/nselib/http.lua

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---Implements the HTTP client protocol in a standard form that Nmap scripts can
-- take advantage of.
--
-- Because HTTP has so many uses, there are a number of interfaces to this library.
-- The most obvious and common ones are simply <code>get</code>, <code>post</code>,
-- and <code>head</code>; or, if more control is required, <code>generic_request</code>
-- can be used. These functions do what one would expect. The <code>get_url</code>
-- helper function can be used to parse and retrieve a full URL.
--
-- HTTPS support is transparent. The library uses <code>comm.tryssl</code> to
-- determine whether SSL is required for a request.
--
-- These functions return a table of values, including:
-- * <code>status-line</code> - A string representing the status, such as "HTTP/1.1 200 OK". In case of an error, a description will be provided in this line.
-- * <code>status</code>: The HTTP status value; for example, "200". If an error occurs during a request, then this value is going to be nil.
-- * <code>header</code> - An associative array representing the header. Keys are all lowercase, and standard headers, such as 'date', 'content-length', etc. will typically be present.
-- * <code>rawheader</code> - A numbered array of the headers, exactly as the server sent them. While header['content-type'] might be 'text/html', rawheader[3] might be 'Content-type: text/html'.
-- * <code>cookies</code> - A numbered array of the cookies the server sent. Each cookie is a table with the following keys: <code>name</code>, <code>value</code>, <code>path</code>, <code>domain</code>, and <code>expires</code>.
-- * <code>body</code> - The full body, as returned by the server.
--
-- If a script is planning on making a lot of requests, the pipelining functions can
-- be helpful. <code>pipeline_add</code> queues requests in a table, and
-- <code>pipeline</code> performs the requests, returning the results as an array,
-- with the responses in the same order as the queries were added. As a simple example:
--<code>
--  -- Start by defining the 'all' variable as nil
--  local all = nil
--
--  -- Add two 'GET' requests and one 'HEAD' to the queue. These requests are not performed
--  -- yet. The second parameter represents the 'options' table, which we don't need.
--  all = http.pipeline_add('/book',    nil, all)
--  all = http.pipeline_add('/test',    nil, all)
--  all = http.pipeline_add('/monkeys', nil, all, 'HEAD')
--
--  -- Perform all three requests as parallel as Nmap is able to
--  local results = http.pipeline('nmap.org', 80, all)
--</code>
--
-- At this point, <code>results</code> is an array with three elements. Each element
-- is a table containing the HTTP result, as discussed above.
--
-- One more interface provided by the HTTP library helps scripts determine whether or not
-- a page exists. The <code>identify_404</code> function will try several URLs on the
-- server to determine what the server's 404 pages look like. It will attempt to identify
-- customized 404 pages that may not return the actual status code 404. If successful,
-- the function <code>page_exists</code> can then be used to determine whether or not
-- a page existed.
--
-- Some other miscellaneous functions that can come in handy are <code>response_contains</code>,
-- <code>can_use_head</code>, and <code>save_path</code>. See the appropriate documentation
-- for them.
--
-- The response to each function is typically a table with the following keys:
-- * <code>status-line</code>: The HTTP status line; for example, "HTTP/1.1 200 OK" (note: this is followed by a newline). In case of an error, a description will be provided in this line.
-- * <code>status</code>: The HTTP status value; for example, "200". If an error occurs during a request, then this value is going to be nil.
-- * <code>header</code>: A table of header values, where the keys are lowercase and the values are exactly what the server sent
-- * <code>rawheader</code>: A list of header values as "name: value" strings, in the exact format and order that the server sent them
-- * <code>cookies</code>: A list of cookies that the server is sending. Each cookie is a table containing the keys <code>name</code>, <code>value</code>, and <code>path</code>. This table can be sent to the server in subsequent responses in the <code>options</code> table to any function (see below).
-- * <code>body</code>: The body of the response
-- * <code>location</code>: a list of the locations of redirects that were followed.
--
-- Many of the functions optionally allow an 'options' table. This table can alter the HTTP headers
-- or other values like the timeout. The following are valid values in 'options' (note: not all
-- options will necessarily affect every function):
-- * <code>timeout</code>: A timeout used for socket operations.
-- * <code>header</code>: A table containing additional headers to be used for the request. For example, <code>options['header']['Content-Type'] = 'text/xml'</code>
-- * <code>content</code>: The content of the message (content-length will be added -- set header['Content-Length'] to override). This can be either a string, which will be directly added as the body of the message, or a table, which will have each key=value pair added (like a normal POST request).
-- * <code>cookies</code>: A list of cookies as either a string, which will be directly sent, or a table. If it's a table, the following fields are recognized: <code>name</code>, <code>value</code>, <code>path</code>, <code>expires</code>. Only <code>name</code> and <code>value</code> fields are required.
-- * <code>auth</code>: A table containing the keys <code>username</code> and <code>password</code>, which will be used for HTTP Basic authentication.
--   If a server requires HTTP Digest authentication, then there must also be a key <code>digest</code>, with value <code>true</code>.
--   If a server requires NTLM authentication, then there must also be a key <code>ntlm</code>, with value <code>true</code>.
-- * <code>bypass_cache</code>: Do not perform a lookup in the local HTTP cache.
-- * <code>no_cache</code>: Do not save the result of this request to the local HTTP cache.
-- * <code>no_cache_body</code>: Do not save the body of the response to the local HTTP cache.
-- * <code>redirect_ok</code>: Closure that overrides the default redirect_ok used to validate whether to follow HTTP redirects or not. False, if no HTTP redirects should be followed. Alternatively, a number may be passed to change the number of redirects to follow.
--   The following example shows how to write a custom closure that follows 5 consecutive redirects, without the safety checks in the default redirect_ok:
--   <code>
--   redirect_ok = function(host,port)
--     local c = 5
--     return function(url)
--       if ( c==0 ) then return false end
--       c = c - 1
--       return true
--     end
--   end
--   </code>
--
-- @args http.max-cache-size The maximum memory size (in bytes) of the cache.
--
-- @args http.useragent The value of the User-Agent header field sent with
-- requests. By default it is
-- <code>"Mozilla/5.0 (compatible; Nmap Scripting Engine; http://nmap.org/book/nse.html)"</code>.
-- A value of the empty string disables sending the User-Agent header field.
--
-- @args http.pipeline If set, it represents the number of HTTP requests that'll be
-- sent on one connection. This can be set low to make debugging easier, or it
-- can be set high to test how a server reacts (its chosen max is ignored).
-- @args http.max-pipeline If set, it represents the number of outstanding  HTTP requests
-- that should be pipelined. Defaults to <code>http.pipeline</code> (if set), or to what
-- <code>getPipelineMax</code> function returns.
--
-- TODO
-- Implement cache system for http pipelines
--


