go install mvdan.cc/garble@latest
Obfuscate Go code by wrapping the Go toolchain. Requires Go 1.16 or later.
garble build [build flags] [packages]
The tool also supports garble test
to run tests with obfuscated code,
and garble reverse
to de-obfuscate text such as stack traces.
See garble -h
for up to date usage information.
Produce a binary that works as well as a regular build, but that has as little information about the original source code as possible.
The tool is designed to be:
- Coupled with
cmd/go
, to support modules and build caching - Deterministic and reproducible, given the same initial source code
- Reversible given the original source, to de-obfuscate panic stack traces
The tool wraps calls to the Go compiler and linker to transform the Go build, in order to:
- Replace as many useful identifiers as possible with short base64 hashes
- Replace package paths with short base64 hashes
- Remove all build and module information
- Strip filenames and shuffle position information
- Strip debugging information and symbol tables via
-ldflags="-w -s"
- Obfuscate literals, if the
-literals
flag is given - Remove extra information, if the
-tiny
flag is given
By default, the tool obfuscates the packages under the current module. If not
running in module mode, then only the main package is obfuscated. To specify
what packages to obfuscate, set GOPRIVATE
, documented at go help private
.
Note that commands like garble build
will use the go
version found in your
$PATH
. To use different versions of Go, you can
install them
and set up $PATH
with them. For example, for Go 1.16.1:
$ go install golang.org/dl/go1.16.1@latest
$ go1.16.1 download
$ PATH=$(go1.16.1 env GOROOT)/bin:${PATH} garble build
Using the -literals
flag causes literal expressions such as strings to be
replaced with more complex variants, resolving to the same value at run-time.
This feature is opt-in, as it can cause slow-downs depending on the input code.
Literal expressions used as constants cannot be obfuscated, since they are
resolved at compile time. This includes any expressions part of a const
declaration.
When the -tiny
flag is passed, extra information is stripped from the resulting
Go binary. This includes line numbers, filenames, and code in the runtime that
prints panics, fatal errors, and trace/debug info. All in all this can make binaries
2-5% smaller in our testing, as well as prevent extracting some more information.
With this flag, no panics or fatal runtime errors will ever be printed, but they
can still be handled internally with recover
as normal. In addition, the
GODEBUG
environmental variable will be ignored.
Note that this flag can make debugging crashes harder, as a panic will simply
exit the entire program without printing a stack trace, and all source code
positions are set to line 1. Similarly, garble reverse
is generally not useful
in this mode.
garble build
should take about twice as long as go build
, as it needs to
complete two builds. The original build, to be able to load and type-check the
input code, and finally the obfuscated build.
Go's build cache is fully supported; if a first garble build
run is slow, a
second run should be significantly faster. This should offset the cost of the
double builds, as incremental builds in Go are fast.
Just like Go, garble builds are deterministic and reproducible if the inputs
remain the same: the version of Go, the version of Garble, and the input code.
This has significant benefits, such as caching builds or being able to use
garble reverse
to de-obfuscate stack traces.
However, it also means that an input package will be obfuscated in exactly the
same way if none of those inputs change. If you want two builds of your program
to be entirely different, you can use -seed
to provide a new seed for the
entire build, which will cause a full rebuild.
If any open source packages are being obfuscated, providing a custom seed can also provide extra protection. It could be possible to guess the versions of Go and garble given how a public package was obfuscated without a seed.
Most of these can improve with time and effort. The purpose of this section is to document the current shortcomings of this tool.
-
Exported methods are never obfuscated at the moment, since they could be required by interfaces and reflection. This area is a work in progress; see #3.
-
If your program breaks due to an issue with reflection please open an issue, we'll try to resolve new edge cases.
-
Go declarations exported for cgo via
//export
are not obfuscated. -
Go plugins are not currently supported; see #87.
We welcome new contributors. If you would like to contribute, see CONTRIBUTING.md as a starting point.