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# garble
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GO111MODULE=on go get mvdan.cc/garble
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Obfuscate Go code by wrapping the Go toolchain. Requires Go 1.15 or later, since
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Go 1.14 uses an entirely different object format.
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garble build [build flags] [packages]
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See `garble -h` for up to date usage information.
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### Purpose
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Produce a binary that works as well as a regular build, but that has as little
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information about the original source code as possible.
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The tool is designed to be:
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* Coupled with `cmd/go`, to support both `GOPATH` and modules with ease
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* Deterministic and reproducible, given the same initial source code
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* Reversible given the original source, to un-garble panic stack traces
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### Mechanism
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The tool wraps calls to the Go compiler and linker to transform the Go build, in
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order to:
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* Replace as many useful identifiers as possible with short base64 hashes
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* Replace package paths with short base64 hashes
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* Remove all [build](https://golang.org/pkg/runtime/#Version) and [module](https://golang.org/pkg/runtime/debug/#ReadBuildInfo) information
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* Strip filenames and shuffle position information
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* Strip debugging information and symbol tables
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* Obfuscate literals, if the `-literals` flag is given
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* Removes [extra information](#tiny-mode) if the `-tiny` flag is given
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### Options
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By default, the tool garbles the packages under the current module. If not
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running in module mode, then only the main package is garbled. To specify what
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packages to garble, set `GOPRIVATE`, documented at `go help module-private`.
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### Caveats
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Most of these can improve with time and effort. The purpose of this section is
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to document the current shortcomings of this tool.
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* Build caching is not supported, so large projects will likely be slow to
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build. See [golang/go#41145](https://github.com/golang/go/issues/41145).
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* Exported methods and fields are never garbled at the moment, since they could
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be required by interfaces and reflection. This area is a work in progress.
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* Functions implemented outside Go, such as assembly, aren't garbled since we
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currently only transform the input Go source.
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* Go plugins are not currently supported; see [#87](https://github.com/burrowers/garble/issues/87).
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### Tiny Mode
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When the `-tiny` flag is passed, extra information is stripped from the resulting
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Go binary. This includes line numbers, filenames, and code in the runtime the
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prints panics, fatal errors, and trace/debug info. All in all this can make binaries
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6-10% smaller in our testing.
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Note: if `-tiny` is passed, no panics, fatal errors will ever be printed, but they can
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still be handled internally with `recover` as normal. In addition, the `GODEBUG`
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environmental variable will be ignored.
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