local base64 = require "base64"
local bin = require "bin"
local bit = require "bit"
local comm = require "comm"
local coroutine = require "coroutine"
local nmap = require "nmap"
local os = require "os"
local sasl = require "sasl"
local stdnse = require "stdnse"
local string = require "string"
local table = require "table"
local url = require "url"
local smbauth = require "smbauth"
local unicode = require "unicode"
_ENV = stdnse.module("http", stdnse.seeall)

---Use ssl if we have it
local have_ssl, openssl = pcall(require,'openssl')

USER_AGENT = stdnse.get_script_args('http.useragent') or "Mozilla/5.0 (compatible; Nmap Scripting Engine; http://nmap.org/book/nse.html)"
local MAX_REDIRECT_COUNT = 5

-- Recursively copy a table.
-- Only recurs when a value is a table, other values are copied by assignment.
local function tcopy (t)
  local tc = {};
  for k,v in pairs(t) do
    if type(v) == "table" then
      tc[k] = tcopy(v);
    else
      tc[k] = v;
    end
  end
  return tc;
end

--- Recursively copy into a table any elements from another table whose key it
-- doesn't have.
local function table_augment(to, from)
  for k, v in pairs(from) do
    if type( to[k] ) == 'table' then
      table_augment(to[k], from[k])
    else
      to[k] = from[k]
    end
  end
end

--- Get a value suitable for the Host header field.
-- See RFC 2616 sections 14.23 and 5.2.
local function get_host_field(host, port)
  return stdnse.get_hostname(host)
end

-- Skip *( SP | HT ) starting at offset. See RFC 2616, section 2.2.
-- @return the first index following the spaces.
-- @return the spaces skipped over.
local function skip_space(s, offset)
  local _, i, space = s:find("^([ \t]*)", offset)
  return i + 1, space
end

-- Get a token starting at offset. See RFC 2616, section 2.2.
-- @return the first index following the token, or nil if no token was found.
-- @return the token.
local function get_token(s, offset)
  -- All characters except CTL and separators.
  local _, i, token = s:find("^([^()<>@,;:\\\"/%[%]?={} \0\001-\031\127]+)", offset)
  if i then
    return i + 1, token
  else
    return nil
  end
end

-- Get a quoted-string starting at offset. See RFC 2616, section 2.2. crlf is
-- used as the definition for CRLF in the case of LWS within the string.
-- @return the first index following the quoted-string, or nil if no
-- quoted-string was found.
-- @return the contents of the quoted-string, without quotes or backslash
-- escapes.
local function get_quoted_string(s, offset, crlf)
  local result = {}
  local i = offset
  assert(s:sub(i, i) == "\"")
  i = i + 1
  while i <= s:len() do
    local c = s:sub(i, i)
    if c == "\"" then
      -- Found the closing quote, done.
      return i + 1, table.concat(result)
    elseif c == "\\" then
      -- This is a quoted-pair ("\" CHAR).
      i = i + 1
      c = s:sub(i, i)
      if c == "" then
        -- No character following.
        error(string.format("\\ escape at end of input while parsing quoted-string."))
      end
      -- Only CHAR may follow a backslash.
      if c:byte(1) > 127 then
        error(string.format("Unexpected character with value > 127 (0x%02X) in quoted-string.", c:byte(1)))
      end
    else
      -- This is qdtext, which is TEXT except for '"'.
      -- TEXT is "any OCTET except CTLs, but including LWS," however "a CRLF is
      -- allowed in the definition of TEXT only as part of a header field
      -- continuation." So there are really two definitions of quoted-string,
      -- depending on whether it's in a header field or not. This function does
      -- not allow CRLF.
      c = s:sub(i, i)
      if c ~= "\t" and c:match("^[\0\001-\031\127]$") then
        error(string.format("Unexpected control character in quoted-string: 0x%02X.", c:byte(1)))
      end
    end
    result[#result + 1] = c
    i = i + 1
  end
  return nil
end

-- Get a ( token | quoted-string ) starting at offset.
-- @return the first index following the token or quoted-string, or nil if
-- nothing was found.
-- @return the token or quoted-string.
local function get_token_or_quoted_string(s, offset, crlf)
  if s:sub(offset, offset) == "\"" then
    return get_quoted_string(s, offset)
  else
    return get_token(s, offset)
  end
end

-- Returns the index just past the end of LWS.
local function skip_lws(s, pos)
  local _, e

  while true do
    while string.match(s, "^[ \t]", pos) do
      pos = pos + 1
    end
    _, e = string.find(s, "^\r?\n[ \t]", pos)
    if not e then
      return pos
    end
    pos = e + 1
  end
end


