The sections are a bit more organized now. We add better docs for flags,
a new section on build speed, and we also remove the "withgo" helper as
it seems a bit over the top.
Fixes#275.
You can also declare a function to make multiple uses simpler:
### Literal obfuscation
```sh
$ withgo() {
local gocmd=go${1}
shift
Using the `-literals` flag causes literal expressions such as strings to be
replaced with more complex variants, resolving to the same value at run-time.
This feature is opt-in, as it can cause slow-downs depending on the input code.
PATH=$(${gocmd} env GOROOT)/bin:${PATH} "$@"
}
$ withgo 1.16.1 garble build
```
Literal expressions used as constants cannot be obfuscated, since they are
resolved at compile time. This includes any expressions part of a `const`
declaration.
### Tiny mode
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.
Note: if `-tiny` is passed, no panics, fatal 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.
### Speed
`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.
### Determinism and seeds
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.
### Caveats
@ -69,32 +102,23 @@ 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.
* Go plugins are not currently supported; see [#87](https://github.com/burrowers/garble/issues/87).
* There are cases where garble is a little too agressive with obfuscation, this may lead to identifiers getting obfuscated which are needed for reflection, e.g. to parse JSON into a struct; see [#162](https://github.com/burrowers/garble/issues/162). To work around this you can pass a hint to garble, that an type is used for reflection via passing it to `reflect.TypeOf` or `reflect.ValueOf` in the same file:
* It can be hard for garble to know what types will be used with
[reflection](https://golang.org/pkg/reflect), including JSON encoding or
decoding. If your program breaks because a type's names are obfuscated when
they should not be, you can add an explicit hint:
```go
// this is used for parsing json
type Message struct {
Command string
Args string
}
// never obfuscate the Message type
// Never obfuscate the Message type.
var _ = reflect.TypeOf(Message{})
```
### Tiny Mode
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.
Note: if `-tiny` is passed, no panics, fatal 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.
* Go plugins are not currently supported; see [#87](https://github.com/burrowers/garble/issues/87).
### Contributing
We actively seek new contributors, if you would like to contribute to garble use the
We welcome new contributors. If you would like to contribute, see
[CONTRIBUTING.md](CONTRIBUTING.md) as a starting point.
Daniel Martí
3 years ago
committed by
lu4p