fixed some sysinfo bugs, and added environment variable privacy

Author: FalsePattern

src/main/java/com/falsepattern/jfunge/Main.java

@@ -43,6 +43,7 @@ public static void main(String[] args) throws IOException, ParseException {
         options.addOptionGroup(masterGroup);
         options.addOption(null, "trefunge", false, "Enable 3D (Trefunge) mode. By default, the interpreter emulates 2D Befunge for compatibility.");
         options.addOption("t", "concurrent", false, "Enables the Concurrent Funge extension (t instruction). Buggy programs can potentially forkbomb the interpreter.");
+        options.addOption(null, "env", false, "Allows the interpreter to access the environment variables of the host system.");
         options.addOption(null, "syscall", false, "Enables the syscall feature (= instruction). This is a very dangerous permission to grant, it can call any arbitrary program on your system.");
         options.addOption(Option.builder("i")
                                 .longOpt("readperm")
@@ -105,6 +106,7 @@ public static void main(String[] args) throws IOException, ParseException {
         val featureSet = FeatureSet.builder();
         featureSet.trefunge(cmd.hasOption("trefunge"));
         featureSet.concurrent(cmd.hasOption("t"));
+        featureSet.environment(cmd.hasOption("env"));
         featureSet.allowedInputFiles(cmd.getOptionValues("i"));
         featureSet.allowedOutputFiles(cmd.getOptionValues("o"));
         featureSet.perl(cmd.hasOption("perl"));

src/main/java/com/falsepattern/jfunge/interpreter/FeatureSet.java

@@ -11,6 +11,7 @@ public class FeatureSet {
     public final String[] allowedInputFiles;
     public final String[] allowedOutputFiles;
     public final boolean concurrent;
+    public final boolean environment;
     public final long maxIter;
 
     public final boolean perl;

src/main/java/com/falsepattern/jfunge/interpreter/Interpreter.java

@@ -25,7 +25,6 @@
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -75,6 +74,9 @@ public boolean writeFile(String file, byte[] data) throws IOException {
     private final boolean unrestrictedOutput;
     private final Path[] allowedOutputPaths;
 
+    @Getter
+    private final Map<String, String> env;
+
     private final TIntObjectMap<Map<String, Object>> globals = new TIntObjectHashMap<>();
 
     private Integer exitCode = null;
@@ -132,6 +134,13 @@ public Interpreter(String[] args, InputStream input, OutputStream output, FileIO
         }
         envFlags = env;
 
+        if (featureSet.environment) {
+            this.env = new HashMap<>(System.getenv());
+        } else {
+            this.env = new HashMap<>();
+        }
+        this.env.put("JFUNGE_ENV", featureSet.environment ? "PASS" : "BLOCK");
+
         if (!featureSet.perl) {
             fingerprintBlackList.add(PERL.INSTANCE.code());
         }
@@ -298,11 +307,6 @@ public void step(IP ip) {
         } while (p == ' ');
     }
 
-    @Override
-    public Map<String, String> env() {
-        return Collections.unmodifiableMap(System.getenv());
-    }
-
     @Override
     public int input(boolean stagger) {
         var value = -1;

src/main/java/com/falsepattern/jfunge/interpreter/instructions/Funge98.java

@@ -470,17 +470,18 @@ public static void sysInfo(ExecutionContext ctx) {
         val n = s.pop();
         val sizes = ctx.IP().stackStack().stackSizes();
         //20 envs
+        s.push(0);
         for (Map.Entry<String, String> entry : ctx.env().entrySet()) {
             String key = entry.getKey();
             String value = entry.getValue();
             s.pushString(key + "=" + value);
         }
         //19 args
+        s.push(0);
+        s.push(0);
         for (String s1 : ctx.args()) {
             s.pushString(s1);
         }
-        s.push(0);
-        s.push(0);
         //18 sizes of stack stack
         for (int size : sizes) {
             s.push(size);