# Gitea OAuth2 Authentication Implementation Plan

> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.

**Goal:** Add Gitea as an OAuth2 login provider that coexists with password auth, auto-provisioning new users on first login.

**Architecture:** A new `oauth.py` module owns all Gitea-specific logic (CSRF state, URL building, token exchange, user-info fetch). `users.py` gains one function to upsert an OAuth-sourced user. `http.py` gets two new route handlers and a small login-page change. No new dependencies — `aiohttp.ClientSession` is already used in the codebase.

**Tech Stack:** Python 3.12, aiohttp 3.x, pytest, pytest-asyncio

---

## File Map

| Action | Path | Responsibility |
|--------|------|----------------|
| Modify | `hbd/server/config.py` | Add `"oauth": {}` default |
| Create | `hbd/server/oauth.py` | CSRF state, URL builder, token exchange, user-info fetch |
| Modify | `hbd/server/users.py` | Add `provision_oauth_user()` |
| Modify | `hbd/server/http.py` | Import oauth, two new routes, login page button |
| Create | `tests/test_oauth.py` | All new unit tests |

---

## Task 1: Add config default and `is_enabled()`

**Files:**
- Modify: `hbd/server/config.py:34` (after the `"users"` line)
- Create: `hbd/server/oauth.py`
- Create: `tests/test_oauth.py`

- [ ] **Step 1: Write the failing test**

Create `tests/test_oauth.py`:

```python
import pytest
from hbd.server import oauth


CFG_OFF = {}
CFG_ON = {
    "oauth": {
        "gitea": {
            "url": "https://git.example.com",
            "client_id": "cid",
            "client_secret": "csec",
        }
    }
}
CFG_PARTIAL = {"oauth": {"gitea": {"url": "https://git.example.com"}}}


def test_is_enabled_when_all_keys_present():
    assert oauth.is_enabled(CFG_ON) is True


def test_is_enabled_false_when_no_oauth_key():
    assert oauth.is_enabled(CFG_OFF) is False


def test_is_enabled_false_when_partial_config():
    assert oauth.is_enabled(CFG_PARTIAL) is False
```

- [ ] **Step 2: Run to confirm failure**

```
pytest tests/test_oauth.py -v
```

Expected: `ModuleNotFoundError: No module named 'hbd.server.oauth'`

- [ ] **Step 3: Add config default**

In `hbd/server/config.py`, add after the `"default_owner"` line (currently line 35):

```python
    # OAuth2 providers
    "oauth": {},                 # oauth.gitea.{url,client_id,client_secret}
```

- [ ] **Step 4: Create `hbd/server/oauth.py` with `is_enabled`**

```python
"""Gitea OAuth2 support.

Config shape (in ~/.hb.yaml):

    oauth:
      gitea:
        url: https://git.example.com
        client_id: <client-id>
        client_secret: <client-secret>

Register a Gitea OAuth2 application at:
  Gitea → Settings → Applications → OAuth2
Set the redirect URI to:
  https://<hbd-host>/login/oauth/gitea/callback
"""

import logging
import secrets
import time

import aiohttp

logger = logging.getLogger(__name__)

STATE_TTL = 600  # 10 minutes

# state_token -> expiry timestamp
_states: dict[str, float] = {}


class OAuthError(Exception):
    """Raised when the OAuth2 flow fails for any reason."""


def _gitea_cfg(config: dict) -> dict:
    """Return the gitea sub-dict or {} if absent/incomplete."""
    return config.get("oauth", {}).get("gitea", {})


def is_enabled(config: dict) -> bool:
    """Return True when all three required Gitea OAuth keys are present."""
    g = _gitea_cfg(config)
    return bool(g.get("url") and g.get("client_id") and g.get("client_secret"))
```

- [ ] **Step 5: Run to confirm tests pass**

```
pytest tests/test_oauth.py -v
```

Expected: 3 passed

- [ ] **Step 6: Commit**

```bash
git add hbd/server/config.py hbd/server/oauth.py tests/test_oauth.py
git commit -m "feat: add oauth module skeleton and is_enabled()"
```

---

## Task 2: CSRF state management

**Files:**
- Modify: `hbd/server/oauth.py` (add `make_state`, `validate_state`)
- Modify: `tests/test_oauth.py` (add state tests)

