Create script to add and remove mentor's ssh key from DO droplets.

tools/droplets/add_mentor.py

@@ -0,0 +1,75 @@
+# Allows a mentor to ssh into a Digital Ocean droplet. This is designed to be
+# executed on the target machine.
+#
+# This script takes the username of the mentor as an argument:
+#
+# $ python3 add_mentor.py <mentor's username>
+#
+# Alternatively you can pass in --remove to remove their ssh key from the
+# machine:
+#
+# $ python3 add_mentor.py --remove <mentor's username>
+
+import os
+import sys
+from argparse import ArgumentParser
+from typing import List
+import socket
+import re
+
+import requests
+
+parser = ArgumentParser(description='Give a mentor ssh access to this machine.')
+parser.add_argument('username', help='Github username of the mentor.')
+parser.add_argument('--remove', help='Remove his/her key from the machine.',
+                    action='store_true', default=False)
+
+# Wrap keys with line comments for easier key removal.
+append_key = """\
+#<{username}>{{{{
+{key}
+#}}}}<{username}>
+"""
+
+def get_mentor_keys(username: str) -> List[str]:
+    url = 'https://api.github.com/users/{}/keys'.format(username)
+
+    r = requests.get(url)
+    if r.status_code != 200:
+        print('Cannot connect to Github...')
+        sys.exit(1)
+
+    keys = r.json()
+    if not keys:
+        print('Mentor "{}" has no public key.'.format(username))
+        sys.exit(1)
+
+    return [key['key'] for key in keys]
+
+
+if __name__ == '__main__':
+    args = parser.parse_args()
+    authorized_keys = os.path.expanduser('~/.ssh/authorized_keys')
+
+    if args.remove:
+        remove_re = re.compile('#<{0}>{{{{.+}}}}<{0}>(\n)?'.format(args.username),
+                               re.DOTALL | re.MULTILINE)
+
+        with open(authorized_keys, 'r+') as f:
+            old_content = f.read()
+            new_content = re.sub(remove_re, '', old_content)
+            f.seek(0)
+            f.write(new_content)
+            f.truncate()
+
+        print('Successfully removed {}\' SSH key!'.format(args.username))
+
+    else:
+        keys = get_mentor_keys(args.username)
+        with open(authorized_keys, 'a') as f:
+            for key in keys:
+                f.write(append_key.format(username=args.username, key=key))
+
+        print('Successfully added {}\'s SSH key!'.format(args.username))
+        print('Can you let your mentor know that they can connect to this machine with:\n')
+        print('    $ ssh zulipdev@{}\n'.format(socket.gethostname()))