Security audit: fix IDOR, add rate limiting, HMAC auth, token hashing, XSS sanitization

Critical: Add ownership checks to all order routes (IDOR fix).
High: Redis rate limiting on auth endpoints, HMAC-signed internal
service calls replacing header-presence-only checks, nh3 HTML
sanitization on ghost_sync and product import, internal auth on
market API endpoints, SHA-256 hashed OAuth grant/code tokens.
Medium: SECRET_KEY production guard, AP signature enforcement,
is_admin param removal, cart_sid validation, SSRF protection on
remote actor fetch.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

account/alembic/versions/0002_hash_oauth_tokens.py

@@ -0,0 +1,86 @@
+"""Add token_hash columns to oauth_grants and oauth_codes
+
+Revision ID: acct_0002
+Revises: acct_0001
+Create Date: 2026-02-26
+"""
+
+import hashlib
+import sqlalchemy as sa
+from alembic import op
+
+revision = "acct_0002"
+down_revision = "acct_0001"
+branch_labels = None
+depends_on = None
+
+
+def _hash(token: str) -> str:
+    return hashlib.sha256(token.encode()).hexdigest()
+
+
+def upgrade():
+    # Add new hash columns
+    op.add_column("oauth_grants", sa.Column("token_hash", sa.String(64), nullable=True))
+    op.add_column("oauth_codes", sa.Column("code_hash", sa.String(64), nullable=True))
+    op.add_column("oauth_codes", sa.Column("grant_token_hash", sa.String(64), nullable=True))
+
+    # Backfill hashes from existing plaintext tokens
+    conn = op.get_bind()
+    grants = conn.execute(sa.text("SELECT id, token FROM oauth_grants WHERE token IS NOT NULL"))
+    for row in grants:
+        conn.execute(
+            sa.text("UPDATE oauth_grants SET token_hash = :h WHERE id = :id"),
+            {"h": _hash(row.token), "id": row.id},
+        )
+
+    codes = conn.execute(sa.text("SELECT id, code, grant_token FROM oauth_codes WHERE code IS NOT NULL"))
+    for row in codes:
+        params = {"id": row.id, "ch": _hash(row.code)}
+        params["gh"] = _hash(row.grant_token) if row.grant_token else None
+        conn.execute(
+            sa.text("UPDATE oauth_codes SET code_hash = :ch, grant_token_hash = :gh WHERE id = :id"),
+            params,
+        )
+
+    # Create unique indexes on hash columns
+    op.create_index("ix_oauth_grant_token_hash", "oauth_grants", ["token_hash"], unique=True)
+    op.create_index("ix_oauth_code_code_hash", "oauth_codes", ["code_hash"], unique=True)
+
+    # Make original token columns nullable (keep for rollback safety)
+    op.alter_column("oauth_grants", "token", nullable=True)
+    op.alter_column("oauth_codes", "code", nullable=True)
+
+    # Drop old unique indexes on plaintext columns
+    try:
+        op.drop_index("ix_oauth_grant_token", "oauth_grants")
+    except Exception:
+        pass
+    try:
+        op.drop_index("ix_oauth_code_code", "oauth_codes")
+    except Exception:
+        pass
+
+
+def downgrade():
+    # Restore original NOT NULL constraints
+    op.alter_column("oauth_grants", "token", nullable=False)
+    op.alter_column("oauth_codes", "code", nullable=False)
+
+    # Drop hash columns and indexes
+    try:
+        op.drop_index("ix_oauth_grant_token_hash", "oauth_grants")
+    except Exception:
+        pass
+    try:
+        op.drop_index("ix_oauth_code_code_hash", "oauth_codes")
+    except Exception:
+        pass
+
+    op.drop_column("oauth_grants", "token_hash")
+    op.drop_column("oauth_codes", "code_hash")
+    op.drop_column("oauth_codes", "grant_token_hash")
+
+    # Restore original unique indexes
+    op.create_index("ix_oauth_grant_token", "oauth_grants", ["token"], unique=True)
+    op.create_index("ix_oauth_code_code", "oauth_codes", ["code"], unique=True)

account/bp/actions/routes.py

@@ -17,6 +17,9 @@ def register() -> Blueprint:
     async def _require_action_header():
         if not request.headers.get(ACTION_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 

account/bp/auth/routes.py

@@ -26,9 +26,10 @@ from sqlalchemy.exc import SQLAlchemyError
 from shared.db.session import get_session
 from shared.models import User
 from shared.models.oauth_code import OAuthCode
-from shared.models.oauth_grant import OAuthGrant
+from shared.models.oauth_grant import OAuthGrant, hash_token
 from shared.infrastructure.urls import account_url, app_url
 from shared.infrastructure.cart_identity import current_cart_identity
+from shared.infrastructure.rate_limit import rate_limit, check_poll_backoff
 from shared.events import emit_activity
 