- [ ] **Step 1: Write the failing tests**

Append to `tests/test_oauth.py`:

```python
import time as time_mod


def test_make_state_returns_unique_tokens():
    s1 = oauth.make_state()
    s2 = oauth.make_state()
    assert s1 != s2
    assert len(s1) == 64  # 32 bytes hex


def test_validate_state_valid():
    state = oauth.make_state()
    assert oauth.validate_state(state) is True


def test_validate_state_consumed_on_use():
    state = oauth.make_state()
    oauth.validate_state(state)
    assert oauth.validate_state(state) is False  # replay rejected


def test_validate_state_unknown():
    assert oauth.validate_state("notastate") is False


def test_validate_state_expired(monkeypatch):
    state = oauth.make_state()
    # Wind expiry into the past
    monkeypatch.setitem(oauth._states, state, time_mod.time() - 1)
    assert oauth.validate_state(state) is False
```

- [ ] **Step 2: Run to confirm failure**

```
pytest tests/test_oauth.py -v -k "state"
```

Expected: `AttributeError: module 'hbd.server.oauth' has no attribute 'make_state'`

- [ ] **Step 3: Implement state functions**

Add to `hbd/server/oauth.py` after the `_states` dict definition:

```python
def make_state() -> str:
    """Generate a CSRF state token, store it with TTL, and return it."""
    _purge_states()
    token = secrets.token_hex(32)
    _states[token] = time.time() + STATE_TTL
    return token


def validate_state(state: str) -> bool:
    """Return True if *state* is known and unexpired; always removes it."""
    expiry = _states.pop(state, None)
    if expiry is None:
        return False
    return time.time() < expiry


def _purge_states() -> None:
    now = time.time()
    expired = [k for k, exp in list(_states.items()) if exp < now]
    for k in expired:
        del _states[k]
```

- [ ] **Step 4: Run to confirm tests pass**

```
pytest tests/test_oauth.py -v
```

Expected: 8 passed

- [ ] **Step 5: Commit**

```bash
git add hbd/server/oauth.py tests/test_oauth.py
git commit -m "feat: add OAuth2 CSRF state management"
```

---

## Task 3: `provision_oauth_user` in users.py

**Files:**
- Modify: `hbd/server/users.py` (add `provision_oauth_user`)
- Modify: `tests/test_oauth.py` (add provisioning tests)

- [ ] **Step 1: Write the failing tests**

Append to `tests/test_oauth.py`:

```python
from hbd.server import users as users_mod
from hbd.server.users import User


def _reset_users(entries=None):
    users_mod.users = entries or {}


def test_provision_oauth_user_new():
    _reset_users()
    user = users_mod.provision_oauth_user("gituser", "Git User", "https://example.com/avatar.png")
    assert user.username == "gituser"
    assert user.full_name == "Git User"
    assert user.avatar == "https://example.com/avatar.png"
    assert user.admin is False
    assert user.password_hash == ""
    assert "gituser" in users_mod.users


def test_provision_oauth_user_no_password_login():
    _reset_users()
    user = users_mod.provision_oauth_user("gituser", "Git User", "")
    assert user.check_password("anything") is False


def test_provision_oauth_user_existing_updates_profile():
    existing = User(
        username="alice",
        full_name="Old Name",
        avatar="old.png",
        password_hash="pbkdf2:sha256:1:salt:abc",
        admin=True,
        notification_channels=["chan1"],
    )
    _reset_users({"alice": existing})
    user = users_mod.provision_oauth_user("alice", "New Name", "new.png")
    assert user.full_name == "New Name"
    assert user.avatar == "new.png"
    # Preserved
    assert user.admin is True
    assert user.password_hash == "pbkdf2:sha256:1:salt:abc"
    assert user.notification_channels == ["chan1"]


def test_provision_oauth_user_does_not_overwrite_with_empty():
    existing = User(username="bob", full_name="Bob", avatar="bob.png")
    _reset_users({"bob": existing})
    user = users_mod.provision_oauth_user("bob", "", "")
    assert user.full_name == "Bob"
    assert user.avatar == "bob.png"
```

