reimplement import path obfuscation without goobj2 (#242)
We used to rely on a parallel implementation of an object file parser
and writer to be able to obfuscate import paths. After compiling each
package, we would parse the object file, replace the import paths, and
write the updated object file in-place.
That worked well, in most cases. Unfortunately, it had some flaws:
* Complexity. Even when most of the code is maintained in a separate
module, the import_obfuscation.go file was still close to a thousand
lines of code.
* Go compatibility. The object file format changes between Go releases,
so we were supporting Go 1.15, but not 1.16. Fixing the object file
package to work with 1.16 would probably break 1.15 support.
* Bugs. For example, we recently had to add a workaround for #224, since
import paths containing dots after the domain would end up escaped.
Another example is #190, which seems to be caused by the object file
parser or writer corrupting the compiled code and causing segfaults in
some rare edge cases.
Instead, let's drop that method entirely, and force the compiler and
linker to do the work for us. The steps necessary when compiling a
package to obfuscate are:
1) Replace its "package foo" lines with the obfuscated package path. No
need to separate the package path and name, since the obfuscated path
does not contain slashes.
2) Replace the "-p pkg/foo" flag with the obfuscated path.
3) Replace the "import" spec lines with the obfuscated package paths,
for those dependencies which were obfuscated.
4) Replace the "-importcfg [...]" file with a version that uses the
obfuscated paths instead.
The linker also needs that last step, since it also uses an importcfg
file to find object files.
There are three noteworthy drawbacks to this new method:
1) Since we no longer write object files, we can't use them to store
data to be cached. As such, the -debugdir flag goes back to using the
"-a" build flag to always rebuild all packages. On the plus side,
that caching didn't work very well; see #176.
2) The package name "main" remains in all declarations under it, not
just "func main", since we can only rename entire packages. This
seems fine, as it gives little information to the end user.
3) The -tiny mode no longer sets all lines to 0, since it did that by
modifying object files. As a temporary measure, we instead set all
top-level declarations to be on line 1. A TODO is added to hopefully
improve this again in the near future.
The upside is that we get rid of all the issues mentioned before. Plus,
garble now nearly works with Go 1.16, with the exception of two very
minor bugs that look fixable. A follow-up PR will take care of that and
start testing on 1.16.
Fixes #176.
Fixes #190.
3 years ago
|
|
|
skip # see https://github.com/burrowers/garble/issues/241
|
|
|
|
|
|
|
|
|
|
# Note that we need bar_test too.
|
|
|
|
|
env GOPRIVATE=test/bar,test/bar_test
|
|
|
|
|
|
|
|
|
|
# build the test binary
|
|
|
|
|
garble test -c
|
|
|
|
|
binsubstr bar.test$exe 'TestFoo' 'TestSeparateFoo'
|
|
|
|
|
! binsubstr bar.test$exe 'ImportedVar'
|
|
|
|
|
|
|
|
|
|
# run the tests
|
|
|
|
|
exec ./bar.test -test.v
|
|
|
|
|
stdout 'PASS.*TestFoo'
|
|
|
|
|
stdout 'PASS.*TestSeparateFoo'
|
|
|
|
|
|
|
|
|
|
[short] stop # no need to verify this with -short
|
|
|
|
|
|
|
|
|
|
# verify with regular cmd/go
|
|
|
|
|
go test -v
|
|
|
|
|
stdout 'PASS.*TestFoo'
|
|
|
|
|
|
|
|
|
|
-- go.mod --
|
|
|
|
|
module test/bar
|
|
|
|
|
|
|
|
|
|
go 1.16
|
|
|
|
|
-- bar.go --
|
|
|
|
|
package bar
|
|
|
|
|
|
|
|
|
|
func Foo() string { return "Foo" }
|
|
|
|
|
|
|
|
|
|
var ImportedVar = "imported var value"
|
|
|
|
|
-- bar_test.go --
|
|
|
|
|
package bar
|
|
|
|
|
|
|
|
|
|
import "testing"
|
|
|
|
|
|
|
|
|
|
func TestFoo(t *testing.T) {
|
|
|
|
|
t.Log(ImportedVar)
|
|
|
|
|
if Foo() != "Foo" {
|
|
|
|
|
t.FailNow()
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
-- bar_separate_test.go --
|
|
|
|
|
package bar_test
|
|
|
|
|
|
|
|
|
|
import (
|
|
|
|
|
"testing"
|
|
|
|
|
|
|
|
|
|
"test/bar"
|
|
|
|
|
)
|
|
|
|
|
|
|
|
|
|
func TestSeparateFoo(t *testing.T) {
|
|
|
|
|
t.Log(bar.ImportedVar)
|
|
|
|
|
if bar.Foo() != "Foo" {
|
|
|
|
|
t.FailNow()
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
-- main_test.go --
|
|
|
|
|
package bar
|
|
|
|
|
|
|
|
|
|
import (
|
|
|
|
|
"os"
|
|
|
|
|
"testing"
|
|
|
|
|
)
|
|
|
|
|
|
|
|
|
|
func TestMain(m *testing.M) {
|
|
|
|
|
os.Exit(m.Run())
|
|
|
|
|
}
|