Re: ssh between el7 and fc28 boxes

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On 12/3/18 1:07 PM, John Pilkington wrote:
> On 03/12/2018 19:19, Rick Stevens wrote:
>> On 12/3/18 10:16 AM, John Pilkington wrote:
>>> On 03/12/2018 17:30, Rick Stevens wrote:
>>>> On 12/3/18 8:15 AM, John Pilkington wrote:
>>>>> Hi:  I have two boxes connected to the same router.  One runs SL7.5,
>>>>> from tomorrow probably SL7.6, which is an el7 clone, and the other
>>>>> runs
>>>>> Fedora 28.
>>>>>
>>>>> I can ssh and rsync from F28 to SL7, but permission is denied in the
>>>>> opposite direction.  Port 22 is open.  I now have copies of both
>>>>> versions of /etc/sshd and intend to examine diffs.
>>>>>
>>>>> Google provides many links but nothing that looks authoritative or,
>>>>> preferably, authoritative and simple.  Any help wpuld be appreciated.
>>>>
>>>> You need to look at the logs or messages when you try to connect from
>>>> SL7 to F28 (and F29 is current).
>>>>
>>>> Odds are that SL7 is using a cipher or an algorithm that is deemed
>>>> insecure in the latest sshd implementations at the F28 end and you'll
>>>> either need to have sshd on F28 accept it (via a "Ciphers" or
>>>> "KexAlgorithms" option in /etc/ssh/sshd_config) or use one of the
>>>> acceptable ciphers/algorithms at the client (SL7) end.
>>>>
>>>> Logs and error messages are your friends in these cases.
>>>
>>> Thanks Rick.  The SL7.5 to 7.6 upgrade has just completed but
>>> 'Connection refused' still.  The only effective diffs between the
>>> sshd_configs appeared to be in F28, 'PermitRootLogin yes' and 'PrintMotd
>>> no'.  So I'll try to get some more verbose logs.
>>
>> "PermitRootLogin yes" is dangerous (allows root to log in via ssh) so
>> I wouldn't suggest leaving that alone. I'd set it to "no" and restart
>> sshd ("systemctl restart sshd.service"). You'll need to log in as a non-
>> root user and "sudo" stuff, but it's safer.
>>
>> As to the other stuff, try "ssh -v <hostname-or-addr-of-f28-system>"
> 
> [john@HP_Box ~]$ ssh -v -v -v john@192.168.1.66
> OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017
> debug1: Reading configuration data /etc/ssh/ssh_config
> debug1: /etc/ssh/ssh_config line 58: Applying options for *
> debug2: resolving "192.168.1.66" port 22
> debug2: ssh_connect_direct: needpriv 0
> debug1: Connecting to 192.168.1.66 [192.168.1.66] port 22.
> debug1: connect to address 192.168.1.66 port 22: Connection refused
> ssh: connect to host 192.168.1.66 port 22: Connection refused
> 
> F28 /etc/ssh/ssh_config line 58 is a blank line among lines commented out.

Ok, the "connection refused" bit indicates that sshd isn't running. Run
"sudo systemctl enable sshd.service" to enable it to start at boot, and
"sudo systemctl start sshd.service" to start it immediately.

>> from the SL client, see what it says and post that. Oh, and make sure
>> the F28 firewall is permitting incoming TCP port 22 (can't recall if it
>> does that by default). You can find that by, as root:
>>
>>     # firewall-cmd --get-default-zone
>>     # firewall-cmd --info-zone <value-from-prev-cmd>
>>
>> Look for the service "ssh" or something like "22/tcp". On one of my
>> machines (ssh service marked with "^^^"):
>>
>>     [root@prophead ~]# firewall-cmd --get-default-zone
>>     public
>>     [root@prophead ~]# firewall-cmd --info-zone public
>>     public (active)
>>       target: default
>>       icmp-block-inversion: no
>>       interfaces: em1 eno1
>>       sources:
>>       services: dhcpv6-client mdns sane ssh synergy tftp tftp-client
>>                         ^^^
>>       ports: 54925/udp 1900/udp 49152/tcp 514/udp 8200/tcp 514/tcp
>> 1935/tcp
>> 161/udp
>>       protocols:
>>       masquerade: no
>>       forward-ports:
>>       source-ports:
>>       icmp-blocks:
>>       rich rules:
> The zone is 'home', services include ssh; I have other ports (for
> mythtv) enabled.  No obvious discrepancies.
> 
> But I was using the firewall-config GUI and got repeated instances of
> 
> (firewall-config: 28658): Gtk-WARNING**: <time> Failed to set text from
> markup due to error parsing markup:  Unknown tag 'interface' on line 1
> char 20
> 
> The 'interface' field in the GUI has enp0s25 Comment: Used by network
> connection xxxxxxx

Yeah, if you see "ssh" and/or "22/tcp" then the firewall is open for
incoming ssh connections. Do the "systemctl" stuff above and try again.
----------------------------------------------------------------------
- Rick Stevens, Systems Engineer, AllDigital    ricks@xxxxxxxxxxxxxx -
- AIM/Skype: therps2        ICQ: 226437340           Yahoo: origrps2 -
-                                                                    -
-         The world is coming to an end ... SAVE YOUR FILES!!!       -
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