Add two-factor authentication

Adds optional two-factor authentication support using TOTP, and
including backup codes in case of a lost 2FA device.

tildes/alembic/versions/67e332481a6e_add_two_factor_authentication.py

@@ -0,0 +1,38 @@
+"""Add two-factor authentication
+
+Revision ID: 67e332481a6e
+Revises: fab922a8bb04
+Create Date: 2018-07-31 02:53:50.182862
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+# revision identifiers, used by Alembic.
+revision = "67e332481a6e"
+down_revision = "fab922a8bb04"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.add_column(
+        "users",
+        sa.Column(
+            "two_factor_backup_codes", postgresql.ARRAY(sa.Text()), nullable=True
+        ),
+    )
+    op.add_column(
+        "users",
+        sa.Column(
+            "two_factor_enabled", sa.Boolean(), server_default="false", nullable=False
+        ),
+    )
+    op.add_column("users", sa.Column("two_factor_secret", sa.Text(), nullable=True))
+
+
+def downgrade():
+    op.drop_column("users", "two_factor_secret")
+    op.drop_column("users", "two_factor_enabled")
+    op.drop_column("users", "two_factor_backup_codes")

tildes/requirements-to-freeze.txt

@@ -13,6 +13,7 @@ html5lib
 ipython
 mypy
 mypy-extensions
+Pillow
 prometheus-client
 psycopg2
 publicsuffix2
@@ -20,6 +21,7 @@ pydocstyle
 pylama
 pylama-pylint
 pylint==1.7.5  # pylama has issues with 1.8.1
+pyotp
 pyramid
 pyramid-debugtoolbar
 pyramid-ipython
@@ -30,6 +32,7 @@ pyramid-webassets
 pytest
 pytest-mock
 PyYAML  # needs to be installed separately for webassets
+qrcode
 SQLAlchemy
 SQLAlchemy-Utils
 stripe

tildes/requirements.txt

@@ -38,6 +38,7 @@ parso==0.3.1
 PasteDeploy==1.5.2
 pexpect==4.6.0
 pickleshare==0.7.4
+Pillow==5.2.0
 plaster==1.0
 plaster-pastedeploy==0.6
 pluggy==0.7.1
@@ -55,6 +56,7 @@ Pygments==2.2.0
 pylama==7.4.3
 pylama-pylint==3.0.1
 pylint==1.7.5
+pyotp==2.2.6
 pyramid==1.9.2
 pyramid-debugtoolbar==4.4
 pyramid-ipython==0.2
@@ -68,6 +70,7 @@ pytest-mock==1.10.0
 python-dateutil==2.7.3
 python-editor==1.0.3
 PyYAML==3.13
+qrcode==6.0
 redis==2.10.6
 repoze.lru==0.7
 requests==2.19.1

tildes/tildes/lib/ratelimit.py

@@ -279,6 +279,7 @@ class RateLimitedAction:
 # each action must have a unique name to prevent key collisions
 _RATE_LIMITED_ACTIONS = (
     RateLimitedAction("login", timedelta(hours=1), 20),
+    RateLimitedAction("login_two_factor", timedelta(hours=1), 20),
     RateLimitedAction("register", timedelta(hours=1), 50),
 )
 

tildes/tildes/models/user/user.py

@@ -4,6 +4,7 @@ from datetime import datetime
 from typing import Any, List, Optional, Sequence, Tuple
 
