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description = [[
Attempts to guess username/password combinations over SMB, storing discovered combinations
for use in other scripts. Every attempt will be made to get a valid list of users and to
verify each username before actually using them. When a username is discovered, besides
being printed, it is also saved in the Nmap registry so other Nmap scripts can use it. That
means that if you're going to run <code>smb-brute.nse</code>, you should run other <code>smb</code> scripts you want.
This checks passwords in a case-insensitive way, determining case after a password is found,
for Windows versions before Vista.
This script is specifically targeted towards security auditors or penetration testers.
One example of its use, suggested by Brandon Enright, was hooking up <code>smb-brute.nse</code> to the
database of usernames and passwords used by the Conficker worm (the password list can be
found at http://www.skullsecurity.org/wiki/index.php/Passwords, among other places.
Then, the network is scanned and all systems that would be infected by Conficker are
discovered.
From the penetration tester perspective its use is pretty obvious. By discovering weak passwords
on SMB, a protocol that's well suited for bruteforcing, access to a system can be gained.
Further, passwords discovered against Windows with SMB might also be used on Linux or MySQL
or custom Web applications. Discovering a password greatly beneficial for a pen-tester.
This script uses a lot of little tricks that I (Ron Bowes) describe in detail in a blog
posting, http://www.skullsecurity.org/blog/?p=164. The tricks will be summarized here, but
that blog is the best place to learn more.
Usernames and passwords are initially taken from the unpwdb library. If possible, the usernames
are verified as existing by taking advantage of Windows' odd behaviour with invalid username
and invalid password responses. As soon as it is able, this script will download a full list
of usernames from the server and replace the unpw usernames with those. This enables the
script to restrict itself to actual accounts only.
When an account is discovered, it's saved in the <code>smb</code> module (which uses the Nmap
registry). If an account is already saved, the account's privileges are checked; accounts
with administrator privileges are kept over accounts without. The specific method for checking
is by calling <code>GetShareInfo("IPC$")</code>, which requires administrative privileges. Once this script
is finished (all other smb scripts depend on it, it'll run first), other scripts will use the saved account
to perform their checks.
The blank password is always tried first, followed by "special passwords" (such as the username
and the username reversed). Once those are exhausted, the unpwdb password list is used.
One major goal of this script is to avoid accout lockouts. This is done in a few ways. First,
when a lockout is detected, unless you user specifically overrides it with the <code>smblockout</code>
argument, the scan stops. Second, all usernames are checked with the most common passwords first,
so with not-too-strict lockouts (10 invalid attempts), the 10 most common passwords will still
be tried. Third, one account, called the canary, "goes out ahead"; that is, three invalid
attempts are made (by default) to ensure that it's locked out before others are.
In addition to active accounts, this script will identify valid passwords for accounts that
are disabled, guest-equivalent, and require password changes. Although these accounts can't
be used, it's good to know that the password is valid. In other cases, it's impossible to
tell a valid password (if an account is locked out, for example). These are displayed, too.
Certain accounts, such as guest or some guest-equivalent, will permit any password. This
is also detected. When possible, the SMB protocol is used to its fullest to get maximum
information.
When possible, checks are done using a case-insensitive password, then proper case is
determined with a fairly efficient bruteforce. For example, if the actual password is
"PassWord", then "password" will work and "PassWord" will be found afterwards (on the
14th attempt out of a possible 256 attempts, with the current algorithm).
]]
---
--@usage
-- nmap --script smb-brute.nse -p445 <host>
-- sudo nmap -sU -sS --script smb-brute.nse -p U:137,T:139 <host>
--
--@output
-- Host script results:
-- | smb-brute:
-- | | bad name:test => Login was successful
-- | | consoletest:test => Password was correct, but user can't log in without changing it
-- | | guest:<anything> => Password was correct, but user's account is disabled
-- | | mixcase:BuTTeRfLY1 => Login was successful
-- | | test:password1 => Login was successful
-- | | this:password => Login was successful
-- | | thisisaverylong:password => Login was successful
-- | | thisisaverylongname:password => Login was successful
-- | | thisisaverylongnamev:password => Login was successful
-- |_ |_ web:TeSt => Password was correct, but user's account is disabled
--
-- @args smblockout Unless this is set to <code>1</code> or <code>true</code>, the script won't continue if it
-- locks out an account or thinks it will lock out an account.
-- @args brutelimit Limits the number of usernames checked in the script. In some domains,
-- it's possible to end up with 10,000+ usernames on each server. By default, this
-- will be <code>5000</code>, which should be higher than most servers and also prevent infinite
-- loops or other weird things. This will only affect the user list pulled from the
-- server, not the username list.
-- @args canaries Sets the number of tests to do to attempt to lock out the first account.
-- This will lock out the first account without locking out the rest of the accounts.
-- The default is 3, which will only trigger strict lockouts, but will also bump the
-- canary account up far enough to detect a lockout well before other accounts are
-- hit.
