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636 lines
33 KiB
Plaintext
636 lines
33 KiB
Plaintext
SSHD(8) System Manager's Manual SSHD(8)
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NAME
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sshd M-bM-^@M-^S OpenSSH SSH daemon
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SYNOPSIS
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sshd [-46DdeiqTt] [-b bits] [-C connection_spec]
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[-c host_certificate_file] [-E log_file] [-f config_file]
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[-g login_grace_time] [-h host_key_file] [-k key_gen_time]
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[-o option] [-p port] [-u len]
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DESCRIPTION
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sshd (OpenSSH Daemon) is the daemon program for ssh(1). Together these
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programs replace rlogin and rsh, and provide secure encrypted
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communications between two untrusted hosts over an insecure network.
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sshd listens for connections from clients. It is normally started at
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boot from /etc/rc. It forks a new daemon for each incoming connection.
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The forked daemons handle key exchange, encryption, authentication,
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command execution, and data exchange.
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sshd can be configured using command-line options or a configuration file
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(by default sshd_config(5)); command-line options override values
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specified in the configuration file. sshd rereads its configuration file
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when it receives a hangup signal, SIGHUP, by executing itself with the
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name and options it was started with, e.g. /usr/sbin/sshd.
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The options are as follows:
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-4 Forces sshd to use IPv4 addresses only.
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-6 Forces sshd to use IPv6 addresses only.
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-b bits
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Specifies the number of bits in the ephemeral protocol version 1
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server key (default 1024).
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-C connection_spec
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Specify the connection parameters to use for the -T extended test
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mode. If provided, any Match directives in the configuration
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file that would apply to the specified user, host, and address
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will be set before the configuration is written to standard
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output. The connection parameters are supplied as keyword=value
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pairs. The keywords are M-bM-^@M-^\userM-bM-^@M-^], M-bM-^@M-^\hostM-bM-^@M-^], M-bM-^@M-^\laddrM-bM-^@M-^], M-bM-^@M-^\lportM-bM-^@M-^], and
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M-bM-^@M-^\addrM-bM-^@M-^]. All are required and may be supplied in any order,
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either with multiple -C options or as a comma-separated list.
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-c host_certificate_file
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Specifies a path to a certificate file to identify sshd during
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key exchange. The certificate file must match a host key file
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specified using the -h option or the HostKey configuration
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directive.
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-D When this option is specified, sshd will not detach and does not
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become a daemon. This allows easy monitoring of sshd.
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-d Debug mode. The server sends verbose debug output to standard
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error, and does not put itself in the background. The server
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also will not fork and will only process one connection. This
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option is only intended for debugging for the server. Multiple
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-d options increase the debugging level. Maximum is 3.
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-E log_file
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Append debug logs to log_file instead of the system log.
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-e Write debug logs to standard error instead of the system log.
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-f config_file
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Specifies the name of the configuration file. The default is
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/etc/ssh/sshd_config. sshd refuses to start if there is no
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configuration file.
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-g login_grace_time
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Gives the grace time for clients to authenticate themselves
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(default 120 seconds). If the client fails to authenticate the
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user within this many seconds, the server disconnects and exits.
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A value of zero indicates no limit.
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-h host_key_file
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Specifies a file from which a host key is read. This option must
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be given if sshd is not run as root (as the normal host key files
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are normally not readable by anyone but root). The default is
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/etc/ssh/ssh_host_key for protocol version 1, and
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/etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_ecdsa_key.
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/etc/ssh/ssh_host_ed25519_key and /etc/ssh/ssh_host_rsa_key for
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protocol version 2. It is possible to have multiple host key
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files for the different protocol versions and host key
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algorithms.
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-i Specifies that sshd is being run from inetd(8). If SSH protocol
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1 is enabled, sshd should not normally be run from inetd because
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it needs to generate the server key before it can respond to the
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client, and this may take some time. Clients may have to wait
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too long if the key was regenerated every time.
