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diff --git a/crypto/openssh/sshd_config.0 b/crypto/openssh/sshd_config.0 deleted file mode 100644 index 413c260..0000000 --- a/crypto/openssh/sshd_config.0 +++ /dev/null @@ -1,835 +0,0 @@ -SSHD_CONFIG(5) OpenBSD Programmer's Manual SSHD_CONFIG(5) - -NAME - sshd_config - OpenSSH SSH daemon configuration file - -SYNOPSIS - /etc/ssh/sshd_config - -DESCRIPTION - sshd(8) reads configuration data from /etc/ssh/sshd_config (or the file - specified with -f on the command line). The file contains keyword- - argument pairs, one per line. Lines starting with `#' and empty lines - are interpreted as comments. Arguments may optionally be enclosed in - double quotes (") in order to represent arguments containing spaces. - - The possible keywords and their meanings are as follows (note that - keywords are case-insensitive and arguments are case-sensitive): - - AcceptEnv - Specifies what environment variables sent by the client will be - copied into the session's environ(7). See SendEnv in - ssh_config(5) for how to configure the client. Note that - environment passing is only supported for protocol 2. Variables - are specified by name, which may contain the wildcard characters - `*' and `?'. Multiple environment variables may be separated by - whitespace or spread across multiple AcceptEnv directives. Be - warned that some environment variables could be used to bypass - restricted user environments. For this reason, care should be - taken in the use of this directive. The default is not to accept - any environment variables. - - AddressFamily - Specifies which address family should be used by sshd(8). Valid - arguments are ``any'', ``inet'' (use IPv4 only), or ``inet6'' - (use IPv6 only). The default is ``any''. - - AllowAgentForwarding - Specifies whether ssh-agent(1) forwarding is permitted. The - default is ``yes''. Note that disabling agent forwarding does - not improve security unless users are also denied shell access, - as they can always install their own forwarders. - - AllowGroups - This keyword can be followed by a list of group name patterns, - separated by spaces. If specified, login is allowed only for - users whose primary group or supplementary group list matches one - of the patterns. Only group names are valid; a numerical group - ID is not recognized. By default, login is allowed for all - groups. The allow/deny directives are processed in the following - order: DenyUsers, AllowUsers, DenyGroups, and finally - AllowGroups. - - See PATTERNS in ssh_config(5) for more information on patterns. - - AllowTcpForwarding - Specifies whether TCP forwarding is permitted. The available - options are ``yes'' or ``all'' to allow TCP forwarding, ``no'' to - prevent all TCP forwarding, ``local'' to allow local (from the - perspective of ssh(1)) forwarding only or ``remote'' to allow - remote forwarding only. The default is ``yes''. Note that - disabling TCP forwarding does not improve security unless users - are also denied shell access, as they can always install their - own forwarders. - - AllowUsers - This keyword can be followed by a list of user name patterns, - separated by spaces. If specified, login is allowed only for - user names that match one of the patterns. Only user names are - valid; a numerical user ID is not recognized. By default, login - is allowed for all users. If the pattern takes the form - USER@HOST then USER and HOST are separately checked, restricting - logins to particular users from particular hosts. The allow/deny - directives are processed in the following order: DenyUsers, - AllowUsers, DenyGroups, and finally AllowGroups. - - See PATTERNS in ssh_config(5) for more information on patterns. - - AuthenticationMethods - Specifies the authentication methods that must be successfully - completed for a user to be granted access. This option must be - followed by one or more comma-separated lists of authentication - method names. Successful authentication requires completion of - every method in at least one of these lists. - - For example, an argument of ``publickey,password - publickey,keyboard-interactive'' would require the user to - complete public key authentication, followed by either password - or keyboard interactive authentication. Only methods that are - next in one or more lists are offered at each stage, so for this - example, it would not be possible to attempt password or - keyboard-interactive authentication before public key. - - For keyboard interactive authentication it is also possible to - restrict authentication to a specific device by appending a colon - followed by the device identifier ``bsdauth'', ``pam'', or - ``skey'', depending on the server configuration. For example, - ``keyboard-interactive:bsdauth'' would restrict keyboard - interactive authentication to the ``bsdauth'' device. - - This option is only available for SSH protocol 2 and will yield a - fatal error if enabled if protocol 1 is also enabled. Note that - each authentication method listed should also be explicitly - enabled in the configuration. The default is not to require - multiple authentication; successful completion of a single - authentication method is sufficient. - - AuthorizedKeysCommand - Specifies a program to be used to look up the user's public keys. - The program must be owned by root and not writable by group or - others. It will be invoked with a single argument of the - username being authenticated, and should produce on standard - output zero or more lines of authorized_keys output (see - AUTHORIZED_KEYS in sshd(8)). If a key supplied by - AuthorizedKeysCommand does not successfully authenticate and - authorize the user then public key authentication continues using - the usual AuthorizedKeysFile files. By default, no - AuthorizedKeysCommand is run. - - AuthorizedKeysCommandUser - Specifies the user under whose account the AuthorizedKeysCommand - is run. It is recommended to use a dedicated user that has no - other role on the host than running authorized keys commands. - - AuthorizedKeysFile - Specifies the file that contains the public keys that can be used - for user authentication. The format is described in the - AUTHORIZED_KEYS FILE FORMAT section of sshd(8). - AuthorizedKeysFile may contain tokens of the form %T which are - substituted during connection setup. The following tokens are - defined: %% is replaced by a literal '%', %h is replaced by the - home directory of the user being authenticated, and %u is - replaced by the username of that user. After expansion, - AuthorizedKeysFile is taken to be an absolute path or one - relative to the user's home directory. Multiple files may be - listed, separated by whitespace. The default is - ``.ssh/authorized_keys .ssh/authorized_keys2''. - - AuthorizedPrincipalsFile - Specifies a file that lists principal names that are accepted for - certificate authentication. When using certificates signed by a - key listed in TrustedUserCAKeys, this file lists names, one of - which must appear in the certificate for it to be accepted for - authentication. Names are listed one per line preceded by key - options (as described in AUTHORIZED_KEYS FILE FORMAT in sshd(8)). - Empty lines and comments starting with `#' are ignored. - - AuthorizedPrincipalsFile may contain tokens of the form %T which - are substituted during connection setup. The following tokens - are defined: %% is replaced by a literal '%', %h is replaced by - the home directory of the user being authenticated, and %u is - replaced by the username of that user. After expansion, - AuthorizedPrincipalsFile is taken to be an absolute path or one - relative to the user's home directory. - - The default is ``none'', i.e. not to use a principals file - in - this case, the username of the user must appear in a - certificate's principals list for it to be accepted. Note that - AuthorizedPrincipalsFile is only used when authentication - proceeds using a CA listed in TrustedUserCAKeys and is not - consulted for certification authorities trusted via - ~/.ssh/authorized_keys, though the principals= key option offers - a similar facility (see sshd(8) for details). - - Banner The contents of the specified file are sent to the remote user - before authentication is allowed. If the argument is ``none'' - then no banner is displayed. This option is only available for - protocol version 2. By default, no banner is displayed. - - ChallengeResponseAuthentication - Specifies whether challenge-response authentication is allowed - (e.g. via PAM or though authentication styles supported in - login.conf(5)) The default is ``yes''. - - ChrootDirectory - Specifies the pathname of a directory to chroot(2) to after - authentication. All components of the pathname must be root- - owned directories that are not writable by any other user or - group. After the chroot, sshd(8) changes the working directory - to the user's home directory. - - The pathname may contain the following tokens that are expanded - at runtime once the connecting user has been authenticated: %% is - replaced by a literal '%', %h is replaced by the home directory - of the user being authenticated, and %u is replaced by the - username of that user. - - The ChrootDirectory must contain the necessary files and - directories to support the user's session. For an