-----------------------------------------------------------------------
author = "Ron Bowes"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"intrusive", "auth"}
require 'msrpc'
require 'smb'
require 'stdnse'
require 'unpwdb'
---The maximum number of usernames to check (can be modified with smblimit argument)
-- The limit exists because domains may have hundreds of thousands of accounts,
-- potentially.
local LIMIT = 5000
hostrule = function(host)
return smb.get_port(host) ~= nil
end
---The possible result codes. These are simplified from the actual codes that SMB returns.
local results =
{
SUCCESS = 1, -- Login was successful
GUEST_ACCESS = 2, -- Login was successful, but was granted guest access
NOT_GRANTED = 3, -- Password was correct, but user wasn't allowed to log in (often happens with blank passwords)
DISABLED = 4, -- Password was correct, but user's account is disabled
EXPIRED = 5, -- Password was correct, but user's account is expired
CHANGE_PASSWORD = 6, -- Password was correct, but user can't log in without changing it
ACCOUNT_LOCKED = 7, -- User's account is locked out (hopefully not by us!)
ACCOUNT_LOCKED_NOW = 8, -- User's account just became locked out (oops!)
FAIL = 9 -- User's password was incorrect
}
---Strings for debugging output
local result_short_strings = {}
result_short_strings[results.SUCCESS] = "SUCCESS"
result_short_strings[results.GUEST_ACCESS] = "GUEST_ACCESS"
result_short_strings[results.NOT_GRANTED] = "NOT_GRANTED"
result_short_strings[results.DISABLED] = "DISABLED"
result_short_strings[results.EXPIRED] = "EXPIRED"
result_short_strings[results.CHANGE_PASSWORD] = "CHANGE_PASSWORD"
result_short_strings[results.ACCOUNT_LOCKED] = "LOCKED"
result_short_strings[results.ACCOUNT_LOCKED_NOW] = "LOCKED_NOW"
result_short_strings[results.FAIL] = "FAIL"
---The strings that the user will see
local result_strings = {}
result_strings[results.SUCCESS] = "Login was successful"
result_strings[results.GUEST_ACCESS] = "Login was successful, but was granted guest access"
result_strings[results.NOT_GRANTED] = "Password was correct, but user wasn't allowed to log in (often happens with blank passwords)"
result_strings[results.DISABLED] = "Password was correct, but user's account is disabled"
result_strings[results.EXPIRED] = "Password was correct, but user's account is expired"
result_strings[results.CHANGE_PASSWORD] = "Password was correct, but user can't log in without changing it"
result_strings[results.ACCOUNT_LOCKED] = "User's account is locked out (hopefully not by us!)"
result_strings[results.ACCOUNT_LOCKED_NOW] = "User's account just became locked out (oops!)"
result_strings[results.FAIL] = "User's password was incorrect"
---Constants for special passwords. These each contain a null character, which is illegal in
-- actual passwords.
local USERNAME = string.char(0) .. "username"
local USERNAME_REVERSED = string.char(0) .. "username reversed"
local special_passwords = { USERNAME, USERNAME_REVERSED }
---Generates a random string of the requested length. This can be used to check how hosts react to
-- weird username/password combinations.
--@param length (optional) The length of the string to return. Default: 8.
--@param set (optional) The set of letters to choose from. Default: upper, lower, numbers, and underscore.
--@return The random string.
local function get_random_string(length, set)
if(length == nil) then
length = 8
end
if(set == nil) then
set = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_"
end
local str = ""
-- Seed the random number, if we haven't already
if not nmap.registry.smbbrute or not nmap.registry.smbbrute.seeded then
math.randomseed(os.time())
nmap.registry.smbbrute = {}
nmap.registry.smbbrute.seeded = true
end
for i = 1, length, 1 do
local random = math.random(#set)
str = str .. string.sub(set, random, random)
end
return str
end
---Splits a string in the form "domain\user" into domain and user.
--@param str The string to split
--@return (domain, username) The domain and the username. If no domain was given, nil is returned
-- for domain.
local function split_domain(str)
local username, domain
local split = stdnse.strsplit("\\", str)
if(#split > 1) then
domain = split[1]
username = split[2]
else
domain = nil
username = str
end
return domain, username
end
---Formats a username/password pair with an optional result. Just a way to keep things consistent
-- throughout the program. Currently, the format is "username:password => result".
--@param username The username.
--@param password [optional] The password. Default: "<unknown>".
--@param result [optional] The result, as a constant. Default: not used.
--@return A string representing the input values.
local function format_result(username, password, result)
if(username == "") then
username = "<blank>"
end
if(password == nil) then
password = "<unknown>"
elseif(password == "") then
password = "<blank>"
end
if(result == nil) then
return string.format("%s:%s", username, password)
else
return string.format("%s:%s => %s", username, password, result_strings[result])
end
end
---Decides which login type to use (lanman, ntlm, or other). Designed to keep things consistent.
--@param hostinfo The hostinfo table.
