launch-node : add sshfp records

Add a tool to scan a host and generate the sshfp records to go into
dns.  Hook this into the DNS print out from the node launcher.

Change-Id: I686287c3c081debeb6a230e2a3e7b48e5720c65a

launch/dns.py

@@ -19,7 +19,7 @@
 # limitations under the License.
 
 import argparse
-
+from sshfp import sshfp_print_records
 
 def get_href(server):
     if not hasattr(server, 'links'):
@@ -50,7 +50,7 @@ def print_dns_opendev(name, ip4, ip6):
     print("{name}			IN	A	{ip4}".format(name=name, ip4=ip4))
     if ip6:
         print("{name}			IN	AAAA	{ip6}".format(name=name, ip6=ip6))
-
+    sshfp_print_records(name, ip4)
 
 def print_reverse_dns(cloud, server, ip4, ip6):
     # Get the server object from the sdk layer so that we can pull the

launch/sshfp.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+
+import argparse
+import subprocess
+
+def generate_sshfp_records(hostname, ip):
+    '''Given a hostname and and IP address, scan the IP address (hostname
+    not in dns yet) and return a bind string with sshfp records'''
+
+    s = subprocess.run(['ssh-keyscan', '-D', ip],
+                       stdout=subprocess.PIPE,
+                       stderr=subprocess.PIPE).stdout.decode('utf-8')
+
+    fingerprints = []
+    for line in s.split('\n'):
+        if not line:
+            continue
+        _, _, _, algo, key_type, fingerprint = line.split(' ')
+        fingerprints.append(
+            (algo, key_type, fingerprint))
+
+    # sort by algo and key_type to keep it consistent
+    fingerprints = sorted(fingerprints,
+                          key=lambda x: (x[0], x[1]))
+
+    ret = ''
+    first = True
+    for f in fingerprints:
+        ret += '%s%s\t\tIN\tSSHFP\t%s %s %s' % \
+            ("\n" if not first else '', hostname, f[0], f[1], f[2])
+        first = False
+    return ret
+
+
+def sshfp_print_records(hostname, ip):
+    print(generate_sshfp_records(hostname, ip))
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("hostname", help="hostname")
+    parser.add_argument("ip", help="address to scan")
+    args = parser.parse_args()
+
+    sshfp_print_records(args.hostname, args.ip)
+
+if __name__ == '__main__':
+    main()