 from .services import (
@@ -98,7 +99,8 @@ def register(url_prefix="/auth"):
         async with get_session() as s:
             async with s.begin():
                 grant = OAuthGrant(
-                    token=grant_token,
+                    token=None,
+                    token_hash=hash_token(grant_token),
                     user_id=g.user.id,
                     client_id=client_id,
                     issuer_session=account_sid,
@@ -107,12 +109,14 @@ def register(url_prefix="/auth"):
                 s.add(grant)
 
                 oauth_code = OAuthCode(
-                    code=code,
+                    code=None,
+                    code_hash=hash_token(code),
                     user_id=g.user.id,
                     client_id=client_id,
                     redirect_uri=redirect_uri,
                     expires_at=expires,
-                    grant_token=grant_token,
+                    grant_token=None,
+                    grant_token_hash=hash_token(grant_token),
                 )
                 s.add(oauth_code)
 
@@ -149,11 +153,15 @@ def register(url_prefix="/auth"):
 
         now = datetime.now(timezone.utc)
 
+        code_h = hash_token(code)
         async with get_session() as s:
             async with s.begin():
+                # Look up by hash first (new grants), fall back to plaintext (migration)
                 result = await s.execute(
                     select(OAuthCode)
-                    .where(OAuthCode.code == code)
+                    .where(
+                        (OAuthCode.code_hash == code_h) | (OAuthCode.code == code)
+                    )
                     .with_for_update()
                 )
                 oauth_code = result.scalar_one_or_none()
@@ -197,9 +205,12 @@ def register(url_prefix="/auth"):
         if not token:
             return jsonify({"valid": False}), 200
 
+        token_h = hash_token(token)
         async with get_session() as s:
             grant = await s.scalar(
-                select(OAuthGrant).where(OAuthGrant.token == token)
+                select(OAuthGrant).where(
+                    (OAuthGrant.token_hash == token_h) | (OAuthGrant.token == token)
+                )
             )
             if not grant or grant.revoked_at is not None:
                 return jsonify({"valid": False}), 200
@@ -257,12 +268,19 @@ def register(url_prefix="/auth"):
         store_login_redirect_target()
         cross_cart_sid = request.args.get("cart_sid")
         if cross_cart_sid:
+            import re
+            # Validate cart_sid is a hex token (32 chars from token_hex(16))
+            if re.fullmatch(r"[0-9a-f]{32}", cross_cart_sid):
                 qsession["cart_sid"] = cross_cart_sid
         if g.get("user"):
             redirect_url = pop_login_redirect_target()
             return redirect(redirect_url)
         return await render_template("auth/login.html")
 
+    @rate_limit(
+        key_func=lambda: request.headers.get("X-Forwarded-For", request.remote_addr),
+        max_requests=10, window_seconds=900, scope="magic_ip",
+    )
     @auth_bp.post("/start/")
     async def start_login():
         form = await request.form
@@ -279,6 +297,22 @@ def register(url_prefix="/auth"):
                 400,
             )
 
+        # Per-email rate limit: 5 magic links per 15 minutes
+        from shared.infrastructure.rate_limit import _check_rate_limit
+        try:
+            allowed, _ = await _check_rate_limit(f"magic_email:{email}", 5, 900)
+            if not allowed:
+                return (
+                    await render_template(
+                        "auth/check_email.html",
+                        email=email,
+                        email_error=None,
+                    ),
+                    200,
+                )
+        except Exception:
+            pass  # Redis down — allow the request
+
         user = await find_or_create_user(g.s, email)
         token, expires = await create_magic_link(g.s, user.id)
 
@@ -521,7 +555,8 @@ def register(url_prefix="/auth"):
         async with get_session() as s:
             async with s.begin():
                 grant = OAuthGrant(
-                    token=grant_token,
+                    token=None,
+                    token_hash=hash_token(grant_token),
                     user_id=user.id,
                     client_id=blob["client_id"],
                     issuer_session=account_sid,
@@ -546,6 +581,10 @@ def register(url_prefix="/auth"):
 
         return True
 
+    @rate_limit(
+        key_func=lambda: request.headers.get("X-Forwarded-For", request.remote_addr),
+        max_requests=10, window_seconds=3600, scope="dev_auth",
+    )
     @csrf_exempt
     @auth_bp.post("/device/authorize")
     @auth_bp.post("/device/authorize/")
@@ -600,6 +639,14 @@ def register(url_prefix="/auth"):
         if not device_code or client_id not in ALLOWED_CLIENTS:
             return jsonify({"error": "invalid_request"}), 400
 
