Add extended-ASCII support to LM hashing

Probably only works for US-English, since it uses Code Page 437. Adding
support for other locales would require detecting or setting the locale
for the remote system, since SMB has no way to negotiate code page. In
other words, Windows systems with different locales will have different
LM hashes for the same password.

Also added some tests. Hashes confirmed by googling for them and finding
the correct plaintext.

nselib/smbauth.lua

@@ -86,6 +86,7 @@ local stdnse = require "stdnse"
 local string = require "string"
 local table = require "table"
 local unicode = require "unicode"
+local unittest = require "unittest"
 _ENV = stdnse.module("smbauth", stdnse.seeall)
 
 local have_ssl, openssl = pcall(require, "openssl")
@@ -345,6 +346,25 @@ local function lm_create_hash(password)
   -- Convert the password to uppercase
   password = string.upper(password)
 
+  -- Encode the password in OEM code page
+  -- Supporting all the OEM code pages would be burdensome, so we try to
+  -- convert to CP437, the default for US-English Windows, which is
+  -- used for Alt+NumPad "unicode" entry in all versions of Windows.
+  -- https://en.wikipedia.org/wiki/Code_page_437
+  do
+    local buf = {}
+    for i, cp in ipairs(unicode.decode(password, unicode.utf8_dec)) do
+      local ch = unicode.cp437_enc(cp)
+      if ch == nil then
+        return false, "Couldn't encode password in CP437"
+      end
+      buf[i] = ch
+    end
+    password = table.concat(buf)
+    local nsedebug = require 'nsedebug'
+    stdnse.print_debug("LM Password: %s", stdnse.tohex(password))
+  end
+
   -- If password is under 14 characters, pad it to 14
   if(#password < 14) then
     password = password .. string.rep(string.char(0), 14 - #password)
@@ -900,5 +920,30 @@ function calculate_signature(mac_key, data)
   end
 end
 
+test_suite = unittest.TestSuite:new()
+test_suite:add_test(unittest.equal(
+    stdnse.tohex(select(-1, lm_create_hash("passphrase"))),
+    "855c3697d9979e78ac404c4ba2c66533"
+    ),
+  "lm_create_hash"
+  )
+test_suite:add_test(unittest.equal(
+    stdnse.tohex(select(-1, ntlm_create_hash("passphrase"))),
+    "7f8fe03093cc84b267b109625f6bbf4b"
+    ),
+  "ntlm_create_hash"
+  )
+test_suite:add_test(unittest.equal(
+    stdnse.tohex(select(-1, lm_create_hash("ÅÇÅÇ"))),
+    "1830f5732b438091aad3b435b51404ee"
+    ),
+  "lm_create_hash"
+  )
+test_suite:add_test(unittest.equal(
+    stdnse.tohex(select(-1, ntlm_create_hash("öäü"))),
+    "4848bcb81cf018c3b70ea1479bd1374d"
+    ),
+  "ntlm_create_hash"
+  )
 
 return _ENV;