1SSHD(8) OpenBSD System Manager's Manual SSHD(8) 2 3NAME 4 sshd - OpenSSH SSH daemon 5 6SYNOPSIS 7 sshd [-46DdeiqTt] [-b bits] [-C connection_spec] 8 [-c host_certificate_file] [-E log_file] [-f config_file] 9 [-g login_grace_time] [-h host_key_file] [-k key_gen_time] 10 [-o option] [-p port] [-u len] 11 12DESCRIPTION 13 sshd (OpenSSH Daemon) is the daemon program for ssh(1). Together these 14 programs replace rlogin(1) and rsh(1), and provide secure encrypted 15 communications between two untrusted hosts over an insecure network. 16 17 sshd listens for connections from clients. It is normally started at 18 boot from /etc/rc. It forks a new daemon for each incoming connection. 19 The forked daemons handle key exchange, encryption, authentication, 20 command execution, and data exchange. 21 22 sshd can be configured using command-line options or a configuration file 23 (by default sshd_config(5)); command-line options override values 24 specified in the configuration file. sshd rereads its configuration file 25 when it receives a hangup signal, SIGHUP, by executing itself with the 26 name and options it was started with, e.g. /usr/sbin/sshd. 27 28 The options are as follows: 29 30 -4 Forces sshd to use IPv4 addresses only. 31 32 -6 Forces sshd to use IPv6 addresses only. 33 34 -b bits 35 Specifies the number of bits in the ephemeral protocol version 1 36 server key (default 1024). 37 38 -C connection_spec 39 Specify the connection parameters to use for the -T extended test 40 mode. If provided, any Match directives in the configuration 41 file that would apply to the specified user, host, and address 42 will be set before the configuration is written to standard 43 output. The connection parameters are supplied as keyword=value 44 pairs. The keywords are ``user'', ``host'', ``laddr'', 45 ``lport'', and ``addr''. All are required and may be supplied in 46 any order, either with multiple -C options or as a comma- 47 separated list. 48 49 -c host_certificate_file 50 Specifies a path to a certificate file to identify sshd during 51 key exchange. The certificate file must match a host key file 52 specified using the -h option or the HostKey configuration 53 directive. 54 55 -D When this option is specified, sshd will not detach and does not 56 become a daemon. This allows easy monitoring of sshd. 57 58 -d Debug mode. The server sends verbose debug output to standard 59 error, and does not put itself in the background. The server 60 also will not fork and will only process one connection. This 61 option is only intended for debugging for the server. Multiple 62 -d options increase the debugging level. Maximum is 3. 63 64 -E log_file 65 Append debug logs to log_file instead of the system log. 66 67 -e Write debug logs to standard error instead of the system log. 68 69 -f config_file 70 Specifies the name of the configuration file. The default is 71 /etc/ssh/sshd_config. sshd refuses to start if there is no 72 configuration file. 73 74 -g login_grace_time 75 Gives the grace time for clients to authenticate themselves 76 (default 120 seconds). If the client fails to authenticate the 77 user within this many seconds, the server disconnects and exits. 78 A value of zero indicates no limit. 79 80 -h host_key_file 81 Specifies a file from which a host key is read. This option must 82 be given if sshd is not run as root (as the normal host key files 83 are normally not readable by anyone but root). The default is 84 /etc/ssh/ssh_host_key for protocol version 1, and 85 /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_ecdsa_key. 86 /etc/ssh/ssh_host_ed25519_key and /etc/ssh/ssh_host_rsa_key for 87 protocol version 2. It is possible to have multiple host key 88 files for the different protocol versions and host key 89 algorithms. 90 91 -i Specifies that sshd is being run from inetd(8). sshd is normally 92 not run from inetd because it needs to generate the server key 93 before it can respond to the client, and this may take tens of 94 seconds. Clients would have to wait too long if the key was 95 regenerated every time. However, with small key sizes (e.g. 512) 96 using sshd from inetd may be feasible. 97 98 -k key_gen_time 99 Specifies how often the ephemeral protocol version 1 server key 100 is regenerated (default 3600 seconds, or one hour). The 101 motivation for regenerating the key fairly often is that the key 102 is not stored anywhere, and after about an hour it becomes 103 impossible to recover the key for decrypting intercepted 104 communications even if the machine is cracked into or physically 105 seized. A value of zero indicates that the key will never be 106 regenerated. 107 108 -o option 109 Can be used to give options in the format used in the 110 configuration file. This is useful for specifying options for 111 which there is no separate command-line flag. For full details 112 of the options, and their values, see sshd_config(5). 