- [ ] **Step 2: Run to confirm failure**

```
pytest tests/test_oauth.py -v -k "provision"
```

Expected: `AttributeError: module 'hbd.server.users' has no attribute 'provision_oauth_user'`

- [ ] **Step 3: Implement `provision_oauth_user`**

Add to `hbd/server/users.py` after the `authenticate()` function (after line 187):

```python
def provision_oauth_user(username: str, full_name: str, avatar: str) -> "User":
    """Create or update a user sourced from an OAuth2 provider.

    New users are inserted with no password_hash — they can only authenticate
    via OAuth.  Existing users (e.g. defined in config with a password) have
    their display name and avatar refreshed; all other attributes are preserved.
    """
    user = users.get(username)
    if user is None:
        user = User(username=username, full_name=full_name, avatar=avatar)
        users[username] = user
        logger.info("Provisioned OAuth user %r", username)
    else:
        if full_name:
            user.full_name = full_name
        if avatar:
            user.avatar = avatar
    return user
```

- [ ] **Step 4: Run to confirm tests pass**

```
pytest tests/test_oauth.py -v
```

Expected: 12 passed

- [ ] **Step 5: Commit**

```bash
git add hbd/server/users.py tests/test_oauth.py
git commit -m "feat: add provision_oauth_user() to users module"
```

---

## Task 4: URL builder, token exchange, and user-info fetch

**Files:**
- Modify: `hbd/server/oauth.py` (add `authorization_url`, `exchange_code`, `fetch_user`)
- Modify: `tests/test_oauth.py` (add async tests with mocked HTTP)

- [ ] **Step 1: Write the failing tests**

Append to `tests/test_oauth.py`:

```python
import pytest
from unittest.mock import AsyncMock, MagicMock, patch
from urllib.parse import urlparse, parse_qs


def test_authorization_url_shape():
    state = "teststate"
    redirect_uri = "https://hbd.example.com/login/oauth/gitea/callback"
    url = oauth.authorization_url(CFG_ON, state, redirect_uri)
    parsed = urlparse(url)
    qs = parse_qs(parsed.query)
    assert parsed.scheme == "https"
    assert parsed.netloc == "git.example.com"
    assert parsed.path == "/login/oauth/authorize"
    assert qs["client_id"] == ["cid"]
    assert qs["state"] == ["teststate"]
    assert qs["redirect_uri"] == [redirect_uri]
    assert qs["scope"] == ["user:email"]
    assert qs["response_type"] == ["code"]


@pytest.mark.asyncio
async def test_exchange_code_returns_token():
    redirect_uri = "https://hbd.example.com/login/oauth/gitea/callback"
    mock_response = AsyncMock()
    mock_response.status = 200
    mock_response.json = AsyncMock(return_value={"access_token": "tok123"})

    mock_session = MagicMock()
    mock_session.post = MagicMock(return_value=AsyncMock(
        __aenter__=AsyncMock(return_value=mock_response),
        __aexit__=AsyncMock(return_value=False),
    ))

    with patch("hbd.server.oauth.aiohttp.ClientSession", return_value=AsyncMock(
        __aenter__=AsyncMock(return_value=mock_session),
        __aexit__=AsyncMock(return_value=False),
    )):
        token = await oauth.exchange_code(CFG_ON, "mycode", redirect_uri)
    assert token == "tok123"


@pytest.mark.asyncio
async def test_exchange_code_raises_on_error_status():
    redirect_uri = "https://hbd.example.com/login/oauth/gitea/callback"
    mock_response = AsyncMock()
    mock_response.status = 401
    mock_response.text = AsyncMock(return_value="unauthorized")

    mock_session = MagicMock()
    mock_session.post = MagicMock(return_value=AsyncMock(
        __aenter__=AsyncMock(return_value=mock_response),
        __aexit__=AsyncMock(return_value=False),
    ))

    with patch("hbd.server.oauth.aiohttp.ClientSession", return_value=AsyncMock(
        __aenter__=AsyncMock(return_value=mock_session),
        __aexit__=AsyncMock(return_value=False),
    )):
        with pytest.raises(oauth.OAuthError):
            await oauth.exchange_code(CFG_ON, "badcode", redirect_uri)


@pytest.mark.asyncio
async def test_fetch_user_returns_profile():
    mock_response = AsyncMock()
    mock_response.status = 200
    mock_response.json = AsyncMock(return_value={
        "login": "alice",
        "full_name": "Alice Smith",
        "avatar_url": "https://git.example.com/avatars/alice.png",
    })

    mock_session = MagicMock()
    mock_session.get = MagicMock(return_value=AsyncMock(
        __aenter__=AsyncMock(return_value=mock_response),
        __aexit__=AsyncMock(return_value=False),
    ))

    with patch("hbd.server.oauth.aiohttp.ClientSession", return_value=AsyncMock(
        __aenter__=AsyncMock(return_value=mock_session),
        __aexit__=AsyncMock(return_value=False),
    )):
        profile = await oauth.fetch_user(CFG_ON, "tok123")
    assert profile == {
        "login": "alice",
        "full_name": "Alice Smith",
        "avatar_url": "https://git.example.com/avatars/alice.png",
    }
```