interactive - session this requires at least a shell, typically sh(1), and - basic /dev nodes such as null(4), zero(4), stdin(4), stdout(4), - stderr(4), arandom(4) and tty(4) devices. For file transfer - sessions using ``sftp'', no additional configuration of the - environment is necessary if the in-process sftp server is used, - though sessions which use logging do require /dev/log inside the - chroot directory (see sftp-server(8) for details). - - The default is not to chroot(2). - - Ciphers - Specifies the ciphers allowed for protocol version 2. Multiple - ciphers must be comma-separated. The supported ciphers are: - - ``3des-cbc'', ``aes128-cbc'', ``aes192-cbc'', ``aes256-cbc'', - ``aes128-ctr'', ``aes192-ctr'', ``aes256-ctr'', - ``aes128-gcm@openssh.com'', ``aes256-gcm@openssh.com'', - ``arcfour128'', ``arcfour256'', ``arcfour'', ``blowfish-cbc'', - ``cast128-cbc'', and ``chacha20-poly1305@openssh.com''. - - The default is: - - aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128, - aes128-gcm@openssh.com,aes256-gcm@openssh.com, - chacha20-poly1305@openssh.com, - aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc, - aes256-cbc,arcfour - - The list of available ciphers may also be obtained using the -Q - option of ssh(1). - - ClientAliveCountMax - Sets the number of client alive messages (see below) which may be - sent without sshd(8) receiving any messages back from the client. - If this threshold is reached while client alive messages are - being sent, sshd will disconnect the client, terminating the - session. It is important to note that the use of client alive - messages is very different from TCPKeepAlive (below). The client - alive messages are sent through the encrypted channel and - therefore will not be spoofable. The TCP keepalive option - enabled by TCPKeepAlive is spoofable. The client alive mechanism - is valuable when the client or server depend on knowing when a - connection has become inactive. - - The default value is 3. If ClientAliveInterval (see below) is - set to 15, and ClientAliveCountMax is left at the default, - unresponsive SSH clients will be disconnected after approximately - 45 seconds. This option applies to protocol version 2 only. - - ClientAliveInterval - Sets a timeout interval in seconds after which if no data has - been received from the client, sshd(8) will send a message - through the encrypted channel to request a response from the - client. The default is 0, indicating that these messages will - not be sent to the client. This option applies to protocol - version 2 only. - - Compression - Specifies whether compression is allowed, or delayed until the - user has authenticated successfully. The argument must be - ``yes'', ``delayed'', or ``no''. The default is ``delayed''. - - DenyGroups - This keyword can be followed by a list of group name patterns, - separated by spaces. Login is disallowed for users whose primary - group or supplementary group list matches one of the patterns. - Only group names are valid; a numerical group ID is not - recognized. By default, login is allowed for all groups. The - allow/deny directives are processed in the following order: - DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups. - - See PATTERNS in ssh_config(5) for more information on patterns. - - DenyUsers - This keyword can be followed by a list of user name patterns, - separated by spaces. Login is disallowed for user names that - match one of the patterns. Only user names are valid; a - numerical user ID is not recognized. By default, login is - allowed for all users. If the pattern takes the form USER@HOST - then USER and HOST are separately checked, restricting logins to - particular users from particular hosts. The allow/deny - directives are processed in the following order: DenyUsers, - AllowUsers, DenyGroups, and finally AllowGroups. - - See PATTERNS in ssh_config(5) for more information on patterns. - - ForceCommand - Forces the execution of the command specified by ForceCommand, - ignoring any command supplied by the client and ~/.ssh/rc if - present. The command is invoked by using the user's login shell - with the -c option. This applies to shell, command, or subsystem - execution. It is most useful inside a Match block. The command - originally supplied by the client is available in the - SSH_ORIGINAL_COMMAND environment variable. Specifying a command - of ``internal-sftp'' will force the use of an in-process sftp - server that requires no support files when used with - ChrootDirectory. - - GatewayPorts - Specifies whether remote hosts are allowed to connect to ports - forwarded for the client. By default, sshd(8) binds remote