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: server still supports SSLv2 -- | SSL2_RC4_128_WITH_MD5 -- | SSL2_DES_192_EDE3_CBC_WITH_MD5 -- | SSL2_RC2_CBC_128_CBC_WITH_MD5 -- | SSL2_DES_64_CBC_WITH_MD5 -- | SSL2_RC4_128_EXPORT40_WITH_MD5 -- |_ SSL2_RC2_CBC_128_CBC_WITH_MD5 author = "Matthew Boyle" license = "Same as Nmap--See http://nmap.org/book/man-legal.html" categories = {"default", "safe"} require "shortport" portrule = shortport.ssl 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 cyphers = function(cypher_list, len) -- returns names of cyphers supported by the server local cypher; local cypher_name; local byte1, byte2, byte3; local available_cyphers = ""; local idx = 0; local ssl_cyphers = { -- (cut down) table of codes with their corresponding cyphers. -- 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 ~= #cypher_list) then return ""; end for idx = 1, len, 3 do cypher = string.sub(cypher_list, idx, idx + 2); byte1 = string.byte(cypher, 1); byte2 = string.byte(cypher, 2); byte3 = string.byte(cypher, 3); cypher = (byte1 * 256 * 256) + (byte2 * 256) + byte3; cypher_name = ssl_cyphers[cypher]; if (cypher_name == nil) then cypher_name = "unknown cypher (" .. byte1 .. "-" .. byte2 .. "-" .. byte3 .. " dec)" end -- Check for duplicate cyphers if not available_cyphers:match("\t" .. cypher_name .. "\n") then available_cyphers = available_cyphers .. "\t" .. cypher_name .. "\n"; end end return available_cyphers end 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_cyphers = ""; 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 cyphers_len; local certificate; local connection_ID_len; local cypher_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, cyphers_len = give_n_bytes(idx, 2, server_hello); cyphers_len = hex2dec(cyphers_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, cypher_list = give_n_bytes(idx, cyphers_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 cyphers offered available_cyphers = cyphers(cypher_list, cyphers_len); -- actually run some tests: if (ssl_version == string.char(0x00, 0x02)) then if (available_cyphers == "none") then return_string = "server supports SSLv2 protocol, but no SSLv2 cyphers\n"; else return_string = "server still supports SSLv2\n"; if (nmap.verbosity() > 1 or nmap.debugging() > 0) then return_string = return_string .. available_cyphers; end end end return return_string; end