server(filesystem): fix archiver path matching

Closes https://github.com/pterodactyl/panel/issues/4630

server/filesystem/archive.go

@@ -3,6 +3,7 @@ package filesystem
 import (
 	"archive/tar"
 	"context"
+	"fmt"
 	"io"
 	"io/fs"
 	"os"
@@ -66,6 +67,8 @@ type Archive struct {
 
 	// Files specifies the files to archive, this takes priority over the Ignore option, if
 	// unspecified, all files in the BasePath will be archived unless Ignore is set.
+	//
+	// All items in Files must be absolute within BasePath.
 	Files []string
 
 	// Progress wraps the writer of the archive to pass through the progress tracker.
@@ -97,6 +100,14 @@ func (a *Archive) Create(ctx context.Context, dst string) error {
 
 // Stream .
 func (a *Archive) Stream(ctx context.Context, w io.Writer) error {
+	for _, f := range a.Files {
+		if strings.HasPrefix(f, a.BasePath) {
+			continue
+		}
+
+		return fmt.Errorf("archive: all entries in Files must be absolute and within BasePath: %s\n", f)
+	}
+
 	// Choose which compression level to use based on the compression_level configuration option
 	var compressionLevel int
 	switch config.Get().System.Backups.CompressionLevel {
@@ -190,9 +201,11 @@ func (a *Archive) callback(tw *TarProgress, opts ...func(path string, relative s
 func (a *Archive) withFilesCallback(tw *TarProgress) func(path string, de *godirwalk.Dirent) error {
 	return a.callback(tw, func(p string, rp string) error {
 		for _, f := range a.Files {
-			// If the given doesn't match, or doesn't have the same prefix continue
-			// to the next item in the loop.
-			if p != f && !strings.HasPrefix(strings.TrimSuffix(p, "/")+"/", f) {
+			// Allow exact file matches, otherwise check if file is within a parent directory.
+			//
+			// The slashes are added in the prefix checks to prevent partial name matches from being
+			// included in the archive.
+			if f != p && !strings.HasPrefix(strings.TrimSuffix(p, "/")+"/", strings.TrimSuffix(f, "/")+"/") {
 				continue
 			}
 

server/filesystem/archive_test.go

@@ -0,0 +1,125 @@
+package filesystem
+
+import (
+	"context"
+	iofs "io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	. "github.com/franela/goblin"
+	"github.com/mholt/archiver/v4"
+)
+
+func TestArchive_Stream(t *testing.T) {
+	g := Goblin(t)
+	fs, rfs := NewFs()
+
+	g.Describe("Archive", func() {
+		g.AfterEach(func() {
+			// Reset the filesystem after each run.
+			rfs.reset()
+		})
+
+		g.It("throws an error when passed invalid file paths", func() {
+			a := &Archive{
+				BasePath: fs.Path(),
+				Files: []string{
+					// To use the archiver properly, this needs to be filepath.Join(BasePath, "yeet")
+					// However, this test tests that we actually validate that behavior.
+					"yeet",
+				},
+			}
+
+			g.Assert(a.Create(context.Background(), "")).IsNotNil()
+		})
+
+		g.It("creates archive with intended files", func() {
+			g.Assert(fs.CreateDirectory("test", "/")).IsNil()
+			g.Assert(fs.CreateDirectory("test2", "/")).IsNil()
+
+			err := fs.Writefile("test/file.txt", strings.NewReader("hello, world!\n"))
+			g.Assert(err).IsNil()
+
+			err = fs.Writefile("test2/file.txt", strings.NewReader("hello, world!\n"))
+			g.Assert(err).IsNil()
+
+			err = fs.Writefile("test_file.txt", strings.NewReader("hello, world!\n"))
+			g.Assert(err).IsNil()
+
+			err = fs.Writefile("test_file.txt.old", strings.NewReader("hello, world!\n"))
+			g.Assert(err).IsNil()
+
+			a := &Archive{
+				BasePath: fs.Path(),
+				Files: []string{
+					filepath.Join(fs.Path(), "test"),
+					filepath.Join(fs.Path(), "test_file.txt"),
+				},
+			}
+
+			// Create the archive
+			archivePath := filepath.Join(rfs.root, "archive.tar.gz")
+			g.Assert(a.Create(context.Background(), archivePath)).IsNil()
+
+			// Ensure the archive exists.
+			_, err = os.Stat(archivePath)
+			g.Assert(err).IsNil()
+
+			// Open the archive.
+			genericFs, err := archiver.FileSystem(archivePath)
+			g.Assert(err).IsNil()
+
+			// Assert that we are opening an archive.
+			afs, ok := genericFs.(archiver.ArchiveFS)
+			g.Assert(ok).IsTrue()
+
+			// Get the names of the files recursively from the archive.
+			files, err := getFiles(afs, ".")
+			g.Assert(err).IsNil()
+
+			// Ensure the files in the archive match what we are expecting.
+			g.Assert(files).Equal([]string{
+				"test_file.txt",
+				"test/file.txt",
+			})
+		})
+	})
+}
+
+func getFiles(f iofs.ReadDirFS, name string) ([]string, error) {
+	var v []string
+
+	entries, err := f.ReadDir(name)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, e := range entries {
+		entryName := e.Name()
+		if name != "." {
+			entryName = filepath.Join(name, entryName)
+		}
+
+		if e.IsDir() {
+			files, err := getFiles(f, entryName)
+			if err != nil {
+				return nil, err
+			}
+
+			if files == nil {
+				return nil, nil
+			}
+
+			for _, f := range files {
+				v = append(v, f)
+			}
+			continue
+		}
+
+		v = append(v, entryName)
+	}
+
+	return v, nil
+}