1 files changed, 275 insertions, 0 deletions
diff --git a/nselib/ssh1.lua b/nselib/ssh1.lua
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+++ b/nselib/ssh1.lua
@@ -0,0 +1,275 @@
+---
+-- Functions for the SSH-1 protocol. This module also contains functions for
+-- formatting key fingerprints.
+--
+-- @author Sven Klemm <sven@c3d2.de>
+-- @copyright Same as Nmap--See https://nmap.org/book/man-legal.html
+
+
+local io = require "io"
+local math = require "math"
+local nmap = require "nmap"
+local os = require "os"
+local stdnse = require "stdnse"
+local string = require "string"
+local stringaux = require "stringaux"
+local table = require "table"
+local base64 = require "base64"
+local openssl = stdnse.silent_require "openssl"
+_ENV = stdnse.module("ssh1", stdnse.seeall)
+
+--- Retrieve the size of the packet that is being received
+--  and checks if it is fully received
+--
+--  This function is very similar to the function generated
+--  with match.numbytes(num) function, except that this one
+--  will check for the number of bytes on-the-fly, based on
+--  the written on the SSH packet.
+--
+--  @param buffer The receive buffer
+--  @return packet_length, packet_length or nil
+--  the return is similar to the lua function string:find()
+check_packet_length = function( buffer )
+  if #buffer < 4 then return nil end
+  local payload_length = string.unpack( ">I4", buffer )
+  local padding = 8 - payload_length % 8
+  assert(payload_length)
+  local total = 4+payload_length+padding;
+  if total > #buffer then return nil end
+  return total, total;
+end
+
+--- Receives a complete SSH packet, even if fragmented
+--
+--  This function is an abstraction layer to deal with
+--  checking the packet size to know if there is any more
+--  data to receive.
+--
+--  @param socket The socket used to receive the data
+--  @return status True or false
+--  @return packet The packet received
+receive_ssh_packet = function( socket )
+  local status, packet = socket:receive_buf(check_packet_length, true)
+  return status, packet
+end
+
+local function unpack_with_padding(len_bytes, data, offset)
+  local length, offset = string.unpack( ">I".. len_bytes, data, offset )
+  return string.unpack( ">c" .. math.ceil( length / 8 ), data, offset )
+end
+
+--- Fetch an SSH-1 host key.
+-- @param host Nmap host table.
+-- @param port Nmap port table.
+-- @return A table with the following fields: <code>exp</code>,
+-- <code>mod</code>, <code>bits</code>, <code>key_type</code>,
+-- <code>fp_input</code>, <code>full_key</code>, <code>algorithm</code>, and
+-- <code>fingerprint</code>.
+fetch_host_key = function(host, port)
+  local socket = nmap.new_socket()
+  local status, _
+
+  status = socket:connect(host, port)
+  if not status then return end
+  -- fetch banner
+  status = socket:receive_lines(1)
+  if not status then socket:close(); return end
+  -- send our banner
+  status = socket:send("SSH-1.5-Nmap-SSH1-Hostkey\r\n")
+  if not status then socket:close(); return end
+
+  local data, packet_length, padding, offset
+  status,data = receive_ssh_packet( socket )
+  socket:close()
+  if not status then return end
+
+  packet_length, offset = string.unpack( ">I4", data )
+  padding = 8 - packet_length % 8
+  offset = offset + padding
+
+  if padding + packet_length + 4 == #data then
+    -- seems to be a proper SSH1 packet
+    local msg_code,host_key_bits,exp,mod,length,fp_input
+    msg_code, offset = string.unpack( ">B", data, offset )
+    if msg_code == 2 then -- 2 => SSH_SMSG_PUBLIC_KEY
+      -- ignore cookie and server key bits
+      offset = offset + 8 + 4
+      -- skip server key exponent and modulus
+      _, offset = unpack_with_padding(2, data, offset)
+      _, offset = unpack_with_padding(2, data, offset)
+
+      host_key_bits, offset = string.unpack( ">I4", data, offset )
+      exp, offset = unpack_with_padding(2, data, offset)
+      exp = openssl.bignum_bin2bn( exp )
+      mod, offset = unpack_with_padding(2, data, offset)
+      mod = openssl.bignum_bin2bn( mod )
+
+      fp_input = mod:tobin()..exp:tobin()
+
+      return {exp=exp,mod=mod,bits=host_key_bits,key_type='rsa1',fp_input=fp_input,
+              full_key=('%d %s %s'):format(host_key_bits, exp:todec(), mod:todec()),
+              key=('%s %s'):format(exp:todec(), mod:todec()), algorithm="RSA1",
+              fingerprint=openssl.md5(fp_input), fp_sha256=openssl.digest("sha256",fp_input)}
+    end
+  end
+end
+
+--- Format a key fingerprint in hexadecimal.
+-- @param fingerprint Key fingerprint.
+-- @param algorithm Key algorithm.
+-- @param bits Key size in bits.
+fingerprint_hex = function( fingerprint, algorithm, bits )
+  fingerprint = stdnse.tohex(fingerprint,{separator=":",group=2})
+  return ("%d %s (%s)"):format( bits, fingerprint, algorithm )
+end
+
+--- Format a key fingerprint in base64.
+-- @param fingerprint Key fingerprint.
+-- @param hash The hashing algorithm used
+-- @param algorithm Key algorithm.
+-- @param bits Key size in bits.
+fingerprint_base64 = function( fingerprint, hash, algorithm, bits )
+  fingerprint = base64.enc(fingerprint)
+  return ("%d %s:%s (%s)"):format( bits, hash, fingerprint:match("[^=]+"), algorithm )
+end
+
+--- Format a key fingerprint in Bubble Babble.
