Gob encoding

[tandem97]

What version of Garble and Go are you using?

mvdan.cc/garble v0.10.0

Build settings:
      -buildmode exe
       -compiler gc
     CGO_ENABLED 1
          GOARCH amd64
            GOOS windows
         GOAMD64 v1

go version go1.20.4 windows/amd64

What environment are you running Garble on?

go env Output

set GO111MODULE=on
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Admin\AppData\Local\go-build
set GOENV=C:\Users\Admin\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\go\pkg\mod
set GONOPROXY=nuke.team/*
set GONOSUMDB=nuke.team/*
set GOOS=windows
set GOPATH=C:\go
set GOPRIVATE=nuke.team/*
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\Program Files\Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.20.4
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=C:\go\src\С2_payloads\go.mod
set GOWORK=
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=C:\Users\Admin\AppData\Local\Temp\go-build1184724407=/tmp/go-build -gno-record-gcc-switches

What did you do?

i have client and server which use gob to encode their messages. I have problems with decoding because encoded data contains struct fields names which garble modify. I made some experiments and found strange thing. Here is main.go code:

package main

import (
    "bytes"
    "encoding/gob"
    "fmt"
    "test/internal"
)

type Message struct {
    ClientId string
    Data     []byte
}

func main() {
    var buf bytes.Buffer
    gob.NewEncoder(&buf).Encode(internal.Message{ClientId: "some client", Data: []byte{1}})
    fmt.Println(buf.String())

    var buf2 bytes.Buffer
    gob.NewEncoder(&buf2).Encode(Message{ClientId: "some client", Data: []byte{1}})
    fmt.Println(buf2.String())
}

here is internal package code:

package internal

type Message struct {
    ClientId string
    Data     []byte
}

garble.exe -seed=random run .\test.go

What did you expect to see?

the same print of two buffers

What did you see instead?

3��♥☺☺  HOJir8bDv☺��☺☻☺ RVCvdUj5N☺♀☺    JzYNwJvir☺
‼��☺♂some client☺☺☺
+��♥☺☺Message☺��☺☻ClientId☺♀☺♦Data☺
‼��☺♂some client☺☺☺

What is the right way to use garble with gob encoding? How can i save struct field's name from garble? Thanks for help!

[lu4p]

gob uses reflection to get field names, garble will skip types which are reflected.

However this only works for types which are reflected in the same package, you can add a hint for garble to your internal package

 var _ = reflect.TypeOf(Message{})