Keycloak redirect_fragment conflicts with react-router hashRouter

Question

I'm running into an issue with the redirection that happens after a user of my app authenticates with Keycloak.

My app uses react-router hashRouter. When the initial redirect happens, I get a redirect_fragment that looks something like this:

http://localhost:3000/lol.html?redirect_fragment=%2F&redirect_fragment=%2Fstate%3D1c5900ee-954f-4532-b01c-dcf5d88f07a2%26code%3DKZNXVqQCcIXTCFu2ZIkx4quXa6zJb59zGKpNIhZwfNo.d2786d1e-67cd-437f-a873-bad49126bad4&redirect_fragment=%2Fstate%3D51a9cb44-b80a-4c14-8f3d-f04dfdb84377%26code%3Dp5cKQ7xVCR_n1s4ucXZTSE3O1T5lwNri_PBKD07Mt1Y.63364a83-f04f-4e64-a33e-faf00f6cd4ff&redirect_fragment=%2Fstate%3D05155315-ab60-4990-8d4e-444c7cce9748%26code%3DBxxpf_uMB28rKAQ6MXFTTrL9RE4rC3UtwCMXLu_K1Zo.4ce56da0-8e52-47e3-a0f2-4f982599bb98#/state=f3e362e4-c030-40ac-80df-9f9882296977&code=8HHTgd3KdlfwcupXR_5nDV0CqZNPV1xdCu3udc6l5xM.97b3ea71-366a-4038-a7ce-30ac2f416807

The URL keeps growing from there. I've read a few posts already that indicate that redirection from keycloak might have a problem with client-side routing via location.hash ... Any thoughts would be appreciated!

Answer 1

I think I figured it out!

The redirection loop seems to stop if I use the 'noslash' hashRouter instead of the default which contains a slash.

My URLs look like this: localhost:3000/lol.html#client/side/route

instead of this: localhost:3000/lol.html#/client/side/route

The redirection now seems to terminate appropriately after one redirect, but now I'm running into a different problem where the hash portion of my route is not being honored by react-router...

EDIT: I figured the second issue out

react-router creates a wrapper around window.location that it uses to tell which client side "page" it is currently on. I found that this wrapper was out of sync with window.location.

Check this console output out. This was taken immediately after the redirection resolved (and the page was blank):

history pathname is /state=aon03i-238hnsln-soih930-8hsdlkh9-982hnkui-89hkgyq-8ihbei78-893hiugsu

history hash is (empty)

window.location pathname is /lol.html

window.location hash is #users/1

The state=blah-blah-blah in the history.pathname is part of the redirect url that keycloak sends back after auth. You'll notice that window.location is updated to the correct path / hash, but that history seems to be one URL behind. Maybe keycloak directly modifies window.location to perform this redirection?

I tried using a history.push(window.location.hash) to push the hash fragment and update react router, but got the error "this entry already exists on the stack". Since it clearly is not on the top of the location stack, this led me to believe that react-router compares window.location with its internal location to figure out where it ultimately is. So how did I get around this?

I used history.replace() instead, which just replaces the entry on the top of the stack with a new value, instead of pushing a new entry to the stack. This also makes sense, since we don't want users who navigate "back" in their browsers to go back to that /state=blah-blah-blah url <-- replace eliminates this entry from the history stack.

One final piece: react-router history.location, like window.location, has both pathname and hash components. HashRouter uses the history.location.pathname component to keep track of the client side route after the hash in the browser. The equivalent of this in window.location is stored in window.location.hash, so we will be using this as the value passed to history.replace() instead of window.location.pathname. This confused me for a bit, but makes sense when you think about it.

react-router history also keeps track of its current route with a prepended / instead of a prepended #, since it's just treating it like any normal URL. Before I called history.replace(), I needed to take my window.location.hash, replace the leading hash with a / and then pass that value history.replace()

const slashPath = window.location.hash.replace('#', '/'); history.replace(slashPath);

Whew!