[COMPRESS-65] TarArchiveInputStream.matches() only works for tar archives whose first file is "test1.xml"

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.0
• Assignee: Unassigned
• Reporter: Sebb
• Created: 29/Mar/09 17:46
• Updated: 08/Mar/13 05:09
• Resolved: 02/Apr/09 23:36

Description

The tar header format does not have a "magic" number at the start, so in general it is impossible to tell if an input file is a tar file without reading a lot more data.

The current match() implementation assumes the first 8 bytes contain "test1.xml", which is obviously a hack for testing purposes.

If more bytes are read from the input, it might be possible to implement a working match() method:

The file must be at least 512 bytes long.

The following offsets have contents that could be checked:

Offset len
148 8 Checksum for header block
156 1 Link indicator (file type) - '0'-'6' or null

Other possible checks are:

• numeric fields must be octal
• filename fields must end in trailing nulls (but can a filename contain a null?)