--@return A string representing the login type to use (that can be passed to SMB functions).
local function get_type(hostinfo)
-- Check if the user requested a specific type
if(nmap.registry.args.smbtype ~= nil) then
return nmap.registry.args.smbtype
end
-- Otherwise, base the type on the operating system (TODO: other versions of Windows (7, 2008))
-- 2k8 example: "Windows Server (R) 2008 Datacenter without Hyper-V 6001 Service Pack 1"
if(string.find(string.lower(hostinfo['os']), "vista") ~= nil) then
return "ntlm"
elseif(string.find(string.lower(hostinfo['os']), "2008") ~= nil) then
return "ntlm"
elseif(string.find(string.lower(hostinfo['os']), "Windows 7") ~= nil) then
return "ntlm"
end
return "lm"
end
---Stops the session, if one exists. This can be called as frequently as needed, it'll just return if no
-- session is present, but it should generally be paired with a <code>restart_session</code> call.
--@param hostinfo The hostinfo table.
--@return (status, err) If status is false, err is a string corresponding to the error; otherwise, err is undefined.
local function stop_session(hostinfo)
local status, err
if(hostinfo['smbstate'] ~= nil) then
stdnse.print_debug(2, "smb-brute: Stopping the SMB session")
status, err = smb.stop(hostinfo['smbstate'])
if(status == false) then
return false, err
end
hostinfo['smbstate'] = nil
end
return true
end
---Starts or restarts a SMB session with the host. Although this will automatically stop a session if
-- one exists, it's a little cleaner to pair this with a <code>stop_session</code> call.
--@param hostinfo The hostinfo table.
--@return (status, err) If status is false, err is a string corresponding to the error; otherwise, err is undefined.
local function restart_session(hostinfo)
local status, err, smbstate
-- Stop the old session, if it exists
stop_session(hostinfo)
stdnse.print_debug(2, "smb-brute: Starting the SMB session")
status, smbstate = smb.start_ex(hostinfo['host'], true, nil, nil, nil, true)
if(status == false) then
return false, smbstate
end
hostinfo['smbstate'] = smbstate
return true
end
---Attempts to log into an account, returning one of the <code>results</code> constants. Will always return to the
-- state where another login can be attempted. Will also differentiate between a hash and a password, and choose the
-- proper login method (unless overridden). Will interpret the result as much as possible.
--
-- The session has to be active (ie, <code>restart_session</code> has to be called) before calling this function.
--
--@param hostinfo The hostinfo table.
--@param username The username to try.
--@param password The password to try.
--@param logintype [optional] The logintype to use. Default: <code>get_type</code> is called. If <code>password</code>
-- is a hash, this is ignored.
--@return Result, an integer value from the <code>results</code> constants.
local function check_login(hostinfo, username, password, logintype)
local result
local domain = ""
local smbstate = hostinfo['smbstate']
if(logintype == nil) then
logintype = get_type(hostinfo)
end
-- Determine if we have a password hash or a password
if(#password == 32 or #password == 64 or #password == 65) then
-- It's a hash (note: we always use NTLM hashes)
status, err = smb.start_session(smbstate, smb.get_overrides(username, domain, nil, password, "ntlm"), false)
else
status, err = smb.start_session(smbstate, smb.get_overrides(username, domain, password, nil, logintype), false)
end
if(status == true) then
if(smbstate['is_guest'] == 1) then
result = results.GUEST_ACCESS
else
result = results.SUCCESS
end
smb.logoff(smbstate)
else
if(err == "NT_STATUS_LOGON_TYPE_NOT_GRANTED") then
result = results.NOT_GRANTED
elseif(err == "NT_STATUS_ACCOUNT_LOCKED_OUT") then
result = results.ACCOUNT_LOCKED
elseif(err == "NT_STATUS_ACCOUNT_DISABLED") then
result = results.DISABLED
elseif(err == "NT_STATUS_PASSWORD_MUST_CHANGE") then
result = results.CHANGE_PASSWORD
else
result = results.FAIL
end
end
--io.write(string.format("Result: %s\n\n", result_strings[result]))
return result
end
---Determines whether or not a login was successful, based on what's known about the server's settings. This
-- is fairly straight forward, but has a couple little tricks.
--
--@param hostinfo The hostinfo table.
--@param result The result code.
--@return <code>true</code> if the password used for logging in was correct, <code>false</code> otherwise. Keep
-- in mind that this doesn't imply the login was successful (only results.SUCCESS indicates that), rather
-- that the password was valid.
function is_positive_result(hostinfo, result)
-- If result is a FAIL, it's always bad
if(result == results.FAIL) then
return false
end
-- If result matches what we discovered for invalid passwords, it's always bad
if(result == hostinfo['invalid_password']) then
return false
end
-- If result was ACCOUNT_LOCKED, it's always bad (locked accounts should already be taken care of, but this
-- makes the function a bit more generic)
if(result == results.ACCOUNT_LOCKED) then
return false
end
-- Otherwise, it's good
return true
end
---Determines whether or not a login was "bad". A bad login is one where an account becomes locked out.
