Difference between revisions of "Ssh"

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=Links=
*[http://blog.joncairns.com/2013/12/understanding-ssh-agent-and-ssh-add/ Understanding ssh-agent and ssh-add]


= Links =


=FAQ=
*[http://blog.joncairns.com/2013/12/understanding-ssh-agent-and-ssh-add/ Understanding ssh-agent and ssh-add]
*[https://www.ssh.com/ssh/key/ https://www.ssh.com/ssh/key/]
 
 
 
 
= FAQ =
 
==ssh multiplexing==
https://www.cyberciti.biz/faq/linux-unix-reuse-openssh-connection
 
== remember key passphrase ==


==remember key passphrase==
  ssh-agent bash
  ssh-agent bash
  ssh-add ~/.ssh/id_rsa
  ssh-add ~/.ssh/id_rsa


==root access from single host==
== root access from single host ==
 
  Match Address 192.168.1.100
  Match Address 192.168.1.100
         PermitRootLogin yes
         PermitRootLogin yes


==multihop tunnel==
== multihop tunnel ==
 
  ssh -A -t -l user jump-host \
  ssh -A -t -l user jump-host \
  -L 8080:localhost:8080 \
  -L 8080:localhost:8080 \
Line 19: Line 30:
  -L 8080:localhost:8080
  -L 8080:localhost:8080


OR
in .ssh/config define
Host targethost
ProxyCommand ssh jumphost -W %h:%p
and then just
ssh -L 1234:<LAN address>:<port> targethost
== SSH tunnel with putty ==
[https://www.skyverge.com/blog/how-to-set-up-an-ssh-tunnel-with-putty/ https://www.skyverge.com/blog/how-to-set-up-an-ssh-tunnel-with-putty/]
== Failed publickey ==


==SSH tunnel with putty==
*acccess rights?
https://www.skyverge.com/blog/how-to-set-up-an-ssh-tunnel-with-putty/


==Failed publickey==
== 14: No supported authentication methods available [preauth] ==
*acccess rights?


==14: No supported authentication methods available [preauth]==
Putty not configured to look at correct private key?
Putty not configured to look at correct private key?


&nbsp;


==chrooted sftp==
== chrooted sftp ==
 
Homedir as defined in /etc/passwd /home/someuser


Homedir as defined in /etc/passwd
/home/someuser
  chmod 755 /home/someuser
  chmod 755 /home/someuser
  chown root.root /home/someuser
  chown root.root /home/someuser


And then create writable dir for user:
And then create writable dir for user:
  mkdir /home/someuser/downloads
  mkdir /home/someuser/downloads
  chown someuser.someuser /home/someuser/downloads
  chown someuser.someuser /home/someuser/downloads


&nbsp;


 
Subsystem sftp internal-sftp
Subsystem       sftp   internal-sftp


'''Per group:'''
'''Per group:'''


/etc/ssh/sshd_config
/etc/ssh/sshd_config
   Match Group sftponly
   Match Group sftponly
     ChrootDirectory %h
     ChrootDirectory %h
Line 69: Line 92:
   Match all
   Match all


The ChrootDirectory must be owned by root.root with permissons 755.
The ChrootDirectory must be owned by root.root with permissons 755. If you want group based access rights, you can do that in subdirectories.
If you want group based access rights, you can do that in subdirectories.


&nbsp;


== ssh tunnel ==
== ssh tunnel ==
Line 85: Line 108:
Maybe try ssh -4
Maybe try ssh -4


==Unable to negotiate with 192.168.100.4 port 22: no matching cipher found.==
== Unable to negotiate with 192.168.100.4 port 22: no matching cipher found. ==
 
passing old cipher, like -o arcfour??
passing old cipher, like -o arcfour??


==rsync only as root==
==no matching host key type found==
if that comes after 'rsa' try
PubkeyAcceptedKeyTypes=+ssh-rsa
in .ssh/config
 
== rsync only as root ==
 
== scp: no matching key exchange method found. ==
 
scp seems to ignore .ssh/config, so use
 
scp -o Ciphers=xxx
 
&nbsp;
 
== kex_exchange_identification: read: Connection reset by peer ==
 
only way to find out about that is look on server
 
== Reverse tunnel with autossh ==
# https://superuser.com/questions/37738/how-to-reliably-keep-an-ssh-tunnel-open
autossh -M 0 -o "ServerAliveInterval 30" -o "ServerAliveCountMax 3" -fgNR :10023:localhost:22 the.server
 
And in the.server:/etc/ssh/sshd_config
 
GatewayPorts clientspecified
 
to allow connecting to 10023 from outside
 
As systemd service:
In /etc/systemd/system/sshtunnel.service
[Unit]
Description=SSH Tunnel
After=network.target
 
