@ -584,6 +584,8 @@ var transformFuncs = map[string]func([]string) ([]string, error){
"link" : transformLink ,
}
var rxIncludeHeader = regexp . MustCompile ( ` #include\s+"([^"]+)" ` )
func transformAsm ( args [ ] string ) ( [ ] string , error ) {
if ! curPkg . ToObfuscate {
return args , nil // we're not obfuscating this package
@ -612,15 +614,8 @@ func transformAsm(args []string) ([]string, error) {
return append ( flags , newPaths ... ) , nil
}
// We need to replace all function references with their obfuscated name
// counterparts.
// Luckily, all func names in Go assembly files are immediately followed
// by the unicode "middle dot", like:
//
// TEXT ·privateAdd(SB),$0-24
const middleDot = '·'
middleDotLen := utf8 . RuneLen ( middleDot )
const missingHeader = "missing header path"
newHeaderPaths := make ( map [ string ] string )
var buf bytes . Buffer
for _ , path := range paths {
// Read the entire file into memory.
@ -629,67 +624,57 @@ func transformAsm(args []string) ([]string, error) {
if err != nil {
return nil , err
}
buf . Reset ( )
// Find all middle-dot names, and replace them.
remaining := content
for {
i := bytes . IndexRune ( remaining , middleDot )
if i < 0 {
buf . Write ( remaining )
remaining = nil
break
offset := 0
for _ , match := range rxIncludeHeader . FindAllSubmatchIndex ( content , - 1 ) {
start , end := offset + match [ 2 ] , offset + match [ 3 ]
path := string ( content [ start : end ] )
if strings . ContainsAny ( path , "\n\"" ) {
// If we failed to keep track of offsets, we could see a header
// path that contains quotes or newlines, which should not happen.
return nil , fmt . Errorf ( "bad offset tracking? %q" , path )
}
// We want to replace "OP ·foo" and "OP $·foo",
// but not "OP somepkg·foo" just yet.
// "somepkg" is often runtime, syscall, etc.
// We don't obfuscate any of those for now.
//
// TODO: we'll likely need to deal with this
// when we start obfuscating the runtime.
// When we do, note that we can't hash with curPkg.
localName := false
if i >= 0 {
switch remaining [ i - 1 ] {
case ' ' , '\t' , '$' :
localName = true
newPath := newHeaderPaths [ path ]
switch newPath {
case missingHeader : // no need to try again
continue
case "" : // first time we see this header
buf . Reset ( )
content , err := os . ReadFile ( path )
if errors . Is ( err , fs . ErrNotExist ) {
newHeaderPaths [ path ] = missingHeader
continue // a header file provided by Go or the system
} else if err != nil {
return nil , err
}
}
replaceAsmNames ( & buf , content )
i += middleDotLen
buf . Write ( remaining [ : i ] )
remaining = remaining [ i : ]
// The name ends at the first rune which cannot be part
// of a Go identifier, such as a comma or space.
nameEnd := 0
for nameEnd < len ( remaining ) {
c , size := utf8 . DecodeRune ( remaining [ nameEnd : ] )
if ! unicode . IsLetter ( c ) && c != '_' && ! unicode . IsDigit ( c ) {
break
}
nameEnd += size
}
name := string ( remaining [ : nameEnd ] )
remaining = remaining [ nameEnd : ]
// For now, we replace `foo.h` or `dir/foo.h` with `garbled_foo.h`.
// The different name ensures we don't use the unobfuscated file.
// This is far from perfect, but does the job for the time being.
// In the future, use a randomized name.
newPath = "garbled_" + filepath . Base ( path )
if ! localName {
buf . WriteString ( name )
continue
}
// Uncomment for some quick debugging. Do not delete.
// fmt.Fprintf(os.Stderr, "\n-- %s --\n%s", path, buf.Bytes())
newName := hashWithPackage ( curPkg , name )
if flagDebug { // TODO(mvdan): remove once https://go.dev/issue/53465 if fixed
log . Printf ( "asm name %q hashed with %x to %q" , name , curPkg . GarbleActionID , newName )
if _ , err := writeTemp ( newPath , buf . Bytes ( ) ) ; err != nil {
return nil , err
}
newHeaderPaths [ path ] = newPath
}
buf . WriteString ( newName )
offset += len ( newPath ) - len ( path )
// TODO: copying the bytes in a loop like this is far from optimal.
var newContent [ ] byte
newContent = append ( newContent , content [ : start ] ... )
newContent = append ( newContent , newPath ... )
newContent = append ( newContent , content [ end : ] ... )
content = newContent
}
buf . Reset ( )
replaceAsmNames ( & buf , content )
// Uncomment for some quick debugging. Do not delete.
// if curPkg.ToObfuscate {
// fmt.Fprintf(os.Stderr, "\n-- %s --\n%s", path, buf.Bytes())
// }
// fmt.Fprintf(os.Stderr, "\n-- %s --\n%s", path, buf.Bytes())
name := filepath . Base ( path )
if path , err := writeTemp ( name , buf . Bytes ( ) ) ; err != nil {
@ -702,6 +687,70 @@ func transformAsm(args []string) ([]string, error) {
return append ( flags , newPaths ... ) , nil
}
func replaceAsmNames ( buf * bytes . Buffer , remaining [ ] byte ) {
// We need to replace all function references with their obfuscated name
// counterparts.
// Luckily, all func names in Go assembly files are immediately followed
// by the unicode "middle dot", like:
//
// TEXT ·privateAdd(SB),$0-24
const middleDot = '·'
middleDotLen := utf8 . RuneLen ( middleDot )
for {
i := bytes . IndexRune ( remaining , middleDot )
if i < 0 {
buf . Write ( remaining )
remaining = nil
break
}
// We want to replace "OP ·foo" and "OP $·foo",
// but not "OP somepkg·foo" just yet.
// "somepkg" is often runtime, syscall, etc.
// We don't obfuscate any of those for now.
//
// TODO: we'll likely need to deal with this
// when we start obfuscating the runtime.
// When we do, note that we can't hash with curPkg.
localName := false
if i >= 0 {
switch remaining [ i - 1 ] {
case ' ' , '\t' , '$' , ',' , '(' :
localName = true
}
}
i += middleDotLen
buf . Write ( remaining [ : i ] )
remaining = remaining [ i : ]
// The name ends at the first rune which cannot be part
// of a Go identifier, such as a comma or space.
nameEnd := 0
for nameEnd < len ( remaining ) {
c , size := utf8 . DecodeRune ( remaining [ nameEnd : ] )
if ! unicode . IsLetter ( c ) && c != '_' && ! unicode . IsDigit ( c ) {
break
}
nameEnd += size
}
name := string ( remaining [ : nameEnd ] )
remaining = remaining [ nameEnd : ]
if ! localName {
buf . WriteString ( name )
continue
}
newName := hashWithPackage ( curPkg , name )
if flagDebug { // TODO(mvdan): remove once https://go.dev/issue/53465 if fixed
log . Printf ( "asm name %q hashed with %x to %q" , name , curPkg . GarbleActionID , newName )
}
buf . WriteString ( newName )
}
}
// writeTemp is a mix between os.CreateTemp and os.WriteFile, as it writes a
// named source file in sharedTempDir given an input buffer.
//
Daniel Martí
2 years ago