- [ ] **Step 2: Run to confirm failure**

```
pytest tests/test_oauth.py -v -k "url or exchange or fetch"
```

Expected: `AttributeError: module 'hbd.server.oauth' has no attribute 'authorization_url'`

- [ ] **Step 3: Implement the three functions**

Add to `hbd/server/oauth.py`:

```python
import urllib.parse


def authorization_url(config: dict, state: str, redirect_uri: str) -> str:
    """Return the Gitea OAuth2 authorization URL to redirect the browser to."""
    g = _gitea_cfg(config)
    params = urllib.parse.urlencode({
        "client_id": g["client_id"],
        "redirect_uri": redirect_uri,
        "response_type": "code",
        "scope": "user:email",
        "state": state,
    })
    return f"{g['url'].rstrip('/')}/login/oauth/authorize?{params}"


async def exchange_code(config: dict, code: str, redirect_uri: str) -> str:
    """Exchange an authorization *code* for a Gitea access token.

    Returns the access token string.  Raises OAuthError on any failure.
    """
    g = _gitea_cfg(config)
    url = f"{g['url'].rstrip('/')}/login/oauth/access_token"
    payload = {
        "client_id": g["client_id"],
        "client_secret": g["client_secret"],
        "code": code,
        "grant_type": "authorization_code",
        "redirect_uri": redirect_uri,
    }
    timeout = aiohttp.ClientTimeout(total=10)
    try:
        async with aiohttp.ClientSession(timeout=timeout) as session:
            async with session.post(url, json=payload, headers={"Accept": "application/json"}) as resp:
                if resp.status != 200:
                    text = await resp.text()
                    raise OAuthError(f"Token exchange failed ({resp.status}): {text}")
                data = await resp.json()
    except aiohttp.ClientError as exc:
        raise OAuthError(f"Token exchange network error: {exc}") from exc
    token = data.get("access_token")
    if not token:
        raise OAuthError(f"No access_token in response: {data}")
    return token


async def fetch_user(config: dict, token: str) -> dict:
    """Fetch the authenticated user's profile from Gitea.

    Returns a dict with keys: login, full_name, avatar_url.
    Raises OAuthError on any failure.
    """
    g = _gitea_cfg(config)
    url = f"{g['url'].rstrip('/')}/api/v1/user"
    timeout = aiohttp.ClientTimeout(total=10)
    try:
        async with aiohttp.ClientSession(timeout=timeout) as session:
            async with session.get(url, headers={"Authorization": f"token {token}"}) as resp:
                if resp.status != 200:
                    text = await resp.text()
                    raise OAuthError(f"User fetch failed ({resp.status}): {text}")
                data = await resp.json()
    except aiohttp.ClientError as exc:
        raise OAuthError(f"User fetch network error: {exc}") from exc
    return {
        "login": data.get("login", ""),
        "full_name": data.get("full_name", ""),
        "avatar_url": data.get("avatar_url", ""),
    }
```

Also add `import urllib.parse` at the top of `oauth.py` (alongside the existing imports).

