notes

cmd/welcome/README.md

@@ -27,7 +27,7 @@ an invite token consists of two pieces that are then base64 encoded. the first p
 something like:
 
 ```
-welcome ALL=(ALL)NOPASSWD:/usr/sbin/adduser,/usr/sbin/usermod,/bin/mkdir,/town/bin/generate_welcome_present.sh
+welcome ALL=(ALL)NOPASSWD:/usr/sbin/adduser,/usr/sbin/usermod,/bin/mkdir,/town/bin/generate_welcome_present.sh,/town/bin/create_keyfile
 ```
 
 though I will likely move welcome_present generation inline to `welcome` itself.
@@ -45,3 +45,35 @@ once we accept what we need from the user accepting an invite, the flow looks li
   c. write blank `~/.ssh/authorized_keys` with note about adding custom keys
 3. generate welcome gift
 4. alert hooks (more of a future idea; but it would be nice to have a "WELCOME NEW USER!" in the mailing list / IRC / etc)
+
+## creating keyfiles
+
+A frustrating hurdle is that `welcome`, just like `ttadmin`, has to write a keyfile that is perms 600 for the new user. This is annoying as shit and requires running `sudo` as the new user. In the old python code:
+
+```python
+def write_authorized_keys(self):
+    # Write out authorized_keys file
+    # Why is this a call out to a python script? There's no secure way with
+    # sudoers to allow this code to write to a file; if this code was to be
+    # compromised, the ability to write arbitrary files with sudo is a TKO.
+    # By putting the ssh key file creation into its own script, we can just
+    # give sudo access for that one command to this code.
+    #
+    # We could put the other stuff from here into that script and then only
+    # grant sudo for the script, but then we're moving code out of this
+    # virtual-env contained, maintainable thing into a script. it's my
+    # preference to have the script be as minimal as possible.
+    with TemporaryFile(dir="/tmp") as fp:
+        fp.write(self.generate_authorized_keys().encode('utf-8'))
+        fp.seek(0)
+        error = _guarded_run(['sudo',
+                              '--user={}'.format(self.username),
+                              '/town/src/tildetown-admin/scripts/create_keyfile.py',
+                              self.username],
+                             stdin=fp)
+        if error:
+            logger.error(error)
+
+```
+
+this warrants porting `create_keyfile.py` to a new Go program that can live at `/town/bin/create_keyfile` or wherever.