Re-allow running Dolphin as the root user (but still not using sudo)

Summary:
Prohibiting the use of Dolphin as the actual root user (not using `sudo` or `kdesu`) breaks legitimate use cases for using the root user. An example is Kali, a distro that logs in as the root user by default as a deliberate design choice.

In such an environment, there is no additional security vulnerability beyond what you're already potentially exposing yourself to. So, let's re-enable it.

BUG: 387974
FIXED-IN: 18.08.0

Test Plan:
- Log in as normal user and run `sudo dolphin`: you get an error message.
- Log in as normal user and run `kdesu dolphin`: you get an error message.
- Log in as the root user and run dolphin normally: it works.

Reviewers: markg, elvisangelaccio, #dolphin

Reviewed By: markg

Subscribers: chinmoyr, cfeck, elvisangelaccio, mmustac, Fuchs, markg, graesslin, nicolasfella, zzag, kfm-devel, emmanuelp

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D12795

1 files changed, 8 insertions, 3 deletions

diff --git a/src/main.cpp b/src/main.cpp
index db52e11be..75bab677d 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -43,10 +43,15 @@
 extern "C" Q_DECL_EXPORT int kdemain(int argc, char **argv)
 {
 #ifndef Q_OS_WIN
-    // Check whether we are running as root
+    // Prohibit using sudo or kdesu (but allow using the root user directly)
     if (getuid() == 0) {
-        std::cout << "Executing Dolphin as root is not possible." << std::endl;
-        return EXIT_FAILURE;
+        if (!qEnvironmentVariableIsEmpty("SUDO_USER")) {
+            std::cout << "Executing Dolphin with sudo is not possible due to unfixable security vulnerabilities." << std::endl;
+            return EXIT_FAILURE;
+        } else if (!qEnvironmentVariableIsEmpty("KDESU_USER")) {
+            std::cout << "Executing Dolphin with kdesu is not possible due to unfixable security vulnerabilities." << std::endl;
+            return EXIT_FAILURE;
+        }
     }
 #endif