Cerberus FTP Server SFTP Username Enumeration - Metasploit


This page contains detailed information about how to use the auxiliary/scanner/ssh/cerberus_sftp_enumusers metasploit module. For list of all metasploit modules, visit the Metasploit Module Library.

Table Of Contents
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Module Overview

Name: Cerberus FTP Server SFTP Username Enumeration
Module: auxiliary/scanner/ssh/cerberus_sftp_enumusers
Source code: modules/auxiliary/scanner/ssh/cerberus_sftp_enumusers.rb
Disclosure date: 2014-05-27
Last modification time: 2020-10-02 17:38:06 +0000
Supported architecture(s): -
Supported platform(s): -
Target service / protocol: -
Target network port(s): 22
List of CVEs: -

This module uses a dictionary to brute force valid usernames from Cerberus FTP server via SFTP. This issue affects all versions of the software older than 6.0.9.0 or 7.0.0.2 and is caused by a discrepancy in the way the SSH service handles failed logins for valid and invalid users. This issue was discovered by Steve Embling.

Module Ranking and Traits

Module Ranking:

  • normal: The exploit is otherwise reliable, but depends on a specific version and can't (or doesn't) reliably autodetect. More information about ranking can be found here.

Basic Usage

This module is a scanner module, and is capable of testing against multiple hosts.

msf > use auxiliary/scanner/ssh/cerberus_sftp_enumusers
msf auxiliary(cerberus_sftp_enumusers) > show options
    ... show and set options ...
msf auxiliary(cerberus_sftp_enumusers) > set RHOSTS ip-range
msf auxiliary(cerberus_sftp_enumusers) > exploit

Other examples of setting the RHOSTS option:

Example 1:

msf auxiliary(cerberus_sftp_enumusers) > set RHOSTS 192.168.1.3-192.168.1.200

Example 2:

msf auxiliary(cerberus_sftp_enumusers) > set RHOSTS 192.168.1.1/24

Example 3:

msf auxiliary(cerberus_sftp_enumusers) > set RHOSTS file:/tmp/ip_list.txt

Required Options

  • RHOSTS: The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'

  • USER_FILE: Files containing usernames, one per line

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Msfconsole Usage

Here is how the scanner/ssh/cerberus_sftp_enumusers auxiliary module looks in the msfconsole:

msf6 > use auxiliary/scanner/ssh/cerberus_sftp_enumusers

msf6 auxiliary(scanner/ssh/cerberus_sftp_enumusers) > show info

       Name: Cerberus FTP Server SFTP Username Enumeration
     Module: auxiliary/scanner/ssh/cerberus_sftp_enumusers
    License: Metasploit Framework License (BSD)
       Rank: Normal
  Disclosed: 2014-05-27

Provided by:
  Steve Embling
  Matt Byrne <[email protected]>

Check supported:
  No

Basic options:
  Name       Current Setting  Required  Description
  ----       ---------------  --------  -----------
  Proxies                     no        A proxy chain of format type:host:port[,type:host:port][...]
  RHOSTS                      yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
  RPORT      22               yes       The target port
  THREADS    1                yes       The number of concurrent threads (max one per host)
  USER_FILE                   yes       Files containing usernames, one per line

Description:
  This module uses a dictionary to brute force valid usernames from 
  Cerberus FTP server via SFTP. This issue affects all versions of the 
  software older than 6.0.9.0 or 7.0.0.2 and is caused by a 
  discrepancy in the way the SSH service handles failed logins for 
  valid and invalid users. This issue was discovered by Steve Embling.

References:
  http://xforce.iss.net/xforce/xfdb/93546
  http://www.securityfocus.com/bid/67707

Module Options

This is a complete list of options available in the scanner/ssh/cerberus_sftp_enumusers auxiliary module:

msf6 auxiliary(scanner/ssh/cerberus_sftp_enumusers) > show options

Module options (auxiliary/scanner/ssh/cerberus_sftp_enumusers):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   Proxies                     no        A proxy chain of format type:host:port[,type:host:port][...]
   RHOSTS                      yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
   RPORT      22               yes       The target port
   THREADS    1                yes       The number of concurrent threads (max one per host)
   USER_FILE                   yes       Files containing usernames, one per line

Advanced Options

Here is a complete list of advanced options supported by the scanner/ssh/cerberus_sftp_enumusers auxiliary module:

msf6 auxiliary(scanner/ssh/cerberus_sftp_enumusers) > show advanced

Module advanced options (auxiliary/scanner/ssh/cerberus_sftp_enumusers):

