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|
local nmap = require "nmap"
local shortport = require "shortport"
local stdnse = require "stdnse"
local string = require "string"
local table = require "table"
local sslcert = require "sslcert"
local tls = require "tls"
description = [[
Enumerates a TLS server's supported application-layer protocols using the ALPN protocol.
Repeated queries are sent to determine which of the registered protocols are supported.
For more information, see:
* https://tools.ietf.org/html/rfc7301
]]
---
-- @usage
-- nmap --script=tls-alpn <targets>
--
--@output
-- 443/tcp open https
-- | tls-alpn:
-- | h2
-- | spdy/3
-- |_ http/1.1
--
-- @xmloutput
-- <elem>h2</elem>
-- <elem>spdy/3</elem>
-- <elem>http/1.1</elem>
author = "Daniel Miller"
license = "Same as Nmap--See https://nmap.org/book/man-legal.html"
categories = {"discovery", "safe", "default"}
dependencies = {"https-redirect"}
portrule = function(host, port)
return shortport.ssl(host, port) or sslcert.getPrepareTLSWithoutReconnect(port)
end
local ALPN_NAME = "application_layer_protocol_negotiation"
--- Function that sends a client hello packet with the TLS ALPN extension to the
-- target host and returns the response
--@args host The target host table.
--@args port The target port table.
--@return status true if response, false else.
--@return response if status is true.
local client_hello = function(host, port, protos)
local sock, status, response, err, cli_h
cli_h = tls.client_hello({
["extensions"] = {
[ALPN_NAME] = tls.EXTENSION_HELPERS[ALPN_NAME](protos)
},
})
-- Connect to the target server
local status, err
local sock
local specialized = sslcert.getPrepareTLSWithoutReconnect(port)
if specialized then
status, sock = specialized(host, port)
if not status then
stdnse.debug1("Connection to server failed: %s", sock)
return false
end
else
sock = nmap.new_socket()
status, err = sock:connect(host, port)
if not status then
stdnse.debug1("Connection to server failed: %s", err)
return false
end
end
sock:set_timeout(5000)
-- Send Client Hello to the target server
status, err = sock:send(cli_h)
if not status then
stdnse.debug1("Couldn't send: %s", err)
sock:close()
return false
end
-- Read response
status, response, err = tls.record_buffer(sock)
if not status then
stdnse.debug1("Couldn't receive: %s", err)
sock:close()
return false
end
return true, response
end
--- Function that checks for the returned protocols to a ALPN extension request.
--@args response Response to parse.
--@return results List of found protocols.
local check_alpn = function(response)
local i, record = tls.record_read(response, 1)
if record == nil then
stdnse.debug1("Unknown response from server")
return nil
end
if record.type == "handshake" and record.body[1].type == "server_hello" then
if record.body[1].extensions == nil then
stdnse.debug1("Server did not return TLS ALPN extension.")
return nil
end
local results = {}
local alpndata = record.body[1].extensions[ALPN_NAME]
if alpndata == nil then
stdnse.debug1("Server did not return TLS ALPN extension.")
return nil
end
-- Parse data
alpndata = string.unpack(">s2", alpndata, 1)
i = 1
while i <= #alpndata do
if i > 1 then
stdnse.debug1("Server sent multiple protocols but RFC only permits 1")
end
local protocol
protocol, i = string.unpack(">s1", alpndata, i)
table.insert(results, protocol)
end
if next(results) then
return results
else
stdnse.debug1("Server supports TLS ALPN extension, but no protocols were offered.")
return nil
end
else
stdnse.debug1("Server response was not server_hello")
return nil
end
end
local function find_and_remove(t, value)
for i, v in ipairs(t) do
if v == value then
table.remove(t, i)
return true
end
end
return false
end
action = function(host, port)
local alpn_protos = {
-- IANA-registered names
"http/1.1",
"spdy/1",
"spdy/2",
"spdy/3",
"stun.turn",
"stun.nat-discovery",
"h2",
"h2c", -- should never be negotiated over TLS
"webrtc",
"c-webrtc",
"ftp",
"imap",
"pop3",
"managesieve",
-- Other sources
"grpc-exp", -- gRPC, see grpc.io
}
local chosen = {}
local unique = {}
while next(alpn_protos) do
-- Send crafted client hello
local status, response = client_hello(host, port, alpn_protos)
if status and response then
-- Analyze response
local result = check_alpn(response)
if not result then
stdnse.debug1("None of %d protocols chosen", #alpn_protos)
goto ALPN_DONE
end
for i, p in ipairs(result) do
if i > 1 then
stdnse.verbose1("Server violates RFC: sent additional protocol %s", p)
else
if not unique[p] then
chosen[#chosen+1] = p
end
unique[p] = true
if not find_and_remove(alpn_protos, p) then
stdnse.debug1("Chosen ALPN protocol %s was not offered", p)
-- Server is forcing this protocol, no need to continue offering.
goto ALPN_DONE
end
end
end
else
stdnse.debug1("Client hello failed with %d protocols", #alpn_protos)
goto ALPN_DONE
end
end
::ALPN_DONE::
if next(chosen) then
return chosen
end
end
|
