First, I tried to follow my own past advice to only set GarbleActionID
if ToObfuscate is true. However, that broke at least three parts of
transformCompile, as the hash is used for more than I recalled.
Give up on that idea, because the current code is working as intended.
Better document what GarbleActionID is and what we use it for.
Second, now that https://go.dev/cl/348741 was shipped with Go 1.18,
using the logger when its output is io.Discard is already a no-op.
So we no longer need our debugf wrapper to apply the no-op logic.
First, two cleanups: unsafe and internal/abi are already in
runtimeAndDeps, so they are already not being obfuscated.
No need to repeat them in the other map.
Then, via trial and error, remove:
* runtime/pprof; it seems like we handle its runtime linknames well now.
* os/signal; unclear what "rebuilds don't work" meant, but it works now.
Our gogarble.txt test already does a full reproducible rebuild.
* crypto/x509/internal/macos; another linkname user that works now.
It is likely that we could remove one or two more packages already,
but it's best to move slowly and watch out for unexpected regressions.
It added packages which are only built with the boringcrypto build tag,
so trying to `go list` them will fail even though it doesn't matter.
While here, a few more minor cleanups:
1) Hide GarbleActionID and ToObfuscate from encoding/json, so that they
can't possibly collide with the fields consumed from `go list -json`.
2) Add test cases for `garble build` with packages that fail to load.
Note that this requires GOGARBLE=* to avoid its "does not match any
package to be built" error.
3) Remove the last use of interface{}, in a testdata file.
Fixes#531.
Returning a json or gob error directly to the user is generally not
helpful, as it lacks any form of context.
For example, from the json unmarshal of "go env -json":
$ garble build
invalid character 'w' looking for beginning of value
Also improve the error when the user ran garble in the wrong way,
resulting in no shared gob file. The context is now shorter, and we also
include the os.Open error in case it contains any useful details.
While here, apply Go tip's gofmt, which reformatted a godoc list.
For #523.
Now that we've released v0.6.0, that will be the last feature release to
feature support for Go 1.17. The upcoming v0.7.0 will be Go 1.18+.
Code-wise, the cleanup here isn't super noticeable,
but it will be easier to work on features like VCS-aware version
information and generics support without worrying about Go 1.17.
Plus, now CI is back to being much faster.
Note how "go 1.18" in go.mod makes "go mod tidy" more aggressive.
The added comment in main.go explains the situation in detail.
The added test is a minimization of the scenario, which failed:
> cd mod1
> garble -seed=${SEED1} build -v gopkg.in/garbletest.v2
> cd ../mod2
> garble -seed=${SEED1} build -v
[stderr]
test/main/mod2
# test/main/mod2
cannot load garble export file for gopkg.in/garbletest.v2: open […]/go-build/ed/[…]-garble-ZV[…]-d: no such file or directory
To work around the problem, we'll always add each package's
GarbleActionID to its build artifact, even when not using -seed.
This will get us the previous behavior with regards to the build cache,
meaning that we fix the recent regression.
The added variable doesn't make it to the final binary either.
While here, improve the cached file loading error's context,
and add an extra sanity check for duplicates on ListedPackages.
The default behavior of garble is to seed via the build inputs,
including the build IDs of the entire Go build of each package.
This works well as a default, and does give us determinism,
but it means that building for different platforms
will result in different obfuscation per platform.
Instead, when -seed is provided, don't use any other hash seed or salt.
This means that a particular Go name will be obfuscated the same way
as long as the seed, package path, and name itself remain constant.
In other words, when the user supplies a custom -seed,
we assume they know what they're doing in terms of storage and rotation.
Expand the README docs with more examples and detail.
Fixes#449.
Back in the day, we used to call toObfuscate anytime we needed to know
whether a package should be obfuscated.
More recently, we started computing via the ToObfuscate field,
which then gets shared with all sub-processes via sharedCache.
We still had two places that directly called toObfuscate.
Replace those with ToObfuscate, and inline toObfuscate into shared.go.
obfuscatedImportPath is also a potential footgun for main packages.
Some use cases always want the original "main" package name,
such as for use in the compiler's "-p main" flag,
while other cases want the obfuscated package import path,
such as the entries in importcfg files.
Since each of these call sites handles the edge case well,
obfuscatedImportPath now panics on main packages to avoid any misuse.
Finally, test that we never leak main package paths via ldflags.txt.
We never did, but it's good to make sure.
Overall, this avoids confusion and trims the size of main.go a bit.
Fix a staticcheck warning about unused code,
as well as an unparam warning and a missing copyright header.
We also bump the action versions to their latest releases,
and drop unnecessary "name" fields for self-describing steps.
Note that we drop the "go env" commands, as setup-go does that now.
