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.
In Go 1.15, if a dependency is required but not listed in go.mod/go.sum,
it's resolved and added automatically.
This is changing in 1.16. From that release, one will have to explicitly
update the mod files via 'go mod tidy' or 'go get'.
To get ahead of the curve, start using -mod=readonly to get the same
behavior in 1.15, and fix all existing tests.
The only tests that failed were imports.txt and syntax.txt, the only
ones to require other modules. But since we're here, let's add the 'go'
line to all go.mod files as well.
The test intended to use an extra module to be obfuscated, rsc.io/quote,
which we were bundling in the local proxy as well. Unfortunately, the
use of GOPRIVATE also meant that we did not actually fetch the module
from the proxy, and we would instead do a full roundtrip to the internet
to "git clone" the actual upstream repository.
To prevent that roundtrip, instead use a locally replaced module. This
fits the syntax.txt test too, since it's one more edge case that we want
to make sure works well with garble. Since rsc.io/quote is used in
another test, simply make up our own tiny module.
Reduces a 'go test -run Syntax/syntax' run with warm cache from ~5s to
~0.5s, thanks to removing the multiple roundtrips. A warm 'go test' run
still sits at ~6s, since we still need that much CPU time in total.
While at it, fix a staticcheck warning and fix inconsistent indentation
in a couple of tests.
Added cleanup of the Comment field.
In some cases, the appearance of a comment in a random place
may break the compilation (e.g. cgo and runtime package).
This is safe because the Comment field cannot contain any directives.
Part of #149.
basic.txt just builds main.go without a module. Similarly, we leave
imports.txt without a GOPRIVATE, to test the 'go list -m' fallback.
For all other tests, explicitly set GOPRIVATE, to avoid two exec calls -
both 'go env GOPRIVATE' as well as 'go list -m'. Each of those calls
takes in the order of 10ms, so saving ~26 exec calls should easily add
to 200-300ms saved from 'go test -short'.
Fixes #2.
Line numbers are now obfuscated, via `//line` comments.
Filenames are now obfuscated via `//line` comments, instead of changing the actual filename.
New flag `-tiny` to reduce the binary size, at the cost of reversibility.
Instead of doing a 'go list' call every time we need to fetch a
dependency's export file, we now do a single 'go list' call before the
build begins. With the '-deps' flag, it gives us all the dependency
packages recursively.
We store that data in the gob format in a temporary file, and share it
with the future garble sub-processes via an env var.
This required lazy parsing of flags for the 'build' and 'test' commands,
since now we need to run 'go list' with the same package pattern
arguments.
Fixes#63.