09-07-2015
Ssh enforcement
Hi,
I am trying to force a server to only accept ssh connections which are:
a. the ssh key connecting to the server has 2048 bits
b. The ssh key they use has a password set on the private key
I have seen in /etc/ssh/sshd_config there are two such parameters:
1. ServerKeyBits
2. PermitEmptyPasswords no
But when these are set to the appropriate values ie (1) 2048 (2) no, it still fails in that users can login with no private key password, and also users with eg 1024 bit keys can login.
I am running Redhat 6.6, but I have tried this on RHEL 3.X as well with the same results.
Thanks in advance
Mantis
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LEARN ABOUT POSIX
ssh-keysign
ssh-keysign(1M) ssh-keysign(1M)
NAME
ssh-keysign - ssh helper program for host-based authentication
SYNOPSIS
ssh-keysign
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. This signature is of data that includes, among other items, the name of the client host and the name of the
client user.
ssh-keysign is disabled by default and can be enabled only in the global client configuration file /etc/ssh/ssh_config by setting Host-
basedAuthentication to yes.
ssh-keysign is not intended to be invoked by the user, but from ssh. See ssh(1) and sshd(1M) for more information about host-based authen-
tication.
/etc/ssh/ssh_config
Controls whether ssh-keysign is enabled.
/etc/ssh/ssh_host_dsa_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, readable
only by root, and not accessible to others. Because they are readable only by root, ssh-keysign must be set-uid root if host-based
authentication is used.
ssh-keysign will not sign host-based authentication data under the following conditions:
o If the HostbasedAuthentication client configuration parameter is not set to yes in /etc/ssh/ssh_config. This setting cannot be overri-
den in users' ~/.ssh/ssh_config files.
o If the client hostname and username in /etc/ssh/ssh_config do not match the canonical hostname of the client where ssh-keysign is
invoked and the name of the user invoking ssh-keysign.
In spite of ssh-keysign's restrictions on the contents of the host-based authentication data, there remains the ability of users to use it
as an avenue for obtaining the client's private host keys. For this reason host-based authentication is turned off by default.
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWsshu |
+-----------------------------+-----------------------------+
|Interface Stability |Evolving |
+-----------------------------+-----------------------------+
ssh(1), sshd(1M), ssh_config(4), attributes(5)
AUTHORS
Markus Friedl, markus@openbsd.org
HISTORY
ssh-keysign first appeared in Ox 3.2.
9 Jun 2004 ssh-keysign(1M)