+        # Enforce polling backoff per RFC 8628
+        try:
+            poll_ok, interval = await check_poll_backoff(device_code)
+            if not poll_ok:
+                return jsonify({"error": "slow_down", "interval": interval}), 400
+        except Exception:
+            pass  # Redis down — allow the request
+
         from shared.infrastructure.auth_redis import get_auth_redis
 
         r = await get_auth_redis()

account/bp/data/routes.py

@@ -19,6 +19,9 @@ def register() -> Blueprint:
     async def _require_data_header():
         if not request.headers.get(DATA_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 

blog/bp/actions/routes.py

@@ -17,6 +17,9 @@ def register() -> Blueprint:
     async def _require_action_header():
         if not request.headers.get(ACTION_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 

blog/bp/blog/ghost/ghost_sync.py

@@ -15,6 +15,7 @@ from html import escape as html_escape
 from typing import Dict, Any, Optional
 
 import httpx
+import nh3
 from sqlalchemy import select, delete
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -29,6 +30,35 @@ GHOST_ADMIN_API_URL = os.environ["GHOST_ADMIN_API_URL"]
 from shared.browser.app.utils import utcnow
 
 
+def _sanitize_html(html: str | None) -> str | None:
+    """Sanitize HTML content using nh3, allowing safe formatting tags."""
+    if not html:
+        return html
+    return nh3.clean(
+        html,
+        tags={
+            "a", "abbr", "acronym", "b", "blockquote", "br", "code",
+            "div", "em", "figcaption", "figure", "h1", "h2", "h3",
+            "h4", "h5", "h6", "hr", "i", "img", "li", "ol", "p",
+            "pre", "span", "strong", "sub", "sup", "table", "tbody",
+            "td", "th", "thead", "tr", "ul", "video", "source",
+            "picture", "iframe", "audio",
+        },
+        attributes={
+            "*": {"class", "id", "style"},
+            "a": {"href", "title", "target", "rel"},
+            "img": {"src", "alt", "title", "width", "height", "loading"},
+            "video": {"src", "controls", "width", "height", "poster"},
+            "audio": {"src", "controls"},
+            "source": {"src", "type"},
+            "iframe": {"src", "width", "height", "frameborder", "allowfullscreen"},
+            "td": {"colspan", "rowspan"},
+            "th": {"colspan", "rowspan"},
+        },
+        url_schemes={"http", "https", "mailto"},
+    )
+
+
 def _auth_header() -> dict[str, str]:
     return {"Authorization": f"Ghost {make_ghost_admin_jwt()}"}
 
@@ -99,13 +129,13 @@ def _apply_ghost_fields(obj: Post, gp: Dict[str, Any], author_map: Dict[str, Aut
     obj.uuid = gp.get("uuid") or obj.uuid
     obj.slug = gp.get("slug") or obj.slug
     obj.title = gp.get("title") or obj.title
-    obj.html = gp.get("html")
+    obj.html = _sanitize_html(gp.get("html"))
     obj.plaintext = gp.get("plaintext")
     obj.mobiledoc = gp.get("mobiledoc")
     obj.lexical = gp.get("lexical")
     obj.feature_image = gp.get("feature_image")
     obj.feature_image_alt = gp.get("feature_image_alt")
-    obj.feature_image_caption = gp.get("feature_image_caption")
+    obj.feature_image_caption = _sanitize_html(gp.get("feature_image_caption"))
     obj.excerpt = gp.get("excerpt")
     obj.custom_excerpt = gp.get("custom_excerpt")
     obj.visibility = gp.get("visibility") or obj.visibility

blog/bp/data/routes.py

@@ -35,6 +35,9 @@ def register() -> Blueprint:
     async def _require_data_header():
         if not request.headers.get(DATA_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 

cart/bp/actions/routes.py

@@ -18,6 +18,9 @@ def register() -> Blueprint:
     async def _require_action_header():
         if not request.headers.get(ACTION_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 

cart/bp/data/routes.py

@@ -19,6 +19,9 @@ def register() -> Blueprint:
     async def _require_data_header():
         if not request.headers.get(DATA_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 

cart/bp/order/routes.py

@@ -11,12 +11,23 @@ from shared.browser.app.payments.sumup import create_checkout as sumup_create_ch
 from shared.config import config
 
 from shared.infrastructure.http_utils import vary as _vary, current_url_without_page as _current_url_without_page
+from shared.infrastructure.cart_identity import current_cart_identity
 from bp.cart.services import check_sumup_status
 from shared.browser.app.utils.htmx import is_htmx_request
 
 from .filters.qs import makeqs_factory, decode
 
 
+def _owner_filter():
+    """Return SQLAlchemy clause restricting orders to current user/session."""
+    ident = current_cart_identity()
+    if ident["user_id"]:
+        return Order.user_id == ident["user_id"]
+    if ident["session_id"]:
+        return Order.session_id == ident["session_id"]
+    return None
+
+
 def register() -> Blueprint:
     bp = Blueprint("order", __name__, url_prefix='/<int:order_id>')
 
