lib/fips140: add directory and test

This directory will hold the fips140 snapshots.
Add a README, helpful Makefile, and a test that
the checksums are correct (once we have zip files).

Change-Id: I735540ad1ce7da9a24c3a0b57b054c8340708da1
Reviewed-on: https://go-review.googlesource.com/c/go/+/629955
Reviewed-by: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Matloob <matloob@golang.org>

lib/fips140/Makefile

@@ -0,0 +1,46 @@
+# Copyright 2024 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+# Rules for building and testing new FIPS snapshots.
+# For example:
+#
+#	make v1.2.3.zip
+#	make v1.2.3.test
+#
+# and then if changes are needed, check them into master
+# and run 'make v1.2.3.rm' and repeat.
+#
+# Note that once published a snapshot zip file should never
+# be modified. We record the sha256 hashes of the zip files
+# in fips140.sum, and the cmd/go/internal/fips test checks
+# that the zips match.
+#
+# When the zip file is finalized, run 'make updatesum' to update
+# fips140.sum.
+
+default:
+	@echo nothing to make
+
+# make v1.2.3.zip builds a v1.2.3.zip file
+# from the current origin/master.
+# copy and edit the 'go run' command by hand to use a different branch.
+v%.zip:
+	git fetch origin master
+	go run ../../src/cmd/go/internal/fips/mkzip.go -b master v$*
+
+# normally mkzip refuses to overwrite an existing zip file.
+# make v1.2.3.rm removes the zip file and and unpacked
+# copy from the module cache.
+v%.rm:
+	rm -f v$*.zip
+	chmod -R u+w $$(go env GOMODCACHE)/golang.org/fips140@v$* 2>/dev/null || true
+	rm -rf $$(go env GOMODCACHE)/golang.org/fips140@v$*
+
+# make v1.2.3.test runs the crypto tests using that snapshot.
+v%.test:
+	GOFIPS140=v$* go test -short crypto...
+
+# make updatesum updates the fips140.sum file.
+updatesum:
+	go test cmd/go/internal/fips -update

lib/fips140/README.md

@@ -0,0 +1,9 @@
+This directory holds snapshots of the crypto/internal/fips tree
+that are being validated and certified for FIPS-140 use.
+The file x.txt (for example, inprocess.txt, certified.txt)
+defines the meaning of the FIPS version alias x, listing
+the exact version to use.
+
+The zip files are created by cmd/go/internal/fips/mkzip.go.
+The fips140.sum file lists checksums for the zip files.
+See the Makefile for recipes.

lib/fips140/fips140.sum

@@ -0,0 +1,11 @@
+# SHA256 checksums of snapshot zip files in this directory.
+# These checksums are included in the FIPS security policy
+# (validation instructions sent to the lab) and MUST NOT CHANGE.
+# That is, the zip files themselves must not change.
+#
+# It is okay to add new zip files to the list, and it is okay to
+# remove zip files from the list when they are removed from
+# this directory. To update this file:
+#
+#	go test cmd/go/internal/fips -update
+#

src/cmd/go/internal/fips/fips_test.go

@@ -0,0 +1,102 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fips
+
+import (
+	"crypto/sha256"
+	"flag"
+	"fmt"
+	"internal/testenv"
+	"maps"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+	"testing"
+)
+
+var update = flag.Bool("update", false, "update GOROOT/lib/fips140/fips140.sum")
+
+func TestSums(t *testing.T) {
+	lib := filepath.Join(testenv.GOROOT(t), "lib/fips140")
+	file := filepath.Join(lib, "fips140.sum")
+	sums, err := os.ReadFile(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	lines := strings.SplitAfter(string(sums), "\n")
+
+	zips, err := filepath.Glob(filepath.Join(lib, "*.zip"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	format := func(name string, sum [32]byte) string {
+		return fmt.Sprintf("%s %x\n", name, sum[:])
+	}
+
+	want := make(map[string]string)
+	for _, zip := range zips {
+		data, err := os.ReadFile(zip)
+		if err != nil {
+			t.Fatal(err)
+		}
+		name := filepath.Base(zip)
+		want[name] = format(name, sha256.Sum256(data))
+	}
+
+	// Process diff, deleting or correcting stale lines.
+	var diff []string
+	have := make(map[string]bool)
+	for i, line := range lines {
+		if line == "" {
+			continue
+		}
+		if strings.HasPrefix(line, "#") || line == "\n" {
+			// comment, preserve
+			diff = append(diff, " "+line)
+			continue
+		}
+		name, _, _ := strings.Cut(line, " ")
+		if want[name] == "" {
+			lines[i] = ""
+			diff = append(diff, "-"+line)
+			continue
+		}
+		have[name] = true
+		fixed := want[name]
+		delete(want, name)
+		if line == fixed {
+			diff = append(diff, " "+line)
+		} else {
+			// zip hashes should never change once listed
+			t.Errorf("policy violation: zip file hash is changing:\n-%s+%s", line, fixed)
+			lines[i] = fixed
+			diff = append(diff, "-"+line, "+"+fixed)
+		}
+	}
+
+	// Add missing lines.
+	// Sort keys to avoid non-determinism, but overall file is not sorted.
+	// It will end up time-ordered instead.
+	for _, name := range slices.Sorted(maps.Keys(want)) {
+		line := want[name]
+		lines = append(lines, line)
+		diff = append(diff, "+"+line)
+	}
+
+	// Show diffs or update file.
+	fixed := strings.Join(lines, "")
+	if fixed != string(sums) {
+		if *update && !t.Failed() {
+			t.Logf("updating GOROOT/lib/fips140/fips140.sum:\n%s", strings.Join(diff, ""))
+			if err := os.WriteFile(file, []byte(fixed), 0666); err != nil {
+				t.Fatal(err)
+			}
+			return
+		}
+		t.Errorf("GOROOT/lib/fips140/fips140.sum out of date. changes needed:\n%s", strings.Join(diff, ""))
+	}
+}