---Validate an 'options' table, which is passed to a number of the HTTP functions. It is
-- often difficult to track down a mistake in the options table, and requires fiddling
-- with the http.lua source, but this should make that a lot easier.
local function validate_options(options)
  local bad = false

  if(options == nil) then
    return true
  end

  for key, value in pairs(options) do
    if(key == 'timeout') then
      if(type(tonumber(value)) ~= 'number') then
        stdnse.debug1('http: options.timeout contains a non-numeric value')
        bad = true
      end
    elseif(key == 'header') then
      if(type(value) ~= 'table') then
        stdnse.debug1("http: options.header should be a table")
        bad = true
      end
    elseif(key == 'content') then
      if(type(value) ~= 'string' and type(value) ~= 'table') then
        stdnse.debug1("http: options.content should be a string or a table")
        bad = true
      end
    elseif(key == 'cookies') then
      if(type(value) == 'table') then
        for _, cookie in ipairs(value) do
          for cookie_key, cookie_value in pairs(cookie) do
            if(cookie_key == 'name') then
              if(type(cookie_value) ~= 'string') then
                stdnse.debug1("http: options.cookies[i].name should be a string")
                bad = true
              end
            elseif(cookie_key == 'value') then
              if(type(cookie_value) ~= 'string') then
                stdnse.debug1("http: options.cookies[i].value should be a string")
                bad = true
              end
            elseif(cookie_key == 'path') then
              if(type(cookie_value) ~= 'string') then
                stdnse.debug1("http: options.cookies[i].path should be a string")
                bad = true
              end
            elseif(cookie_key == 'expires') then
              if(type(cookie_value) ~= 'string') then
                stdnse.debug1("http: options.cookies[i].expires should be a string")
                bad = true
              end
            else
              stdnse.debug1("http: Unknown field in cookie table: %s", cookie_key)
              bad = true
            end
          end
        end
      elseif(type(value) ~= 'string') then
        stdnse.debug1("http: options.cookies should be a table or a string")
        bad = true
      end
    elseif(key == 'auth') then
      if(type(value) == 'table') then
        if(value['username'] == nil or value['password'] == nil) then
          stdnse.debug1("http: options.auth should contain both a 'username' and a 'password' key")
          bad = true
        end
      else
        stdnse.debug1("http: options.auth should be a table")
        bad = true
      end
    elseif (key == 'digestauth') then
      if(type(value) == 'table') then
        local req_keys = {"username","realm","nonce","digest-uri","response"}
        for _,k in ipairs(req_keys) do
          if not value[k] then
            stdnse.debug1("http: options.digestauth missing key: %s",k)
            bad = true
            break
          end
        end
      else
        bad = true
        stdnse.debug1("http: options.digestauth should be a table")
      end
    elseif (key == 'ntlmauth') then
      stdnse.debug1("Proceeding with ntlm message")
    elseif(key == 'bypass_cache' or key == 'no_cache' or key == 'no_cache_body') then
      if(type(value) ~= 'boolean') then
        stdnse.debug1("http: options.bypass_cache, options.no_cache, and options.no_cache_body must be boolean values")
        bad = true
      end
    elseif(key == 'redirect_ok') then
      if(type(value)~= 'function' and type(value)~='boolean' and type(value) ~= 'number') then
        stdnse.debug1("http: options.redirect_ok must be a function or boolean or number")
        bad = true
      end
    else
      stdnse.debug1("http: Unknown key in the options table: %s", key)
    end
  end

  return not(bad)
end


-- The following recv functions, and the function <code>next_response</code>
-- follow a common pattern. They each take a <code>partial</code> argument
-- whose value is data that has been read from the socket but not yet used in
-- parsing, and they return as their second return value a new value for
-- <code>partial</code>. The idea is that, for example, in reading from the
-- socket to get the Status-Line, you will probably read too much and read part
-- of the header. That part (the "partial") has to be retained when you go to
-- parse the header. The common use pattern is this:
-- <code>
-- local partial
-- status_line, partial = recv_line(socket, partial)
-- ...
-- header, partial = recv_header(socket, partial)
-- ...
-- </code>
-- On error, the functions return <code>nil</code> and the second return value
-- is an error message.

-- Receive a single line (up to <code>\n</code>).
local function recv_line(s, partial)
  local _, e
  local status, data
  local pos

  partial = partial or ""

  pos = 1
  while true do
    _, e = string.find(partial, "\n", pos, true)
    if e then
      break
    end
    status, data = s:receive()
    if not status then
      return status, data
    end
    pos = #partial
    partial = partial .. data
  end

  return string.sub(partial, 1, e), string.sub(partial, e + 1)
end

local function line_is_empty(line)
  return line == "\r\n" or line == "\n"
end

-- Receive up to and including the first blank line, but return everything up
-- to and not including the final blank line.
local function recv_header(s, partial)
  local lines = {}

  partial = partial or ""

  while true do
    local line
    line, partial = recv_line(s, partial)
    if not line then
      return line, partial
    end
    if line_is_empty(line) then
      break
    end
    lines[#lines + 1] = line
  end

  return table.concat(lines), partial
end

-- Receive until the connection is closed.
local function recv_all(s, partial)
  local parts

  partial = partial or ""

  parts = {partial}
  while true do
    local status, part = s:receive()
    if not status then
      break
    else
      parts[#parts + 1] = part
    end
  end

  return table.concat(parts), ""
end

-- Receive exactly <code>length</code> bytes. Returns <code>nil</code> if that
-- many aren't available.
local function recv_length(s, length, partial)
  local parts, last

  partial = partial or ""

  parts = {}
  last = partial
  length = length - #last
  while length > 0 do
    local status

    parts[#parts + 1] = last
    status, last = s:receive()
    if not status then
      return nil
    end
    length = length - #last
  end

