---
-- A library providing functions for collecting SSL certificates and storing
-- them in the host-based registry.
--
-- The library is largely based on code (copy-pasted) from David Fifields
-- ssl-cert script in an effort to allow certs to be cached and shared among
-- other scripts.
--
-- STARTTLS functions are included for several protocols:
--
-- * FTP
-- * IMAP
-- * LDAP
-- * NNTP
-- * POP3
-- * PostgreSQL
-- * SMTP
-- * TDS (MS SQL Server)
-- * VNC (TLS and VeNCrypt auth types)
-- * XMPP
--
-- @author "Patrik Karlsson <patrik@cqure.net>"

local asn1 = require "asn1"
local bin = require "bin"
local bit = require "bit"
local comm = require "comm"
local ftp = require "ftp"
local ldap = require "ldap"
local match = require "match"
local mssql = require "mssql"
local nmap = require "nmap"
local smtp = require "smtp"
local stdnse = require "stdnse"
local string = require "string"
local table = require "table"
local tls = require "tls"
local vnc = require "vnc"
local xmpp = require "xmpp"
_ENV = stdnse.module("sslcert", stdnse.seeall)

--- Parse an X.509 certificate from DER-encoded string
--@name parse_ssl_certificate
--@class function
--@param der DER-encoded certificate
--@return table containing decoded certificate
--@see nmap.get_ssl_certificate
_ENV.parse_ssl_certificate = nmap.socket.parse_ssl_certificate

-- Simple reconnect_ssl wrapper for most common case
local function tls_reconnect (func)
  return function (host, port)
    local err
    local status, s = StartTLS[func](host, port)
    if status then
      status,err = s:reconnect_ssl()
      if not status then
        stdnse.debug1("Could not establish SSL session after STARTTLS command.")
        s:close()
        return false, "Failed to connect to server"
      else
        return true, s
      end
    end
    return false, string.format("Failed to connect to server: %s", s or "unknown error")
  end
end

-- Class for sockets which wrap sends and receives in some sort of tunnel
-- Overload the wrap_close, wrap_send, and wrap_receive functions to use it.
-- The socket won't be able to reconnect_ssl, though, since Nsock has
-- no idea about the wrapper. Still useful for ssl-* scripts.
WrappedSocket =
{
  new = function(self, socket, o)
    assert(socket, "socket must be connected socket!")
    o = o or {}
    o.socket = socket
    setmetatable(o, self)
    self.__index = function(instance, key)
      return rawget(self, key) or instance.socket[key]
    end
    return o
  end,

  close = function(self)
    return self:wrap_close()
  end,

  receive = function(self)
    return self:wrap_receive()
  end,

  send = function(self, data)
    return self:wrap_send(data)
  end,

  set_timeout = function(self, timeout)
    return self.socket:set_timeout(timeout)
  end,

  receive_buf = function(self, delimiter, keeppattern)
    self.buffer = self.buffer or ""
    local delim_func
    if type(delimiter) == "function" then
      delim_func = delimiter
    else
      delim_func = function(buf)
        return string.find(buf, delimiter)
      end
    end
    local start, finish = delim_func(self.buffer)
    if start then
      local rval
      if keeppattern then
        rval = string.sub(self.buffer, 1, finish)
      else
        rval = string.sub(self.buffer, 1, start - 1)
      end
      self.buffer = string.sub(self.buffer, finish + 1)
      return true, rval
    else
      local status, data = self:receive()
      if not status then
        return status, data
      end
      self.buffer = self.buffer .. data
      -- tail recursion
      return self:receive_buf(delimiter, keeppattern)
    end
  end,

  receive_bytes = function(self, n)
    local x = 0
    local read = {}
    while x < n do
      local status, data = self:receive()
      if not status then
        return status, data
      end
      read[#read+1] = data
      x = x + #data
    end
    return true, table.concat(read)
  end,

  receive_lines = function(self, n)
    local x = 0
    local read = {}
    local function incr()
      x = x + 1
    end
    while x < n do
      local status, data = self:receive()
      if not status then
        return status, data
      end
      read[#read+1] = data
      string.gsub(data, "\n", incr)
    end
    return true, table.concat(read)
  end,