@@ -32,12 +43,15 @@ def register() -> Blueprint:
         """
         Show a single order + items.
         """
+        owner = _owner_filter()
+        if owner is None:
+            return await make_response("Order not found", 404)
         result = await g.s.execute(
             select(Order)
             .options(
                 selectinload(Order.items).selectinload(OrderItem.product)
             )
-            .where(Order.id == order_id)
+            .where(Order.id == order_id, owner)
         )
         order = result.scalar_one_or_none()
         if not order:
@@ -58,7 +72,10 @@ def register() -> Blueprint:
         If already paid, just go back to the order detail.
         If not, (re)create a SumUp checkout and redirect.
         """
-        result = await g.s.execute(select(Order).where(Order.id == order_id))
+        owner = _owner_filter()
+        if owner is None:
+            return await make_response("Order not found", 404)
+        result = await g.s.execute(select(Order).where(Order.id == order_id, owner))
         order = result.scalar_one_or_none()
         if not order:
             return await make_response("Order not found", 404)
@@ -115,7 +132,10 @@ def register() -> Blueprint:
         Manually re-check this order's status with SumUp.
         Useful if the webhook hasn't fired or the user didn't return correctly.
         """
-        result = await g.s.execute(select(Order).where(Order.id == order_id))
+        owner = _owner_filter()
+        if owner is None:
+            return await make_response("Order not found", 404)
+        result = await g.s.execute(select(Order).where(Order.id == order_id, owner))
         order = result.scalar_one_or_none()
         if not order:
             return await make_response("Order not found", 404)

cart/bp/orders/routes.py

@@ -11,6 +11,7 @@ from shared.browser.app.payments.sumup import create_checkout as sumup_create_ch
 from shared.config import config
 
 from shared.infrastructure.http_utils import vary as _vary, current_url_without_page as _current_url_without_page
+from shared.infrastructure.cart_identity import current_cart_identity
 from bp.cart.services import check_sumup_status
 from shared.browser.app.utils.htmx import is_htmx_request
 from bp import register_order
@@ -42,9 +43,25 @@ def register(url_prefix: str) -> Blueprint:
         # this is the crucial bit for the |qs filter
         g.makeqs_factory = makeqs_factory
 
+    @bp.before_request
+    async def _require_identity():
+        """Orders require a logged-in user or at least a cart session."""
+        ident = current_cart_identity()
+        if not ident["user_id"] and not ident["session_id"]:
+            return redirect(url_for("auth.login_form"))
+
     @bp.get("/")
     async def list_orders():
 
+        # --- ownership: only show orders belonging to current user/session ---
+        ident = current_cart_identity()
+        if ident["user_id"]:
+            owner_clause = Order.user_id == ident["user_id"]
+        elif ident["session_id"]:
+            owner_clause = Order.session_id == ident["session_id"]
+        else:
+            return redirect(url_for("auth.login_form"))
+
         # --- decode filters from query string (page + search) ---
         q = decode()
         page, search = q.page, q.search
@@ -97,8 +114,8 @@ def register(url_prefix: str) -> Blueprint:
 
             where_clause = or_(*conditions)
 
-        # --- total count & total pages (respecting search) ---
-        count_stmt = select(func.count()).select_from(Order)
+        # --- total count & total pages (respecting search + ownership) ---
+        count_stmt = select(func.count()).select_from(Order).where(owner_clause)
         if where_clause is not None:
             count_stmt = count_stmt.where(where_clause)
 
@@ -110,10 +127,11 @@ def register(url_prefix: str) -> Blueprint:
         if page > total_pages:
             page = total_pages
 
-        # --- paginated orders (respecting search) ---
+        # --- paginated orders (respecting search + ownership) ---
         offset = (page - 1) * ORDERS_PER_PAGE
         stmt = (
             select(Order)
+            .where(owner_clause)
             .order_by(Order.created_at.desc())
             .offset(offset)
             .limit(ORDERS_PER_PAGE)

events/bp/actions/routes.py

@@ -18,6 +18,9 @@ def register() -> Blueprint:
     async def _require_action_header():
         if not request.headers.get(ACTION_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 

events/bp/data/routes.py

@@ -19,6 +19,9 @@ def register() -> Blueprint:
     async def _require_data_header():
         if not request.headers.get(DATA_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 
@@ -131,8 +134,9 @@ def register() -> Blueprint:
         period_start = datetime.fromisoformat(request.args.get("period_start", ""))
         period_end = datetime.fromisoformat(request.args.get("period_end", ""))
         user_id = request.args.get("user_id", type=int)
-        is_admin = request.args.get("is_admin", "false").lower() == "true"
         session_id = request.args.get("session_id")
+        # is_admin determined server-side, never from client params
+        is_admin = False
         entries = await services.calendar.visible_entries_for_period(
             g.s, calendar_id, period_start, period_end,
             user_id=user_id, is_admin=is_admin, session_id=session_id,

market/bp/actions/routes.py

@@ -18,6 +18,9 @@ def register() -> Blueprint:
     async def _require_action_header():
         if not request.headers.get(ACTION_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 

market/bp/api/routes.py

@@ -5,6 +5,7 @@ from datetime import datetime, timezone
 from decimal import Decimal
 from typing import Any, Dict, List, Tuple, Iterable, Optional
 
