add support for experimental safe-mode which disables some functionality

src/Evaller.php

@@ -6,14 +6,16 @@ class Evaller
     protected Tokenizer $tokenizer;
     protected Reader $reader;
     protected Printer $printer;
+    protected bool $safemode;
 
     protected bool $debug = false;
 
-    public function __construct(Tokenizer $tokenizer, Reader $reader, Printer $printer)
+    public function __construct(Tokenizer $tokenizer, Reader $reader, Printer $printer, bool $safemode)
     {
         $this->tokenizer = $tokenizer;
         $this->reader = $reader;
         $this->printer = $printer;
+        $this->safemode = $safemode;
     }
 
     public function eval($ast, Env $env)
@@ -116,7 +118,7 @@ class Evaller
 
                     $ast = $astData[$astLength - 1];
                     continue; // tco
-                } elseif ($symbolName == 'env') {
+                } elseif (!$this->safemode && $symbolName == 'env') {
                     if ($astLength >= 2) {
                         if (!($astData[1] instanceof Symbol)) {
                             throw new MadLispException("first argument to env is not symbol");
@@ -126,7 +128,7 @@ class Evaller
                     } else {
                         return $env;
                     }
-                } elseif ($symbolName == 'eval') {
+                } elseif (!$this->safemode && $symbolName == 'eval') {
                     if ($astLength == 1) {
                         return null;
                     }
@@ -207,10 +209,13 @@ class Evaller
                     $ast = $astData[2];
                     $env = $newEnv;
                     continue; // tco
-                } elseif ($symbolName == 'load') {
+                } elseif (!$this->safemode && $symbolName == 'load') {
                     // Load is here because we want to load into
                     // current $env which is hard otherwise.
 
+                    // This is disabled now for safe-mode, but some
+                    // use (maybe restricted) might need to be allowed.
+
                     if ($astLength != 2) {
                         throw new MadLispException("load requires exactly 1 argument");
                     }

src/Lib/Core.php

@@ -20,21 +20,26 @@ class Core implements ILib
     protected Reader $reader;
     protected Printer $printer;
     protected Evaller $evaller;
+    protected bool $safemode;
 
-    public function __construct(Tokenizer $tokenizer, Reader $reader, Printer $printer, Evaller $evaller)
+    public function __construct(Tokenizer $tokenizer, Reader $reader, Printer $printer, Evaller $evaller, bool $safemode)
     {
         $this->tokenizer = $tokenizer;
         $this->reader = $reader;
         $this->printer = $printer;
         $this->evaller = $evaller;
+        $this->safemode = $safemode;
     }
 
     public function register(Env $env): void
     {
         // Register special constants
+        if (!$this->safemode) {
             $env->set('__FILE__', null);
             $env->set('__DIR__', null);
+        }
 
+        if (!$this->safemode) {
             $env->set('debug', new CoreFunc('debug', 'Toggle debug mode.', 0, 0,
                 function () {
                     $val = !$this->evaller->getDebug();
@@ -42,8 +47,9 @@ class Core implements ILib
                     return $val;
                 }
             ));
+        }
 
-        $env->set('doc', new CoreFunc('doc', 'Get or set documentation for a function.', 1, 2,
+        $env->set('doc', new CoreFunc('doc', 'Get or set documentation string for a function.', 1, 2,
             function (Func $a, ?string $str = null) {
                 if (func_num_args() == 1) {
                     return $a->getDoc();
@@ -63,6 +69,7 @@ class Core implements ILib
             }
         ));
 
+        if (!$this->safemode) {
             $env->set('meta', new CoreFunc('meta', 'Read meta information of an entity.', 2, 2,
                 function ($obj, $attribute) {
                     if ($obj instanceof Env) {
@@ -88,28 +95,37 @@ class Core implements ILib
                     }
                 }
             ));
+        }
 
+        if (!$this->safemode) {
             $env->set('read', new CoreFunc('read', 'Read string as code.', 1, 1,
                 fn (string $a) => $this->reader->read($this->tokenizer->tokenize($a))
             ));
+        }
 
+        if (!$this->safemode) {
             $env->set('print', new CoreFunc('print', 'Print argument. Give second argument as true to show strings in readable format.', 1, 2,
                 function ($a, bool $readable = false) {
                     $this->printer->print($a, $readable);
                     return null;
                 }
             ));
+        }
 
+        // This is allowed in safe-mode, because the evaluation should be wrapped in a try-catch in embedded use.
         $env->set('error', new CoreFunc('error', 'Throw an exception using argument (string) as message.', 1, 1,
             function (string $error) {
+                // We should probably use another exception type to distinguish user-thrown errors from built-in errors.
                 throw new MadLispException($error);
             }
         ));
 
+        if (!$this->safemode) {
             $env->set('exit', new CoreFunc('exit', 'Terminate the script with given exit code.', 0, 1,
                 function (int $status = 0) {
                     exit($status);
                 }
             ));
         }
+    }
 }

src/LispFactory.php

@@ -3,25 +3,22 @@ namespace MadLisp;
 
 class LispFactory
 {
-    public function make(array $coreLibs = [], array $userLibs = []): Lisp
+    public function make(bool $safemode = false): Lisp
     {
         $tokenizer = new Tokenizer();
         $reader = new Reader();
         $printer = new Printer();
-        $eval = new Evaller($tokenizer, $reader, $printer);
+        $eval = new Evaller($tokenizer, $reader, $printer, $safemode);
 
         // Root environment
         $env = new Env('root');
 
         // Register core functions
-        (new Lib\Core($tokenizer, $reader, $printer, $eval))->register($env);
+        (new Lib\Core($tokenizer, $reader, $printer, $eval, $safemode))->register($env);
 
         // Register core libraries
         (new Lib\Collections())->register($env);
         (new Lib\Compare())->register($env);
-        (new Lib\Database())->register($env);
-        (new Lib\Http())->register($env);
-        (new Lib\IO())->register($env);
         (new Lib\Json())->register($env);
         (new Lib\Math())->register($env);
         (new Lib\Regex())->register($env);
@@ -29,19 +26,16 @@ class LispFactory
         (new Lib\Time())->register($env);
         (new Lib\Types())->register($env);
 
-        // Register additional libs for root env
+        // Register unsafe libraries if not in safemode
-        foreach ($coreLibs as $lib) {
+        if (!$safemode) {
-            $lib->register($env);
+            (new Lib\Database())->register($env);
+            (new Lib\Http())->register($env);
+            (new Lib\IO())->register($env);
         }
 
         // User environment
         $env = new Env('user', $env);
 
-        // Register additional libs for user env
-        foreach ($userLibs as $lib) {
-            $lib->register($env);
-        }
-
         return new Lisp($tokenizer, $reader, $eval, $printer, $env);
     }
 }