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README.md | ||
form.go | ||
main.go | ||
welcome.txt |
README.md
welcome command
this command is used to exchange a town invite token for a user account. it is responsible for:
- accepting and validating an invite token generated by the
review
command - accepting and validating a new user's username choice (ie enforcing rules and checking for dupes)
- accepting and validating a user's email for use in account recovery (defaulting to an email embedded in the invite token)
- accepting and validating a display name (PUT OFF)
- Confirming that a user agrees to our CoC
- accepting and validating a user's public ssh key
upon receipt of these things a user account is created. if it fails, the user is told about the failure and told to email root@tilde.town for guidance; us admins get a local mail about the problem.
upon successful creation, welcome
prints a message on STDOUT suggesting how to log in then quits.
It is risky to let welcome
create users but no riskier at a high level than the Django admin we had. I can re-use the sudoers trick I did there for the welcome
user.
an invite token
an invite token consists of two pieces that are then base64 encoded. the first piece is a random string of 30 characters (alphanumeric and symbols except space) and the second is an email address the invite was sent to; they are separated by a space.
sudoers config
something like:
welcome ALL=(ALL)NOPASSWD:/usr/sbin/adduser,/usr/sbin/usermod,/town/bin/createkeyfile,/town/bin/generate_welcome_present.sh,/town/bin/registeruser
I'd like to consolidate adduser/usermod calls into a single "createuser" helper. I'd also like to move the welcome present generation into welcome
. TODO.
user creation flow
once we accept what we need from the user accepting an invite, the flow looks like:
- create user account
a. run
adduser
, set shell and displayname b. add user to town group - write authorized keys
a. create
~/.ssh
b. write~/.ssh/authorized_keys2
and put their key in there c. write blank~/.ssh/authorized_keys
with note about adding custom keys - generate welcome gift
- 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:
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.