diff --git a/changelog.d/9376.feature b/changelog.d/9376.feature
new file mode 100644
index 0000000000..68ea21dbdd
--- /dev/null
+++ b/changelog.d/9376.feature
@@ -0,0 +1 @@
+Add support for receiving OpenID Connect authentication responses via form `POST`s rather than `GET`s.
diff --git a/synapse/handlers/oidc_handler.py b/synapse/handlers/oidc_handler.py
index c00b9c57c6..07db1e31e4 100644
--- a/synapse/handlers/oidc_handler.py
+++ b/synapse/handlers/oidc_handler.py
@@ -48,7 +48,26 @@ if TYPE_CHECKING:
logger = logging.getLogger(__name__)
-SESSION_COOKIE_NAME = b"oidc_session"
+# we want the cookie to be returned to us even when the request is the POSTed
+# result of a form on another domain, as is used with `response_mode=form_post`.
+#
+# Modern browsers will not do so unless we set SameSite=None; however *older*
+# browsers (including all versions of Safari on iOS 12?) don't support
+# SameSite=None, and interpret it as SameSite=Strict:
+# https://bugs.webkit.org/show_bug.cgi?id=198181
+#
+# As a rather painful workaround, we set *two* cookies, one with SameSite=None
+# and one with no SameSite, in the hope that at least one of them will get
+# back to us.
+#
+# Secure is necessary for SameSite=None (and, empirically, also breaks things
+# on iOS 12.)
+#
+# Here we have the names of the cookies, and the options we use to set them.
+_SESSION_COOKIES = [
+ (b"oidc_session", b"Path=/_synapse/client/oidc; HttpOnly; Secure; SameSite=None"),
+ (b"oidc_session_no_samesite", b"Path=/_synapse/client/oidc; HttpOnly"),
+]
#: A token exchanged from the token endpoint, as per RFC6749 sec 5.1. and
#: OpenID.Core sec 3.1.3.3.
@@ -149,26 +168,33 @@ class OidcHandler:
# otherwise, it is presumably a successful response. see:
# https://tools.ietf.org/html/rfc6749#section-4.1.2
- # Fetch the session cookie
- session = request.getCookie(SESSION_COOKIE_NAME) # type: Optional[bytes]
- if session is None:
+ # Fetch the session cookie. See the comments on SESSION_COOKIES for why there
+ # are two.
+
+ for cookie_name, _ in _SESSION_COOKIES:
+ session = request.getCookie(cookie_name) # type: Optional[bytes]
+ if session is not None:
+ break
+ else:
logger.info("Received OIDC callback, with no session cookie")
self._sso_handler.render_error(
request, "missing_session", "No session cookie found"
)
return
- # Remove the cookie. There is a good chance that if the callback failed
+ # Remove the cookies. There is a good chance that if the callback failed
# once, it will fail next time and the code will already be exchanged.
- # Removing it early avoids spamming the provider with token requests.
- request.addCookie(
- SESSION_COOKIE_NAME,
- b"",
- path="/_synapse/oidc",
- expires="Thu, Jan 01 1970 00:00:00 UTC",
- httpOnly=True,
- sameSite="lax",
- )
+ # Removing the cookies early avoids spamming the provider with token requests.
+ #
+ # we have to build the header by hand rather than calling request.addCookie
+ # because the latter does not support SameSite=None
+ # (https://twistedmatrix.com/trac/ticket/10088)
+
+ for cookie_name, options in _SESSION_COOKIES:
+ request.cookies.append(
+ b"%s=; Expires=Thu, Jan 01 1970 00:00:00 UTC; %s"
+ % (cookie_name, options)
+ )
# Check for the state query parameter
if b"state" not in request.args:
@@ -722,14 +748,18 @@ class OidcProvider:
ui_auth_session_id=ui_auth_session_id,
),
)
- request.addCookie(
- SESSION_COOKIE_NAME,
- cookie,
- path="/_synapse/client/oidc",
- max_age="3600",
- httpOnly=True,
- sameSite="lax",
- )
+
+ # Set the cookies. See the comments on _SESSION_COOKIES for why there are two.