port - forwardings to the loopback address. This prevents other remote - hosts from connecting to forwarded ports. GatewayPorts can be - used to specify that sshd should allow remote port forwardings to - bind to non-loopback addresses, thus allowing other hosts to - connect. The argument may be ``no'' to force remote port - forwardings to be available to the local host only, ``yes'' to - force remote port forwardings to bind to the wildcard address, or - ``clientspecified'' to allow the client to select the address to - which the forwarding is bound. The default is ``no''. - - GSSAPIAuthentication - Specifies whether user authentication based on GSSAPI is allowed. - The default is ``no''. Note that this option applies to protocol - version 2 only. - - GSSAPICleanupCredentials - Specifies whether to automatically destroy the user's credentials - cache on logout. The default is ``yes''. Note that this option - applies to protocol version 2 only. - - HostbasedAuthentication - Specifies whether rhosts or /etc/hosts.equiv authentication - together with successful public key client host authentication is - allowed (host-based authentication). This option is similar to - RhostsRSAAuthentication and applies to protocol version 2 only. - The default is ``no''. - - HostbasedUsesNameFromPacketOnly - Specifies whether or not the server will attempt to perform a - reverse name lookup when matching the name in the ~/.shosts, - ~/.rhosts, and /etc/hosts.equiv files during - HostbasedAuthentication. A setting of ``yes'' means that sshd(8) - uses the name supplied by the client rather than attempting to - resolve the name from the TCP connection itself. The default is - ``no''. - - HostCertificate - Specifies a file containing a public host certificate. The - certificate's public key must match a private host key already - specified by HostKey. The default behaviour of sshd(8) is not to - load any certificates. - - HostKey - Specifies a file containing a private host key used by SSH. The - default is /etc/ssh/ssh_host_key for protocol version 1, and - /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_ecdsa_key, - /etc/ssh/ssh_host_ed25519_key and /etc/ssh/ssh_host_rsa_key for - protocol version 2. Note that sshd(8) will refuse to use a file - if it is group/world-accessible. It is possible to have multiple - host key files. ``rsa1'' keys are used for version 1 and - ``dsa'', ``ecdsa'', ``ed25519'' or ``rsa'' are used for version 2 - of the SSH protocol. It is also possible to specify public host - key files instead. In this case operations on the private key - will be delegated to an ssh-agent(1). - - HostKeyAgent - Identifies the UNIX-domain socket used to communicate with an - agent that has access to the private host keys. If - ``SSH_AUTH_SOCK'' is specified, the location of the socket will - be read from the SSH_AUTH_SOCK environment variable. - - IgnoreRhosts - Specifies that .rhosts and .shosts files will not be used in - RhostsRSAAuthentication or HostbasedAuthentication. - - /etc/hosts.equiv and /etc/shosts.equiv are still used. The - default is ``yes''. - - IgnoreUserKnownHosts - Specifies whether sshd(8) should ignore the user's - ~/.ssh/known_hosts during RhostsRSAAuthentication or - HostbasedAuthentication. The default is ``no''. - - IPQoS Specifies the IPv4 type-of-service or DSCP class for the - connection. Accepted values are ``af11'', ``af12'', ``af13'', - ``af21'', ``af22'', ``af23'', ``af31'', ``af32'', ``af33'', - ``af41'', ``af42'', ``af43'', ``cs0'', ``cs1'', ``cs2'', ``cs3'', - ``cs4'', ``cs5'', ``cs6'', ``cs7'', ``ef'', ``lowdelay'', - ``throughput'', ``reliability'', or a numeric value. This option - may take one or two arguments, separated by whitespace. If one - argument is specified, it is used as the packet class - unconditionally. If two values are specified, the first is - automatically selected for interactive sessions and the second - for non-interactive sessions. The default is ``lowdelay'' for - interactive sessions and ``throughput'' for non-interactive - sessions. - - KbdInteractiveAuthentication - Specifies whether to allow keyboard-interactive authentication. - The argument to this keyword must be ``yes'' or ``no''. The - default is to use whatever value ChallengeResponseAuthentication - is set to (by default ``yes''). - - KerberosAuthentication - Specifies whether the password provided by the user for - PasswordAuthentication will be validated through the Kerberos - KDC. To use this option, the server needs a Kerberos servtab - which allows the verification of the KDC's identity. The default - is ``no''. - - KerberosGetAFSToken - If AFS is active and the user has