  }


StartTLS = {

  ftp_prepare_tls_without_reconnect = function(host, port)
    -- Attempt to negotiate TLS over FTP for services that support it
    -- Works for FTP (21)

    -- Open a standard TCP socket
    local s, err = comm.opencon(host, port)
    if not s then
      return false, string.format("Failed to connect to FTP server: %s", err)
    end
    local buf = stdnse.make_buffer(s, "\r?\n")

    local code, result = ftp.read_reply(buf)
    if code ~= 220 then
      return false, string.format("FTP protocol error: %s", code or result)
    end

    -- Send AUTH TLS command, ask the service to start encryption
    s:send("AUTH TLS\r\n")
    code, result = ftp.read_reply(buf)
    if code ~= 234 then
      stdnse.debug1("AUTH TLS failed or unavailable.  Enable --script-trace to see what is happening.")

      -- Send QUIT to clean up server side connection
      s:send("QUIT\r\n")

      return false, string.format("FTP AUTH TLS error: %s", code or result)
    end
    -- Should have a solid TLS over FTP session now...
    return true, s
  end,

  ftp_prepare_tls = tls_reconnect("ftp_prepare_tls_without_reconnect"),

  imap_prepare_tls_without_reconnect = function(host, port)
    -- Attempt to negotiate TLS over IMAP for services that support it
    -- Works for IMAP (143)

    -- Open a standard TCP socket
    local s, err, result = comm.opencon(host, port, "", {lines=1, recv_before=true})
    if not s then
      return false, string.format("Failed to connect to IMAP server: %s", err)
    end

    if not string.match(result, "^%* OK") then
      return false, "IMAP protocol mismatch"
    end

    -- Check for STARTTLS support.
    local status = s:send("A001 CAPABILITY\r\n")
    status, result = s:receive_lines(1)

    if not (string.match(result, "STARTTLS")) then
      stdnse.debug1("Server doesn't support STARTTLS")
      return false, "Failed to connect to IMAP server"
    end

    -- Send the STARTTLS message
    status = s:send("A002 STARTTLS\r\n")
    status, result = s:receive_lines(1)

    if not (string.match(result, "^A002 OK")) then
      stdnse.debug1(string.format("Error: %s", result))
      return false, "Failed to connect to IMAP server"
    end

    -- Should have a solid TLS over IMAP session now...
    return true, s
  end,

  imap_prepare_tls = tls_reconnect("imap_prepare_tls_without_reconnect"),

  ldap_prepare_tls_without_reconnect = function(host, port)
    local s = nmap.new_socket()
    -- Attempt to negotiate TLS over LDAP for services that support it
    -- Works for LDAP (389)

    -- Open a standard TCP socket
    local status, error = s:connect(host, port, "tcp")
    if not status then
      return false, "Failed to connect to LDAP server"
    end

    -- Create an ExtendedRequest and specify the OID for the
    -- Start TTLS operation (see http://www.ietf.org/rfc/rfc2830.txt)
    local ExtendedRequest = 23
    local ExtendedResponse = 24
    local oid, ldapRequest, ldapRequestId
    oid = ldap.encode("1.3.6.1.4.1.1466.20037")
    ldapRequest = ldap.encodeLDAPOp(ExtendedRequest, true, oid)
    ldapRequestId = ldap.encode(1)

    -- Send the STARTTLS request
    local encoder = asn1.ASN1Encoder:new()
    local data = encoder:encodeSeq(ldapRequestId .. ldapRequest)
    status = s:send(data)
    if not status then
      return false, "STARTTLS failed"
    end