--
--@param hostinfo The hostinfo table.
--@param result The result code.
--@return <code>true</code> if the password used for logging in was correct, <code>false</code> otherwise. Keep
-- in mind that this doesn't imply the login was successful (only results.SUCCESS indicates that), rather
-- that the password was valid.
function is_bad_result(hostinfo, result)
-- If result is LOCKED, it's always bad.
if(result == results.ACCOUNT_LOCKED or result == results.ACCOUNT_LOCKED_NOW) then
return true
end
-- Otherwise, it's good
return false
end
---Count the number of one bits in a binary representation of the given number. This is used for case-sensitive
-- checks.
--
--@param num The number to count the ones for.
--@return The number of ones in the number
local function count_ones(num)
local count = 0
while num ~= 0 do
if(bit.band(num, 1) == 1) then
count = count + 1
end
num = bit.rshift(num, 1)
end
return count
end
---Converts a string's case based on a binary number. For every '1' bit, the character is uppercased, and for every '0'
-- bit it's lowercased. For example, "test" and 8 (1000) becomes "Test", while "test" and 11 (1011) becomes "TeST".
--
--@param str The string to convert.
--@param num The binary number representing the case. This value isn't checked, so if it's too large it's truncated, and if it's
-- too small it's effectively zero-padded.
--@return The converted string.
local function convert_case(str, num)
local pos = #str
-- Don't bother with blank strings (we probably won't get here anyway, but it doesn't hurt)
if(str == "") then
return ""
end
while(num ~= 0) do
-- Check if the bit we're at is '1'
if(bit.band(num, 1) == 1) then
-- Check if we're at the beginning or end (or both) of the string -- those are special cases
if(pos == #str and pos == 1) then
str = string.upper(string.sub(str, pos, pos))
elseif(pos == #str) then
str = string.sub(str, 1, pos - 1) .. string.upper(string.sub(str, pos, pos))
elseif(pos == 1) then
str = string.upper(string.sub(str, pos, pos)) .. string.sub(str, pos + 1, #str)
else
str = string.sub(str, 1, pos - 1) .. string.upper(string.sub(str, pos, pos)) .. string.sub(str, pos + 1, #str)
end
end
num = bit.rshift(num, 1)
pos = pos - 1
end
return str
end
---Attempts to determine the case of a password. This is done by trying every possible combination of upper and lowercase
-- characters in the password, in the most efficient possible ordering, until the corerct case is found.
--
-- A session has to be active when this function is called.
--
--@param hostinfo The hostinfo table.
--@param username The username.
--@param password The password (it's assumed that it's all lowercase already, but it doesn't matter)
--@return The password with the proper case, or the original password if it couldn't be determined (either the proper
-- case wasn't found or the login type is incorrect).
local function find_password_case(hostinfo, username, password)
-- Only do this if we're using lanman, otherwise we already have the proper password
if(get_type(hostinfo) ~= "lm") then
return password
end
-- Figure out how many possibilities exist
local max = math.pow(2, #password) - 1
-- Create an array of them, starting with all the values whose binary representation has no ones, then one one, then two ones, etc.
local ordered = {}
-- Cheat a bit, by adding all lower then all upper right at the start
ordered = {0, max}
-- Loop backwards from the length of the password to 0. At each spot, put all numbers that have that many '1' bits
for i = 1, #password - 1, 1 do
for j = max, 0, -1 do
if(count_ones(j) == i) then
table.insert(ordered, j)
end
end
end
-- Create the list of converted passwords
for i = 1, #ordered, 1 do
local thispassword = convert_case(password, ordered[i])
-- We specify "ntlm" for the login type because it's case sensitive
local result = check_login(hostinfo, username, thispassword, 'ntlm')
if(is_positive_result(hostinfo, result)) then
return thispassword
end
end
-- Print an error message
stdnse.print_debug(1, "ERROR: smb-brute: Was unable to determine case of %s's password", username)
-- If all else fails, just return the actual password (we probably shouldn't get here)
return password
end
---Unless the user is ok with lockouts, check the lockout policy of the host. Take the most restrictive
-- portion among the domains. Returns true if lockouts could happen, false otherwise.
local function bad_lockout_policy(host)
-- If the user is ok with locking out accounts, just return
if(nmap.registry.args.smblockout == "1" or nmap.registry.args.smblockout == "true") then
stdnse.print_debug(1, "smb-brute: Not checking server's lockout policy")
return true, false
end
local status, result = msrpc.get_domains(host)
if(not(status)) then
stdnse.print_debug(1, "smb-brute: Couldn't detect lockout policy: %s\n", result)
return false, "Couldn't retrieve lockout policy: " .. result
end
for domain, data in pairs(result) do
if(data and data.lockout_threshold) then
stdnse.print_debug(1, "smb-brute: Server's lockout policy: lock out after %d attempts\n", data.lockout_threshold)
return true, true
end
end
stdnse.print_debug(1, "smb-brute: Server has no lockout policy")
return true, false
end
---Initializes and returns the hostinfo table. This includes queuing up the username and password lists, determining
-- the server's operating system, and checking the server's response for invalid usernames/invalid passwords.
