authentication: added logout ability

sachet/server/models.py

@@ -33,50 +33,97 @@ class User(db.Model):
             algorithm="HS256"
         )
 
-def _token_decorator(require_admin, f, *args, **kwargs):
-    """Generic function for checking tokens.
 
-    require_admin: require user to be administrator to authenticate
+class BlacklistToken(db.Model):
+    """Token that has been revoked (but has not expired yet.)
+
+    This is needed to perform functionality like logging out.
     """
-    token = None
-    auth_header = request.headers.get("Authorization")
-    if auth_header:
-        try:
-            token = auth_header.split(" ")[1]
-        except IndexError:
-            resp = {
-                "status": "fail",
-                "message": "Malformed Authorization header."
-            }
-            return jsonify(resp), 401
 
-    if not token:
-        return jsonify({"status": "fail", "message": "Missing auth token"}), 401
-    try:
-        data = jwt.decode(token, app.config["SECRET_KEY"], algorithms=["HS256"])
-        user = User.query.filter_by(username=data.get("sub")).first()
-    except:
-        return jsonify({"status": "fail", "message": "Invalid auth token."}), 401
+    __tablename__ = "blacklist_tokens"
+    
+    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
+    token = db.Column(db.String(500), unique=True,  nullable=False)
+    expires = db.Column(db.DateTime, nullable=False)
 
+    def __init__(self, token):
+        self.token = token
+
+        data = jwt.decode(
+            token,
+            app.config["SECRET_KEY"],
+            algorithms=["HS256"],
+        )
+        self.expires = datetime.datetime.fromtimestamp(data["exp"])
+
+    @staticmethod
+    def check_blacklist(token):
+        """Returns if a token is blacklisted."""
+        entry = BlacklistToken.query.filter_by(token=token).first()
+
+        if not entry:
+            return False
+        else:
+            if entry.expires < datetime.datetime.utcnow():
+                db.session.delete(entry)
+            return True
+
+
+def read_token(token):
+    """Read a JWT and validate it.
+
+    Returns a tuple: dictionary of the JWT's data, and the corresponding user
+    if available.
+    """
+
+    data = jwt.decode(
+        token,
+        app.config["SECRET_KEY"],
+        algorithms=["HS256"],
+    )
+
+    if BlacklistToken.check_blacklist(token):
+        raise jwt.ExpiredSignatureError("Token revoked.")
+
+    user = User.query.filter_by(username=data.get("sub")).first()
     if not user:
-        return jsonify({"status": "fail", "message": "Invalid auth token."}), 401
+        raise jwt.InvalidTokenError("No user corresponds to this token.")
 
-    if require_admin and not user.admin:
-        return jsonify({"status": "fail", "message": "You are not authorized to view this page."}), 403
+    return data, user
 
-    return f(user, *args, **kwargs)
 
-def token_required(f):
-    """Decorator to require authentication."""
+def auth_required(f):
+    """Decorator to require authentication.
+
+    Passes an argument 'user' to the function, with a User object corresponding
+    to the authenticated session.
+    """
     @wraps(f)
     def decorator(*args, **kwargs):
-        return _token_decorator(False, f, *args, **kwargs)
-    return decorator
+        token = None
+        auth_header = request.headers.get("Authorization")
+        if auth_header:
+            try:
+                token = auth_header.split(" ")[1]
+            except IndexError:
+                resp = {
+                    "status": "fail",
+                    "message": "Malformed Authorization header."
+                }
+                return jsonify(resp), 401
 
-def admin_required(f):
-    """Decorator to require authentication and admin privileges."""
+        if not token:
+            return jsonify({"status": "fail", "message": "Missing auth token"}), 401
+
+        try:
+            data, user = read_token(token)
+        except jwt.ExpiredSignatureError:
+            # if it's expired we don't want it lingering in the db
+            BlacklistToken.check_blacklist(token)
+            return jsonify({"status": "fail", "message": "Token has expired."}), 401
+        except jwt.InvalidTokenError:
+            return jsonify({"status": "fail", "message": "Invalid auth token."}), 401
+
+        return f(user, *args, **kwargs)
 
-    @wraps(f)
-    def decorator(*args, **kwargs):
-        return _token_decorator(True, f, *args, **kwargs)
     return decorator

sachet/server/users/views.py

@@ -1,7 +1,8 @@
+import jwt
 from flask import Blueprint, request, jsonify
 from flask.views import MethodView
-from sachet.server.models import token_required, admin_required, User
-from sachet.server import bcrypt
+from sachet.server.models import auth_required, read_token, User, BlacklistToken
+from sachet.server import bcrypt, db
 
 users_blueprint = Blueprint("users_blueprint", __name__)
 