    -- Decode the response
    local response
    status, response = s:receive()
    if not status then
      return false, "STARTTLS failed"
    end

    local decoder = asn1.ASN1Decoder:new()
    local len, pos, messageId, ldapOp, tmp = ""
    pos, len = decoder.decodeLength(response, 2)
    pos, messageId = ldap.decode(response, pos)
    pos, tmp = bin.unpack("C", response, pos)
    ldapOp = asn1.intToBER(tmp)

    if ldapOp.number ~= ExtendedResponse then
      stdnse.debug1(string.format(
        "STARTTLS failed (got wrong op number: %d)", ldapOp.number))
      return false, "STARTTLS failed"
    end

    local resultCode
    pos, len = decoder.decodeLength(response, pos)
    pos, resultCode = ldap.decode(response, pos)

    if resultCode ~= 0 then
      stdnse.debug1(string.format(
        "STARTTLS failed (LDAP error code is: %d)", resultCode))
      return false, "STARTTLS failed"
    end

    -- Should have a solid TLS over LDAP session now...
    return true,s
  end,

  ldap_prepare_tls = tls_reconnect("ldap_prepare_tls_without_reconnect"),

  lmtp_prepare_tls_without_reconnect = function(host, port)
    -- Open a standard TCP socket
    local s, result = smtp.connect(host, port, {lines=1, recv_before=1, ssl=false})
    if not s then
      return false, string.format("Failed to connect to LMTP server: %s", result)
    end

    local status
    status, result = smtp.query(s, "LHLO", "example.com")
    if not status then
      stdnse.debug1("LHLO with errors or timeout.  Enable --script-trace to see what is happening.")
      return false, string.format("Failed to LHLO: %s", result)
    end
    -- semantics of LHLO are same as EHLO
    status, result = smtp.check_reply("EHLO", result)
    if not status then
      return false, string.format("Received LHLO error: %s", result)
    end

    -- Send STARTTLS command ask the service to start encryption
    status, result = smtp.query(s, "STARTTLS")
    if status then
      status, result = smtp.check_reply("STARTTLS", result)
    end

    if not status then
      stdnse.debug1("STARTTLS failed or unavailable.  Enable --script-trace to see what is happening.")

      -- Send QUIT to clean up server side connection
      smtp.quit(s)
      return false, string.format("Failed to connect to SMTP server: %s", result)
    end
    -- Should have a solid TLS over LMTP session now...
    return true, s
  end,

  lmtp_prepare_tls = tls_reconnect("lmtp_prepare_tls_without_reconnect"),

  nntp_prepare_tls_without_reconnect = function(host, port)
    local s, err, result = comm.opencon(host, port, "", {lines=1, recv_before=true})
    if not s then
      return false, string.format("Failed to connect to NNTP server: %s", err)
    end

    if not string.match(result, "^200") then
      return false, "NNTP protocol mismatch"
    end

    local status = s:send("STARTTLS\r\n")
    status, result = s:receive_lines(1)

    if not (string.match(result, "^382 ")) then
      stdnse.debug1(string.format("Error: %s", result))
      status = s:send("QUIT\r\n")
      s:close()
      return false, "NNTP server does not support STARTTLS"
    end

    return true, s
  end,

  nntp_prepare_tls = tls_reconnect("nntp_prepare_tls_without_reconnect"),

  pop3_prepare_tls_without_reconnect = function(host, port)
    -- Attempt to negotiate TLS over POP3 for services that support it
    -- Works for POP3 (110)

    -- Open a standard TCP socket
    local s, err, result = comm.opencon(host, port, "", {lines=1, recv_before=true})
    if not s then
      return false, string.format("Failed to connect to POP3 server: %s", err)
    end

    if not string.match(result, "^%+OK") then
      return false, "POP3 protocol mismatch"
    end

    -- Send the STLS message
    local status = s:send("STLS\r\n")
    status, result = s:receive_lines(1)

    if not (string.match(result, "^%+OK")) then
      stdnse.debug1(string.format("Error: %s", result))
      status = s:send("QUIT\r\n")
      return false, "Failed to connect to POP3 server"
    end