--
--@param host The host object.
local function initialize(host)
local os, result
local status, bad_lockout_policy_result
local hostinfo = {}
hostinfo['host'] = host
hostinfo['invalid_usernames'] = {}
hostinfo['locked_usernames'] = {}
hostinfo['accounts'] = {}
hostinfo['special_password'] = 1
-- Get the OS (identifying windows versions tells us which hash to use)
result, os = smb.get_os(host)
if(result == false) then
hostinfo['os'] = "<Unknown>"
else
hostinfo['os'] = os['os']
end
stdnse.print_debug(1, "smb-brute: Remote operating system: %s", hostinfo['os'])
-- Check lockout policy
status, bad_lockout_policy_result = bad_lockout_policy(host)
if(not(status)) then
stdnse.print_debug(1, "smb-brute: WARNING: couldn't determine lockout policy: %s", bad_lockout_policy_result)
else
if(bad_lockout_policy_result) then
return false, "Account lockouts are enabled on the host. To continue (and risk lockouts), add --script-args=smblockout=1 -- for more information, run smb-enum-domains."
end
end
-- Attempt to enumerate users
stdnse.print_debug(1, "smb-brute: Trying to get user list from server")
hostinfo['have_user_list'], _, hostinfo['user_list'] = msrpc.get_user_list(host)
hostinfo['user_list_index'] = 1
if(hostinfo['have_user_list'] and #hostinfo['user_list'] == 0) then
hostinfo['have_user_list'] = false
end
-- If the enumeration failed, try using the built-in list
if(not(hostinfo['have_user_list'])) then
stdnse.print_debug(1, "smb-brute: Couldn't enumerate users (normal for Windows XP and higher), using unpwdb initially")
status, hostinfo['user_list_default'] = unpwdb.usernames()
if(status == false) then
return false, "Couldn't open username file"
end
end
-- Open the password file
stdnse.print_debug(1, "smb-brute: Opening password list")
status, hostinfo['password_list'] = unpwdb.passwords()
if(status == false) then
return false, "Couldn't open password file"
end
-- Start the SMB session
stdnse.print_debug(1, "smb-brute: Starting the initial SMB session")
status, err = restart_session(hostinfo)
if(status == false) then
stop_session(hostinfo)
return false, err
end
-- Some hosts will accept any username -- check for this by trying to log in with a totally random name. If the
-- server accepts it, it'll be impossible to bruteforce; if it gives us a weird result code, we have to remember
-- it.
hostinfo['invalid_username'] = check_login(hostinfo, get_random_string(8), get_random_string(8), "ntlm")
hostinfo['invalid_password'] = check_login(hostinfo, "Administrator", get_random_string(8), "ntlm")
stdnse.print_debug(1, "smb-brute: Server's response to invalid usernames: %s", result_short_strings[hostinfo['invalid_username']])
stdnse.print_debug(1, "smb-brute: Server's response to invalid passwords: %s", result_short_strings[hostinfo['invalid_password']])
-- If either of these comes back as success, there's no way to tell what's valid/invalid
if(hostinfo['invalid_username'] == results.SUCCESS) then
stop_session(hostinfo)
return false, "Invalid username was accepted; unable to bruteforce"
end
if(hostinfo['invalid_password'] == results.SUCCESS) then
stop_session(hostinfo)
return false, "Invalid password was accepted; unable to bruteforce"
end
-- Print a message to the user if we can identify passwords
if(hostinfo['invalid_username'] ~= hostinfo['invalid_password']) then
stdnse.print_debug(1, "smb-brute: Invalid username and password response are different, so identifying valid accounts is possible")
end
-- Print a warning message if invalid_username and invalid_password go to the same thing that isn't FAIL
if(hostinfo['invalid_username'] ~= results.FAIL and hostinfo['invalid_username'] == hostinfo['invalid_password']) then
stdnse.print_debug(1, "smb-brute: WARNING: Difficult to recognize invalid usernames/passwords; may not get good results")
end
-- Restart the SMB connection so we have a clean slate
stdnse.print_debug(1, "smb-brute: Restarting the session before the bruteforce")
status, err = restart_session(hostinfo)
if(status == false) then
stop_session(hostinfo)
return false, err
end
-- Stop the SMB session (we're going to let the scripts look after their own sessions)
stop_session(hostinfo)
-- Return the results
return true, hostinfo
end
---Retrieves the next password in the password database we're using. Will never return the empty string.
-- May also return one of the <code>special_passwords</code> constants.
--
--@param hostinfo The hostinfo table (the password list is stored there).
