• Joe Tsai's avatar
    archive/tar: properly handle header-only "files" in Reader · dd5e14a7
    Joe Tsai authored
    Certain special type-flags, specifically 1, 2, 3, 4, 5, 6,
    do not have a data section. Thus, regardless of what the size field
    says, we should not attempt to read any data for these special types.
    
    The relevant PAX and USTAR specification says:
    <<<
    If the typeflag field is set to specify a file to be of type 1 (a link)
    or 2 (a symbolic link), the size field shall be specified as zero.
    If the typeflag field is set to specify a file of type 5 (directory),
    the size field shall be interpreted as described under the definition
    of that record type. No data logical records are stored for types 1, 2, or 5.
    If the typeflag field is set to 3 (character special file),
    4 (block special file), or 6 (FIFO), the meaning of the size field is
    unspecified by this volume of POSIX.1-2008, and no data logical records shall
    be stored on the medium.
    Additionally, for type 6, the size field shall be ignored when reading.
    If the typeflag field is set to any other value, the number of logical
    records written following the header shall be (size+511)/512, ignoring
    any fraction in the result of the division.
    >>>
    
    Contrary to the specification, we do not assert that the size field
    is zero for type 1 and 2 since we liberally accept non-conforming formats.
    
    Change-Id: I666b601597cb9d7a50caa081813d90ca9cfc52ed
    Reviewed-on: https://go-review.googlesource.com/16614Reviewed-by: 's avatarBrad Fitzpatrick <bradfitz@golang.org>
    Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    dd5e14a7