    -- Should have a solid TLS over POP3 session now...
    return true, s
  end,

  pop3_prepare_tls = tls_reconnect("pop3_prepare_tls_without_reconnect"),

  postgres_prepare_tls_without_reconnect = function(host, port)
    -- http://www.postgresql.org/docs/devel/static/protocol-message-formats.html
    -- 80877103 is "SSLRequest" in v2 and v3 of Postgres protocol
    local s, resp = comm.opencon(host, port, bin.pack(">II", 8, 80877103))
    if not s then
      return false, ("Failed to connect to Postgres server: %s"):format(resp)
    end
    -- v2 has "Y", v3 has "S"
    if string.match(resp, "^[SY]") then
      return true, s
    elseif string.match(resp, "^N") then
      return false, "Postgres server does not support SSL"
    end
    return false, "Unknown response from Postgres server"
  end,

  postgres_prepare_tls = tls_reconnect("postgres_prepare_tls_without_reconnect"),

  smtp_prepare_tls_without_reconnect = function(host, port)
    -- Attempt to negotiate TLS over SMTP for services that support it
    -- Works for SMTP (25) and SMTP Submission (587)

    -- Open a standard TCP socket
    local s, result = smtp.connect(host, port, {lines=1, recv_before=1, ssl=false})
    if not s then
      return false, string.format("Failed to connect to SMTP server: %s", result)
    end

    local status
    status, result = smtp.ehlo(s, "example.com")
    if not status then
      stdnse.debug1("EHLO with errors or timeout.  Enable --script-trace to see what is happening.")
      return false, string.format("Failed to connect to SMTP server: %s", result)
    end

    -- Send STARTTLS command ask the service to start encryption
    status, result = smtp.query(s, "STARTTLS")
    if status then
      status, result = smtp.check_reply("STARTTLS", result)
    end

    if not status then
      stdnse.debug1("STARTTLS failed or unavailable.  Enable --script-trace to see what is happening.")

      -- Send QUIT to clean up server side connection
      smtp.quit(s)
      return false, string.format("Failed to connect to SMTP server: %s", result)
    end
    -- Should have a solid TLS over SMTP session now...
    return true, s
  end,

  smtp_prepare_tls = tls_reconnect("smtp_prepare_tls_without_reconnect"),

  tds_prepare_tls_without_reconnect = function(host, port)
    local tds = mssql.TDSStream:new()
    local status, result = tds:Connect(host, port)
    if not status then return status, result end
    local prelogin = mssql.PreLoginPacket:new()
    prelogin:SetRequestEncryption(true)
    tds:Send( prelogin:ToBytes() )
    status, result = tds:Receive()
    if not status then return status, result end

    local status, preloginResponse = mssql.PreLoginPacket.FromBytes(result)
    if not status then return status, preloginResponse end

    local encryption
    local pos, optype, oppos, oplen = bin.unpack('>CSS', result)
    while optype ~= mssql.PreLoginPacket.OPTION_TYPE.Terminator do
      --stdnse.debug1("optype: %d, oppos: %x, oplen: %d", optype, oppos, oplen)
      if optype == mssql.PreLoginPacket.OPTION_TYPE.Encryption then
        encryption = bin.unpack('C', result, oppos + 1)
        break
      end
      pos, optype, oppos, oplen = bin.unpack('>CSS', result, pos)
    end
    if not encryption then
      return false, "no encryption option found"
    elseif encryption == 0 then
      return false, "Server refused encryption"
    elseif encryption == 3 then
      return false, "Server does not support encryption"
    end

    return true, WrappedSocket:new(tds._socket, {
        wrap_close = function(self)
          return tds:Disconnect()
        end,
        wrap_receive = function(self)
          -- mostly lifted from mssql.TDSStream.Receive
          -- TODO: Modify that function to allow recieving arbitrary response
          -- types, since it's only because it forces type 0x04 that we had to
          -- do this here (where we expect type 0x12)
          local combinedData = ""
          local readBuffer = ""
          local pos = 1
          local tdsPacketAvailable = true

