[pve-devel] [PATCH widget-toolkit] fix external linking to products by setting cookie SameSite attribute to lax

[Dominik Csapak]

We introduced the 'strict' setting when browsers warned about our
cookies not having any SameSite setting [0]

While this works in general, it had an unforeseen side effect:

When linking to a URL of our products, the cookie does not get sent on
the initial page load, leading to the username/CSRFPreventionToken not
being set in the index response.

Our UI code interprets this as being logged out (e.g. because the ticket
is not valid) and clears the cookie, displaying the login window.

The MDN reference[1] says that setting it to 'lax' is similar to
'strict', but sends the cookie when navigating *to* our origin even from
other sites, which is what we want when linking from elsewhere. (This
would have also been the default if we wouldn't have set any attribute).

0: https://lore.proxmox.com/pve-devel/20230315162630.289768-1-m.carrara@proxmox.com/
1: https://developer.mozilla.org/en-US/docs/Web/HTTP/Cookies#SameSite_attribute

Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
---
Alternatively, we could try to modify the client code to retry with the
content of the cookie (which the client still has), to generate a
ticket. Though I'm not sure that will work correctly, since I observed
some even stricter behaviour in Firefox ESR, where not only the
navigation part did not send the cookie, but also subsequent requests
did not do that (I did not test for long, so this may have been an
artifact of a different issue).

I'd generally prefer this solution, since it's less intrusive and
restores the behaviour we had before the change, altough I'm not against
implementing a retry in the client code if that's preferred.

 src/Utils.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Utils.js b/src/Utils.js
index 7dd034a..b68c0f4 100644
--- a/src/Utils.js
+++ b/src/Utils.js
@@ -317,7 +317,7 @@ utilities: {
 	// that way the cookie gets deleted after the browser window is closed
 	if (data.ticket) {
 	    Proxmox.CSRFPreventionToken = data.CSRFPreventionToken;
-	    Ext.util.Cookies.set(Proxmox.Setup.auth_cookie_name, data.ticket, null, '/', null, true, "strict");
+	    Ext.util.Cookies.set(Proxmox.Setup.auth_cookie_name, data.ticket, null, '/', null, true, "lax");
 	}
 
 	if (data.token) {
@@ -343,7 +343,7 @@ utilities: {
 	    return;
 	}
 	// ExtJS clear is basically the same, but browser may complain if any cookie isn't "secure"
-	Ext.util.Cookies.set(Proxmox.Setup.auth_cookie_name, "", new Date(0), null, null, true, "strict");
+	Ext.util.Cookies.set(Proxmox.Setup.auth_cookie_name, "", new Date(0), null, null, true, "lax");
 	window.localStorage.removeItem("ProxmoxUser");
     },
 
-- 
2.39.5