[feature] Push notifications (#3587)

* Update push subscription API model to be Mastodon 4.0 compatible

* Add webpush-go dependency

# Conflicts:
#	go.sum

* Single-row table for storing instance's VAPID key pair

* Generate VAPID key pair during startup

* Add VAPID public key to instance info API

* Return VAPID public key when registering an app

* Store Web Push subscriptions in DB

* Add Web Push sender (similar to email sender)

* Add no-op push senders to most processor tests

* Test Web Push notifications from workers

* Delete Web Push subscriptions when account is deleted

* Implement push subscription API

* Linter fixes

* Update Swagger

* Fix enum to int migration

* Fix GetVAPIDKeyPair

* Create web push subscriptions table with indexes

* Log Web Push server error messages

* Send instance URL as Web Push JWT subject

* Accept any 2xx code as a success

* Fix malformed VAPID sub claim

* Use packed notification flags

* Remove unused date columns

* Add notification type for update notifications

Not used yet

* Make GetVAPIDKeyPair idempotent

and remove PutVAPIDKeyPair

* Post-rebase fixes

* go mod tidy

* Special-case 400 errors other than 408/429

Most client errors should remove the subscription.

* Improve titles, trim body to reasonable length

* Disallow cleartext HTTP for Web Push servers

* Fix lint

* Remove redundant index on unique column

Also removes redundant unique and notnull tags on ID column since these are implied by pk