          -- Large messages (e.g. result sets) can be split across multiple TDS
          -- packets from the server (which could themselves each be split across
          -- multiple TCP packets or SMB messages).
          while ( tdsPacketAvailable ) do
            -- If there is existing data in the readBuffer, see if there's
            -- enough to read the TDS headers for the next packet. If not,
            -- do another read so we have something to work with.
            if #readBuffer < 8 then
              status, result = tds._socket:receive_bytes(8 - readBuffer:len())
              if not status then return status, result end
              readBuffer = readBuffer .. result
            end

            -- TDS packet validity check: packet at least as long as the TDS header
            if #readBuffer < 8 then
              return false, "Server returned short packet"
            end

            -- read in the TDS headers
            local packetType, messageStatus, packetLength
            pos, packetType, messageStatus, packetLength = bin.unpack(">CCS", readBuffer, pos )
            local spid, packetId, window
            pos, spid, packetId, window = bin.unpack(">SCC", readBuffer, pos )

            if packetLength > #readBuffer then
              status, result = tds._socket:receive_bytes(packetLength - #readBuffer)
              if not status then return status, result end
              readBuffer = readBuffer .. result
            end

            -- We've read in an apparently valid TDS packet
            local thisPacketData = readBuffer:sub( pos, packetLength )
            -- Append its data to that of any previous TDS packets
            combinedData = combinedData .. thisPacketData
            -- If we read in data beyond the end of this TDS packet, save it
            -- so that we can use it in the next loop.
            readBuffer = readBuffer:sub( packetLength + 1 )

            -- Check the status flags in the TDS packet to see if the message is
            -- continued in another TDS packet.
            tdsPacketAvailable = (
              bit.band( messageStatus, mssql.TDSStream.MESSAGE_STATUS_FLAGS.EndOfMessage)
              ~= mssql.TDSStream.MESSAGE_STATUS_FLAGS.EndOfMessage)
          end

          -- return only the data section ie. without the headers
          return true, combinedData

        end,
        wrap_send = function(self, data)
          return tds:Send(mssql.PacketType.PreLogin, data)
        end,
      })
  end,
  -- no TLS reconnect for TDS because of the wrapped handshake thing.
  tds_prepare_tls = function(host, port)
    return false, "Full SSL connection over TDS not supported"
  end,

  vnc_prepare_tls_without_reconnect = function(host,port)
    local v = vnc.VNC:new( host, port )

    local status, data = v:connect()
    if not status then
      return false, string.format("Failed to connect to VNC server: %s", data)
    end

    status, data = v:handshake()
    if not status then
      return false, string.format("Failed VNC handshake: %s", data)
    end

    local sock = v.socket
    if v:supportsSecType(vnc.VNC.sectypes.VENCRYPT) then

      status = sock:send( bin.pack("C", vnc.VNC.sectypes.VENCRYPT) )
      if not status then
        return false, "Failed to select VeNCrypt authentication type"
      end

      local status, buf = sock:receive_buf(match.numbytes(2), true)
      local pos, maj, min = bin.unpack("CC", buf)
      if maj ~= 0 or min ~= 2 then
        return false, string.format("Unknown VeNCrypt version: %d.%d", maj, min)
      end
      sock:send(bin.pack("CC", maj, min))
      status, buf = sock:receive_buf(match.numbytes(1), true)
      pos, status = bin.unpack("C", buf)
      if status ~= 0 then
        return false, string.format("Server refused VeNCrypt version %d.%d", maj, min)
      end

      status, buf = sock:receive_buf(match.numbytes(1), true)
      local pos, nauth = bin.unpack("C", buf)
      if nauth == 0 then
        return false, "No VeNCrypt auth subtypes received"
      end

