11:45 a.m.
On 07/11/22 15:05, Richard W.M. Jones wrote:
On Mon, Jul 11, 2022 at 09:01:57AM +0200, Laszlo Ersek wrote:
> - "KexAlgorithms": the Fedora 35 ssh binary, using the DEFAULT
> crypto-policy, cannot log in to RHEL5 sshd without relaxing
> "KexAlgorithms". The server offers three algorithms:
> "diffie-hellman-group-exchange-sha1",
"diffie-hellman-group14-sha1",
> "diffie-hellman-group1-sha1"; and according to RFC 9142,
> "diffie-hellman-group14-sha1" is the least deprecated from those. (The
> RFC marks it as MAY be implemented, and marks the other two as SHOULD
> NOT be implemented.) Recommend "diffie-hellman-group14-sha1".
>
> - "MACs": the Fedora 35 ssh binary, using the FUTURE crypto-policy, cannot
> log in to RHEL5 sshd without relaxing "MACs". The server offers
> "hmac-md5", "hmac-sha1", "hmac-ripemd160",
"hmac-ripemd160(a)openssh.com",
> "hmac-sha1-96", "hmac-md5-96". After eliminating the MD5-based
algos
> (MD5 is considered completely broken), and the one based on truncated
> SHA1, we're left with "hmac-sha1", "hmac-ripemd160", and
> "hmac-ripemd160(a)openssh.com". RIPEMD-160 is generally trusted, but it is
> compiled out of the Fedora 35 "ssh" client binary. Therefore only
> "hmac-sha1" remains.
>
> - "HostKeyAlgorithms", "PubkeyAcceptedAlgorithms": these options
control
> the usage of public key algorithms, for authenticating the server to the
> client, and vice versa, respectively. RHEL5 sshd only supports "ssh-rsa"
> and "ssh-dss", and from those, "ssh-rsa" is more commonly used
(for
> example, "ssh-keygen" defaults to creating "ssh-rsa" keys).
Recommend
> "ssh-rsa".
>
> - "PubkeyAcceptedKeyTypes": this is the old ("legacy") name for
> "PubkeyAcceptedAlgorithms". As of this writing, the latest upstream
> release of libssh (also packaged in Fedora 35 -- libssh-0.9.6-1.fc35)
> does not recognize the new "PubkeyAcceptedAlgorithms" option name, only
> the original "PubkeyAcceptedKeyTypes". openssh-8.7p1-3.fc35 recognizes
> both option variants. Include "PubkeyAcceptedKeyTypes" in the
> recommendation along with "PubkeyAcceptedAlgorithms", for backward and
> forward compatbility.
>
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2062360
> Signed-off-by: Laszlo Ersek <lersek(a)redhat.com>
> ---
> docs/virt-v2v-input-xen.pod | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/docs/virt-v2v-input-xen.pod b/docs/virt-v2v-input-xen.pod
> index afc4a019f13d..789853b4d194 100644
> --- a/docs/virt-v2v-input-xen.pod
> +++ b/docs/virt-v2v-input-xen.pod
> @@ -37,12 +37,22 @@ option is incomplete. Some operations remain that still require
the
> user to enter the password manually. Therefore ssh-agent is recommended
> over the I<-ip> option. See L<https://bugzilla.redhat.com/1854275>;.
>
> -With some modern ssh implementations, legacy crypto policies required
> -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:
> +With some modern ssh implementations, legacy crypto algorithms required
> +to interoperate with RHEL 5 sshd are disabled. To enable them, you may
> +need to add the following C<Host> stanza to your F<~/.ssh/config>:
>
> - # update-crypto-policies --set LEGACY
> + Host xen.example.com
> + KexAlgorithms +diffie-hellman-group14-sha1
> + MACs +hmac-sha1
> + HostKeyAlgorithms +ssh-rsa
> + PubkeyAcceptedKeyTypes +ssh-rsa
> + PubkeyAcceptedAlgorithms +ssh-rsa
> +
> +(C<PubkeyAcceptedKeyTypes> and C<PubkeyAcceptedAlgorithms> have
> +identical meaning; the former is the old option name, the latter is the
> +new one. Virt-v2v uses both C<libssh> and C<ssh> when converting a
guest
> +from Xen, and on some operating systems, C<libssh> and C<ssh> may not
> +both accept the same option variant.)
>
> =head2 Test libvirt connection to remote Xen host
For the series:
Reviewed-by: Richard W.M. Jones <rjones(a)redhat.com>
Commit range 4368b94ee172..af4a0454cdd2.
Thanks!
Laszlo