135 lines
5.9 KiB
Diff
135 lines
5.9 KiB
Diff
Security advisory: Fraudulent certificates
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Background:
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Recently a group of people managed to get fraudulent SSL certificates signed
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by a Certificate Authority (CA).
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These certificates potentially enable their owners to pretend to be other
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entities on the Web; the attackers can present valid certificates for e.g.
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mail.google.com, login.yahoo.com and login.live.com, among others.
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The patch below solves this problem by blacklisting those fake certificates
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and aborting an SSL handshake with entities that present these certificates.
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The patch applies to all 4.6 and 4.7 versions, and should be applied to all Qt
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4.6.x and 4.7.x versions; upcoming Qt releases will contain a fix for this
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problem.
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More technical background:
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In order to trick a user into establishing an SSL connection to a site using
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one of those fake certificates, in addition to controlling the certificate, an
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attacker would need to either control the DNS server used by the victim, or
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have control over a proxy that the victim uses. That way, the attacker could
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trick the victim to connect to the attacker?s site and then present the user
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with a valid certificate.
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One obvious question now is: Should those certificates not just be revoked,
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which would solve the problem?
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First, they have been revoked by the affected Certificate Authority (see above
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link).
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However, the problem in this case, and probably part of the reason why most
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browser vendors release new versions blacklisting those certificates, is that
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by default browsers do not treat invalid responses from an OCSP server (a
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server used for checking the revocation status of a certificate) as fatal, and
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will allow the SSL connection to proceed anyway. Qt itself does not support
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OCSP yet, which makes blacklisting the certificates the only valid option (now
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would be a good moment to vote on the task for implementing OCSP in Qt); since
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Qt is relying on the system root certificates since version 4.7, it cannot
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control the root certificates that Qt trusts automatically anymore.
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http://www.comodo.com/Comodo-Fraud-Incident-2011-03-23.html
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http://qt.nokia.com/files/qt-patches/blacklist-fraudulent-comodo-certificates-patch.diff/view
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diff --git a/src/network/ssl/qsslcertificate.cpp b/src/network/ssl/qsslcertificate.cpp
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index 618ac79..a5cdf01 100644
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--- a/src/network/ssl/qsslcertificate.cpp
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+++ b/src/network/ssl/qsslcertificate.cpp
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@@ -219,17 +219,19 @@ bool QSslCertificate::isNull() const
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Returns true if this certificate is valid; otherwise returns
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false.
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- Note: Currently, this function only checks that the current
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+ Note: Currently, this function checks that the current
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data-time is within the date-time range during which the
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- certificate is considered valid. No other checks are
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- currently performed.
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+ certificate is considered valid, and checks that the
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+ certificate is not in a blacklist of fraudulent certificates.
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\sa isNull()
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*/
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bool QSslCertificate::isValid() const
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{
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const QDateTime currentTime = QDateTime::currentDateTime();
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- return currentTime >= d->notValidBefore && currentTime <= d->notValidAfter;
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+ return currentTime >= d->notValidBefore &&
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+ currentTime <= d->notValidAfter &&
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+ ! QSslCertificatePrivate::isBlacklisted(*this);
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}
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/*!
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@@ -798,6 +800,30 @@ QList<QSslCertificate> QSslCertificatePrivate::certificatesFromDer(const QByteAr
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return certificates;
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}
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+// These certificates are known to be fraudulent and were created during the comodo
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+// compromise. See http://www.comodo.com/Comodo-Fraud-Incident-2011-03-23.html
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+static const char *certificate_blacklist[] = {
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+ "04:7e:cb:e9:fc:a5:5f:7b:d0:9e:ae:36:e1:0c:ae:1e",
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+ "f5:c8:6a:f3:61:62:f1:3a:64:f5:4f:6d:c9:58:7c:06",
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+ "d7:55:8f:da:f5:f1:10:5b:b2:13:28:2b:70:77:29:a3",
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+ "39:2a:43:4f:0e:07:df:1f:8a:a3:05:de:34:e0:c2:29",
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+ "3e:75:ce:d4:6b:69:30:21:21:88:30:ae:86:a8:2a:71",
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+ "e9:02:8b:95:78:e4:15:dc:1a:71:0a:2b:88:15:44:47",
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+ "92:39:d5:34:8f:40:d1:69:5a:74:54:70:e1:f2:3f:43",
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+ "b0:b7:13:3e:d0:96:f9:b5:6f:ae:91:c8:74:bd:3a:c0",
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+ "d8:f3:5f:4e:b7:87:2b:2d:ab:06:92:e3:15:38:2f:b0",
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+ 0
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+};
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+
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+bool QSslCertificatePrivate::isBlacklisted(const QSslCertificate &certificate)
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+{
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+ for (int a = 0; certificate_blacklist[a] != 0; a++) {
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+ if (certificate.serialNumber() == certificate_blacklist[a])
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+ return true;
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+ }
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+ return false;
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+}
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+
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#ifndef QT_NO_DEBUG_STREAM
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QDebug operator<<(QDebug debug, const QSslCertificate &certificate)
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{
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diff --git a/src/network/ssl/qsslcertificate_p.h b/src/network/ssl/qsslcertificate_p.h
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index cdceb0f..1ce33d3 100644
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--- a/src/network/ssl/qsslcertificate_p.h
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+++ b/src/network/ssl/qsslcertificate_p.h
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@@ -96,6 +96,7 @@ public:
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static QSslCertificate QSslCertificate_from_X509(X509 *x509);
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static QList<QSslCertificate> certificatesFromPem(const QByteArray &pem, int count = -1);
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static QList<QSslCertificate> certificatesFromDer(const QByteArray &der, int count = -1);
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+ static bool isBlacklisted(const QSslCertificate &certificate);
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friend class QSslSocketBackendPrivate;
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diff --git a/src/network/ssl/qsslsocket_openssl.cpp b/src/network/ssl/qsslsocket_openssl.cpp
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index 0866534..2427193 100644
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--- a/src/network/ssl/qsslsocket_openssl.cpp
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+++ b/src/network/ssl/qsslsocket_openssl.cpp
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@@ -1193,6 +1193,13 @@ bool QSslSocketBackendPrivate::startHandshake()
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X509 *x509 = q_SSL_get_peer_certificate(ssl);
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configuration.peerCertificate = QSslCertificatePrivate::QSslCertificate_from_X509(x509);
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q_X509_free(x509);
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+ if (QSslCertificatePrivate::isBlacklisted(configuration.peerCertificate)) {
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+ q->setErrorString(QSslSocket::tr("The peer certificate is blacklisted"));
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+ q->setSocketError(QAbstractSocket::SslHandshakeFailedError);
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+ emit q->error(QAbstractSocket::SslHandshakeFailedError);
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+ plainSocket->disconnectFromHost();
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+ return false;
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+ }
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// Start translating errors.
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QList<QSslError> errors;
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