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Debian: Improve AES-GCM justification

Richard Laager 2019-12-27 17:39:42 -06:00
parent 5a6a6b0cff
commit 959d2e72cc
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Debian-Buster-Root-on-ZFS.md

@ -184,7 +184,7 @@ Choose one of the following options:
* Setting `xattr=sa` [vastly improves the performance of extended attributes](https://github.com/zfsonlinux/zfs/commit/82a37189aac955c81a59a5ecc3400475adb56355). Inside ZFS, extended attributes are used to implement POSIX ACLs. Extended attributes can also be used by user-space applications. [They are used by some desktop GUI applications.](https://en.wikipedia.org/wiki/Extended_file_attributes#Linux) [They can be used by Samba to store Windows ACLs and DOS attributes; they are required for a Samba Active Directory domain controller.](https://wiki.samba.org/index.php/Setting_up_a_Share_Using_Windows_ACLs) Note that [`xattr=sa` is Linux-specific.](http://open-zfs.org/wiki/Platform_code_differences) If you move your `xattr=sa` pool to another OpenZFS implementation besides ZFS-on-Linux, extended attributes will not be readable (though your data will be). If portability of extended attributes is important to you, omit the `-O xattr=sa` above. Even if you do not want `xattr=sa` for the whole pool, it is probably fine to use it for `/var/log`.
* Make sure to include the `-part4` portion of the drive path. If you forget that, you are specifying the whole disk, which ZFS will then re-partition, and you will lose the bootloader partition(s).
* For LUKS, the key size chosen is 512 bits. However, XTS mode requires two keys, so the LUKS key is split in half. Thus, `-s 512` means AES-256.
* ZFS native encryption uses `aes-256-ccm` by default. AES-GCM seems to be generally preferred over AES-CCM elsewhere, and is likely faster.
* ZFS native encryption uses `aes-256-ccm` by default. [AES-GCM seems to be generally preferred over AES-CCM](https://crypto.stackexchange.com/questions/6842/how-to-choose-between-aes-ccm-and-aes-gcm-for-storage-volume-encryption), [is faster now](https://github.com/zfsonlinux/zfs/pull/9749#issuecomment-569132997), and [will be even faster in the future](https://github.com/zfsonlinux/zfs/pull/9749).
* Your passphrase will likely be the weakest link. Choose wisely. See [section 5 of the cryptsetup FAQ](https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions#5-security-aspects) for guidance.
**Hints:**