Finally, I did briefly try to add caching,
but then realised it didn't help us at all. Document why.
There are two scenarios when it comes to embedding fields.
The first is easy, and we always handled it well:
type Named struct { Foo int }
type T struct { Named }
In this scenario, T ends up with an embedded field named "Named",
and a promoted field named "Foo".
Then there's the form with a type alias:
type Named struct { Foo int }
type Alias = Named
type T struct { Alias }
This case is different: T ends up with an embedded field named "Alias",
and a promoted field named "Foo".
Note how the field gets its name from the referenced type,
even if said type is just an alias to another type.
This poses two problems.
First, we must obfuscate the field T.Alias as the name "Alias",
and not as the name "Named" that the alias points to.
Second, we must be careful of cases where Named and Alias are declared
in different packages, as they will obfuscate the same name differently.
Both of those problems compounded in the reported issue.
The actual reason is that quic-go has a type alias in the form of:
type ConnectionState = qtls.ConnectionState
In other words, the entire problem boils down to a type alias which
points to a named type in a different package, where both types share
the same name. For example:
package parent
import "parent/p1"
type T struct { p1.SameName }
[...]
package p1
import "parent/p2"
type SameName = p2.SameName
[...]
package p2
type SameName struct { Foo int }
This broke garble because we had a heuristic to detect when an embedded
field was a type alias:
// Instead, detect such a "foreign alias embed".
// If we embed a final named type,
// but the field name does not match its name,
// then it must have been done via an alias.
// We dig out the alias's TypeName via locateForeignAlias.
if named.Obj().Name() != node.Name {
As the reader can deduce, this heuristic would incorrectly assume that
the snippet above does not embed a type alias, when in fact it does.
When obfuscating the field T.SameName, which uses a type alias,
we would correctly obfuscate the name "SameName",
but we would incorrectly obfuscate it with the package p2, not p1.
This would then result in build errors.
To fix this problem for good, we need to get rid of the heuristic.
Instead, we now mimic what was done for KnownCannotObfuscate,
but for embedded fields which use type aliases.
KnownEmbeddedAliasFields is now filled for each package
and stored in the cache as part of cachedOutput.
We can then detect the "embedded alias" case reliably,
even when the field is declared in an imported package.
On the plus side, we get to remove locateForeignAlias.
We also add a couple of TODOs to record further improvements.
Finally, add a test.
Fixes#466.
Obfuscating the runtime only needs to list the linknamed packages,
and doesn't need to know about their dependencies directly.
Refactor the script to return a "flat" list that includes all packages
we need, except those that we know the runtime already pulled in.
This allows us to simplify the script and avoid passing -deps to cmd/go.
Performance is unaffected, but I reckon it's worthwhile given how much
we simplified the script.
Longer term, it's also best to avoid using -deps when we don't need it,
as cmd/go could avoid computing information we don't need.
name old time/op new time/op delta
Build/NoCache-16 1.68s ± 1% 1.68s ± 0% ~ (p=1.000 n=5+5)
name old bin-B new bin-B delta
Build/NoCache-16 6.72M ± 0% 6.72M ± 0% +0.01% (p=0.008 n=5+5)
name old sys-time/op new sys-time/op delta
Build/NoCache-16 1.88s ± 1% 1.89s ± 2% ~ (p=0.548 n=5+5)
name old user-time/op new user-time/op delta
Build/NoCache-16 19.9s ± 1% 19.8s ± 0% ~ (p=0.421 n=5+5)
We were listing all of std, which certainly worked,
but was quite slow at over 200 packages.
In practice, we can only be missing up to 20-30 packages.
It was a good change as it fixed a severe bug,
but it also introduced a fairly noticeable slow-down.
The numbers are clear; this change shaves off multiple seconds when
obfuscating the runtime with a cold cache:
name old time/op new time/op delta
Build/NoCache-16 5.06s ± 1% 1.94s ± 1% -61.64% (p=0.008 n=5+5)
name old bin-B new bin-B delta
Build/NoCache-16 6.70M ± 0% 6.71M ± 0% +0.05% (p=0.008 n=5+5)
name old sys-time/op new sys-time/op delta
Build/NoCache-16 13.4s ± 2% 5.0s ± 2% -62.45% (p=0.008 n=5+5)
name old user-time/op new user-time/op delta
Build/NoCache-16 60.6s ± 1% 19.8s ± 1% -67.34% (p=0.008 n=5+5)
Since we only want to call "go list" one extra time,
instead of once for every package we find out we're missing,
we want to know what packages we could be missing in advance.
Resurrect a smarter version of the runtime-related script.
Finally, remove the runtime-related.txt test script,
as it has now been superseeded by the sanity checks in listPackage.
That is, obfuscating the runtime package will now panic if we are
missing any necessary package information.