- [ ] **Step 4: Run to confirm tests pass**

```
pytest tests/test_oauth.py -v
```

Expected: 17 passed

- [ ] **Step 5: Commit**

```bash
git add hbd/server/oauth.py tests/test_oauth.py
git commit -m "feat: add authorization_url, exchange_code, fetch_user to oauth module"
```

---

## Task 5: HTTP routes — redirect and callback

**Files:**
- Modify: `hbd/server/http.py`

`http.py` defines all handlers inside `async def start(...)`. The two new handlers go in the same block, just before the `app = web.Application()` line (~line 900). The import goes at the top of the file.

- [ ] **Step 1: Add the import**

In `hbd/server/http.py`, add after the existing local imports (after `from . import users as users_mod`):

```python
from . import oauth as oauth_mod
```

- [ ] **Step 2: Add the two route handlers**

In `hbd/server/http.py`, add the two handlers immediately before the `app = web.Application()` line:

```python
    async def oauth_gitea_redirect(request):
        """GET /login/oauth/gitea — kick off the Gitea OAuth2 flow."""
        if not oauth_mod.is_enabled(config):
            return web.Response(status=404, text="OAuth not configured")
        state = oauth_mod.make_state()
        redirect_uri = f"{request.url.origin()}/login/oauth/gitea/callback"
        raise web.HTTPFound(oauth_mod.authorization_url(config, state, redirect_uri))

    async def oauth_gitea_callback(request):
        """GET /login/oauth/gitea/callback — handle Gitea's redirect back."""
        if not oauth_mod.is_enabled(config):
            return web.Response(status=404, text="OAuth not configured")
        code = request.rel_url.query.get("code", "")
        state = request.rel_url.query.get("state", "")
        if not code or not state:
            return web.Response(status=400, text="Missing code or state")
        if not oauth_mod.validate_state(state):
            raise web.HTTPFound("/login?error=1")
        redirect_uri = f"{request.url.origin()}/login/oauth/gitea/callback"
        try:
            token = await oauth_mod.exchange_code(config, code, redirect_uri)
            profile = await oauth_mod.fetch_user(config, token)
        except oauth_mod.OAuthError as exc:
            logger.warning("OAuth error: %s", exc)
            raise web.HTTPFound("/login?error=1")
        user = users_mod.provision_oauth_user(
            profile["login"],
            profile["full_name"],
            profile["avatar_url"],
        )
        session_token = users_mod.create_session(user.username)
        resp = web.HTTPFound("/")
        resp.set_cookie(
            SESSION_COOKIE,
            session_token,
            max_age=users_mod.SESSION_TTL,
            httponly=True,
            samesite="Lax",
        )
        raise resp
```

- [ ] **Step 3: Register the routes**

In `hbd/server/http.py`, add to the route list after the existing auth routes (after `web.post("/api/0/auth/logout", api_logout)`):

```python
            web.get("/login/oauth/gitea",          oauth_gitea_redirect),
            web.get("/login/oauth/gitea/callback", oauth_gitea_callback),
```

- [ ] **Step 4: Manual smoke test**

Start the server locally with OAuth configured in `~/.hb.yaml`:

```yaml
oauth:
  gitea:
    url: https://your-gitea-instance.example.com
    client_id: your-client-id
    client_secret: your-client-secret
```

Visit `http://localhost:50004/login/oauth/gitea` — confirm you are redirected to Gitea's authorization page.

- [ ] **Step 5: Commit**

```bash
git add hbd/server/http.py
git commit -m "feat: add Gitea OAuth2 redirect and callback routes"
```