+ #
+ # we have to build the header by hand rather than calling request.addCookie
+ # because the latter does not support SameSite=None
+ # (https://twistedmatrix.com/trac/ticket/10088)
+
+ for cookie_name, options in _SESSION_COOKIES:
+ request.cookies.append(
+ b"%s=%s; Max-Age=3600; %s"
+ % (cookie_name, cookie.encode("utf-8"), options)
+ )
metadata = await self.load_metadata()
authorization_endpoint = metadata.get("authorization_endpoint")
diff --git a/synapse/rest/synapse/client/oidc/callback_resource.py b/synapse/rest/synapse/client/oidc/callback_resource.py
index f7a0bc4bdb..1af33f0a45 100644
--- a/synapse/rest/synapse/client/oidc/callback_resource.py
+++ b/synapse/rest/synapse/client/oidc/callback_resource.py
@@ -12,19 +12,30 @@
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
+
import logging
+from typing import TYPE_CHECKING
from synapse.http.server import DirectServeHtmlResource
+if TYPE_CHECKING:
+ from synapse.server import HomeServer
+
logger = logging.getLogger(__name__)
class OIDCCallbackResource(DirectServeHtmlResource):
isLeaf = 1
- def __init__(self, hs):
+ def __init__(self, hs: "HomeServer"):
super().__init__()
self._oidc_handler = hs.get_oidc_handler()
async def _async_render_GET(self, request):
await self._oidc_handler.handle_oidc_callback(request)
+
+ async def _async_render_POST(self, request):
+ # the auth response can be returned via an x-www-form-urlencoded form instead
+ # of GET params, as per
+ # https://openid.net/specs/oauth-v2-form-post-response-mode-1_0.html.
+ await self._oidc_handler.handle_oidc_callback(request)
diff --git a/tests/handlers/test_oidc.py b/tests/handlers/test_oidc.py
index bdd2e02eae..cf1de28fa9 100644
--- a/tests/handlers/test_oidc.py
+++ b/tests/handlers/test_oidc.py
@@ -327,7 +327,9 @@ class OidcHandlerTestCase(HomeserverTestCase):
def test_redirect_request(self):
"""The redirect request has the right arguments & generates a valid session cookie."""
- req = Mock(spec=["addCookie"])
+ req = Mock(spec=["cookies"])
+ req.cookies = []
+
url = self.get_success(
self.provider.handle_redirect_request(req, b"http://client/redirect")
)
@@ -346,19 +348,16 @@ class OidcHandlerTestCase(HomeserverTestCase):
self.assertEqual(len(params["state"]), 1)
self.assertEqual(len(params["nonce"]), 1)
- # Check what is in the cookie
- # note: python3.5 mock does not have the .called_once() method
- calls = req.addCookie.call_args_list
- self.assertEqual(len(calls), 1) # called once
- # For some reason, call.args does not work with python3.5
- args = calls[0][0]
- kwargs = calls[0][1]
+ # Check what is in the cookies
+ self.assertEqual(len(req.cookies), 2) # two cookies
+ cookie_header = req.cookies[0]
# The cookie name and path don't really matter, just that it has to be coherent
# between the callback & redirect handlers.
- self.assertEqual(args[0], b"oidc_session")
- self.assertEqual(kwargs["path"], "/_synapse/client/oidc")
- cookie = args[1]
+ parts = [p.strip() for p in cookie_header.split(b";")]
+ self.assertIn(b"Path=/_synapse/client/oidc", parts)
+ name, cookie = parts[0].split(b"=")
+ self.assertEqual(name, b"oidc_session")
macaroon = pymacaroons.Macaroon.deserialize(cookie)
state = self.handler._token_generator._get_value_from_macaroon(
@@ -489,7 +488,7 @@ class OidcHandlerTestCase(HomeserverTestCase):
def test_callback_session(self):
"""The callback verifies the session presence and validity"""
- request = Mock(spec=["args", "getCookie", "addCookie"])
+ request = Mock(spec=["args", "getCookie", "cookies"])
# Missing cookie
request.args = {}
@@ -943,13 +942,14 @@ def _build_callback_request(
spec=[
"args",
"getCookie",
- "addCookie",
+ "cookies",
"requestHeaders",
"getClientIP",
"getHeader",
]
)
+ request.cookies = []
request.getCookie.return_value = session
request.args = {}
request.args[b"code"] = [code.encode("utf-8")]
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