To double check that we get the runtime's linkname edge case right,
make gogarble.txt use runtime/debug.WriteHeapDump,
which is implemented via a direct runtime linkname.
This ensures we don't lose test coverage from runtime-related.txt.
While here, add a TODO I forgot about, and run gofumpt.
Also bump all test timeouts slightly,
as the Mac and Windows hosted runners are a bit slow
and I've hit failures twice recently.
As of 1.18beta1. I used bash commands like:
diff -u <(go1.17.5 help build) <(gotip help build)
While here, supply -buildinfo=false and -buildvcs=false to go build.
We already remove that information by discarding the _gomod_.go file,
but we might as well pass the flags too.
If anything, it lets the toolchain avoid the work entirely.
Note that we can't use these flags on Go 1.17 for now, though.
Add a TODO that came to mind while writing this, too.
We went to great lengths to ensure garble builds are reproducible.
This includes how the tool itself works,
as its behavior should be the same given the same inputs.
However, we made one crucial mistake with the runtime package.
It has go:linkname directives pointing at other packages,
and some of those pointed packages aren't its dependencies.
Imagine two scenarios where garble builds the runtime package:
1) We run "garble build runtime". The way we handle linkname directives
calls listPackage on the target package, to obfuscate the target's
import path and object name. However, since we only obtained build
info of runtime and its deps, calls for some linknames such as
listPackage("sync/atomic") will fail. The linkname directive will
leave its target untouched.
2) We run "garble build std". Unlike the first scenario, all listPackage
calls issued by runtime's linkname directives will succeed, so its
linkname directive targets will be obfuscated.
At best, this can result in inconsistent builds, depending on how the
runtime package was built. At worst, the mismatching object names can
result in errors at link time, if the target packages are actually used.
The modified test reproduces the worst case scenario reliably,
when the fix is reverted:
> env GOCACHE=${WORK}/gocache-empty
> garble build -a runtime
> garble build -o=out_rebuild ./stdimporter
[stderr]
# test/main/stdimporter
JZzQivnl.NtQJu0H3: relocation target JZzQivnl.iioHinYT not defined
JZzQivnl.NtQJu0H3.func9: relocation target JZzQivnl.yz5z0NaH not defined
JZzQivnl.(*ypvqhKiQ).String: relocation target JZzQivnl.eVciBQeI not defined
JZzQivnl.(*ypvqhKiQ).PkgPath: relocation target JZzQivnl.eVciBQeI not defined
[...]
The fix consists of two steps. First, if we're building the runtime and
listPackage fails on a package, that means we ran into scenario 1 above.
To avoid the inconsistency, we fill ListedPackages with "go list [...] std".
This means we'll always build runtime as described in scenario 2 above.
Second, when building packages other than the runtime,
we only allow listPackage to succeed if we're listing a dependency of
the current package.
This ensures we won't run into similar reproducibility bugs in the future.
Finally, re-enable test-gotip on CI since this was the last test flake.
Not really meant for end users,
but they might still debug failures before filing bugs.
We add the -debug flag itself,
as well as machinery to deduplicate output lines.
There are quite a lot of them otherwise,
which aren't helpful and simply add noise.
In the future, if we always want to output a debug log line,
such as "choosing not to obfuscate here because X",
we can simply insert the unique position string.
Finally, turn all commented-out log.Printf calls to debugf.
Improve a few log lines to be more human-friendly,
and also add a few extras like how long it takes to load files.
We can improve the logging further in the future.
This seems like a good starting point.
The parent garble process parses the original flags,
as provided by the user via the command line.
Previously, those got stored in the shared cache file,
so that child processes spawned by toolexec could see them.
Unfortunately, this made the code relatively easy to misuse.
A child process would always see flagLiterals as zero value,
given that it should never see such a flag argument directly.
Similarly, one would have to be careful with cached options,
as they could only be consumed after the cache file is loaded.
Simplify the situation by deduplicating the storage of flags.
Now, the parent passes all flags onto children via toolexec.
One exception is GarbleDir, which now becomes an env var.
This seems in line with other top-level dirs like GARBLE_SHARED.
Finally, we turn -seed into a flag.Value,
which lets us implement its "set" behavior as part of flag.Parse.
Overall, we barely reduce the amount of code involved,
but we certainly remove a couple of footguns.
As part of the cleanup, we also introduce appendFlags.
Piggybacking off of GOPRIVATE is great for a number of reasons:
* People tend to obfuscate private code, whose package paths will
generally be in GOPRIVATE already
* Its meaning and syntax are well understood
* It allows all the flexibility we need without adding our own env var
or config option
However, using GOPRIVATE directly has one main drawback.
It's fairly common to also want to obfuscate public dependencies,
to make the code in private packages even harder to follow.
