From 783ae900cddb2098a4db575d6515a2ee1fee18c7 Mon Sep 17 00:00:00 2001
From: Andrew Morgan <andrew@amorgan.xyz>
Date: Fri, 19 Jul 2019 13:54:12 +0100
Subject: [PATCH] Correctly create new device when device_id is passed to
 /login

---
 .../auth/storage/devices/devices_table.go     |  2 ++
 clientapi/auth/storage/devices/storage.go     |  2 +-
 clientapi/routing/login.go                    | 21 ++++++++-----------
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/clientapi/auth/storage/devices/devices_table.go b/clientapi/auth/storage/devices/devices_table.go
index 96d6521d8..60aa563a2 100644
--- a/clientapi/auth/storage/devices/devices_table.go
+++ b/clientapi/auth/storage/devices/devices_table.go
@@ -169,6 +169,8 @@ func (s *devicesStatements) selectDeviceByToken(
 	return &dev, err
 }
 
+// selectDeviceByID retrieves a device from the database with the given user
+// localpart and deviceID
 func (s *devicesStatements) selectDeviceByID(
 	ctx context.Context, localpart, deviceID string,
 ) (*authtypes.Device, error) {
diff --git a/clientapi/auth/storage/devices/storage.go b/clientapi/auth/storage/devices/storage.go
index 7032fe7bf..82c8e97a2 100644
--- a/clientapi/auth/storage/devices/storage.go
+++ b/clientapi/auth/storage/devices/storage.go
@@ -84,7 +84,7 @@ func (d *Database) CreateDevice(
 	if deviceID != nil {
 		returnErr = common.WithTransaction(d.db, func(txn *sql.Tx) error {
 			var err error
-			// Revoke existing token for this device
+			// Revoke existing tokens for this device
 			if err = d.devices.deleteDevice(ctx, txn, *deviceID, localpart); err != nil {
 				return err
 			}
diff --git a/clientapi/routing/login.go b/clientapi/routing/login.go
index 2e2d409f6..01fb00dbe 100644
--- a/clientapi/routing/login.go
+++ b/clientapi/routing/login.go
@@ -18,7 +18,6 @@ import (
 	"net/http"
 
 	"context"
-	"database/sql"
 
 	"github.com/matrix-org/dendrite/clientapi/auth"
 	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
@@ -42,10 +41,12 @@ type flow struct {
 }
 
 type passwordRequest struct {
-	User               string  `json:"user"`
-	Password           string  `json:"password"`
+	User     string `json:"user"`
+	Password string `json:"password"`
+	// Both DeviceID and InitialDisplayName can be omitted, or empty strings ("")
+	// Thus a pointer is needed to differentiate between them two
 	InitialDisplayName *string `json:"initial_device_display_name"`
-	DeviceID           string  `json:"device_id"`
+	DeviceID           *string `json:"device_id"`
 }
 
 type loginResponse struct {
@@ -134,7 +135,7 @@ func Login(
 	}
 }
 
-// check if device exists else create one
+// getDevice returns a new or existing device
 func getDevice(
 	ctx context.Context,
 	r passwordRequest,
@@ -142,12 +143,8 @@ func getDevice(
 	acc *authtypes.Account,
 	localpart, token string,
 ) (dev *authtypes.Device, err error) {
-	dev, err = deviceDB.GetDeviceByID(ctx, localpart, r.DeviceID)
-	if err == sql.ErrNoRows {
-		// device doesn't exist, create one
-		dev, err = deviceDB.CreateDevice(
-			ctx, acc.Localpart, nil, token, r.InitialDisplayName,
-		)
-	}
+	dev, err = deviceDB.CreateDevice(
+		ctx, acc.Localpart, r.DeviceID, token, r.InitialDisplayName,
+	)
 	return
 }