--@return The new password, or nil if the end of the list has been reached.
local function get_next_password(hostinfo)
local new_password
-- If we're out of special passwords, move onto actual ones
if(hostinfo['special_password'] > #special_passwords) then
-- Pick the next non-blank password from the list
repeat
new_password = hostinfo['password_list']()
until new_password ~= ''
else
-- Get the next non-blank password
new_password = special_passwords[hostinfo['special_password']]
hostinfo['special_password'] = hostinfo['special_password'] + 1
end
return new_password
end
---Reset to the first password. This is normally done when the user list changes.
--
--@param hostinfo The hostinfo table.
local function reset_password(hostinfo)
hostinfo['password_list']("reset")
end
---Retrieves the next username. This can be from the username database, or from an array stored in the
-- hostinfo table. This won't return any names that have been determined to be invalid, locked, or
-- have already had their password found.
--
--@param hostinfo The hostinfo table
--@return The next username, or nil if the end of the list has been reached.
local function get_next_username(hostinfo)
local username
repeat
if(hostinfo['have_user_list']) then
local index = hostinfo['user_list_index']
hostinfo['user_list_index'] = hostinfo['user_list_index'] + 1
username = hostinfo['user_list'][index]
if(username ~= nil) then
_, username = split_domain(username)
end
else
username = hostinfo['user_list_default']()
end
-- Make the username lowercase (usernames aren't case sensitive, so making it lower case prevents duplicates)
if(username ~= nil) then
username = string.lower(username)
end
until username == nil or (hostinfo['invalid_usernames'][username] ~= true and hostinfo['locked_usernames'][username] ~= true and hostinfo['accounts'][username] == nil)
return username
end
---Reset to the first username.
--
--@param hostinfo The hostinfo table.
local function reset_username(hostinfo)
if(hostinfo['have_user_list']) then
hostinfo['user_list_index'] = 1
else
hostinfo['user_list_default']("reset")
end
end
---Do a little trick to detect account lockouts without bringing every user to the lockout threshold -- bump the lockout counter of
-- the first user ahead. If lockouts are happening, this means that the first account will trigger before the rest of the accounts.
-- A canary in the mineshaft, in a way.
--
-- The number of checks defaults to three, but it can be controlled with the <code>canary</code> argument.
--
-- Times it'll fail are when:
-- * Accounts are locked out due to the initial checks (happens if the user runs smb-brute twice in a row, the canary won't help)
-- * A valid user list isn't pulled, and we create a canary that doesn't exist (won't be as bad, though, because it means we also
-- don't have every account on the server/domain
function test_lockouts(hostinfo)
local i
local username = get_next_username(hostinfo)
-- It's possible that every username was accounted for already, so our list is empty.
if(username == nil) then
return
end
if(nmap.registry.args.smblockout == 1 or nmap.registry.args.smblockout == "true") then
return
end
while(string.lower(username) == "administrator") do
username = get_next_username(hostinfo)
if(username == nil) then
return
end
end
if(username ~= nil) then
-- Try logging in as the "canary" account
local canaries = nmap.registry.args.canaries
if(canaries == nil) then
canaries = 3
else
canaries = tonumber(canaries)
end
if(canaries > 0) then
stdnse.print_debug(1, "smb-brute: Detecting server lockout on '%s' with %d canaries", username, canaries)
end
for i=1, canaries, 1 do
result = check_login(hostinfo, username, get_random_string(8), "ntlm")
end
-- If the account just became locked (it's already been put on the 'valid' list), we're in trouble
if(result == results.LOCKED) then
-- If the canary just became locked, we're one step from locking out every account. Loop through the usernames and invalidate them to
-- prevent them from being locked out
stdnse.print_debug(1, "smb-brute: Canary (%s) became locked out -- aborting")
-- Add it to the locked username list (so it can be reported)
hostinfo['locked_usernames'][username] = true
-- Mark all the usernames as invalid (a bit of a hack, but it's safer this way)
while(username ~= nil) do
stdnse.print_debug(1, "smb-brute: Marking '%s' as 'invalid'", username)
hostinfo['invalid_usernames'][username] = true
username = get_next_username(hostinfo)
end
end
end
-- Go back to the beginning of the list
reset_username(hostinfo)
end
---Attempts to validate the current list of usernames by logging in with a blank password, marking invalid ones (and ones that had
-- a blank password). Determining the validity of a username works best if invalid usernames are redirected to 'guest'.
--
-- If a username accepts the blank password, a random password is tested. If that's accepted as well, the account is marked as
-- accepting any password (the 'guest' account is normally like that).
--
-- This also checks whether the server locks out users, and raises the lockout threshold of the first user (see the
-- <code>check_lockouts</code> function for more information on that. If accounts on the system are locked out, they aren't
-- checked.
--
--@param hostinfo The hostinfo table.