@@ -42,9 +43,46 @@ users_blueprint.add_url_rule(
 )
 
 
+class LogoutAPI(MethodView):
+    """Endpoint to revoke a user's token."""
+
+    @auth_required
+    def post(user, self):
+        post_data = request.get_json()
+        token = post_data.get("token")
+        if not token:
+            return jsonify({"status": "fail", "message": "Specify a token to revoke."}), 400
+
+        res = BlacklistToken.check_blacklist(token)
+        if res:
+            return jsonify({"status": "fail", "message": "Token already revoked."}), 400
+
+        try:
+            data, token_user = read_token(token)
+        except jwt.ExpiredSignatureError:
+            return jsonify({"status": "fail", "message": "Token already expired."}), 400
+        except jwt.InvalidTokenError:
+            return jsonify({"status": "fail", "message": "Invalid auth token."}), 400
+
+        if user == token_user or user.admin == True:
+            entry = BlacklistToken(token=token)
+            db.session.add(entry)
+            db.session.commit()
+            return jsonify({"status": "success", "message": "Token revoked."}), 200
+        else:
+            return jsonify({"status": "fail", "message": "You are not allowed to revoke this token."}), 403
+
+
+users_blueprint.add_url_rule(
+    "/users/logout",
+    view_func=LogoutAPI.as_view("logout_api"),
+    methods=['POST']
+)
+
+
 class UserAPI(MethodView):
     """User information API"""
-    @token_required
+    @auth_required
     def get(user, self, username):
         info_user = User.query.filter_by(username=username).first()
         if (not info_user) or (info_user != user and not user.admin):

tests/test_auth.py

@@ -84,3 +84,104 @@ def test_login(client, users):
     assert resp_json.get("username") == "jeff"
     token = resp_json.get("auth_token")
     assert token is not None and token != ""
+
+
+def test_logout(client, tokens, validate_info):
+    """Test logging out."""
+
+    # unauthenticated
+    resp = client.post("/users/logout", json={
+            "token": tokens["jeff"]
+        },
+    )
+    assert resp.status_code == 401
+
+    # missing token
+    resp = client.post("/users/logout", json={
+
+        },
+        headers={
+            "Authorization": f"bearer {tokens['jeff']}"
+        }
+    )
+    assert resp.status_code == 400
+
+    # invalid token
+    resp = client.post("/users/logout", json={
+            "token": "not.real.jwt"
+        },
+        headers={
+            "Authorization": f"bearer {tokens['jeff']}"
+        }
+    )
+    assert resp.status_code == 400
+
+    # wrong user's token
+    resp = client.post("/users/logout", json={
+            "token": tokens["administrator"]
+        },
+        headers={
+            "Authorization": f"bearer {tokens['jeff']}"
+        }
+    )
+    assert resp.status_code == 403
+
+    # check that we can access this endpoint before logging out
+    resp = client.get("/users/jeff",
+        headers={
+            "Authorization": f"bearer {tokens['jeff']}"
+        }
+    )
+    assert resp.status_code == 200
+    validate_info("jeff", resp.get_json())
+
+    # valid logout
+    resp = client.post("/users/logout", json={
+            "token": tokens["jeff"]
+        },
+        headers={
+            "Authorization": f"bearer {tokens['jeff']}"
+        }
+    )
+    assert resp.status_code == 200
+
+    # check that the logout worked
+
+    resp = client.get("/users/jeff",
+        headers={
+            "Authorization": f"bearer {tokens['jeff']}"
+        }
+    )
+    assert resp.status_code == 401
+
+def test_admin_revoke(client, tokens, validate_info):
+    """Test that an admin can revoke any token from other users."""
+
+    resp = client.post("/users/logout", json={
+            "token": tokens["jeff"]
+        },
+        headers={
+            "Authorization": f"bearer {tokens['administrator']}"
+        }
+    )
+    assert resp.status_code == 200
+
+    # check that the logout worked
+
+    resp = client.get("/users/jeff",
+        headers={
+            "Authorization": f"bearer {tokens['jeff']}"
+        }
+    )
+    assert resp.status_code == 401
+
+    # try revoking twice
+
+    resp = client.post("/users/logout", json={
+            "token": tokens["jeff"]
+        },
+        headers={
+            "Authorization": f"bearer {tokens['administrator']}"
+        }
+    )
+    assert resp.status_code == 400