 from mypy_extensions import NoReturn
+import pyotp
 from pyramid.security import (
     ALL_PERMISSIONS,
     Allow,
@@ -21,7 +22,7 @@ from sqlalchemy import (
     Text,
     TIMESTAMP,
 )
-from sqlalchemy.dialects.postgresql import ENUM
+from sqlalchemy.dialects.postgresql import ARRAY, ENUM
 from sqlalchemy.ext.hybrid import hybrid_property
 from sqlalchemy.orm import deferred
 from sqlalchemy.sql.expression import text
@@ -62,6 +63,9 @@ class User(DatabaseModel):
             ),
         )
     )
+    two_factor_enabled: bool = Column(Boolean, nullable=False, server_default="false")
+    two_factor_secret: Optional[str] = deferred(Column(Text))
+    two_factor_backup_codes: List[str] = deferred(Column(ARRAY(Text)))
     created_time: datetime = Column(
         TIMESTAMP(timezone=True),
         nullable=False,
@@ -161,6 +165,24 @@ class User(DatabaseModel):
         # disable mypy on this line because it doesn't handle setters correctly
         self.password = new_password  # type: ignore
 
+    def is_correct_two_factor_code(self, code: str) -> bool:
+        """Verify that a TOTP/backup code is correct."""
+        totp = pyotp.TOTP(self.two_factor_secret)
+        code = code.strip()
+
+        if totp.verify(code.replace(" ", "")):
+            return True
+        elif code in self.two_factor_backup_codes:
+            # Need to set the attribute so SQLAlchemy knows it changed
+            self.two_factor_backup_codes = [
+                backup_code
+                for backup_code in self.two_factor_backup_codes
+                if backup_code != code
+            ]
+            return True
+
+        return False
+
     @property
     def email_address(self) -> NoReturn:
         """Return an error since reading the email address isn't possible."""

tildes/tildes/routes.py

@@ -20,6 +20,7 @@ def includeme(config: Configurator) -> None:
     config.add_route("groups", "/groups")
 
     config.add_route("login", "/login")
+    config.add_route("login_two_factor", "/login_two_factor")
     config.add_route("logout", "/logout", factory=LoggedInFactory)
 
     config.add_route("register", "/register")
@@ -61,6 +62,14 @@ def includeme(config: Configurator) -> None:
         "/settings/account_recovery",
         factory=LoggedInFactory,
     )
+    config.add_route(
+        "settings_two_factor", "/settings/two_factor", factory=LoggedInFactory
+    )
+    config.add_route(
+        "settings_two_factor_qr_code",
+        "/settings/two_factor/qr_code",
+        factory=LoggedInFactory,
+    )
     config.add_route(
         "settings_comment_visits", "/settings/comment_visits", factory=LoggedInFactory
     )

tildes/tildes/templates/intercooler/login_two_factor.jinja2

@@ -0,0 +1,17 @@
+<p>Two-factor authentication is enabled on this account. Please enter the code from your authenticator app below. If you do not have access to your authenticator device, enter a backup code.</p>
+
+<form class="form-narrow" method="post" action="/login_two_factor" data-ic-post-to="/login_two_factor">
+  <input type="hidden" name="csrf_token" value="{{ get_csrf_token() }}">
+  {% if keep %}
+  <input type="hidden" name="keep" value="on">
+  {% endif %}
+
+  <div class="form-group">
+    <label class="form-label col-4" for="code">Code</label>
+    <input class="form-input" id="code" name="code" type="text" placeholder="Code" data-js-auto-focus>
+  </div>
+
+  <div class="form-buttons">
+    <button class="btn btn-primary" type="submit">Continue</button>
+  </div>
+</form>

tildes/tildes/templates/intercooler/two_factor_disabled.jinja2

@@ -0,0 +1,3 @@
+<p>Two-factor authentication has been disabled. You will no longer need a code when logging in.</p>
+
+<p>Keep in mind: if you ever reenable two-factor authentication, your previous backup codes will not be valid.</p>

tildes/tildes/templates/intercooler/two_factor_enabled.jinja2

@@ -0,0 +1,10 @@
+<p>Congratulations! Two-factor authentication has been enabled.</p>
+
+<p>These are your backup codes. <strong class="text-warning">Make sure to write them down and store them in a safe place.</strong>
+In the event that you lose access to your authenticator device, you will need these to regain access to your account. Each code can only be used once.</p>
+
+<code>
+{% for code in backup_codes %}
+	- {{ code }}<br />
+{% endfor %}
+</code>

tildes/tildes/templates/login.jinja2

@@ -5,7 +5,7 @@
 {% block main_heading %}Log in{% endblock %}
 
 {% block content %}
-  <form class="form-narrow" method="post" data-ic-post-to="/login">
+  <form class="form-narrow" method="post" data-ic-post-to="/login" data-ic-target="closest main">
     <input type="hidden" name="csrf_token" value="{{ get_csrf_token() }}">
 
