lynis/include/tests_ssh

#!/bin/sh

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#
#   Lynis
# ------------------
#
# Copyright 2007-2013, Michael Boelen
# Copyright 2013-2016, CISOfy
#
# Website  : https://cisofy.com
# Blog     : http://linux-audit.com
# GitHub   : https://github.com/CISOfy/lynis
#
# Lynis comes with ABSOLUTELY NO WARRANTY. This is free software, and you are
# welcome to redistribute it under the terms of the GNU General Public License.
# See LICENSE file for usage of this software.
#
#################################################################################
#
# SSH
#
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#
    SSH_DAEMON_CONFIG_LOCS="/etc /etc/ssh /usr/local/etc/ssh /opt/csw/etc/ssh"
    SSH_DAEMON_CONFIG=""
    SSH_DAEMON_PORT=""
    SSH_DAEMON_RUNNING=0
    SSH_DAEMON_OPTIONS_FILE=""
#
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#
    InsertSection "SSH Support"
#
#################################################################################
#
    # Test        : SSH-7402
    # Description : Check for a running SSH daemon
    Register --test-no SSH-7402 --weight L --network NO --description "Check for running SSH daemon"
    if [ ${SKIPTEST} -eq 0 ]; then
        LogText "Test: Searching for a SSH daemon"
        IsRunning sshd
        if [ ${RUNNING} -eq 1 ] || PortIsListening "TCP" 22; then
            SSH_DAEMON_RUNNING=1
            Display --indent 2 --text "- Checking running SSH daemon" --result "${STATUS_FOUND}" --color GREEN
            # Store settings in a temporary file
            CreateTempFile
            SSH_DAEMON_OPTIONS_FILE="${TEMP_FILE}"
            ${SSHDBINARY} -T 2> /dev/null > ${SSH_DAEMON_OPTIONS_FILE}
          else
            Display --indent 2 --text "- Checking running SSH daemon" --result "${STATUS_NOT_FOUND}" --color WHITE
        fi
    fi
#
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#
    # Test        : SSH-7404
    # Description : Determine SSH daemon configuration file location
    if [ ${SSH_DAEMON_RUNNING} -eq 1 ]; then PREQS_MET="YES"; else PREQS_MET="NO"; fi
    Register --test-no SSH-7404 --preqs-met ${PREQS_MET} --weight L --network NO --description "Check SSH daemon file location"
    if [ ${SKIPTEST} -eq 0 ]; then
        FOUND=0
        LogText "Test: searching for sshd_config file"
        for I in ${SSH_DAEMON_CONFIG_LOCS}; do
            if [ -f "${I}/sshd_config" ]; then
              LogText "Result: ${I}/sshd_config exists"
              if [ ${FOUND} -eq 1 ]; then
                  ReportException "${TEST_NO}:01"
                  LogText "Result: we already had found another sshd_config file. Using this new file then."
              fi
              FileIsReadable ${I}/sshd_config
              if [ ${CANREAD} -eq 1 ]; then
                  FOUND=1
                  SSH_DAEMON_CONFIG="${I}/sshd_config"
                else
                  LogText "Result: can not read ${I}/sshd_config file (no permission)"
              fi
            fi
        done
        if [ "${SSH_DAEMON_CONFIG}" = "" ]; then
            LogText "Result: No sshd configuration found"
            Display --indent 4 --text "- Searching SSH configuration" --result "${STATUS_NOT_FOUND}" --color YELLOW
            ReportException "${TEST_NO}:1" "SSH daemon is running, but no readable configuration file found"
          else
            LogText "Result: using last found configuration file: ${SSH_DAEMON_CONFIG}"
            Display --indent 4 --text "- Searching SSH configuration" --result "${STATUS_FOUND}" --color GREEN
        fi
    fi
#
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#
    # Test        : SSH-7408
    # Description : Check SSH specific defined options
    # Notes       : Instead of parsing the configuration file, we query the SSH daemon itself
    if [ ${SSH_DAEMON_RUNNING} -eq 1 -a ! "${SSH_DAEMON_OPTIONS_FILE}" = "" ]; then PREQS_MET="YES"; else PREQS_MET="NO"; fi
    Register --test-no SSH-7408 --preqs-met ${PREQS_MET} --weight L --network NO --description "Check SSH specific defined options"
    if [ ${SKIPTEST} -eq 0 ]; then
        LogText "Test: Checking specific defined options in ${SSH_DAEMON_OPTIONS_FILE}"
        ## SSHOPTIONS scheme:
        ##      <OptionName>:<ExpectedValue>,<MediumScoreValue>,<WeakValue>:<TestType>
        ##
        ##      Test types:
        ##      (a) '='         -- equal to is better,
        ##      (b) '<'         -- less or equal is better,
        ##      (c) '>'         -- more or equal is better,
        ##      (d) '!'         -- not equal is better.
        ##
        ##      Example:
        ##      PermitRootLogin:NO,WITHOUT-PASSWORD,YES,:=
        SSHOPS="AllowTcpForwarding:NO,LOCAL,YES:=\
                ClientAliveCountMax:2,4,16:<\
                ClientAliveInterval:300,600,900:<\
                Compression:NO,DELAYED,YES:=\
                FingerprintHash:SHA256,MD5,:=\
                GatewayPorts:NO,,YES:=\
                IgnoreRhosts:YES,,NO:=\
                LoginGraceTime:120,240,480:<\
                LogLevel:VERBOSE,INFO,:=\
                MaxAuthTries:1,3,6:<\
                MaxSessions:2,4,8:<\
                PermitRootLogin:NO,WITHOUT-PASSWORD,YES:=\
                PermitUserEnvironment:NO,,YES:=\
                PermitTunnel:NO,,YES:=\
                Port:,,22:!\
                PrintLastLog:YES,,NO:=\
                Protocol:2,,1:=\
                StrictModes:YES,,NO:=\
                TCPKeepAlive:NO,,YES:=\
                UseDNS:NO,,YES:=\
                UsePrivilegeSeparation:SANDBOX,YES,NO:=\
                VerifyReverseMapping:YES,,NO:=\
                X11Forwarding:NO,,YES:="