a Kerberos 5 TGT, attempt to - acquire an AFS token before accessing the user's home directory. - The default is ``no''. - - KerberosOrLocalPasswd - If password authentication through Kerberos fails then the - password will be validated via any additional local mechanism - such as /etc/passwd. The default is ``yes''. - - KerberosTicketCleanup - Specifies whether to automatically destroy the user's ticket - cache file on logout. The default is ``yes''. - - KexAlgorithms - Specifies the available KEX (Key Exchange) algorithms. Multiple - algorithms must be comma-separated. The default is - - curve25519-sha256@libssh.org, - ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521, - diffie-hellman-group-exchange-sha256, - diffie-hellman-group-exchange-sha1, - diffie-hellman-group14-sha1, - diffie-hellman-group1-sha1 - - KeyRegenerationInterval - In protocol version 1, the ephemeral server key is automatically - regenerated after this many seconds (if it has been used). The - purpose of regeneration is to prevent decrypting captured - sessions by later breaking into the machine and stealing the - keys. The key is never stored anywhere. If the value is 0, the - key is never regenerated. The default is 3600 (seconds). - - ListenAddress - Specifies the local addresses sshd(8) should listen on. The - following forms may be used: - - ListenAddress host|IPv4_addr|IPv6_addr - ListenAddress host|IPv4_addr:port - ListenAddress [host|IPv6_addr]:port - - If port is not specified, sshd will listen on the address and all - prior Port options specified. The default is to listen on all - local addresses. Multiple ListenAddress options are permitted. - Additionally, any Port options must precede this option for non- - port qualified addresses. - - LoginGraceTime - The server disconnects after this time if the user has not - successfully logged in. If the value is 0, there is no time - limit. The default is 120 seconds. - - LogLevel - Gives the verbosity level that is used when logging messages from - sshd(8). The possible values are: QUIET, FATAL, ERROR, INFO, - VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. - DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify - higher levels of debugging output. Logging with a DEBUG level - violates the privacy of users and is not recommended. - - MACs Specifies the available MAC (message authentication code) - algorithms. The MAC algorithm is used in protocol version 2 for - data integrity protection. Multiple algorithms must be comma- - separated. The algorithms that contain ``-etm'' calculate the - MAC after encryption (encrypt-then-mac). These are considered - safer and their use recommended. The default is: - - hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com, - umac-64-etm@openssh.com,umac-128-etm@openssh.com, - hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com, - hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com, - hmac-md5-96-etm@openssh.com, - hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com, - hmac-sha2-256,hmac-sha2-512,hmac-ripemd160, - hmac-sha1-96,hmac-md5-96 - - Match Introduces a conditional block. If all of the criteria on the - Match line are satisfied, the keywords on the following lines - override those set in the global section of the config file, - until either another Match line or the end of the file. If a - keyword appears in multiple Match blocks that are satisified, - only the first instance of the keyword is applied. - - The arguments to Match are one or more criteria-pattern pairs or - the single token All which matches all criteria. The available - criteria are User, Group, Host, LocalAddress, LocalPort, and - Address. The match patterns may consist of single entries or - comma-separated lists and may use the wildcard and negation - operators described in the PATTERNS section of ssh_config(5). - - The patterns in an Address criteria may additionally contain - addresses to match in CIDR address/masklen format, e.g. - ``192.0.2.0/24'' or ``3ffe:ffff::/32''. Note that the mask - length provided must be consistent with the address - it is an - error to specify a mask length that is too long for the address - or one with bits set in this host portion of the address. For - example, ``192.0.2.0/33'' and ``192.0.2.0/8'' respectively. - - Only a subset of keywords may be used on the lines following a - Match keyword. Available keywords are