ASN1: speed up parsing of certificate timestamps

By parsing QDate and QTime separately it will internally parse the
values as-if-by UTC. This means we avoid the overhead of figuring out
what the local timezone is repeatedly for each certificate.

On Windows, with Schannel, this brings QAsn1Element::toDateTime
from consuming more than 97% of the test time to below 10%.
The test being tst_QSslSocket::systemCaCertificates. It also goes
from taking 1 minute in debug, to 1 second.

As a drive-by: add a (currently) failing test for Feb 29 2000, which
fails because we decode the date as 1900 before adjusting it to 2000.
But there is no 1900-02-29, so it returns an invalid date. As spotted
by Eddy.

Pick-to: 6.6 6.5
Change-Id: Iefa73a01d710129faf6412c4fa8bc2b5d7c98bbb
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

2 files changed, 18 insertions, 11 deletions

diff --git a/src/plugins/tls/shared/qasn1element.cpp b/src/plugins/tls/shared/qasn1element.cpp
index 63351947f0..8d4d908e53 100644
--- a/src/plugins/tls/shared/qasn1element.cpp
+++ b/src/plugins/tls/shared/qasn1element.cpp
@@ -6,6 +6,7 @@
 
 #include <QtCore/qdatastream.h>
 #include <QtCore/qdatetime.h>
+#include <QtCore/qtimezone.h>
 #include <QtCore/qlist.h>
 #include <QDebug>
 #include <private/qtools_p.h>
@@ -224,15 +225,10 @@ QDateTime QAsn1Element::toDateTime() const
         return result;
 
     if (mType == UtcTimeType && mValue.size() == 13) {
-        result = QDateTime::fromString(QString::fromLatin1(mValue),
-                                       u"yyMMddHHmmsst");
-        if (!result.isValid())
+        const QLatin1StringView inputView(mValue);
+        QDate date = QDate::fromString(inputView.first(6), u"yyMMdd");
+        if (!date.isValid())
             return result;
-
-        Q_ASSERT(result.timeSpec() == Qt::UTC);
-
-        QDate date = result.date();
-
         // RFC 2459:
         //   Where YY is greater than or equal to 50, the year shall be
         //   interpreted as 19YY; and
@@ -242,10 +238,15 @@ QDateTime QAsn1Element::toDateTime() const
         // QDateTime interprets the 'yy' format as 19yy, so we may need to adjust
         // the year (bring it in the [1950, 2049] range).
         if (date.year() < 1950)
-            result.setDate(date.addYears(100));
+            date = date.addYears(100);
+
+        Q_ASSERT(date.year() >= 1950);
+        Q_ASSERT(date.year() <= 2049);
 
-        Q_ASSERT(result.date().year() >= 1950);
-        Q_ASSERT(result.date().year() <= 2049);
+        QTime time = QTime::fromString(inputView.sliced(6, 6), u"HHmmss");
+        if (!time.isValid())
+            return result;
+        result = QDateTime(date, time, QTimeZone::UTC);
     } else if (mType == GeneralizedTimeType && mValue.size() == 15) {
         result = QDateTime::fromString(QString::fromLatin1(mValue),
                                        u"yyyyMMddHHmmsst");
diff --git a/tests/auto/network/ssl/qasn1element/tst_qasn1element.cpp b/tests/auto/network/ssl/qasn1element/tst_qasn1element.cpp
index eb614551a9..aa126f0f1a 100644
--- a/tests/auto/network/ssl/qasn1element/tst_qasn1element.cpp
+++ b/tests/auto/network/ssl/qasn1element/tst_qasn1element.cpp
@@ -121,6 +121,9 @@ void tst_QAsn1Element::dateTime_data()
     QTest::newRow("UTCTime - year 2000")
         << QByteArray::fromHex("170d3030313232343035353530305a")
         << QDateTime(QDate(2000, 12, 24), QTime(5, 55), QTimeZone::UTC);
+    QTest::newRow("UTCTime - leap day year 2000")
+        << QByteArray::fromHex("170d3030303232393035353530305a")
+        << QDateTime(QDate(2000, 2, 29), QTime(5, 55), QTimeZone::UTC);
     QTest::newRow("UTCTime - year 2049")
         << QByteArray::fromHex("170d3439313232343035353530305a")
         << QDateTime(QDate(2049, 12, 24), QTime(5, 55), QTimeZone::UTC);
@@ -163,6 +166,9 @@ void tst_QAsn1Element::dateTime()
 
     QAsn1Element elem;
     QVERIFY(elem.read(encoded));
+    QEXPECT_FAIL("UTCTime - leap day year 2000",
+                 "We decode as 1900, and then adjust to 2000. But there was no leap day in 1900!",
+                 Continue);
     QCOMPARE(elem.toDateTime(), value);
 }