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Re: [PATCH 26/26] ubifs: Raise write version to 5

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On Fri, Oct 21, 2016 at 10:31:54AM -0700, Michael Halcrow wrote:
> > diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h
> > index bdc7935a5e41..e8c23c9d4f4a 100644
> > --- a/fs/ubifs/ubifs-media.h
> > +++ b/fs/ubifs/ubifs-media.h
> > @@ -46,7 +46,7 @@
> >   * UBIFS went into mainline kernel with format version 4. The older formats
> >   * were development formats.
> >   */
> > -#define UBIFS_FORMAT_VERSION 4
> > +#define UBIFS_FORMAT_VERSION 5
> 
> Alex Cope is working on a fix for file name encryption in ext4 so that
> common plaintext prefixes don't result in common ciphertext prefixes.
> Older kernels will not be able to read the new file names.

To be clear, this will be done in the context of a new encryption
mode.  In terms of how Ubifs will handle things, that's going to
depend on whether ubifs uses a single major version number or whether
they have a feature bitmask like other filesystems, including ext4.

This is better because if the user doesn't use a particular feature,
especially a feature like encryption which is optional, we don't want
the file system to reject the mount unnecessarily.  In the case of
encryption, where there may be new encryption algorithms used, or
maybe even hardware-specific encryption modes if you are using in-line
encryption where the encryption is done in hardware, the question is
whether you want to refuse the mount if you know it won't work, or
just throw an error when there is an attempt to access a directory or
file which is encrypted using an encryption algorithm which a
particular kernel version doesn't support.

We did leave some room in the ext4 superblock for an encryption format
version number, as ewll as an array of which encryption algorithsm are
in use in the superblock, but we haven't really decided which strategy
we want to use.

My current thinking is that there ought to be a warning at mount time
if there are some directories which the kernel being used won't be
able to access, but we should just fail the mount entirely, since
there might be a lot of unencrypted files that the user might want to access.

Cheers,

							- Ted

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[PATCH 00/26] UBIFS File Encryption Richard Weinberger <richard@nod.at> - 2016-10-21 14:50 +0200
  [PATCH 26/26] ubifs: Raise write version to 5 Richard Weinberger <richard@nod.at> - 2016-10-21 14:50 +0200
    Re: [PATCH 26/26] ubifs: Raise write version to 5 Michael Halcrow <mhalcrow@google.com> - 2016-10-21 19:40 +0200
      Re: [PATCH 26/26] ubifs: Raise write version to 5 Theodore Ts'o <tytso@mit.edu> - 2016-10-21 19:50 +0200
        Re: [PATCH 26/26] ubifs: Raise write version to 5 Eric Biggers <ebiggers@google.com> - 2016-10-21 20:20 +0200
          Re: [PATCH 26/26] ubifs: Raise write version to 5 Theodore Ts'o <tytso@mit.edu> - 2016-10-22 00:40 +0200
        Re: [PATCH 26/26] ubifs: Raise write version to 5 Richard Weinberger <richard@nod.at> - 2016-10-24 09:10 +0200
  [PATCH 05/26] ubifs: Define UBIFS crypto context xattr Richard Weinberger <richard@nod.at> - 2016-10-21 14:50 +0200
  [PATCH 10/26] ubifs: Enforce crypto policy in ->link and ->rename Richard Weinberger <richard@nod.at> - 2016-10-21 14:50 +0200
  [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
    Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Michael Halcrow <mhalcrow@google.com> - 2016-10-21 19:20 +0200
      Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Richard Weinberger <richard@nod.at> - 2016-10-21 19:30 +0200
        Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Michael Halcrow <mhalcrow@google.com> - 2016-10-21 20:00 +0200
          Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Richard Weinberger <richard@nod.at> - 2016-10-21 20:30 +0200
    Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Eric Biggers <ebiggers@google.com> - 2016-10-21 20:30 +0200
      Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Richard Weinberger <richard@nod.at> - 2016-10-24 09:10 +0200
  [PATCH 07/26] ubifs: Massage ubifs_listxattr() for encryption context Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 13/26] ubifs: Enforce crypto policy in mmap Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 11/26] ubifs: Preload crypto context in ->lookup() Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 21/26] ubifs: Rename tnc_read_node_nm Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 12/26] ubifs: Massage assert in ubifs_xattr_set() wrt. fscrypto Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 02/26] fscrypto: Constify struct inode pointer Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
    Re: [PATCH 02/26] fscrypto: Constify struct inode pointer Theodore Ts'o <tytso@mit.edu> - 2016-10-21 17:00 +0200
      Re: [PATCH 02/26] fscrypto: Constify struct inode pointer Richard Weinberger <richard@nod.at> - 2016-10-21 17:20 +0200
  [PATCH 22/26] ubifs: Add full hash lookup support Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 24/26] ubifs: Implement UBIFS_FLG_DOUBLE_HASH Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 25/26] ubifs: Implement UBIFS_FLG_ENCRYPTION Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
    Re: [PATCH 25/26] ubifs: Implement UBIFS_FLG_ENCRYPTION Eric Biggers <ebiggers@google.com> - 2016-10-21 20:40 +0200
      Re: [PATCH 25/26] ubifs: Implement UBIFS_FLG_ENCRYPTION Richard Weinberger <richard@nod.at> - 2016-10-24 09:00 +0200
        Re: [PATCH 25/26] ubifs: Implement UBIFS_FLG_ENCRYPTION Theodore Ts'o <tytso@mit.edu> - 2016-10-24 15:50 +0200
  [PATCH 17/26] ubifs: Make r5 hash binary string aware Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 20/26] ubifs: Add support for encrypted symlinks Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
    Re: [PATCH 20/26] ubifs: Add support for encrypted symlinks Eric Biggers <ebiggers@google.com> - 2016-10-21 20:50 +0200
      Re: [PATCH 20/26] ubifs: Add support for encrypted symlinks Richard Weinberger <richard@nod.at> - 2016-10-24 09:00 +0200
  [PATCH 23/26] ubifs: Use a random number for cookies Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 08/26] ubifs: Implement directory open operation Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 14/26] ubifs: Introduce new data node field, compr_size Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 16/26] ubifs: Relax checks in ubifs_validate_entry() Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 18/26] ubifs: Constify struct inode pointer in ubifs_crypt_is_encrypted() Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 06/26] ubifs: Add skeleton for fscrypto Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200
  Re: [PATCH 01/26] fscrypto: Add buffer operations Christoph Hellwig <hch@infradead.org> - 2016-10-21 15:10 +0200
    Re: [PATCH 01/26] fscrypto: Add buffer operations Richard Weinberger <richard@nod.at> - 2016-10-21 15:20 +0200
      Re: [PATCH 01/26] fscrypto: Add buffer operations Christoph Hellwig <hch@infradead.org> - 2016-10-21 15:30 +0200
        Re: [PATCH 01/26] fscrypto: Add buffer operations Theodore Ts'o <tytso@mit.edu> - 2016-10-21 17:20 +0200
        Re: [PATCH 01/26] fscrypto: Add buffer operations Richard Weinberger <richard@nod.at> - 2016-10-24 09:10 +0200
  [PATCH 09/26] ubifs: Implement file open operation Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200
  [PATCH 03/26] ubifs: Export ubifs_check_dir_empty() Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200
  [PATCH 04/26] ubifs: Export xattr get and set functions Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200
  [PATCH 01/26] fscrypto: Add buffer operations Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200

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