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-k key_gen_time
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Specifies how often the ephemeral protocol version 1 server key
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is regenerated (default 3600 seconds, or one hour). The
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motivation for regenerating the key fairly often is that the key
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is not stored anywhere, and after about an hour it becomes
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impossible to recover the key for decrypting intercepted
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communications even if the machine is cracked into or physically
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seized. A value of zero indicates that the key will never be
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regenerated.
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-o option
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Can be used to give options in the format used in the
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configuration file. This is useful for specifying options for
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which there is no separate command-line flag. For full details
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of the options, and their values, see sshd_config(5).
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-p port
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Specifies the port on which the server listens for connections
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(default 22). Multiple port options are permitted. Ports
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specified in the configuration file with the Port option are
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ignored when a command-line port is specified. Ports specified
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using the ListenAddress option override command-line ports.
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-q Quiet mode. Nothing is sent to the system log. Normally the
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beginning, authentication, and termination of each connection is
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logged.
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-T Extended test mode. Check the validity of the configuration
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file, output the effective configuration to stdout and then exit.
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Optionally, Match rules may be applied by specifying the
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connection parameters using one or more -C options.
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-t Test mode. Only check the validity of the configuration file and
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sanity of the keys. This is useful for updating sshd reliably as
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configuration options may change.
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-u len This option is used to specify the size of the field in the utmp
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structure that holds the remote host name. If the resolved host
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name is longer than len, the dotted decimal value will be used
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instead. This allows hosts with very long host names that
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overflow this field to still be uniquely identified. Specifying
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-u0 indicates that only dotted decimal addresses should be put
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into the utmp file. -u0 may also be used to prevent sshd from
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making DNS requests unless the authentication mechanism or
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configuration requires it. Authentication mechanisms that may
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require DNS include RhostsRSAAuthentication,
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HostbasedAuthentication, and using a from="pattern-list" option
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in a key file. Configuration options that require DNS include
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using a USER@HOST pattern in AllowUsers or DenyUsers.
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AUTHENTICATION
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The OpenSSH SSH daemon supports SSH protocols 1 and 2. The default is to
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use protocol 2 only, though this can be changed via the Protocol option
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in sshd_config(5). Protocol 2 supports DSA, ECDSA, Ed25519 and RSA keys;
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protocol 1 only supports RSA keys. For both protocols, each host has a
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host-specific key, normally 2048 bits, used to identify the host.
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Forward security for protocol 1 is provided through an additional server
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key, normally 1024 bits, generated when the server starts. This key is
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normally regenerated every hour if it has been used, and is never stored
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on disk. Whenever a client connects, the daemon responds with its public
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host and server keys. The client compares the RSA host key against its
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own database to verify that it has not changed. The client then
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generates a 256-bit random number. It encrypts this random number using
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both the host key and the server key, and sends the encrypted number to
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the server. Both sides then use this random number as a session key
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which is used to encrypt all further communications in the session. The
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rest of the session is encrypted using a conventional cipher, currently
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Blowfish or 3DES, with 3DES being used by default. The client selects
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the encryption algorithm to use from those offered by the server.
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For protocol 2, forward security is provided through a Diffie-Hellman key
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agreement. This key agreement results in a shared session key. The rest
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of the session is encrypted using a symmetric cipher, currently 128-bit
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AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES. The
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client selects the encryption algorithm to use from those offered by the
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server. Additionally, session integrity is provided through a
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cryptographic message authentication code (hmac-md5, hmac-sha1, umac-64,
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umac-128, hmac-ripemd160, hmac-sha2-256 or hmac-sha2-512).
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Finally, the server and the client enter an authentication dialog. The
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client tries to authenticate itself using host-based authentication,
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public key authentication, challenge-response authentication, or password
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authentication.
