Use original test for Windows, use UID for unix and add co-author

patches/server/0806-Add-root-admin-user-detection.patch

@@ -8,46 +8,71 @@ The warning serves as a sort-of PSA for newer server admins who don't understand
 We've seen plenty of bad/malicious plugins hit markets, and there's been a few close-calls with exploits in the past.
 Hopefully this helps mitigate some potential damage to servers, even if it is just a warning.
 
+Co-authored-by: Noah van der Aa <[email protected]>
+
 diff --git a/src/main/java/io/papermc/paper/util/ServerEnvironment.java b/src/main/java/io/papermc/paper/util/ServerEnvironment.java
 new file mode 100644
-index 0000000000000000000000000000000000000000..0f41ea267c2cde6dc897e2c6e1615e1bb42d3a60
+index 0000000000000000000000000000000000000000..2d029bafafd912a35c7d272e9a08b87c23314f88
 --- /dev/null
 +++ b/src/main/java/io/papermc/paper/util/ServerEnvironment.java
-@@ -0,0 +1,41 @@
+@@ -0,0 +1,64 @@
 +package io.papermc.paper.util;
 +
 +import org.apache.commons.lang.SystemUtils;
 +
-+import java.io.File;
++import java.io.BufferedReader;
++import java.io.InputStreamReader;
 +import java.io.IOException;
++import java.io.OutputStream;
++import java.io.PrintStream;
++import java.util.prefs.Preferences;
 +
 +public class ServerEnvironment {
 +    private static final boolean runningAsRootOrAdmin;
 +
 +    static {
 +        if (SystemUtils.IS_OS_WINDOWS) {
-+            String programFiles = System.getenv("ProgramFiles");
-+            if (programFiles == null) {
-+                programFiles = "C:\\Program Files";
-+            }
-+            File programFile = new File(programFiles);
-+            boolean canWrite = programFile.canWrite();
-+
-+            if (canWrite) {
-+                // Make sure that the path can actually be written to.
-+                try {
-+                    File test = File.createTempFile(".paperwritecheck", null, programFile);
-+                    if (!test.delete()) {
-+                        test.deleteOnExit();
-+                    }
-+                } catch (IOException exception) {
-+                    canWrite = false;
++            // https://stackoverflow.com/a/23538961
++            Preferences prefs = Preferences.systemRoot();
++            PrintStream err = System.err;
++            PrintStream emptyStream = new PrintStream(new OutputStream() {
++                @Override
++                public void write(int b) {
 +                }
++            });
++
++            System.err.flush();
++            System.setErr(emptyStream);
++
++            boolean retVal;
++            try {
++                prefs.put("papermc.priv_test", "This is a test performed by the Paper Minecraft server software."); // SecurityException
++                prefs.remove("papermc.priv_test");
++                prefs.flush(); // BackingStoreException
++                retVal = true;
++            } catch (Exception ignored) { // Windows = SecurityException
++                retVal = false;
 +            }
++            runningAsRootOrAdmin = retVal;
 +
-+            runningAsRootOrAdmin = canWrite;
++            System.err.flush();
++            System.setErr(err);
 +        } else {
-+            runningAsRootOrAdmin = System.getProperty("user.name", "").equals("root");
++            String uid = "";
++
++            // https://stackoverflow.com/a/4796235/11171331
++            try {
++                Process child = Runtime.getRuntime().exec("id -u " + System.getProperty("user.name"));
++
++                // Get the input stream and read from it.
++                BufferedReader reader = new BufferedReader(new InputStreamReader(child.getInputStream()));
++                uid = reader.readLine();
++                reader.close();
++            } catch (IOException ignored) {
++            }
++
++            // On Unix systems the UID for the root user is always zero.
++            runningAsRootOrAdmin = uid.equals("0");
 +        }
 +    }
 +