From 2c3caa7e176bc846a4b399c8b4a0bb67e48aa79c Mon Sep 17 00:00:00 2001
From: Peter Elliott <pelliott@ualberta.ca>
Date: Mon, 5 Sep 2022 22:10:46 -0600
Subject: [PATCH] LibCore: Create Core::SessionManagement for session
 management

---
 Userland/Libraries/LibCore/CMakeLists.txt     |  1 +
 .../Libraries/LibCore/SessionManagement.cpp   | 68 +++++++++++++++++++
 .../Libraries/LibCore/SessionManagement.h     | 20 ++++++
 3 files changed, 89 insertions(+)
 create mode 100644 Userland/Libraries/LibCore/SessionManagement.cpp
 create mode 100644 Userland/Libraries/LibCore/SessionManagement.h

diff --git a/Userland/Libraries/LibCore/CMakeLists.txt b/Userland/Libraries/LibCore/CMakeLists.txt
index a22ab5245f..704eb29f1f 100644
--- a/Userland/Libraries/LibCore/CMakeLists.txt
+++ b/Userland/Libraries/LibCore/CMakeLists.txt
@@ -26,6 +26,7 @@ set(SOURCES
     ProcessStatisticsReader.cpp
     Property.cpp
     SecretString.cpp
+    SessionManagement.cpp
     SOCKSProxyClient.cpp
     Stream.cpp
     StandardPaths.cpp
diff --git a/Userland/Libraries/LibCore/SessionManagement.cpp b/Userland/Libraries/LibCore/SessionManagement.cpp
new file mode 100644
index 0000000000..f6bdac93d7
--- /dev/null
+++ b/Userland/Libraries/LibCore/SessionManagement.cpp
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2022, Peter Elliott <pelliott@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/Directory.h>
+#include <LibCore/ProcessStatisticsReader.h>
+#include <LibCore/SessionManagement.h>
+#include <LibCore/System.h>
+
+namespace Core::SessionManagement {
+
+static ErrorOr<Core::ProcessStatistics const*> get_proc(Core::AllProcessesStatistics const& stats, pid_t pid)
+{
+    for (auto& proc : stats.processes) {
+        if (proc.pid == pid)
+            return &proc;
+    }
+    return Error::from_string_literal("Could not find pid in process statistics.");
+}
+
+ErrorOr<pid_t> root_session_id(Optional<pid_t> force_sid)
+{
+    auto stats = Core::ProcessStatisticsReader::get_all(false);
+    if (!stats.has_value())
+        return Error::from_string_literal("Failed to get all process statistics");
+
+    pid_t sid = (force_sid.has_value()) ? force_sid.value() : TRY(System::getsid());
+    while (true) {
+        pid_t parent = TRY(get_proc(stats.value(), sid))->ppid;
+        pid_t parent_sid = TRY(get_proc(stats.value(), parent))->sid;
+
+        if (parent_sid == 0)
+            break;
+
+        sid = parent_sid;
+    }
+
+    return sid;
+}
+
+ErrorOr<void> logout(Optional<pid_t> force_sid)
+{
+    pid_t sid = TRY(root_session_id(force_sid));
+    TRY(System::kill(-sid, SIGTERM));
+    return {};
+}
+
+ErrorOr<String> parse_path_with_sid(StringView general_path, Optional<pid_t> force_sid)
+{
+    if (general_path.contains("%sid"sv)) {
+        pid_t sid = TRY(root_session_id(force_sid));
+        return general_path.replace("%sid"sv, String::number(sid), ReplaceMode::All);
+    }
+    return String(general_path);
+}
+
+ErrorOr<void> create_session_temporary_directory_if_needed(uid_t uid, gid_t gid, Optional<pid_t> force_sid)
+{
+    pid_t sid = TRY(root_session_id(force_sid));
+    auto const temporary_directory = String::formatted("/tmp/session/{}", sid);
+    auto directory = TRY(Core::Directory::create(temporary_directory, Core::Directory::CreateDirectories::Yes));
+    TRY(directory.chown(uid, gid));
+    return {};
+}
+
+}
diff --git a/Userland/Libraries/LibCore/SessionManagement.h b/Userland/Libraries/LibCore/SessionManagement.h
new file mode 100644
index 0000000000..eb744a058a
--- /dev/null
+++ b/Userland/Libraries/LibCore/SessionManagement.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2022, Peter Elliott <pelliott@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Error.h>
+#include <AK/Types.h>
+
+namespace Core::SessionManagement {
+
+ErrorOr<pid_t> root_session_id(Optional<pid_t> force_sid = {});
+ErrorOr<void> logout(Optional<pid_t> force_sid = {});
+
+ErrorOr<String> parse_path_with_sid(StringView general_path, Optional<pid_t> force_sid = {});
+ErrorOr<void> create_session_temporary_directory_if_needed(uid_t uid, gid_t gid, Optional<pid_t> force_sid = {});
+
+}