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Regardless of the authentication type, the account is checked to ensure
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that it is accessible. An account is not accessible if it is locked,
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listed in DenyUsers or its group is listed in DenyGroups . The
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definition of a locked account is system dependant. Some platforms have
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their own account database (eg AIX) and some modify the passwd field (
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M-bM-^@M-^X*LK*M-bM-^@M-^Y on Solaris and UnixWare, M-bM-^@M-^X*M-bM-^@M-^Y on HP-UX, containing M-bM-^@M-^XNologinM-bM-^@M-^Y on
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Tru64, a leading M-bM-^@M-^X*LOCKED*M-bM-^@M-^Y on FreeBSD and a leading M-bM-^@M-^X!M-bM-^@M-^Y on most
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Linuxes). If there is a requirement to disable password authentication
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for the account while allowing still public-key, then the passwd field
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should be set to something other than these values (eg M-bM-^@M-^XNPM-bM-^@M-^Y or M-bM-^@M-^X*NP*M-bM-^@M-^Y ).
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If the client successfully authenticates itself, a dialog for preparing
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the session is entered. At this time the client may request things like
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allocating a pseudo-tty, forwarding X11 connections, forwarding TCP
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connections, or forwarding the authentication agent connection over the
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secure channel.
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After this, the client either requests a shell or execution of a command.
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The sides then enter session mode. In this mode, either side may send
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data at any time, and such data is forwarded to/from the shell or command
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on the server side, and the user terminal in the client side.
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When the user program terminates and all forwarded X11 and other
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connections have been closed, the server sends command exit status to the
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client, and both sides exit.
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LOGIN PROCESS
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When a user successfully logs in, sshd does the following:
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1. If the login is on a tty, and no command has been specified,
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prints last login time and /etc/motd (unless prevented in the
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configuration file or by ~/.hushlogin; see the FILES section).
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2. If the login is on a tty, records login time.
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3. Checks /etc/nologin; if it exists, prints contents and quits
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(unless root).
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4. Changes to run with normal user privileges.
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5. Sets up basic environment.
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6. Reads the file ~/.ssh/environment, if it exists, and users are
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allowed to change their environment. See the
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PermitUserEnvironment option in sshd_config(5).
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7. Changes to user's home directory.
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8. If ~/.ssh/rc exists and the sshd_config(5) PermitUserRC option
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is set, runs it; else if /etc/ssh/sshrc exists, runs it;
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otherwise runs xauth. The M-bM-^@M-^\rcM-bM-^@M-^] files are given the X11
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authentication protocol and cookie in standard input. See
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SSHRC, below.
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9. Runs user's shell or command. All commands are run under the
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user's login shell as specified in the system password
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database.
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SSHRC
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If the file ~/.ssh/rc exists, sh(1) runs it after reading the environment
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files but before starting the user's shell or command. It must not
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produce any output on stdout; stderr must be used instead. If X11
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forwarding is in use, it will receive the "proto cookie" pair in its
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standard input (and DISPLAY in its environment). The script must call
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xauth(1) because sshd will not run xauth automatically to add X11
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cookies.
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The primary purpose of this file is to run any initialization routines
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which may be needed before the user's home directory becomes accessible;
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AFS is a particular example of such an environment.
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This file will probably contain some initialization code followed by
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something similar to:
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if read proto cookie && [ -n "$DISPLAY" ]; then
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if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
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# X11UseLocalhost=yes
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echo add unix:`echo $DISPLAY |
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cut -c11-` $proto $cookie
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else
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# X11UseLocalhost=no
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echo add $DISPLAY $proto $cookie
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fi | xauth -q -
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fi
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If this file does not exist, /etc/ssh/sshrc is run, and if that does not
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exist either, xauth is used to add the cookie.
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AUTHORIZED_KEYS FILE FORMAT
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AuthorizedKeysFile specifies the files containing public keys for public
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key authentication; if none is specified, the default is
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~/.ssh/authorized_keys and ~/.ssh/authorized_keys2. Each line of the
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file contains one key (empty lines and lines starting with a M-bM-^@M-^X#M-bM-^@M-^Y are
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ignored as comments). Protocol 1 public keys consist of the following
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space-separated fields: options, bits, exponent, modulus, comment.
