QSslSocket: fix connection to a international domain name

RFC6125 section 6.4.2 specify we need to convert the IDN to ascii
before comparison. Note that we don't need to toLower anymore
because toAce takes care of it.

Section 7.2 recommands that we dod not attempt to check for wildcard
character embedded within the A-labels or U-labels of an
internationalized domain name. So we reject names that contiains a
'*' but starts with 'xn--'.

Change-Id: Ib0830520a1f82bbf9fd11818718277a479527ee3
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

2 files changed, 21 insertions, 7 deletions

diff --git a/src/network/ssl/qsslsocket.cpp b/src/network/ssl/qsslsocket.cpp
index 2fc779b257..166907780b 100644
--- a/src/network/ssl/qsslsocket.cpp
+++ b/src/network/ssl/qsslsocket.cpp
@@ -326,6 +326,7 @@
 #include <QtCore/qdebug.h>
 #include <QtCore/qdir.h>
 #include <QtCore/qmutex.h>
+#include <QtCore/qurl.h>
 #include <QtCore/qelapsedtimer.h>
 #include <QtNetwork/qhostaddress.h>
 #include <QtNetwork/qhostinfo.h>
@@ -2673,31 +2674,35 @@ QSharedPointer<QSslContext> QSslSocketPrivate::sslContext(QSslSocket *socket)
 
 bool QSslSocketPrivate::isMatchingHostname(const QSslCertificate &cert, const QString &peerName)
 {
-    const QString lowerPeerName = peerName.toLower();
+    const QString lowerPeerName = QString::fromLatin1(QUrl::toAce(peerName));
     const QStringList commonNames = cert.subjectInfo(QSslCertificate::CommonName);
 
     for (const QString &commonName : commonNames) {
-        if (isMatchingHostname(commonName.toLower(), lowerPeerName))
+        if (isMatchingHostname(commonName, lowerPeerName))
             return true;
     }
 
     const auto subjectAlternativeNames = cert.subjectAlternativeNames();
     const auto altNames = subjectAlternativeNames.equal_range(QSsl::DnsEntry);
     for (auto it = altNames.first; it != altNames.second; ++it) {
-        if (isMatchingHostname(it->toLower(), lowerPeerName))
+        if (isMatchingHostname(*it, lowerPeerName))
             return true;
     }
 
     return false;
 }
 
+/*! \internal
+   Checks if the certificate's name \a cn matches the \a hostname.
+   \a hostname must be normalized in ASCII-Compatible Encoding, but \a cn is not normalized
+ */
 bool QSslSocketPrivate::isMatchingHostname(const QString &cn, const QString &hostname)
 {
     int wildcard = cn.indexOf(QLatin1Char('*'));
 
     // Check this is a wildcard cert, if not then just compare the strings
     if (wildcard < 0)
-        return cn == hostname;
+        return QLatin1String(QUrl::toAce(cn)) == hostname;
 
     int firstCnDot = cn.indexOf(QLatin1Char('.'));
     int secondCnDot = cn.indexOf(QLatin1Char('.'), firstCnDot+1);
@@ -2714,13 +2719,21 @@ bool QSslSocketPrivate::isMatchingHostname(const QString &cn, const QString &hos
     if (cn.lastIndexOf(QLatin1Char('*')) != wildcard)
         return false;
 
+    // Reject wildcard character embedded within the A-labels or U-labels of an internationalized
+    // domain name (RFC6125 section 7.2)
+    if (cn.startsWith(QLatin1String("xn--"), Qt::CaseInsensitive))
+        return false;
+
     // Check characters preceding * (if any) match
-    if (wildcard && (hostname.leftRef(wildcard) != cn.leftRef(wildcard)))
+    if (wildcard && hostname.leftRef(wildcard).compare(cn.leftRef(wildcard), Qt::CaseInsensitive) != 0)
         return false;
 
     // Check characters following first . match
-    if (hostname.midRef(hostname.indexOf(QLatin1Char('.'))) != cn.midRef(firstCnDot))
+    int hnDot = hostname.indexOf(QLatin1Char('.'));
+    if (hostname.midRef(hnDot + 1) != cn.midRef(firstCnDot + 1)
+        && hostname.midRef(hnDot + 1) != QLatin1String(QUrl::toAce(cn.mid(firstCnDot + 1)))) {
         return false;
+    }
 
     // Check if the hostname is an IP address, if so then wildcards are not allowed
     QHostAddress addr(hostname);
diff --git a/src/network/ssl/qsslsocket_p.h b/src/network/ssl/qsslsocket_p.h
index cec61d07c1..aec3437422 100644
--- a/src/network/ssl/qsslsocket_p.h
+++ b/src/network/ssl/qsslsocket_p.h
@@ -151,7 +151,8 @@ public:
                                          QRegExp::PatternSyntax syntax);
     static void addDefaultCaCertificate(const QSslCertificate &cert);
     static void addDefaultCaCertificates(const QList<QSslCertificate> &certs);
-    static bool isMatchingHostname(const QSslCertificate &cert, const QString &peerName);
+    Q_AUTOTEST_EXPORT static bool isMatchingHostname(const QSslCertificate &cert,
+                                                     const QString &peerName);
     Q_AUTOTEST_EXPORT static bool isMatchingHostname(const QString &cn, const QString &hostname);
 
 #if defined(Q_OS_WIN) && !defined(Q_OS_WINRT)