  -- At this point length is 0 or negative, and indicates the degree to which
  -- the last read "overshot" the desired length.

  if length == 0 then
    return table.concat(parts) .. last, ""
  else
    return table.concat(parts) .. string.sub(last, 1, length - 1), string.sub(last, length)
  end
end

-- Receive until the end of a chunked message body, and return the dechunked
-- body.
local function recv_chunked(s, partial)
  local chunks, chunk
  local chunk_size
  local pos

  chunks = {}
  repeat
    local line, hex, _, i

    line, partial = recv_line(s, partial)
    if not line then
      return nil, partial
    end

    pos = 1
    pos = skip_space(line, pos)

    -- Get the chunk-size.
    _, i, hex = string.find(line, "^([%x]+)", pos)
    if not i then
      return nil, string.format("Chunked encoding didn't find hex; got %q.", string.sub(line, pos, pos + 10))
    end
    pos = i + 1

    chunk_size = tonumber(hex, 16)
    if not chunk_size or chunk_size < 0 then
      return nil, string.format("Chunk size %s is not a positive integer.", hex)
    end

    -- Ignore chunk-extensions that may follow here.
    -- RFC 2616, section 2.1 ("Implied *LWS") seems to allow *LWS between the
    -- parts of a chunk-extension, but that is ambiguous. Consider this case:
    -- "1234;a\r\n =1\r\n...". It could be an extension with a chunk-ext-name
    -- of "a" (and no value), and a chunk-data beginning with " =", or it could
    -- be a chunk-ext-name of "a" with a value of "1", and a chunk-data
    -- starting with "...". We don't allow *LWS here, only ( SP | HT ), so the
    -- first interpretation will prevail.

    chunk, partial = recv_length(s, chunk_size, partial)
    if not chunk then
      return nil, partial
    end
    chunks[#chunks + 1] = chunk

    line, partial = recv_line(s, partial)
    if not line then
      -- this warning message was initially an error but was adapted
      -- to support broken servers, such as the Citrix XML Service
      stdnse.debug2("Didn't find CRLF after chunk-data.")
    elseif not string.match(line, "^\r?\n") then
      return nil, string.format("Didn't find CRLF after chunk-data; got %q.", line)
    end
  until chunk_size == 0

  return table.concat(chunks), partial
end

-- Receive a message body, assuming that the header has already been read by
-- <code>recv_header</code>. The handling is sensitive to the request method
-- and the status code of the response.
local function recv_body(s, response, method, partial)
  local connection_close, connection_keepalive
  local version_major, version_minor
  local transfer_encoding
  local content_length
  local err

  partial = partial or ""

  -- First check for Connection: close and Connection: keep-alive. This is
  -- necessary to handle some servers that don't follow the protocol.
  connection_close = false
  connection_keepalive = false
  if response.header.connection then
    local offset, token
    offset = 0
    while true do
      offset, token = get_token(response.header.connection, offset + 1)
      if not offset then
        break
      end
      if string.lower(token) == "close" then
        connection_close = true
      elseif string.lower(token) == "keep-alive" then
        connection_keepalive = true
      end
    end
  end

  -- The HTTP version may also affect our decisions.
  version_major, version_minor = string.match(response["status-line"], "^HTTP/(%d+)%.(%d+)")

  -- See RFC 2616, section 4.4 "Message Length".

  -- 1. Any response message which "MUST NOT" include a message-body (such as
  --    the 1xx, 204, and 304 responses and any response to a HEAD request) is
  --    always terminated by the first empty line after the header fields...
  --
  -- Despite the above, some servers return a body with response to a HEAD
  -- request. So if an HTTP/1.0 server returns a response without Connection:
  -- keep-alive, or any server returns a response with Connection: close, read
  -- whatever's left on the socket (should be zero bytes).
  if string.upper(method) == "HEAD"
    or (response.status >= 100 and response.status <= 199)
    or response.status == 204 or response.status == 304 then
    if connection_close or (version_major == "1" and version_minor == "0" and not connection_keepalive) then
      return recv_all(s, partial)
    else
      return "", partial
    end
  end

  -- 2. If a Transfer-Encoding header field (section 14.41) is present and has
  --    any value other than "identity", then the transfer-length is defined by
  --    use of the "chunked" transfer-coding (section 3.6), unless the message
  --    is terminated by closing the connection.
  if response.header["transfer-encoding"]
    and response.header["transfer-encoding"] ~= "identity" then
    return recv_chunked(s, partial)
  end
  -- The Citrix XML Service sends a wrong "Transfer-Coding" instead of
  -- "Transfer-Encoding".
  if response.header["transfer-coding"]
    and response.header["transfer-coding"] ~= "identity" then
    return recv_chunked(s, partial)
  end

  -- 3. If a Content-Length header field (section 14.13) is present, its decimal
  --    value in OCTETs represents both the entity-length and the
  --    transfer-length. The Content-Length header field MUST NOT be sent if
  --    these two lengths are different (i.e., if a Transfer-Encoding header
  --    field is present). If a message is received with both a
  --    Transfer-Encoding header field and a Content-Length header field, the
  --    latter MUST be ignored.
  if response.header["content-length"]  and not response.header["transfer-encoding"] then
    content_length = tonumber(response.header["content-length"])
    if not content_length then
      return nil, string.format("Content-Length %q is non-numeric", response.header["content-length"])
    end
    return recv_length(s, content_length, partial)
  end

  -- 4. If the message uses the media type "multipart/byteranges", and the
  --    transfer-length is not otherwise specified, then this self-delimiting
  --    media type defines the transfer-length. [sic]

  -- Case 4 is unhandled.

