[Unison-hackers] [PATCH] Unison with eCryptfs

[Benjamin C. Pierce]

Thanks for the patch.  I’ve just added it to the trunk.

   - Benjamin

On Oct 24, 2013, at 9:13 AM, Irányossy Knoblauch Artúr <ikartur at gmail.com> wrote:

> Hi Everyone!
> 
> Currently Unison will fail to sync files with more than 64 character
> long file names on systems using eCryptfs.
> 
> Unison still has some trouble creating proper temporary file names on
> certain file systems which has some limitations on the maximum allowed
> file name length: for example, eCryptfs has a limitation of 143
> characters long file names [1].
> eCryptfs is widely used: for example the default Ubuntu installer
> offers you to encrypt your home folder using eCryptfs.
> 
> If someone wants to use Unison on a system using encrypted home
> folders, Unison will highly likely fail to create temporary files.
> You can find users complaining about this in various places over the
> Internet ([2] [3] [4] [5]).
> 
> A very similar problem related to temporary file name lengths was
> fixed in the past (where Unison tried to create temporary files with
> more than 256 characters long names).
> The approach was to crop file names to 64 characters and add an MD5
> digest of the original file name to the temporary name. Using this
> method, if you have a file with 65 'a' characters Unison will fail to
> create a 148 characters long temporary file:
> 
> .unison.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaac743a45e0d2e6a95cb859adae0248435.0e30133d04f8d05f6556aa7ddc20ef74.unison.tmp
> 
> I have created a patch that fixes this problem by ensuring that all
> temporary file names will be limited to exactly 143 characters. (The
> limit can be easily and safely modified). Please review it.
> 
> Thank you very much, and have a nice day! ;-)
> 
> 
> 
> References:
> 
> [1] eCryptfs maximum file length:
> https://bugs.launchpad.net/ecryptfs/+bug/344878
> 
> [2] Unison fails to synchronize some git repositories:
> http://superuser.com/questions/629558/unison-fails-to-synchronize-some-git-repositories
> 
> [3] Has Unison error on “File name too long”:
> http://askubuntu.com/questions/232322/has-unison-error-on-file-name-too-long
> 
> [4] File name too long (ecryptfs):
> http://groups.yahoo.com/neo/groups/unison-users/conversations/messages/10756
> 
> [5] long file names:
> http://groups.yahoo.com/neo/groups/unison-users/conversations/messages/10880
> <limit_temp_file_names_to_be_compatible_with_eCryptfs.patch>_______________________________________________
> Unison-hackers mailing list
> Unison-hackers at lists.seas.upenn.edu
> http://lists.seas.upenn.edu/mailman/listinfo/unison-hackers