[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

1 files changed, 140 insertions, 0 deletions

diff --git a/internal/middleware/tokencheck.go b/internal/middleware/tokencheck.go
new file mode 100644
index 000000000..ca93f379a
--- /dev/null
+++ b/internal/middleware/tokencheck.go
@@ -0,0 +1,140 @@
+/*
+   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 (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
+	"github.com/superseriousbusiness/oauth2/v4"
+)
+
+// TokenCheck returns a new gin middleware for validating oauth tokens in requests.
+//
+// The middleware checks the request Authorization header for a valid oauth Bearer token.
+//
+// If no token was set in the Authorization header, or the token was invalid, the handler will return.
+//
+// If a valid oauth Bearer token was provided, it will be set on the gin context for further use.
+//
+// Then, it will check which *gtsmodel.User the token belongs to. If the user is not confirmed, not approved,
+// or has been disabled, then the middleware will return early. Otherwise, the User will be set on the
+// gin context for further processing by other functions.
+//
+// Next, it will look up the *gtsmodel.Account for the User. If the Account has been suspended, then the
+// middleware will return early. Otherwise, it will set the Account on the gin context too.
+//
+// Finally, it will check the client ID of the token to see if a *gtsmodel.Application can be retrieved
+// for that client ID. This will also be set on the gin context.
+//
+// If an invalid token is presented, or a user/account/application can't be found, then this middleware
+// won't abort the request, since the server might want to still allow public requests that don't have a
+// Bearer token set (eg., for public instance information and so on).
+func TokenCheck(dbConn db.DB, validateBearerToken func(r *http.Request) (oauth2.TokenInfo, error)) func(*gin.Context) {
+	return func(c *gin.Context) {
+		ctx := c.Request.Context()
+
+		if c.Request.Header.Get("Authorization") == "" {
+			// no token set in the header, we can just bail
+			return
+		}
+
+		ti, err := validateBearerToken(c.Copy().Request)
+		if err != nil {
+			log.Debugf("token was passed in Authorization header but we could not validate it: %s", err)
+			return
+		}
+		c.Set(oauth.SessionAuthorizedToken, ti)
+
+		// check for user-level token
+		if userID := ti.GetUserID(); userID != "" {
+			log.Tracef("authenticated user %s with bearer token, scope is %s", userID, ti.GetScope())
+
+			// fetch user for this token
+			user, err := dbConn.GetUserByID(ctx, userID)
+			if err != nil {
+				if err != db.ErrNoEntries {
+					log.Errorf("database error looking for user with id %s: %s", userID, err)
+					return
+				}
+				log.Warnf("no user found for userID %s", userID)
+				return
+			}
+
+			if user.ConfirmedAt.IsZero() {
+				log.Warnf("authenticated user %s has never confirmed thier email address", userID)
+				return
+			}
+
+			if !*user.Approved {
+				log.Warnf("authenticated user %s's account was never approved by an admin", userID)
+				return
+			}
+
+			if *user.Disabled {
+				log.Warnf("authenticated user %s's account was disabled'", userID)
+				return
+			}
+
+			c.Set(oauth.SessionAuthorizedUser, user)
+
+			// fetch account for this token
+			if user.Account == nil {
+				acct, err := dbConn.GetAccountByID(ctx, user.AccountID)
+				if err != nil {
+					if err != db.ErrNoEntries {
+						log.Errorf("database error looking for account with id %s: %s", user.AccountID, err)
+						return
+					}
+					log.Warnf("no account found for userID %s", userID)
+					return
+				}
+				user.Account = acct
+			}
+
+			if !user.Account.SuspendedAt.IsZero() {
+				log.Warnf("authenticated user %s's account (accountId=%s) has been suspended", userID, user.AccountID)
+				return
+			}
+
+			c.Set(oauth.SessionAuthorizedAccount, user.Account)
+		}
+
+		// check for application token
+		if clientID := ti.GetClientID(); clientID != "" {
+			log.Tracef("authenticated client %s with bearer token, scope is %s", clientID, ti.GetScope())
+
+			// fetch app for this token
+			app := &gtsmodel.Application{}
+			if err := dbConn.GetWhere(ctx, []db.Where{{Key: "client_id", Value: clientID}}, app); err != nil {
+				if err != db.ErrNoEntries {
+					log.Errorf("database error looking for application with clientID %s: %s", clientID, err)
+					return
+				}
+				log.Warnf("no app found for client %s", clientID)
+				return
+			}
+			c.Set(oauth.SessionAuthorizedApplication, app)
+		}
+	}
+}