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Protocol 2 public key consist of: options, keytype, base64-encoded key,
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comment. The options field is optional; its presence is determined by
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whether the line starts with a number or not (the options field never
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starts with a number). The bits, exponent, modulus, and comment fields
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give the RSA key for protocol version 1; the comment field is not used
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for anything (but may be convenient for the user to identify the key).
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For protocol version 2 the keytype is M-bM-^@M-^\ecdsa-sha2-nistp256M-bM-^@M-^],
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M-bM-^@M-^\ecdsa-sha2-nistp384M-bM-^@M-^], M-bM-^@M-^\ecdsa-sha2-nistp521M-bM-^@M-^], M-bM-^@M-^\ssh-ed25519M-bM-^@M-^], M-bM-^@M-^\ssh-dssM-bM-^@M-^] or
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M-bM-^@M-^\ssh-rsaM-bM-^@M-^].
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Note that lines in this file are usually several hundred bytes long
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(because of the size of the public key encoding) up to a limit of 8
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kilobytes, which permits DSA keys up to 8 kilobits and RSA keys up to 16
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kilobits. You don't want to type them in; instead, copy the
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identity.pub, id_dsa.pub, id_ecdsa.pub, id_ed25519.pub, or the id_rsa.pub
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file and edit it.
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sshd enforces a minimum RSA key modulus size for protocol 1 and protocol
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2 keys of 768 bits.
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The options (if present) consist of comma-separated option
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specifications. No spaces are permitted, except within double quotes.
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The following option specifications are supported (note that option
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keywords are case-insensitive):
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cert-authority
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Specifies that the listed key is a certification authority (CA)
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that is trusted to validate signed certificates for user
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authentication.
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Certificates may encode access restrictions similar to these key
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options. If both certificate restrictions and key options are
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present, the most restrictive union of the two is applied.
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command="command"
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Specifies that the command is executed whenever this key is used
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for authentication. The command supplied by the user (if any) is
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ignored. The command is run on a pty if the client requests a
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pty; otherwise it is run without a tty. If an 8-bit clean
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channel is required, one must not request a pty or should specify
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no-pty. A quote may be included in the command by quoting it
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with a backslash. This option might be useful to restrict
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certain public keys to perform just a specific operation. An
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example might be a key that permits remote backups but nothing
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else. Note that the client may specify TCP and/or X11 forwarding
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unless they are explicitly prohibited. The command originally
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supplied by the client is available in the SSH_ORIGINAL_COMMAND
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environment variable. Note that this option applies to shell,
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command or subsystem execution. Also note that this command may
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be superseded by either a sshd_config(5) ForceCommand directive
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or a command embedded in a certificate.
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environment="NAME=value"
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Specifies that the string is to be added to the environment when
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logging in using this key. Environment variables set this way
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override other default environment values. Multiple options of
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this type are permitted. Environment processing is disabled by
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default and is controlled via the PermitUserEnvironment option.
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This option is automatically disabled if UseLogin is enabled.
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from="pattern-list"
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Specifies that in addition to public key authentication, either
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the canonical name of the remote host or its IP address must be
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present in the comma-separated list of patterns. See PATTERNS in
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ssh_config(5) for more information on patterns.
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In addition to the wildcard matching that may be applied to
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hostnames or addresses, a from stanza may match IP addresses
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using CIDR address/masklen notation.
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The purpose of this option is to optionally increase security:
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public key authentication by itself does not trust the network or
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name servers or anything (but the key); however, if somebody
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somehow steals the key, the key permits an intruder to log in
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from anywhere in the world. This additional option makes using a
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stolen key more difficult (name servers and/or routers would have
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to be compromised in addition to just the key).
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no-agent-forwarding
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Forbids authentication agent forwarding when this key is used for
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authentication.
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no-port-forwarding
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Forbids TCP forwarding when this key is used for authentication.
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Any port forward requests by the client will return an error.
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This might be used, e.g. in connection with the command option.
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no-pty Prevents tty allocation (a request to allocate a pty will fail).
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no-user-rc
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Disables execution of ~/.ssh/rc.
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no-X11-forwarding
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Forbids X11 forwarding when this key is used for authentication.
