allow the user to provide a shared secret for authentication

autoca/ca_tool.py

 import optparse
+import os
 import logging
 import sys
 from OpenSSL import crypto
@@ -30,13 +31,21 @@ def main():
     parser.add_option('--subject', dest='subject',
                       help='specify the X.509 subject as a set of '
                       'comma-separated ATTR=VALUE assignments')
+    parser.add_option('--secret', dest='secret',
+                      help='shared secret for authentication')
     opts, args = parser.parse_args()
     if len(args) < 1:
         parser.error('No command specified')
     if not opts.url:
         parser.error('Must specify --url')
 
-    ca = ca_stub.CaStub(opts.url)
+    secret = opts.secret
+    if not secret:
+        if os.getenv('AUTOCA_SECRET'):
+            with open(os.getenv('AUTOCA_SECRET'), 'r') as fd:
+                secret = fd.read().strip()
+
+    ca = ca_stub.CaStub(opts.url, secret)
 
     cmd, args = args[0], args[1:]
     if cmd == 'get-ca':