  -- 5. By the server closing the connection.
  return recv_all(s, partial)
end

-- Sets response["status-line"] and response.status.
local function parse_status_line(status_line, response)
  local version, status, reason_phrase

  response["status-line"] = status_line
  version, status, reason_phrase = string.match(status_line,
    "^HTTP/(%d%.%d) *(%d+) *(.*)\r?\n$")
  if not version then
    return nil, string.format("Error parsing status-line %q.", status_line)
  end
  -- We don't have a use for the version; ignore it.
  response.status = tonumber(status)
  if not response.status then
    return nil, string.format("Status code is not numeric: %s", status)
  end

  return true
end

-- Sets response.header and response.rawheader.
local function parse_header(header, response)
  local pos
  local name, words
  local s, e

  response.header = {}
  response.rawheader = stdnse.strsplit("\r?\n", header)
  pos = 1
  while pos <= #header do
    -- Get the field name.
    e, name = get_token(header, pos)
    if not name or e > #header or string.sub(header, e, e) ~= ":" then
      return nil, string.format("Can't get header field name at %q", string.sub(header, pos, pos + 30))
    end
    pos = e + 1

    -- Skip initial space.
    pos = skip_lws(header, pos)
    -- Get non-space words separated by LWS, then join them with a single space.
    words = {}
    while pos <= #header and not string.match(header, "^\r?\n", pos) do
      s = pos
      while not string.match(header, "^[ \t]", pos) and
        not string.match(header, "^\r?\n", pos) do
        pos = pos + 1
      end
      words[#words + 1] = string.sub(header, s, pos - 1)
      pos = skip_lws(header, pos)
    end

    -- Set it in our table.
    name = string.lower(name)
    if response.header[name] then
      response.header[name] = response.header[name] .. ", " .. table.concat(words, " ")
    else
      response.header[name] = table.concat(words, " ")
    end

    -- Next field, or end of string. (If not it's an error.)
    s, e = string.find(header, "^\r?\n", pos)
    if not e then
      return nil, string.format("Header field named %q didn't end with CRLF", name)
    end
    pos = e + 1
  end

  return true
end

-- Parse the contents of a Set-Cookie header field. The result is an array
-- containing tables of the form
--
-- { name = "NAME", value = "VALUE", Comment = "...", Domain = "...", ... }
--
-- Every key except "name" and "value" is optional.
--
-- This function attempts to support the cookie syntax defined in RFC 2109
-- along with the backwards-compatibility suggestions from its section 10,
-- "HISTORICAL". Values need not be quoted, but if they start with a quote they
-- will be interpreted as a quoted string.
local function parse_set_cookie(s)
  local cookies
  local name, value
  local _, pos

  cookies = {}

  pos = 1
  while true do
    local cookie = {}

    -- Get the NAME=VALUE part.
    pos = skip_space(s, pos)
    pos, cookie.name = get_token(s, pos)
    if not cookie.name then
      return nil, "Can't get cookie name."
    end
    pos = skip_space(s, pos)
    if pos > #s or string.sub(s, pos, pos) ~= "=" then
      return nil, string.format("Expected '=' after cookie name \"%s\".", cookie.name)
    end
    pos = pos + 1
    pos = skip_space(s, pos)
    if string.sub(s, pos, pos) == "\"" then
      pos, cookie.value = get_quoted_string(s, pos)
    else
      _, pos, cookie.value = string.find(s, "([^;]*)[ \t]*", pos)
      pos = pos + 1
    end
    if not cookie.value then
      return nil, string.format("Can't get value of cookie named \"%s\".", cookie.name)
    end
    pos = skip_space(s, pos)

    -- Loop over the attributes.
    while pos <= #s and string.sub(s, pos, pos) == ";" do
      pos = pos + 1
      pos = skip_space(s, pos)
      pos, name = get_token(s, pos)
      if not name then
        return nil, string.format("Can't get attribute name of cookie \"%s\".", cookie.name)
      end
      pos = skip_space(s, pos)
      if pos <= #s and string.sub(s, pos, pos) == "=" then
        pos = pos + 1
        pos = skip_space(s, pos)
        if string.sub(s, pos, pos) == "\"" then
          pos, value = get_quoted_string(s, pos)
        else
          -- account for the possibility of the expires attribute being empty or improperly formatted
          local last_pos = pos

         if string.lower(name) == "expires" then
            -- For version 0 cookies we must allow one comma for "expires".
            _, pos, value = string.find(s, "([^,]*,[^;,]*)[ \t]*", pos)
          else
            _, pos, value = string.find(s, "([^;,]*)[ \t]*", pos)
          end

          -- account for the possibility of the expires attribute being empty or improperly formatted
          if ( not(pos) ) then
            _, pos, value = s:find("([^;]*)", last_pos)
          end

          pos = pos + 1
        end
        if not value then
          return nil, string.format("Can't get value of cookie attribute \"%s\".", name)
        end
      else
        value = true
      end
      cookie[name:lower()] = value
      pos = skip_space(s, pos)
    end

    cookies[#cookies + 1] = cookie

    if pos > #s then
      break
    end

    if string.sub(s, pos, pos) ~= "," then
      return nil, string.format("Syntax error after cookie named \"%s\".", cookie.name)
    end

    pos = pos + 1
    pos = skip_space(s, pos)
  end

  return cookies
end

-- Read one response from the socket <code>s</code> and return it after
-- parsing.
local function next_response(s, method, partial)
  local response
  local status_line, header, body
  local status, err

  partial = partial or ""
  response = {
    status=nil,
    ["status-line"]=nil,
    header={},
    rawheader={},
    body=""
  }

  status_line, partial = recv_line(s, partial)
  if not status_line then
    return nil, partial
  end
  status, err = parse_status_line(status_line, response)
  if not status then
    return nil, err
  end

  header, partial = recv_header(s, partial)
  if not header then
    return nil, partial
  end
  status, err = parse_header(header, response)
  if not status then
    return nil, err
  end

  body, partial = recv_body(s, response, method, partial)
  if not body then
    return nil, partial
  end
  response.body = body

