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Filename : update-secureboot-policy
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#!/bin/sh
set -e

if  test $# = 0                                                 \
    && test x"$SHIM_NOTRIGGER" = x                              \
 && test x"$DPKG_MAINTSCRIPT_PACKAGE" != x                      \
 && dpkg-trigger --check-supported 2>/dev/null
then
        if dpkg-trigger --no-await shim-secureboot-policy; then
                if test x"$SHIM_TRIGGER_DEBUG" != x; then
                        echo "shim: wrapper deferring policy update (trigger activated)"
                fi
                exit 0
        fi
fi

if [ "$(id -u)" -ne 0 ]; then
	echo "$0: Permission denied"
	exit 1
fi

do_enroll=0
do_toggle=0

efivars=/sys/firmware/efi/efivars
secureboot_var=SecureBoot-8be4df61-93ca-11d2-aa0d-00e098032b8c
moksbstatert_var=MokSBStateRT-605dab50-e046-4300-abb6-3dd810dd8b23

SB_KEY="/var/lib/shim-signed/mok/MOK.der"
SB_PRIV="/var/lib/shim-signed/mok/MOK.priv"

OLD_DKMS_LIST="/var/lib/shim-signed/dkms-list"
NEW_DKMS_LIST="${OLD_DKMS_LIST}.new"

touch $OLD_DKMS_LIST

dkms_list=$(find /var/lib/dkms -maxdepth 1 -type d -print 2>/dev/null \
            | LC_ALL=C sort)
dkms_modules=$(echo "$dkms_list" | wc -l)

. /usr/share/debconf/confmodule

update_dkms_list()
{
    echo "$dkms_list" > $NEW_DKMS_LIST
}

save_dkms_list()
{
    mv "$NEW_DKMS_LIST" "$OLD_DKMS_LIST"
}

clear_new_dkms_list()
{
    rm "$NEW_DKMS_LIST"
}

new_dkms_module()
{
    # handle nvidia module specially because it changed path
    if ! grep -q "/var/lib/dkms/nvidia" "$OLD_DKMS_LIST" && grep -q "/var/lib/dkms/nvidia" "$NEW_DKMS_LIST" ; then
        # nvidia module is newly added
        return 0
    fi

    # return 0 if there is any other new module
    env LC_ALL=C comm -1 -3 $OLD_DKMS_LIST $NEW_DKMS_LIST | grep -q -v "/var/lib/dkms/nvidia"
}

show_dkms_list_changes()
{
    diff -u $OLD_DKMS_LIST $NEW_DKMS_LIST >&2
}

validate_password()
{
    db_capb
    if [ "$key" != "$again" ]; then
        db_fset shim/error/secureboot_key_mismatch seen false
        db_input critical shim/error/secureboot_key_mismatch || true
        STATE=$(($STATE - 2))
    else
        length=$((`echo "$key" | wc -c` - 1))
        if [ $length -lt 8 ] || [ $length -gt 16 ]; then
            db_fset shim/error/bad_secureboot_key seen false
            db_input critical shim/error/bad_secureboot_key || true
            STATE=$(($STATE - 2))
        elif [ $length -ne 0 ]; then
            return 0
        fi
    fi

    return 1
}

clear_passwords()
{
    # Always clear secureboot key.
    db_set shim/secureboot_key ''
    db_fset shim/secureboot_key seen false
    db_set shim/secureboot_key_again ''
    db_fset shim/secureboot_key_again seen false
}

toggle_validation()
{
    local key="$1"
    local again="$2"

    echo "Enabling shim validation."
    printf '%s\n%s\n' "$key" "$again" | mokutil --enable-validation >/dev/null || true
    mokutil --timeout -1 >/dev/null || true
}

enroll_mok()
{
    local key="$1"
    local again="$2"

    echo "Adding '$SB_KEY' to shim:"
    printf '%s\n%s\n' "$key" "$again" | mokutil --import "$SB_KEY" >/dev/null || true
    mokutil --timeout -1 >/dev/null || true
}

