MSC4174: Web push by p1gp1g · Pull Request #4174 · matrix-org/matrix-spec-proposals

p1gp1g · 2024-08-01T15:52:06Z

Client implementation:
synapse impl: element-hq/synapse#17987
updated hydrogen impl: element-hq/hydrogen-web#1201

Note: in addition to this MSC, it would be very useful to have MSC4173, if someone is interested in implementing this MSC as well

SCT Stuff:

MSC checklist

FCP tickyboxes

Signed-off-by: S1m <[email protected]>

turt2live · 2024-08-01T16:46:05Z

proposals/4174-webpush-pushkind.md

Implementation requirements:

Client

Server

@turt2live These requirements are now met

Client (Hydrogen) and Server (Synapse) implementations noted at #4174 (comment)

This MSC has changed since the implementations were made. I'm not sure what all the changes were. If they are primarily minor changes such as naming changes (e.g. renaming properties), or changes of that sort, then the implementations should still be fine as a demonstration that the MSC works. If there are any substantial changes, then the implementations may need to be updated.

The homeserver implementation for Synapse is actively being updated in element-hq/synapse#17987. It has yet to be merged.

The client implementation for Hydrogen has not been updated since Dec 2nd, 2024: element-hq/hydrogen-web#1201. The changes to the MSC since Dec 2nd, 2024 are https://github.com/matrix-org/matrix-spec-proposals/pull/4174/files/0346332a1f802425b579d2b4cdf98fe8a462d48b..f59cb97551216812d1ca492fafba05d057cc1298.

I've left a review on the Hydrogen PR with what appears to be missing from a cursory glance. As such, I think we're still missing an up-to-date client implementation.

@mscbot concern The client implementation has grown stale with respect to the MSC. See this PR review for the outstanding changes.

proposals/4174-webpush-pushkind.md

p1gp1g · 2024-08-07T10:43:25Z

Thank you for your feedback @clokep, I'm updated the proposal soon

Reword some sentences, add links

p1gp1g · 2024-11-21T08:14:02Z

Client implementation: p1gp1g/hydrogen-web@e7cc488

Add capability and VAPID

proposals/4174-webpush-pushkind.md

MatMaul · 2024-12-02T22:57:54Z

synapse impl: element-hq/synapse#17987
updated hydrogen impl: element-hq/hydrogen-web#1201

proposals/4174-webpush-pushkind.md

tulir · 2025-01-21T16:18:21Z

Implementations seem to implement what's described in the MSC, so removing the needs-checking label

proposals/4174-webpush-pushkind.md

anoadragon453 · 2026-03-11T21:54:12Z

proposals/4174-webpush-pushkind.md

The homeserver implementation for Synapse is actively being updated in element-hq/synapse#17987. It has yet to be merged.

The client implementation for Hydrogen has not been updated since Dec 2nd, 2024: element-hq/hydrogen-web#1201. The changes to the MSC since Dec 2nd, 2024 are https://github.com/matrix-org/matrix-spec-proposals/pull/4174/files/0346332a1f802425b579d2b4cdf98fe8a462d48b..f59cb97551216812d1ca492fafba05d057cc1298.

I've left a review on the Hydrogen PR with what appears to be missing from a cursory glance. As such, I think we're still missing an up-to-date client implementation.

Co-authored-by: Andrew Morgan <[email protected]>

richvdh · 2026-03-17T17:37:43Z

proposals/4174-webpush-pushkind.md

@@ -0,0 +1,177 @@
+# MSC4174: Web push
+
+This MSC supersedes and replaces [MSC3013](https://github.com/matrix-org/matrix-spec-proposals/pull/3013), which introduced push notification encryption first.


@tulir claims this MSC does not adequately replace MSC3013.

@mscbot concern decide if we are replacing MSC3013 or not

I think that we only want to use the encryption defined in here for WebPush (and only because it isn't easy to replace the encryption in WebPush with something else). If we want to encrypt push notifictions over other systems, we should use a different mechanism, which will probably be something different from what 3013 defines. So 3013 will be probably replaced, but not by this MSC.

Basically, this first sentence should be removed.