113 114 -p port 115 Specifies the port on which the server listens for connections 116 (default 22). Multiple port options are permitted. Ports 117 specified in the configuration file with the Port option are 118 ignored when a command-line port is specified. Ports specified 119 using the ListenAddress option override command-line ports. 120 121 -q Quiet mode. Nothing is sent to the system log. Normally the 122 beginning, authentication, and termination of each connection is 123 logged. 124 125 -T Extended test mode. Check the validity of the configuration 126 file, output the effective configuration to stdout and then exit. 127 Optionally, Match rules may be applied by specifying the 128 connection parameters using one or more -C options. 129 130 -t Test mode. Only check the validity of the configuration file and 131 sanity of the keys. This is useful for updating sshd reliably as 132 configuration options may change. 133 134 -u len This option is used to specify the size of the field in the utmp 135 structure that holds the remote host name. If the resolved host 136 name is longer than len, the dotted decimal value will be used 137 instead. This allows hosts with very long host names that 138 overflow this field to still be uniquely identified. Specifying 139 -u0 indicates that only dotted decimal addresses should be put 140 into the utmp file. -u0 may also be used to prevent sshd from 141 making DNS requests unless the authentication mechanism or 142 configuration requires it. Authentication mechanisms that may 143 require DNS include RhostsRSAAuthentication, 144 HostbasedAuthentication, and using a from="pattern-list" option 145 in a key file. Configuration options that require DNS include 146 using a USER@HOST pattern in AllowUsers or DenyUsers. 147 148AUTHENTICATION 149 The OpenSSH SSH daemon supports SSH protocols 1 and 2. The default is to 150 use protocol 2 only, though this can be changed via the Protocol option 151 in sshd_config(5). Protocol 2 supports DSA, ECDSA, ED25519 and RSA keys; 152 protocol 1 only supports RSA keys. For both protocols, each host has a 153 host-specific key, normally 2048 bits, used to identify the host. 154 155 Forward security for protocol 1 is provided through an additional server 156 key, normally 768 bits, generated when the server starts. This key is 157 normally regenerated every hour if it has been used, and is never stored 158 on disk. Whenever a client connects, the daemon responds with its public 159 host and server keys. The client compares the RSA host key against its 160 own database to verify that it has not changed. The client then 161 generates a 256-bit random number. It encrypts this random number using 162 both the host key and the server key, and sends the encrypted number to 163 the server. Both sides then use this random number as a session key 164 which is used to encrypt all further communications in the session. The 165 rest of the session is encrypted using a conventional cipher, currently 166 Blowfish or 3DES, with 3DES being used by default. The client selects 167 the encryption algorithm to use from those offered by the server. 168 169 For protocol 2, forward security is provided through a Diffie-Hellman key 170 agreement. This key agreement results in a shared session key. The rest 171 of the session is encrypted using a symmetric cipher, currently 128-bit 172 AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES. The 173 client selects the encryption algorithm to use from those offered by the 174 server. Additionally, session integrity is provided through a 175 cryptographic message authentication code (hmac-md5, hmac-sha1, umac-64, 176 umac-128, hmac-ripemd160, hmac-sha2-256 or hmac-sha2-512). 177 178 Finally, the server and the client enter an authentication dialog. The 179 client tries to authenticate itself using host-based authentication, 180 public key authentication, challenge-response authentication, or password 181 authentication. 182 183 Regardless of the authentication type, the account is checked to ensure 184 that it is accessible. An account is not accessible if it is locked, 185 listed in DenyUsers or its group is listed in DenyGroups . The 186 definition of a locked account is system dependant. Some platforms have 187 their own account database (eg AIX) and some modify the passwd field ( 188 `*LK*' on Solaris and UnixWare, `*' on HP-UX, containing `Nologin' on 189 Tru64, a leading `*LOCKED*' on FreeBSD and a leading `!' on most 190 Linuxes). If there is a requirement to disable password authentication 191 for the account while allowing still public-key, then the passwd field 192 should be set to something other than these values (eg `NP' or `*NP*' ). 193 194 If the client successfully authenticates itself, a dialog for preparing 195 the session is entered. At this time the client may request things like 196 allocating a pseudo-tty, forwarding X11 connections, forwarding TCP 197 connections, or forwarding the authentication agent connection over the 198 secure channel. 199 200 After this, the client either requests a shell or execution of a command. 