agent: add --shell and --connect flags

--shell: opens $SHELL as subprocess
--connect: connect via SSH to specified identity's host

sshagent/trezor_agent.py

@@ -13,43 +13,51 @@ log = logging.getLogger(__name__)
 def main():
     fmt = '%(asctime)s %(levelname)-12s %(message)-100s [%(filename)s:%(lineno)d]'
     p = argparse.ArgumentParser()
-    g = p.add_mutually_exclusive_group()
-    g.add_argument('-v', '--verbose', default=0, action='count')
-    g.add_argument('-q', '--quiet', default=False, action='store_true')
-
-    p.add_argument('-p', '--public-key', default=False, action='store_true')
+    p.add_argument('-v', '--verbose', default=0, action='count')
 
     p.add_argument('-i', '--identity', type=str,
                    help='proto://[user@]host[:port][/path]')
-    p.add_argument('command', type=str, nargs='*',
+
+    g = p.add_mutually_exclusive_group()
+    g.add_argument('-s', '--shell', default=False, action='store_true',
+                   help='run $SHELL as subprocess under SSH agent')
+    g.add_argument('-c', '--connect', default=False, action='store_true',
+                   help='connect to specified host via SSH')
+    p.add_argument('argument', type=str, nargs='*', metavar='ARGUMENT',
                    help='command to run under the SSH agent')
     args = p.parse_args()
 
-    loglevel = logging.INFO
-    if args.verbose:
-        loglevel = logging.DEBUG
-    if args.quiet:
-        loglevel = logging.WARNING
-
-    logging.basicConfig(level=loglevel, format=fmt)
+    levels = [logging.WARNING, logging.INFO, logging.DEBUG]
+    level = levels[min(args.verbose, len(levels))]
+    logging.basicConfig(level=level, format=fmt)
 
     with trezor.Client(factory=trezor.TrezorLibrary) as client:
         identity = client.get_identity(label=args.identity)
         public_key = client.get_public_key(identity=identity)
-        if args.public_key:
-            sys.stdout.write(public_key)
-            return
 
-        command, use_shell = args.command, False
-        if not command:
+        command, use_shell = args.argument, False
+        if args.connect:
+            to_ascii = lambda s: s.encode('ascii')
+            command = ['ssh', to_ascii(identity.host)]
+            if identity.user:
+                command += ['-l', to_ascii(identity.user)]
+            if identity.port:
+                command += ['-p', to_ascii(identity.port)]
+            log.debug('SSH connect: %r', command)
+
+        if args.shell:
             command, use_shell = os.environ['SHELL'], True
+            log.debug('using shell: %r', command)
+
+        if not command:
+            sys.stdout.write(public_key)
+            return
 
         signer = client.sign_ssh_challenge
 
         try:
             with server.serve(public_keys=[public_key], signer=signer) as env:
-                return server.run_process(
-                    command=command, environ=env, use_shell=use_shell
-                )
+                return server.run_process(command=command, environ=env,
+                                          use_shell=use_shell)
         except KeyboardInterrupt:
             log.info('server stopped')