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local nmap = require "nmap"
local shortport = require "shortport"
local string = require "string"
local table = require "table"
local bin = require "bin"
local stdnse = require "stdnse"
description = [[
Determines whether the server supports obsolete and less secure SSLv2, and discovers which ciphers it
supports.
]]
---
--@output
-- 443/tcp open https syn-ack
-- | sslv2:
-- | SSLv2 supported
-- | ciphers:
-- | SSL2_DES_192_EDE3_CBC_WITH_MD5
-- | SSL2_IDEA_128_CBC_WITH_MD5
-- | SSL2_RC2_CBC_128_CBC_WITH_MD5
-- | SSL2_RC4_128_WITH_MD5
-- | SSL2_DES_64_CBC_WITH_MD5
-- | SSL2_RC2_CBC_128_CBC_WITH_MD5
-- |_ SSL2_RC4_128_EXPORT40_WITH_MD5
--@xmloutput
--<elem>SSLv2 supported</elem>
--<table key="ciphers">
-- <elem>SSL2_DES_192_EDE3_CBC_WITH_MD5</elem>
-- <elem>SSL2_IDEA_128_CBC_WITH_MD5</elem>
-- <elem>SSL2_RC2_CBC_128_CBC_WITH_MD5</elem>
-- <elem>SSL2_RC4_128_WITH_MD5</elem>
-- <elem>SSL2_DES_64_CBC_WITH_MD5</elem>
-- <elem>SSL2_RC2_CBC_128_CBC_WITH_MD5</elem>
-- <elem>SSL2_RC4_128_EXPORT40_WITH_MD5</elem>
--</table>
author = "Matthew Boyle"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"default", "safe"}
portrule = shortport.ssl
local hex2dec = function(hex)
local byte1, byte2;
byte1 = string.byte(hex, 1);
byte2 = string.byte(hex, 2);
if (byte1 == nil or byte2 == nil) then return 0; end;
return (byte1 * 256) + byte2;
end
local ciphers = function(cipher_list, len)
-- returns names of ciphers supported by the server
local seen = {}
local available_ciphers = {}
local idx = 0;
local ssl_ciphers = {
-- (cut down) table of codes with their corresponding ciphers.
-- inspired by Wireshark's 'epan/dissectors/packet-ssl-utils.h'
[0x010080] = "SSL2_RC4_128_WITH_MD5",
[0x020080] = "SSL2_RC4_128_EXPORT40_WITH_MD5",
[0x030080] = "SSL2_RC2_CBC_128_CBC_WITH_MD5",
[0x040080] = "SSL2_RC2_CBC_128_CBC_WITH_MD5",
[0x050080] = "SSL2_IDEA_128_CBC_WITH_MD5",
[0x060040] = "SSL2_DES_64_CBC_WITH_MD5",
[0x0700c0] = "SSL2_DES_192_EDE3_CBC_WITH_MD5",
[0x080080] = "SSL2_RC4_64_WITH_MD5",
};
if (len == 0) then return "none"; end
-- something's got broken along the way if these aren't equal
if (len ~= #cipher_list) then
return nil
end
for idx = 1, len, 3 do
local _, cipher = bin.unpack(">I", "\x00" .. string.sub(cipher_list, idx, idx + 2))
local cipher_name = ssl_ciphers[cipher];
if (cipher_name == nil) then
cipher_name = string.format("0x%06x", cipher)
end
-- Check for duplicate ciphers
if not seen[cipher] then
table.insert(available_ciphers, cipher_name)
seen[cipher] = true
end
end
return available_ciphers
end
local give_n_bytes = function(idx, n, str)
-- returns the next n bytes of a string
if (idx + (n - 1) > #str) then
return (idx + n), string.rep(string.char(0x00), n);
end
return (idx + n), string.sub(str, idx, (idx + (n - 1)) );
end
action = function(host, port)
local socket = nmap.new_socket();
local status = true;
local tmp;
local idx = 3; -- start reading after the end of the length record
local return_string = "";
local available_ciphers;
local ssl_v2_hello;
local server_hello;
local server_hello_len;
local message_type;
local SID_hit;
local certificate_type;
local ssl_version;
