В линухе с openssh :
1. Основные конфиги - /etc/ssh/ : ssh_config - клиентская часть, sshd_config - сервера.
2. Затрагиваемые файлы (выдержка из мана) :
$HOME/.ssh/known_hosts
Records host keys for all hosts the user has logged into that are
not in /etc/ssh_known_hosts. See sshd(8).
$HOME/.ssh/identity, $HOME/.ssh/id_dsa, $HOME/.ssh/id_rsa
Contains the authentication identity of the user. They are for
protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
These files contain sensitive data and should be readable by the
user but not accessible by others (read/write/execute). Note
that ssh ignores a private key file if it is accessible by oth-
ers. It is possible to specify a passphrase when generating the
key; the passphrase will be used to encrypt the sensitive part of
this file using 3DES.
$HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub, $HOME/.ssh/id_rsa.pub
Contains the public key for authentication (public part of the
identity file in human-readable form). The contents of the
$HOME/.ssh/identity.pub file should be added to the file
$HOME/.ssh/authorized_keys on all machines where the user wishes
to log in using protocol version 1 RSA authentication. The con-
tents of the $HOME/.ssh/id_dsa.pub and $HOME/.ssh/id_rsa.pub file
should be added to $HOME/.ssh/authorized_keys on all machines
where the user wishes to log in using protocol version 2 DSA/RSA
authentication. These files are not sensitive and can (but need
not) be readable by anyone. These files are never used automati-
cally and are not necessary; they are only provided for the con-
venience of the user.
$HOME/.ssh/config
This is the per-user configuration file. The file format and
configuration options are described in ssh_config(5). Because of
the potential for abuse, this file must have strict permissions:
read/write for the user, and not accessible by others.
$HOME/.ssh/authorized_keys
Lists the public keys (RSA/DSA) that can be used for logging in
as this user. The format of this file is described in the
sshd(8) manual page. In the simplest form the format is the same
as the .pub identity files. This file is not highly sensitive,
but the recommended permissions are read/write for the user, and
not accessible by others.
/etc/ssh_known_hosts
Systemwide list of known host keys. This file should be prepared
by the system administrator to contain the public host keys of
all machines in the organization. This file should be world-
readable. This file contains public keys, one per line, in the
following format (fields separated by spaces): system name, pub-
lic key and optional comment field. When different names are
used for the same machine, all such names should be listed, sepa-
rated by commas. The format is described in the sshd(8) manual
page.
The canonical system name (as returned by name servers) is used
by sshd(8) to verify the client host when logging in; other names
are needed because ssh does not convert the user-supplied name to
a canonical name before checking the key, because someone with
access to the name servers would then be able to fool host
authentication.
/etc/ssh_config
Systemwide configuration file. The file format and configuration
options are described in ssh_config(5).
/etc/ssh_host_key, /etc/ssh_host_dsa_key, /etc/ssh_host_rsa_key
These three files contain the private parts of the host keys and
are used for RhostsRSAAuthentication and HostbasedAuthentication.
If the protocol version 1 RhostsRSAAuthentication method is used,
ssh must be setuid root, since the host key is readable only by
root. For protocol version 2, ssh uses ssh-keysign(8) to access
the host keys for HostbasedAuthentication. This eliminates the
requirement that ssh be setuid root when that authentication
method is used. By default ssh is not setuid root.
$HOME/.rhosts
This file is used in RhostsRSAAuthentication and
HostbasedAuthentication authentication to list the host/user
pairs that are permitted to log in. (Note that this file is also
used by rlogin and rsh, which makes using this file insecure.)
Each line of the file contains a host name (in the canonical form
returned by name servers), and then a user name on that host,
separated by a space. On some machines this file may need to be
world-readable if the user’s home directory is on a NFS parti-
tion, because sshd(8) reads it as root. Additionally, this file
must be owned by the user, and must not have write permissions
for anyone else. The recommended permission for most machines is
read/write for the user, and not accessible by others.
Note that sshd(8) allows authentication only in combination with
client host key authentication before permitting log in. If the
server machine does not have the client’s host key in
/etc/ssh_known_hosts, it can be stored in $HOME/.ssh/known_hosts.
The easiest way to do this is to connect back to the client from
the server machine using ssh; this will automatically add the
host key to $HOME/.ssh/known_hosts.
$HOME/.shosts
This file is used exactly the same way as .rhosts. The purpose
for having this file is to be able to use RhostsRSAAuthentication
and HostbasedAuthentication authentication without permitting
login with rlogin or rsh(1).
/etc/hosts.equiv
This file is used during RhostsRSAAuthentication and
HostbasedAuthentication authentication. It contains canonical
hosts names, one per line (the full format is described in the
sshd(8) manual page). If the client host is found in this file,
login is automatically permitted provided client and server user
names are the same. Additionally, successful client host key
authentication is required. This file should only be writable by
root.
/etc/shosts.equiv
This file is processed exactly as /etc/hosts.equiv. This file
may be useful to permit logins using ssh but not using
rsh/rlogin.
/etc/ssh/sshrc
Commands in this file are executed by ssh when the user logs in
just before the user’s shell (or command) is started. See the
sshd(8) manual page for more information.
$HOME/.ssh/rc
Commands in this file are executed by ssh when the user logs in
just before the user’s shell (or command) is started. See the
sshd(8) manual page for more information.
$HOME/.ssh/environment
Contains additional definitions for environment variables, see
section ENVIRONMENT above.
3. Пишет лог по адресу /var/log/secure
4. Пароли вообще-то не хранит, хранит ключи - см. список файлов п.2
5. man ssh :)