AcceptEnv, - AllowAgentForwarding, AllowGroups, AllowTcpForwarding, - AllowUsers, AuthenticationMethods, AuthorizedKeysCommand, - AuthorizedKeysCommandUser, AuthorizedKeysFile, - AuthorizedPrincipalsFile, Banner, ChrootDirectory, DenyGroups, - DenyUsers, ForceCommand, GatewayPorts, GSSAPIAuthentication, - HostbasedAuthentication, HostbasedUsesNameFromPacketOnly, - KbdInteractiveAuthentication, KerberosAuthentication, - MaxAuthTries, MaxSessions, PasswordAuthentication, - PermitEmptyPasswords, PermitOpen, PermitRootLogin, PermitTTY, - PermitTunnel, PubkeyAuthentication, RekeyLimit, - RhostsRSAAuthentication, RSAAuthentication, X11DisplayOffset, - X11Forwarding and X11UseLocalHost. - - MaxAuthTries - Specifies the maximum number of authentication attempts permitted - per connection. Once the number of failures reaches half this - value, additional failures are logged. The default is 6. - - MaxSessions - Specifies the maximum number of open sessions permitted per - network connection. The default is 10. - - MaxStartups - Specifies the maximum number of concurrent unauthenticated - connections to the SSH daemon. Additional connections will be - dropped until authentication succeeds or the LoginGraceTime - expires for a connection. The default is 10:30:100. - - Alternatively, random early drop can be enabled by specifying the - three colon separated values ``start:rate:full'' (e.g. - "10:30:60"). sshd(8) will refuse connection attempts with a - probability of ``rate/100'' (30%) if there are currently - ``start'' (10) unauthenticated connections. The probability - increases linearly and all connection attempts are refused if the - number of unauthenticated connections reaches ``full'' (60). - - PasswordAuthentication - Specifies whether password authentication is allowed. The - default is ``yes''. - - PermitEmptyPasswords - When password authentication is allowed, it specifies whether the - server allows login to accounts with empty password strings. The - default is ``no''. - - PermitOpen - Specifies the destinations to which TCP port forwarding is - permitted. The forwarding specification must be one of the - following forms: - - PermitOpen host:port - PermitOpen IPv4_addr:port - PermitOpen [IPv6_addr]:port - - Multiple forwards may be specified by separating them with - whitespace. An argument of ``any'' can be used to remove all - restrictions and permit any forwarding requests. An argument of - ``none'' can be used to prohibit all forwarding requests. By - default all port forwarding requests are permitted. - - PermitRootLogin - Specifies whether root can log in using ssh(1). The argument - must be ``yes'', ``without-password'', ``forced-commands-only'', - or ``no''. The default is ``yes''. - - If this option is set to ``without-password'', password - authentication is disabled for root. - - If this option is set to ``forced-commands-only'', root login - with public key authentication will be allowed, but only if the - command option has been specified (which may be useful for taking - remote backups even if root login is normally not allowed). All - other authentication methods are disabled for root. - - If this option is set to ``no'', root is not allowed to log in. - - PermitTunnel - Specifies whether tun(4) device forwarding is allowed. The - argument must be ``yes'', ``point-to-point'' (layer 3), - ``ethernet'' (layer 2), or ``no''. Specifying ``yes'' permits - both ``point-to-point'' and ``ethernet''. The default is ``no''. - - PermitTTY - Specifies whether pty(4) allocation is permitted. The default is - ``yes''. - - PermitUserEnvironment - Specifies whether ~/.ssh/environment and environment= options in - ~/.ssh/authorized_keys are processed by sshd(8). The default is - ``no''. Enabling environment processing may enable users to - bypass access restrictions in some configurations using - mechanisms such as LD_PRELOAD. - - PidFile - Specifies the file that contains the process ID of the SSH - daemon. The default is /var/run/sshd.pid. - - Port Specifies the port number that sshd(8) listens on. The default - is 22. Multiple options of this type are permitted. See also - ListenAddress. - - PrintLastLog - Specifies whether sshd(8) should print the date and time of the - last user login when a user logs in interactively. The default - is ``yes''. - - PrintMotd - Specifies whether sshd(8) should print /etc/motd when a user logs - in interactively. (On some systems it is also printed by the - shell, /etc/profile, or equivalent.) The default is ``yes''. - - Protocol - Specifies the protocol versions sshd(8) supports. The possible - values are `1' and `2'. Multiple versions must be comma- - separated. The default is `2'. Note that the order of the - protocol list does not indicate preference, because the client - selects among multiple protocol versions offered by the server. - Specifying ``2,1'' is identical to ``1,2''. - - PubkeyAuthentication - Specifies