+import nh3
 from quart import Blueprint, request, jsonify, g
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -29,10 +30,18 @@ from models.market import (
 
 from shared.browser.app.redis_cacher import clear_cache
 from shared.browser.app.csrf import csrf_exempt
+from shared.infrastructure.internal_auth import validate_internal_request
 
 
 products_api = Blueprint("products_api", __name__, url_prefix="/api/products")
 
+
+@products_api.before_request
+async def _require_internal_auth():
+    """All product API endpoints require HMAC-signed internal requests."""
+    if not validate_internal_request():
+        return jsonify({"error": "forbidden"}), 403
+
 # ---- Comparison config (matches your schema) --------------------------------
 
 PRODUCT_FIELDS: List[str] = [
@@ -219,9 +228,35 @@ def _deep_equal(a: Dict[str, Any], b: Dict[str, Any]) -> bool:
 
 # ---- Mutation helpers -------------------------------------------------------
 
+_PRODUCT_HTML_FIELDS = {"description_html"}
+
+_SANITIZE_TAGS = {
+    "a", "b", "blockquote", "br", "code", "div", "em", "h1", "h2", "h3",
+    "h4", "h5", "h6", "hr", "i", "img", "li", "ol", "p", "pre", "span",
+    "strong", "sub", "sup", "table", "tbody", "td", "th", "thead", "tr",
+    "ul", "figure", "figcaption",
+}
+_SANITIZE_ATTRS = {
+    "*": {"class", "id"},
+    "a": {"href", "title", "target", "rel"},
+    "img": {"src", "alt", "title", "width", "height", "loading"},
+    "td": {"colspan", "rowspan"},
+    "th": {"colspan", "rowspan"},
+}
+
+
+def _sanitize_product_html(value: Any) -> Any:
+    if isinstance(value, str) and value:
+        return nh3.clean(value, tags=_SANITIZE_TAGS, attributes=_SANITIZE_ATTRS)
+    return value
+
+
 def _apply_product_fields(p: Product, payload: Dict[str, Any]) -> None:
     for f in PRODUCT_FIELDS:
-        setattr(p, f, payload.get(f))
+        val = payload.get(f)
+        if f in _PRODUCT_HTML_FIELDS:
+            val = _sanitize_product_html(val)
+        setattr(p, f, val)
     p.updated_at = _now_utc()
 
 def _replace_children(p: Product, payload: Dict[str, Any]) -> None:
@@ -239,7 +274,7 @@ def _replace_children(p: Product, payload: Dict[str, Any]) -> None:
     for row in payload.get("sections") or []:
         p.sections.append(ProductSection(
             title=row.get("title") or "",
-            html=row.get("html") or "",
+            html=_sanitize_product_html(row.get("html") or ""),
             created_at=_now_utc(), updated_at=_now_utc(),
         ))
 

market/bp/data/routes.py

@@ -19,6 +19,9 @@ def register() -> Blueprint:
     async def _require_data_header():
         if not request.headers.get(DATA_HEADER):
             return jsonify({"error": "forbidden"}), 403
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if not validate_internal_request():
+            return jsonify({"error": "forbidden"}), 403
 
     _handlers: dict[str, object] = {}
 

shared/browser/app/csrf.py

@@ -57,10 +57,13 @@ async def protect() -> None:
     if _is_exempt_endpoint():
         return
 
-    # Internal service-to-service calls are already gated by header checks
-    # and only reachable on the Docker overlay network.
+    # Internal service-to-service calls — validate HMAC signature
     if request.headers.get("X-Internal-Action") or request.headers.get("X-Internal-Data"):
+        from shared.infrastructure.internal_auth import validate_internal_request
+        if validate_internal_request():
             return
+        # Reject unsigned internal requests
+        abort(403, "Invalid internal request signature")
 
     session_token = qsession.get("csrf_token")
     if not session_token:

shared/infrastructure/actions.py

@@ -13,6 +13,8 @@ import os
 
 import httpx
 
+from shared.infrastructure.internal_auth import sign_internal_headers
+
 log = logging.getLogger(__name__)
 
 # Re-usable async client (created lazily, one per process)
@@ -65,10 +67,11 @@ async def call_action(
     base = _internal_url(app_name)
     url = f"{base}/internal/actions/{action_name}"
     try:
+        headers = {ACTION_HEADER: "1", **sign_internal_headers(app_name)}
         resp = await _get_client().post(
             url,
             json=payload or {},
-            headers={ACTION_HEADER: "1"},
+            headers=headers,
             timeout=timeout,
         )
         if 200 <= resp.status_code < 300:

shared/infrastructure/activitypub.py

@@ -328,9 +328,10 @@ def create_activitypub_blueprint(app_name: str) -> Blueprint:
 
         if not sig_valid:
             log.warning(
-                "Unverified inbox POST from %s (%s) on %s — accepting anyway for now",
+                "Unverified inbox POST from %s (%s) on %s — rejecting",
                 from_actor_url, activity_type, domain,
             )
+            abort(401, "Invalid or missing HTTP signature")
 
