:fix: toctou for files

- Fixes #440

Signed-off-by: naveensrinivasan <172697+naveensrinivasan@users.noreply.github.com>

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/AlecAivazis/survey/v2 v2.3.7
 	github.com/alecthomas/jsonschema v0.0.0-20220216202328-9eeeec9d044b
 	github.com/defenseunicorns/zarf v0.32.3
+	github.com/fsnotify/fsnotify v1.7.0
 	github.com/goccy/go-yaml v1.11.3
 	github.com/mholt/archiver/v3 v3.5.1
 	github.com/mholt/archiver/v4 v4.0.0-alpha.8
@@ -197,7 +198,6 @@ require (
 	github.com/fluxcd/pkg/apis/kustomize v1.3.0 // indirect
 	github.com/fluxcd/pkg/apis/meta v1.3.0 // indirect
 	github.com/fluxcd/source-controller/api v1.2.4 // indirect
-	github.com/fsnotify/fsnotify v1.7.0 // indirect
 	github.com/fvbommel/sortorder v1.1.0 // indirect
 	github.com/gabriel-vasile/mimetype v1.4.3 // indirect
 	github.com/gdamore/encoding v1.0.0 // indirect

src/pkg/bundle/tarball.go

@@ -121,8 +121,11 @@ func (tp *tarballBundleProvider) getBundleManifest() error {
 	if err := av3.Extract(tp.src, "index.json", tp.dst); err != nil {
 		return fmt.Errorf("failed to extract index.json from %s: %w", tp.src, err)
 	}
-
 	indexPath := filepath.Join(tp.dst, "index.json")
+	indexPathChecksum, err := utils.CalculateFileChecksum(indexPath)
+	if err != nil {
+		return fmt.Errorf("failed to calculate checksum for %s: %w", indexPath, err)
+	}
 
 	defer os.Remove(indexPath)
 
@@ -136,7 +139,13 @@ func (tp *tarballBundleProvider) getBundleManifest() error {
 	if err := json.Unmarshal(b, &index); err != nil {
 		return err
 	}
-
+	// The check is done after json.Unmarshal to ensure that the file wasn't tampered after written to the temp dir
+	// while reading the file
+	// Verify the calculated checksum against the expected checksum
+	isValid, err := utils.VerifyFileChecksum(indexPath, indexPathChecksum)
+	if err != nil || !isValid {
+		return fmt.Errorf("checksum verification failed for %s", indexPath)
+	}
 	// local bundles only have one manifest entry in their index.json
 	bundleManifestDesc := index.Manifests[0]
 	tp.bundleRootDesc = bundleManifestDesc
@@ -169,6 +178,11 @@ func (tp *tarballBundleProvider) getBundleManifest() error {
 	if err := json.Unmarshal(b, &manifest); err != nil {
 		return err
 	}
+	// This is to ensure that the file wasn't tampered after written to the temp dir
+	isValid, err = utils.VerifyFileChecksum(manifestPath, bundleManifestDesc.Digest.Encoded())
+	if err != nil || !isValid {
+		return fmt.Errorf("checksum verification failed for %s", manifestPath)
+	}
 
 	tp.bundleRootManifest = manifest
 	return nil

src/pkg/utils/utils.go

@@ -6,6 +6,8 @@ package utils
 
 import (
 	"context"
+	"crypto/sha256"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -120,3 +122,29 @@ func ToLocalFile(t any, filePath string) error {
 func IsRemotePkg(pkg types.Package) bool {
 	return pkg.Repository != ""
 }
+
+// CalculateFileChecksum calculates the SHA-256 checksum of a file.
+func CalculateFileChecksum(filePath string) (string, error) {
+	file, err := os.Open(filePath)
+	if err != nil {
+		return "", fmt.Errorf("error opening file: %w", err)
+	}
+	defer file.Close()
+
+	hasher := sha256.New()
+	if _, err := io.Copy(hasher, file); err != nil {
+		return "", fmt.Errorf("error calculating checksum: %w", err)
+	}
+
+	return hex.EncodeToString(hasher.Sum(nil)), nil
+}
+
+// VerifyFileChecksum compares the calculated checksum of a file against a provided checksum.
+func VerifyFileChecksum(filePath, expectedChecksum string) (bool, error) {
+	calculatedChecksum, err := CalculateFileChecksum(filePath)
+	if err != nil {
+		return false, fmt.Errorf("error calculating checksum: %w", err)
+	}
+
+	return calculatedChecksum == expectedChecksum, nil
+}

src/pkg/utils/utils_test.go

@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023-Present The UDS Authors
+
+// Package utils provides utility fns for UDS-CLI
+package utils
+
+import (
+	"os"
+	"testing"
+)
+
+func TestCalculateFileChecksum(t *testing.T) {
+	// Create a temporary file
+	tmpFile, err := os.CreateTemp("", "testfile-")
+	if err != nil {
+		t.Fatalf("Unable to create temporary file: %v", err)
+	}
+	defer os.Remove(tmpFile.Name()) // clean up
+
+	// Write some content to the file
+	content := []byte("hello world")
+	if _, err := tmpFile.Write(content); err != nil {
+		t.Fatalf("Unable to write to temporary file: %v", err)
+	}
+	tmpFile.Close()
+
+	// Expected checksum of "hello world"
+	expectedChecksum := "b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9"
+
+	checksum, err := CalculateFileChecksum(tmpFile.Name())
+	if err != nil {
+		t.Errorf("CalculateFileChecksum returned an error: %v", err)
+	}
+
+	if checksum != expectedChecksum {
+		t.Errorf("Expected checksum %s, got %s", expectedChecksum, checksum)
+	}
+}
+
+func TestVerifyFileChecksum(t *testing.T) {
+	// Create a temporary file
+	tmpFile, err := os.CreateTemp("", "testfile-")
+	if err != nil {
+		t.Fatalf("Unable to create temporary file: %v", err)
+	}
+	defer os.Remove(tmpFile.Name()) // clean up
+
+	// Write some content to the file
+	content := []byte("hello world")
+	if _, err := tmpFile.Write(content); err != nil {
+		t.Fatalf("Unable to write to temporary file: %v", err)
+	}
+	tmpFile.Close()
+
+	// Expected checksum of "hello world"
+	expectedChecksum := "b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9"
+
+	valid, err := VerifyFileChecksum(tmpFile.Name(), expectedChecksum)
+	if err != nil {
+		t.Errorf("VerifyFileChecksum returned an error: %v", err)
+	}
+
+	if !valid {
+		t.Errorf("Expected checksum verification to be true, got false")
+	}
+
+	// Test with incorrect checksum
+	invalidChecksum := "invalidchecksum"
+	valid, err = VerifyFileChecksum(tmpFile.Name(), invalidChecksum)
+	if err != nil {
+		t.Errorf("Didn't expect an error for incorrect checksum, got %v", err)
+	}
+
+	if valid {
+		t.Errorf("Expected checksum verification to be false, got true")
+	}
+}