[chore] The Big Middleware and API Refactor (tm) (#1250)

* interim commit: start refactoring middlewares into package under router

* another interim commit, this is becoming a big job

* another fucking massive interim commit

* refactor bookmarks to new style

* ambassador, wiz zeze commits you are spoiling uz

* she compiles, we're getting there

* we're just normal men; we're just innocent men

* apiutil

* whoopsie

* i'm glad noone reads commit msgs haha :blob_sweat:

* use that weirdo go-bytesize library for maxMultipartMemory

* fix media module paths

internal/middleware/session.go

@@ -0,0 +1,95 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   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 middleware
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/gin-contrib/sessions"
+	"github.com/gin-contrib/sessions/memstore"
+	"github.com/gin-gonic/gin"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+	"golang.org/x/net/idna"
+)
+
+// SessionOptions returns the standard set of options to use for each session.
+func SessionOptions() sessions.Options {
+	var samesite http.SameSite
+	switch strings.TrimSpace(strings.ToLower(config.GetAdvancedCookiesSamesite())) {
+	case "lax":
+		samesite = http.SameSiteLaxMode
+	case "strict":
+		samesite = http.SameSiteStrictMode
+	default:
+		log.Warnf("%s set to %s which is not recognized, defaulting to 'lax'", config.AdvancedCookiesSamesiteFlag(), config.GetAdvancedCookiesSamesite())
+		samesite = http.SameSiteLaxMode
+	}
+
+	return sessions.Options{
+		Path:   "/",
+		Domain: config.GetHost(),
+		// 2 minutes
+		MaxAge: 120,
+		// only set secure over https
+		Secure: config.GetProtocol() == "https",
+		// forbid javascript from inspecting cookie
+		HttpOnly: true,
+		// https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-cookie-same-site-00#section-4.1.1
+		SameSite: samesite,
+	}
+}
+
+// SessionName is a utility function that derives an appropriate session name from the hostname.
+func SessionName() (string, error) {
+	// parse the protocol + host
+	protocol := config.GetProtocol()
+	host := config.GetHost()
+	u, err := url.Parse(fmt.Sprintf("%s://%s", protocol, host))
+	if err != nil {
+		return "", err
+	}
+
+	// take the hostname without any port attached
+	strippedHostname := u.Hostname()
+	if strippedHostname == "" {
+		return "", fmt.Errorf("could not derive hostname without port from %s://%s", protocol, host)
+	}
+
+	// make sure IDNs are converted to punycode or the cookie library breaks:
+	// see https://en.wikipedia.org/wiki/Punycode
+	punyHostname, err := idna.New().ToASCII(strippedHostname)
+	if err != nil {
+		return "", fmt.Errorf("could not convert %s to punycode: %s", strippedHostname, err)
+	}
+
+	return fmt.Sprintf("gotosocial-%s", punyHostname), nil
+}
+
+// Session returns a new gin middleware that implements session cookies using the given
+// sessionName, authentication key, and encryption key. Session name can be derived from the
+// SessionName utility function in this package.
+func Session(sessionName string, auth []byte, crypt []byte) gin.HandlerFunc {
+	store := memstore.NewStore(auth, crypt)
+	store.Options(SessionOptions())
+	return sessions.Sessions(sessionName, store)
+}