  -- We have the Status-Line, header, and body; now do any postprocessing.

  response.cookies = {}
  if response.header["set-cookie"] then
    response.cookies, err = parse_set_cookie(response.header["set-cookie"])
    if not response.cookies then
      -- Ignore a cookie parsing error.
      response.cookies = {}
    end
  end

  return response, partial
end

--- Tries to extract the max number of requests that should be made on
--  a keep-alive connection based on "Keep-Alive: timeout=xx,max=yy" response
--  header.
--
--  If the value is not available, an arbitrary value is used. If the connection
--  is not explicitly closed by the server, this same value is attempted.
--
--  @param response The http response - Might be a table or a raw response
--  @return The max number of requests on a keep-alive connection
local function getPipelineMax(response)
  -- Allow users to override this with a script-arg
  local pipeline = stdnse.get_script_args({'http.pipeline', 'pipeline'})

  if(pipeline) then
    return tonumber(pipeline)
  end

  if response then
    if response.header and response.header.connection ~= "close" then
      if response.header["keep-alive"] then
        local max = string.match( response.header["keep-alive"], "max=(%d*)")
        if(max == nil) then
          return 40
        end
        return tonumber(max)
      else
        return 40
      end
    end
  end
  return 1
end

--- Builds a string to be added to the request mod_options table
--
--  @param cookies A cookie jar just like the table returned parse_set_cookie.
--  @param path If the argument exists, only cookies with this path are included to the request
--  @return A string to be added to the mod_options table
local function buildCookies(cookies, path)
  local cookie = ""
  if type(cookies) == 'string' then return cookies end
  for _, ck in ipairs(cookies or {}) do
    local ckpath = ck["path"]
    if not path or not ckpath
      or ckpath == path
      or ckpath:sub(-1) == "/" and ckpath == path:sub(1, ckpath:len())
      or ckpath .. "/" == path:sub(1, ckpath:len()+1)
      then
        cookie = cookie .. ck["name"] .. "=" .. ck["value"] .. "; "
      end
    end
  return cookie:gsub("; $","")
end

-- HTTP cache.
-- Cache of GET and HEAD requests. Uses <"host:port:path", record>.
-- record is in the format:
--   result: The result from http.get or http.head
--   last_used: The time the record was last accessed or made.
--   get: Was the result received from a request to get or recently wiped?
--   size: The size of the record, equal to #record.result.body.
local cache = {size = 0};

local function check_size (cache)
  local max_size = tonumber(stdnse.get_script_args({'http.max-cache-size', 'http-max-cache-size'}) or 1e6);

  local size = cache.size;

  if size > max_size then
    stdnse.debug1(
        "Current http cache size (%d bytes) exceeds max size of %d",
        size, max_size);
    table.sort(cache, function(r1, r2)
      return (r1.last_used or 0) < (r2.last_used or 0);
    end);

    for i, record in ipairs(cache) do
      if size <= max_size then break end
      local result = record.result;
      if type(result.body) == "string" then
        size = size - record.size;
        record.size, record.get, result.body = 0, false, "";
      end
    end
    cache.size = size;
  end
  stdnse.debug2("Final http cache size (%d bytes) of max size of %d",
      size, max_size);
  return size;
end

-- Unique value to signal value is being retrieved.
-- Also holds <mutex, thread> pairs, working thread is value
local WORKING = setmetatable({}, {__mode = "v"});

local function lookup_cache (method, host, port, path, options)
  if(not(validate_options(options))) then
    return nil
  end

  options = options or {};
  local bypass_cache = options.bypass_cache; -- do not lookup
  local no_cache = options.no_cache; -- do not save result
  local no_cache_body = options.no_cache_body; -- do not save body

  if type(port) == "table" then port = port.number end

  local key = stdnse.get_hostname(host)..":"..port..":"..path;
  local mutex = nmap.mutex(tostring(lookup_cache)..key);

  local state = {
    mutex = mutex,
    key = key,
    method = method,
    bypass_cache = bypass_cache,
    no_cache = no_cache,
    no_cache_body = no_cache_body,
  };

  while true do
    mutex "lock";
    local record = cache[key];
    if bypass_cache or record == nil or method ~= record.method then
      WORKING[mutex] = coroutine.running();
      cache[key], state.old_record = WORKING, record;
      return nil, state;
    elseif record == WORKING then
      local working = WORKING[mutex];
      if working == nil or coroutine.status(working) == "dead" then
        -- thread died before insert_cache could be called
        cache[key] = nil; -- reset
      end
      mutex "done";
    else
      mutex "done";
      record.last_used = os.time();
      return tcopy(record.result), state;
    end
  end
end

local function response_is_cacheable(response)
  -- if response.status is nil, then an error must have occurred during the request
  -- and we probably don't want to cache the response
  if not response.status then
    return false
  end

  -- 206 Partial Content. RFC 2616, 1.34: "...a cache that does not support the
  -- Range and Content-Range headers MUST NOT cache 206 (Partial Content)
  -- responses."
  if response.status == 206 then
    return false
  end

  -- RFC 2616, 13.4. "A response received with any [status code other than 200,
  -- 203, 206, 300, 301 or 410] (e.g. status codes 302 and 307) MUST NOT be
  -- returned in a reply to a subsequent request unless there are cache-control
  -- directives or another header(s) that explicitly allow it."
  -- We violate the standard here and allow these other codes to be cached,
  -- with the exceptions listed below.