      -- vencrypt auth types are u32
      status, buf = sock:receive_buf(match.numbytes(nauth * 4), true)
      local best
      pos = 1
      for i=1, nauth do
        local auth
        pos, auth = bin.unpack(">I", buf, pos)
        if auth >= 260 and auth <= 263 then
          -- X509 auth subtype
          best = auth
          break
        elseif auth >= 257 then
          -- other TLS auth subtype (Plain is 256)
          -- These are anon types, so no cert available
          best = auth
        end
      end
      if not best then
        return false, "No TLS VeNCrypt auth subtype received"
      end
      sock:send(bin.pack(">I", best))
      status, buf = sock:receive_buf(match.numbytes(1), true)
      if not status or string.byte(buf, 1) ~= 1 then
        return false, "VeNCrypt auth subtype refused"
      end
      return true, sock
    elseif v:supportsSecType(vnc.VNC.sectypes.TLS) then
      status = sock:send( bin.pack("C", vnc.VNC.sectypes.TLS) )
      if not status then
        return false, "Failed to select TLS authentication type"
      end
    else
      return false, string.format("No TLS auth types supported")
    end
    return true, sock
  end,

  vnc_prepare_tls = tls_reconnect("vnc_prepare_tls_without_reconnect"),

  xmpp_prepare_tls_without_reconnect = function(host,port)
    local sock,status,err,result
    local xmppStreamStart = string.format("<?xml version='1.0' ?>\r\n<stream:stream xmlns:stream='http://etherx.jabber.org/streams' xmlns='jabber:client' to='%s' version='1.0'>\r\n",host.name)
    local xmppStartTLS = "<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>\r\n"
    sock = nmap.new_socket()
    sock:set_timeout(5000)
    status, err = sock:connect(host, port)
    if not status then
      sock:close()
      stdnse.debug1("Can't send: %s", err)
      return false, "Failed to connect to XMPP server"
    end
    status, err = sock:send(xmppStreamStart)
    if not status then
      stdnse.debug1("Couldn't send: %s", err)
      sock:close()
      return false, "Failed to connect to XMPP server"
    end
    status, result = sock:receive()
    if not status then
      stdnse.debug1("Couldn't receive: %s", err)
      sock:close()
      return false, "Failed to connect to XMPP server"
    end
    status, err = sock:send(xmppStartTLS)
    if not status then
      stdnse.debug1("Couldn't send: %s", err)
      sock:close()
      return false, "Failed to connect to XMPP server"
    end
    status, result = sock:receive()
    if not status then
      stdnse.debug1("Couldn't receive: %s", err)
      sock:close()
      return false, "Failed to connect to XMPP server"
    end
    if string.find(result,"proceed") then
      return true,sock
    end

    status, result = sock:receive() -- might not be in the first reply
    if not status then
      stdnse.debug1("Couldn't receive: %s", err)
      sock:close()
      return false, "Failed to connect to XMPP server"
    end
    if string.find(result,"proceed") then
      return true,sock
    else
      return false, "Failed to connect to XMPP server"
    end
  end,

  xmpp_prepare_tls = function(host, port)
    local ls = xmpp.XMPP:new(host, port, { starttls = true } )
    ls.socket = nmap.new_socket()
    ls.socket:set_timeout(ls.options.timeout * 1000)

    local status, err = ls.socket:connect(host, port)
    if not status then
      return nil
    end

    status, err = ls:connect()
    if not(status) then
      return false, "Failed to connected"
    end
    return true, ls.socket
  end
}


-- A table mapping port numbers to specialized SSL negotiation functions.
local SPECIALIZED_PREPARE_TLS = {
  ftp = StartTLS.ftp_prepare_tls,
  [21] = StartTLS.ftp_prepare_tls,
  nntp = StartTLS.nntp_prepare_tls,
  [119] = StartTLS.nntp_prepare_tls,
  imap = StartTLS.imap_prepare_tls,
  [143] = StartTLS.imap_prepare_tls,
  ldap = StartTLS.ldap_prepare_tls,
  [389] = StartTLS.ldap_prepare_tls,
  lmtp = StartTLS.lmtp_prepare_tls,
  pop3 = StartTLS.pop3_prepare_tls,
  [110] = StartTLS.pop3_prepare_tls,
  postgresql = StartTLS.postgres_prepare_tls,
  [5432] = StartTLS.postgres_prepare_tls,
  smtp = StartTLS.smtp_prepare_tls,
  [25] = StartTLS.smtp_prepare_tls,
  [587] = StartTLS.smtp_prepare_tls,
  xmpp = StartTLS.xmpp_prepare_tls,
  [5222] = StartTLS.xmpp_prepare_tls,
  [5269] = StartTLS.xmpp_prepare_tls,
  vnc = StartTLS.vnc_prepare_tls,
  [5900] = StartTLS.vnc_prepare_tls,
  ["ms-sql-s"] = StartTLS.tds_prepare_tls
}