201 The sides then enter session mode. In this mode, either side may send 202 data at any time, and such data is forwarded to/from the shell or command 203 on the server side, and the user terminal in the client side. 204 205 When the user program terminates and all forwarded X11 and other 206 connections have been closed, the server sends command exit status to the 207 client, and both sides exit. 208 209LOGIN PROCESS 210 When a user successfully logs in, sshd does the following: 211 212 1. If the login is on a tty, and no command has been specified, 213 prints last login time and /etc/motd (unless prevented in the 214 configuration file or by ~/.hushlogin; see the FILES section). 215 216 2. If the login is on a tty, records login time. 217 218 3. Checks /etc/nologin; if it exists, prints contents and quits 219 (unless root). 220 221 4. Changes to run with normal user privileges. 222 223 5. Sets up basic environment. 224 225 6. Reads the file ~/.ssh/environment, if it exists, and users are 226 allowed to change their environment. See the 227 PermitUserEnvironment option in sshd_config(5). 228 229 7. Changes to user's home directory. 230 231 8. If ~/.ssh/rc exists, runs it; else if /etc/ssh/sshrc exists, 232 runs it; otherwise runs xauth. The ``rc'' files are given the 233 X11 authentication protocol and cookie in standard input. See 234 SSHRC, below. 235 236 9. Runs user's shell or command. 237 238SSHRC 239 If the file ~/.ssh/rc exists, sh(1) runs it after reading the environment 240 files but before starting the user's shell or command. It must not 241 produce any output on stdout; stderr must be used instead. If X11 242 forwarding is in use, it will receive the "proto cookie" pair in its 243 standard input (and DISPLAY in its environment). The script must call 244 xauth(1) because sshd will not run xauth automatically to add X11 245 cookies. 246 247 The primary purpose of this file is to run any initialization routines 248 which may be needed before the user's home directory becomes accessible; 249 AFS is a particular example of such an environment. 250 251 This file will probably contain some initialization code followed by 252 something similar to: 253 254 if read proto cookie && [ -n "$DISPLAY" ]; then 255 if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then 256 # X11UseLocalhost=yes 257 echo add unix:`echo $DISPLAY | 258 cut -c11-` $proto $cookie 259 else 260 # X11UseLocalhost=no 261 echo add $DISPLAY $proto $cookie 262 fi | xauth -q - 263 fi 264 265 If this file does not exist, /etc/ssh/sshrc is run, and if that does not 266 exist either, xauth is used to add the cookie. 267 268AUTHORIZED_KEYS FILE FORMAT 269 AuthorizedKeysFile specifies the files containing public keys for public 270 key authentication; if none is specified, the default is 271 ~/.ssh/authorized_keys and ~/.ssh/authorized_keys2. Each line of the 272 file contains one key (empty lines and lines starting with a `#' are 273 ignored as comments). Protocol 1 public keys consist of the following 274 space-separated fields: options, bits, exponent, modulus, comment. 275 Protocol 2 public key consist of: options, keytype, base64-encoded key, 276 comment. The options field is optional; its presence is determined by 277 whether the line starts with a number or not (the options field never 278 starts with a number). The bits, exponent, modulus, and comment fields 279 give the RSA key for protocol version 1; the comment field is not used 280 for anything (but may be convenient for the user to identify the key). 281 For protocol version 2 the keytype is ``ecdsa-sha2-nistp256'', 282 ``ecdsa-sha2-nistp384'', ``ecdsa-sha2-nistp521'', ``ssh-ed25519'', 283 ``ssh-dss'' or ``ssh-rsa''. 284 285 Note that lines in this file are usually several hundred bytes long 286 (because of the size of the public key encoding) up to a limit of 8 287 kilobytes, which permits DSA keys up to 8 kilobits and RSA keys up to 16 288 kilobits. You don't want to type them in; instead, copy the 289 identity.pub, id_dsa.pub, id_ecdsa.pub, id_ed25519.pub, or the id_rsa.pub 290 file and edit it. 291 292 sshd enforces a minimum RSA key modulus size for protocol 1 and protocol 293 2 keys of 768 bits. 294 295 The options (if present) consist of comma-separated option 296 specifications. No spaces are permitted, except within double quotes. 297 The following option specifications are supported (note that option 298 keywords are case-insensitive): 299 300 cert-authority 301 Specifies that the listed key is a certification authority (CA) 302 that is trusted to validate signed certificates for user 303 authentication. 304 305 Certificates may encode access restrictions similar to these key 306 options. If both certificate restrictions and key options are 307 present, the most restrictive union of the two is applied. 