Cf. #3013 (comment)

proposals/4174-webpush-pushkind.md

uhoreg · 2026-03-17T19:00:18Z

proposals/4174-webpush-pushkind.md

+`POST /_matrix/client/v3/pushers/set` now supports a new `kind`: `webpush`.
+- `kind`: is updated to introduce `webpush` which makes a
+pusher that sends Web Push encrypted messages.
+- `pushkey`: is updated, if the `kind` is `webpush`, this is the user agent public key in the uncompressed form ([SEC 1](https://www.secg.org/sec1-v2.pdf), section 2.3.3, replicated from X9.62), encoded in URL-safe Base64 without padding. The public key comes from a ECDH


Is the intention here that the pushkey is still a unique identifier for the pusher (as it is currently defined in the spec), and is also the public key? In other words, the client needs to use a unique P-256 key per pusher? If so, I think this should be stated explicity.

The spec isn't very clear for FCM/APNS push key too

proposals/4174-webpush-pushkind.md

uhoreg · 2026-03-17T19:21:56Z

proposals/4174-webpush-pushkind.md

@@ -0,0 +1,177 @@
+# MSC4174: Web push


[non-blocking] This MSC refers to the feature inconsistently as "WebPush" or "Web Push" (with or without the space), but it's hard to fault this MSC for that, since the RFCs do the same thing. However, when the spec gets written, we should pick one and stick with it.

proposals/4174-webpush-pushkind.md

richvdh · 2026-03-17T18:02:00Z

proposals/4174-webpush-pushkind.md

+Web Push is a standard for (E2EE) push notifications, defined with 3 RFC:
+- [RFC8030](https://www.rfc-editor.org/rfc/rfc8030) defines the application server to push server communications
+- [RFC8291](https://www.rfc-editor.org/rfc/rfc8291) defines the encryption:
+    - the subscribing client (user agent in RFC8030) generates a P-256 key pair the *auth* secret, and sends the P-256 public key and the *auth* secret to the home server during registration


Are the auth secret and P-256 key pair different things?

(Also, why is auth in italics?)

proposals/4174-webpush-pushkind.md

richvdh · 2026-03-17T23:13:52Z

proposals/4174-webpush-pushkind.md

+```
+"m.webpush": {
+	"enabled": true,
+	"vapid": "BNbXV88MfMI0fSxB7cDngopoviZRTbxIS0qSS-O7BZCtG04khMOn-PP2ueb_X7Aeci42n02kJ0-JJJ0uQ4ELRTs"


I slightly feel that it might be more appropriate to expose this on a separate endpoint, but it's not a strong opinion.

richvdh · 2026-03-17T23:14:58Z

proposals/4174-webpush-pushkind.md

+
+```
+"m.webpush": {
+	"enabled": true,


is enabled necessary here, or is the presence of an m.webpush entry sufficient for clients to determine that their server supports webpush?

proposals/4174-webpush-pushkind.md

richvdh · 2026-03-17T23:31:35Z

proposals/4174-webpush-pushkind.md

+safelist a private IP. (Synapse already implements [`ip_range_whitelist`](https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#ip_range_whitelist))
+It is also recommended to not follow redirection, to avoid implementation issue where the destination is checked
+before sending the request but not for redirection.
+


does the sample implementation follow these recommendations? Do they work ok in practice (especially not following redirects)?

@MatMaul may answer that question

richvdh · 2026-03-17T23:33:01Z

proposals/4174-webpush-pushkind.md

+- Until this proposal is considered stable, implementations must use
+`org.matrix.msc4174.webpush` instead of `m.webpush`.


for the capabilities? There doesn't seem much point specifying an unstable prefix for that without also doing so for Pusher.kind and the new API endpoint.

