feat: tar stream extractor

stream/pipe.go

@@ -0,0 +1,42 @@
+package stream
+
+import (
+	"io"
+	"sync"
+)
+
+// Pipe creates a pipe that can be used to write to take the results of a command
+// which accepts io.Writer for the output and pipe to an io.Reader with synchronization
+// appropriately waiting for the reader to complete before continuing on the writer process
+func Pipe(readerFn func(io.Reader)) io.Writer {
+	pr, pw := io.Pipe()
+	t := &piper{
+		pipeW: pw,
+	}
+
+	t.rdrGrp.Add(1)
+
+	// Need a separate goroutine for pipe
+	go func() {
+		defer t.rdrGrp.Done()
+		readerFn(pr)
+	}()
+
+	return t
+}
+
+type piper struct {
+	rdrGrp sync.WaitGroup
+	pipeW  *io.PipeWriter
+}
+
+// Write satisfies the io.Writer interface
+func (t *piper) Write(p []byte) (n int, err error) {
+	return t.pipeW.Write(p)
+}
+
+// Close ensures the pipe is shut down correctly, wait for readerFn to complete
+func (t *piper) Close() error {
+	defer t.rdrGrp.Wait()
+	return t.pipeW.Close()
+}

stream/tar_extractor.go

@@ -0,0 +1,70 @@
+package stream
+
+import (
+	"archive/tar"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/anchore/go-make/log"
+)
+
+// TarExtractor returns a readerFn that can be passed to a WriterPipe to extract
+// the contents of a tar stream to a directory
+func TarExtractor(destDir string) func(r io.Reader) {
+	return func(r io.Reader) {
+		destDir = filepath.Clean(destDir)
+		destDirPrefix := filepath.Dir(destDir) + string(os.PathSeparator)
+		tr := tar.NewReader(r)
+		for {
+			header, err := tr.Next()
+			if err == io.EOF {
+				break // End of archive
+			}
+			if err != nil {
+				return
+			}
+
+			// Security: Prevent ZipSlip (directory traversal attacks)
+			target := filepath.Join(destDir, filepath.FromSlash(filepath.Clean(header.Name)))
+
+			if !strings.HasPrefix(target, destDirPrefix) {
+				log.Warn("refusing to write file outside of root dir: %s", target)
+				continue
+			}
+
+			switch header.Typeflag {
+			case tar.TypeDir:
+				err = os.MkdirAll(target, 0755)
+				if err != nil {
+					log.Warn("error creating directory %s: %v", target, err)
+				}
+			case tar.TypeReg:
+				// Ensure parent directory exists
+				err = os.MkdirAll(filepath.Dir(target), 0755)
+				if err != nil {
+					log.Warn("unable to create parent directory for %s: %v", target, err)
+					continue
+				}
+
+				f, err := os.OpenFile(target, os.O_CREATE|os.O_RDWR, os.FileMode(header.Mode))
+				if err != nil {
+					log.Warn("unable to create file at %s: %v", target, err)
+					continue
+				}
+
+				// Stream the file content directly to disk
+				const gb = 1024 * 1024 * 1024
+				_, err = io.CopyN(f, tr, gb)
+				if err != nil {
+					log.Warn("error writing file %s: %v", target, err)
+				}
+				err = f.Close()
+				if err != nil {
+					log.Debug("error writing file %s: %v", target, err)
+				}
+			}
+		}
+	}
+}