        # Disabled        MaxStartups:4,8,16:<\ (needs fixing)

        # Go through our list of options
        for I in ${SSHOPS}; do
            OPTIONNAME=`echo ${I} | cut -d ':' -f1`
            OPTIONNAME_LOWER=`echo ${I} | cut -d ':' -f1 | awk '{ print tolower($1) }'`
            EXPECTEDVALUE=`echo ${I} | cut -d ':' -f2 | cut -d',' -f1`
            MEDIUMSCOREDVALUE=`echo ${I} | cut -d ':' -f2 | cut -d',' -f2`
            WEAKVALUE=`echo ${I} | cut -d ':' -f2 | cut -d',' -f3`
            TESTTYPE=`echo ${I} | cut -d ':' -f3`
            RESULT="NONE"

            if ! SkipAtomicTest "${TEST_NO}:${OPTIONNAME_LOWER}"; then

                # Get value and use the last occurrence
                FOUNDVALUE=`awk -v OPT="${OPTIONNAME_LOWER}" 'index($0, OPT) == 1 { print toupper($2) }' ${SSH_DAEMON_OPTIONS_FILE} | tail -1`
                LogText "Test: Checking ${OPTIONNAME} in ${SSH_DAEMON_OPTIONS_FILE}"

                if [ ! "${FOUNDVALUE}" = "" ]; then
                    LogText "Result: Option ${OPTIONNAME} found"
                    LogText "Result: Option ${OPTIONNAME} value is ${FOUNDVALUE}"

                    if [ "${TESTTYPE}" = "=" ]; then
                        if [ "${FOUNDVALUE}" = "${EXPECTEDVALUE}" ]; then
                            RESULT="GOOD"
                        elif [ "${FOUNDVALUE}" = "${MEDIUMSCOREDVALUE}" ]; then
                            RESULT="MIDSCORED"
                        elif [ "${FOUNDVALUE}" = "${WEAKVALUE}" ]; then
                            RESULT="WEAK"
                        else
                            RESULT="UNKNOWN"
                        fi

                    elif [ "${TESTTYPE}" = "<" ]; then
                        if [ "${FOUNDVALUE}" -ge "${WEAKVALUE}" -o "${FOUNDVALUE}" -gt "${MEDIUMSCOREDVALUE}" ]; then
                            RESULT="WEAK"
                        elif [ "${FOUNDVALUE}" -le "${MEDIUMSCOREDVALUE}" -a "${FOUNDVALUE}" -gt "${EXPECTEDVALUE}" ]; then
                            RESULT="MIDSCORED"
                        elif [ "${FOUNDVALUE}" -le "${EXPECTEDVALUE}" ]; then
                            RESULT="GOOD"
                        else
                            RESULT="UNKNOWN"
                        fi

                    elif [ "${TESTTYPE}" = ">" ]; then
                        if [ "${FOUNDVALUE}" -le "${WEAKVALUE}" ]; then
                            RESULT="WEAK"
                        elif [ "${FOUNDVALUE}" -le "${WEAKVALUE}" -a "${FOUNDVALUE}" -ge "${MEDIUMSCOREDVALUE}" ]; then
                            RESULT="MIDSCORED"
                        elif [ "${FOUNDVALUE}" -ge "${EXPECTEDVALUE}" ]; then
                            RESULT="GOOD"
                        else
                            RESULT="UNKNOWN"
                        fi

                    elif [ "${TESTTYPE}" = "!" ]; then
                        if [ "${FOUNDVALUE}" = "${WEAKVALUE}" ]; then
                            RESULT="WEAK"
                        elif [ ! "${FOUNDVALUE}" = "${WEAKVALUE}" ]; then
                            RESULT="GOOD"
                        else
                            RESULT="UNKNOWN"
                        fi

                    else
                        RESULT="NONE"
                    fi
                fi