However, using "GOPRIVATE=*" will result in two main downsides:
* GONOPROXY defaults to GOPRIVATE, so the proxy would be entirely disabled.
Downloading modules, such as when adding or updating dependencies,
or when the local cache is cold, can be less reliable.
* GONOSUMDB defaults to GOPRIVATE, so the sumdb would be entirely disabled.
Adding entries to go.sum, such as when adding or updating dependencies,
can be less secure.
We will continue to consume GOPRIVATE as a fallback,
but we now expect users to set GOGARBLE instead.
The new logic is documented in the README.
While here, rewrite some uses of "private" with "to obfuscate",
to make the code easier to follow and harder to misunderstand.
Fixes#276.
We rely on importcfg files to load type info for obfuscated packages.
We use this type information to remember what names we didn't obfuscate.
Unfortunately, indirect dependencies aren't listed in importcfg files,
so we relied on extra "go list -toolexec" calls to locate object files.
This worked fine, but added a significant amount of complexity.
The extra "go list -export -toolexec=garble" invocations weren't slow,
as they avoided rebuilding or re-obfuscating thanks to the build cache.
Still, it was hard to reason about how garble runs during a build
if we might have multiple layers of -toolexec invocations.
Instead, record the export files we encounter in an incremental map,
and persist it in the build cache via the gob file we're already using.
This way, each garble invocation knows where all object files are,
even those for indirect imports.
One wrinkle is that importcfg files can point to temporary object files.
In that case, figure out its final location in the build cache.
This requires hard-coding a bit of knowledge about how GOCACHE works,
but it seems relatively harmless given how it's very little code.
Plus, if GOCACHE ever changes, it will be obvious when our code breaks.
Finally, add a TODO about potentially saving even more work.
While investigating a bug report,
I noticed that garble was writing to the same temp file twice.
At best, writing to the same path on disk twice is wasteful,
as the design is careful to be deterministic and use unique paths.
At worst, the two writes could cause races at the filesystem level.
To prevent either of those situations,
we now create files with os.OpenFile and os.O_EXCL,
meaning that we will error if the file already exists.
That change uncovered a number of such unintended cases.
First, transformAsm would write obfuscated Go files twice.
This is because the Go toolchain actually runs:
[...]/asm -gensymabis [...] foo.s bar.s
[...]/asm [...] foo.s bar.s
That is, the first run is only meant to generate symbol ABIs,
which are then used by the compiler.
We need to obfuscate at that first stage,
because the symbol ABI descriptions need to use obfuscated names.
However, having already obfuscated the assembly on the first stage,
there is no need to do so again on the second stage.
If we detect gensymabis is missing, we simply reuse the previous files.
This first situation doesn't seem racy,
but obfuscating the Go assembly files twice is certainly unnecessary.
Second, saveKnownReflectAPIs wrote a gob file to the build cache.
Since the build cache can be kept between builds,
and since the build cache uses reproducible paths for each build,
running the same "garble build" twice could overwrite those files.
This could actually cause races at the filesystem level;
if two concurrent builds write to the same gob file on disk,
one of them could end up using a partially-written file.
Note that this is the only of the three cases not using temporary files.
As such, it is expected that the file may already exist.
In such a case, we simply avoid overwriting it rather than failing.
Third, when "garble build -a" was used,
and when we needed an export file not listed in importcfg,
we would end up calling roughly:
go list -export -toolexec=garble -a <dependency>
This meant we would re-build and re-obfuscate those packages.
Which is unfortunate, because the parent process already did via:
go build -toolexec=garble -a <main>
The repeated dependency builds tripped the new os.O_EXCL check,
as we would try to overwrite the same obfuscated Go files.
Beyond being wasteful, this could again cause subtle filesystem races.
To fix the problem, avoid passing flags like "-a" to nested go commands.
Overall, we should likely be using safer ways to write to disk,
be it via either atomic writes or locked files.
However, for now, catching duplicate writes is a big step.
I have left a self-assigned TODO for further improvements.
CI on the pull request found a failure on test-gotip.
The failure reproduces on master, so it seems to be related to gotip,
and not a regression introduced by this change.
For now, disable test-gotip until we can investigate.
In particular, internal/abi now has some actual code,
so obfuscating those literals was breaking as expected.
Document how to update the list in the future as well.
The change above gets "go test" to just one test failure on:
go version devel go1.18-578ada410d Tue Nov 9 22:58:24 2021 +0000 linux/amd64
We also move the doc about why we disable GarbleLiterals,
so that it's next to where the disabling happens.
While here, we also rename GarbleLiterals to ObfuscateLiterals,
as we have been trying to move away from "to garble" as a verb.
Finally, limit the verbosity of diffoscope.
