feat: return better error if file size is too big to upload (#7775)

* feat: return better error if file size is too big to upload
* Use a limit writer to capture actual tar size

provisionersdk/archive.go

@@ -8,6 +8,8 @@ import (
 	"strings"
 
 	"golang.org/x/xerrors"
+
+	"github.com/coder/coder/coderd/util/xio"
 )
 
 const (
@@ -32,8 +34,9 @@ func dirHasExt(dir string, ext string) (bool, error) {
 
 // Tar archives a Terraform directory.
 func Tar(w io.Writer, directory string, limit int64) error {
+	// The total bytes written must be under the limit, so use -1
+	w = xio.NewLimitWriter(w, limit-1)
 	tarWriter := tar.NewWriter(w)
-	totalSize := int64(0)
 
 	const tfExt = ".tf"
 	hasTf, err := dirHasExt(directory, tfExt)
@@ -95,22 +98,26 @@ func Tar(w io.Writer, directory string, limit int64) error {
 		if !fileInfo.Mode().IsRegular() {
 			return nil
 		}
+
 		data, err := os.Open(file)
 		if err != nil {
 			return err
 		}
 		defer data.Close()
-		wrote, err := io.Copy(tarWriter, data)
+		_, err = io.Copy(tarWriter, data)
 		if err != nil {
+			if xerrors.Is(err, xio.ErrLimitReached) {
+				return xerrors.Errorf("Archive too big. Must be <= %d bytes", limit)
+			}
 			return err
 		}
-		totalSize += wrote
-		if limit != 0 && totalSize >= limit {
-			return xerrors.Errorf("Archive too big. Must be <= %d bytes", limit)
-		}
+
 		return data.Close()
 	})
 	if err != nil {
+		if xerrors.Is(err, xio.ErrLimitReached) {
+			return xerrors.Errorf("Archive too big. Must be <= %d bytes", limit)
+		}
 		return err
 	}
 	err = tarWriter.Flush()

provisionersdk/archive_test.go

@@ -15,6 +15,32 @@ import (
 
 func TestTar(t *testing.T) {
 	t.Parallel()
+	t.Run("HeaderBreakLimit", func(t *testing.T) {
+		t.Parallel()
+		dir := t.TempDir()
+		file, err := os.CreateTemp(dir, "*.tf")
+		require.NoError(t, err)
+		_ = file.Close()
+		// A header is 512 bytes
+		err = provisionersdk.Tar(io.Discard, dir, 100)
+		require.Error(t, err)
+	})
+	t.Run("HeaderAndContent", func(t *testing.T) {
+		t.Parallel()
+		dir := t.TempDir()
+		file, err := os.CreateTemp(dir, "*.tf")
+		require.NoError(t, err)
+		_, _ = file.Write(make([]byte, 100))
+		_ = file.Close()
+		// Pay + header is 1024 bytes (padding)
+		err = provisionersdk.Tar(io.Discard, dir, 1025)
+		require.NoError(t, err)
+
+		// Limit is 1 byte too small (n == limit is a failure, must be under)
+		err = provisionersdk.Tar(io.Discard, dir, 1024)
+		require.Error(t, err)
+	})
+
 	t.Run("NoTF", func(t *testing.T) {
 		t.Parallel()
 		dir := t.TempDir()
@@ -97,7 +123,8 @@ func TestTar(t *testing.T) {
 			}
 		}
 		archive := new(bytes.Buffer)
-		err := provisionersdk.Tar(archive, dir, 1024)
+		// Headers are chonky so raise the limit to something reasonable
+		err := provisionersdk.Tar(archive, dir, 1024<<2)
 		require.NoError(t, err)
 		dir = t.TempDir()
 		err = provisionersdk.Untar(dir, archive)