308 309 command="command" 310 Specifies that the command is executed whenever this key is used 311 for authentication. The command supplied by the user (if any) is 312 ignored. The command is run on a pty if the client requests a 313 pty; otherwise it is run without a tty. If an 8-bit clean 314 channel is required, one must not request a pty or should specify 315 no-pty. A quote may be included in the command by quoting it 316 with a backslash. This option might be useful to restrict 317 certain public keys to perform just a specific operation. An 318 example might be a key that permits remote backups but nothing 319 else. Note that the client may specify TCP and/or X11 forwarding 320 unless they are explicitly prohibited. The command originally 321 supplied by the client is available in the SSH_ORIGINAL_COMMAND 322 environment variable. Note that this option applies to shell, 323 command or subsystem execution. Also note that this command may 324 be superseded by either a sshd_config(5) ForceCommand directive 325 or a command embedded in a certificate. 326 327 environment="NAME=value" 328 Specifies that the string is to be added to the environment when 329 logging in using this key. Environment variables set this way 330 override other default environment values. Multiple options of 331 this type are permitted. Environment processing is disabled by 332 default and is controlled via the PermitUserEnvironment option. 333 This option is automatically disabled if UseLogin is enabled. 334 335 from="pattern-list" 336 Specifies that in addition to public key authentication, either 337 the canonical name of the remote host or its IP address must be 338 present in the comma-separated list of patterns. See PATTERNS in 339 ssh_config(5) for more information on patterns. 340 341 In addition to the wildcard matching that may be applied to 342 hostnames or addresses, a from stanza may match IP addresses 343 using CIDR address/masklen notation. 344 345 The purpose of this option is to optionally increase security: 346 public key authentication by itself does not trust the network or 347 name servers or anything (but the key); however, if somebody 348 somehow steals the key, the key permits an intruder to log in 349 from anywhere in the world. This additional option makes using a 350 stolen key more difficult (name servers and/or routers would have 351 to be compromised in addition to just the key). 352 353 no-agent-forwarding 354 Forbids authentication agent forwarding when this key is used for 355 authentication. 356 357 no-port-forwarding 358 Forbids TCP forwarding when this key is used for authentication. 359 Any port forward requests by the client will return an error. 360 This might be used, e.g. in connection with the command option. 361 362 no-pty Prevents tty allocation (a request to allocate a pty will fail). 363 364 no-user-rc 365 Disables execution of ~/.ssh/rc. 366 367 no-X11-forwarding 368 Forbids X11 forwarding when this key is used for authentication. 369 Any X11 forward requests by the client will return an error. 370 371 permitopen="host:port" 372 Limit local ``ssh -L'' port forwarding such that it may only 373 connect to the specified host and port. IPv6 addresses can be 374 specified by enclosing the address in square brackets. Multiple 375 permitopen options may be applied separated by commas. No 376 pattern matching is performed on the specified hostnames, they 377 must be literal domains or addresses. A port specification of * 378 matches any port. 379 380 principals="principals" 381 On a cert-authority line, specifies allowed principals for 382 certificate authentication as a comma-separated list. At least 383 one name from the list must appear in the certificate's list of 384 principals for the certificate to be accepted. This option is 385 ignored for keys that are not marked as trusted certificate 386 signers using the cert-authority option. 387 388 tunnel="n" 389 Force a tun(4) device on the server. Without this option, the 390 next available device will be used if the client requests a 391 tunnel. 392 393 An example authorized_keys file: 394 395 # Comments allowed at start of line 396 ssh-rsa AAAAB3Nza...LiPk== user@example.net 397 from="*.sales.example.net,!pc.sales.example.net" ssh-rsa 398 AAAAB2...19Q== john@example.net 399 command="dump /home",no-pty,no-port-forwarding ssh-dss 400 AAAAC3...51R== example.net 401 permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-dss 402 AAAAB5...21S== 403 tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...== 404 jane@example.net 405 406SSH_KNOWN_HOSTS FILE FORMAT 407 The /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts files contain host 408 public keys for all known hosts. The global file should be prepared by 409 the administrator (optional), and the per-user file is maintained 410 automatically: whenever the user connects from an unknown host, its key 411 is added to the per-user file. 412 413 Each line in these files contains the following fields: markers 414 (optional), hostnames, bits, exponent, modulus, comment. The fields are 415 separated by spaces. 