Manage bastion SSH known_hosts file

This attempts to manage the SSH host keys of all the hosts in the
inventory. The idea here is each host in the inventory will add a
ansible_ssh_host_key_ecdsa_public variable, then when we first run our
bastion playbook we'll properly populate the local known_hosts file each
time.

Change-Id: I26e328192a7127086e514dc62a27cb946a77440b
Depends-On: https://review.openstack.org/643408
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

launch/launch-node.py

@@ -69,6 +69,10 @@ def bootstrap_server(server, key, name, group, keep, timeout):
     ansible_user = None
 
     print("--- Running initial configuration on host %s ---" % ip)
+    host_key = utils.nodescan(ip)
+    if not host_key:
+        raise Exception("Unable to find ssh-ecdsa SSH host key")
+
     for username in ['ubuntu', 'centos']:
         ssh_client = utils.ssh_connect(
             ip, username, ssh_kwargs, timeout=timeout)
@@ -87,9 +91,10 @@ def bootstrap_server(server, key, name, group, keep, timeout):
         with open(runner.hosts, 'w') as inventory_file:
             inventory_file.write(
                 "[{group}]\n{host} ansible_host={ip} "
-                "ansible_user={user}".format(
+                "ansible_user={user} "
+                "ansible_ssh_host_key_ed25519_public={host_key}".format(
                     group=group, host=name, ip=server.interface_ip,
-                    user=ansible_user))
+                    user=ansible_user, host_key=host_key))
 
         project_dir = os.path.join(
             SCRIPT_DIR, '..', 'playbooks', 'bootstrap-ansible')

launch/utils.py

@@ -15,6 +15,7 @@
 # limitations under the License.
 
 import socket
+import subprocess
 import time
 
 import paramiko
@@ -32,6 +33,30 @@ def iterate_timeout(max_seconds, purpose):
     raise Exception("Timeout waiting for %s" % purpose)
 
 
+def nodescan(ip, port=22, timeout=60):
+    """Scan the IP address for public SSH keys.
+
+    Returns SSH host key
+    """
+
+    key = None
+    output = None
+    for count in iterate_timeout(
+            timeout, "connection to %s on port %s" % (ip, port)):
+
+        try:
+            output = subprocess.check_output(
+                ['ssh-keyscan', '-t', 'ed25519', '-p', str(port), str(ip)])
+            if output:
+                break
+        except Exception as e:
+            print("ssh-keyscan failure: %s", e)
+
+    key = output.split()[2].decode('utf8')
+
+    return key
+
+
 def ssh_connect(ip, username, connect_kwargs={}, timeout=60):
     # HPcloud may return errno 111 for about 30 seconds after adding the IP
     for count in iterate_timeout(timeout, "ssh access"):

playbooks/bootstrap/site.yaml

@@ -12,6 +12,15 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 ---
+- name: Configure bastion SSH known_hosts
+  hosts: bastion:!disabled
+  gather_facts: false
+  tasks:
+    - name: Ensure SSH host keys are known
+      template:
+        dest: ~/.ssh/known_hosts
+        src: bastion/root/.ssh/known_hosts.j2
+
 - name: Bootstrap all hosts
   hosts: all:!disabled
   tasks:

playbooks/bootstrap/templates/bastion/root/.ssh/known_hosts.j2

@@ -0,0 +1,10 @@
+# This file is generated by Ansible
+#  DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
+#
+{% for host in groups['all'] %}
+{% if hostvars[host].ansible_host is defined %}
+{% if hostvars[host].ansible_ssh_host_key_ed25519_public is defined %}
+{{ hostvars[host].ansible_host }} ssh-ed25519 {{ hostvars[host].ansible_ssh_host_key_ed25519_public }}
+{% endif %}
+{% endif %}
+{% endfor %}