local SPECIALIZED_PREPARE_TLS_WITHOUT_RECONNECT = {
  ftp = StartTLS.ftp_prepare_tls_without_reconnect,
  [21] = StartTLS.ftp_prepare_tls_without_reconnect,
  nntp = StartTLS.nntp_prepare_tls_without_reconnect,
  [119] = StartTLS.nntp_prepare_tls_without_reconnect,
  imap = StartTLS.imap_prepare_tls_without_reconnect,
  [143] = StartTLS.imap_prepare_tls_without_reconnect,
  ldap = StartTLS.ldap_prepare_tls_without_reconnect,
  [389] = StartTLS.ldap_prepare_tls_without_reconnect,
  lmtp = StartTLS.lmtp_prepare_tls_without_reconnect,
  pop3 = StartTLS.pop3_prepare_tls_without_reconnect,
  [110] = StartTLS.pop3_prepare_tls_without_reconnect,
  postgresql = StartTLS.postgres_prepare_tls_without_reconnect,
  [5432] = StartTLS.postgres_prepare_tls_without_reconnect,
  smtp = StartTLS.smtp_prepare_tls_without_reconnect,
  [25] = StartTLS.smtp_prepare_tls_without_reconnect,
  [587] = StartTLS.smtp_prepare_tls_without_reconnect,
  xmpp = StartTLS.xmpp_prepare_tls_without_reconnect,
  [5222] = StartTLS.xmpp_prepare_tls_without_reconnect,
  [5269] = StartTLS.xmpp_prepare_tls_without_reconnect,
  vnc = StartTLS.vnc_prepare_tls_without_reconnect,
  [5900] = StartTLS.vnc_prepare_tls_without_reconnect,
}

-- these can't do reconnect_ssl
local SPECIALIZED_WRAPPED_TLS_WITHOUT_RECONNECT = {
  ["ms-sql-s"] = StartTLS.tds_prepare_tls_without_reconnect,
}

--- Get a specialized SSL connection function without starting SSL
--
-- For protocols that require some sort of START-TLS setup, this function will
-- return a function that can be used to produce a socket that is ready for SSL
-- messages.
-- @param port A port table with 'number' and 'service' keys
-- @return A STARTTLS function or nil
function getPrepareTLSWithoutReconnect(port)
  if port.protocol == 'udp' then
    return nil
  end
  if ( port.version and port.version.service_tunnel == 'ssl') then
    return nil
  end
  return (SPECIALIZED_PREPARE_TLS_WITHOUT_RECONNECT[port.service] or
    SPECIALIZED_PREPARE_TLS_WITHOUT_RECONNECT[port.number] or
    SPECIALIZED_WRAPPED_TLS_WITHOUT_RECONNECT[port.service] or
    SPECIALIZED_WRAPPED_TLS_WITHOUT_RECONNECT[port.number])
end

--- Get a specialized SSL connection function to create an SSL socket
--
-- For protocols that require some sort of START-TLS setup, this function will
-- return a function that can be used to produce an SSL-connected socket.
-- @param port A port table with 'number' and 'service' keys
-- @return A STARTTLS function or nil
function isPortSupported(port)
  if port.protocol == 'udp' then
    return nil
  end
  if ( port.version and port.version.service_tunnel == 'ssl') then
    return nil
  end
  return (SPECIALIZED_PREPARE_TLS[port.service] or
    SPECIALIZED_PREPARE_TLS[port.number])
end

