From c7430ec403b133adea0336424f1ebebd539dce6b Mon Sep 17 00:00:00 2001
From: Andrew Morgan <andrewm@matrix.org>
Date: Mon, 4 Jun 2018 16:00:04 +0100
Subject: [PATCH] Prevent sql scanning into nil value in accounts_table

Signed-off-by: Andrew Morgan <andrewm@matrix.org>
---
 .../auth/storage/accounts/accounts_table.go   | 27 ++++++++++++++-----
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/accounts_table.go b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/accounts_table.go
index aaf6af39..7b7c997a 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/accounts_table.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/accounts_table.go
@@ -22,6 +22,8 @@ import (
 	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
 	"github.com/matrix-org/dendrite/clientapi/userutil"
 	"github.com/matrix-org/gomatrixserverlib"
+
+	log "github.com/sirupsen/logrus"
 )
 
 const accountsSchema = `
@@ -121,14 +123,27 @@ func (s *accountsStatements) selectPasswordHash(
 
 func (s *accountsStatements) selectAccountByLocalpart(
 	ctx context.Context, localpart string,
-) (acc *authtypes.Account, err error) {
+) (*authtypes.Account, error) {
+	var localpartPtr, appserviceIDPtr sql.NullString
+	var acc authtypes.Account
+
 	stmt := s.selectAccountByLocalpartStmt
-	err = stmt.QueryRowContext(ctx, localpart).Scan(&acc.Localpart, &acc.AppServiceID)
-	if err == nil {
-		acc.UserID = userutil.MakeUserID(localpart, s.serverName)
-		acc.ServerName = s.serverName
+	err := stmt.QueryRowContext(ctx, localpart).Scan(&localpartPtr, &appserviceIDPtr)
+	if err != nil {
+		log.WithError(err).Error("Unable to retrieve user from the db")
+		return nil, err
 	}
-	return
+	if appserviceIDPtr.Valid {
+		acc.AppServiceID = appserviceIDPtr.String
+	}
+	if localpartPtr.Valid {
+		acc.Localpart = localpartPtr.String
+	}
+
+	acc.UserID = userutil.MakeUserID(localpart, s.serverName)
+	acc.ServerName = s.serverName
+
+	return &acc, nil
 }
 
 func (s *accountsStatements) selectNewNumericLocalpart(