• Joe Tsai's avatar
    archive/tar: fallback to pre-Go1.8 behavior on certain GNU files · 01e45c73
    Joe Tsai authored
    Prior to Go1.8, the Writer had a bug where it would output
    an invalid tar file in certain rare situations because the logic
    incorrectly believed that the old GNU format had a prefix field.
    This is wrong and leads to an output file that mangles the
    atime and ctime fields, which are often left unused.
    
    In order to continue reading tar files created by former, buggy
    versions of Go, we skeptically parse the atime and ctime fields.
    If we are unable to parse them and the prefix field looks like
    an ASCII string, then we fallback on the pre-Go1.8 behavior
    of treating these fields as the USTAR prefix field.
    
    Note that this will not use the fallback logic for all possible
    files generated by a pre-Go1.8 toolchain. If the generated file
    happened to have a prefix field that parses as valid
    atime and ctime fields (e.g., when they are valid octal strings),
    then it is impossible to distinguish between an valid GNU file
    and an invalid pre-Go1.8 file.
    
    Fixes #21005
    
    Change-Id: Iebf5c67c08e0e46da6ee41a2e8b339f84030dd90
    Reviewed-on: https://go-review.googlesource.com/53635
    Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
    Reviewed-by: 's avatarIan Lance Taylor <iant@golang.org>
    01e45c73
reader.go 25.9 KB