import: make sure gnu tar complains on tar files with trailing garbage

System Internals / systemd - Lennart Poettering [] - 2 September 2020 06:59 UTC

By default GNU tar will only read the first archive if multiple archives are concatenated and ignore the rest. If an archive contains trailing garbage this will hence not be recognized by tar as error, it simply stops reading when the first archive is done (which might escalate to SIGPIPE when invoked via a pipe).

Let's add --ignore-zeros to the tar command line when extracting. This means:

1) if a tar archive was concatenated (i.e. generated with tar -A) we'll process it correctly.

2) if a tar archive contains trailing garbage tar will now generate an error message about it, instead of just throwing EPIPE, which makes things easier to debug as broken files are not silently processed.

I think it's OK for gnu tar to ignore trailing garbage when dealing with classic tapes drives, i.e. mediums that do not have a size limit built-in. However, this is not what we are dealing with: we are dealing with OS images here, that hopefully someone generated with a clean build system, that were signed and validated and hence should not contain trailing garbage. Hence it's better to refuse and complain thant to silently eat up like for classic tape drives.

Fixes: #16605

e4ec78206c import: make sure gnu tar complains on tar files with trailing garbage
src/import/import-common.c | 1 +
1 file changed, 1 insertion(+)


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