Strip stdlib paths from binaries (#971)

Set GOROOT_FINAL to a constant string ('GOROOT') when
linking. Normally, the actual path to GOROOT is set in linked
binaries, which results in non-reproducible builds. GOROOT_FINAL
provides a constant replacement.

Also, added a test for common reproducibility problems.

Fixes #969

go/tools/builders/env.go

@@ -71,6 +71,7 @@ func (env *GoEnv) Env() []string {
 	}
 	return []string{
 		fmt.Sprintf("GOROOT=%s", env.absRoot()),
+		"GOROOT_FINAL=GOROOT",
 		fmt.Sprintf("TMP=%s", "/tmp"), // TODO: may need to be different on windows
 		fmt.Sprintf("GOOS=%s", env.goos),
 		fmt.Sprintf("GOARCH=%s", env.goarch),

tests/reproducible_binary/BUILD.bazel

@@ -0,0 +1,25 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["hello.go"],
+    importpath = "github.com/bazelbuild/rules_go/tests/reproducible_binary",
+    visibility = ["//visibility:private"],
+)
+
+go_binary(
+    name = "reproducible_binary",
+    importpath = "github.com/bazelbuild/rules_go/tests/reproducible_binary",
+    library = ":go_default_library",
+    visibility = ["//visibility:public"],
+)
+
+# keep
+go_test(
+    name = "go_default_test",
+    srcs = ["reproducible_binary_test.go"],
+    args = ["$(location :reproducible_binary)"],
+    data = [":reproducible_binary"],
+    importpath = "github.com/bazelbuild/rules_go/tests/reproducible_binary",
+    rundir = ".", # run in repo root instead of test dir
+)

tests/reproducible_binary/hello.go

@@ -0,0 +1,25 @@
+/* Copyright 2017 The Bazel Authors. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import "fmt"
+
+func main() {
+	// Call a function from the standard library. The test will check whether
+	// the path to the source file that defines this function gets embedded
+	// in the binary.
+	fmt.Println("Hello, world!")
+}

tests/reproducible_binary/reproducible_binary_test.go

@@ -0,0 +1,81 @@
+/* Copyright 2017 The Bazel Authors. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// reproducible_binary_test checks that a given binary DOES NOT contain
+// strings that match the GOROOT, the current user's name, or the
+// current user's home directory.
+package main
+
+import (
+	"bytes"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/user"
+	"regexp"
+	"testing"
+)
+
+var allStrings [][]byte
+var currentUser *user.User
+
+func TestMain(m *testing.M) {
+	log.SetFlags(0)
+	if len(os.Args) != 2 {
+		log.Fatalf("usage: %s <binary>\n", os.Args[0])
+	}
+
+	binaryData, err := ioutil.ReadFile(os.Args[1])
+	if err != nil {
+		log.Fatal(err)
+	}
+	stringRex := regexp.MustCompile(`[[:graph:]]{3,}`)
+	allStrings = stringRex.FindAll(binaryData, -1)
+
+	currentUser, err = user.Current()
+	if err != nil {
+		currentUser = nil
+	}
+
+	os.Exit(m.Run())
+}
+
+// TestStandardPath checks that source paths from the standard library
+// are trimmed. We just check one known source file.
+func TestStandardPath(t *testing.T) {
+	want := []byte("GOROOT/src/fmt/format.go")
+	for _, s := range allStrings {
+		if bytes.HasSuffix(s, []byte("fmt/format.go")) && !bytes.Equal(s, want) {
+			t.Fatalf("got %q; want %q", s, want)
+		}
+	}
+}
+
+// TestUserNameAndHome checks the user name and home directory do not
+// appear in strings from the binary.
+func TestUserNameAndHome(t *testing.T) {
+	if currentUser == nil || len(currentUser.Username) < 4 {
+		t.Skip()
+	}
+	for _, s := range allStrings {
+		if currentUser.Username != "" && bytes.Contains(s, []byte(currentUser.Username)) {
+			t.Errorf("binary contains username %q in string %q", currentUser.Username, s)
+			continue
+		}
+		if currentUser.HomeDir != "" && bytes.Contains(s, []byte(currentUser.HomeDir)) {
+			t.Errorf("binary contains home dir %q in string %q", currentUser.HomeDir, s)
+		}
+	}
+}