This article contains tentatively golang’s packaging techniques and UPX repackaging introduction, because both these 2 topics have small content size and I’d better merge them into one article for typesettings.
Golang Compiling cross platforms
Normally these commands could compile golang program:
SET CGO_ENABLED=0
SET GOOS=linux
SET GOARCH=amd64
go build main.go
Linux on x86:
CGO_ENABLED=0
GOOS=linux
GOARCH=amd64
go build
Linux on arm:
CGO_ENABLED=0
GOOS=linux
GOARCH=arm
go build filename.go
Windows:
CGO_ENABLED=0
GOOS=windows
GOARCH=amd64
go build filename.go
MacOS:
CGO_ENABLED=0
GOOS=darwin
GOARCH=amd64
go build filename.go
CGO is a option for unification of C,C++ and golang, it can unify C and golang’s basic data struct. Its default value is 0, and if you want to set it up to 1, refer to https://stackoverflow.com/questions/64531437/why-is-cgo-enabled-1-default.
Normally if the target executive Linux has standard libc, glibc, you donnot enable this option. If enabling CGO, and the file size after packaging would be bigger.
Golang Compiling without symbols
Golang’s compiling tool chain would build the binaries staticly with standard libraries and Third-party libraries. And the binaries contain runtime and GC(Garbage Collection) instructions. Normally it is hard to analyse the binaries for reverse engineering.
go build command:
go build -ldflags "-s -w"
go build -ldflags "-s -w" -trimpath
go build -ldflags "-w -s" -o SecretDetection-lackOfOptimize.exe
go build -ldflags "-s -w" -trimpath -o SecretDetection-lackOfOptimize.exe
UPX compresses the binaries
I recommand to read the raw github and download the upstream binaries: https://github.com/upx/upx/releases . In china, there are many modified UPX prevalent in many security platforms with backdoors, so that be vigilant except the original github project.
UPX is simple to use, and I dont have deeper research.
# Often command
upx -9 fscan.exe
# The 2 commands below are possible to package with failure, and I suggest to do more tests after compression
upx --best program.exe
upx --brute program.exe
Welcome to point out the mistakes and faults!