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https://issues.apache.org/jira/browse/COMPRESS-407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16060227#comment-16060227
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Simon Spero commented on COMPRESS-407:
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It is definitely an error to attempt to create a PAX or USTAR format file a
record size that is not 512 bytes. Any attempt to use a PAX or USTAR feature
with a record size not equal to 512 bytes will have to be modified to throw an
exception.
[The tar format documentation in libarchive|
https://github.com/libarchive/libarchive/blob/master/libarchive/tar.5] shows
that this goes all the way back to V7.
{panel:title=tar (5) }
*General Format*
A tar archive consists of a series of 512-byte records. Each file system
object requires a header record which stores basic metadata (pathname, owner,
permissions, etc.) and zero or more records containing any file data. The end
of the archive is indicated by two records consisting entirely of zero bytes.
For compatibility with tape drives that use fixed block sizes, programs
that read or write tar files always read or write a fixed number of records
with each I/O operation. These “blocks” are always a multiple of the record
size. The maximum block size supported by early implementations was 10240
bytes or 20 records. This is still the default for most implementations
although block sizes of 1MiB (2048 records) or larger are commonly used with
modern high-speed tape drives. (Note: the terms “block” and “record” here are
not entirely standard; this document follows the convention established by John
Gilmore in documenting pdtar.)
{panel}
If alternative record sizes are to be permitted then these will have to be 512
bytes or greater in size. If such uses are permitted then there needs to a
warning logged. Which means there has to be logging added.
I will add a second pull request on top of this one that adds a logging
framework, reduces the errors to a warning, and removes the tests.
As an alternative, I will add a third pull request that uses a system property
to enable invalid tar record sizes.
I would still advise applying the PR as submitted and rejecting either of the
above listed alternatives.
> Validate Block and Record Sizes
> -------------------------------
>
> Key: COMPRESS-407
> URL: https://issues.apache.org/jira/browse/COMPRESS-407
> Project: Commons Compress
> Issue Type: Sub-task
> Components: Archivers
> Reporter: Simon Spero
>
> Reject record sizes not equal to 512 bytes; require block sizes to be
> multiples of 512 bytes.
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