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Any X11 forward requests by the client will return an error.
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permitopen="host:port"
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Limit local port forwarding with ssh(1) -L such that it may only
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connect to the specified host and port. IPv6 addresses can be
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specified by enclosing the address in square brackets. Multiple
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permitopen options may be applied separated by commas. No
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pattern matching is performed on the specified hostnames, they
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must be literal domains or addresses. A port specification of *
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matches any port.
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principals="principals"
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On a cert-authority line, specifies allowed principals for
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certificate authentication as a comma-separated list. At least
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one name from the list must appear in the certificate's list of
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principals for the certificate to be accepted. This option is
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ignored for keys that are not marked as trusted certificate
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signers using the cert-authority option.
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tunnel="n"
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Force a tun(4) device on the server. Without this option, the
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next available device will be used if the client requests a
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tunnel.
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An example authorized_keys file:
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# Comments allowed at start of line
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ssh-rsa AAAAB3Nza...LiPk== user@example.net
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from="*.sales.example.net,!pc.sales.example.net" ssh-rsa
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AAAAB2...19Q== john@example.net
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command="dump /home",no-pty,no-port-forwarding ssh-dss
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AAAAC3...51R== example.net
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permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-dss
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AAAAB5...21S==
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tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...==
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jane@example.net
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SSH_KNOWN_HOSTS FILE FORMAT
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The /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts files contain host
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public keys for all known hosts. The global file should be prepared by
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the administrator (optional), and the per-user file is maintained
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automatically: whenever the user connects from an unknown host, its key
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is added to the per-user file.
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Each line in these files contains the following fields: markers
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(optional), hostnames, bits, exponent, modulus, comment. The fields are
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separated by spaces.
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The marker is optional, but if it is present then it must be one of
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M-bM-^@M-^\@cert-authorityM-bM-^@M-^], to indicate that the line contains a certification
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authority (CA) key, or M-bM-^@M-^\@revokedM-bM-^@M-^], to indicate that the key contained on
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the line is revoked and must not ever be accepted. Only one marker
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should be used on a key line.
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Hostnames is a comma-separated list of patterns (M-bM-^@M-^X*M-bM-^@M-^Y and M-bM-^@M-^X?M-bM-^@M-^Y act as
|
|
wildcards); each pattern in turn is matched against the canonical host
|
|
name (when authenticating a client) or against the user-supplied name
|
|
(when authenticating a server). A pattern may also be preceded by M-bM-^@M-^X!M-bM-^@M-^Y to
|
|
indicate negation: if the host name matches a negated pattern, it is not
|
|
accepted (by that line) even if it matched another pattern on the line.
|
|
A hostname or address may optionally be enclosed within M-bM-^@M-^X[M-bM-^@M-^Y and M-bM-^@M-^X]M-bM-^@M-^Y
|
|
brackets then followed by M-bM-^@M-^X:M-bM-^@M-^Y and a non-standard port number.
|
|
|
|
Alternately, hostnames may be stored in a hashed form which hides host
|
|
names and addresses should the file's contents be disclosed. Hashed
|
|
hostnames start with a M-bM-^@M-^X|M-bM-^@M-^Y character. Only one hashed hostname may
|
|
appear on a single line and none of the above negation or wildcard
|
|
operators may be applied.
|
|
|
|
Bits, exponent, and modulus are taken directly from the RSA host key;
|
|
they can be obtained, for example, from /etc/ssh/ssh_host_key.pub. The
|
|
optional comment field continues to the end of the line, and is not used.
|
|
|
|
Lines starting with M-bM-^@M-^X#M-bM-^@M-^Y and empty lines are ignored as comments.
|
|
|
|
When performing host authentication, authentication is accepted if any
|
|
matching line has the proper key; either one that matches exactly or, if
|
|
the server has presented a certificate for authentication, the key of the
|
|
certification authority that signed the certificate. For a key to be
|
|
trusted as a certification authority, it must use the M-bM-^@M-^\@cert-authorityM-bM-^@M-^]
|
|
marker described above.
