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SSH root login from one ip via certificate only, all other logins password only.

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  SSH root login from one ip via certificate only, all other logins  password only. James Allsopp <jamesaallsopp@googlemail.com> - 2018-08-29 14:40 +0200
    Re: SSH root login from one ip via certificate only, all other  logins password only. Joe <joe@jretrading.com> - 2018-08-29 14:50 +0200
    Re: SSH root login from one ip via certificate only, all other  logins  password only. Dan Purgert <dan@djph.net> - 2018-08-29 15:20 +0200

#199574 — SSH root login from one ip via certificate only, all other logins password only.

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Hi,
I need to have one computer I can ssh to other computers as root for
Ansible. To do this I've set up a strong certificate with a password, but
what I want is to only be able to log in as root from one IP using that
cert. All other users should only log in via a password and can do so from
any IP.

Currently normal user logins are broken with this sshd_config. Can anyone
tell me where I'm going wrong? Sudo is not an option.

Thanks
James

#       $OpenBSD: sshd_config,v 1.93 2014/01/10 05:59:19 djm Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/local/bin:/usr/bin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options override the
# default value.

# If you want to change the port on a SELinux system, you have to tell
# SELinux about this change.
# semanage port -a -t ssh_port_t -p tcp #PORTNUMBER
#
#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

# The default requires explicit activation of protocol 1
#Protocol 2

# HostKey for protocol version 1
#HostKey /etc/ssh/ssh_host_key
# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key

# Lifetime and size of ephemeral version 1 server key
#KeyRegenerationInterval 1h
#ServerKeyBits 1024

# Ciphers and keying
#RekeyLimit default none

# Logging
# obsoletes QuietMode and FascistLogging
#SyslogFacility AUTH
SyslogFacility AUTHPRIV
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin no
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

#RSAAuthentication yes
#PubkeyAuthentication yes

# The default is to check both .ssh/authorized_keys and
.ssh/authorized_keys2
# but this is overridden so installations will only check
.ssh/authorized_keys
AuthorizedKeysFile      .ssh/authorized_keys

#AuthorizedPrincipalsFile none

#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#RhostsRSAAuthentication no
# similar for protocol version 2
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# RhostsRSAAuthentication and HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes

# To disable tunneled clear text passwords, change to no here!
#PermitEmptyPasswords no
#PasswordAuthentication yes

# Change to no to disable s/key passwords
#ChallengeResponseAuthentication yes
#ChallengeResponseAuthentication no

# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no
#KerberosUseKuserok yes

# GSSAPI options
GSSAPIAuthentication yes
GSSAPICleanupCredentials no
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no
#GSSAPIEnablek5users no

# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
# WARNING: 'UsePAM no' is not supported in Red Hat Enterprise Linux and may
cause several
# problems.
#UsePAM yes

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
UsePrivilegeSeparation sandbox          # Default for new installations.
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#ShowPatchLevel no
#UseDNS yes
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none

# no default banner path
#Banner none

# Accept locale-related environment variables
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY
LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS

# override default of no subsystems
Subsystem       sftp    /usr/libexec/openssh/sftp-server

# Example of overriding settings on a per-user basis
#Match User anoncvs
#       X11Forwarding no
#       AllowTcpForwarding no
#       PermitTTY no
#       ForceCommand cvs server
Match User root Address x.y.z.w
      PermitRootLogin yes
      PermitTunnel no
      PasswordAuthentication no
Match all
      PermitRootLogin no
      PasswordAuthentication yes
      PermitTunnel no

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#199579 — Re: SSH root login from one ip via certificate only, all other logins password only.

On Wed, 29 Aug 2018 13:32:56 +0100
James Allsopp <jamesaallsopp@googlemail.com> wrote:

> Hi,
> I need to have one computer I can ssh to other computers as root for
> Ansible. To do this I've set up a strong certificate with a password,
> but what I want is to only be able to log in as root from one IP
> using that cert. All other users should only log in via a password
> and can do so from any IP.
> 
> Currently normal user logins are broken with this sshd_config. Can
> anyone tell me where I'm going wrong? Sudo is not an option.
> 

I'd think it ought to be possible. Personally, I'd run two instances of
sshd, it's pretty lightweight, and that would (probably) eliminate
potential obscure bugs where the authors hadn't expected anyone to want
to do this.

-- 
Joe

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#199584 — Re: SSH root login from one ip via certificate only, all other logins password only.

James Allsopp wrote:
> Hi,
> I need to have one computer I can ssh to other computers as root for
> Ansible. To do this I've set up a strong certificate with a password, but
> what I want is to only be able to log in as root from one IP using that
> cert. All other users should only log in via a password and can do so from
> any IP.
>
> Currently normal user logins are broken with this sshd_config. Can anyone
> tell me where I'm going wrong? Sudo is not an option.
>
> [...]
> #PermitRootLogin no

Change this to "without-password" to force key-based logins.  (Yeah, I
know this is in the global section but I'm not reading through the rest
of your config).

Alternately, if you don't want this as a global setting, an additional
stanza along these lines will take care of it:

match User root Address 192.0.2.10
  PermitRootLogin without-password

You shouldn't have to bother trying to create any rules for the  other
users, as without a "match" directive, they'll just use the global
settings


-- 
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|_|_|O| Github: https://github.com/dpurgert
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