   Name                 Current Setting  Required  Description
   ----                 ---------------  --------  -----------
   RETRY_NUM            3                yes       The number of attempts to connect to a SSH server for each user
   SSH_DEBUG            false            yes       Enable SSH debugging output (Extreme verbosity!)
   SSH_TIMEOUT          10               yes       Specify the maximum time to negotiate a SSH session
   ShowProgress         true             yes       Display progress messages during a scan
   ShowProgressPercent  10               yes       The interval in percent that progress should be shown
   VERBOSE              false            no        Enable detailed status messages
   WORKSPACE                             no        Specify the workspace for this module

Auxiliary Actions

This is a list of all auxiliary actions that the scanner/ssh/cerberus_sftp_enumusers module can do:

msf6 auxiliary(scanner/ssh/cerberus_sftp_enumusers) > show actions

Auxiliary actions:

   Name  Description
   ----  -----------

Evasion Options

Here is the full list of possible evasion options supported by the scanner/ssh/cerberus_sftp_enumusers auxiliary module in order to evade defenses (e.g. Antivirus, EDR, Firewall, NIDS etc.):

msf6 auxiliary(scanner/ssh/cerberus_sftp_enumusers) > show evasion

Module evasion options:

   Name  Current Setting  Required  Description
   ----  ---------------  --------  -----------

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Error Messages

This module may fail with the following error messages:

Error Messages

Check for the possible causes from the code snippets below found in the module source code. This can often times help in identifying the root cause of the problem.

Cannot read file <USER_FILE>

Here is a relevant code snippet related to the "Cannot read file <USER_FILE>" error message:

169:	    if File.readable? datastore['USER_FILE']
170:	      users = File.new(datastore['USER_FILE']).read.split
171:	      users.each {|u| u.downcase!}
172:	      users.uniq!
173:	    else
174:	      raise ArgumentError, "Cannot read file #{datastore['USER_FILE']}"
175:	    end
176:	
177:	    users
178:	  end
179:

<PEER-IP> Retrying '<USER>' due to connection error

Here is a relevant code snippet related to the "<PEER-IP> Retrying '<USER>' due to connection error" error message:

182:	    ret = nil
183:	
184:	    while (attempt_num <= retry_num) && (ret.nil? || ret == :connection_error)
185:	      if attempt_num > 0
186:	        Rex.sleep(2 ** attempt_num)
187:	        vprint_status("#{peer(ip)} Retrying '#{user}' due to connection error")
188:	      end
189:	
190:	      ret = check_user(ip, user, rport)
191:	      attempt_num += 1
192:	    end

<PEER-IP> User '<USER>' could not connect

Here is a relevant code snippet related to the "<PEER-IP> User '<USER>' could not connect" error message:

198:	    case attempt_result
199:	    when :success
200:	      print_good "#{peer(ip)} User '#{user}' found"
201:	      do_report(ip, user, rport)
202:	    when :connection_error
203:	      print_error "#{peer(ip)} User '#{user}' could not connect"
204:	    when :fail
205:	      vprint_status "#{peer(ip)} User '#{user}' not found"
206:	    end
207:	  end
208:

<PEER-IP> User '<USER>' not found

Here is a relevant code snippet related to the "<PEER-IP> User '<USER>' not found" error message:

200:	      print_good "#{peer(ip)} User '#{user}' found"
201:	      do_report(ip, user, rport)
202:	    when :connection_error
203:	      print_error "#{peer(ip)} User '#{user}' could not connect"
204:	    when :fail
205:	      vprint_status "#{peer(ip)} User '#{user}' not found"
206:	    end
207:	  end
208:	
209:	  def run_host(ip)
210:	    print_status "#{peer(ip)} Checking for vulnerability"

<PEER-IP> Not vulnerable

Here is a relevant code snippet related to the "<PEER-IP> Not vulnerable" error message:

214:	      print_status "#{peer(ip)} Starting scan"
215:	      user_list.each do |user|
216:	        show_result(attempt_user(user, ip), user, ip)
217:	      end
218:	    when :safe
219:	      print_error "#{peer(ip)} Not vulnerable"
220:	    when :connection_error
221:	      print_error "#{peer(ip)} Connection failed"
222:	    end
223:	  end
224:	end

<PEER-IP> Connection failed

Here is a relevant code snippet related to the "<PEER-IP> Connection failed" error message:

215:	      user_list.each do |user|
216:	        show_result(attempt_user(user, ip), user, ip)
217:	      end
218:	    when :safe
219:	      print_error "#{peer(ip)} Not vulnerable"
220:	    when :connection_error
221:	      print_error "#{peer(ip)} Connection failed"
222:	    end
223:	  end
224:	end
225:

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References

See Also

Check also the following modules related to this module:

Authors

  • Steve Embling
  • Matt Byrne <attackdebris[at]gmail.com>

Version

This page has been produced using Metasploit Framework version 6.1.27-dev. For more modules, visit the Metasploit Module Library.

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