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")
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