add selfbind functionality

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

@@ -7,9 +7,11 @@ import (
 	"math/rand"
 	"time"
   "strings"
+  "encoding/binary"
 
 	log "github.com/sirupsen/logrus"
 
+	"ios-wrapper/pkg/protomodel"
 	. "ios-wrapper/pkg/ios"
 )
 
@@ -681,3 +683,130 @@ func (mc *MachoContext) RemoveExportTrie() {
 		// should never occur unless this binary is modified
 	}
 }
+
+func (mc *MachoContext) AddSection(segname string, name string, size int) Section {
+  // mc.file.WriteAt(mc.header.Serialize(mc), 0)
+  var ret Section
+  var buffer bytes.Buffer
+	for _, command := range mc.commands {
+		switch command.(type) {
+		case *Segment64:
+      var virtualAddr uint64
+      var fileOffset uint64
+
+			var segment = command.(*Segment64)
+      if bytes.Compare(bytes.Trim(segment.SegName(), "\x00"), []byte(segname)) != 0 {
+        buffer.Write(segment.Serialize(mc))
+        continue
+      } else {
+        virtualAddr = segment.Vmaddr()
+        fileOffset = segment.Fileoff()
+        for _, section := range segment.Sections() {
+          virtualAddr += section.Size()
+          // if section.Offset() != 0 {
+            fileOffset += section.Size()
+          // }
+        }
+
+        align := uint64(4)
+        alignment := align - (fileOffset % align)
+        fileOffset += alignment
+        virtualAddr += alignment
+
+        enoughSpace := segment.Fileoff() + segment.Filesize() >= fileOffset + uint64(size)
+        if !enoughSpace {
+          fmt.Println("Not enough space to store saved info in __DATA segment, need resize (not supported now)")
+          panic("Not enough space to store saved info in __DATA segment, need resize (not supported now)")
+        }
+      }
+
+      var section Section64
+      section.sectname = make([]byte, 16)
+      copy(section.sectname, name)
+      section.segname = make([]byte, 16)
+      copy(section.segname, segname)
+      section.size = uint64(size)
+      section.reloff = 0
+      section.nreloc = 0
+      section.flags = 0
+      section.align = 3
+      section.reserved1 = 0
+      section.reserved2 = 0
+      section.reserved3 = 0
+
+      // addr will increment from the last section
+      // offset will increment from the last section + size
+      // be careful of Virtual section (bss)
+      section.addr = virtualAddr
+      section.offset = uint32(fileOffset)
+      segment.nsects += 1
+      buffer.Write(segment.Serialize(mc))
+      buffer.Write(section.Serialize(mc))
+
+      fmt.Printf("Add a new section with addr=0x%x, fileoffset=0x%x\n", section.addr, section.offset)
+
+      ret = &section
+      continue
+
+    default:
+      buffer.Write(command.Serialize(mc))
+      continue
+    }
+  }
+
+  mc.header.sizeofcmds = uint32(buffer.Len())
+  header := mc.header.Serialize(mc)
+  mc.file.WriteAt(header, 0)
+  mc.file.WriteAt(buffer.Bytes(), int64(len(header)))
+  return ret
+}
+
+func (mc *MachoContext) WriteInfoToData(info *protomodel.MachoInfo) {
+  encode := func () []byte {
+    buffer := new(bytes.Buffer)
+		for _, table := range info.Symbols.Tables {
+      binary.Write(buffer, mc.byteorder, table.LibIndex)
+      binary.Write(buffer, mc.byteorder, table.Nsymbols)
+			for _, symbol := range table.Symbols {
+        binary.Write(buffer, mc.byteorder, (symbol.SymbolIndex<<8)|symbol.SegmentIndex)
+        binary.Write(buffer, mc.byteorder, symbol.Offset)
+			}
+		}
+    instructions := buffer.Bytes()
+
+    buffer = new(bytes.Buffer)
+		for _, lib := range info.Symbols.Libs {
+      buffer.WriteString(lib)
+      buffer.WriteByte(0)
+		}
+    liblist := buffer.Bytes()
+
+    buffer = new(bytes.Buffer)
+		for _, symbol := range info.Symbols.Symbols {
+      buffer.WriteString(symbol)
+      buffer.WriteByte(0)
+		}
+    symbollist := buffer.Bytes()
+
+    buffer = new(bytes.Buffer)
+    // offset to liblist
+    binary.Write(buffer, mc.byteorder, uint32(len(instructions)))
+    // offset to symbollist
+    binary.Write(buffer, mc.byteorder, uint32(len(instructions) + len(liblist)))
+    buffer.Write(instructions)
+    buffer.Write(liblist)
+    buffer.Write(symbollist)
+
+    return buffer.Bytes()
+  }
+  encoded := encode()
+  // encoded := []byte{0x11,0x22,0x33, 0x44}
+  section := mc.AddSection("__DATA", "selfbind", len(encoded))
+  if mc.Is64bit() {
+    var s *Section64 = section.(*Section64)
+    mc.file.WriteAt(encoded, int64(s.Offset()))
+  } else {
+    var s *Section32 = section.(*Section32)
+    mc.file.WriteAt(encoded, int64(s.Offset()))
+  }
+}