Merge pull request #41 from d5/sandbox

sandbox environment for scripts

docs/interoperability.md

@@ -4,9 +4,9 @@
 
 - [Using Scripts](#using-scripts)
   - [Type Conversion Table](#type-conversion-table)
-- [Compiler and VM](#compiler-and-vm)
 - [User Types](#user-types)
 - [Sandbox Environments](#sandbox-environments)
+- [Compiler and VM](#compiler-and-vm)
 
 ## Using Scripts
 
@@ -102,15 +102,52 @@ When adding a Variable _([Script.Add](https://godoc.org/github.com/d5/tengo/scri
 
 One can easily add and use customized value types in Tengo code by implementing [Object](https://godoc.org/github.com/d5/tengo/objects#Object) interface. Tengo runtime will treat the user types exactly in the same way it does to the runtime types with no performance overhead. See [Tengo Objects](https://github.com/d5/tengo/blob/master/docs/objects.md) for more details.
 
+## Sandbox Environments
+
+To securely compile and execute _potentially_ unsafe script code, you can use the following Script functions.
+
+#### Script.DisableBuiltinFunction(name string)
+
+DisableBuiltinFunction disables and removes a builtin function from the compiler. Compiler will reports a compile-time error if the given name is referenced.
+
+```golang
+s := script.New([]byte(`print([1, 2, 3])`))
+
+s.DisableBuiltinFunction("print") 
+
+_, err := s.Run() // compile error 
+```
+
+#### Script.DisableStdModule(name string)
+
+DisableStdModule disables a [standard library](https://github.com/d5/tengo/blob/master/docs/stdlib.md) module. Compile will report a compile-time error if the code tries to import the module with the given name.
+
+```golang
+s := script.New([]byte(`import("exec")`))
+
+s.DisableStdModule("exec") 
+
+_, err := s.Run() // compile error 
+```
+
+#### Script.SetUserModuleLoader(loader compiler.ModuleLoader)
+
+SetUserModuleLoader replaces the default user-module loader of the compiler, which tries to read the source from a local file.  
+
+```golang
+s := script.New([]byte(`math := import("mod1"); a := math.foo()`))
+ 
+s.SetUserModuleLoader(func(moduleName string) ([]byte, error) {
+    if moduleName == "mod1" {
+        return []byte(`foo := func() { return 5 }`), nil
+    }
+
+    return nil, errors.New("module not found")
+})
+```
+
 ## Compiler and VM
 
 Although it's not recommended, you can directly create and run the Tengo [Parser](https://godoc.org/github.com/d5/tengo/compiler/parser#Parser), [Compiler](https://godoc.org/github.com/d5/tengo/compiler#Compiler), and [VM](https://godoc.org/github.com/d5/tengo/runtime#VM) for yourself instead of using Scripts and Script Variables. It's a bit more involved as you have to manage the symbol tables and global variables between them, but, basically that's what Script and Script Variable is doing internally.
 
 _TODO: add more information here_
-
-## Sandbox Environments
-
-In an environment where a _(potentially)_ unsafe script code needs to be executed,   
-
-_TODO: add more information here_
-

script/script.go

@@ -7,14 +7,18 @@ import (
 	"github.com/d5/tengo/compiler"
 	"github.com/d5/tengo/compiler/parser"
 	"github.com/d5/tengo/compiler/source"
+	"github.com/d5/tengo/compiler/stdlib"
 	"github.com/d5/tengo/objects"
 	"github.com/d5/tengo/runtime"
 )
 
 // Script can simplify compilation and execution of embedded scripts.
 type Script struct {
-	variables map[string]*Variable
-	input     []byte
+	variables         map[string]*Variable
+	removedBuiltins   map[string]bool
+	removedStdModules map[string]bool
+	userModuleLoader  compiler.ModuleLoader
+	input             []byte
 }
 
 // New creates a Script instance with an input script.
@@ -52,9 +56,32 @@ func (s *Script) Remove(name string) bool {
 	return true
 }
 
