Libguestfs - Jan 2020 - Re: [PATCH v2v] docs: Fix update-crypto-policies command.

The command as documented was wrong.  We need to use the --set option
to change the policy.

Fixes commit d5cbe7b4bee5dec9e28b1db03e933c97ef6d11e0.
Thanks: Xiaodai Wang
---
 docs/virt-v2v-input-xen.pod | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/virt-v2v-input-xen.pod b/docs/virt-v2v-input-xen.pod
index bafeabf62..bce0aff45 100644
--- a/docs/virt-v2v-input-xen.pod
+++ b/docs/virt-v2v-input-xen.pod
@@ -36,7 +36,7 @@ to interoperate with RHEL 5 sshd are disabled.  To enable them
you may
 need to run this command on the conversion server (ie. ssh client),
 but read L<update-crypto-policies(8)> first:
 
- # update-crypto-policies LEGACY
+ # update-crypto-policies --set LEGACY
 
 =head2 Test libvirt connection to remote Xen host
 
-- 
2.24.1

On Wed, Jan 15, 2020 at 10:57:36AM +0000, Richard W.M. Jones
wrote:
> The command as documented was wrong.  We need to use the --set option
> to change the policy.
> 
> Fixes commit d5cbe7b4bee5dec9e28b1db03e933c97ef6d11e0.
> Thanks: Xiaodai Wang
> ---
>  docs/virt-v2v-input-xen.pod | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/docs/virt-v2v-input-xen.pod b/docs/virt-v2v-input-xen.pod
> index bafeabf62..bce0aff45 100644
> --- a/docs/virt-v2v-input-xen.pod
> +++ b/docs/virt-v2v-input-xen.pod
> @@ -36,7 +36,7 @@ to interoperate with RHEL 5 sshd are disabled.  To enable
them you may
>  need to run this command on the conversion server (ie. ssh client),
>  but read L<update-crypto-policies(8)> first:
>  
> - # update-crypto-policies LEGACY
> + # update-crypto-policies --set LEGACY
Personally I would not be in favour of recommending that people
change their crypto policies host-wide, especially since the
doc is not telling them to set it back to the stronger default
policy later.

If the problem is simply the SSH server, then it ought to be
possible to address this using the "Ciphers" config option
for the SSH client, so that it doesn't weaken crypto for the
entire host.

Regards,
Daniel
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On Wed, Jan 15, 2020 at 11:03:24AM +0000, Daniel P. Berrangé
wrote:
> On Wed, Jan 15, 2020 at 10:57:36AM +0000, Richard W.M. Jones wrote:
> > The command as documented was wrong.  We need to use the --set option
> > to change the policy.
> > 
> > Fixes commit d5cbe7b4bee5dec9e28b1db03e933c97ef6d11e0.
> > Thanks: Xiaodai Wang
> > ---
> >  docs/virt-v2v-input-xen.pod | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/docs/virt-v2v-input-xen.pod b/docs/virt-v2v-input-xen.pod
> > index bafeabf62..bce0aff45 100644
> > --- a/docs/virt-v2v-input-xen.pod
> > +++ b/docs/virt-v2v-input-xen.pod
> > @@ -36,7 +36,7 @@ to interoperate with RHEL 5 sshd are disabled.  To
enable them you may
> >  need to run this command on the conversion server (ie. ssh client),
> >  but read L<update-crypto-policies(8)> first:
> >  
> > - # update-crypto-policies LEGACY
> > + # update-crypto-policies --set LEGACY
> 
> Personally I would not be in favour of recommending that people
> change their crypto policies host-wide, especially since the
> doc is not telling them to set it back to the stronger default
> policy later.
> 
> If the problem is simply the SSH server, then it ought to be
> possible to address this using the "Ciphers" config option
> for the SSH client, so that it doesn't weaken crypto for the
> entire host.
That's the "but read the <manual> first" part of the
documentation.

Anyway I looked at how easy this might be to implement.  The first
complication is that we're using two different ways to contact the
RHEL 5 Xen server, first making a libvirt connection to xen+ssh, and
then using nbdkit-ssh-plugin.

Libvirt is using the ssh binary, but with no control over the -c /
Ciphers option.  However /usr/bin/ssh will honour crypto-policies.

nbdkit is using libssh, so again it's not settable directly but it
will honour crypto-policies.

It seems as if it's possible to set crypto-policies only for SSH
protocol connections, but the documentation for this is obscure to say
the least.  Since we're using external binaries to do the work it
doesn't seem like we can do this only for virt-v2v.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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