Remediate errors in various favicon fetch scenarios (#2779)

Fixes stuck "Download favicon" button on icon download attempts for IP
address hosts by skipping attempts to get 2nd level domain resources
(which resulted in calls to 0.0.0.<rightmost octet of original IP>).

Fixes some cases when DuckDuckGo fallback fails to find icon of >2-level
domains, by adding a request to a DDG URL based on entry's 2nd level
domain.

Repurposes EditWidgetIcons' private fetchCanceled slot (which as of #2439,
is unused by any code) into public abortRequests slot, which is
connected to the entry edit widget's accepted and rejected signals (in
other words, Ok or Cancel was pressed).

src/gui/EditWidgetIcons.cpp

@@ -30,6 +30,7 @@
 #include "gui/MessageBox.h"
 
 #ifdef WITH_XC_NETWORKING
+#include <QHostInfo>
 #include <QNetworkAccessManager>
 #include <QtNetwork>
 #endif
@@ -195,13 +196,27 @@ void EditWidgetIcons::downloadFavicon()
     m_urlsToTry.clear();
 
     QString fullyQualifiedDomain = m_url.host();
-    QString secondLevelDomain = getSecondLevelDomain(m_url);
 
-    // Attempt to simply load the favicon.ico file
+    m_urlsToTry.append(QUrl(m_url.scheme() + "://" + fullyQualifiedDomain + "/favicon.ico"));
-    if (fullyQualifiedDomain != secondLevelDomain) {
+
-        m_urlsToTry.append(QUrl(m_url.scheme() + "://" + fullyQualifiedDomain + "/favicon.ico"));
+    // Determine if host portion of URL is an IP address by resolving it and
+    // searching for a match with the returned address(es).
+    bool hostIsIp = false;
+    QList<QHostAddress> hostAddressess = QHostInfo::fromName(fullyQualifiedDomain).addresses();
+    for (auto addr : hostAddressess) {
+        if (addr.toString() == fullyQualifiedDomain) {
+            hostIsIp = true;
+        }
+    }
+
+    if (!hostIsIp) {
+        QString secondLevelDomain = getSecondLevelDomain(m_url);
+
+        // Attempt to simply load the favicon.ico file
+        if (fullyQualifiedDomain != secondLevelDomain) {
+            m_urlsToTry.append(QUrl(m_url.scheme() + "://" + secondLevelDomain + "/favicon.ico"));
+        }
     }
-    m_urlsToTry.append(QUrl(m_url.scheme() + "://" + secondLevelDomain + "/favicon.ico"));
 
     // Try to use alternative fallback URL, if enabled
     if (config()->get("security/IconDownloadFallback", false).toBool()) {
@@ -209,6 +224,15 @@ void EditWidgetIcons::downloadFavicon()
         fallbackUrl.setPath("/ip3/" + QUrl::toPercentEncoding(fullyQualifiedDomain) + ".ico");
 
         m_urlsToTry.append(fallbackUrl);
+
+        if (!hostIsIp) {
+            QString secondLevelDomain = getSecondLevelDomain(m_url);
+
+            if (fullyQualifiedDomain != secondLevelDomain) {
+                fallbackUrl.setPath("/ip3/" + QUrl::toPercentEncoding(secondLevelDomain) + ".ico");
+                m_urlsToTry.append(fallbackUrl);
+            }
+        }
     }
 
     startFetchFavicon(m_urlsToTry.takeFirst());
@@ -276,7 +300,7 @@ void EditWidgetIcons::fetchFinished()
 #endif
 }
 
-void EditWidgetIcons::fetchCanceled()
+void EditWidgetIcons::abortRequests()
 {
 #ifdef WITH_XC_NETWORKING
     if (m_reply) {

src/gui/EditWidgetIcons.h

@@ -19,7 +19,6 @@
 #ifndef KEEPASSX_EDITWIDGETICONS_H
 #define KEEPASSX_EDITWIDGETICONS_H
 
-#include <QSet>
 #include <QUrl>
 #include <QUuid>
 #include <QWidget>
@@ -66,6 +65,7 @@ public:
 
 public slots:
     void setUrl(const QString& url);
+    void abortRequests();
 
 signals:
     void messageEditEntry(QString, MessageWidget::MessageType);
@@ -77,7 +77,6 @@ private slots:
     void startFetchFavicon(const QUrl& url);
     void fetchFinished();
     void fetchReadyRead();
-    void fetchCanceled();
     void addCustomIconFromFile();
     bool addCustomIcon(const QImage& icon);
     void removeCustomIcon();

src/gui/entry/EditEntryWidget.cpp

@@ -194,6 +194,8 @@ void EditEntryWidget::setupAdvanced()
 void EditEntryWidget::setupIcon()
 {
     addPage(tr("Icon"), FilePath::instance()->icon("apps", "preferences-desktop-icons"), m_iconsWidget);
+    connect(this, SIGNAL(accepted()), m_iconsWidget, SLOT(abortRequests()));
+    connect(this, SIGNAL(rejected()), m_iconsWidget, SLOT(abortRequests()));
 }
 
 void EditEntryWidget::setupAutoType()