whether public key authentication is allowed. The - default is ``yes''. Note that this option applies to protocol - version 2 only. - - RekeyLimit - Specifies the maximum amount of data that may be transmitted - before the session key is renegotiated, optionally followed a - maximum amount of time that may pass before the session key is - renegotiated. The first argument is specified in bytes and may - have a suffix of `K', `M', or `G' to indicate Kilobytes, - Megabytes, or Gigabytes, respectively. The default is between - `1G' and `4G', depending on the cipher. The optional second - value is specified in seconds and may use any of the units - documented in the TIME FORMATS section. The default value for - RekeyLimit is ``default none'', which means that rekeying is - performed after the cipher's default amount of data has been sent - or received and no time based rekeying is done. This option - applies to protocol version 2 only. - - RevokedKeys - Specifies revoked public keys. Keys listed in this file will be - refused for public key authentication. Note that if this file is - not readable, then public key authentication will be refused for - all users. Keys may be specified as a text file, listing one - public key per line, or as an OpenSSH Key Revocation List (KRL) - as generated by ssh-keygen(1). For more information on KRLs, see - the KEY REVOCATION LISTS section in ssh-keygen(1). - - RhostsRSAAuthentication - Specifies whether rhosts or /etc/hosts.equiv authentication - together with successful RSA host authentication is allowed. The - default is ``no''. This option applies to protocol version 1 - only. - - RSAAuthentication - Specifies whether pure RSA authentication is allowed. The - default is ``yes''. This option applies to protocol version 1 - only. - - ServerKeyBits - Defines the number of bits in the ephemeral protocol version 1 - server key. The minimum value is 512, and the default is 1024. - - StrictModes - Specifies whether sshd(8) should check file modes and ownership - of the user's files and home directory before accepting login. - This is normally desirable because novices sometimes accidentally - leave their directory or files world-writable. The default is - ``yes''. Note that this does not apply to ChrootDirectory, whose - permissions and ownership are checked unconditionally. - - Subsystem - Configures an external subsystem (e.g. file transfer daemon). - Arguments should be a subsystem name and a command (with optional - arguments) to execute upon subsystem request. - - The command sftp-server(8) implements the ``sftp'' file transfer - subsystem. - - Alternately the name ``internal-sftp'' implements an in-process - ``sftp'' server. This may simplify configurations using - ChrootDirectory to force a different filesystem root on clients. - - By default no subsystems are defined. Note that this option - applies to protocol version 2 only. - - SyslogFacility - Gives the facility code that is used when logging messages from - sshd(8). The possible values are: DAEMON, USER, AUTH, LOCAL0, - LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The - default is AUTH. - - TCPKeepAlive - Specifies whether the system should send TCP keepalive messages - to the other side. If they are sent, death of the connection or - crash of one of the machines will be properly noticed. However, - this means that connections will die if the route is down - temporarily, and some people find it annoying. On the other - hand, if TCP keepalives are not sent, sessions may hang - indefinitely on the server, leaving ``ghost'' users and consuming - server resources. - - The default is ``yes'' (to send TCP keepalive messages), and the - server will notice if the network goes down or the client host - crashes. This avoids infinitely hanging sessions. - - To disable TCP keepalive messages, the value should be set to - ``no''. - - TrustedUserCAKeys - Specifies a file containing public keys of certificate - authorities that are trusted to sign user certificates for - authentication. Keys are listed one per line; empty lines and - comments starting with `#' are allowed. If a certificate is - presented for authentication and has its signing CA key listed in - this file, then it may be used for authentication for any user - listed in the certificate's principals list. Note that - certificates that lack a list of principals will not be permitted - for authentication using TrustedUserCAKeys. For more details on - certificates, see the CERTIFICATES section in ssh-keygen(1). - - UseDNS Specifies whether sshd(8) should look up the remote host name and - check that the resolved host name for the remote IP