Re: svn commit: r301010 - in head/sys: cddl/contrib/opensolaris/common/zfs cddl/contrib/opensolaris/uts/common cddl/contrib/opensolaris/uts/common/fs/zfs cddl/contrib/opensolaris/uts/common/fs/zfs/sys

[Matthew Ahrens]

On Tue, May 31, 2016 at 7:44 AM, Allan Jude  wrote:

> On 2016-05-31 07:41, Ivan Klymenko wrote:
> > On Tue, 31 May 2016 04:12:14 + (UTC)
> > Allan Jude  wrote:
> >
> >> Author: allanjude
> >> Date: Tue May 31 04:12:14 2016
> >> New Revision: 301010
> >> URL: https://svnweb.freebsd.org/changeset/base/301010
> >>
> >> Log:
> >>   Connect the SHA-512t256 and Skein hashing algorithms to ZFS
> >>
> >>   Support for the new hashing algorithms in ZFS was introduced in
> >> r289422 However it was disconnected because FreeBSD lacked
> >> implementations of SHA-512 (truncated to 256 bits), and Skein.
> >>
> >>   These implementations were introduced in r300921 and r300966
> >> respectively
> >>   This commit connects them to ZFS and enabled these new checksum
> >> algorithms
> >>   This new algorithms are not supported by the boot blocks, so do not
> >> use them on your root dataset if you boot from ZFS.
> >>
> >
> > Hello.
> >
> > Tell me please, who is now the fastest of these algorithms?
> >
> > What remains of the available algorithms checksum algorithm by default?
> >
> > Thanks.
> >
>
> None of the old checksums were removed
> This means the available checksums are (from fastest to slowest):
>
> off (bad idea)
> fletcher2 (not recommended, weak)
> fletcher4 (default)
> edon-r (not implemented, possibly insecure)
>

To be clear, all of the above are (possibly) insecure.  Edon-R and
fletcher4 are not used for dedup, so they doesn't need to be secure.
Edon-R can be used for nop-write, which also doesn't need to be secure, it
just needs to prevent accidental hash collisions (intentional ones are
fine, because they only mess up the block being written, and if you can
write then by definition you can arbitrarily modify the block being
written).

That said, even intentional collisions with Edon-R would be nontrivial,
because of the secret salt.  This is documented in the zpool-features
manpage:

   edonr

   GUID   org.illumos:edonr
   READ-ONLY COMPATIBLE   no
   DEPENDENCIES   none

   This feature enables the use of the Edon-R hash algorithm for
   checksum, including for nopwrite (if compression is also enabled,
   an overwrite of a block whose checksum matches the data being
   written will be ignored).  In an abundance of caution, Edon-R can
   not be used with dedup (without verification).

   Edon-R is a very high-performance hash algorithm that was part of
   the NIST SHA-3 competition. It provides extremely high hash
   performance (over 350% faster than SHA-256), but was not selected
   because of its unsuitability as a general purpose secure hash
   algorithm.  This implementation utilizes the new salted
   checksumming functionality in ZFS, which means that the checksum
is
   pre-seeded with a secret 256-bit random key (stored on the pool)
   before being fed the data block to be checksummed. Thus the
   produced checksums are unique to a given pool, blocking hash
   collision attacks on systems with dedup.

--matt


> skein
> sha512
> sha256
>
> --
> Allan Jude
>
>
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Re: svn commit: r301010 - in head/sys: cddl/contrib/opensolaris/common/zfs cddl/contrib/opensolaris/uts/common cddl/contrib/opensolaris/uts/common/fs/zfs cddl/contrib/opensolaris/uts/common/fs/zfs/sys

[Allan Jude]

On 2016-05-31 07:41, Ivan Klymenko wrote:
> On Tue, 31 May 2016 04:12:14 + (UTC)
> Allan Jude  wrote:
> 
>> Author: allanjude
>> Date: Tue May 31 04:12:14 2016
>> New Revision: 301010
>> URL: https://svnweb.freebsd.org/changeset/base/301010
>>
>> Log:
>>   Connect the SHA-512t256 and Skein hashing algorithms to ZFS
>>   
>>   Support for the new hashing algorithms in ZFS was introduced in
>> r289422 However it was disconnected because FreeBSD lacked
>> implementations of SHA-512 (truncated to 256 bits), and Skein.
>>   
>>   These implementations were introduced in r300921 and r300966
>> respectively 
>>   This commit connects them to ZFS and enabled these new checksum
>> algorithms 
>>   This new algorithms are not supported by the boot blocks, so do not
>> use them on your root dataset if you boot from ZFS.
>>   
> 
> Hello.
> 
> Tell me please, who is now the fastest of these algorithms?
> 
> What remains of the available algorithms checksum algorithm by default?
> 
> Thanks.
> 

None of the old checksums were removed
This means the available checksums are (from fastest to slowest):

off (bad idea)
fletcher2 (not recommended, weak)
fletcher4 (default)
edon-r (not implemented, possibly insecure)
skein
sha512
sha256

-- 
Allan Jude
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Re: svn commit: r301010 - in head/sys: cddl/contrib/opensolaris/common/zfs cddl/contrib/opensolaris/uts/common cddl/contrib/opensolaris/uts/common/fs/zfs cddl/contrib/opensolaris/uts/common/fs/zfs/sys

[Jan Beich]

Allan Jude  writes:

> Author: allanjude
> Date: Tue May 31 04:12:14 2016
> New Revision: 301010
> URL: https://svnweb.freebsd.org/changeset/base/301010
>
> Log:
>   Connect the SHA-512t256 and Skein hashing algorithms to ZFS
>   
>   Support for the new hashing algorithms in ZFS was introduced in r289422
>   However it was disconnected because FreeBSD lacked implementations of
>   SHA-512 (truncated to 256 bits), and Skein.
>   
>   These implementations were introduced in r300921 and r300966 respectively
>   
>   This commit connects them to ZFS and enabled these new checksum algorithms
>   
>   This new algorithms are not supported by the boot blocks, so do not use them
>   on your root dataset if you boot from ZFS.

Can you document the feature and booting caveat in zpool-features(7) manpage?
And Illumos seems to limit booting support to pools vs. datasets.

  Booting off of pools using skein is NOT supported -- any attempt to
  enable skein on a root pool will fail with an error.

https://illumos.org/man/5/zpool-features


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Re: svn commit: r301010 - in head/sys: cddl/contrib/opensolaris/common/zfs cddl/contrib/opensolaris/uts/common cddl/contrib/opensolaris/uts/common/fs/zfs cddl/contrib/opensolaris/uts/common/fs/zfs/sys

[Ivan Klymenko]

On Tue, 31 May 2016 04:12:14 + (UTC)
Allan Jude  wrote:

> Author: allanjude
> Date: Tue May 31 04:12:14 2016
> New Revision: 301010
> URL: https://svnweb.freebsd.org/changeset/base/301010
> 
> Log:
>   Connect the SHA-512t256 and Skein hashing algorithms to ZFS
>   
>   Support for the new hashing algorithms in ZFS was introduced in
> r289422 However it was disconnected because FreeBSD lacked
> implementations of SHA-512 (truncated to 256 bits), and Skein.
>   
>   These implementations were introduced in r300921 and r300966
> respectively 
>   This commit connects them to ZFS and enabled these new checksum
> algorithms 
>   This new algorithms are not supported by the boot blocks, so do not
> use them on your root dataset if you boot from ZFS.
>   

Hello.

Tell me please, who is now the fastest of these algorithms?

What remains of the available algorithms checksum algorithm by default?

Thanks.
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