+-- @param fingerprint Key fingerprint.
+-- @param algorithm Key algorithm.
+-- @param bits Key size in bits.
+fingerprint_bubblebabble = function( fingerprint, algorithm, bits )
+  local vowels = {'a','e','i','o','u','y'}
+  local consonants = {'b','c','d','f','g','h','k','l','m','n','p','r','s','t','v','z','x'}
+  local s = "x"
+  local seed = 1
+
+  for i=1,#fingerprint+2,2 do
+    local in1,in2,idx1,idx2,idx3,idx4,idx5
+    if i < #fingerprint or #fingerprint / 2 % 2 ~= 0 then
+      in1 = fingerprint:byte(i)
+      idx1 = (((in1 >> 6) & 3) + seed) % 6 + 1
+      idx2 = ((in1 >> 2) & 15) + 1
+      idx3 = ((in1 & 3) + math.floor(seed/6)) % 6 + 1
+      s = s .. vowels[idx1] .. consonants[idx2] .. vowels[idx3]
+      if i < #fingerprint then
+        in2 = fingerprint:byte(i+1)
+        idx4 = ((in2 >> 4) & 15) + 1
+        idx5 = (in2 & 15) + 1
+        s = s .. consonants[idx4] .. '-' .. consonants[idx5]
+        seed = (seed * 5 + in1 * 7 + in2) % 36
+      end
+    else
+      idx1 = seed % 6 + 1
+      idx2 = 16 + 1
+      idx3 = math.floor(seed/6) + 1
+      s = s .. vowels[idx1] .. consonants[idx2] .. vowels[idx3]
+    end
+  end
+  s = s .. 'x'
+  return ("%d %s (%s)"):format( bits, s, algorithm )
+end
+
+--- Format a key fingerprint into a visual ASCII art representation.
+--
+-- Ported from http://www.openbsd.org/cgi-bin/cvsweb/~checkout~/src/usr.bin/ssh/key.c.
+-- @param fingerprint Key fingerprint.
+-- @param algorithm Key algorithm.
+-- @param bits Key size in bits.
+fingerprint_visual = function( fingerprint, algorithm, bits )
+  local i,j,field,characters,input,fieldsize_x,fieldsize_y,s
+  fieldsize_x, fieldsize_y = 17, 9
+  characters = {' ','.','o','+','=','*','B','O','X','@','%','&','#','/','^','S','E'}
+
+  -- initialize drawing area
+  field = {}
+  for i=1,fieldsize_x do
+    field[i]={}
+    for j=1,fieldsize_y do field[i][j]=1 end
+  end
+
+  -- we start in the center and mark it
+  local x, y = math.ceil(fieldsize_x/2), math.ceil(fieldsize_y/2)
+  field[x][y] = #characters - 1;
+
+  -- iterate over fingerprint
+  for i=1,#fingerprint do
+    input = fingerprint:byte(i)
+    -- each byte conveys four 2-bit move commands
+    for j=1,4 do
+      if (input & 1) == 1 then x = x + 1 else x = x - 1 end
+      if (input & 2) == 2 then y = y + 1 else y = y - 1 end
+
+      x = math.max(x,1); x = math.min(x,fieldsize_x)
+      y = math.max(y,1); y = math.min(y,fieldsize_y)
+
+      if field[x][y] < #characters - 2 then
+        field[x][y] = field[x][y] + 1
+      end
+      input = input >> 2
+    end
+  end
+
+  -- mark end point
+  field[x][y] = #characters;
+
+  -- build output
+  s = ('\n+--[%4s %4d]----+\n'):format( algorithm, bits )
+  for i=1,fieldsize_y do
+    s = s .. '|'
+    for j=1,fieldsize_x do s = s .. characters[ field[j][i] ] end
+    s = s .. '|\n'
+  end
+  s = s .. '+-----------------+\n'
+  return s
+end
+
+-- A lazy parsing function for known_hosts_file.
+-- The script checks for the known_hosts file in this order:
+--
+-- (1) If known_hosts is specified in a script arg, use that. If turned
+-- off (false), then don't do any known_hosts checking.
+-- (2) Look at ~/.ssh/config to see if user known_hosts is in an
+-- alternate location*. Look for "UserKnownHostsFile". If
+-- UserKnownHostsFile is specified, open that known_hosts.
+-- (3) Otherwise, open ~/.ssh/known_hosts.
+parse_known_hosts_file = function(path)
+    local common_paths = {}
+    local f, knownhostspath
+
+    if path and io.open(path) then
+        knownhostspath = path
+    end
+
+    if not knownhostspath then
+        for l in io.lines(os.getenv("HOME") .. "/.ssh/config") do
+            if l and string.find(l, "UserKnownHostsFile") then
+                knownhostspath = string.match(l, "UserKnownHostsFile%s(.*)")
+                if string.sub(knownhostspath,1,1)=="~" then
+                    knownhostspath = os.getenv("HOME") .. string.sub(knownhostspath, 2)
+                end
+            end
+        end
+    end
+
+    if not knownhostspath then
+        knownhostspath = os.getenv("HOME") .."/.ssh/known_hosts"
+    end
+
+    if not knownhostspath then
+        return
+    end
+
+    local known_host_entries = {}
+    local lnumber = 0
+
+    for l in io.lines(knownhostspath) do
+        lnumber = lnumber + 1
+        if l and string.sub(l, 1, 1) ~= "#" then
+            local parts = stringaux.strsplit(" ", l)
+            table.insert(known_host_entries, {entry=parts, linenumber=lnumber})
+        end
+    end
+    return known_host_entries
+end
+
+return _ENV;