address maps - back to the very same IP address. The default is ``yes''. - - UseLogin - Specifies whether login(1) is used for interactive login - sessions. The default is ``no''. Note that login(1) is never - used for remote command execution. Note also, that if this is - enabled, X11Forwarding will be disabled because login(1) does not - know how to handle xauth(1) cookies. If UsePrivilegeSeparation - is specified, it will be disabled after authentication. - - UsePAM Enables the Pluggable Authentication Module interface. If set to - ``yes'' this will enable PAM authentication using - ChallengeResponseAuthentication and PasswordAuthentication in - addition to PAM account and session module processing for all - authentication types. - - Because PAM challenge-response authentication usually serves an - equivalent role to password authentication, you should disable - either PasswordAuthentication or ChallengeResponseAuthentication. - - If UsePAM is enabled, you will not be able to run sshd(8) as a - non-root user. The default is ``no''. - - UsePrivilegeSeparation - Specifies whether sshd(8) separates privileges by creating an - unprivileged child process to deal with incoming network traffic. - After successful authentication, another process will be created - that has the privilege of the authenticated user. The goal of - privilege separation is to prevent privilege escalation by - containing any corruption within the unprivileged processes. The - default is ``yes''. If UsePrivilegeSeparation is set to - ``sandbox'' then the pre-authentication unprivileged process is - subject to additional restrictions. - - VersionAddendum - Optionally specifies additional text to append to the SSH - protocol banner sent by the server upon connection. The default - is ``none''. - - X11DisplayOffset - Specifies the first display number available for sshd(8)'s X11 - forwarding. This prevents sshd from interfering with real X11 - servers. The default is 10. - - X11Forwarding - Specifies whether X11 forwarding is permitted. The argument must - be ``yes'' or ``no''. The default is ``no''. - - When X11 forwarding is enabled, there may be additional exposure - to the server and to client displays if the sshd(8) proxy display - is configured to listen on the wildcard address (see - X11UseLocalhost below), though this is not the default. - Additionally, the authentication spoofing and authentication data - verification and substitution occur on the client side. The - security risk of using X11 forwarding is that the client's X11 - display server may be exposed to attack when the SSH client - requests forwarding (see the warnings for ForwardX11 in - ssh_config(5)). A system administrator may have a stance in - which they want to protect clients that may expose themselves to - attack by unwittingly requesting X11 forwarding, which can - warrant a ``no'' setting. - - Note that disabling X11 forwarding does not prevent users from - forwarding X11 traffic, as users can always install their own - forwarders. X11 forwarding is automatically disabled if UseLogin - is enabled. - - X11UseLocalhost - Specifies whether sshd(8) should bind the X11 forwarding server - to the loopback address or to the wildcard address. By default, - sshd binds the forwarding server to the loopback address and sets - the hostname part of the DISPLAY environment variable to - ``localhost''. This prevents remote hosts from connecting to the - proxy display. However, some older X11 clients may not function - with this configuration. X11UseLocalhost may be set to ``no'' to - specify that the forwarding server should be bound to the - wildcard address. The argument must be ``yes'' or ``no''. The - default is ``yes''. - - XAuthLocation - Specifies the full pathname of the xauth(1) program. The default - is /usr/X11R6/bin/xauth. - -TIME FORMATS - sshd(8) command-line arguments and configuration file options that - specify time may be expressed using a sequence of the form: - time[qualifier], where time is a positive integer value and qualifier is - one of the following: - - <none> seconds - s | S seconds - m | M minutes - h | H hours - d | D days - w | W weeks - - Each member of the sequence is added together to calculate the total time - value. - - Time format examples: - - 600 600 seconds (10 minutes) - 10m 10 minutes - 1h30m 1 hour 30 minutes (90 minutes) - -FILES - /etc/ssh/sshd_config - Contains configuration data for sshd(8). This file should be - writable by root only, but it is recommended (though not - necessary) that it be world-readable. - -SEE ALSO - sshd(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 5.5 February 27, 2014 OpenBSD 5.5 |