--@return (status, err) If status is false, err is a string corresponding to the error; otherwise, err is undefined.
local function validate_usernames(hostinfo)
local status, err
local result
local username, password
stdnse.print_debug(1, "smb-brute: Checking which account names exist (based on what goes to the 'guest' account)")
-- Start a session
status, err = restart_session(hostinfo)
if(status == false) then
return false, err
end
-- Make sure we start at the beginning
reset_username(hostinfo)
username = get_next_username(hostinfo)
while(username ~= nil) do
result = check_login(hostinfo, username, "", "ntlm")
if(result ~= hostinfo['invalid_password'] and result == hostinfo['invalid_username']) then
-- If the account matches the value of 'invalid_username', but not the value of 'invalid_password', it's invalid
stdnse.print_debug(1, "smb-brute: Blank password for '%s' -> '%s' (invalid account)", username, result_short_strings[result])
hostinfo['invalid_usernames'][username] = true
elseif(result == hostinfo['invalid_password']) then
-- If the account matches the value of 'invalid_password', and 'invalid_password' is reliable, it's probably valid
if(hostinfo['invalid_username'] ~= results.FAIL and hostinfo['invalid_username'] == hostinfo['invalid_password']) then
stdnse.print_debug(1, "smb-brute: Blank password for '%s' => '%s' (can't determine validity)", username, result_short_strings[result])
else
stdnse.print_debug(1, "smb-brute: Blank password for '%s' => '%s' (probably valid)", username, result_short_strings[result])
end
elseif(result == results.ACCOUNT_LOCKED) then
-- If the account is locked out, don't try it
hostinfo['locked_usernames'][username] = true
stdnse.print_debug(1, "smb-brute: Blank password for '%s' => '%s' (locked out)", username, result_short_strings[result])
elseif(result == results.FAIL) then
-- If none of the standard options work, check if it's FAIL. If it's FAIL, there's an error somewhere (probably, the
-- 'administrator' username is changed so we're getting invalid data).
stdnse.print_debug(1, "smb-brute: Blank password for '%s' => '%s' (may be valid)", username, result_short_strings[result])
else
-- If none of those came up, either the password is legitimately blank, or any account works. Figure out what!
local new_result = check_login(hostinfo, username, get_random_string(14), "ntlm")
if(new_result == result) then
-- Any password works (often happens with 'guest' account)
stdnse.print_debug(1, "smb-brute: All passwords accepted for %s (goes to %s)", username, result_short_strings[result])
status, err = found_account(hostinfo, username, "<anything>", result)
if(status == false) then
return false, err
end
else
-- Blank password worked, but not random one
status, err = found_account(hostinfo, username, "", result)
if(status == false) then
return false, err
end
end
end
username = get_next_username(hostinfo)
end
-- Start back at the beginning of the list
reset_username(hostinfo)
-- Check for lockouts
test_lockouts(hostinfo)
-- Stop the session
stop_session(hostinfo)
return true
end
---Marks an account as discovered. The login with this account doesn't have to be successful, but <code>is_positive_result</code> should
-- return <code>true</code>.
--
-- If the result IS successful, and this hasn't been done before, this function will attempt to pull a userlist from the server.
--
-- The session should be stopped before entering this function, and restarted after -- that allows this function to make its own SMB calls.
--
--@param hostinfo The hostinfo table.
--@param username The username.
--@param password The password.
--@param result The result, as an integer constant.
--@return (status, err) If status is false, err is a string corresponding to the error; otherwise, err is undefined.
function found_account(hostinfo, username, password, result)
local status, err
-- Save the username
hostinfo['accounts'][username] = {}
hostinfo['accounts'][username]['password'] = password
hostinfo['accounts'][username]['result'] = result
-- Save the account (smb will automatically decide if it's better than the account it already has)
if(result == results.SUCCESS) then
-- Stop the connection -- this lets us do some queries
status, err = stop_session(hostinfo)
if(status == false) then
return false, err
end
-- Check if we have an 'admin' account
-- Try getting information about "IPC$". This determines whether or not the user is administrator
-- since only admins can get share info. Note that on Vista and up, unless UAC is disabled, all
-- accounts are non-admin.
local is_admin = smb.is_admin(hostinfo['host'], username, '', password, nil, nil)
-- Add the account
smb.add_account(hostinfo['host'], username, '', password, nil, nil, is_admin)
-- Check lockout policy
local status, bad_lockout_policy_result = bad_lockout_policy(hostinfo['host'])
if(not(status)) then
stdnse.print_debug(1, "smb-brute: WARNING: couldn't determine lockout policy: %s", bad_lockout_policy_result)
else
if(bad_lockout_policy_result) then
return false, "Account lockouts are enabled on the host. To continue (and risk lockouts), add --script-args=smblockout=1 -- for more information, run smb-enum-domains."
end
end
-- If we haven't retrieved the real user list yet, do so
if(hostinfo['have_user_list'] == false) then
-- Attempt to enumerate users
stdnse.print_debug(1, "smb-brute: Trying to get user list from server using newly discovered account")
hostinfo['have_user_list'], _, hostinfo['user_list'] = msrpc.get_user_list(hostinfo['host'])
hostinfo['user_list_index'] = 1
if(hostinfo['have_user_list'] and #hostinfo['user_list'] == 0) then
hostinfo['have_user_list'] = false
end
-- If the list was found, let the user know and reset the password list
if(hostinfo['have_user_list']) then
stdnse.print_debug(1, "smb-brute: Found %d accounts to check!", #hostinfo['user_list'])
reset_password(hostinfo)
-- Validate them (pick out the ones that can't possibly log in)
validate_usernames(hostinfo)
end
end
-- Start the session again
status, err = restart_session(hostinfo)
if(status == false) then
return false, err
end
end
end
---This is the main function that does all the work (loops through the lists and checks the results).
