QStandardPaths/unix: ignore relative paths in all $XDG_* env vars

This is a continuation of commit 5c9d671bfb5b511106.

[ChangeLog][QtCore][QStandardPaths] Improved conformance to the
Freedesktop basedir spec by ignoring any relative paths in XDG_*
environment variables.

Fixes: QTBUG-58043
Change-Id: I7c34143ced97d6d3de6ecbf13bccf9e935462d1e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit d4f72b4de63fe0622908c7657f9724bad359574e)
(cherry picked from commit 80a6048ab1806e695764abebe1d9d682ac346a78)

2 files changed, 47 insertions, 5 deletions

diff --git a/src/corelib/io/qstandardpaths_unix.cpp b/src/corelib/io/qstandardpaths_unix.cpp
index 07325ae9c8..55150f9e93 100644
--- a/src/corelib/io/qstandardpaths_unix.cpp
+++ b/src/corelib/io/qstandardpaths_unix.cpp
@@ -185,6 +185,9 @@ QString QStandardPaths::writableLocation(StandardLocation type)
 
         // http://standards.freedesktop.org/basedir-spec/basedir-spec-0.6.html
         QString xdgCacheHome = QFile::decodeName(qgetenv("XDG_CACHE_HOME"));
+        if (!xdgCacheHome.startsWith(u'/'))
+            xdgCacheHome.clear(); // spec says relative paths should be ignored
+
         if (xdgCacheHome.isEmpty())
             xdgCacheHome = QDir::homePath() + "/.cache"_L1;
         if (type == QStandardPaths::CacheLocation)
@@ -199,6 +202,9 @@ QString QStandardPaths::writableLocation(StandardLocation type)
             return QDir::homePath() + "/.qttest/share"_L1;
 
         QString xdgDataHome = QFile::decodeName(qgetenv("XDG_DATA_HOME"));
+        if (!xdgDataHome.startsWith(u'/'))
+            xdgDataHome.clear(); // spec says relative paths should be ignored
+
         if (xdgDataHome.isEmpty())
             xdgDataHome = QDir::homePath() + "/.local/share"_L1;
         if (type == AppDataLocation || type == AppLocalDataLocation)
@@ -214,6 +220,9 @@ QString QStandardPaths::writableLocation(StandardLocation type)
 
         // http://standards.freedesktop.org/basedir-spec/latest/
         QString xdgConfigHome = QFile::decodeName(qgetenv("XDG_CONFIG_HOME"));
+        if (!xdgConfigHome.startsWith(u'/'))
+            xdgConfigHome.clear(); // spec says relative paths should be ignored
+
         if (xdgConfigHome.isEmpty())
             xdgConfigHome = QDir::homePath() + "/.config"_L1;
         if (type == AppConfigLocation)
@@ -223,6 +232,9 @@ QString QStandardPaths::writableLocation(StandardLocation type)
     case RuntimeLocation:
     {
         QString xdgRuntimeDir = QFile::decodeName(qgetenv("XDG_RUNTIME_DIR"));
+        if (!xdgRuntimeDir.startsWith(u'/'))
+            xdgRuntimeDir.clear(); // spec says relative paths should be ignored
+
         bool fromEnv = !xdgRuntimeDir.isEmpty();
         if (xdgRuntimeDir.isEmpty() || !checkXdgRuntimeDir(xdgRuntimeDir)) {
             // environment variable not set or is set to something unsuitable
@@ -249,6 +261,9 @@ QString QStandardPaths::writableLocation(StandardLocation type)
 #if QT_CONFIG(regularexpression)
     // http://www.freedesktop.org/wiki/Software/xdg-user-dirs
     QString xdgConfigHome = QFile::decodeName(qgetenv("XDG_CONFIG_HOME"));
+    if (!xdgConfigHome.startsWith(u'/'))
+        xdgConfigHome.clear(); // spec says relative paths should be ignored
+
     if (xdgConfigHome.isEmpty())
         xdgConfigHome = QDir::homePath() + "/.config"_L1;
     QFile file(xdgConfigHome + "/user-dirs.dirs"_L1);
@@ -361,13 +376,13 @@ static QStringList xdgDataDirs()
 
 static QStringList xdgConfigDirs()
 {
-    QStringList dirs;
     // http://standards.freedesktop.org/basedir-spec/latest/
     const QString xdgConfigDirs = QFile::decodeName(qgetenv("XDG_CONFIG_DIRS"));
-    if (xdgConfigDirs.isEmpty())
-        dirs.append(QString::fromLatin1("/etc/xdg"));
-    else
-        dirs = xdgConfigDirs.split(u':');
+
+    QStringList dirs = dirsList(xdgConfigDirs);
+    if (dirs.isEmpty())
+        dirs.push_back(u"/etc/xdg"_s);
+
     return dirs;
 }
 
diff --git a/tests/auto/corelib/io/qstandardpaths/tst_qstandardpaths.cpp b/tests/auto/corelib/io/qstandardpaths/tst_qstandardpaths.cpp
index 3b06175aa3..d37651bd7a 100644
--- a/tests/auto/corelib/io/qstandardpaths/tst_qstandardpaths.cpp
+++ b/tests/auto/corelib/io/qstandardpaths/tst_qstandardpaths.cpp
@@ -24,6 +24,8 @@
 #define Q_XDG_PLATFORM
 #endif
 
+using namespace Qt::StringLiterals;
+
 // Update this when adding new enum values; update enumNames too
 static const int MaxStandardLocation = QStandardPaths::AppConfigLocation;
 
@@ -724,6 +726,31 @@ void tst_qstandardpaths::testXdgPathCleanup()
     QVERIFY(!appsDirs.contains("/applications"));
     QVERIFY(!appsDirs.contains(uncleanGlobalAppDir + "/applications"));
     QVERIFY(!appsDirs.contains("relative/path/applications"));
+
+    const QString uncleanGlobalConfigDir = "/./" + QFile::encodeName(m_globalConfigDir);
+    qputenv("XDG_CONFIG_DIRS", QFile::encodeName(uncleanGlobalConfigDir) + "::relative/path");
+    const QStringList configDirs = QStandardPaths::standardLocations(QStandardPaths::ConfigLocation);
+    QVERIFY(!configDirs.contains("relative/path"_L1));
+    QVERIFY(!configDirs.contains(""_L1));
+
+    // Relative paths in XDG_* env vars are ignored
+    const QString relative("./someRelativeDir");
+
+    qputenv("XDG_CACHE_HOME", relative.toLatin1());
+    const QString cacheDir = QStandardPaths::writableLocation(QStandardPaths::CacheLocation);
+    QCOMPARE_NE(cacheDir, relative);
+
+    qputenv("XDG_DATA_HOME", relative.toLatin1());
+    const QString localDataDir = QStandardPaths::writableLocation(QStandardPaths::GenericDataLocation);
+    QCOMPARE_NE(localDataDir, relative);
+
+    qputenv("XDG_CONFIG_HOME", relative.toLatin1());
+    const QString localConfig = QStandardPaths::writableLocation(QStandardPaths::ConfigLocation);
+    QCOMPARE_NE(localConfig, relative);
+
+    qputenv("XDG_RUNTIME_DIR", relative.toLatin1());
+    const QString runtimeDir = QStandardPaths::writableLocation(QStandardPaths::GenericDataLocation);
+    QCOMPARE_NE(runtimeDir, relative);
 #endif
 }