One test was failing for me, and diffoscope printed thousands of lines.
Not particularly useful when I'm trying to skim test results.
Usually, seeing a few dozen lines of output is enough.
Updates #385.
Also update linkname directives of public packages,
to allow the package where something is linknamed to to be
obfuscated regardless.
Public packages can now depend on private packages.
Now that Go 1.17.x is out,
we no longer need to worry about users on Go 1.15.x.
Since Go 1.16, the best way to install programs has been "go install":
https://golang.org/doc/go1.16#go-command
This method does not interfere with the current module,
and allows selecting a version such as "latest" or "master".
Our recent work in fieldToAlias worked well when the embedded field
declaration (using an alias) was in the same package as the use of that
field. We would have the *ast.Ident for the field declaration, so
types.Info.Uses would give us the TypeName for the alias.
Unfortunately, if the declaration was in a dependency package, we did
not have that same *ast.Ident, as we weren't parsing the source code for
dependencies for type-checking. This resulted in us incorrectly
obfuscating the use of such an embedded field:
> garble build
[stderr]
# test/main
JtzmzxWf.go:4: unknown field 'ExternalForeignAlias' in struct literal of type _BdSNiEL.Vcs_smer
To fix this, look through the direct imports of the package defining the
field to find an alias under the exact same name. Not a foolproof
solution, as there's a TODO, but it should work for most cases.
Fixes the obfuscation of google.golang.org/grpc/internal/status, too.
Updates #349.
Packages P1 and P2 can define identical struct types T1 and T2, and one
can convert from type T1 to T2 or vice versa.
The spec defines two identical struct types as:
Two struct types are identical if they have the same sequence of
fields, and if corresponding fields have the same names, and
identical types, and identical tags. Non-exported field names
from different packages are always different.
Unfortunately, garble broke this: since we obfuscated field names
differently depending on the package, cross-package conversions like the
case above would result in typechecking errors.
To fix this, implement Joe Tsai's idea: hash struct field names with the
string representation of the entire struct. This way, identical struct
types will have their field names obfuscated in the same way in all
packages across a build.
Note that we had to refactor "reverse" a bit to start using transformer,
since now it needs to keep track of struct types as well.
This failure was affecting the build of google.golang.org/protobuf,
since it makes regular use of cross-package struct conversions.
Note that the protobuf module still fails to build, but for other
reasons. The package that used to fail now succeeds, so the build gets a
bit further than before. #240 tracks adding relevant third-party Go
modules to CI, so we'll track the other remaining failures there.
Fixes#310.
In the worst case scenario, when GOPRIVATE isn't set at all, we would
run these three commands:
* "go env GOPRIVATE", to fetch GOPRIVATE itself
* "go list -m", for GOPRIVATE's fallback
* "go version", to check the version of Go being used
Now that we support Go 1.16 and later, all these three can be obtained
via "go env -json":
$ go env -json GOPRIVATE GOMOD GOVERSION
{
"GOMOD": "/home/mvdan/src/garble/go.mod",
"GOPRIVATE": "",
"GOVERSION": "go1.16.3"
}
Note that we don't get the module path directly, but we can use the
x/mod/modfile Go API to parse it from the GOMOD file cheaply.
Notably, this also simplifies our Go version checking logic, as now we
get just the version string without the "go version" prefix and
"GOOS/GOARCH" suffix we don't care about.
This makes our code a bit more maintainable and robust. When running a
short incremental build, we can also see a small speed-up, as saving two
"go" invocations can save a few milliseconds:
name old time/op new time/op delta
Build/Cache-8 168ms ± 0% 166ms ± 1% -1.26% (p=0.009 n=6+6)
name old bin-B new bin-B delta
Build/Cache-8 6.36M ± 0% 6.36M ± 0% +0.12% (p=0.002 n=6+6)
name old sys-time/op new sys-time/op delta
Build/Cache-8 222ms ± 2% 219ms ± 3% ~ (p=0.589 n=6+6)
name old user-time/op new user-time/op delta
Build/Cache-8 857ms ± 1% 846ms ± 1% -1.31% (p=0.041 n=6+6)
In 6898d61637, we switched from using action IDs from "go list
-toolexec=garble" to those from the original "go list". We still wanted
the obfuscation and hashing to change if the version of garble changes,
so we hashed that "original action ID" with garble's own content ID, and
called the new hash "garble action ID".
While working on a different patch, I noticed something weird: with the
new mechanism, adding or removing flags like -literals did not alter
those hashes, unlike the old method. This is because the old method used
ownContentID, which includes such bits of information, but the new
method does not.
Change that, and add a test that locks in the behavior we want. In
seed.txt, we check that a single function name gets hashed in particular
ways in different scenarios.
