Nmap rexec-brute NSE Script
This page contains detailed information about how to use the rexec-brute NSE script. For list of all NSE scripts, visit the Nmap NSE Library.
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Script Overview
Script source code: https://github.com/nmap/nmap/tree/master/scripts/rexec-brute.nse
Script categories: brute, intrusive
Target service / protocol: exec, tcp
Target network port(s): 512
List of CVEs: -
Script Description
The rexec-brute.nse script performs brute force password auditing against the classic UNIX rexec (remote exec) service.
Rexec-brute NSE Script Arguments
This is a full list of arguments supported by the rexec-brute.nse script:
rexec-brute.timeoutSocket timeout for connecting to rexec (default 10s)
creds.globalCredentials to be returned by Credentials.getCredentials regardless of the service.
creds.[service]Credentials to be returned by Credentials.getCredentials for [service]. E.g. creds.http=admin:password
passdbThe filename of an alternate password database. Default: nselib/data/passwords.lst
unpwdb.passlimit
The maximum number of passwords passwords
will return (default unlimited).
The maximum amount of time that any iterator will run before stopping. The value is in seconds by default and you can follow it with ms
, s
, m
, or h
for milliseconds, seconds, minutes, or hours. For example, unpwdb.timelimit=30m
or unpwdb.timelimit=.5h
for 30 minutes. The default depends on the timing template level (see the module description). Use the value 0
to disable the time limit.
The maximum number of usernames usernames
will return (default unlimited).
The filename of an alternate username database. Default: nselib/data/usernames.lst
brute.credfileA file containing username and password pairs delimited by '/'
brute.delayThe number of seconds to wait between guesses (default: 0)
brute.emptypassGuess an empty password for each user (default: false)
brute.firstonlyStop guessing after first password is found (default: false)
brute.guessesThe number of guesses to perform against each account. (default: 0 (unlimited)). The argument can be used to prevent account lockouts.
brute.modeCan be user, pass or creds and determines what mode to run the engine in.
- user - the unpwdb library is used to guess passwords, every password Password is tried for each user. (The user iterator is in the outer loop)
- pass - the unpwdb library is used to guess passwords, each password Is tried for every user. (The password iterator is in the outer loop)
- creds - a set of credentials (username and password pairs) are Guessed against the service. This allows for lists of known or common username and password combinations to be tested. If no mode is specified and the script has not added any custom iterator the pass mode will be enabled.
Iterate over passwords only for services that provide only a password for authentication. (default: false)
brute.retriesThe number of times to retry if recoverable failures occur. (default: 2)
brute.startThe number of threads the engine will start with. (default: 5).
brute.threadsThe number of initial worker threads, the number of active threads will be automatically adjusted.
brute.uniqueMake sure that each password is only guessed once (default: true)
brute.useraspassGuess the username as password for each user (default: true)
creds.[service]Credentials to be returned by Credentials.getCredentials for [service]. E.g. creds.http=admin:password
- - -
To use these script arguments, add them to the Nmap command line using the --script-args arg1=value,[arg2=value,..]
syntax. For example:
nmap --script=rexec-brute --script-args rexec-brute.timeout=value,creds.global=value <target>
Rexec-brute NSE Script Example Usage
Here's an example of how to use the rexec-brute.nse script:
nmap -p 512 --script rexec-brute <ip>
Rexec-brute NSE Script Example Output
Here's a sample output from the rexec-brute.nse script:
PORT STATE SERVICE
512/tcp open exec
| rexec-brute:
| Accounts
| nmap:test - Valid credentials
| Statistics
|_ Performed 16 guesses in 7 seconds, average tps: 2
Rexec-brute NSE Script Example XML Output
There is no sample XML output for this module. However, by providing the -oX <file>
option, Nmap will produce a XML output and save it in the file.xml
file.
Author
- Patrik Karlsson
References
- https://nmap.org/nsedoc/scripts/rexec-brute.html
- https://github.com/nmap/nmap/tree/master/scripts/rexec-brute.nse
See Also
Visit Nmap NSE Library for more scripts.
The rexec-brute.nse script may fail with the following error messages. Check for the possible causes by using the code snippets highlighted below found in the script source code. This can often times help in identifying the root cause of the problem.
Connection failed
Here is a relevant code snippet related to the "Connection failed" error message:
63: connect = function(self)
64: self.socket = brute.new_socket()
65: self.socket:set_timeout(self.timeout)
66: local status, err = self.socket:connect(self.host, self.port)
67: if ( not(status) ) then
68: local err = brute.Error:new("Connection failed")
69: err:setRetry( true )
70: return false, err
71: end
72: return true
73: end,
Send failed
Here is a relevant code snippet related to the "Send failed" error message:
76: local cmd = "id"
77: local data = ("\0%s\0%s\0%s\0"):format(username, password, cmd)
78:
79: local status, err = self.socket:send(data)
80: if ( not(status) ) then
81: local err = brute.Error:new("Send failed")
82: err:setRetry( true )
83: return false, err
84: end
85:
86: local response
Incorrect password
Here is a relevant code snippet related to the "Incorrect password" error message:
86: local response
87: status, response = self.socket:receive()
88: if ( status and not is_login_failure(response)) then
89: return true, creds.Account:new(username, password, creds.State.VALID)
90: end
91: return false, brute.Error:new( "Incorrect password" )
92: end,
93:
94: disconnect = function(self)
95: self.socket:close()
96: end,
Version
This page has been created based on Nmap version 7.92.
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