| """The code this worker prints for the people allowed to use it. |
| |
| **Why a worker hands out a code at all.** A server knows who is signed in; it |
| does not know whose machine an agent is. The operator of the machine does, and |
| this is how they say so: the worker prints one code when it starts, they give |
| it to the people who should be able to use it, and those people enter it on a |
| server they have signed in to. The server keeps a digest, never the code. |
| |
| It is deliberately not derived from anything. A code computed from a hostname, |
| a port, a start time or an agent id would be guessable by anybody who knew |
| those, and every one of them is public or nearly so. |
| """ |
|
|
| from __future__ import annotations |
|
|
| import base64 |
| import secrets |
| from collections.abc import Sequence |
|
|
| |
| |
| |
| ACCESS_CODE_BYTES = 24 |
|
|
|
|
| def new_access_code() -> str: |
| """192 random bits, in groups of five. |
| |
| Grouped because it is going to be read aloud and retyped at least once by |
| somebody who is not enjoying it, and base32 because a code containing |
| both `l` and `1` is a support request waiting to happen. |
| """ |
|
|
| raw = base64.b32encode(secrets.token_bytes(ACCESS_CODE_BYTES)).decode("ascii").rstrip("=") |
| return "-".join(raw[index : index + 5] for index in range(0, len(raw), 5)) |
|
|
|
|
| def announce_access_code(code: str, servers: "Sequence[str]" = ()) -> str: |
| """What the worker prints, once, when it starts. |
| |
| In full rather than summarised, because this is the only moment it exists |
| in a readable form: the servers keep a digest of it and this process does |
| not write it to disk. |
| |
| ``servers`` are named in the invitation when they are known, because the |
| two halves of the instruction are useless apart: a code with no address is |
| a key to a door nobody can find. It is written as a sentence somebody can |
| forward as-is, since forwarding it is the entire point. |
| |
| A sequence, not a string, because ``--server`` is repeatable and one |
| worker can serve several servers on the same code. An earlier version |
| took the argument straight from argparse and printed |
| ``Sign in at ['http://…']``, which is what happens when a list is asked |
| to be a sentence. |
| |
| THIS CODE IS DELIBERATELY NOT ONE-TO-ONE. It is not consumed by being |
| used and it is not tied to whoever redeems it first; every person who |
| enters it is added to the set allowed to see this worker. That is the |
| sharing model, and the wording says so, because a reader who assumed one |
| code meant one person would go looking for a way to mint more. |
| """ |
|
|
| addresses = [str(item).strip() for item in servers if str(item).strip()] |
| if len(addresses) == 1: |
| where = f" at {addresses[0]}" |
| elif addresses: |
| where = " at " + ", ".join(addresses[:-1]) + f" or {addresses[-1]}" |
| else: |
| where = "" |
| return ( |
| "\n" |
| " Access code for this worker:\n" |
| f" {code}\n" |
| "\n" |
| f" Send this to anyone who should be able to use this machine:\n" |
| f" Sign in{where} and enter this code under \"Add a worker\":\n" |
| f" {code}\n" |
| "\n" |
| " The same code works for as many people as you give it to — it is\n" |
| " not used up by the first person to enter it. Anybody holding it\n" |
| " can send this worker requests, so treat it like a key. Restarting\n" |
| " the worker issues a new one and retires this.\n" |
| ) |
|
|
