Determines whether the server supports SSLv2, what ciphers it supports and tests for CVE-2015-3197, CVE-2016-0703 and CVE-2016-0800 (DROWN)
See the documentation for the tls library.
See the documentation for the smbauth library.
See the documentation for the mssql library.
See the documentation for the smtp library.
See the documentation for the smb library.
See the documentation for the vulns library.
nmap -sV --script=sslv2-drown <target>
443/tcp open https
| sslv2-drown:
| ciphers:
| SSL2_DES_192_EDE3_CBC_WITH_MD5
| SSL2_IDEA_128_CBC_WITH_MD5
| SSL2_RC2_128_CBC_WITH_MD5
| SSL2_RC4_128_WITH_MD5
| SSL2_DES_64_CBC_WITH_MD5
| forced_ciphers:
| SSL2_RC2_128_CBC_EXPORT40_WITH_MD5
| SSL2_RC4_128_EXPORT40_WITH_MD5
| vulns:
| CVE-2016-0800:
| title: OpenSSL: Cross-protocol attack on TLS using SSLv2 (DROWN)
| state: VULNERABLE
| ids:
| CVE:CVE-2016-0800
| description:
| The SSLv2 protocol, as used in OpenSSL before 1.0.1s and 1.0.2 before 1.0.2g and
| other products, requires a server to send a ServerVerify message before establishing
| that a client possesses certain plaintext RSA data, which makes it easier for remote
| attackers to decrypt TLS ciphertext data by leveraging a Bleichenbacher RSA padding
| oracle, aka a "DROWN" attack.
|
| refs:
| https://www.openssl.org/news/secadv/20160301.txt
|_ https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-0800
local nmap = require "nmap"
local shortport = require "shortport"
local table = require "table"
local tableaux = require "tableaux"
local stdnse = require "stdnse"
local string = require "string"
local sslcert = require "sslcert"
local sslv2 = require "sslv2"
local vulns = require "vulns"
description = [[
Determines whether the server supports SSLv2, what ciphers it supports and tests for
CVE-2015-3197, CVE-2016-0703 and CVE-2016-0800 (DROWN)
]]
author = "Bertrand Bonnefoy-Claudet <[email protected]>"
license = "Same as Nmap--See https://nmap.org/book/man-legal.html"
-- We can use the set of ciphers detected by sslv2.nse to avoid 1 handshake
dependencies = {"sslv2"}
categories = {"intrusive", "vuln"}
---
-- @output
-- 443/tcp open https
-- | sslv2-drown:
-- | ciphers:
-- | SSL2_DES_192_EDE3_CBC_WITH_MD5
-- | SSL2_IDEA_128_CBC_WITH_MD5
-- | SSL2_RC2_128_CBC_WITH_MD5
-- | SSL2_RC4_128_WITH_MD5
-- | SSL2_DES_64_CBC_WITH_MD5
-- | forced_ciphers:
-- | SSL2_RC2_128_CBC_EXPORT40_WITH_MD5
-- | SSL2_RC4_128_EXPORT40_WITH_MD5
-- | vulns:
-- | CVE-2016-0800:
-- | title: OpenSSL: Cross-protocol attack on TLS using SSLv2 (DROWN)
-- | state: VULNERABLE
-- | ids:
-- | CVE:CVE-2016-0800
-- | description:
-- | The SSLv2 protocol, as used in OpenSSL before 1.0.1s and 1.0.2 before 1.0.2g and
-- | other products, requires a server to send a ServerVerify message before establishing
-- | that a client possesses certain plaintext RSA data, which makes it easier for remote
-- | attackers to decrypt TLS ciphertext data by leveraging a Bleichenbacher RSA padding
-- | oracle, aka a "DROWN" attack.
-- |
-- | refs:
-- | https://www.openssl.org/news/secadv/20160301.txt
-- |_ https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-0800
--
-- @xmloutput
-- <table key="ciphers">
-- <elem>SSL2_DES_192_EDE3_CBC_WITH_MD5</elem>
-- <elem>SSL2_IDEA_128_CBC_WITH_MD5</elem>
-- <elem>SSL2_RC2_128_CBC_WITH_MD5</elem>
-- <elem>SSL2_RC4_128_WITH_MD5</elem>
-- <elem>SSL2_DES_64_CBC_WITH_MD5</elem>
-- </table>
-- <table key="forced_ciphers">
-- <elem>SSL2_RC2_128_CBC_EXPORT40_WITH_MD5</elem>
-- <elem>SSL2_RC4_128_EXPORT40_WITH_MD5</elem>
-- </table>
-- <table key="vulns">
-- <table key="CVE-2016-0800">
-- <elem key="title">OpenSSL: Cross-protocol attack on TLS using SSLv2 (DROWN)</elem>
-- <elem key="state">VULNERABLE</elem>
-- <table key="ids">
-- <elem>CVE:CVE-2016-0800</elem>
-- </table>
-- <table key="description">
-- <elem>
-- The SSLv2 protocol, as used in OpenSSL before 1.0.1s and 1.0.2 before
-- 1.0.2g and other products, requires a server to send a ServerVerify
-- message before establishing that a client possesses certain plaintext
-- RSA data, which makes it easier for remote attackers to decrypt TLS
-- ciphertext data by leveraging a Bleichenbacher RSA padding oracle, aka
-- a "DROWN" attack.