  -- 401 Unauthorized. Caching this would prevent us from retrieving it later
  -- with the correct credentials.
  if response.status == 401 then
    return false
  end

  return true
end

local function insert_cache (state, response)
  local key = assert(state.key);
  local mutex = assert(state.mutex);

  if response == nil or state.no_cache or not response_is_cacheable(response) then
    cache[key] = state.old_record;
  else
    local record = {
      result = tcopy(response),
      last_used = os.time(),
      method = state.method,
      size = type(response.body) == "string" and #response.body or 0,
    };
    response = record.result; -- only modify copy
    cache[key], cache[#cache+1] = record, record;
    if state.no_cache_body then
      response.body = "";
    end
    if type(response.body) == "string" then
      cache.size = cache.size + #response.body;
      check_size(cache);
    end
  end
  mutex "done";
end

-- Return true if the given method requires a body in the request. In case no
-- body was supplied we must send "Content-Length: 0".
local function request_method_needs_content_length(method)
  return method == "POST"
end

-- For each of the following request functions, <code>host</code> may either be
-- a string or a table, and <code>port</code> may either be a number or a
-- table.
--
-- The format of the return value is a table with the following structure:
-- {status = 200, status-line = "HTTP/1.1 200 OK", header = {}, rawheader = {}, body ="<html>...</html>"}
-- The header table has an entry for each received header with the header name
-- being the key. The table also has an entry named "status" which contains the
-- http status code of the request.
-- In case of an error, the status is nil and status-line describes the problem.

local function http_error(status_line)
  return {
    status = nil,
    ["status-line"] = status_line,
    header = {},
    rawheader = {},
    body = nil,
  }
end

--- Build an HTTP request from parameters and return it as a string.
--
-- @param host The host this request is intended for.
-- @param port The port this request is intended for.
-- @param method The method to use.
-- @param path The path for the request.
-- @param options A table of options, which may include the keys:
-- * <code>header</code>: A table containing additional headers to be used for the request.
-- * <code>content</code>: The content of the message (content-length will be added -- set header['Content-Length'] to override)
-- * <code>cookies</code>: A table of cookies in the form returned by <code>parse_set_cookie</code>.
-- * <code>auth</code>: A table containing the keys <code>username</code> and <code>password</code>.
-- @return A request string.
-- @see generic_request
local function build_request(host, port, method, path, options)
  if(not(validate_options(options))) then
    return nil
  end
  options = options or {}

  -- Private copy of the options table, used to add default header fields.
  local mod_options = {
    header = {
      Connection = "close",
      Host = get_host_field(host, port),
      ["User-Agent"]  = USER_AGENT
    }
  }

  if options.cookies then
    local cookies = buildCookies(options.cookies, path)
    if #cookies > 0 then
      mod_options.header["Cookie"] = cookies
    end
  end

  if options.auth and not (options.auth.digest or options.auth.ntlm) then
    local username = options.auth.username
    local password = options.auth.password
    local credentials = "Basic " .. base64.enc(username .. ":" .. password)
    mod_options.header["Authorization"] = credentials
  end

  if options.digestauth then
    local order = {"username", "realm", "nonce", "digest-uri", "algorithm", "response", "qop", "nc", "cnonce"}
    local no_quote = {algorithm=true, qop=true, nc=true}
    local creds = {}
    for _,k in ipairs(order) do
      local v = options.digestauth[k]
      if v then
        if no_quote[k] then
          table.insert(creds, ("%s=%s"):format(k,v))
        else
          if k == "digest-uri" then
            table.insert(creds, ('%s="%s"'):format("uri",v))
          else
            table.insert(creds, ('%s="%s"'):format(k,v))
          end
        end
      end
    end
    local credentials = "Digest "..table.concat(creds, ", ")
    mod_options.header["Authorization"] = credentials
  end

  if options.ntlmauth then
    mod_options.header["Authorization"] = "NTLM " .. base64.enc(options.ntlmauth)
  end


  local body
  -- Build a form submission from a table, like "k1=v1&k2=v2".
  if type(options.content) == "table" then
    local parts = {}
    local k, v
    for k, v in pairs(options.content) do
      parts[#parts + 1] = url.escape(k) .. "=" .. url.escape(v)
    end
    body = table.concat(parts, "&")
    mod_options.header["Content-Type"] = "application/x-www-form-urlencoded"
  elseif options.content then
    body = options.content
  elseif request_method_needs_content_length(method) then
    body = ""
  end
  if body then
    mod_options.header["Content-Length"] = #body
  end

  -- Add any other header fields into the local copy.
  table_augment(mod_options, options)
  -- We concat this string manually to allow null bytes in requests
  local request_line = method.." "..path.." HTTP/1.1"
  local header = {}
  for name, value in pairs(mod_options.header) do
    -- we concat this string manually to allow null bytes in requests
    header[#header + 1] = name..": "..value
  end

  return request_line .. "\r\n" .. stdnse.strjoin("\r\n", header) .. "\r\n\r\n" .. (body or "")
end