local certificate_len;
local ciphers_len;
local certificate;
local connection_ID_len;
local cipher_list;
local connection_ID;
-- build client hello packet (contents inspired by
-- http://mail.nessus.org/pipermail/plugins-writers/2004-October/msg00041.html )
local t = {};
table.insert(t, string.char(0x80, 0x31));
table.insert(t, string.char(0x01));
table.insert(t, string.char(0x00, 0x02));
table.insert(t, string.char(0x00, 0x18));
table.insert(t, string.char(0x00, 0x00));
table.insert(t, string.char(0x00, 0x10));
table.insert(t, string.char(0x07, 0x00, 0xc0));
table.insert(t, string.char(0x05, 0x00, 0x80));
table.insert(t, string.char(0x03, 0x00, 0x80));
table.insert(t, string.char(0x01, 0x00, 0x80));
table.insert(t, string.char(0x08, 0x00, 0x80));
table.insert(t, string.char(0x06, 0x00, 0x40));
table.insert(t, string.char(0x04, 0x00, 0x80));
table.insert(t, string.char(0x02, 0x00, 0x80));
table.insert(t, string.char(0xe4, 0xbd, 0x00, 0x00));
table.insert(t, string.char(0xa4, 0x41, 0xb6, 0x74));
table.insert(t, string.char(0x71, 0x2b, 0x27, 0x95));
table.insert(t, string.char(0x44, 0xc0, 0x3d, 0xc0));
ssl_v2_hello = table.concat(t, "")
socket:connect(host, port, "tcp");
socket:send(ssl_v2_hello);
status, server_hello = socket:receive_bytes(2);
if (not status) then
socket:close();
return;
end
server_hello_len = string.sub(server_hello, 1, 2);
server_hello_len = hex2dec(server_hello_len);
-- length record doesn't include its own length, and is "broken".
server_hello_len = server_hello_len - (128 * 256) + 2;
-- the hello needs to be at least 13 bytes long to be of any use
if (server_hello_len < 13) then
socket:close();
return;
end
--try to get entire hello, if we don't already
if (#server_hello < server_hello_len) then
status, tmp = socket:receive_bytes(server_hello_len - #server_hello);
if (not status) then
socket:close();
return;
end
server_hello = server_hello .. tmp;
end;
socket:close();
-- split up server hello into components
idx, message_type = give_n_bytes(idx, 1, server_hello);
idx, SID_hit = give_n_bytes(idx, 1, server_hello);
idx, certificate_type = give_n_bytes(idx, 1, server_hello);
idx, ssl_version = give_n_bytes(idx, 2, server_hello);
idx, certificate_len = give_n_bytes(idx, 2, server_hello);
certificate_len = hex2dec(certificate_len);
idx, ciphers_len = give_n_bytes(idx, 2, server_hello);
ciphers_len = hex2dec(ciphers_len);
idx, connection_ID_len = give_n_bytes(idx, 2, server_hello);
connection_ID_len = hex2dec(connection_ID_len);
idx, certificate = give_n_bytes(idx, certificate_len, server_hello);
idx, cipher_list = give_n_bytes(idx, ciphers_len, server_hello);
idx, connection_ID = give_n_bytes(idx, connection_ID_len, server_hello);
-- some sanity checks:
-- is response a server hello?
if (message_type ~= string.char(0x04)) then
return;
end
-- is certificate in X.509 format?
if (certificate_type ~= string.char(0x01)) then
return;
end
-- get a list of ciphers offered
available_ciphers = ciphers(cipher_list, ciphers_len);
-- actually run some tests:
o = stdnse.output_table()
if (ssl_version == string.char(0x00, 0x02)) then
table.insert(o, "SSLv2 supported")
o["ciphers"] = available_ciphers
end
return o;
end