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Operating Systems Linux Red Hat How to block ssh via /etc/hosts.deny Post 302292679 by fpmurphy on Sunday 1st of March 2009 09:15:27 AM
Old 03-01-2009
You have to use TCP wrappers. Assuming you are on RHEL5, sshd comes precompiled with TCP wrappers. You can use ldd to check if your particular sshd has TCP wrapper support, e.g.
Code:
# ldd /usr/sbin/sshd | grep libwrap
        libwrap.so.0 => /lib64/libwrap.so.0 (0x00002b14120a7000)

Note that access rules in /etc/hosts.allow are applied first i.e. they take precedence over rules specified in /etc/hosts.deny. Therefore, if access to a service is allowed in /etc/hosts.allow, a rule denying access to in /etc/hosts.deny is ignored because libwrap implements a "stop on first match" policy.
 

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SSH-KEYSIGN(8)						    BSD System Manager's Manual 					    SSH-KEYSIGN(8)

NAME
ssh-keysign -- ssh helper program for host-based authentication SYNOPSIS
ssh-keysign DESCRIPTION
ssh-keysign is used by ssh(1) to access the local host keys and generate the digital signature required during host-based authentication with SSH protocol version 2. ssh-keysign is disabled by default and can only be enabled in the global client configuration file /etc/ssh/ssh_config by setting EnableSSHKeysign to ``yes''. ssh-keysign is not intended to be invoked by the user, but from ssh(1). See ssh(1) and sshd(8) for more information about host-based authen- tication. FILES
/etc/ssh/ssh_config Controls whether ssh-keysign is enabled. /etc/ssh/ssh_host_dsa_key /etc/ssh/ssh_host_ecdsa_key /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys used to generate the digital signature. They should be owned by root, read- able only by root, and not accessible to others. Since they are readable only by root, ssh-keysign must be set-uid root if host- based authentication is used. /etc/ssh/ssh_host_dsa_key-cert.pub /etc/ssh/ssh_host_ecdsa_key-cert.pub /etc/ssh/ssh_host_rsa_key-cert.pub If these files exist they are assumed to contain public certificate information corresponding with the private keys above. SEE ALSO
ssh(1), ssh-keygen(1), ssh_config(5), sshd(8) HISTORY
ssh-keysign first appeared in OpenBSD 3.2. AUTHORS
Markus Friedl <markus@openbsd.org> BSD
August 31, 2010 BSD
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