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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,68 @@ | ||
| package elfExecStack | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "io" | ||
| "io/ioutil" | ||
| "os" | ||
|
|
||
| "github.com/alecthomas/kingpin" | ||
| "github.com/apex/log" | ||
| "github.com/develar/errors" | ||
| ) | ||
|
|
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| func ConfigureCommand(app *kingpin.Application) { | ||
| command := app.Command("clear-exec-stack", "") | ||
|
|
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| file := command.Flag("input", "").Short('i').Required().String() | ||
|
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| command.Action(func(context *kingpin.ParseContext) error { | ||
| err := ClearExecStack(*file) | ||
| if err != nil { | ||
| return errors.WithStack(err) | ||
| } | ||
|
|
||
| return nil | ||
| }) | ||
| } | ||
|
|
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| func ClearExecStack(fileName string) error { | ||
| file, err := os.OpenFile(fileName, os.O_RDWR, 0) | ||
| if err != nil { | ||
| return errors.WithStack(err) | ||
| } | ||
|
|
||
| defer file.Close() | ||
|
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| data, err := ioutil.ReadAll(io.LimitReader(file, 2048)) | ||
| if err != nil { | ||
| return errors.WithStack(err) | ||
| } | ||
|
|
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| // GNU_STACK 1685382481 | ||
| gnuStack := []byte{0x51, 0xE5, 0x74, 0x64} | ||
| index := bytes.Index(data, gnuStack) | ||
| if index < 0 { | ||
| return errors.Errorf("cannot find GNU_STACK header in a first 2048 bytes") | ||
| } | ||
|
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| flagIndex := index + len(gnuStack) | ||
|
|
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| if index >= len(data) { | ||
| return errors.Errorf("GNU_STACK header flags outside of first 2048 bytes") | ||
| } | ||
|
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| flagValue := data[flagIndex] | ||
| if flagValue == 6 { | ||
| // already cleared | ||
| log.WithField("flags", flagValue).Debug("stack is already cleared") | ||
| return nil | ||
| } | ||
|
|
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| _, err = file.WriteAt([]byte{0x06}, int64(flagIndex)) | ||
| if err != nil { | ||
| return errors.WithStack(err) | ||
| } | ||
|
|
||
| return nil | ||
| } |
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