Support both TLS encrypted sessions and plaintext sessions

Added support for both TLS and plaintext connections. Server can accept
both types of connection simultaneously or in different combinations
(i.e encrypted client and plaintext PAM). Added options for specifying
dedicated TLS ports on server. Added --plain options for client and PAM
to force plaintext connections, default is to use encrypted connections.

Configuring encrypted client and PAM connections and plaintext server
connections allows for use of a reverse proxy setup with something like
nginx. This will avoid having to expose the MFA server directly in setups
that traverse the internet.

1 files changed, 37 insertions, 9 deletions

diff --git a/pam/pam_mfa.py b/pam/pam_mfa.py
index 5a5a112..a5105a2 100755
--- a/pam/pam_mfa.py
+++ b/pam/pam_mfa.py
@@ -34,11 +34,12 @@ def parse_arguments():
                         default="/etc/mfa/mfa.conf")
     parser.add_argument("--server",type=str,help="MFA server address")
     parser.add_argument("--port",type=str,help="MFA server PAM connection port")
+    parser.add_argument("--plain",action="store_true",help="Connect without TLS")
     parser.add_argument("--insecure",action="store_true",
                         help="Accept invalid TLS certificates")
     return parser.parse_args()
 
-def init_connection(mfa_server, pam_port, insecure):
+def init_connection_tls(mfa_server, pam_port, insecure):
     # Attempts to connect to MFA server with provided address and port
     # Repeats connection attempts once per second until timeout is reached
     # Returns the socket if connection was successful or None otherwise
@@ -52,7 +53,6 @@ def init_connection(mfa_server, pam_port, insecure):
         context.verify_mode = 0
     while connection == None and timeout < timeout_length:
         try:
-            #connection = socket.create_connection((mfa_server,client_port))
             connection = context.wrap_socket(socket.socket(socket.AF_INET),
                                              server_hostname=mfa_server)
             connection.connect((mfa_server,int(pam_port)))
@@ -65,6 +65,24 @@ def init_connection(mfa_server, pam_port, insecure):
     return None
 
 
+def init_connection(mfa_server, pam_port):
+    # Attempts to connect to MFA server with provided address and port
+    # Repeats connection attempts once per second until timeout is reached
+    # Returns the socket if connection was successful or None otherwise
+    connection = None
+    timeout = 0
+    timeout_length = 5
+    sleep_length = 1
+    while connection == None and timeout < timeout_length:
+        try:
+            connection = socket.create_connection((mfa_server,pam_port))
+            return connection
+        except (ConnectionError,ConnectionRefusedError):
+            time.sleep(sleep_length)
+            timeout += sleep_length
+    return None
+
+
 def read_config(config_file):
     # Read config file for server and port info
     # Return tuple (server,port)
@@ -94,19 +112,28 @@ def get_vars(args,confparser):
 
     server = None
     port = None
+    plain = None
     insecure = None
 
     # Set values from config file first
     if confparser.has_section("pam"):
         server = confparser.get("pam","server",fallback=None) 
         port = confparser.get("pam","port",fallback=None) 
-        insecure = bool(confparser.get("pam","insecure",fallback=False))
+        plain = confparser.get("client","plain",fallback=False)
+        insecure = confparser.get("client","insecure",fallback=False)
         
+    if plain.lower() == "false":
+        plain = False
+    if insecure.lower() == "false":
+        insecure = False
+
     # Let command line args overwrite any values
     if args.server != None:
         server = args.server
     if args.port != None:
         port = args.port
+    if args.plain:
+        plain = args.plain
     if args.insecure:
         insecure = args.insecure
 
@@ -115,7 +142,7 @@ def get_vars(args,confparser):
         print("error: one or more items unspecified")
         sys.exit(1)
 
-    return server,port,insecure
+    return server,port,plain,insecure
 
 
 def main():
@@ -125,7 +152,7 @@ def main():
     # Get arguments
     args = parse_arguments()
     confparser = read_config(args.config)
-    mfa_server,pam_port,insecure = get_vars(args,confparser)
+    mfa_server,pam_port,plain,insecure = get_vars(args,confparser)
     user = args.user
     service = args.service
 
@@ -144,12 +171,13 @@ def main():
         hostname = args.host
     data = user + "," + hostname + "," + service 
     
-
     # Initalize connection to MFA server.  Quit if unable to connect.
-    connection = init_connection(mfa_server,pam_port,insecure)
+    if plain:
+        connection = init_connection(mfa_server, pam_port)
+    else:
+        connection = init_connection_tls(mfa_server,pam_port,insecure)
     if connection == None:
-        print(failed)
-        sys.exit(1)
+        die("failed to connect")
 
     # Send authentication data to MFA server
     data_length = len(data)