11

I've tried yes | ssh root@10.x.x.x to try to accept the RSA key fingerprint, but am still prompted if I'm sure I want to connect. Is there a way to make this automatic?

5

Add these to your bash startup file, or similar:

 #
 #  ssh + scp without storing or prompting for keys.
 #
 function sshtmp
 {
     ssh -o "ConnectTimeout 3" \
         -o "StrictHostKeyChecking no" \
         -o "UserKnownHostsFile /dev/null" \
              "$@"
 }
 function scptmp
 {
     exec scp -o "ConnectTimeout 3" \
         -o "StrictHostKeyChecking no" \
         -o "UserKnownHostsFile /dev/null" \
         "$@"
 }

Then use sshtmp, or scptmp in place of ssh and scp.

NOTE If you do go down this road you'll not be alerted that a host-key has changed and will lose security.

  • 4
    Thanks ssh -o "StrictHostKeyChecking no" root@10.x.x.x worked for me – VenomFangs Oct 21 '14 at 15:18
  • 16
    how is this the answer? The question was to accept the keys automatically, not ignore them! If this is asked and answered here then how do I find an answer to the actual question "Accept keys automatically"? Hate to do a downvote but come-on people, this is not the way stack-exchange should be! – JohnnyB Oct 7 '15 at 15:38
  • @JohnnyB take a look at my answer. It is not the cleanest solution, but it actually permits the key to be automatically accepted – RDP Dec 3 '16 at 2:34
11

OpenSSH 7.6 has introduced new StrictHostKeyChecking=accept-new setting for exactly this purpose:

ssh(1): expand the StrictHostKeyChecking option with two new
   settings. The first "accept-new" will automatically accept
   hitherto-unseen keys but will refuse connections for changed or
   invalid hostkeys. This is a safer subset of the current behaviour
   of StrictHostKeyChecking=no. The second setting "n", is a synonym
   for the current behaviour of StrictHostKeyChecking=no: accept new
   host keys, and continue connection for hosts with incorrect
   hostkeys. A future release will change the meaning of
   StrictHostKeyChecking=no to the behaviour of "accept-new".

(OpenSSH 7.6 Release notes)

10

Using SSH Programmatically with known hosts key

If what you want is to be able to use programmatically AND avoid Man-In-The-Middle attack, then I suggest you get the known fingerprint using the command ssh-keyscan. Example:

$ ssh-keyscan -t rsa,dsa github.com 2>/dev/null
github.com ssh-dss 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
github.com ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa+PXYPCPy6rbTrTtw7PHkccKrpp0yVhp5HdEIcKr6pLlVDBfOLX9QUsyCOV0wzfjIJNlGEYsdlLJizHhbn2mUjvSAHQqZETYP81eFzLQNnPHt4EVVUh7VfDESU84KezmD5QlWpXLmvU31/yMf+Se8xhHTvKSCZIFImWwoG6mbUoWf9nzpIoaSjB+weqqUUmpaaasXVal72J+UX2B+2RPW3RcT0eOzQgqlJL3RKrTJvdsjE3JEAvGq3lGHSZXy28G3skua2SmVi/w4yCE6gbODqnTWlg7+wC604ydGXA8VJiS5ap43JXiUFFAaQ==

Then you can forge a script to save it to a temporary file and use the UserKnownHostsFile option. The example below is a script, which can be called ssh_github:

#!/bin/bash

HOSTKEY='github.com ssh-dss AAAAB3NzaC1kc3MAAACBANGFW2P9xlGU3zWrymJgI/lKo//ZW2WfVtmbsUZJ5uyKArtlQOT2+WRhcg4979aFxgKdcsqAYW3/LS1T2km3jYW/vr4Uzn+dXWODVk5VlUiZ1HFOHf6s6ITcZvjvdbp6ZbpM+DuJT7Bw+                      h5Fx8Qt8I16oCZYmAPJRtu46o9C2zk1AAAAFQC4gdFGcSbp5Gr0Wd5Ay/jtcldMewAAAIATTgn4sY4Nem/FQE+XJlyUQptPWMem5fwOcWtSXiTKaaN0lkk2p2snz+EJvAGXGq9dTSWHyLJSM2W6ZdQDqWJ1k+cL8CARAqL+UMwF84CR0m3hj+wtVGD/J4G5kW2DBAf4/bqzP4469lT+dF2FRQ2L9JKXrCWcnhMtJUvua8dvnwAAAIB6C4nQfAA7x8oLta6tT+oCk2WQcydNsyugE8vLrHlogoWEicla6cWPk7oXSspbzUcfkjN3Qa6e74PhRkc7JdSdAlFzU3m7LMkXo1MHgkqNX8glxWNVqBSc0YRdbFdTkL0C6gtpklilhvuHQCdbgB3LBAikcRkDp+FCVkUgPC/7Rw==
github.com ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa+                                                                                                                                      PXYPCPy6rbTrTtw7PHkccKrpp0yVhp5HdEIcKr6pLlVDBfOLX9QUsyCOV0wzfjIJNlGEYsdlLJizHhbn2mUjvSAHQqZETYP81eFzLQNnPHt4EVVUh7VfDESU84KezmD5QlWpXLmvU31/yMf+Se8xhHTvKSCZIFImWwoG6mbUoWf9nzpIoaSjB+weqqUUmpaaasXVal72J+UX2B+    2RPW3RcT0eOzQgqlJL3RKrTJvdsjE3JEAvGq3lGHSZXy28G3skua2SmVi/w4yCE6gbODqnTWlg7+wC604ydGXA8VJiS5ap43JXiUFFAaQ=='

TEMPFILE=$(mktemp)
echo "$HOSTKEY" > $TEMPFILE

ssh -o "UserKnownHostsFile $TEMPFILE" $@

rm $TEMPFILE

With this, you can just run ssh_github instead of ssh and it will connect even if there is no known_hosts file where you put the script.

0

I just use:'ssh -o StrictHostKeyChecking=no user@host', it can also be used with pssh:'pssh -O StrictHostKeyChecking=no -h list.text -l user -A -i "cmd"'

Regards,

  • This worked for me, is there a reason why it was down voted? Also requires OpenSSH 7.6+ – Xenocide8998 Jul 2 '19 at 17:06
-3

You can use -y option: i.e. try

ssh -y root@10.x.x.x

-y Always accept remote host key if unknown

  • Welcome to Server Fault! Please use Markdown and/or the formatting options in the edit menu to properly type-set your posts to improve their readability. It is convention to format commands as "code". – HBruijn Dec 31 '16 at 16:26
  • Strange but in the man I see the following - -y Send log information using the syslog system module. By default this information is sent to stderr. – ALex_hha Feb 9 '17 at 20:22
  • I see the same in man. – Király István May 15 '17 at 11:39
  • this isn't a valid ssh option ? Where did you copy/paste this from ? – Flo Woo May 29 '17 at 8:46
  • 2
    This option only exists in dropbear SSH, not OpenSSH. – Jeremy Visser Jun 19 '17 at 7:12

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