do_it()
{
    STATE=1
    db_settitle shim/title/secureboot
    while true; do
        case "$STATE" in
        1)
            db_capb
            db_fset shim/secureboot_explanation seen false
            db_input critical shim/secureboot_explanation || true
            ;;
        2)
            if [ "$do_toggle" -eq 1 ]; then
                # Force no backtracking here; otherwise the GNOME backend
                # might allow it due to displaying the explanation just before.
                # Fixes LP: #1767091
                db_capb
                # Allow the user to skip toggling Secure Boot.
                db_fset shim/enable_secureboot seen false
                db_input critical shim/enable_secureboot || true
                db_go

                db_get shim/enable_secureboot
                if [ "$RET" = "false" ]; then
                    break
                fi
            fi
            ;;
        3)

            db_input critical shim/secureboot_key || true
            seen_key=$RET
            db_input critical shim/secureboot_key_again || true
            ;;
        4)
            db_get shim/secureboot_key
            key="$RET"
            db_get shim/secureboot_key_again
            again="$RET"

            if [ -z "$key$again" ] && echo "$seen_key" | grep -q ^30; then
                echo "Running in non-interactive mode, doing nothing." >&2

                if new_dkms_module; then
                    show_dkms_list_changes
                    clear_new_dkms_list
                    exit 1
                else
                    exit 0
                fi
            fi

            if validate_password; then
                if [ $do_toggle -eq 1 ]; then
                    toggle_validation "$key" "$again"
                fi
                if [ $do_enroll -eq 1 ]; then
                    enroll_mok "$key" "$again"
                fi
                save_dkms_list
            fi

            clear_passwords
            ;;
        *)
            break
            ;;
        esac

        if db_go; then
            STATE=$(($STATE + 1))
        else
            STATE=$(($STATE - 1))
        fi
        db_capb backup
    done
    db_capb
}

validate_actions() {
    # Validate any queued actions before we go try to do them.
    local moksbstatert=0

    if ! [ -d $efivars ]; then
        echo "$efivars not found, aborting." >&2
        exit 0
    fi

    if ! [ -f $efivars/$secureboot_var ] \
        || [ "$(od -An -t u1 $efivars/$secureboot_var | awk '{ print $NF }')" -ne 1 ]
    then
        echo "Secure Boot not enabled on this system." >&2
        exit 0
    fi

    if [ $dkms_modules -lt 2 ]; then
        echo "No DKMS modules installed." >&2
        exit 0
    fi

    if [ -f /proc/sys/kernel/moksbstate_disabled ]; then
        moksbstatert=$(cat /proc/sys/kernel/moksbstate_disabled 2>/dev/null || echo 0)
    elif [ -f $efivars/$moksbstatert_var ]; then
        # MokSBStateRT set to 1 means validation is disabled
        moksbstatert=$(od -An -t u1 $efivars/$moksbstatert_var | \
                       awk '{ print $NF; }')
    fi

    # We were asked to enroll a key. This only makes sense if validation
    # is enabled.
    if [ $do_enroll -eq 1 ] && [ $moksbstatert -eq 1 ]; then
        do_toggle=1
    fi
}

create_mok()
{
    if [ -e "$SB_KEY" ]; then
        return
    fi

    echo "Generating a new Secure Boot signing key:"
    openssl req -config /usr/lib/shim/mok/openssl.cnf \
        -subj "/CN=`hostname -s | cut -b1-31` Secure Boot Module Signature key" \
        -new -x509 -newkey rsa:2048 \
        -nodes -days 36500 -outform DER \
        -keyout "$SB_PRIV" \
        -out "$SB_KEY"
}

update_dkms_list

case "$1" in
'--enable'|'--disable')
    echo "Please run mokutil directly to change shim validation behavior."
    exit 0
    ;;

'--new-key')
    create_mok
    exit 0
    ;;

'--enroll-key')
    if [ -e "$SB_KEY" ]; then
        if mokutil --test-key "$SB_KEY" | \
                grep -qc 'is not'; then
            do_enroll=1
        fi
    else
        echo "No MOK found."
        exit 1
    fi
    ;;

*)
    echo "update-secureboot-policy: toggle UEFI Secure Boot in shim"
    echo
    echo "\t--new-key\tCreate a new MOK."
    echo "\t--enroll-key\tEnroll the new MOK for this system in shim."
    echo "\t--help\t\tThis help text."
    exit 0

esac

validate_actions

if [ $(($do_toggle + $do_enroll)) -lt 1 ]; then
    echo "Nothing to do."
    exit 0
fi

do_it

exit 0