Re: Failing iotest 206

[Daniel P . Berrangé]

On Tue, Aug 03, 2021 at 07:17:47PM +0200, Kevin Wolf wrote:
> Am 20.07.2021 um 10:32 hat Daniel P. Berrangé geschrieben:
> > On Mon, Jul 19, 2021 at 08:12:58PM -0500, Eric Blake wrote:
> > > On Mon, Jul 19, 2021 at 10:06:01AM +0200, Thomas Huth wrote:
> > > >  Hi,
> > > > 
> > > > iotest 206 fails for me with:
> > > > 
> > > 
> > > > --- 206.out
> > > > +++ 206.out.bad
> > > > @@ -99,55 +99,19 @@
> > > > 
> > > >  {"execute": "blockdev-create", "arguments": {"job-id": "job0", 
> > > > "options":
> > > > {"driver": "qcow2", "encrypt": {"cipher-alg": "twofish-128", 
> > > > "cipher-mode":
> > > > "ctr", "format": "luks", "hash-alg": "sha1", "iter-time": 10, 
> > > > "ivgen-alg":
> > > > "plain64", "ivgen-hash-alg": "md5", "key-secret": "keysec0"}, "file":
> > > > {"driver": "file", "filename": "TEST_DIR/PID-t.qcow2"}, "size": 
> > > > 33554432}}}
> > > >  {"return": {}}
> > > > +Job failed: Unsupported cipher algorithm twofish-128 with ctr mode
> > > >  {"execute": "job-dismiss", "arguments": {"id": "job0"}}
> > > >  {"return": {}}
> > > 
> > > > 
> > > > Looks like it is missing a check for the availability of the 
> > > > corresponding
> > > > crypto stuff? Does anybody got a clue how to fix this?
> > > 
> > > What system is this on? Which crypto library versions are installed?
> > > I suspect this is related to Dan's effort to speed up crypto by
> > > favoring gnutls over nettle, where the switch in favored libraries
> > > failed to account for whether twofish-128 is supported?
> > > 
> > > https://lists.gnu.org/archive/html/qemu-devel/2021-07/msg03886.html
> > 
> > Yes, the gnutls provider doesn't support twofish. This doesn't matter
> > in real world usage because no one is seriously going to ask for twofish
> > instead of AES for luks encryption.
> > 
> > I guess that test suite was simply trying to ask for some non-default
> > values though.
> 
> Do we already have a patch somewhere that makes it use a different
> value? Or if not, which value would be most likely to work everywhere?

Ultimately there is only one cipher alg that is guaranteed 'aes',
which can be used in two keysizes 128/256, and two modes cbc/xts.

Sine aes-128 with xts is the default, if you want to exercise
a non-default codepath for LUKS support, i'd suggest aes-256
with cbc mode, and essiv IV generator.

Regards,
Daniel
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