Computer is not locked after suspend

[Nicholas Guriev]

Prerequisites:

1. Set up a password.

Steps to reproduce:

1. Click the gear wheel icon.
2. In the indicator menu, click "Suspend" item.

Expected behavior:

1. Computer goes to sleep mode.
2. After wake up, it is required to type the password to log in.

Actual behavior:

1. Computer goes to sleep mode.
2. After wake up, screen is not locked, it is possible to use session without the password.

Notes:

1. If a user suspend the system via shut down dialog box, the password is prompted.
2. The same vulnerability is present for hibernation mode if it is enabled.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: indicator-session 17.3.20+19.10.20190921-0ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-26.30-generic 5.4.30
Uname: Linux 5.4.0-26-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckMismatches: ./pool/restricted/n/nvidia-graphics-drivers-390/nvidia-kernel-source-390_390.132-0ubuntu2_amd64.deb
CasperMD5CheckResult: skip
CasperVersion: 1.445
CurrentDesktop: MATE
Date: Wed Jul 8 05:46:24 2020
LiveMediaBuild: Ubuntu-MATE 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
ProcEnviron:
 SHELL=/bin/bash
 LANG=C.UTF-8
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
 PATH=(custom, no user)
SourcePackage: indicator-session
UpgradeStatus: No upgrade log present (probably fresh install)