     <div class="form-group">

tildes/tildes/templates/settings.jinja2

@@ -95,6 +95,10 @@
       <a href="/settings/account_recovery">Set up account recovery</a>
       <div class="text-small text-secondary">To be able to regain access in case of lost password, compromise, etc.</div>
     </li>
+    <li>
+      <a href="/settings/two_factor">Set up two-factor authentication</a>
+      <div class="text-small text-secondary">For extra security, you can enable two-factor authentication.</div>
+    </li>
     <li>
       <a href="/settings/comment_visits">Toggle marking new comments (currently {{ 'enabled' if request.user.track_comment_visits else 'disabled' }})</a>
       <div class="text-small text-secondary">Marks new comments in topics since your last visit, and which topics have any</div>

tildes/tildes/templates/settings_two_factor.jinja2

@@ -0,0 +1,53 @@
+{% extends 'base_no_sidebar.jinja2' %}
+
+{% block title %}Set up two-factor authentication{% endblock %}
+
+{% block main_heading %}Set up two-factor authentication{% endblock %}
+
+{% block content %}
+{% if request.user.two_factor_enabled %}
+<p>You already have two-factor authentication enabled. To disable it, enter a code from your authenticator device below and click the button. If you do not have access to your authenticator device, enter a backup code.</p>
+
+<form
+  name="disable-two-factor"
+  autocomplete="off"
+  data-ic-post-to="{{ request.route_url('ic_user', username=request.user.username) }}"
+  data-ic-target="closest main"
+>
+  <div class="form-group">
+    <label class="form-label" for="code">TOTP or backup code</label>
+    <input class="form-input" id="code" name="code" type="text" placeholder="Code" required>
+  </div>
+
+  <div class="form-buttons">
+    <button class="btn btn-error" type="submit">Disable two-factor authentication</button>
+  </div>
+</form>
+{% else %}
+<p>To get started, you'll need to install an app such as <a href="https://support.google.com/accounts/answer/1066447">Google Authenticator</a>, <a href="https://authy.com/download">Authy</a>, <a href="https://freeotp.github.io">FreeOTP</a>, or any app that supports TOTP.</p>
+
+<p>Next, scan the below QR code with the app of your choice.</p>
+
+<img src="/settings/two_factor/qr_code" alt="" />
+
+<p>Lastly, enter the 6-digit code displayed in the app.</p>
+
+<div class="divider"></div>
+
+<form
+  name="enable-two-factor"
+  autocomplete="off"
+  data-ic-post-to="{{ request.route_url('ic_user', username=request.user.username) }}"
+  data-ic-target="closest main"
+>
+  <div class="form-group">
+    <label class="form-label" for="code">Code</label>
+    <input class="form-input" id="code" name="code" type="text" placeholder="Code" maxlength="6" pattern="[0-9]{6}">
+  </div>
+
+  <div class="form-buttons">
+    <button class="btn btn-primary" type="submit">Enable two-factor authentication</button>
+  </div>
+</form>
+{% endif %}
+{% endblock %}

tildes/tildes/views/api/web/user.py

@@ -1,10 +1,17 @@
 """Web API endpoints related to users."""
 
