From f71c1288d21c863b54ea7d543ce6cad40d099675 Mon Sep 17 00:00:00 2001
From: Morgan Fainberg <code@tempusfrang.it>
Date: Tue, 3 Dec 2024 09:59:41 -0800
Subject: [PATCH] Fix PGET Expected Byte Check

Tar files have padding. Verify the end of the file is null and only
error if there is non-null or we haven't matched content-length from
origin.

This behavior is an artifact of multi-readers if the final multireader
is potentially all null bytes. New test mimics observed behavior.
---
 pkg/consumer/tar_extractor_test.go |  9 +++++----
 pkg/extract/tar.go                 | 12 ++++++++++++
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/pkg/consumer/tar_extractor_test.go b/pkg/consumer/tar_extractor_test.go
index 5f7f93d..072ecc7 100644
--- a/pkg/consumer/tar_extractor_test.go
+++ b/pkg/consumer/tar_extractor_test.go
@@ -3,6 +3,7 @@ package consumer_test
 import (
 	"archive/tar"
 	"bytes"
+	"io"
 	"os"
 	"path"
 	"testing"
@@ -110,7 +111,7 @@ func TestTarExtractor_Consume(t *testing.T) {
 	r.NoError(err)
 
 	// Create a reader from the tar file bytes
-	reader := bytes.NewReader(tarFileBytes)
+	reader := io.MultiReader(bytes.NewReader(tarFileBytes), bytes.NewReader(make([]byte, 1024)))
 
 	// Create a temporary directory to extract the tar file
 	tmpDir, err := os.MkdirTemp("", "tarExtractorTest-")
@@ -120,15 +121,15 @@ func TestTarExtractor_Consume(t *testing.T) {
 
 	tarConsumer := consumer.TarExtractor{}
 	targetDir := path.Join(tmpDir, "extract")
-	r.NoError(tarConsumer.Consume(reader, targetDir, int64(len(tarFileBytes))))
+	r.NoError(tarConsumer.Consume(reader, targetDir, int64(len(tarFileBytes)+1024)))
 
 	// Check if the extraction was successful
 	checkTarExtraction(t, targetDir)
 
 	// Test with incorrect expectedBytes
-	_, _ = reader.Seek(0, 0)
+	reader = io.MultiReader(bytes.NewReader(tarFileBytes), bytes.NewReader(make([]byte, 1024)))
 	targetDir = path.Join(tmpDir, "extract-fail")
-	r.Error(tarConsumer.Consume(reader, targetDir, int64(len(tarFileBytes)-1)))
+	r.Error(tarConsumer.Consume(reader, targetDir, int64(len(tarFileBytes)+1024-1)))
 }
 
 func checkTarExtraction(t *testing.T, targetDir string) {
diff --git a/pkg/extract/tar.go b/pkg/extract/tar.go
index ce37807..1355c0c 100644
--- a/pkg/extract/tar.go
+++ b/pkg/extract/tar.go
@@ -119,6 +119,18 @@ func TarFile(r *bufio.Reader, destDir string, overwrite bool) error {
 		return fmt.Errorf("error creating links: %w", err)
 	}
 
+	// Read the rest of the bytes from the archive and verify they are all null bytes
+	// This is for validation that the byte count is correct
+	padding, err := io.ReadAll(r)
+	if err != nil {
+		return fmt.Errorf("error reading padding bytes: %w", err)
+	}
+	for _, b := range padding {
+		if b != 0x00 {
+			return fmt.Errorf("unexpected non-null byte in padding: %x", b)
+		}
+	}
+
 	elapsed := time.Since(startTime).Seconds()
 	logger.Debug().
 		Str("extractor", "tar").