|
|
|
|
The known hosts file also provides a facility to mark keys as revoked,
|
|
for example when it is known that the associated private key has been
|
|
stolen. Revoked keys are specified by including the M-bM-^@M-^\@revokedM-bM-^@M-^] marker at
|
|
the beginning of the key line, and are never accepted for authentication
|
|
or as certification authorities, but instead will produce a warning from
|
|
ssh(1) when they are encountered.
|
|
|
|
It is permissible (but not recommended) to have several lines or
|
|
different host keys for the same names. This will inevitably happen when
|
|
short forms of host names from different domains are put in the file. It
|
|
is possible that the files contain conflicting information;
|
|
authentication is accepted if valid information can be found from either
|
|
file.
|
|
|
|
Note that the lines in these files are typically hundreds of characters
|
|
long, and you definitely don't want to type in the host keys by hand.
|
|
Rather, generate them by a script, ssh-keyscan(1) or by taking
|
|
/etc/ssh/ssh_host_key.pub and adding the host names at the front.
|
|
ssh-keygen(1) also offers some basic automated editing for
|
|
~/.ssh/known_hosts including removing hosts matching a host name and
|
|
converting all host names to their hashed representations.
|
|
|
|
An example ssh_known_hosts file:
|
|
|
|
# Comments allowed at start of line
|
|
closenet,...,192.0.2.53 1024 37 159...93 closenet.example.net
|
|
cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....=
|
|
# A hashed hostname
|
|
|1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa
|
|
AAAA1234.....=
|
|
# A revoked key
|
|
@revoked * ssh-rsa AAAAB5W...
|
|
# A CA key, accepted for any host in *.mydomain.com or *.mydomain.org
|
|
@cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W...
|
|
|
|
FILES
|
|
~/.hushlogin
|
|
This file is used to suppress printing the last login time and
|
|
/etc/motd, if PrintLastLog and PrintMotd, respectively, are
|
|
enabled. It does not suppress printing of the banner specified
|
|
by Banner.
|
|
|
|
~/.rhosts
|
|
This file is used for host-based authentication (see ssh(1) for
|
|
more information). On some machines this file may need to be
|
|
world-readable if the user's home directory is on an NFS
|
|
partition, because sshd 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.
|
|
|
|
~/.shosts
|
|
This file is used in exactly the same way as .rhosts, but allows
|
|
host-based authentication without permitting login with
|
|
rlogin/rsh.
|
|
|
|
~/.ssh/
|
|
This directory is the default location for all user-specific
|
|
configuration and authentication information. There is no
|
|
general requirement to keep the entire contents of this directory
|
|
secret, but the recommended permissions are read/write/execute
|
|
for the user, and not accessible by others.
|
|
|
|
~/.ssh/authorized_keys
|
|
Lists the public keys (DSA, ECDSA, Ed25519, RSA) that can be used
|
|
for logging in as this user. The format of this file is
|
|
described above. The content of the file is not highly
|
|
sensitive, but the recommended permissions are read/write for the
|
|
user, and not accessible by others.
|
|
|
|
If this file, the ~/.ssh directory, or the user's home directory
|
|
are writable by other users, then the file could be modified or
|
|
replaced by unauthorized users. In this case, sshd will not
|
|
allow it to be used unless the StrictModes option has been set to
|
|
M-bM-^@M-^\noM-bM-^@M-^].
|
|
|
|
~/.ssh/environment
|
|
This file is read into the environment at login (if it exists).
|
|
It can only contain empty lines, comment lines (that start with
|
|
M-bM-^@M-^X#M-bM-^@M-^Y), and assignment lines of the form name=value. The file
|
|
should be writable only by the user; it need not be readable by
|
|
anyone else. Environment processing is disabled by default and
|
|
is controlled via the PermitUserEnvironment option.
|
|
|
|
~/.ssh/known_hosts
|
|
Contains a list of host keys for all hosts the user has logged
|
|
into that are not already in the systemwide list of known host
|
|
keys. The format of this file is described above. This file
|
|
should be writable only by root/the owner and can, but need not
|
|
be, world-readable.