Note that we use a mix of "cmp" and "! bincmp", since the former has no
negated form.
While at it, the seed.txt test is revamped a bit. Now, we only run with
-literals once, as this test is mainly about -seed. We also declare seed
strings once, as environment variables, which makes it easier to track
what each step is doing.
Mainly comments. "garble" refers to the tool, but the verb and adjective
is more intuitive as "obfuscate" and "obfuscated" instead of "garble"
and "garbled".
Explain why we print the random seed on failure, and why we accept
base64 padding when we don't use it.
While at it, the flagOptions.Random field is unused, so remove it. It
also seems wrong for it to exist; the random value is only for the seed
flag, which already has a field of its own.
With the many refactors building up to v0.1.0, we broke "garble test" as
we no longer dealt with test packages well.
Luckily, now that we can depend on TOOLEXEC_IMPORTPATH, we can support
the test command again, as we can always figure out what package we're
currently compiling, without having to track a "main" package.
Note that one major pitfall there is test packages, where
TOOLEXEC_IMPORTPATH does not agree with ImportPath from "go list -json".
However, we can still work around that with a bit of glue code, which is
also copiously documented.
The second change necessary is to consider test packages private
depending on whether their non-test package is private or not. This can
be done via the ForTest field in "go list -json".
The third change is to obfuscate "_testmain.go" files, which are the
code-generated main functions which actually run tests. We used to not
need to obfuscate them, since test function names are never obfuscated
and we used to not obfuscate import paths at compilation time. Now we do
rewrite import paths, so we must do that for "_testmain.go" too.
The fourth change is to re-enable test.txt, and expand it with more
sanity checks and edge cases.
Finally, document "garble test" again.
Fixes#241.
Now that we've dropped support for Go 1.15.x, we can finally rely on
this environment variable for toolexec calls, present in Go 1.16.
Before, we had hacky ways of trying to figure out the current package's
import path, mostly from the -p flag. The biggest rough edge there was
that, for main packages, that was simply the package name, and not its
full import path.
To work around that, we had a restriction on a single main package, so
we could work around that issue. That restriction is now gone.
The new code is simpler, especially because we can set curPkg in a
single place for all toolexec transform funcs.
Since we can always rely on curPkg not being nil now, we can also start
reusing listedPackage.Private and avoid the majority of repeated calls
to isPrivate. The function is cheap, but still not free.
isPrivate itself can also get simpler. We no longer have to worry about
the "main" edge case. Plus, the sanity check for invalid package paths
is now unnecessary; we only got malformed paths from goobj2, and we now
require exact matches with the ImportPath field from "go list -json".
Another effect of clearing up the "main" edge case is that -debugdir now
uses the right directory for main packages. We also start using
consistent debugdir paths in the tests, for the sake of being easier to
read and maintain.
Finally, note that commandReverse did not need the extra call to "go
list -toolexec", as the "shared" call stored in the cache is enough. We
still call toolexecCmd to get said cache, which should probably be
simplified in a future PR.
While at it, replace the use of the "-std" compiler flag with the
Standard field from "go list -json".
This mainly cleans up the few bits of code where we explicitly kept
support for Go 1.15.x. With v0.1.0 released, we can drop support now,
since the next v0.2.0 release will only support Go 1.16.x.
Also updates all modules, including test ones, to 'go 1.16'.
Note that the TOOLEXEC_IMPORTPATH refactor is not done here, despite all
the TODOs about doing so when we drop 1.15 support. This is because that
refactor needs to be done carefully and might have side effects, so it's
best to keep it to a separate commit.
Finally, update the deps.
First, we had some link errors such as:
cannot find package J6OzO8GN (using -importcfg)
This was caused by the code that writes an updated importcfg, which did
not handle import maps well. That code is now fixed, and we also add an
obfuscatedImportPath method for clarity.
Once fixed, we ran into other link errors:
Pw3g97ww.addVW: relocation target Pw3g97ww.addVWlarge not defined
After some digging, the cause of those is assembly code that we do not
yet support obfuscating. #261 tracks that.
Meanwhile, to fix "GOPRIVATE=* garble build" and to be able to have a
test for the original import path bug, we add the packages which use
that form of assembly code to runtimeRelated - math/big and
crypto/sha512. There might be more, but these were the ones found by
trying to link crypto/tls, a fairly common dependency.
Fixes#256.
We use it to get the content ID of garble's binary, which is used for
both the garble action IDs, as well as 'go tool compile -V=full'.
Since those two happen in separate processes, both used to call 'go tool
buildid' separately. Store it in the gob cache the first time, and reuse
it the second time.
Since each call to cmd/go costs about 10ms (new process, running its
many init funcs, etc), this results in a nice speed-up for our small
benchmark. Most builds will take many seconds though, so note that a
~15ms speedup there will likely not be noticeable.
