nebula-token 1.0.1

Opaque rotating refresh tokens (RFC 9700 model): rotation, reuse detection, family revocation, sender binding. Stdlib only.

nebula-token

Python reference implementation of NEBULA — opaque rotating refresh tokens (RFC 9700 model). Standard library only, Python ≥ 3.11. Implements spec_version = 1.

pip install nebula-token

import os
from nebula_token import NebulaEngine, MemoryRefreshTokenStore

engine = NebulaEngine(
    peppers={"k1": os.environ["NEBULA_PEPPER_K1"]},  # >= 32 BYTES, from env/KMS
    active_kid="k1",
    store=MemoryRefreshTokenStore(),  # dev only — implement RefreshTokenStore for production
    reuse_grace_seconds=0,            # see [N-30] before raising this
)

issued = engine.issue("usr_1", device_id)
# issued.token, .user_id, .family_id, .generation, .expires_at, .idle_expires_at

result = engine.refresh(issued.token, device_id)
if result.ok:
    ...            # persist result.token client-side; the presented token is dead
else:
    result.error   # "REUSE_DETECTED", "CONFLICT", … — treat an unknown code as a refusal

API

Call	Returns
issue(user_id, device_id=None)	IssueResult — raises NebulaConfigError for an invalid device_id
refresh(token, device_id=None)	RefreshOk | RefreshError (never raises for protocol outcomes)
revoke_token(token)	RevokeOk | RevokeError — authenticated: proves the verifier, then revokes the family and reports revoked. Takes no device identifier ([N-36])
revoke_family(family_id)	int revoked — administrative, no token required
revoke_all_for_user(user_id)	int revoked — administrative, no token required

Timestamps are integer Unix seconds everywhere. device_id=None (unbound) and device_id="" (bound to the empty string) are different values.

Failure results carry user_id and family_id whenever the engine resolved a record — every code except MALFORMED, UNKNOWN_KID and NOT_FOUND — so a security event can be attributed without a second lookup.

NebulaErrorCode is a closed Literal for type checking but an open set at runtime: a future minor version may add a code, so treat an unrecognised value as a refusal rather than assuming your if/elif chain is exhaustive.

Stores

RefreshTokenStore is a six-method Protocol; mark_rotated and revoke_if_active are compare-and-set and must return whether they applied — returning True unconditionally re-opens the race that forks a token family. examples/sqlite_store.py is a runnable template; the schema is in docs/STORE.md.

The contract is synchronous. Blocking drivers are the Python norm, and an engine that never awaits cannot silently discard a coroutine. Under asyncio, call the engine off the event loop:

result = await asyncio.to_thread(engine.refresh, token, device_id)

Do not give the engine a store whose methods are async def: nothing awaits them, so insert would return an un-awaited coroutine and the engine would hand out a token for a record that was never written.

Infrastructure failures (store unreachable, timeout, constraint violation) must raise; the exception propagates out of the engine and is never converted into a protocol outcome, so callers fail closed.

MemoryRefreshTokenStore is mutex-guarded and safe across threads, but is per-process and lost on restart — development and tests only.

Tests

cd packages/python
pip install pytest
pytest -q

pyproject.toml puts the source tree and tests/ on sys.path (tool.pytest.ini_options.pythonpath), so no install step is needed. The suites read the normative artifacts from spec/ in the repository root, located by walking up from the test file:

• tests/test_conformance.py — spec/test-vectors.json (46 cases)
• tests/test_behavior.py + tests/behavior_runner.py — spec/behavior-vectors.json (38 scenarios)
• tests/test_engine.py — what the vectors cannot express: the constant-time guard, concurrency, store failures, configuration, and secret hygiene

Type checking: pip install mypy && mypy --strict (configured in pyproject.toml).

See the repository README and SPECIFICATION.md.

Agent skill: skills/nebula-token-python/SKILL.md teaches an AI coding assistant to integrate this package correctly. Install it with the standard agent-skill installer:

npx skills add nebula-token/nebula-token --skill nebula-token-python

That lands in the project's .claude/skills/, checked in and shared with your team; add -g for your personal ~/.claude/skills/ instead. In Claude Code it is equally a plugin — /plugin marketplace add nebula-token/nebula-token, then /plugin install nebula-token-python@nebula-token. Neither route copies anything: both read this directory in place, through .claude-plugin/marketplace.json.

As a fallback the skill also ships inside the published artefact, in the same installable shape — after pip install nebula-token the directory is at <site-packages>/nebula_token/skills/nebula-token-python/, and copying that directory into ~/.claude/skills/ is the whole installation. All ten skills and every install route are in skills/README.md.