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V-258824

CAT II (Medium)

The Photon operating system must require authentication upon booting into single-user and maintenance modes.

Rule ID

SV-258824r933533_rule

STIG

VMware vSphere 8.0 vCenter Appliance Photon OS 4.0 Security Technical Implementation Guide

Version

V1R1

CCIs

CCI-000213

Discussion

If the system does not require authentication before it boots into single-user mode, anyone with console access to the system can trivially access all files on the system. GRUB2 is the boot loader for Photon OS and can be configured to require a password to boot into single-user mode or make modifications to the boot menu. Note: Photon does not support building grub changes via grub2-mkconfig.

Check Content

At the command line, run the following command to verify a password is required to edit the grub bootloader to boot into single-user mode:

# grep -E "^set\ssuperusers|^password_pbkdf2" /boot/grub2/grub.cfg

Example output:

set superusers="root"
password_pbkdf2 root grub.pbkdf2.sha512.[password_hash]

If superusers is not set, this is a finding.
If a password is not set for the super user, this is a finding.

Fix Text

Before proceeding, ensure a snapshot is taken to rollback if needed.

At the command line, run the following command to generate a grub password:

# grub2-mkpasswd-pbkdf2

Enter a secure password and ensure this password is stored for break-glass situations. Users will not be able to recover the root account without knowing this separate password. Copy the resulting encrypted string.

An example string is below:

grub.pbkdf2.sha512.10000.983A13DF3C51BB2B5130F0B86DDBF0DEA1AAF766BD1F16B7840F79CE3E35494C4B99F505C99C150071E563DF1D7FE1F45456D5960C4C79DAB6C49298B02A5558.5B2C49E12D43CC5A876F6738462DE4EFC24939D4BE486CDB72CFBCD87FDE93FBAFCB817E01B90F23E53C2502C3230502BC3113BE4F80B0AFC0EE956E735F7F86

Note: The grub2 package must be installed to generate a password for grub.

Navigate to and open:

/boot/grub2/grub.cfg

Find the line that begins with "set rootpartition". Below this line, paste the following on its own line:

set superusers="root"

Note: The superusers name can be a value other than root and is not tied to an OS account.

Below this paste the following, substituting the user's own encrypted string from the steps above:

password_pbkdf2 root <YOUR-LONG-STRING-FROM-ABOVE>

Next edit the default Photon menuentry block with the "--unrestricted" parameter so that it will continue to boot without prompting for credentials, for example:

menuentry "Photon" --unrestricted {
    linux /boot/$photon_linux root=$rootpartition $photon_cmdline $systemd_cmdline audit=1
    if [ -f /boot/$photon_initrd ]; then
        initrd /boot/$photon_initrd
    fi
}

When booting now, if users press "e" when the Photon splash screen appears, users will be prompted for credentials before being presented the option to edit the boot loader before system startup.

Note: Photon does not support building grub changes via grub2-mkconfig.