+import random
+import string
 from typing import Optional
 
 from marshmallow import ValidationError
 from marshmallow.fields import String
-from pyramid.httpexceptions import HTTPForbidden, HTTPUnprocessableEntity
+import pyotp
+from pyramid.httpexceptions import (
+    HTTPForbidden,
+    HTTPUnauthorized,
+    HTTPUnprocessableEntity,
+)
 from pyramid.request import Request
 from pyramid.response import Response
 from sqlalchemy.exc import IntegrityError
@@ -84,6 +91,63 @@ def patch_change_email_address(
     return Response("Your email address has been updated")
 
 
+def generate_backup_code() -> str:
+    """Generate a user-friendly (easy to read) backup code for 2FA."""
+    parts = []
+    # Generate 4 four-length random strings.
+    for _ in range(4):
+        parts.append("".join(random.choices(string.ascii_lowercase, k=4)))
+
+    # Combine parts to make one, e.g. xxxx xxxx xxxx xxxx
+    return " ".join(parts)
+
+
+@ic_view_config(
+    route_name="user",
+    request_method="POST",
+    request_param="ic-trigger-name=enable-two-factor",
+    renderer="two_factor_enabled.jinja2",
+    permission="change_two_factor",
+)
+def post_enable_two_factor(request: Request) -> dict:
+    """Enable two-factor authentication for the user."""
+    user = request.context
+    totp = pyotp.TOTP(user.two_factor_secret)
+    code = str(request.params.get("code"))
+
+    if not totp.verify(code):
+        raise HTTPUnprocessableEntity("Invalid code, please try again.")
+
+    # Generate 10 backup codes.
+    backup_codes = [generate_backup_code() for _ in range(10)]
+
+    request.user.two_factor_enabled = True
+    request.user.two_factor_backup_codes = backup_codes
+
+    return {"backup_codes": backup_codes}
+
+
+@ic_view_config(
+    route_name="user",
+    request_method="POST",
+    request_param="ic-trigger-name=disable-two-factor",
+    renderer="two_factor_disabled.jinja2",
+    permission="change_two_factor",
+)
+def post_disable_two_factor(request: Request) -> Response:
+    """Disable two-factor authentication for the user."""
+    code = str(request.params.get("code"))
+
+    if not request.user.is_correct_two_factor_code(code):
+        raise HTTPUnauthorized(body="Invalid code")
+
+    request.user.two_factor_enabled = False
+    request.user.two_factor_secret = None
+    request.user.two_factor_backup_codes = None
+
+    return {}
+
+
 @ic_view_config(
     route_name="user",
     request_method="PATCH",

tildes/tildes/views/login.py

@@ -1,7 +1,9 @@
 """Views related to logging in/out."""
 
-from pyramid.httpexceptions import HTTPFound, HTTPUnprocessableEntity
+from pyramid.httpexceptions import HTTPFound, HTTPUnauthorized, HTTPUnprocessableEntity
+from pyramid.renderers import render_to_response
 from pyramid.request import Request
+from pyramid.response import Response
 from pyramid.security import NO_PERMISSION_REQUIRED, remember
 from pyramid.view import view_config
 from webargs.pyramidparser import use_kwargs
@@ -24,6 +26,22 @@ def get_login(request: Request) -> dict:
     return {}
 
 
+def finish_login(request: Request, user: User) -> None:
+    """Save the user ID into session."""
+    # Username/password were correct - attach the user_id to the session
+    remember(request, user.user_id)
+
+    # Depending on "keep me logged in", set session timeout to 1 year or 1 day
+    if request.params.get("keep"):
+        request.session.adjust_timeout_for_session(31_536_000)
+    else:
+        request.session.adjust_timeout_for_session(86_400)
+
+    # set request.user before logging so the user is associated with the event
+    request.user = user
+    request.db_session.add(Log(LogEventType.USER_LOG_IN, request))
+
+
 @view_config(
     route_name="login", request_method="POST", permission=NO_PERMISSION_REQUIRED
 )
@@ -57,20 +75,45 @@ def post_login(request: Request, username: str, password: str) -> HTTPFound:
     if user.is_banned:
         raise HTTPUnprocessableEntity("This account has been banned")
 