[Service]
Restart=always
RestartSec=20
User=root
ExecStart=/bin/ssh -o ServerAliveInterval=30 -o ServerAliveCountMax=6 -gNR :10023:localhost:22 user@ssh.example.com
 
[Install]
WantedBy=multi-user.target
 
==The RSA host key for host has changed==
If you're migrating to a new server: copy /etc/ssh/ssh_host_rsa_key* to the new server
 
 
== ssh require both key and user password ==
In sshd_config
  AuthenticationMethods "publickey,password"
# do not just set to no!
#PasswordAuthentication yes
 
== add your key to remote authorized_keys ==
ssh-copy-id remotehost
or, if not installed:
cat ~/.ssh/rsa_pub.id | ssh remotehost "cat >> ~/.ssh/authorized_keys"
 
== Show key fingerprint ==
ssh-keygen -lf /etc/ssh/ssh_host_rsa_key.pub

Revision as of 15:10, 23 June 2022

Links



FAQ

ssh multiplexing

https://www.cyberciti.biz/faq/linux-unix-reuse-openssh-connection

remember key passphrase

ssh-agent bash
ssh-add ~/.ssh/id_rsa

root access from single host

Match Address 192.168.1.100
       PermitRootLogin yes

multihop tunnel

ssh -A -t -l user jump-host \
-L 8080:localhost:8080 \
ssh -A -t -l user webserver.dmz \
-L 8080:localhost:8080

OR in .ssh/config define

Host targethost
ProxyCommand ssh jumphost -W %h:%p

and then just

ssh -L 1234:<LAN address>:<port> targethost

SSH tunnel with putty

https://www.skyverge.com/blog/how-to-set-up-an-ssh-tunnel-with-putty/

Failed publickey

  • acccess rights?

14: No supported authentication methods available [preauth]

Putty not configured to look at correct private key?

 

chrooted sftp

Homedir as defined in /etc/passwd /home/someuser

chmod 755 /home/someuser
chown root.root /home/someuser

And then create writable dir for user:

mkdir /home/someuser/downloads
chown someuser.someuser /home/someuser/downloads

 

Subsystem sftp internal-sftp

Per group:

/etc/ssh/sshd_config

 Match Group sftponly
   ChrootDirectory %h
   ForceCommand internal-sftp
   AllowTcpForwarding no
   PermitTunnel no
   X11Forwarding no
 #Remember this one to close Match block!
 Match all

Per user:

 Match User username
   ChrootDirectory %h
   ForceCommand internal-sftp
   AllowTcpForwarding no
   PermitTunnel no
   X11Forwarding no
 #Remember this one to close Match block!
 Match all

The ChrootDirectory must be owned by root.root with permissons 755. If you want group based access rights, you can do that in subdirectories.

 

ssh tunnel

ssh -L 1234:192.168.100.2:80 remotehost

And then connect to localhost:1234

 

bind Cannot assign requested address

Maybe try ssh -4

Unable to negotiate with 192.168.100.4 port 22: no matching cipher found.

passing old cipher, like -o arcfour??

no matching host key type found

if that comes after 'rsa' try

PubkeyAcceptedKeyTypes=+ssh-rsa

in .ssh/config

rsync only as root

scp: no matching key exchange method found.

scp seems to ignore .ssh/config, so use

scp -o Ciphers=xxx

 

kex_exchange_identification: read: Connection reset by peer

only way to find out about that is look on server

Reverse tunnel with autossh

  1. https://superuser.com/questions/37738/how-to-reliably-keep-an-ssh-tunnel-open
autossh -M 0 -o "ServerAliveInterval 30" -o "ServerAliveCountMax 3" -fgNR :10023:localhost:22 the.server

And in the.server:/etc/ssh/sshd_config

GatewayPorts clientspecified

to allow connecting to 10023 from outside

As systemd service: In /etc/systemd/system/sshtunnel.service

[Unit]
Description=SSH Tunnel
After=network.target
[Service]
Restart=always
RestartSec=20
User=root
ExecStart=/bin/ssh -o ServerAliveInterval=30 -o ServerAliveCountMax=6 -gNR :10023:localhost:22 user@ssh.example.com
[Install]
WantedBy=multi-user.target

The RSA host key for host has changed

If you're migrating to a new server: copy /etc/ssh/ssh_host_rsa_key* to the new server


ssh require both key and user password

In sshd_config
 AuthenticationMethods "publickey,password"
# do not just set to no!
#PasswordAuthentication yes

add your key to remote authorized_keys

ssh-copy-id remotehost

or, if not installed:

cat ~/.ssh/rsa_pub.id | ssh remotehost "cat >> ~/.ssh/authorized_keys"

Show key fingerprint

ssh-keygen -lf /etc/ssh/ssh_host_rsa_key.pub