[PATCH] rpc: Pass OPENSSL_CONF through to ssh invocations
It's no longer possible for libvirt to connect over the ssh transport
from RHEL 9 to RHEL 5. This is because SHA1 signatures have been
effectively banned in RHEL 9 at the openssl level. They are required
to check the RHEL 5 host key. Note this is a separate issue from
openssh requiring additional configuration in order to connect to
older servers.
Connecting from a RHEL 9 client to RHEL 5 server:
$ cat ~/.ssh/config
Host 192.168.0.91
KexAlgorithms +diffie-hellman-group14-sha1
MACs +hmac-sha1
HostKeyAlgorithms +ssh-rsa
PubkeyAcceptedKeyTypes +ssh-rsa
PubkeyAcceptedAlgorithms +ssh-rsa
$ virsh -c 'qemu+ssh://root@192.168.0.91/system' list
error: failed to connect to the hypervisor
error: Cannot recv data: ssh_dispatch_run_fatal: Connection to 192.168.0.91 port 22: error
in libcrypto: Connection reset by peer
"error in libcrypto: Connection reset by peer" is the characteristic
error of openssl having been modified to disable SHA1 by default.
(You will not see this on non-RHEL-derived distros.)
You could enable the legacy crypto policy which downgrades security on
the entire host, but a more fine-grained way to do this is to create
an alternate openssl configuration file that enables the "forbidden"
signatures. However this requires passing the OPENSSL_CONF
environment variable through to ssh to specify the alternate
configuration. Libvirt filters out this environment variable, but
this commit allows it through. With this commit:
$ cat /var/tmp/openssl.cnf
.include /etc/ssl/openssl.cnf
[openssl_init]
alg_section = evp_properties
[evp_properties]
rh-allow-sha1-signatures = yes
$ OPENSSL_CONF=/var/tmp/openssl.cnf ./run virsh -c
'qemu+ssh://root@192.168.0.91/system' list
root(a)192.168.0.91's password:
Id Name State
--------------------
Essentially my argument here is that OPENSSL_CONF is sufficiently
similar in nature to KRB5CCNAME, SSH* and XAUTHORITY that we should
permit it to be passed through.
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2062360
Signed-off-by: Richard W.M. Jones <rjones(a)redhat.com>
---
src/rpc/virnetsocket.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/rpc/virnetsocket.c b/src/rpc/virnetsocket.c
index 32f506d2d4..8280bda007 100644
--- a/src/rpc/virnetsocket.c
+++ b/src/rpc/virnetsocket.c
@@ -855,6 +855,7 @@ int virNetSocketNewConnectSSH(const char *nodename,
virCommandAddEnvPass(cmd, "KRB5CCNAME");
virCommandAddEnvPass(cmd, "SSH_AUTH_SOCK");
virCommandAddEnvPass(cmd, "SSH_ASKPASS");
+ virCommandAddEnvPass(cmd, "OPENSSL_CONF");
virCommandAddEnvPass(cmd, "DISPLAY");
virCommandAddEnvPass(cmd, "XAUTHORITY");
virCommandClearCaps(cmd);
--
2.31.1