-- </elem>
-- </table>
-- <table key="refs">
-- <elem>https://www.openssl.org/news/secadv/20160301.txt</elem>
-- <elem>https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-0800</elem>
-- </table>
-- </table>
-- </table>
-- Those ciphers are weak enough to enable a "General DROWN" attack.
local GENERAL_DROWN_CIPHERS = {}
for k, v in pairs(sslv2.SSL_CIPHERS) do
-- 40 bits or less, or single-DES (56 bits)
if v.encrypted_key_length <= 5 or v.str:find("DES_64") then
GENERAL_DROWN_CIPHERS[v.str] = true
end
end
portrule = function(host, port)
return shortport.ssl(host, port) or sslcert.getPrepareTLSWithoutReconnect(port)
end
-- Return whether all values of "t1" are also values in "t2".
local function values_in(t1, t2)
local set = {}
for _, e in pairs(t2) do
set[e] = true
end
for _, e in pairs(t1) do
if not set[e] then
return false
end
end
return true
end
-- Create a socket ready to begin an SSL negotiation and send client_hello
local function do_setup(host, port)
local timeout = stdnse.get_timeout(host, 10000, 5000)
local status, socket, err
local starttls = sslcert.getPrepareTLSWithoutReconnect(port)
if starttls then
status, socket = starttls(host, port)
if not status then
stdnse.debug(1, "Can't connect using STARTTLS: %s", socket)
return nil
end
else
socket = nmap.new_socket()
socket:set_timeout(timeout)
status, err = socket:connect(host, port)
if not status then
stdnse.debug(1, "Can't connect: %s", err)
return nil
end
end
socket:set_timeout(timeout)
socket:send(sslv2.client_hello(tableaux.keys(sslv2.SSL_CIPHER_CODES)))
local status, buffer = sslv2.record_buffer(socket)
if not status then
socket:close()
return false
end
return socket, buffer
end
local function try_force_cipher(host, port, cipher)
local socket, buffer = do_setup(host, port)
if not socket then
return false
end
local i, server_hello = sslv2.record_read(buffer)
local code = sslv2.SSL_CIPHER_CODES[cipher]
local key_length = sslv2.SSL_CIPHERS[code].key_length
local encrypted_key_length = sslv2.SSL_CIPHERS[code].encrypted_key_length
local dummy_key = string.rep("\0", key_length)
local clear_key = dummy_key:sub(1, key_length - encrypted_key_length)
local encrypted_key = dummy_key:sub(key_length - encrypted_key_length + 1)
local dummy_client_master_key = sslv2.client_master_secret(cipher, clear_key, encrypted_key)
socket:send(dummy_client_master_key)
local status, buffer = sslv2.record_buffer(socket, buffer, i)
socket:close()
if not status then
return false
end
local i, message = sslv2.record_read(buffer, i)
-- Treat an error as a failure to force the cipher.
if not message or message.message_type == sslv2.SSL_MESSAGE_TYPES.ERROR then
return false
end
return true
end
local function has_extra_clear_bug(host, port, cipher)
local socket, buffer = do_setup(host, port)
if not socket then
return false
end
local i, server_hello = sslv2.record_read(buffer)
local code = sslv2.SSL_CIPHER_CODES[cipher]
local key_length = sslv2.SSL_CIPHERS[code].key_length
local encrypted_key_length = sslv2.SSL_CIPHERS[code].encrypted_key_length
-- The length of clear_key is intentionally wrong to highlight the bug.
local clear_key = string.rep("\0", key_length - encrypted_key_length + 1)
local encrypted_key = string.rep("\0", encrypted_key_length)
local dummy_client_master_key = sslv2.client_master_secret(cipher, clear_key, encrypted_key)
socket:send(dummy_client_master_key)
local status, buffer, err = sslv2.record_buffer(socket, buffer, i)
socket:close()
if not status then
return false
end
local i, message = sslv2.record_read(buffer, i)
-- Treat an error as a failure to force the cipher.
