We were obfuscating reflect's package path and its declared names,
but the toolchain wants to detect the presence of method reflection
to turn down the aggressiveness of dead code elimination.
Given that the obfuscation broke the detection,
we could easily end up in crashes when making reflect calls:
fatal error: unreachable method called. linker bug?
goroutine 1 [running]:
runtime.throw({0x50c9b3?, 0x2?})
runtime/panic.go:1047 +0x5d fp=0xc000063660 sp=0xc000063630 pc=0x43245d
runtime.unreachableMethod()
runtime/iface.go:532 +0x25 fp=0xc000063680 sp=0xc000063660 pc=0x40a845
runtime.call16(0xc00010a360, 0xc00000e0a8, 0x0, 0x0, 0x0, 0x8, 0xc000063bb0)
runtime/wcS9OpRFL:728 +0x49 fp=0xc0000636a0 sp=0xc000063680 pc=0x45eae9
runtime.reflectcall(0xc00001c120?, 0x1?, 0x1?, 0x18110?, 0xc0?, 0x1?, 0x1?)
<autogenerated>:1 +0x3c fp=0xc0000636e0 sp=0xc0000636a0 pc=0x462e9c
Avoid obfuscating the three names which cause problems: "reflect",
"Method", and "MethodByName".
While here, we also teach obfuscatedImportPath to skip "runtime",
as I also saw that the toolchain detects it for many reasons.
That wasn't a problem yet, as we do not obfuscate the runtime,
but it was likely going to become a problem in the future.
We can drop the code that kicked in when GOGARBLE was empty.
We can also add the value in addGarbleToHash unconditionally,
as we never allow it to be empty.
In the tests, remove all GOGARBLE lines where it just meant "obfuscate
everything" or "obfuscate the entire main module".
cgo.txtar had "obfuscate everything" as a separate step,
so remove it entirely.
linkname.txtar started failing because the imported package did not
import strings, so listPackage errored out. This wasn't a problem when
strings itself wasn't obfuscated, as transformLinkname silently left
strings.IndexByte untouched. It is a problem when IndexByte does get
obfuscated. Make that kind of listPackage error visible, and fix it.
reflect.txtar started failing with "unreachable method" runtime throws.
It's not clear to me why; it appears that GOGARBLE=* makes the linker
think that ExportedMethodName is suddenly unreachable.
Work around the problem by making the method explicitly reachable,
and leave a TODO as a reminder to investigate.
Finally, gogarble.txtar no longer needs to test for GOPRIVATE.
The rest of the test is left the same, as we still want the various
values for GOGARBLE to continue to work just like before.
Fixes#594.
Up to this point, -debugdir only included obfuscated Go files.
Include assembly files and their headers as well.
While here, ensure that -debugdir supports the standard library too,
and that it behaves correctly with build tags as well.
Also use more consistent names for path strings, to clarify which are
only the basename, and which are the obfuscated version.
Some big changes landed in Go for the upcoming 1.20.
While here, remove the use of GOGC=off with make.bash,
as https://go.dev/cl/436235 makes that unnecessary now.
We were still leaking the filenames for assembly files.
In our existing asm.txtar test's output binary,
the string `test/main/garble_main_amd64.s` was present.
This leaked full import paths on one hand,
and the filenames of each assembly file on the other.
We avoid this in Go files by using `/*line` directives,
but those are not supported in assembly files.
Instead, obfuscate the paths in the temporary directory.
Note that we still need a separate temporary directory per package,
because otherwise any included header files might collide.
We must remove the `main` package panic in obfuscatedImportPath,
as we now need to use that function for all packages.
While here, remove the outdated comment about `-trimpath`.
Fixes#605.
A main package can be imported in one edge case we weren't testing:
when the same main package has any tests, which implicitly import main.
Before the fix, we would panic:
> garble test -v ./...
# test/bar/somemaintest.test
panic: main packages should never need to obfuscate their import paths
The last change made it so that hashWithCustomSalt does not always end
up with 8 base64 characters, which is a good change for the sake of
avoiding easy patterns in obfuscated code.
However, the docs weren't updated accordingly, and it wasn't
particularly clear that the byte giving us randomness wasn't part of the
resulting base64-encoded name.
First, refactor the code to only feed as many checksum bytes to the
base64 encoder as necessary, which is 12.
This shrinks b64NameBuffer and saves us some base64 encoding work.
Second, use the first checksum byte that we don't use, the 13th,
as the source of the randomness.
Note how before we used a base64-encoded byte for the randomness,
which isn't great as that byte was only one of 63 characters,
whereas a checksum byte is one of 256.
Third, update the docs so that the code is as clear as possible.
This is particularly important given that we have no tests.
With debug prints in the gogarble.txt test, we can see that the
randomness in hash lengths is working as intended:
# test/main/stdimporter
hashLength = 13
hashLength = 8
hashLength = 12
hashLength = 15
hashLength = 10
hashLength = 15
hashLength = 9
hashLength = 8
hashLength = 15
hashLength = 15
hashLength = 12
hashLength = 10
hashLength = 13
hashLength = 13
hashLength = 8
hashLength = 15
hashLength = 11
Finally, add a regression test that will complain if we end up with
hashed names that reuse the same length too often.
Out of eight hashed names, the test will fail if six end up with the
same length, as that is incredibly unlikely given that each should pick
one of eight lengths with a fair distribution.
One more package that further unblocks obfuscating the runtime.
The issue was the TODO we already had about go:linkname directives with
just one argument, which are used in the syscall package.
While here, factor out the obfuscation of linkname directives into
transformLinkname, as it was starting to get a bit complex.
We now support debug logging as well, while still being able to use
"early returns" for some cases where we bail out.
We also need listPackage to treat all runtime sub-packages like it does
runtime itself, as `runtime/internal/syscall` linknames into `syscall`
without it being a dependency as well.
Finally, add a regression test that, without the fix,
properly spots that the syscall package was not obfuscated:
FAIL: testdata/script/gogarble.txtar:41: unexpected match for ["syscall.RawSyscall6"] in out
Updates #193.
See https://golang.org/issue/28749. The improved asm test would fail:
go parse: $WORK/imported/imported_amd64.s:1:1: expected 'package', found TEXT (and 2 more errors)
because we would incorrectly parse a non-Go file as a Go file.
Add a workaround. The original reporter's reproducer with go-ethereum
works now, as this was the last hiccup.
Fixes#555.
The reverse feature relied on `GoFiles` from `go list`,
but that list may not be enough to typecheck a package:
typecheck error: $WORK/main.go:3:15: undeclared name: longMain
`go help list` shows:
GoFiles []string // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
CgoFiles []string // .go source files that import "C"
CompiledGoFiles []string // .go files presented to compiler (when using -compiled)
In other words, to mimic the same list of Go files fed to the compiler,
we want CompiledGoFiles.
Note that, since the cgo files show up as generated files,
we currently do not support reversing their filenames.
That is left as a TODO for now.
Updates #555.
Assembly files can include header files within the same Go module,
and those header files can include "defines" which refer to Go names.
Since those Go names are likely being obfuscated,
we need to replace them just like we do in assembly files.
The added mechanism is rather basic; we add two TODOs to improve it.
This should help when building projects like go-ethereum.
Fixes#553.
This way, the child process knows that it's running a toolchain command
via -toolexec without having to guess via filepath.IsAbs.
While here, improve the docs and tests a bit.
Following the best practices from upstream.
In particular, the "txt" extension is somewhat ambiguous.
This may cause some conflicts due to the git diff noise,
but hopefully we won't ever do this again.
Daniel Martí