From f467ebc933f28b1bed3cc3a72b4945524308f801 Mon Sep 17 00:00:00 2001
From: Lucas CHOLLET <lucas.chollet@free.fr>
Date: Thu, 9 Jun 2022 17:26:05 +0200
Subject: [PATCH] SystemServer: Detect spawning user for
 AcceptSocketConnections services

SystemServer now invokes services with the same uid as the process that
made the request.

This allows the superuser to have a normal GUI workflow. For example,
read and write its own files in TextEditor.
---
 Userland/Services/SystemServer/Service.cpp | 15 +++++++++++++++
 Userland/Services/SystemServer/Service.h   |  2 ++
 2 files changed, 17 insertions(+)

diff --git a/Userland/Services/SystemServer/Service.cpp b/Userland/Services/SystemServer/Service.cpp
index 6b93db32fc..babd700aa2 100644
--- a/Userland/Services/SystemServer/Service.cpp
+++ b/Userland/Services/SystemServer/Service.cpp
@@ -98,6 +98,8 @@ void Service::handle_socket_connection()
         }
 
         int accepted_fd = maybe_accepted_fd.release_value();
+        // FIXME: Propagate errors
+        MUST(determine_account(accepted_fd));
         spawn(accepted_fd);
         close(accepted_fd);
     } else {
@@ -401,3 +403,16 @@ bool Service::is_enabled() const
     extern String g_system_mode;
     return m_system_modes.contains_slow(g_system_mode);
 }
+
+ErrorOr<void> Service::determine_account(int fd)
+{
+    struct ucred creds = {};
+    socklen_t creds_size = sizeof(creds);
+    TRY(Core::System::getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &creds, &creds_size));
+
+    auto const directory_name = String::formatted("/proc/{}/", creds.pid);
+    auto const stat = TRY(Core::System::stat(directory_name.characters()));
+
+    m_account = TRY(Core::Account::from_uid(stat.st_uid));
+    return {};
+}
diff --git a/Userland/Services/SystemServer/Service.h b/Userland/Services/SystemServer/Service.h
index 2f21ef6298..42920cf2c8 100644
--- a/Userland/Services/SystemServer/Service.h
+++ b/Userland/Services/SystemServer/Service.h
@@ -33,6 +33,8 @@ private:
 
     void spawn(int socket_fd = -1);
 
+    ErrorOr<void> determine_account(int fd);
+
     /// SocketDescriptor describes the details of a single socket that was
     /// requested by a service.
     struct SocketDescriptor {