QUrl::fromLocalFile: accept invalid hostnames

QUrl hostnames must be compliant with STD3, but we must somehow accept
file paths that begin with double slash but aren't valid hostnames.
Because the file URI spec requires us to start with "file://" anyway, we
can represent those with four slashes. Note that on Unix "//X/y" is a
valid but local file path. If given to QUrl::fromLocalFile(), if the
path at the root does parse as a hostname, we will still try to
normalize (the above becomes "file://x/y").

[ChangeLog][QtCore][QUrl] Changed QUrl::fromLocalFile() to accept
Windows UNC paths whose hostname component is not a valid Internet
hostname. This makes QUrl able to accept extended-length paths (\\?\),
device namespace (\\.\),  WSL (\\wsl$), etc.

Fixes: QTBUG-86277
Change-Id: I3eb349b832c14610895efffd1635759348214a3b
Reviewed-by: David Faure <david.faure@kdab.com>
(cherry picked from commit 97de53ee8cce3dc6347b08668f0de45e1000f01c)

2 files changed, 26 insertions, 3 deletions

diff --git a/src/corelib/io/qurl.cpp b/src/corelib/io/qurl.cpp
index 0c81af52d7..f7269798a3 100644
--- a/src/corelib/io/qurl.cpp
+++ b/src/corelib/io/qurl.cpp
@@ -3862,12 +3862,20 @@ QUrl QUrl::fromLocalFile(const QString &localFile)
             hostSpec.truncate(hostSpec.size() - 4);
             scheme = webDavScheme();
         }
-        url.setHost(hostSpec.toString());
 
-        if (indexOfPath > 2)
+        // hosts can't be IPv6 addresses without [], so we can use QUrlPrivate::setHost
+        url.detach();
+        if (!url.d->setHost(hostSpec.toString(), 0, hostSpec.size(), StrictMode)) {
+            if (url.d->error->code != QUrlPrivate::InvalidRegNameError)
+                return url;
+
+            // Path hostname is not a valid URL host, so set it entirely in the path
+            // (by leaving deslashified unchanged)
+        } else if (indexOfPath > 2) {
             deslashified = deslashified.right(deslashified.length() - indexOfPath);
-        else
+        } else {
             deslashified.clear();
+        }
     }
 
     url.setScheme(scheme);
diff --git a/tests/auto/corelib/io/qurl/tst_qurl.cpp b/tests/auto/corelib/io/qurl/tst_qurl.cpp
index d506ae5a66..d30ec1d57d 100644
--- a/tests/auto/corelib/io/qurl/tst_qurl.cpp
+++ b/tests/auto/corelib/io/qurl/tst_qurl.cpp
@@ -1280,6 +1280,9 @@ void tst_QUrl::toLocalFile_data()
     QTest::newRow("windows-unc-path") << QString::fromLatin1("file://somehost/somedir/somefile") << QString::fromLatin1("//somehost/somedir/somefile");
     QTest::newRow("windows-unc-root") << QString::fromLatin1("file://somehost/") << QString::fromLatin1("//somehost/");
     QTest::newRow("windows-unc-nopath") << QString::fromLatin1("file://somehost") << QString::fromLatin1("//somehost");
+    QTest::newRow("windows-extlen-path") << QString::fromLatin1("file:////%3F/somedir/somefile") << QString::fromLatin1("//?/somedir/somefile");
+    QTest::newRow("windows-wsl-path") << QString::fromLatin1("file:////wsl$/somedir/somefile") << QString::fromLatin1("//wsl$/somedir/somefile");
+    QTest::newRow("windows-device-path") << QString::fromLatin1("file:////./somedir/somefile") << QString::fromLatin1("//./somedir/somefile");
 
     // and some that result in empty (i.e., not local)
     QTest::newRow("noscheme-absolute") << QString::fromLatin1("/a.txt") << QString();
@@ -1332,6 +1335,18 @@ void tst_QUrl::fromLocalFile_data()
                 << QString("file://somehost") + suffix
                 << QString(suffix);
 #endif
+        QTest::addRow("windows-extlen-%s", pathDescription)
+                << QString("//?") + suffix
+                << QString("file:////%3F") + suffix
+                << QString("//?") + suffix;
+        QTest::addRow("windows-wsl-%s", pathDescription)
+                << QString("//wsl$") + suffix
+                << QString("file:////wsl$") + suffix
+                << QString("//wsl$") + suffix;
+        QTest::addRow("windows-device--%s", pathDescription)
+                << QString("//.") + suffix
+                << QString("file:////.") + suffix
+                << QString("//.") + suffix;
     }
 
     QTest::newRow("windows-webdav")