Add support for variable expansion in SSHConfig

(cherry picked from commit 31482a46d6)

paramiko/config.py

@@ -21,7 +21,10 @@ L{SSHConfig}.
 """
 
 import fnmatch
+import os
+import socket
 
+SSH_PORT=22
 
 class SSHConfig (object):
     """
@@ -115,18 +118,56 @@ class SSHConfig (object):
         Return a dict of config options with expanded substitutions
         for a given hostname.
 
-        For the moment only expansion of the %h substitution in the 
-        hostname config is supported.
+        Please refer to man ssh_config(5) for the parameters that
+        are replaced.
 
         @param config: the config for the hostname
         @type hostname: dict
         @param hostname: the hostname that the config belongs to
         @type hostname: str
         """
-        #TODO: Add support for expansion of all substitution parameters
-        #TODO: see man ssh_config(5)
+
         if 'hostname' in config:
             config['hostname'] = config['hostname'].replace('%h',hostname)
         else:
             config['hostname'] = hostname
+
+        if 'port' in config:
+            port = config['port']
+        else:
+            port = SSH_PORT
+
+        user = os.getenv('USER')
+        if 'user' in config:
+            remoteuser = config['user']
+        else:
+            remoteuser = user
+
+        host = socket.gethostname().split('.')[0]
+        fqdn = socket.getfqdn()
+        homedir = os.path.expanduser('~')
+        replacements = {'controlpath' :
+                [
+                    ('%h', config['hostname']),
+                    ('%l', fqdn),
+                    ('%L', host),
+                    ('%n', hostname),
+                    ('%p', port),
+                    ('%r', remoteuser),
+                    ('%u', user)
+                ],
+                'identityfile' :
+                [
+                    ('~', homedir),
+                    ('%d', homedir),
+                    ('%h', config['hostname']),
+                    ('%l', fqdn),
+                    ('%u', user),
+                    ('%r', remoteuser)
+                ]
+                }
+        for k in config:
+            if k in replacements:
+                for find, replace in replacements[k]:
+                        config[k] = config[k].replace(find, str(replace))
         return config