const char16_t shortDayNames[] = u"MonTueWedThuFriSatSun";
+    for (int i = 0; i < 7; i++) {
+        if (name == QStringView(shortDayNames + 3 * i, 3))
+            return i + 1;
+    }
+    return 0;
+}
+
 static ParsedRfcDateTime rfcDateImpl(const QString &s)
 {
+    // Matches "[ddd,] dd MMM yyyy[ hh:mm[:ss]] [±hhmm]" - correct RFC 822, 2822, 5322 format -
+    // or           "ddd MMM dd[ hh:mm:ss] yyyy [±hhmm]" - permissive RFC 850, 1036 (read only)
     ParsedRfcDateTime result;
 
-    // Matches "[ddd,] dd MMM yyyy[ hh:mm[:ss]] [±hhmm]" - correct RFC 822, 2822, 5322 format
-    QRegExp rex(QStringLiteral("^[ \\t]*(?:[A-Z][a-z]+,)?[ \\t]*(\\d{1,2})[ \\t]+([A-Z][a-z]+)[ \\t]+(\\d\\d\\d\\d)(?:[ \\t]+(\\d\\d):(\\d\\d)(?::(\\d\\d))?)?[ \\t]*(?:([+-])(\\d\\d)(\\d\\d))?"));
-    if (s.indexOf(rex) == 0) {
-        const QStringList cap = rex.capturedTexts();
-        result.date = QDate(cap[3].toInt(), qt_monthNumberFromShortName(cap[2]), cap[1].toInt());
-        if (!cap[4].isEmpty())
-            result.time = QTime(cap[4].toInt(), cap[5].toInt(), cap[6].toInt());
-        const bool positiveOffset = (cap[7] == QLatin1String("+"));
-        const int hourOffset = cap[8].toInt();
-        const int minOffset = cap[9].toInt();
-        result.utcOffset = ((hourOffset * 60 + minOffset) * (positiveOffset ? 60 : -60));
-    } else {
-        // Matches "ddd MMM dd[ hh:mm:ss] yyyy [±hhmm]" - permissive RFC 850, 1036 (read only)
-        QRegExp rex(QStringLiteral("^[ \\t]*[A-Z][a-z]+[ \\t]+([A-Z][a-z]+)[ \\t]+(\\d\\d)(?:[ \\t]+(\\d\\d):(\\d\\d):(\\d\\d))?[ \\t]+(\\d\\d\\d\\d)[ \\t]*(?:([+-])(\\d\\d)(\\d\\d))?"));
-        if (s.indexOf(rex) == 0) {
-            const QStringList cap = rex.capturedTexts();
-            result.date = QDate(cap[6].toInt(), qt_monthNumberFromShortName(cap[1]), cap[2].toInt());
-            if (!cap[3].isEmpty())
-                result.time = QTime(cap[3].toInt(), cap[4].toInt(), cap[5].toInt());
-            const bool positiveOffset = (cap[7] == QLatin1String("+"));
-            const int hourOffset = cap[8].toInt();
-            const int minOffset = cap[9].toInt();
-            result.utcOffset = ((hourOffset * 60 + minOffset) * (positiveOffset ? 60 : -60));
+    auto words = s.splitRef(QLatin1Char(' '), QString::SkipEmptyParts);
+    if (words.size() < 3 || words.size() > 6)
+        return result;
+    const QChar colon(QLatin1Char(':'));
+    const QLocale C = QLocale::c();
+    bool ok = true;
+    QDate date;
+
+    const auto isShortName = [](QStringView name) {
+        return (name.length() == 3 && name.at(0).isUpper()
+                && name.at(1).isLower() && name.at(2).isLower());
+    };
+
+    /* Reject entirely (return) if the string is malformed; however, if the date
+     * is merely invalid, (break, so as to) go on to parsing of the time.
+     */
+    int yearIndex;
+    do { // "loop" so that we can use break on merely invalid, but "right shape" date.