* Make realsender.go more readable

* Use Tobi's style for wrapping errors

* Restore treating all 5xx codes as temporary problems

* Always load target account settings

* Stub `policy` and `standard`

* webpush.Sender: take type converter as ctor param

* Move webpush.MockSender and noopSender into testrig

1 files changed, 284 insertions, 0 deletions

diff --git a/internal/api/client/push/pushsubscriptionpost.go b/internal/api/client/push/pushsubscriptionpost.go
new file mode 100644
index 000000000..a7e299894
--- /dev/null
+++ b/internal/api/client/push/pushsubscriptionpost.go
@@ -0,0 +1,284 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package push
+
+import (
+	"crypto/ecdh"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/url"
+
+	"github.com/gin-gonic/gin"
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
+)
+
+// PushSubscriptionPOSTHandler swagger:operation POST /api/v1/push/subscription pushSubscriptionPost
+//
+// Create a new Web Push subscription for the current access token, or replace the existing one.
+//
+//	---
+//	tags:
+//	- push
+//
+//	consumes:
+//	- application/json
+//	- application/x-www-form-urlencoded
+//
+//	produces:
+//	- application/json
+//
+//	parameters:
+//	-
+//		name: subscription[endpoint]
+//		in: formData
+//		type: string
+//		required: true
+//		minLength: 1
+//		description: The URL to which Web Push notifications will be sent.
+//	-
+//		name: subscription[keys][auth]
+//		in: formData
+//		type: string
+//		required: true
+//		minLength: 1
+//		description: The auth secret, a Base64 encoded string of 16 bytes of random data.
+//	-
+//		name: subscription[keys][p256dh]
+//		in: formData
+//		type: string
+//		required: true
+//		minLength: 1
+//		description: The user agent public key, a Base64 encoded string of a public key from an ECDH keypair using the prime256v1 curve.
+//	-
+//		name: data[alerts][follow]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when someone has followed you?
+//	-
+//		name: data[alerts][follow_request]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when someone has requested to follow you?
+//	-
+//		name: data[alerts][favourite]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a status you created has been favourited by someone else?
+//	-
+//		name: data[alerts][mention]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when someone else has mentioned you in a status?
+//	-
+//		name: data[alerts][reblog]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a status you created has been boosted by someone else?
+//	-
+//		name: data[alerts][poll]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a poll you voted in or created has ended?
+//	-
+//		name: data[alerts][status]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a subscribed account posts a status?
+//	-
+//		name: data[alerts][update]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a status you interacted with has been edited?
+//	-
+//		name: data[alerts][admin.sign_up]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a new user has signed up?
+//	-
+//		name: data[alerts][admin.report]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a new report has been filed?
+//	-
+//		name: data[alerts][pending.favourite]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a fave is pending?
+//	-
+//		name: data[alerts][pending.reply]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a reply is pending?
+//	-
+//		name: data[alerts][pending.reblog]
+//		in: formData
+//		type: boolean
+//		default: false
+//		description: Receive a push notification when a boost is pending?
+//
+//	security:
+//	- OAuth2 Bearer:
+//		- push
+//
+//	responses:
+//		'200':
+//			description: Web Push subscription for current access token.
+//			schema:
+//				"$ref": "#/definitions/webPushSubscription"
+//		'400':
+//			description: bad request
+//		'401':
+//			description: unauthorized
+//		'403':
+//			description: forbidden
+//		'404':
+//			description: not found
+//		'406':
+//			description: not acceptable
+//		'500':
+//			description: internal server error
+func (m *Module) PushSubscriptionPOSTHandler(c *gin.Context) {
+	authed, err := oauth.Authed(c, true, true, true, true)
+	if err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	if authed.Account.IsMoving() {
+		apiutil.ForbiddenAfterMove(c)
+		return
+	}
+
+	if _, err := apiutil.NegotiateAccept(c, apiutil.JSONAcceptHeaders...); err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	form := &apimodel.WebPushSubscriptionCreateRequest{}
+	if err := c.ShouldBind(form); err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	if err := validateNormalizeCreate(form); err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorUnprocessableEntity(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	apiSubscription, errWithCode := m.processor.Push().CreateOrReplace(c, authed.Account.ID, authed.Token.GetAccess(), form)
+	if errWithCode != nil {
+		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
+		return
+	}
+
+	apiutil.JSON(c, http.StatusOK, apiSubscription)
+}
+
+// validateNormalizeCreate checks subscription endpoint format and keys decodability,
+// and copies form fields to their canonical JSON equivalents.
+func validateNormalizeCreate(request *apimodel.WebPushSubscriptionCreateRequest) error {
+	if request.Subscription == nil {
+		request.Subscription = &apimodel.WebPushSubscriptionRequestSubscription{}
+	}
+
+	// Normalize and validate endpoint URL.
+	if request.SubscriptionEndpoint != nil {
+		request.Subscription.Endpoint = *request.SubscriptionEndpoint
+	}
+
+	if request.Subscription.Endpoint == "" {
+		return errors.New("endpoint is required")
+	}
+	endpointURL, err := url.Parse(request.Subscription.Endpoint)
+	if err != nil {
+		return errors.New("endpoint must be a valid URL")
+	}
+	if endpointURL.Scheme != "https" {
+		return errors.New("endpoint must be an https:// URL")
+	}
+	if endpointURL.Host == "" {
+		return errors.New("endpoint URL must have a host")
+	}
+	if endpointURL.Fragment != "" {
+		return errors.New("endpoint URL must not have a fragment")
+	}
+
+	// Normalize and validate auth secret.
+	if request.SubscriptionKeysAuth != nil {
+		request.Subscription.Keys.Auth = *request.SubscriptionKeysAuth
+	}
+
+	authBytes, err := base64DecodeAny("auth", request.Subscription.Keys.Auth)
+	if err != nil {
+		return err
+	}
+	if len(authBytes) != 16 {
+		return fmt.Errorf("auth must be 16 bytes long, got %d", len(authBytes))
+	}
+
+	// Normalize and validate public key.
+	if request.SubscriptionKeysP256dh != nil {
+		request.Subscription.Keys.P256dh = *request.SubscriptionKeysP256dh
+	}
+
+	p256dhBytes, err := base64DecodeAny("p256dh", request.Subscription.Keys.P256dh)
+	if err != nil {
+		return err
+	}
+	_, err = ecdh.P256().NewPublicKey(p256dhBytes)
+	if err != nil {
+		return fmt.Errorf("p256dh must be a valid public key on the NIST P-256 curve: %w", err)
+	}
+
+	return validateNormalizeUpdate(&request.WebPushSubscriptionUpdateRequest)
+}
+
+// base64DecodeAny tries decoding a string with standard and URL alphabets of Base64, with and without padding.
+func base64DecodeAny(name string, value string) ([]byte, error) {
+	encodings := []*base64.Encoding{
+		base64.StdEncoding,
+		base64.URLEncoding,
+		base64.RawStdEncoding,
+		base64.RawURLEncoding,
+	}
+
+	for _, encoding := range encodings {
+		if bytes, err := encoding.DecodeString(value); err == nil {
+			return bytes, nil
+		}
+	}
+
+	return nil, fmt.Errorf("%s is not valid Base64 data", name)
+}