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From c6ea67c481a2f447951449bd9b2746cfaaf385fd Mon Sep 17 00:00:00 2001
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Message-Id: <c6ea67c481a2f447951449bd9b2746cfaaf385fd@dist-git>
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Mon, 25 Jul 2022 14:09:39 +0100
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Subject: [PATCH] rpc: Pass OPENSSL_CONF through to ssh invocations
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It's no longer possible for libvirt to connect over the ssh transport
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from RHEL 9 to RHEL 5. This is because SHA1 signatures have been
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effectively banned in RHEL 9 at the openssl level. They are required
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to check the RHEL 5 host key. Note this is a separate issue from
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openssh requiring additional configuration in order to connect to
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older servers.
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Connecting from a RHEL 9 client to RHEL 5 server:
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$ cat ~/.ssh/config
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Host 192.168.0.91
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KexAlgorithms +diffie-hellman-group14-sha1
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MACs +hmac-sha1
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HostKeyAlgorithms +ssh-rsa
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PubkeyAcceptedKeyTypes +ssh-rsa
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PubkeyAcceptedAlgorithms +ssh-rsa
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$ virsh -c 'qemu+ssh://root@192.168.0.91/system' list
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error: failed to connect to the hypervisor
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error: Cannot recv data: ssh_dispatch_run_fatal: Connection to 192.168.0.91 port 22: error in libcrypto: Connection reset by peer
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"error in libcrypto: Connection reset by peer" is the characteristic
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error of openssl having been modified to disable SHA1 by default.
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(You will not see this on non-RHEL-derived distros.)
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You could enable the legacy crypto policy which downgrades security on
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the entire host, but a more fine-grained way to do this is to create
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an alternate openssl configuration file that enables the "forbidden"
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signatures. However this requires passing the OPENSSL_CONF
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environment variable through to ssh to specify the alternate
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configuration. Libvirt filters out this environment variable, but
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this commit allows it through. With this commit:
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$ cat /var/tmp/openssl.cnf
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.include /etc/ssl/openssl.cnf
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[openssl_init]
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alg_section = evp_properties
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[evp_properties]
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rh-allow-sha1-signatures = yes
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$ OPENSSL_CONF=/var/tmp/openssl.cnf ./run virsh -c 'qemu+ssh://root@192.168.0.91/system' list
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root@192.168.0.91's password:
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Id Name State
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--------------------
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Essentially my argument here is that OPENSSL_CONF is sufficiently
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similar in nature to KRB5CCNAME, SSH* and XAUTHORITY that we should
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permit it to be passed through.
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virt-v2v bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2062360
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Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
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Acked-by: Laszlo Ersek <lersek@redhat.com>
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Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
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(cherry picked from commit 45912ac399abd9d4eba21fa3f15cb7587351f959)
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Libvirt BZ: https://bugzilla.redhat.com/show_bug.cgi?id=2112348
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Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
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---
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src/rpc/virnetsocket.c | 1 +
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1 file changed, 1 insertion(+)
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diff --git a/src/rpc/virnetsocket.c b/src/rpc/virnetsocket.c
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index 32f506d2d4..8280bda007 100644
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--- a/src/rpc/virnetsocket.c
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+++ b/src/rpc/virnetsocket.c
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@@ -855,6 +855,7 @@ int virNetSocketNewConnectSSH(const char *nodename,
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virCommandAddEnvPass(cmd, "KRB5CCNAME");
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virCommandAddEnvPass(cmd, "SSH_AUTH_SOCK");
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virCommandAddEnvPass(cmd, "SSH_ASKPASS");
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+ virCommandAddEnvPass(cmd, "OPENSSL_CONF");
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virCommandAddEnvPass(cmd, "DISPLAY");
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virCommandAddEnvPass(cmd, "XAUTHORITY");
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virCommandClearCaps(cmd);
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--
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2.35.1
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