         # Load actor row for DB operations
         actor_row = (

shared/infrastructure/ap_inbox_handlers.py

@@ -29,8 +29,43 @@ AP_CONTENT_TYPE = "application/activity+json"
 # Helpers
 # ---------------------------------------------------------------------------
 
+def _is_safe_url(url: str) -> bool:
+    """Reject URLs pointing to private/internal IPs to prevent SSRF."""
+    from urllib.parse import urlparse
+    import ipaddress
+
+    parsed = urlparse(url)
+
+    # Require HTTPS
+    if parsed.scheme != "https":
+        return False
+
+    hostname = parsed.hostname
+    if not hostname:
+        return False
+
+    # Block obvious internal hostnames
+    if hostname in ("localhost", "127.0.0.1", "::1", "0.0.0.0"):
+        return False
+
+    try:
+        addr = ipaddress.ip_address(hostname)
+        if addr.is_private or addr.is_loopback or addr.is_reserved or addr.is_link_local:
+            return False
+    except ValueError:
+        # Not an IP literal — hostname is fine (DNS resolution handled by httpx)
+        # Block common internal DNS patterns
+        if hostname.endswith(".internal") or hostname.endswith(".local"):
+            return False
+
+    return True
+
+
 async def fetch_remote_actor(actor_url: str) -> dict | None:
     """Fetch a remote actor's JSON-LD profile."""
+    if not _is_safe_url(actor_url):
+        log.warning("Blocked SSRF attempt: %s", actor_url)
+        return None
     try:
         async with httpx.AsyncClient(timeout=10) as client:
             resp = await client.get(

shared/infrastructure/data_client.py

@@ -13,6 +13,8 @@ import os
 
 import httpx
 
+from shared.infrastructure.internal_auth import sign_internal_headers
+
 log = logging.getLogger(__name__)
 
 # Re-usable async client (created lazily, one per process)
@@ -66,10 +68,11 @@ async def fetch_data(
     base = _internal_url(app_name)
     url = f"{base}/internal/data/{query_name}"
     try:
+        headers = {DATA_HEADER: "1", **sign_internal_headers(app_name)}
         resp = await _get_client().get(
             url,
             params=params,
-            headers={DATA_HEADER: "1"},
+            headers=headers,
             timeout=timeout,
         )
         if resp.status_code == 200:

shared/infrastructure/factory.py

@@ -77,7 +77,13 @@ def create_base_app(
 
     configure_logging(name)
 
-    app.secret_key = os.getenv("SECRET_KEY", "dev-secret-key-change-me-777")
+    secret_key = os.getenv("SECRET_KEY")
+    if not secret_key:
+        env = os.getenv("ENVIRONMENT", "development")
+        if env in ("production", "staging"):
+            raise RuntimeError("SECRET_KEY environment variable must be set in production")
+        secret_key = "dev-secret-key-change-me-777"
+    app.secret_key = secret_key
 
     # Per-app first-party session cookie (no shared domain — avoids Safari ITP)
     app.config["SESSION_COOKIE_NAME"] = f"{name}_session"
@@ -192,11 +198,14 @@ def create_base_app(
 
                 from sqlalchemy import select
                 from shared.db.session import get_account_session
-                from shared.models.oauth_grant import OAuthGrant
+                from shared.models.oauth_grant import OAuthGrant, hash_token
                 try:
+                    token_h = hash_token(grant_token)
                     async with get_account_session() as s:
                         grant = await s.scalar(
-                            select(OAuthGrant).where(OAuthGrant.token == grant_token)
+                            select(OAuthGrant).where(
+                                (OAuthGrant.token_hash == token_h) | (OAuthGrant.token == grant_token)
+                            )
                         )
                         valid = grant is not None and grant.revoked_at is None
                 except Exception:

