SSL internals: do not write after shutting down the socket

... but rather throw an error, so the HTTP layer can recover from a SSL
shutdown gracefully. In case the other side sent us a shutdown, we tried
to send one as well, which results in an error.

(backport of commit e145b67fbd54f147dab0f8e460280a9c8533aa7b)
Change-Id: I57291a5363cb0f6585dbd6aaa521c748766a1fdf
Reviewed-by: Richard J. Moore <rich@kde.org>

3 files changed, 13 insertions, 4 deletions

diff --git a/src/network/ssl/qsslsocket.cpp b/src/network/ssl/qsslsocket.cpp
index 6ec8f6e..454a52a 100644
--- a/src/network/ssl/qsslsocket.cpp
+++ b/src/network/ssl/qsslsocket.cpp
@@ -1851,6 +1851,7 @@ QSslSocketPrivate::QSslSocketPrivate()
     , mode(QSslSocket::UnencryptedMode)
     , autoStartHandshake(false)
     , connectionEncrypted(false)
+    , shutdown(false)
     , ignoreAllSslErrors(false)
     , readyReadEmittedPointer(0)
     , allowRootCertOnDemandLoading(true)
@@ -1875,6 +1876,7 @@ void QSslSocketPrivate::init()
     autoStartHandshake = false;
     connectionEncrypted = false;
     ignoreAllSslErrors = false;
+    shutdown = false;
 
     // we don't want to clear the ignoreErrorsList, so
     // that it is possible setting it before connecting
diff --git a/src/network/ssl/qsslsocket_openssl.cpp b/src/network/ssl/qsslsocket_openssl.cpp
index 37dea2b..4b0a9ec 100644
--- a/src/network/ssl/qsslsocket_openssl.cpp
+++ b/src/network/ssl/qsslsocket_openssl.cpp
@@ -1163,8 +1163,11 @@ void QSslSocketBackendPrivate::transmit()
 #ifdef QSSLSOCKET_DEBUG
                 qDebug() << "QSslSocketBackendPrivate::transmit: remote disconnect";
 #endif
-                plainSocket->disconnectFromHost();
-                break;
+                shutdown = true; // the other side shut down, make sure we do not send shutdown ourselves
+                q->setErrorString(QSslSocket::tr("The TLS/SSL connection has been closed"));
+                q->setSocketError(QAbstractSocket::RemoteHostClosedError);
+                emit q->error(QAbstractSocket::RemoteHostClosedError);
+                return;
             case SSL_ERROR_SYSCALL: // some IO error
             case SSL_ERROR_SSL: // error in the SSL library
                 // we do not know exactly what the error is, nor whether we can recover from it,
@@ -1447,8 +1450,11 @@ bool QSslSocketBackendPrivate::startHandshake()
 void QSslSocketBackendPrivate::disconnectFromHost()
 {
     if (ssl) {
-        q_SSL_shutdown(ssl);
-        transmit();
+        if (!shutdown) {
+            q_SSL_shutdown(ssl);
+            shutdown = true;
+            transmit();
+        }
     }
     plainSocket->disconnectFromHost();
 }
diff --git a/src/network/ssl/qsslsocket_p.h b/src/network/ssl/qsslsocket_p.h
index 5044c72..f8967d0 100644
--- a/src/network/ssl/qsslsocket_p.h
+++ b/src/network/ssl/qsslsocket_p.h
@@ -108,6 +108,7 @@ public:
     QSslSocket::SslMode mode;
     bool autoStartHandshake;
     bool connectionEncrypted;
+    bool shutdown;
     bool ignoreAllSslErrors;
     QList<QSslError> ignoreErrorsList;
     bool* readyReadEmittedPointer;