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|
package builder
import (
"bytes"
"debug/elf"
"debug/macho"
"encoding/binary"
"fmt"
"io"
"os"
"runtime"
)
// ReadBuildID reads the build ID from the currently running executable.
func ReadBuildID() ([]byte, error) {
executable, err := os.Executable()
if err != nil {
return nil, err
}
f, err := os.Open(executable)
if err != nil {
return nil, err
}
defer f.Close()
switch runtime.GOOS {
case "linux", "freebsd":
// Read the GNU build id section. (Not sure about FreeBSD though...)
file, err := elf.NewFile(f)
if err != nil {
return nil, err
}
for _, section := range file.Sections {
if section.Type != elf.SHT_NOTE || section.Name != ".note.gnu.build-id" {
continue
}
buf := make([]byte, section.Size)
n, err := section.ReadAt(buf, 0)
if uint64(n) != section.Size || err != nil {
return nil, fmt.Errorf("could not read build id: %w", err)
}
return buf, nil
}
case "darwin":
// Read the LC_UUID load command, which contains the equivalent of a
// build ID.
file, err := macho.NewFile(f)
if err != nil {
return nil, err
}
for _, load := range file.Loads {
// Unfortunately, the debug/macho package doesn't support the
// LC_UUID command directly. So we have to read it from
// macho.LoadBytes.
load, ok := load.(macho.LoadBytes)
if !ok {
continue
}
raw := load.Raw()
command := binary.LittleEndian.Uint32(raw)
if command != 0x1b {
// Looking for the LC_UUID load command.
// LC_UUID is defined here as 0x1b:
// https://opensource.apple.com/source/xnu/xnu-4570.71.2/EXTERNAL_HEADERS/mach-o/loader.h.auto.html
continue
}
return raw[4:], nil
}
default:
// On other platforms (such as Windows) there isn't such a convenient
// build ID. Luckily, Go does have an equivalent of the build ID, which
// is stored as a special symbol named go.buildid. You can read it
// using `go tool buildid`, but the code below extracts it directly
// from the binary.
// Unfortunately, because of stripping with the -w flag, no symbol
// table might be available. Therefore, we have to scan the binary
// directly. Luckily the build ID is always at the start of the file.
// For details, see:
// https://github.com/golang/go/blob/master/src/cmd/internal/buildid/buildid.go
fileStart := make([]byte, 4096)
_, err := io.ReadFull(f, fileStart)
index := bytes.Index(fileStart, []byte("\xff Go build ID: \""))
if index < 0 || index > len(fileStart)-103 {
return nil, fmt.Errorf("could not find build id in %s", err)
}
buf := fileStart[index : index+103]
if bytes.HasPrefix(buf, []byte("\xff Go build ID: \"")) && bytes.HasSuffix(buf, []byte("\"\n \xff")) {
return buf[len("\xff Go build ID: \"") : len(buf)-1], nil
}
}
return nil, fmt.Errorf("could not find build ID in %s", executable)
}
|