416 417 The marker is optional, but if it is present then it must be one of 418 ``@cert-authority'', to indicate that the line contains a certification 419 authority (CA) key, or ``@revoked'', to indicate that the key contained 420 on the line is revoked and must not ever be accepted. Only one marker 421 should be used on a key line. 422 423 Hostnames is a comma-separated list of patterns (`*' and `?' act as 424 wildcards); each pattern in turn is matched against the canonical host 425 name (when authenticating a client) or against the user-supplied name 426 (when authenticating a server). A pattern may also be preceded by `!' to 427 indicate negation: if the host name matches a negated pattern, it is not 428 accepted (by that line) even if it matched another pattern on the line. 429 A hostname or address may optionally be enclosed within `[' and `]' 430 brackets then followed by `:' and a non-standard port number. 431 432 Alternately, hostnames may be stored in a hashed form which hides host 433 names and addresses should the file's contents be disclosed. Hashed 434 hostnames start with a `|' character. Only one hashed hostname may 435 appear on a single line and none of the above negation or wildcard 436 operators may be applied. 437 438 Bits, exponent, and modulus are taken directly from the RSA host key; 439 they can be obtained, for example, from /etc/ssh/ssh_host_key.pub. The 440 optional comment field continues to the end of the line, and is not used. 441 442 Lines starting with `#' and empty lines are ignored as comments. 443 444 When performing host authentication, authentication is accepted if any 445 matching line has the proper key; either one that matches exactly or, if 446 the server has presented a certificate for authentication, the key of the 447 certification authority that signed the certificate. For a key to be 448 trusted as a certification authority, it must use the ``@cert-authority'' 449 marker described above. 450 451 The known hosts file also provides a facility to mark keys as revoked, 452 for example when it is known that the associated private key has been 453 stolen. Revoked keys are specified by including the ``@revoked'' marker 454 at the beginning of the key line, and are never accepted for 455 authentication or as certification authorities, but instead will produce 456 a warning from ssh(1) when they are encountered. 457 458 It is permissible (but not recommended) to have several lines or 459 different host keys for the same names. This will inevitably happen when 460 short forms of host names from different domains are put in the file. It 461 is possible that the files contain conflicting information; 462 authentication is accepted if valid information can be found from either 463 file. 464 465 Note that the lines in these files are typically hundreds of characters 466 long, and you definitely don't want to type in the host keys by hand. 467 Rather, generate them by a script, ssh-keyscan(1) or by taking 468 /etc/ssh/ssh_host_key.pub and adding the host names at the front. 469 ssh-keygen(1) also offers some basic automated editing for 470 ~/.ssh/known_hosts including removing hosts matching a host name and 471 converting all host names to their hashed representations. 472 473 An example ssh_known_hosts file: 474 475 # Comments allowed at start of line 476 closenet,...,192.0.2.53 1024 37 159...93 closenet.example.net 477 cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....= 478 # A hashed hostname 479 |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa 480 AAAA1234.....= 481 # A revoked key 482 @revoked * ssh-rsa AAAAB5W... 483 # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org 484 @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W... 485 486FILES 487 ~/.hushlogin 488 This file is used to suppress printing the last login time and 489 /etc/motd, if PrintLastLog and PrintMotd, respectively, are 490 enabled. It does not suppress printing of the banner specified 491 by Banner. 492 493 ~/.rhosts 494 This file is used for host-based authentication (see ssh(1) for 495 more information). On some machines this file may need to be 496 world-readable if the user's home directory is on an NFS 497 partition, because sshd reads it as root. Additionally, this 498 file must be owned by the user, and must not have write 499 permissions for anyone else. The recommended permission for most 500 machines is read/write for the user, and not accessible by 501 others. 502 503 ~/.shosts 504 This file is used in exactly the same way as .rhosts, but allows 505 host-based authentication without permitting login with 506 rlogin/rsh. 507 508 ~/.ssh/ 509 This directory is the default location for all user-specific 510 configuration and authentication information. There is no 511 general requirement to keep the entire contents of this directory 512 secret, but the recommended permissions are read/write/execute 513 for the user, and not accessible by others. 514 515 ~/.ssh/authorized_keys 516 Lists the public keys (DSA, ECDSA, ED25519, RSA) that can be used 517 for logging in as this user. The format of this file is 518 described above. The content of the file is not highly 519 sensitive, but the recommended permissions are read/write for the 520 user, and not accessible by others. 