-- returns a function that yields a new tls record each time it is called
local function get_record_iter(sock)
  local buffer = ""
  local i = 1
  local fragment
  return function ()
    local record
    i, record = tls.record_read(buffer, i, fragment)
    if record == nil then
      local status, err
      status, buffer, err = tls.record_buffer(sock, buffer, i)
      if not status then
        return nil, err
      end
      i, record = tls.record_read(buffer, i, fragment)
      if record == nil then
        return nil, "done"
      end
    end
    fragment = record.fragment
    return record
  end
end

--- Gets a certificate for the given host and port
-- The function will attempt to START-TLS for the ports known to require it.
-- @param host table as received by the script action function
-- @param port table as received by the script action function
-- @return status true on success, false on failure
-- @return cert userdata containing the SSL certificate, or error message on
--         failure.
function getCertificate(host, port)
  local mutex = nmap.mutex("sslcert-cache-mutex")
  mutex "lock"

  if ( host.registry["ssl-cert"] and
    host.registry["ssl-cert"][port.number] ) then
    stdnse.debug2("sslcert: Returning cached SSL certificate")
    mutex "done"
    return true, host.registry["ssl-cert"][port.number]
  end

  local cert
  -- do we have to use a wrapper and do a manual handshake?
  local wrapper = SPECIALIZED_WRAPPED_TLS_WITHOUT_RECONNECT[port.service] or SPECIALIZED_WRAPPED_TLS_WITHOUT_RECONNECT[port.number]
  if wrapper then
    local status, socket = wrapper(host, port)
    if not status then
      mutex "done"
      return false, socket
    end

    -- logic mostly lifted from ssl-enum-ciphers
    local hello = tls.client_hello()
    local status, err = socket:send(hello)
    if not status then
      mutex "done"
      return false, "Failed to connect to server"
    end

    local get_next_record = get_record_iter(socket)
    local records = {}
    while true do
      local record
      record, err = get_next_record()
      if not record then
        stdnse.debug1("no record: %s", err)
        socket:close()
        break
      end
      -- Collect message bodies into one record per type
      records[record.type] = records[record.type] or record
      local done = false
      for j = 1, #record.body do -- no ipairs because we append below
        local b = record.body[j]
        done = ((record.type == "alert" and b.level == "fatal") or
          (record.type == "handshake" and b.type == "server_hello_done"))
        table.insert(records[record.type].body, b)
      end
      if done then
        socket:close()
        break
      end
    end

    local handshake = records.handshake
    if not handshake then
      mutex "done"
      return false, "Server did not handshake"
    end

    local certs
    for i, b in ipairs(handshake.body) do
      if b.type == "certificate" then
        certs = b
        break
      end
    end
    if not certs or not next(certs.certificates) then
      mutex "done"
      return false, "Server sent no certificate"
    end

    cert = parse_ssl_certificate(certs.certificates[1])
    if not cert then
      mutex "done"
      return false, "Unable to get cert"
    end
  else
    -- Is there a specialized function for this port?
    local specialized = SPECIALIZED_PREPARE_TLS[port.service] or SPECIALIZED_PREPARE_TLS[port.number]
    local status
    local socket = nmap.new_socket()
    if specialized then
      status, socket = specialized(host, port)
      if not status then
        mutex "done"
        stdnse.debug1("Specialized function error: %s", socket)
        return false, "Failed to connect to server"
      end
    else
      status = socket:connect(host, port, "ssl")
      if ( not(status) ) then
        mutex "done"
        return false, "Failed to connect to server"
      end
    end
    cert = socket:get_ssl_certificate()
    if ( cert == nil ) then
      mutex "done"
      return false, "Unable to get cert"
    end
  end

  host.registry["ssl-cert"] = host.registry["ssl-cert"] or {}
  host.registry["ssl-cert"][port.number] = host.registry["ssl-cert"][port.number] or {}
  host.registry["ssl-cert"][port.number] = cert
  mutex "done"
  return true, cert
end



return _ENV;