shared/infrastructure/internal_auth.py

@@ -0,0 +1,92 @@
+"""HMAC-based authentication for internal service-to-service calls.
+
+Replaces the previous header-presence-only check with a signed token
+that includes a timestamp to prevent replay attacks.
+
+Signing side (data_client.py / actions.py)::
+
+    from shared.infrastructure.internal_auth import sign_internal_headers
+    headers = sign_internal_headers("cart")
+
+Validation side (before_request guards, csrf.py)::
+
+    from shared.infrastructure.internal_auth import validate_internal_request
+    if not validate_internal_request():
+        abort(403)
+"""
+from __future__ import annotations
+
+import hashlib
+import hmac
+import os
+import time
+
+from quart import request
+
+# Shared secret — MUST be set in production
+_SECRET = os.getenv("INTERNAL_HMAC_SECRET", "").encode() or os.getenv("SECRET_KEY", "").encode()
+
+# Maximum age of a signed request (seconds)
+_MAX_AGE = 300  # 5 minutes
+
+
+def _get_secret() -> bytes:
+    return _SECRET or os.getenv("SECRET_KEY", "dev-secret-key-change-me-777").encode()
+
+
+def sign_internal_headers(app_name: str) -> dict[str, str]:
+    """Generate signed headers for an internal request.
+
+    Returns a dict of headers to include in the request.
+    """
+    ts = str(int(time.time()))
+    payload = f"{ts}:{app_name}".encode()
+    sig = hmac.new(_get_secret(), payload, hashlib.sha256).hexdigest()
+    return {
+        "X-Internal-Timestamp": ts,
+        "X-Internal-App": app_name,
+        "X-Internal-Signature": sig,
+    }
+
+
+def validate_internal_request() -> bool:
+    """Validate that an incoming request has a valid HMAC signature.
+
+    Checks X-Internal-Timestamp, X-Internal-App, and X-Internal-Signature
+    headers. Returns True if valid, False otherwise.
+    """
+    ts = request.headers.get("X-Internal-Timestamp", "")
+    app_name = request.headers.get("X-Internal-App", "")
+    sig = request.headers.get("X-Internal-Signature", "")
+
+    if not ts or not app_name or not sig:
+        return False
+
+    # Check timestamp freshness
+    try:
+        req_time = int(ts)
+    except (ValueError, TypeError):
+        return False
+
+    now = int(time.time())
+    if abs(now - req_time) > _MAX_AGE:
+        return False
+
+    # Verify signature
+    payload = f"{ts}:{app_name}".encode()
+    expected = hmac.new(_get_secret(), payload, hashlib.sha256).hexdigest()
+    return hmac.compare_digest(sig, expected)
+
+
+def is_internal_request() -> bool:
+    """Check if the current request is a signed internal request.
+
+    This is a convenience that checks for any of the internal headers
+    (legacy or new HMAC-signed).
+    """
+    # New HMAC-signed headers
+    if request.headers.get("X-Internal-Signature"):
+        return validate_internal_request()
+    # Legacy: presence-only headers (still accepted during migration,
+    # but callers should be updated to use signed headers)
+    return False

shared/infrastructure/rate_limit.py

@@ -0,0 +1,142 @@
+"""Redis-based rate limiter for auth endpoints.
+
+Provides a decorator that enforces per-key rate limits using a sliding
+window counter stored in Redis (auth DB 15).
+
+Usage::
+
+    from shared.infrastructure.rate_limit import rate_limit
+
+    @rate_limit(key_func=lambda: request.form.get("email", "").lower(),
+                max_requests=5, window_seconds=900, scope="magic_link")
+    @bp.post("/start/")
+    async def start_login():
+        ...
+"""
+from __future__ import annotations
+
+import functools
+import time
+
+from quart import request, jsonify, make_response
+
+
+async def _check_rate_limit(
+    key: str,
+    max_requests: int,
+    window_seconds: int,
+) -> tuple[bool, int]:
+    """Check and increment rate limit counter.
+
+    Returns (allowed, remaining).
+    """
+    from shared.infrastructure.auth_redis import get_auth_redis
+
+    r = await get_auth_redis()
+    now = time.time()
+    window_start = now - window_seconds
+    redis_key = f"rl:{key}"
+
+    pipe = r.pipeline()
+    # Remove expired entries
+    pipe.zremrangebyscore(redis_key, 0, window_start)
+    # Add current request
+    pipe.zadd(redis_key, {str(now).encode(): now})
+    # Count entries in window
+    pipe.zcard(redis_key)
+    # Set TTL so key auto-expires
+    pipe.expire(redis_key, window_seconds)
+    results = await pipe.execute()
+
+    count = results[2]
+    allowed = count <= max_requests
+    remaining = max(0, max_requests - count)
+
+    return allowed, remaining
+
+
+def rate_limit(
+    *,
+    key_func,
+    max_requests: int,
+    window_seconds: int,
+    scope: str,
+):
+    """Decorator that rate-limits a Quart route.
+
+    Parameters
+    ----------
+    key_func:
+        Callable returning the rate-limit key (e.g. email, IP).
+        Called inside request context.
+    max_requests:
+        Maximum number of requests allowed in the window.
+    window_seconds:
+        Sliding window duration in seconds.
+    scope:
+        Namespace prefix for the Redis key (e.g. "magic_link").
+    """
+    def decorator(fn):
+        @functools.wraps(fn)
+        async def wrapper(*args, **kwargs):
+            raw_key = key_func()
+            if not raw_key:
+                return await fn(*args, **kwargs)
+
+            full_key = f"{scope}:{raw_key}"
+            try:
+                allowed, remaining = await _check_rate_limit(
+                    full_key, max_requests, window_seconds,
+                )
+            except Exception:
+                # If Redis is down, allow the request
+                return await fn(*args, **kwargs)
+
+            if not allowed:
+                resp = await make_response(
+                    jsonify({"error": "rate_limited", "retry_after": window_seconds}),
+                    429,
+                )
+                resp.headers["Retry-After"] = str(window_seconds)
+                return resp
+
+            return await fn(*args, **kwargs)
+        return wrapper
+    return decorator
+
+
+async def check_poll_backoff(device_code: str) -> tuple[bool, int]:
+    """Enforce exponential backoff on device token polling.
+
+    Returns (allowed, interval) where interval is the recommended
+    poll interval in seconds. If not allowed, caller should return
+    a 'slow_down' error per RFC 8628.
+    """
+    from shared.infrastructure.auth_redis import get_auth_redis
+
+    r = await get_auth_redis()
+    key = f"rl:devpoll:{device_code}"
+    now = time.time()
+
+    raw = await r.get(key)
+    if raw:
+        data = raw.decode() if isinstance(raw, bytes) else raw
+        parts = data.split(":")
+        last_poll = float(parts[0])
+        interval = int(parts[1])
+
+        elapsed = now - last_poll
+        if elapsed < interval:
+            # Too fast — increase interval
+            new_interval = min(interval + 5, 60)
+            await r.set(key, f"{now}:{new_interval}".encode(), ex=900)
+            return False, new_interval
+
+        # Acceptable pace — keep current interval
+        await r.set(key, f"{now}:{interval}".encode(), ex=900)
+        return True, interval
+
+    # First poll
+    initial_interval = 5
+    await r.set(key, f"{now}:{initial_interval}".encode(), ex=900)
+    return True, initial_interval