-    # Username/password were correct - attach the user_id to the session
-    remember(request, user.user_id)
+    # If 2FA is enabled, save username to session and make user enter code
+    if user.two_factor_enabled:
+        request.session["two_factor_username"] = username
+        return render_to_response(
+            "tildes:templates/intercooler/login_two_factor.jinja2",
+            {"keep": request.params.get("keep")},
+            request=request,
+        )
 
-    # Depending on "keep me logged in", set session timeout to 1 year or 1 day
-    if request.params.get("keep"):
-        request.session.adjust_timeout_for_session(31_536_000)
-    else:
-        request.session.adjust_timeout_for_session(86_400)
+    finish_login(request, user)
+
+    raise HTTPFound(location="/")
 
-    # set request.user before logging so the user is associated with the event
-    request.user = user
-    request.db_session.add(Log(LogEventType.USER_LOG_IN, request))
+
+@view_config(
+    route_name="login_two_factor",
+    request_method="POST",
+    permission=NO_PERMISSION_REQUIRED,
+)
+@not_logged_in
+@rate_limit_view("login_two_factor")
+def post_login_two_factor(request: Request) -> Response:
+    """Process a log in request with 2FA."""
+    # Look up the user for the supplied username
+    user = (
+        request.query(User)
+        .undefer_all_columns()
+        .filter(User.username == request.session["two_factor_username"])
+        .one_or_none()
+    )
+    code = str(request.params.get("code"))
+
+    if user.is_correct_two_factor_code(code):
+        del request.session["two_factor_username"]
+        finish_login(request, user)
 
         raise HTTPFound(location="/")
+    else:
+        raise HTTPUnauthorized(body="Invalid code, please try again.")
 
 
 @view_config(route_name="logout")

tildes/tildes/views/settings.py

@@ -1,9 +1,12 @@
 """Views related to user settings."""
 
-from pyramid.httpexceptions import HTTPUnprocessableEntity
+from io import BytesIO
+import pyotp
+from pyramid.httpexceptions import HTTPForbidden, HTTPUnprocessableEntity
 from pyramid.request import Request
 from pyramid.response import Response
 from pyramid.view import view_config
+import qrcode
 from webargs.pyramidparser import use_kwargs
 
 from tildes.schemas.user import EMAIL_ADDRESS_NOTE_MAX_LENGTH, UserSchema
@@ -35,6 +38,13 @@ def get_settings_account_recovery(request: Request) -> dict:
     return {"note_max_length": EMAIL_ADDRESS_NOTE_MAX_LENGTH}
 
 
+@view_config(route_name="settings_two_factor", renderer="settings_two_factor.jinja2")
+def get_settings_two_factor(request: Request) -> dict:
+    """Generate the two-factor authentication page."""
+    # pylint: disable=unused-argument
+    return {}
+
+
 @view_config(
     route_name="settings_comment_visits", renderer="settings_comment_visits.jinja2"
 )
@@ -60,6 +70,27 @@ def get_settings_password_change(request: Request) -> dict:
     return {}
 
 
+@view_config(route_name="settings_two_factor_qr_code")
+def get_settings_two_factor_qr_code(request: Request) -> Response:
+    """Generate the 2FA QR code."""
+    # If 2FA is already enabled, don't expose the secret.
+    if request.user.two_factor_enabled:
+        raise HTTPForbidden("Already enabled")
+
+    # Generate a new secret key if the user doesn't have one.
+    if request.user.two_factor_secret is None:
+        request.user.two_factor_secret = pyotp.random_base32()
+
+    totp = pyotp.totp.TOTP(request.user.two_factor_secret)
+    otp_uri = totp.provisioning_uri(request.user.username, issuer_name="Tildes")
+    byte_io = BytesIO()
+    img = qrcode.make(otp_uri, border=2, box_size=4)
+
+    img.save(byte_io, "PNG")
+
+    return Response(byte_io.getvalue(), cache_control="private, no-cache")
+
+
 @view_config(route_name="settings_password_change", request_method="POST")
 @use_kwargs(
     {