                if [ "${RESULT}" = "GOOD" ]; then
                    LogText "Result: SSH option ${OPTIONNAME} is configured very well"
                    Display --indent 4 --text "- SSH option: ${OPTIONNAME}" --result "${STATUS_OK}" --color GREEN
                    AddHP 3 3
                elif [ "${RESULT}" = "MIDSCORED" ]; then
                    LogText "Result: SSH option ${OPTIONNAME} is configured reasonably"
                    ReportSuggestion ${TEST_NO} "Consider hardening SSH configuration" "${OPTIONNAME} (${FOUNDVALUE} --> ${EXPECTEDVALUE})" "-"
                    ReportDetails --test "${TEST_NO}" --service "sshd" --field "${OPTIONNAME}" --value "${FOUNDVALUE}" --preferredvalue "${EXPECTEDVALUE}" --description "sshd option ${OPTIONNAME}"
                    Display --indent 4 --text "- SSH option: ${OPTIONNAME}" --result "${STATUS_SUGGESTION}" --color YELLOW
                    AddHP 1 3
                elif [ "${RESULT}" = "WEAK" ]; then
                    LogText "Result: SSH option ${OPTIONNAME} is in a weak configuration state and should be fixed"
                    ReportSuggestion ${TEST_NO} "Consider hardening SSH configuration" "${OPTIONNAME} (${FOUNDVALUE} --> ${EXPECTEDVALUE})" "-"
                    ReportDetails --test "${TEST_NO}" --service "sshd" --field "${OPTIONNAME}" --value "${FOUNDVALUE}" --preferredvalue "${EXPECTEDVALUE}" --description "sshd option ${OPTIONNAME}"
                    Display --indent 4 --text "- SSH option: ${OPTIONNAME}" --result "${STATUS_SUGGESTION}" --color YELLOW
                    AddHP 0 3
                elif [ "${RESULT}" = "UNKNOWN" ]; then
                    LogText "Result: Value of SSH option ${OPTIONNAME} is unknown (not defined)"
                    Display --indent 4 --text "- SSH option: ${OPTIONNAME}" --result DEFAULT --color WHITE
                    Report "unknown_config_option[]=ssh|$SSH_DAEMON_CONFIG}|${OPTIONNAME}|"
                else
                    LogText "Result: Option ${OPTIONNAME} not found in output"
                    Display --indent 4 --text "- SSH option: ${OPTIONNAME}" --result "${STATUS_NOT_FOUND}" --color WHITE
                fi
              else
                if IsVerbose; then Display --indent 4 --text "- SSH option: ${OPTIONNAME}" --result "SKIPPED (via config)" --color WHITE; fi
            fi
        done
    fi
#
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#
    # Test        : SSH-7440
    # Description : AllowUsers / AllowGroups
    # Goal        : Check if only a specific amount of users/groups can log in to the system
    if [ ${SSH_DAEMON_RUNNING} -eq 1 -a ! "${SSH_DAEMON_OPTIONS_FILE}" = "" ]; then PREQS_MET="YES"; else PREQS_MET="NO"; fi
    Register --test-no SSH-7440 --preqs-met ${PREQS_MET} --weight L --network NO --description "Check SSH option: AllowUsers and AllowGroups"
    if [ ${SKIPTEST} -eq 0 ]; then
        FOUND=0
        # AllowUsers
        FIND=`egrep -i "^AllowUsers" ${SSH_DAEMON_OPTIONS_FILE} | awk '{ print $2 }'`
        if [ ! "${FIND}" = "" ]; then
            LogText "Result: AllowUsers set, with value ${FIND}"
            Display --indent 4 --text "- SSH option: AllowUsers" --result "${STATUS_FOUND}" --color GREEN
            FOUND=1
          else
            LogText "Result: AllowUsers is not set"
            Display --indent 4 --text "- SSH option: AllowUsers" --result "${STATUS_NOT_FOUND}" --color WHITE
        fi

        # AllowGroups
        FIND=`egrep -i "^AllowGroups" ${SSH_DAEMON_OPTIONS_FILE} | awk '{ print $2 }'`
        if [ ! "${FIND}" = "" ]; then
            LogText "Result: AllowUsers set ${FIND}"
            Display --indent 4 --text "- SSH option: AllowGroups" --result "${STATUS_FOUND}" --color GREEN
            FOUND=1
          else
            LogText "Result: AllowGroups is not set"
            Display --indent 4 --text "- SSH option: AllowGroups" --result "${STATUS_NOT_FOUND}" --color WHITE
        fi

        if [ ${FOUND} -eq 1 ]; then
            LogText "Result: SSH is limited to a specific set of users, which is good"
            AddHP 2 2
          else
            LogText "Result: SSH has no specific user or group limitation. Most likely all valid users can SSH to this machine."
            AddHP 0 1
        fi
    fi
#
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#

Report "ssh_daemon_running=${SSH_DAEMON_RUNNING}"
#Report "ssh_daemon_port=${SSH_DAEMON_PORT}"

WaitForKeyPress

#
#================================================================================
# Lynis - Security Auditing and System Hardening for Linux and UNIX - https://cisofy.com