crypto/tls: streamline BoGo testing w/ -bogo-local-dir

If -bogo-local-dir is provided but doesn't exist, populate it with a git
checkout of the BoringSSL repo at the correct SHA.

Without any -bogo-local-dir argument the BoGo TLS handshake test will
fetch the BoringSSL source at a specific SHA as a Go module in a r/o
module directory. When debugging, or extending BoGo coverage, it's
preferable to have a mutable local copy of BoGo that the test will
use.

The pre-existing -bogo-local-dir flag offered a way to use a checkout of
BoGo but it relied on the user fetching the correct repo & revision
manually ahead of time. This commit extends the test to automatically
invoke `git` to clone the repo into the provided local dir at the
correct SHA based on the boringsslModVer const if the local dir doesn't
exist.

This leaves the user ready to make changes in local BoGo dir to aid
debugging, or to upstream as CRs to BoringSSL, and prevents using an
incorrect SHA by mistake.

Updates #72006

Change-Id: I0451a3d35203878cdf02a7587e138c3cd60d15a9
Reviewed-on: https://go-review.googlesource.com/c/go/+/687475
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
TryBot-Bypass: Daniel McCarney <daniel@binaryparadox.net>

src/crypto/tls/bogo_shim_test.go

@@ -11,6 +11,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"encoding/pem"
+	"errors"
 	"flag"
 	"fmt"
 	"html/template"
@@ -541,6 +542,7 @@ func orderlyShutdown(tlsConn *Conn) {
 }
 
 func TestBogoSuite(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
 	if testing.Short() {
 		t.Skip("skipping in short mode")
 	}
@@ -559,6 +561,7 @@ func TestBogoSuite(t *testing.T) {
 
 	var bogoDir string
 	if *bogoLocalDir != "" {
+		ensureLocalBogo(t, *bogoLocalDir)
 		bogoDir = *bogoLocalDir
 	} else {
 		bogoDir = cryptotest.FetchModule(t, "boringssl.googlesource.com/boringssl.git", boringsslModVer)
@@ -664,6 +667,49 @@ func TestBogoSuite(t *testing.T) {
 	}
 }
 
+// ensureLocalBogo fetches BoringSSL to localBogoDir at the correct revision
+// (from boringsslModVer) if localBogoDir doesn't already exist.
+//
+// If localBogoDir does exist, ensureLocalBogo fails the test if it isn't
+// a directory.
+func ensureLocalBogo(t *testing.T, localBogoDir string) {
+	t.Helper()
+
+	if stat, err := os.Stat(localBogoDir); err == nil {
+		if !stat.IsDir() {
+			t.Fatalf("local bogo dir (%q) exists but is not a directory", localBogoDir)
+		}
+
+		t.Logf("using local bogo checkout from %q", localBogoDir)
+		return
+	} else if !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("failed to stat local bogo dir (%q): %v", localBogoDir, err)
+	}
+
+	testenv.MustHaveExecPath(t, "git")
+
+	idx := strings.LastIndex(boringsslModVer, "-")
+	if idx == -1 || idx == len(boringsslModVer)-1 {
+		t.Fatalf("invalid boringsslModVer format: %q", boringsslModVer)
+	}
+	commitSHA := boringsslModVer[idx+1:]
+
+	t.Logf("cloning boringssl@%s to %q", commitSHA, localBogoDir)
+	cloneCmd := testenv.Command(t, "git", "clone", "--no-checkout", "https://boringssl.googlesource.com/boringssl", localBogoDir)
+	if err := cloneCmd.Run(); err != nil {
+		t.Fatalf("git clone failed: %v", err)
+	}
+
+	checkoutCmd := testenv.Command(t, "git", "checkout", commitSHA)
+	checkoutCmd.Dir = localBogoDir
+	if err := checkoutCmd.Run(); err != nil {
+		t.Fatalf("git checkout failed: %v", err)
+	}
+
+	t.Logf("using fresh local bogo checkout from %q", localBogoDir)
+	return
+}
+
 func generateReport(results bogoResults, outPath string) error {
 	data := reportData{
 		Results:   results,

src/crypto/tls/handshake_test.go

@@ -46,8 +46,9 @@ var (
 	keyFile      = flag.String("keylog", "", "destination file for KeyLogWriter")
 	bogoMode     = flag.Bool("bogo-mode", false, "Enabled bogo shim mode, ignore everything else")
 	bogoFilter   = flag.String("bogo-filter", "", "BoGo test filter")
-	bogoLocalDir = flag.String("bogo-local-dir", "", "Local BoGo to use, instead of fetching from source")
-	bogoReport   = flag.String("bogo-html-report", "", "File path to render an HTML report with BoGo results")
+	bogoLocalDir = flag.String("bogo-local-dir", "",
+		"If not-present, checkout BoGo into this dir, or otherwise use it as a pre-existing checkout")
+	bogoReport = flag.String("bogo-html-report", "", "File path to render an HTML report with BoGo results")
 )
 
 func runTestAndUpdateIfNeeded(t *testing.T, name string, run func(t *testing.T, update bool), wait bool) {