+// DisableBuiltinFunction disables a builtin function.
+func (s *Script) DisableBuiltinFunction(name string) {
+	if s.removedBuiltins == nil {
+		s.removedBuiltins = make(map[string]bool)
+	}
+
+	s.removedBuiltins[name] = true
+}
+
+// DisableStdModule disables a standard library module.
+func (s *Script) DisableStdModule(name string) {
+	if s.removedStdModules == nil {
+		s.removedStdModules = make(map[string]bool)
+	}
+
+	s.removedStdModules[name] = true
+}
+
+// SetUserModuleLoader sets the user module loader for the compiler.
+func (s *Script) SetUserModuleLoader(loader compiler.ModuleLoader) {
+	s.userModuleLoader = loader
+}
+
 // Compile compiles the script with all the defined variables, and, returns Compiled object.
 func (s *Script) Compile() (*Compiled, error) {
-	symbolTable, globals := s.prepCompile()
+	symbolTable, stdModules, globals := s.prepCompile()
 
 	fileSet := source.NewFileSet()
 
@@ -64,7 +91,12 @@ func (s *Script) Compile() (*Compiled, error) {
 		return nil, fmt.Errorf("parse error: %s", err.Error())
 	}
 
-	c := compiler.NewCompiler(symbolTable, nil, nil)
+	c := compiler.NewCompiler(symbolTable, stdModules, nil)
+
+	if s.userModuleLoader != nil {
+		c.SetModuleLoader(s.userModuleLoader)
+	}
+
 	if err := c.Compile(file); err != nil {
 		return nil, err
 	}
@@ -100,7 +132,7 @@ func (s *Script) RunContext(ctx context.Context) (compiled *Compiled, err error)
 	return
 }
 
-func (s *Script) prepCompile() (symbolTable *compiler.SymbolTable, globals []*objects.Object) {
+func (s *Script) prepCompile() (symbolTable *compiler.SymbolTable, stdModules map[string]*objects.ImmutableMap, globals []*objects.Object) {
 	var names []string
 	for name := range s.variables {
 		names = append(names, name)
@@ -108,7 +140,16 @@ func (s *Script) prepCompile() (symbolTable *compiler.SymbolTable, globals []*ob
 
 	symbolTable = compiler.NewSymbolTable()
 	for idx, fn := range objects.Builtins {
-		symbolTable.DefineBuiltin(idx, fn.Name)
+		if !s.removedBuiltins[fn.Name] {
+			symbolTable.DefineBuiltin(idx, fn.Name)
+		}
+	}
+
+	stdModules = make(map[string]*objects.ImmutableMap)
+	for name, mod := range stdlib.Modules {
+		if !s.removedStdModules[name] {
+			stdModules[name] = mod
+		}
 	}
 
 	globals = make([]*objects.Object, len(names), len(names))

script/script_test.go

@@ -1,6 +1,7 @@
 package script_test
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/d5/tengo/assert"
@@ -36,3 +37,44 @@ func TestScript_Run(t *testing.T) {
 	assert.NotNil(t, c)
 	compiledGet(t, c, "a", int64(5))
 }
+
+func TestScript_DisableBuiltinFunction(t *testing.T) {
+	s := script.New([]byte(`a := len([1, 2, 3])`))
+	c, err := s.Run()
+	assert.NoError(t, err)
+	assert.NotNil(t, c)
+	compiledGet(t, c, "a", int64(3))
+	s.DisableBuiltinFunction("len")
+	_, err = s.Run()
+	assert.Error(t, err)
+}
+
+func TestScript_DisableStdModule(t *testing.T) {
+	s := script.New([]byte(`math := import("math"); a := math.abs(-19.84)`))
+	c, err := s.Run()
+	assert.NoError(t, err)
+	assert.NotNil(t, c)
+	compiledGet(t, c, "a", 19.84)
+	s.DisableStdModule("math")
+	_, err = s.Run()
+	assert.Error(t, err)
+}
+
+func TestScript_SetUserModuleLoader(t *testing.T) {
+	s := script.New([]byte(`math := import("mod1"); a := math.foo()`))
+	_, err := s.Run()
+	assert.Error(t, err)
+	s.SetUserModuleLoader(func(moduleName string) (res []byte, err error) {
+		if moduleName == "mod1" {
+			res = []byte(`foo := func() { return 5 }`)
+			return
+		}
+
+		err = errors.New("module not found")
+		return
+	})
+	c, err := s.Run()
+	assert.NoError(t, err)
+	assert.NotNil(t, c)
+	compiledGet(t, c, "a", int64(5))
+}