remove all strings when remove imports

macho-go/internal/wrapper/action/remove_imports.go

@@ -8,6 +8,8 @@ type removeImports struct{}
 
 func (action *removeImports) withMacho(mf *MachoFile) error {
 	mf.Context().RemoveBindSymbols()
+	mf.Context().RemoveSymbolTable()
+	mf.Context().RemoveExportTrie()
 	return nil
 }
 

macho-go/pkg/ios/macho/edit.go

@@ -320,6 +320,32 @@ func (mc *MachoContext) RemoveBindSymbols() {
 }
 
 func (mc *MachoContext) removeBindSymbolsModern() {
+  // we don't mess up the chain
+  // we clear the imports table, and the raw opcodes
+  // clearing imports table disables static analysis
+  // clearing opcodes forces runtime manual mapping
+
+  // imports item are defined by mc.fixups.imports_format
+  // basic case is dyld_chained_import, 4 bytes
+
+  start := mc.fixups.dataoff
+  size := mc.fixups.datasize
+  fixups :=  new(Fixups)
+  fixups.Deserialize(mc, mc.buf[start:start+size])
+
+  start = mc.fixups.dataoff + fixups.imports_offset
+  size = fixups.imports_count * 4
+  fmt.Printf("// Erase at=0x%x size=0x%x\n", start, size)
+  mc.file.WriteAt(make([]byte, size), int64(start))
+
+  // string reference are at the end of this section
+  start = mc.fixups.dataoff + fixups.symbols_offset
+  size = mc.fixups.Datasize() - fixups.symbols_offset
+  fmt.Printf("// Erase at=0x%x size=0x%x\n", start, size)
+  mc.file.WriteAt(make([]byte, size), int64(start))
+
+  fixups.imports_count = 0
+  mc.file.WriteAt(fixups.Serialize(mc), int64(mc.fixups.dataoff))
 }
 
 func (mc *MachoContext) removeBindSymbolsLegacy() {
@@ -329,3 +355,89 @@ func (mc *MachoContext) removeBindSymbolsLegacy() {
   // but no symbol state to bind
   mc.file.WriteAt(make([]byte, size), int64(start))
 }
+
+func (mc *MachoContext) RemoveSymbolTable() {
+  // try to remove symtab and dysymtab
+  mc.removeSymtabCommand()
+  mc.removeDySymtabCommand()
+}
+
+func (mc *MachoContext) removeSymtabCommand() {
+  ptr := int64(0)
+	if mc.Is64bit() {
+		ptr, _ = mc.file.Seek(int64(Header_size_64), io.SeekStart)
+	} else {
+		ptr, _ = mc.file.Seek(int64(Header_size), io.SeekStart)
+	}
+
+  var symtab_fix *Symtab
+	for _, cmd := range mc.commands {
+		if cmd.Cmd() != LC_SYMTAB {
+      ptr += int64(cmd.Cmdsize())
+			continue
+		}
+    var symtab = cmd.(*Symtab)
+    symtab_fix = symtab
+
+    // erase strings referenced
+    start := int64(symtab_fix.stroff)
+    size := symtab_fix.strsize
+    fmt.Printf("// Erase at=0x%x size=0x%x\n", start, size)
+    mc.file.WriteAt(make([]byte, size), start)
+
+    // erase nlist64 symbol items
+    start = int64(symtab_fix.symoff)
+    size = symtab_fix.nsyms * 16
+    fmt.Printf("// Erase at=0x%x size=0x%x\n", start, size)
+    mc.file.WriteAt(make([]byte, size), start)
+
+    symtab_fix.symoff = 0
+    symtab_fix.nsyms = 0
+    symtab_fix.stroff = 0
+    symtab_fix.strsize = 0
+		mc.file.Seek(ptr, io.SeekStart)
+		mc.file.Write(symtab_fix.Serialize(mc))
+    break
+	}
+  mc.file.Seek(0, io.SeekStart)
+}
+
+func (mc *MachoContext) removeDySymtabCommand() {
+  ptr := int64(0)
+	if mc.Is64bit() {
+		ptr, _ = mc.file.Seek(int64(Header_size_64), io.SeekStart)
+	} else {
+		ptr, _ = mc.file.Seek(int64(Header_size), io.SeekStart)
+	}
+	for _, cmd := range mc.commands {
+		if cmd.Cmd() != LC_DYSYMTAB {
+      ptr += int64(cmd.Cmdsize())
+			continue
+		}
+    var dysymtab = cmd.(*DySymtab)
+    dysymtab_fix := dysymtab
+    dysymtab_fix.indirectsymoff = 0
+    dysymtab_fix.nindirectsyms = 0
+		mc.file.Seek(ptr, io.SeekStart)
+		mc.file.Write(dysymtab_fix.Serialize(mc))
+	}
+}
+
+func (mc *MachoContext) RemoveExportTrie() {
+  var start int64
+  var size int
+  if mc.dyldinfo != nil {
+    // legacy export trie
+    start = int64(mc.dyldinfo.export_off)
+    size = int(mc.dyldinfo.export_size)
+    mc.file.WriteAt(make([]byte, size), start)
+  } else if mc.exports != nil {
+    // modern export trie
+    start = int64(mc.exports.dataoff)
+    size = int(mc.exports.datasize)
+    mc.file.WriteAt(make([]byte, size), start)
+  } else {
+    // no export trie (??)
+    // should never occur unless this binary is modified
+  }
+}