|
|
|
|
~/.ssh/rc
|
|
Contains initialization routines to be run before the user's home
|
|
directory becomes accessible. This file should be writable only
|
|
by the user, and need not be readable by anyone else.
|
|
|
|
/etc/hosts.equiv
|
|
This file is for host-based authentication (see ssh(1)). It
|
|
should only be writable by root.
|
|
|
|
/etc/moduli
|
|
Contains Diffie-Hellman groups used for the "Diffie-Hellman Group
|
|
Exchange". The file format is described in moduli(5).
|
|
|
|
/etc/motd
|
|
See motd(5).
|
|
|
|
/etc/nologin
|
|
If this file exists, sshd refuses to let anyone except root log
|
|
in. The contents of the file are displayed to anyone trying to
|
|
log in, and non-root connections are refused. The file should be
|
|
world-readable.
|
|
|
|
/etc/shosts.equiv
|
|
This file is used in exactly the same way as hosts.equiv, but
|
|
allows host-based authentication without permitting login with
|
|
rlogin/rsh.
|
|
|
|
/etc/ssh/ssh_host_key
|
|
/etc/ssh/ssh_host_dsa_key
|
|
/etc/ssh/ssh_host_ecdsa_key
|
|
/etc/ssh/ssh_host_ed25519_key
|
|
/etc/ssh/ssh_host_rsa_key
|
|
These files contain the private parts of the host keys. These
|
|
files should only be owned by root, readable only by root, and
|
|
not accessible to others. Note that sshd does not start if these
|
|
files are group/world-accessible.
|
|
|
|
/etc/ssh/ssh_host_key.pub
|
|
/etc/ssh/ssh_host_dsa_key.pub
|
|
/etc/ssh/ssh_host_ecdsa_key.pub
|
|
/etc/ssh/ssh_host_ed25519_key.pub
|
|
/etc/ssh/ssh_host_rsa_key.pub
|
|
These files contain the public parts of the host keys. These
|
|
files should be world-readable but writable only by root. Their
|
|
contents should match the respective private parts. These files
|
|
are not really used for anything; they are provided for the
|
|
convenience of the user so their contents can be copied to known
|
|
hosts files. These files are created using ssh-keygen(1).
|
|
|
|
/etc/ssh/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. The format of this file is
|
|
described above. This file should be writable only by root/the
|
|
owner and should be world-readable.
|
|
|
|
/etc/ssh/sshd_config
|
|
Contains configuration data for sshd. The file format and
|
|
configuration options are described in sshd_config(5).
|
|
|
|
/etc/ssh/sshrc
|
|
Similar to ~/.ssh/rc, it can be used to specify machine-specific
|
|
login-time initializations globally. This file should be
|
|
writable only by root, and should be world-readable.
|
|
|
|
/var/empty
|
|
chroot(2) directory used by sshd during privilege separation in
|
|
the pre-authentication phase. The directory should not contain
|
|
any files and must be owned by root and not group or world-
|
|
writable.
|
|
|
|
/var/run/sshd.pid
|
|
Contains the process ID of the sshd listening for connections (if
|
|
there are several daemons running concurrently for different
|
|
ports, this contains the process ID of the one started last).
|
|
The content of this file is not sensitive; it can be world-
|
|
readable.
|
|
|
|
SEE ALSO
|
|
scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1),
|
|
ssh-keyscan(1), chroot(2), login.conf(5), moduli(5), sshd_config(5),
|
|
inetd(8), sftp-server(8)
|
|
|
|
AUTHORS
|
|
OpenSSH is a derivative of the original and free ssh 1.2.12 release by
|
|
Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
|
|
de Raadt and Dug Song removed many bugs, re-added newer features and
|
|
created OpenSSH. Markus Friedl contributed the support for SSH protocol
|
|
versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support
|
|
for privilege separation.
|
|
|
|
OpenBSD 5.8 July 3, 2015 OpenBSD 5.8
|