--- Send a string to a host and port and return the HTTP result. This function
-- is like <code>generic_request</code>, to be used when you have a ready-made
-- request, not a collection of request parameters.
--
-- @param host The host to connect to.
-- @param port The port to connect to.
-- @param options A table of other parameters. It may have any of these fields:
-- * <code>timeout</code>: A timeout used for socket operations.
-- * <code>header</code>: A table containing additional headers to be used for the request.
-- * <code>content</code>: The content of the message (content-length will be added -- set header['Content-Length'] to override)
-- * <code>cookies</code>: A table of cookies in the form returned by <code>parse_set_cookie</code>.
-- * <code>auth</code>: A table containing the keys <code>username</code> and <code>password</code>.
-- @return A response table, see module documentation for description.
-- @see generic_request
local function request(host, port, data, options)
  if(not(validate_options(options))) then
    return http_error("Options failed to validate.")
  end
  local method
  local header
  local response

  options = options or {}

  if type(port) == 'table' then
    if port.protocol and port.protocol ~= 'tcp' then
      stdnse.debug1("http.request() supports the TCP protocol only, your request to %s cannot be completed.", host)
      return http_error("Unsupported protocol.")
    end
  end

  method = string.match(data, "^(%S+)")

  local socket, partial, opts = comm.tryssl(host, port, data, { timeout = options.timeout })

  if not socket then
    return http_error("Error creating socket.")
  end

  repeat
    response, partial = next_response(socket, method, partial)
    if not response then
      return http_error("There was an error in next_response function.")
    end
    -- See RFC 2616, sections 8.2.3 and 10.1.1, for the 100 Continue status.
    -- Sometimes a server will tell us to "go ahead" with a POST body before
    -- sending the real response. If we got one of those, skip over it.
  until not (response.status >= 100 and response.status <= 199)

  socket:close()

  -- if SSL was used to retrieve the URL mark this in the response
  response.ssl = ( opts == 'ssl' )

  return response
end

---Do a single request with a given method. The response is returned as the standard
-- response table (see the module documentation).
--
-- The <code>get</code>, <code>head</code>, and <code>post</code> functions are simple
-- wrappers around <code>generic_request</code>.
--
-- Any 1XX (informational) responses are discarded.
--
-- @param host The host to connect to.
-- @param port The port to connect to.
-- @param method The method to use; for example, 'GET', 'HEAD', etc.
-- @param path The path to retrieve.
-- @param options [optional] A table that lets the caller control socket timeouts, HTTP headers, and other parameters. For full documentation, see the module documentation (above).
-- @return A response table, see module documentation for description.
-- @see request
function generic_request(host, port, method, path, options)
  if(not(validate_options(options))) then
    return http_error("Options failed to validate.")
  end

  local digest_auth = options and options.auth and options.auth.digest
  local ntlm_auth = options and options.auth and options.auth.ntlm

  if (digest_auth or ntlm_auth) and not have_ssl then
    stdnse.debug1("http: digest and ntlm auth require openssl.")
  end

  if digest_auth and have_ssl then
    -- If we want to do digest authentication, we have to make an initial
    -- request to get realm, nonce and other fields.
    local options_with_auth_removed = tcopy(options)
    options_with_auth_removed["auth"] = nil
    local r = generic_request(host, port, method, path, options_with_auth_removed)
    local h = r.header['www-authenticate']
    if not r.status or (h and not string.find(h:lower(), "digest.-realm")) then
      stdnse.debug1("http: the target doesn't support digest auth or there was an error during request.")
      return http_error("The target doesn't support digest auth or there was an error during request.")
    end
    -- Compute the response hash
    local dmd5 = sasl.DigestMD5:new(h, options.auth.username, options.auth.password, method, path)
    local _, digest_table = dmd5:calcDigest()
    options.digestauth = digest_table
  end

  if ntlm_auth and have_ssl then

    local custom_options = tcopy(options) -- to be sent with the type 1 request
    custom_options["auth"] = nil -- removing the auth options
    -- let's check if the target supports ntlm with a simple get request.
    -- Setting a timeout here other than nil messes up the authentication if this is the first device sending
    -- a request to the server. Don't know why.
    custom_options.timeout = nil
    local response = generic_request(host, port, method, path, custom_options)
    local authentication_header = response.header['www-authenticate']
    -- get back the timeout option.
    custom_options.timeout = options.timeout
    custom_options.header = options.header or {}
    custom_options.header["Connection"] = "Keep-Alive" -- Keep-Alive headers are needed for authentication.

    if (not authentication_header) or (not response.status) or (not string.find(authentication_header:lower(), "ntlm")) then
      stdnse.debug1("http: the target doesn't support NTLM or there was an error during request.")
      return http_error("The target doesn't support NTLM or there was an error during request.")
    end

    -- ntlm works with three messages. we send a request, it sends
    -- a challenge, we respond to the challenge.
    local hostname = options.auth.hostname or "localhost" -- the hostname to be sent
    local workstation_name = options.auth.workstation_name or "NMAP" -- the workstation name to be sent
    local username = options.auth.username -- the username as specified

    local auth_blob = "NTLMSSP\x00" .. -- NTLM signature
    "\x01\x00\x00\x00" .. -- NTLM Type 1 message
    bin.pack("<I", 0xa208b207) .. -- flags 56, 128, Version, Extended Security, Always Sign, Workstation supplied, Domain Supplied, NTLM Key, OEM, Unicode 
    bin.pack("<SSISSI",#workstation_name, #workstation_name, 40 + #hostname, #hostname, #hostname, 40) .. -- Supplied Domain and Workstation
    bin.pack("CC<S", -- OS version info
    5, 1, 2600) .. -- 5.1.2600
    "\x00\x00\x00\x0f" .. -- OS version info end (static 0x0000000f)
    hostname.. -- HOST NAME
    workstation_name --WORKSTATION name

    custom_options.ntlmauth = auth_blob

    -- check if the protocol is tcp
    if type(port) == 'table' then
      if port.protocol and port.protocol ~= 'tcp' then
        stdnse.debug1("NTLM authentication supports the TCP protocol only, your request to %s cannot be completed.", host)
        return http_error("Unsupported protocol.")
      end
    end

    -- tryssl uses ssl if needed. sends the type 1 message.
    local socket, partial, opts = comm.tryssl(host, port, build_request(host, port, method, path, custom_options), { timeout = options.timeout })

    if not socket then
      return http_error("Could not create socket to send type 1 message.")
    end

    repeat
      response, partial = next_response(socket, method, partial)
      if not response then
        return http_error("There was error in receivin…