While at it, simplify the buildInfo global, as now it just contains a
map representation of the -importcfg contents. It now has better names,
docs, and a simpler representation.
We also stop using the term "garbled import", as it was a bit confusing.
"obfuscated types.Package" is a much better description.
name old time/op new time/op delta
Build-8 106ms ± 1% 92ms ± 0% -14.07% (p=0.010 n=6+4)
name old bin-B new bin-B delta
Build-8 6.60M ± 0% 6.60M ± 0% -0.01% (p=0.002 n=6+6)
name old sys-time/op new sys-time/op delta
Build-8 208ms ± 5% 149ms ± 3% -28.27% (p=0.004 n=6+5)
name old user-time/op new user-time/op delta
Build-8 433ms ± 3% 384ms ± 3% -11.35% (p=0.002 n=6+6)
When we obfuscate a name, what we do is hash the name with the action ID
of the package that contains the name. To ensure that the hash changes
if the garble tool changes, we used the action ID of the obfuscated
build, which is different than the original action ID, as we include
garble's own content ID in "go tool compile -V=full" via -toolexec.
Let's call that the "obfuscated action ID". Remember that a content ID
is roughly the hash of a binary or object file, and an action ID
contains the hash of a package's source code plus the content IDs of its
dependencies.
This had the advantage that it did what we wanted. However, it had one
massive drawback: when we compile a package, we only have the obfuscated
action IDs of its dependencies. This is because one can't have the
content ID of dependent packages before they are built.
Usually, this is not a problem, because hashing a foreign name means it
comes from a dependency, where we already have the obfuscated action ID.
However, that's not always the case.
First, go:linkname directives can point to any symbol that ends up in
the binary, even if the package is not a dependency. So garble could
only support linkname targets belonging to dependencies. This is at the
root of why we could not obfuscate the runtime; it contains linkname
directives targeting the net package, for example, which depends on runtime.
Second, some other places did not have an easy access to obfuscated
action IDs, like transformAsm, which had to recover it from a temporary
file stored by transformCompile.
Plus, this was all pretty expensive, as each toolexec sub-process had to
make repeated calls to buildidOf with the object files of dependencies.
We even had to use extra calls to "go list" in the case of indirect
dependencies, as their export files do not appear in importcfg files.
All in all, the old method was complex and expensive. A better mechanism
is to use the original action IDs directly, as listed by "go list"
without garble in the picture.
This would mean that the hashing does not change if garble changes,
meaning weaker obfuscation. To regain that property, we define the
"garble action ID", which is just the original action ID hashed together
with garble's own content ID.
This is practically the same as the obfuscated build ID we used before,
but since it doesn't go through "go tool compile -V=full" and the
obfuscated build itself, we can work out *all* the garble action IDs
upfront, before the obfuscated build even starts.
This fixes all of our problems. Now we know all garble build IDs
upfront, so a bunch of hacks can be entirely removed. Plus, since we
know them upfront, we can also cache them and avoid repeated calls to
"go tool buildid".
While at it, make use of the new BuildID field in Go 1.16's "list -json
-export". This avoids the vast majority of "go tool buildid" calls, as
the only ones that remain are 2 on the garble binary itself.
The numbers for Go 1.16 look very good:
name old time/op new time/op delta
Build-8 146ms ± 4% 101ms ± 1% -31.01% (p=0.002 n=6+6)
name old bin-B new bin-B delta
Build-8 6.61M ± 0% 6.60M ± 0% -0.09% (p=0.002 n=6+6)
name old sys-time/op new sys-time/op delta
Build-8 321ms ± 7% 202ms ± 6% -37.11% (p=0.002 n=6+6)
name old user-time/op new user-time/op delta
Build-8 538ms ± 4% 414ms ± 4% -23.12% (p=0.002 n=6+6)
There was one bug keeping the command below from working:
GOPRIVATE='*' garble build std
The bug is rather obscure; I'm still working on a minimal reproducer
that I can submit upstream, and I'm not yet convinced about where the
bug lives and how it can be fixed.
In short, the command would fail with:
typecheck error: /go/src/crypto/ecdsa/ecdsa.go:122:12: cannot use asn1.SEQUENCE (constant 48 of type asn1.Tag) as asn1.Tag value in argument to b.AddASN1
Note that the error is ambiguous; there are two asn1 packages, but they
are actually mismatching. We can see that by manually adding debug
prints to go/types:
constant: asn1.SEQUENCE (constant 48 of type golang.org/x/crypto/cryptobyte/asn1.Tag)
argument type: vendor/golang.org/x/crypto/cryptobyte/asn1.Tag
It's clear that, for some reason, go/types ends up confused and loading
a vendored and non-vendored version of asn1. There also seems to be no
way to work around this with our lookup function, as it just receives an
import path as a parameter, and returns an object file reader.