521 522 If this file, the ~/.ssh directory, or the user's home directory 523 are writable by other users, then the file could be modified or 524 replaced by unauthorized users. In this case, sshd will not 525 allow it to be used unless the StrictModes option has been set to 526 ``no''. 527 528 ~/.ssh/environment 529 This file is read into the environment at login (if it exists). 530 It can only contain empty lines, comment lines (that start with 531 `#'), and assignment lines of the form name=value. The file 532 should be writable only by the user; it need not be readable by 533 anyone else. Environment processing is disabled by default and 534 is controlled via the PermitUserEnvironment option. 535 536 ~/.ssh/known_hosts 537 Contains a list of host keys for all hosts the user has logged 538 into that are not already in the systemwide list of known host 539 keys. The format of this file is described above. This file 540 should be writable only by root/the owner and can, but need not 541 be, world-readable. 542 543 ~/.ssh/rc 544 Contains initialization routines to be run before the user's home 545 directory becomes accessible. This file should be writable only 546 by the user, and need not be readable by anyone else. 547 548 /etc/hosts.allow 549 /etc/hosts.deny 550 Access controls that should be enforced by tcp-wrappers are 551 defined here. Further details are described in hosts_access(5). 552 553 /etc/hosts.equiv 554 This file is for host-based authentication (see ssh(1)). It 555 should only be writable by root. 556 557 /etc/moduli 558 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group 559 Exchange". The file format is described in moduli(5). 560 561 /etc/motd 562 See motd(5). 563 564 /etc/nologin 565 If this file exists, sshd refuses to let anyone except root log 566 in. The contents of the file are displayed to anyone trying to 567 log in, and non-root connections are refused. The file should be 568 world-readable. 569 570 /etc/shosts.equiv 571 This file is used in exactly the same way as hosts.equiv, but 572 allows host-based authentication without permitting login with 573 rlogin/rsh. 574 575 /etc/ssh/ssh_host_key 576 /etc/ssh/ssh_host_dsa_key 577 /etc/ssh/ssh_host_ecdsa_key 578 /etc/ssh/ssh_host_ed25519_key 579 /etc/ssh/ssh_host_rsa_key 580 These files contain the private parts of the host keys. These 581 files should only be owned by root, readable only by root, and 582 not accessible to others. Note that sshd does not start if these 583 files are group/world-accessible. 584 585 /etc/ssh/ssh_host_key.pub 586 /etc/ssh/ssh_host_dsa_key.pub 587 /etc/ssh/ssh_host_ecdsa_key.pub 588 /etc/ssh/ssh_host_ed25519_key.pub 589 /etc/ssh/ssh_host_rsa_key.pub 590 These files contain the public parts of the host keys. These 591 files should be world-readable but writable only by root. Their 592 contents should match the respective private parts. These files 593 are not really used for anything; they are provided for the 594 convenience of the user so their contents can be copied to known 595 hosts files. These files are created using ssh-keygen(1). 596 597 /etc/ssh/ssh_known_hosts 598 Systemwide list of known host keys. This file should be prepared 599 by the system administrator to contain the public host keys of 600 all machines in the organization. The format of this file is 601 described above. This file should be writable only by root/the 602 owner and should be world-readable. 603 604 /etc/ssh/sshd_config 605 Contains configuration data for sshd. The file format and 606 configuration options are described in sshd_config(5). 607 608 /etc/ssh/sshrc 609 Similar to ~/.ssh/rc, it can be used to specify machine-specific 610 login-time initializations globally. This file should be 611 writable only by root, and should be world-readable. 612 613 /var/empty 614 chroot(2) directory used by sshd during privilege separation in 615 the pre-authentication phase. The directory should not contain 616 any files and must be owned by root and not group or world- 617 writable. 618 619 /var/run/sshd.pid 620 Contains the process ID of the sshd listening for connections (if 621 there are several daemons running concurrently for different 622 ports, this contains the process ID of the one started last). 623 The content of this file is not sensitive; it can be world- 624 readable. 625 626SEE ALSO 627 scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), 628 ssh-keyscan(1), chroot(2), hosts_access(5), login.conf(5), moduli(5), 629 sshd_config(5), inetd(8), sftp-server(8) 630 631AUTHORS 632 OpenSSH is a derivative of the original and free ssh 1.2.12 release by 633 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo 634 de Raadt and Dug Song removed many bugs, re-added newer features and 635 created OpenSSH. Markus Friedl contributed the support for SSH protocol 636 versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support 637 for privilege separation. 638 639CAVEATS 640 System security is not improved unless rshd, rlogind, and rexecd are 641 disabled (thus completely disabling rlogin and rsh into the machine). 642 643OpenBSD 5.5 December 7, 2013 OpenBSD 5.5 644