---

## Task 6: Login page — "Sign in with Gitea" button

**Files:**
- Modify: `hbd/server/http.py` (update `login_page` handler, ~line 625)

- [ ] **Step 1: Replace the login page HTML**

In `hbd/server/http.py`, find the `html = f"""` block inside `login_page` and replace it with:

```python
        gitea_button = ""
        if oauth_mod.is_enabled(config):
            gitea_url = _gitea_cfg_url(config)
            gitea_button = f"""
    <div class="divider">or</div>
    <a href="/login/oauth/gitea" class="gitea-btn">
      Sign in with Gitea
    </a>"""

        html = f"""<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>Heartbeat — Login</title>
  <style>
    body {{ font-family: sans-serif; background: #f5f5f5; display: flex;
            justify-content: center; align-items: center; height: 100vh; margin: 0; }}
    .box {{ background: #fff; padding: 2em 2.5em; border-radius: 8px;
             box-shadow: 0 2px 12px rgba(0,0,0,.15); min-width: 300px; }}
    h2 {{ margin: 0 0 1.2em; color: #333; font-size: 1.4em; }}
    label {{ display: block; margin-bottom: .3em; font-size: .9em; color: #555; }}
    input {{ width: 100%; padding: .5em .7em; border: 1px solid #ccc;
              border-radius: 4px; font-size: 1em; box-sizing: border-box; }}
    button {{ margin-top: 1.2em; width: 100%; padding: .6em; background: #0066cc;
               color: #fff; border: none; border-radius: 4px; font-size: 1em; cursor: pointer; }}
    button:hover {{ background: #0055aa; }}
    .error {{ color: #c00; font-size: .9em; margin-bottom: .8em; }}
    .field {{ margin-bottom: .9em; }}
    .divider {{ text-align: center; margin: 1.2em 0 .8em; color: #999;
                font-size: .85em; border-top: 1px solid #eee; padding-top: .8em; }}
    .gitea-btn {{ display: block; width: 100%; padding: .6em; background: #609926;
                  color: #fff; border-radius: 4px; font-size: 1em; text-align: center;
                  text-decoration: none; box-sizing: border-box; }}
    .gitea-btn:hover {{ background: #4e7d1e; }}
  </style>
</head>
<body>
  <div class="box">
    <h2>Heartbeat</h2>
    {'<p class="error">Invalid username, password, or OAuth error.</p>' if error else ''}
    <form method="post">
      <div class="field"><label>Username</label><input name="username" autofocus></div>
      <div class="field"><label>Password</label><input name="password" type="password"></div>
      <button type="submit">Sign in</button>
    </form>{gitea_button}
  </div>
</body>
</html>"""
```

- [ ] **Step 2: Add the `_gitea_cfg_url` helper**

Add this small helper in `hbd/server/http.py` just before the `login_page` handler (around line 600) so the template can read the Gitea display URL without importing internal oauth details:

```python
def _gitea_cfg_url(config: dict) -> str:
    return config.get("oauth", {}).get("gitea", {}).get("url", "")
```

Also update the `login_page` handler's `error` logic to show the error when the `?error=1` query param is present (set by the callback on OAuth failure):

```python
    async def login_page(request):
        """GET /login — show login form; POST /login — process and redirect."""
        if not users_mod.users_enabled():
            raise web.HTTPFound("/")

        error = ""
        if request.method == "POST":
            form = await request.post()
            username = form.get("username", "")
            password = form.get("password", "")
            user = users_mod.authenticate(username, password)
            if user:
                token = users_mod.create_session(username)
                redirect_to = request.rel_url.query.get("next", "/")
                resp = web.HTTPFound(redirect_to)
                resp.set_cookie(
                    SESSION_COOKIE,
                    token,
                    max_age=users_mod.SESSION_TTL,
                    httponly=True,
                    samesite="Lax",
                )
                raise resp
            error = "Invalid username or password."
        elif request.rel_url.query.get("error"):
            error = "Sign-in failed. Please try again."
```

- [ ] **Step 3: Manual verification**

Start the server with OAuth configured. Visit `/login`. Confirm:
- The "Sign in with Gitea" button appears (green, below a divider)
- Clicking it redirects to Gitea
- After authorising on Gitea, you are redirected back and land on `/` with a valid session cookie

Without OAuth configured, confirm the button does not appear.

- [ ] **Step 4: Commit**

```bash
git add hbd/server/http.py
git commit -m "feat: add Sign in with Gitea button to login page"
```

---

## Self-Review Notes

- All 5 spec requirements covered: coexist ✓, auto-provision ✓, regular user ✓, any Gitea user ✓, config-driven ✓
- `exchange_code` signature in Task 4 matches usage in Task 5 (`config, code, redirect_uri`) ✓
- `fetch_user` returns `{login, full_name, avatar_url}` — matched in callback handler ✓
- `validate_state` removes state on use (replay protection) ✓
- `provision_oauth_user` skips empty strings so existing avatar/name aren't erased ✓
- `_gitea_cfg_url` is a plain `def`, not `async` — safe to call in template prep ✓