How to reverse a stack trace of a executable file that was built with -seed=random?

[nghia-nguyen-ts]

What version of Garble and Go are you using?

$ garble version
mvdan.cc/garble v0.9.3

Build settings:
      -buildmode exe
       -compiler gc
     CGO_ENABLED 1
          GOARCH arm64
            GOOS darwin
$ go version
go version go1.20.1 darwin/arm64

What environment are you running Garble on?

go env Output

$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN=""
GOCACHE="/Users/nghianguyen/Library/Caches/go-build"
GOENV="/Users/nghianguyen/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/nghianguyen/go/pkg/mod"
GONOPROXY="github.com/tsocial/*"
GONOSUMDB="github.com/tsocial/*"
GOOS="darwin"
GOPATH="/Users/nghianguyen/go"
GOPRIVATE="github.com/tsocial/*"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.20.1"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/nghianguyen/Desktop/playground/garble/go.mod"
GOWORK=""
CGO_CFLAGS="-O2 -g"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-O2 -g"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-O2 -g"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/26/qs1y2gzs5xl1sslkyxvbzv_80000gr/T/go-build2983500078=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

1. Build an executable file by: garble build -seed=random main.go, the main.go has some panic inside and prints stack trace.
2. Run main executable file and copy output to stack.txt.
3. garble reverse main.go stack.txt.
4. garble -seed=random reverse main.go stack.txt.

What did you expect to see?

Step 3 and 4 print the un-obfuscated stack trace.

What did you see instead?

Step 3. nor 4. prints the un-obfuscated stack trace.

Question

garble -seed=X reverse main.go stack.txt would prints the un-obfuscated stack trace if X is the value of the random seed used by step 1, right? So can we print the random seed upon garble -seed=random build for later reverse usage?

[lu4p]

Yes you are correct if you want to reverse panics you need to save the random seed.

[nghia-nguyen-ts]

But garble doesn't print the random seed it uses? How do I get the random seed?

[lu4p]

garble/main.go

Line 247 in 059c1d6

fmt.Fprintf(os.Stderr, "random seed: %s\n", base64.RawStdEncoding.EncodeToString(flagSeed.bytes))

You're right the seed is only printed when an error occured, I think it got printed in all cases before. We should definitely fix this.