--
--@param host The host table.
--@return (status, accounts, locked_accounts) If status is false, accounts is an error message. Otherwise, accounts
-- is a table of passwords/results, indexed by the username and locked_accounts is a table indexed by locked
-- usernames.
local function go(host)
local status, err
local result, hostinfo
local password, temp_password, username
local response = {}
-- Initialize the hostinfo object, which sets up the initial variables
result, hostinfo = initialize(host)
if(result == false) then
return false, hostinfo
end
-- If invalid accounts don't give guest, we can determine the existence of users by trying to
-- log in with an invalid password and checking the value
status, err = validate_usernames(hostinfo)
if(status == false) then
return false, err
end
-- Start up the SMB session
status, err = restart_session(hostinfo)
if(status == false) then
return false, err
end
-- Loop through the password list
temp_password = get_next_password(hostinfo)
while(temp_password ~= nil) do
-- Loop through the user list
username = get_next_username(hostinfo)
while(username ~= nil) do
-- Check if it's a special case (we do this every loop because special cases are often
-- based on the username
if(temp_password == USERNAME) then
password = username
--io.write(string.format("Trying matching username/password (%s:%s)\n", username, password))
elseif(temp_password == USERNAME_REVERSED) then
password = string.reverse(username)
--io.write(string.format("Trying reversed username/password (%s:%s)\n", username, password))
else
password = temp_password
end
--io.write(string.format("%s:%s\n", username, password))
local result = check_login(hostinfo, username, password, get_type(hostinfo))
-- Check if the username was locked out
if(is_bad_result(hostinfo, result)) then
-- Add it to the list of locked usernames
hostinfo['locked_usernames'][username] = true
-- Unless the user requested to keep going, stop the check
if(not(nmap.registry.args.smblockout == "1" or nmap.registry.args.smblockout == "true")) then
-- Mark it as found, which is technically true
status, err = found_account(hostinfo, username, nil, results.ACCOUNT_LOCKED_NOW)
if(status == false) then
return err
end
-- Let the user know that it went badly
stdnse.print_debug(1, "smb-brute: '%s' became locked out; stopping", username)
return true, hostinfo['accounts'], hostinfo['locked_usernames']
else
stdnse.print_debug(1, "smb-brute: '%s' became locked out; continuing", username)
end
end
if(is_positive_result(hostinfo, result)) then
-- Reset the connection
stdnse.print_debug(2, "smb-brute: Found an account; resetting connection")
status, err = restart_session(hostinfo)
if(status == false) then
return false, err
end
-- Find the case of the password, unless it's a hash
if(not(#password == 32 or #password == 64 or #password == 65)) then
stdnse.print_debug(1, "smb-brute: Determining password's case (%s)", format_result(username, password))
case_password = find_password_case(hostinfo, username, password, result)
stdnse.print_debug(1, "smb-brute: Result: %s", format_result(username, case_password))
else
case_password = password
end
-- Take normal actions for finding an account
status, err = found_account(hostinfo, username, case_password, result)
if(status == false) then
return err
end
end
username = get_next_username(hostinfo)
end
reset_username(hostinfo)
temp_password = get_next_password(hostinfo)
end
stop_session(hostinfo)
return true, hostinfo['accounts'], hostinfo['locked_usernames']
end
--_G.TRACEBACK = TRACEBACK or {}
action = function(host)
-- TRACEBACK[coroutine.running()] = true;
local status, result
local response = {}
local username
local usernames = {}
local locked = {}
local i
status, result, locked_result = go(host)
if(status == false) then
return stdnse.format_output(false, result)
end
-- Put the usernames in their own table
for username in pairs(result) do
table.insert(usernames, username)
end
-- Sort the usernames alphabetically
table.sort(usernames)
-- Display the usernames
if(#usernames == 0) then
table.insert(response, "No accounts found")
else
for i=1, #usernames, 1 do
local username = usernames[i]
table.insert(response, format_result(username, result[username]['password'], result[username]['result']))
end
end
-- Make a list of locked accounts
for username in pairs(locked_result) do
table.insert(locked, username)
end
if(#locked > 0) then
-- Sort the list
table.sort(locked)
-- Display the list
table.insert(response, string.format("Locked accounts found: %s", stdnse.strjoin(", ", locked)))
end
return stdnse.format_output(true, response)
end
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