lynis/plugins/plugin_krb5_phase1

#!/bin/sh

#########################################################################
#
#    * DO NOT REMOVE *
#-----------------------------------------------------
# PLUGIN_AUTHOR="pyllyukko"
# PLUGIN_CATEGORY=security
# PLUGIN_DATE=2024-02-14
# PLUGIN_DESC=Kerberos
# PLUGIN_NAME=krb5
# PLUGIN_REQUIRED_TESTS=
# PLUGIN_VERSION=0.2
#-----------------------------------------------------
#
#########################################################################
#

    # Test for the prerequisites first
    if [ -n "${KADMINLOCALBINARY}" ] && [ -n "${KDB5UTILBINARY}" ]
    then
        PREQS_MET="YES"
        # Make sure krb5 debugging doesn't mess up the output
        unset KRB5_TRACE
        PRINCS="$(${KADMINLOCALBINARY} listprincs | ${TRBINARY:-tr} '\n' ' ')"
        if [ -z "${PRINCS}" ]
        then
            PREQS_MET="NO"
        fi
    else
        PREQS_MET="NO"
    fi

    # Test        : KRB5-0001
    # Description : Check that Kerberos principals have passwords that expire
    Register --test-no KRB5-0001 --preqs-met ${PREQS_MET} --weight L --network NO --description "Check that Kerberos principals have passwords that expire" --progress
    if [ ${SKIPTEST} -eq 0 ]; then
        for I in ${PRINCS}
        do
            FIND="$(${KADMINLOCALBINARY} getprinc "${I}" | ${GREPBINARY} '^Password expiration date:')"
            if [ "${FIND}" = "Password expiration date: [never]" ]
            then
                LogText "Result: Kerberos principal ${I} has a password/key that never expires"
            fi
        done
    fi
#
#################################################################################
#

    # Test        : KRB5-0002
    # Description : Check last password change for Kerberos principals
    Register --test-no KRB5-0002 --preqs-met ${PREQS_MET} --weight L --network NO --description "Check last password change for Kerberos principals" --progress
    if [ ${SKIPTEST} -eq 0 ]; then
        for I in ${PRINCS}
        do
            FIND="$(${KADMINLOCALBINARY} getprinc "${I}" | ${SEDBINARY} -n '/^Last password change:\s\+/s/^Last password change:\s\+//p')"
            if [ "${FIND}" = "[never]" ]
            then
                LogText "Result: Kerberos principal ${I} has a password/key that has never been changed"
            else
                J="$(date -d "${FIND}" +%s)"
                if [ ${J} -lt $((NOW - 60 * 60 * 24 * 365)) ]
                then
                    LogText "Result: Kerberos principal ${I} has had a password/key change over a year ago"
                fi
            fi
        done
    fi

#
#################################################################################
#

    # Test        : KRB5-0003
    # Description : Check that Kerberos principals have a policy associated to them
    Register --test-no KRB5-0003 --preqs-met ${PREQS_MET} --weight L --network NO --description "Check that Kerberos principals have a policy associated to them" --progress
    if [ ${SKIPTEST} -eq 0 ]; then
        for I in ${PRINCS}
        do
            FIND="$(${KADMINLOCALBINARY} getprinc "${I}" | ${GREPBINARY} '^Policy:')"
            if [ "${FIND}" = "Policy: [none]" ]
            then
                LogText "Result: Kerberos principal ${I} does not have a policy associated to it"
            fi
        done
    fi

#
#################################################################################
#

    # Test        : KRB5-0004
    # Description : Check various attributes for Kerberos principals
    Register --test-no KRB5-0004 --preqs-met ${PREQS_MET} --weight L --network NO --description "Check various attributes for Kerberos principals" --progress
    if [ ${SKIPTEST} -eq 0 ]; then
        for I in ${PRINCS}
        do
            J="$(${KADMINLOCALBINARY} getprinc "${I}" | ${SEDBINARY} -n 's/^Attributes:\s\+\(.\+\)$/\1/p')"
            if ContainsString "^K/M@" "${I}" || \
                ContainsString "^kadmin/admin@" "${I}" || \
                ContainsString "^kadmin/changepw@" "${I}" || \
                ContainsString "^krbtgt/" "${I}"
            then
                if ! ContainsString "\bLOCKDOWN_KEYS\b" "${J}"
                then
                    LogText "Result: Sensitive Kerberos principal ${I} does not have the lockdown_keys attribute"
                fi
            elif ContainsString "/admin@" "${I}"
            then
                if ! ContainsString "\bDISALLOW_TGT_BASED\b" "${J}"
                then
                    LogText "Result: Kerberos admin principal ${I} does not have the disallow_tgt_based attribute"
                fi
            elif ContainsString "^[^/$]+@" "${I}"
            then
                if ! ContainsString "\bREQUIRES_PRE_AUTH\b.+\bDISALLOW_SVR\b" "${J}"
                then
                    LogText "Result: Regular Kerberos user principal ${I} does not have the requires_pre_auth and/or the disallow_svr attribute"
                fi
            fi
        done
    fi

#
#################################################################################
#

    # Test        : KRB5-0005
    # Description : Check for weak crypto
    Register --test-no KRB5-0005 --preqs-met ${PREQS_MET} --weight L --network NO --description "Check for weak crypto" --progress
    if [ ${SKIPTEST} -eq 0 ]; then
        FIND=$(${KDB5UTILBINARY} tabdump keyinfo | ${AWKBINARY} '$4 ~ /(des|arcfour|cbc|sha1)/{print$1,$4}')
        while read I J
        do
            LogText "Result: Kerberos principal ${I} has a key with weak cryptographic algorithm ${J}"
        done << EOF
${FIND}
EOF
    fi

#
#################################################################################
#

unset PRINCS
unset I
unset J

#EOF