From b3c88f573f4c1b269e78dd7d1dbd6de73d477694 Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Sun, 6 Oct 2019 19:34:32 +0200
Subject: contentenc: add explicit test for all-zero header

https://github.com/rfjakob/gocryptfs/issues/363
---
 internal/contentenc/file_header.go | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

(limited to 'internal')

diff --git a/internal/contentenc/file_header.go b/internal/contentenc/file_header.go
index 5f8bd63..6ce2e3b 100644
--- a/internal/contentenc/file_header.go
+++ b/internal/contentenc/file_header.go
@@ -44,21 +44,25 @@ func (h *FileHeader) Pack() []byte {
 
 // allZeroFileID is preallocated to quickly check if the data read from disk is all zero
 var allZeroFileID = make([]byte, headerIDLen)
+var allZeroHeader = make([]byte, HeaderLen)
 
 // ParseHeader - parse "buf" into fileHeader object
 func ParseHeader(buf []byte) (*FileHeader, error) {
 	if len(buf) != HeaderLen {
 		return nil, fmt.Errorf("ParseHeader: invalid length, want=%d have=%d", HeaderLen, len(buf))
 	}
+	if bytes.Equal(buf, allZeroHeader) {
+		return nil, fmt.Errorf("ParseHeader: header is all-zero. Header hexdump: %s", hex.EncodeToString(buf))
+	}
 	var h FileHeader
 	h.Version = binary.BigEndian.Uint16(buf[0:headerVersionLen])
 	if h.Version != CurrentVersion {
-		return nil, fmt.Errorf("ParseHeader: invalid version, want=%d have=%d. Hexdump: %s",
+		return nil, fmt.Errorf("ParseHeader: invalid version, want=%d have=%d. Header hexdump: %s",
 			CurrentVersion, h.Version, hex.EncodeToString(buf))
 	}
 	h.ID = buf[headerVersionLen:]
 	if bytes.Equal(h.ID, allZeroFileID) {
-		return nil, fmt.Errorf("ParseHeader: file id is all-zero. Hexdump: %s",
+		return nil, fmt.Errorf("ParseHeader: file id is all-zero. Header hexdump: %s",
 			hex.EncodeToString(buf))
 	}
 	return &h, nil
-- 
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