+        QStringView dayName;
+        bool rfcX22 = true;
+        if (words.at(0).endsWith(QLatin1Char(','))) {
+            dayName = words.takeFirst().chopped(1);
+        } else if (!words.at(0).at(0).isDigit()) {
+            dayName = words.takeFirst();
+            rfcX22 = false;
+        } // else: dayName is not specified (so we can only be RFC *22)
+        if (words.size() < 3 || words.size() > 5)
+            return result;
+
+        // Don't break before setting yearIndex.
+        int dayIndex, monthIndex;
+        if (rfcX22) {
+            // dd MMM yyyy [hh:mm[:ss]] [±hhmm]
+            dayIndex = 0;
+            monthIndex = 1;
+            yearIndex = 2;
+        } else {
+            // MMM dd[ hh:mm:ss] yyyy [±hhmm]
+            dayIndex = 1;
+            monthIndex = 0;
+            yearIndex = words.size() > 3 && words.at(2).contains(colon) ? 3 : 2;
         }
+
+        int dayOfWeek = 0;
+        if (!dayName.isEmpty()) {
+            if (!isShortName(dayName))
+                return result;
+            dayOfWeek = shortDayFromName(dayName);
+            if (!dayOfWeek)
+                break;
+        }
+
+        const int day = words.at(dayIndex).toInt(&ok);
+        if (!ok)
+            return result;
+        const int year = words.at(yearIndex).toInt(&ok);
+        if (!ok)
+            return result;
+        const QStringView monthName = words.at(monthIndex);
+        if (!isShortName(monthName))
+            return result;
+        int month = fromShortMonthName(monthName, year);
+        if (month < 0)
+            break;
+
+        date = QDate(year, month, day);
+        if (dayOfWeek && date.dayOfWeek() != dayOfWeek)
+            date = QDate();
+    } while (false);
+    words.remove(yearIndex);
+    words.remove(0, 2); // month and day-of-month, in some order
+
+    // Time: [hh:mm[:ss]]
+    QTime time;
+    if (words.size() && words.at(0).contains(colon)) {
+        const QStringView when = words.takeFirst();
+        if (when.at(2) != colon || (when.size() == 8 ? when.at(5) != colon : when.size() > 5))
+            return result;
+        const int hour = C.toInt(when.left(2), &ok);
+        if (!ok)
+            return result;
+        const int minute = C.toInt(when.mid(3, 2), &ok);
+        if (!ok)
+            return result;
+        const auto secs = when.size() == 8 ? C.toInt(when.right(2), &ok) : 0;
+        if (!ok)
+            return result;
+        time = QTime(hour, minute, secs);
+    }
+
+    // Offset: [±hhmm]
+    int offset = 0;
+    if (words.size()) {
+        const QStringView zone = words.takeFirst();
+        if (words.size() || !(zone.size() == 3 || zone.size() == 5))
+            return result;
+        bool negate = false;
+        if (zone.at(0) == QLatin1Char('-'))
+            negate = true;
+        else if (zone.at(0) != QLatin1Char('+'))
+            return result;
+        const int hour = C.toInt(zone.mid(1, 2), &ok);
+        if (!ok)
+            return result;
+        const auto minute = zone.size() > 3 ? C.toInt(zone.mid(3, 2), &ok) : 0;
+        if (!ok)
+            return result;
+        offset = (hour * 60 + minute) * 60;
+        if (negate)
+            offset = -offset;
     }
 
+    result.date = date;
+    result.time = time;
+    result.utcOffset = offset;
     return result;
 }
 #endif // datestring
@@ -5285,7 +5383,7 @@ QT_WARNING_POP
             isoString.chop(1); // trim 'Z'
         } else {
             // the loop below is faster but functionally equal to:
-            // const int signIndex = isoString.indexOf(QRegExp(QStringLiteral("[+-]")));
+            // const int signIndex = isoString.indexOf(QRegulargExpression(QStringLiteral("[+-]")));
             int signIndex = isoString.size() - 1;
             Q_ASSERT(signIndex >= 0);
             bool found = false;