properly handle controlflow obfuscation in code that uses unsafe

Due to unsafe not being a real dependency, type checking during control-flow obfuscation was performed incorrectly.
This is fixed by excluding unsafe from the dependency checks.


Fixes #903

main.go

@@ -1248,6 +1248,11 @@ func (tf *transformer) processImportCfg(flags []string, requiredPkgs []string) (
 	if requiredPkgs != nil {
 		newIndirectImports = make(map[string]bool)
 		for _, pkg := range requiredPkgs {
+			// unsafe is a special case, it's not a real dependency
+			if pkg == "unsafe" {
+				continue
+			}
+
 			newIndirectImports[pkg] = true
 		}
 	}
@@ -1727,6 +1732,8 @@ func recordType(used, origin types.Type, done map[*types.Named]bool, fieldToStru
 // Unsafe types: generic types and non-method interfaces.
 func isSafeForInstanceType(t types.Type) bool {
 	switch t := types.Unalias(t).(type) {
+	case *types.Basic:
+		return t.Kind() != types.Invalid
 	case *types.Named:
 		if t.TypeParams().Len() > 0 {
 			return false

testdata/script/ctrlflow.txtar

@@ -38,6 +38,7 @@ import (
 	"encoding/binary"
 	"encoding/hex"
 	"hash/crc32"
+	"unsafe"
 )
 
 //garble:controlflow flatten_passes=0 junk_jumps=max block_splits=max
@@ -78,6 +79,22 @@ func multiHardeningTest(i int) int {
     return multiply(i);
 }
 
+//garble:controlflow
+func ModifyValue() {
+	var a int = 42
+	var p *int = &a
+
+	println("Value of a:", a)
+
+	var up unsafe.Pointer = unsafe.Pointer(p)
+
+	var p2 *int = (*int)(up)
+
+	*p2 = 100
+
+	println("New value of a:", a)
+}
+
 //garble:controlflow flatten_passes=1 junk_jumps=10 block_splits=10 trash_blocks=32
 func main() {
 	// Reference to the unexported interface triggers creation of a new interface
@@ -106,6 +123,7 @@ func main() {
 	println(xorHardeningTest(0))
 	println(delegateHardeningTest(0))
 	println(multiHardeningTest(0))
+	ModifyValue()
 }
 
 -- main.stderr --
@@ -116,4 +134,6 @@ correct name
 884863d2
 1
 1
-1
+1
+Value of a: 42
+New value of a: 100