if not message or message.message_type == sslv2.SSL_MESSAGE_TYPES.ERROR then
return false
end
return true
end
local function registry_get(host, port)
if host.registry.sslv2 then
return host.registry.sslv2[port.number .. port.protocol]
end
end
local function unique (t)
local tc = {};
for k,v in ipairs(t) do
tc[v] = true;
end
return tc;
end
function action(host, port)
local output = stdnse.output_table()
local report = vulns.Report:new("sslv2-drown", host, port)
local cve_2015_3197 = {
title = "OpenSSL: SSLv2 doesn't block disabled ciphers",
state = vulns.STATE.NOT_VULN,
IDS = {
CVE = 'CVE-2015-3197',
},
risk_factor = "Low",
description = [[
ssl/s2_srvr.c in OpenSSL 1.0.1 before 1.0.1r and 1.0.2 before 1.0.2f does not
prevent use of disabled ciphers, which makes it easier for man-in-the-middle
attackers to defeat cryptographic protection mechanisms by performing computations
on SSLv2 traffic, related to the get_client_master_key and get_client_hello
functions.
]],
references = {
"https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-3197",
"https://www.openssl.org/news/secadv/20160128.txt",
},
}
local cve_2016_0703 = {
title = "OpenSSL: Divide-and-conquer session key recovery in SSLv2",
state = vulns.STATE.NOT_VULN,
IDS = {
CVE = 'CVE-2016-0703',
},
risk_factor = "High",
description = [[
The get_client_master_key function in s2_srvr.c in the SSLv2 implementation in
OpenSSL before 0.9.8zf, 1.0.0 before 1.0.0r, 1.0.1 before 1.0.1m, and 1.0.2 before
1.0.2a accepts a nonzero CLIENT-MASTER-KEY CLEAR-KEY-LENGTH value for an arbitrary
cipher, which allows man-in-the-middle attackers to determine the MASTER-KEY value
and decrypt TLS ciphertext data by leveraging a Bleichenbacher RSA padding oracle, a
related issue to CVE-2016-0800.
]],
references = {
"https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-0703",
"https://www.openssl.org/news/secadv/20160301.txt",
},
}
local cve_2016_0800 = {
title = "OpenSSL: Cross-protocol attack on TLS using SSLv2 (DROWN)",
state = vulns.STATE.NOT_VULN,
IDS = {
CVE = 'CVE-2016-0800',
},
risk_factor = "High",
description = [[
The SSLv2 protocol, as used in OpenSSL before 1.0.1s and 1.0.2 before 1.0.2g and
other products, requires a server to send a ServerVerify message before establishing
that a client possesses certain plaintext RSA data, which makes it easier for remote
attackers to decrypt TLS ciphertext data by leveraging a Bleichenbacher RSA padding
oracle, aka a "DROWN" attack.
]],
references = {
"https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-0800",
"https://www.openssl.org/news/secadv/20160301.txt",
},
}
local offered_ciphers = registry_get(host, port) or sslv2.test_sslv2(host, port)
if not offered_ciphers then
output.vulns = report:make_output()
if (#output > 0) then
return output
else
return nil
end
end
if next(offered_ciphers) then
output.ciphers = offered_ciphers
end
-- CVE-2015-3197
local forced_ciphers = {}
local all_ciphers = unique(offered_ciphers)
for cipher, code in pairs(sslv2.SSL_CIPHER_CODES) do
if not all_ciphers[cipher] and try_force_cipher(host, port, cipher) then
all_ciphers[cipher] = true
table.insert(forced_ciphers, cipher)
end
end
if next(forced_ciphers) then
output.forced_ciphers = forced_ciphers
cve_2015_3197.state = vulns.STATE.VULN
end
-- CVE-2016-0703
local cipher, _ = next(all_ciphers)
local result = has_extra_clear_bug(host, port, cipher)
if result then
cve_2016_0703.state = vulns.STATE.VULN
end
-- CVE-2016-0800
local has_weak_ciphers = false
for cipher, _ in pairs(all_ciphers) do
if GENERAL_DROWN_CIPHERS[cipher] then
has_weak_ciphers = true
break
end
end
if has_weak_ciphers or cve_2016_0703.state == vulns.STATE.VULN then
cve_2016_0800.state = vulns.STATE.VULN
end
report:add_vulns(cve_2015_3197)
report:add_vulns(cve_2016_0703)
report:add_vulns(cve_2016_0800)
output.vulns = report:make_output()
if (#output > 0) then
return output
end
end