shared/models/oauth_code.py

@@ -1,4 +1,5 @@
 from __future__ import annotations
+import hashlib
 from datetime import datetime
 from sqlalchemy import String, Integer, DateTime, ForeignKey, func, Index
 from sqlalchemy.orm import Mapped, mapped_column, relationship
@@ -6,21 +7,28 @@ from shared.db.base import Base
 
 
 class OAuthCode(Base):
+    """Short-lived authorization code issued during OAuth flow.
+
+    The ``code`` column is retained during migration but new codes store
+    only ``code_hash``.  Lookups should use ``code_hash``.
+    """
     __tablename__ = "oauth_codes"
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
-    code: Mapped[str] = mapped_column(String(128), unique=True, index=True, nullable=False)
+    code: Mapped[str | None] = mapped_column(String(128), nullable=True)
+    code_hash: Mapped[str | None] = mapped_column(String(64), unique=True, nullable=True, index=True)
     user_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
     client_id: Mapped[str] = mapped_column(String(64), nullable=False)
     redirect_uri: Mapped[str] = mapped_column(String(512), nullable=False)
     expires_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
     used_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
     grant_token: Mapped[str | None] = mapped_column(String(128), nullable=True)
+    grant_token_hash: Mapped[str | None] = mapped_column(String(64), nullable=True)
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False, server_default=func.now())
 
     user = relationship("User", backref="oauth_codes")
 
     __table_args__ = (
-        Index("ix_oauth_code_code", "code", unique=True),
+        Index("ix_oauth_code_code_hash", "code_hash", unique=True),
         Index("ix_oauth_code_user", "user_id"),
     )

shared/models/oauth_grant.py

@@ -1,21 +1,31 @@
 from __future__ import annotations
+import hashlib
 from datetime import datetime
 from sqlalchemy import String, Integer, DateTime, ForeignKey, func, Index
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 from shared.db.base import Base
 
 
+def hash_token(token: str) -> str:
+    """SHA-256 hash a token for secure DB storage."""
+    return hashlib.sha256(token.encode()).hexdigest()
+
+
 class OAuthGrant(Base):
     """Long-lived grant tracking each client-app session authorization.
 
     Created when the OAuth authorize endpoint issues a code.  Tied to the
     account session that issued it (``issuer_session``) so that logging out
     on one device revokes only that device's grants.
+
+    The ``token`` column is retained during migration but new grants store
+    only ``token_hash``.  Lookups should use ``token_hash``.
     """
     __tablename__ = "oauth_grants"
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
-    token: Mapped[str] = mapped_column(String(128), unique=True, nullable=False)
+    token: Mapped[str | None] = mapped_column(String(128), nullable=True)
+    token_hash: Mapped[str | None] = mapped_column(String(64), unique=True, nullable=True, index=True)
     user_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
     client_id: Mapped[str] = mapped_column(String(64), nullable=False)
     issuer_session: Mapped[str] = mapped_column(String(128), nullable=False, index=True)
@@ -26,7 +36,7 @@ class OAuthGrant(Base):
     user = relationship("User", backref="oauth_grants")
 
     __table_args__ = (
-        Index("ix_oauth_grant_token", "token", unique=True),
+        Index("ix_oauth_grant_token_hash", "token_hash", unique=True),
         Index("ix_oauth_grant_issuer", "issuer_session"),
         Index("ix_oauth_grant_device", "device_id", "client_id"),
     )

shared/requirements.txt

@@ -44,6 +44,7 @@ Werkzeug==3.1.3
 wsproto==1.2.0
 zstandard==0.25.0
 redis>=5.0
+nh3>=0.2.14
 mistune>=3.0
 pytest>=8.0
 pytest-asyncio>=0.23