For now, work around the issue by *not* using a custom lookup function
in this rare edge case involving vendored dependencies in std packages.
The added code has a lengthy comment explaining the reasoning.
I still intend to investigate this further, but there's no reason to
keep garble failing if we can work around the bug.
Fixes#223.
Unexported names are a bit tricky, since they are not listed in the
export data file. Perhaps unsurprisingly, it's only meant to expose
exported objects.
One option would be to go back to adding an extra header to the export
data file, containing the unexported methods in a map[string]T or
[]string. However, we have an easier route: just parse the Go files and
look up the names directly.
This does mean that we parse the Go files every time "reverse" runs,
even if the build cache is warm, but that should not be an issue.
Parsing Go files without any typechecking is very cheap compared to
everything else we do. Plus, we save having to load go/types information
from the build cache, or having to load extra headers from export files.
It should be noted that the obfuscation process does need type
information, mainly to be careful about which names can be obfuscated
and how they should be obfuscated. Neither is a worry here; all names
belong to a single package, and it doesn't matter if some aren't
actually obfuscated, since the string replacements would simply never
trigger in practice.
The test includes an unexported func, to test the new feature. We also
start reversing the obfuscation of import paths. Now, the test's reverse
output is as follows:
goroutine 1 [running]:
runtime/debug.Stack(0x??, 0x??, 0x??)
runtime/debug/stack.go:24 +0x??
test/main/lib.ExportedLibFunc(0x??, 0x??, 0x??, 0x??)
p.go:6 +0x??
main.unexportedMainFunc(...)
C.go:2
main.main()
z.go:3 +0x??
The only major missing feature is positions and filenames. A follow-up
PR will take care of those.
Updates #5.
For now, this only implements reversing of exported names which are
hashed with action IDs. Many other kinds of obfuscation, like positions
and private names, are not yet implemented.
Note that we don't document this new command yet on purpose, since it's
not finished.
Some other minor cleanups were done for future changes, such as making
transformLineInfo into a method that also receives the original
filename, and making header names more self-describing.
Updates #5.
Each compile and link sub-process created its own temporary directory,
to be cleaned up shortly after. Moreover, we also had the global
gob-encoded temporary file.
Instead, place all of those under a single, start-to-end temporary
directory. This is cleaner for the end user, and easier to maintain for
us.
A big plus is that we can also get rid of the confusing deferred global,
as it was mostly used to clean up these extra temp dirs. The only
remaining use was post-compile code, which is now an explicit func
returned by each "transform" func.
While at it, clean up the math/rand seeding code a bit and add a debug
log line, and stop shadowing a cmd string with a cmd *exec.Cmd.
Fixes#147.
main.go includes a lengthy comment that documents this edge case, why it
happened, and how we are fixing it. To summarize, we should no longer
error with a build error in those cases. Read the comment for details.
A few other minor changes were done to allow writing this patch.
First, the actionID and contentID funcs were renamed, since they started
to collide with variable names.
Second, the logging has been improved a bit, which allowed me to debug
the issue.
Third, the "cache" global shared by all garble sub-processes now
includes the necessary parameters to run "go list -toolexec", including
the path to garble and the build flags being used.
Thanks to lu4p for writing a test case, which also applied gofmt to that
testdata Go file.
Fixes#180.
Closes#181, since it includes its test case.
Previously, we were never obfuscating runtime and its direct
dependencies. Unfortunately, due to linkname, the runtime package is
actually closely related to dozens of other std packages as well.
Until we can obfuscate the runtime and properly support go:linkname
directives, obfuscating fewer std packages is a better outcome than
breaking and not producing any obfuscated code at all.
The added test case is building runtime/pprof, which used to cause
failures:
# runtime/pprof
/go/src/runtime/pprof/label.go:27:21: undefined: context.Context
/go/src/runtime/pprof/label.go:59:21: undefined: context.Context
/go/src/runtime/pprof/label.go:93:16: undefined: context.Context
/go/src/runtime/pprof/label.go:101:20: undefined: context.Context
The net package was also very close to obfuscating properly thanks to
this change, so its test is now run as well. The only other remaining
fix was to not obfuscate fields on cgo types, since those aren't
obfuscated at the moment.
The map is pretty long, but it's only a temporary solution and the
command to obtain the list again is included. Never obfuscating the
entire std library is also an option, but it's a bit unnecessary.
Fixes#134.
Previously garble heavily used env vars to share data between processes.
This also makes it easy to share complex data between processes.
The complexity of main.go is considerably reduced.
Daniel Martí
lu4p
Andrew LeFevre