@MatMaul any opinion ?

p1gp1g · 2026-03-18T08:55:47Z

RE: P-256 concern (can't find the comment anymore)

RFC8291, web push AES-128-GCM encryption: the key is derived from the auth_secret and the ECDH secret. If somehow the P-256 curve is broken, you will still have to break the auth_secret too. And if the notification contains the content of the event, the content is encrypted with Olm/Megolm on top of that

I think we should start working with the IETF to make a new AES-256-GCM encryption for web push, that works the same way, maybe using X25519 at the same time; using a 32B pre-shared key as auth_secret would make the protocol PQ. It is more efficient than all application rolling their own protocol again

poljar · 2026-03-18T09:25:38Z

I think we should start working with the IETF to make a new AES-256-GCM encryption for web push, that works the same way, maybe using X25519 at the same time; using a 32B pre-shared key as auth_secret would make the protocol PQ. It is more efficient than all application rolling their own protocol again

I would say that this is a good idea, though I would suggest that we attempt to reuse HPKE and its single shot API if such an attempt is mounted.

HPKE also has some drafts around which add PQ-safe algorithms to the mix.

Co-authored-by: Richard van der Hoff <[email protected]>

p1gp1g · 2026-03-18T09:32:40Z

I think we should start working with the IETF [...]

I would say that this is a good idea, though I would suggest that we attempt to reuse HPKE and its single shot API is such an attempt is mounted.

HPKE also has some drafts around which add PQ-safe algorithms to the mix.

There should be different way to do it, and would be discussed with IETF. The limited size of push notifications is important, so the pre-shared key solution may be a good thing. I'm surprised they offer AES-128, I thought it wasn't considered PQ-safe

Co-authored-by: Richard van der Hoff <[email protected]>

proposals/4174-webpush-pushkind.md

Co-authored-by: Richard van der Hoff <[email protected]> Co-authored-by: Hubert Chathi <[email protected]> Co-authored-by: S1m <[email protected]>

proposals/4174-webpush-pushkind.md

Co-authored-by: S1m <[email protected]>

p1gp1g force-pushed the webpush-pushkind branch from 0f3f077 to 6ccf76d Compare August 1, 2024 15:53

Add MSC for webpush push kind

24473e5

Signed-off-by: S1m <[email protected]>

p1gp1g force-pushed the webpush-pushkind branch from 6ccf76d to 24473e5 Compare August 1, 2024 15:54

p1gp1g changed the title ~~MSC webpush push kind~~ MSC4174: webpush push kind Aug 1, 2024

p1gp1g mentioned this pull request Aug 1, 2024

MSC3013: Encrypted Push #3013

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turt2live added push proposal A matrix spec change proposal client-server Client-Server API needs-implementation This MSC does not have a qualifying implementation for the SCT to review. The MSC cannot enter FCP. labels Aug 1, 2024

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Unified push endpoint: do not fallback to default endpoint in case of failure and add troubleshoot test. element-hq/element-x-android#3388

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Add capability and VAPID

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Add support for webpush pusher as defined in MSC4174 element-hq/hydrogen-web#1201

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MatMaul mentioned this pull request Dec 3, 2024

MSC4174: add support for WebPush pusher kind element-hq/synapse#17987

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p1gp1g mentioned this pull request Dec 13, 2024

Push notifications via unifiedpush don't work SchildiChat/schildichat-android-next#38

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uhoreg added implementation-needs-checking The MSC has an implementation, but the SCT has not yet checked it. and removed needs-implementation This MSC does not have a qualifying implementation for the SCT to review. The MSC cannot enter FCP. labels Dec 13, 2024

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UnifiedPush support ExteraApp/Extera#26

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mscbot added unresolved-concerns This proposal has at least one outstanding concern and removed unresolved-concerns This proposal has at least one outstanding concern labels Mar 11, 2026

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Co-authored-by: Andrew Morgan <[email protected]>

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Background synchronization / polling notification provider element-hq/element-x-android#4586

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Benjamin-Loison mentioned this pull request Mar 27, 2026

*Use UnifiedPush* purpose? Benjamin-Loison/firefox-android#96

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		@@ -0,0 +1,177 @@
		# MSC4174: Web push

		This MSC supersedes and replaces [MSC3013](https://github.com/matrix-org/matrix-spec-proposals/pull/3013), which introduced push notification encryption first.

		- Until this proposal is considered stable, implementations must use
		`org.matrix.msc4174.webpush` instead of `m.webpush`.

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p1gp1g commented Aug 1, 2024 •

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