sshd.0 revision 239844
150477SpeterSSHD(8) OpenBSD System Manager's Manual SSHD(8) 222377Spst 322401SphkNAME 422377Spst sshd - OpenSSH SSH daemon 522377Spst 622377SpstSYNOPSIS 788857Sache sshd [-46DdeiqTt] [-b bits] [-C connection_spec] 822377Spst [-c host_certificate_file] [-f config_file] [-g login_grace_time] 979467Smarkm [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len] 1079467Smarkm 1122377SpstDESCRIPTION 1222377Spst sshd (OpenSSH Daemon) is the daemon program for ssh(1). Together these 1379467Smarkm programs replace rlogin(1) and rsh(1), and provide secure encrypted 1483391Sru communications between two untrusted hosts over an insecure network. 1578644Sache 16137164Sru sshd listens for connections from clients. It is normally started at 1722377Spst boot from /etc/rc. It forks a new daemon for each incoming connection. 1822377Spst The forked daemons handle key exchange, encryption, authentication, 1922377Spst command execution, and data exchange. 2022377Spst 21 sshd can be configured using command-line options or a configuration file 22 (by default sshd_config(5)); command-line options override values 23 specified in the configuration file. sshd rereads its configuration file 24 when it receives a hangup signal, SIGHUP, by executing itself with the 25 name and options it was started with, e.g. /usr/sbin/sshd. 26 27 The options are as follows: 28 29 -4 Forces sshd to use IPv4 addresses only. 30 31 -6 Forces sshd to use IPv6 addresses only. 32 33 -b bits 34 Specifies the number of bits in the ephemeral protocol version 1 35 server key (default 1024). 36 37 -C connection_spec 38 Specify the connection parameters to use for the -T extended test 39 mode. If provided, any Match directives in the configuration 40 file that would apply to the specified user, host, and address 41 will be set before the configuration is written to standard 42 output. The connection parameters are supplied as keyword=value 43 pairs. The keywords are ``user'', ``host'', and ``addr''. All 44 are required and may be supplied in any order, either with 45 multiple -C options or as a comma-separated list. 46 47 -c host_certificate_file 48 Specifies a path to a certificate file to identify sshd during 49 key exchange. The certificate file must match a host key file 50 specified using the -h option or the HostKey configuration 51 directive. 52 53 -D When this option is specified, sshd will not detach and does not 54 become a daemon. This allows easy monitoring of sshd. 55 56 -d Debug mode. The server sends verbose debug output to standard 57 error, and does not put itself in the background. The server 58 also will not fork and will only process one connection. This 59 option is only intended for debugging for the server. Multiple 60 -d options increase the debugging level. Maximum is 3. 61 62 -e When this option is specified, sshd will send the output to the 63 standard error instead of the system log. 64 65 -f config_file 66 Specifies the name of the configuration file. The default is 67 /etc/ssh/sshd_config. sshd refuses to start if there is no 68 configuration file. 69 70 -g login_grace_time 71 Gives the grace time for clients to authenticate themselves 72 (default 120 seconds). If the client fails to authenticate the 73 user within this many seconds, the server disconnects and exits. 74 A value of zero indicates no limit. 75 76 -h host_key_file 77 Specifies a file from which a host key is read. This option must 78 be given if sshd is not run as root (as the normal host key files 79 are normally not readable by anyone but root). The default is 80 /etc/ssh/ssh_host_key for protocol version 1, and 81 /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_ecdsa_key and 82 /etc/ssh/ssh_host_rsa_key for protocol version 2. It is possible 83 to have multiple host key files for the different protocol 84 versions and host key algorithms. 85 86 -i Specifies that sshd is being run from inetd(8). sshd is normally 87 not run from inetd because it needs to generate the server key 88 before it can respond to the client, and this may take tens of 89 seconds. Clients would have to wait too long if the key was 90 regenerated every time. However, with small key sizes (e.g. 512) 91 using sshd from inetd may be feasible. 92 93 -k key_gen_time 94 Specifies how often the ephemeral protocol version 1 server key 95 is regenerated (default 3600 seconds, or one hour). The 96 motivation for regenerating the key fairly often is that the key 97 is not stored anywhere, and after about an hour it becomes 98 impossible to recover the key for decrypting intercepted 99 communications even if the machine is cracked into or physically 100 seized. A value of zero indicates that the key will never be 101 regenerated. 102 103 -o option 104 Can be used to give options in the format used in the 105 configuration file. This is useful for specifying options for 106 which there is no separate command-line flag. For full details 107 of the options, and their values, see sshd_config(5). 108 109 -p port 110 Specifies the port on which the server listens for connections 111 (default 22). Multiple port options are permitted. Ports 112 specified in the configuration file with the Port option are 113 ignored when a command-line port is specified. Ports specified 114 using the ListenAddress option override command-line ports. 115 116 -q Quiet mode. Nothing is sent to the system log. Normally the 117 beginning, authentication, and termination of each connection is 118 logged. 119 120 -T Extended test mode. Check the validity of the configuration 121 file, output the effective configuration to stdout and then exit. 122 Optionally, Match rules may be applied by specifying the 123 connection parameters using one or more -C options. 124 125 -t Test mode. Only check the validity of the configuration file and 126 sanity of the keys. This is useful for updating sshd reliably as 127 configuration options may change. 128 129 -u len This option is used to specify the size of the field in the utmp 130 structure that holds the remote host name. If the resolved host 131 name is longer than len, the dotted decimal value will be used 132 instead. This allows hosts with very long host names that 133 overflow this field to still be uniquely identified. Specifying 134 -u0 indicates that only dotted decimal addresses should be put 135 into the utmp file. -u0 may also be used to prevent sshd from 136 making DNS requests unless the authentication mechanism or 137 configuration requires it. Authentication mechanisms that may 138 require DNS include RhostsRSAAuthentication, 139 HostbasedAuthentication, and using a from="pattern-list" option 140 in a key file. Configuration options that require DNS include 141 using a USER@HOST pattern in AllowUsers or DenyUsers. 142 143AUTHENTICATION 144 The OpenSSH SSH daemon supports SSH protocols 1 and 2. The default is to 145 use protocol 2 only, though this can be changed via the Protocol option 146 in sshd_config(5). Protocol 2 supports DSA, ECDSA and RSA keys; protocol 147 1 only supports RSA keys. For both protocols, each host has a host- 148 specific key, normally 2048 bits, used to identify the host. 149 150 Forward security for protocol 1 is provided through an additional server 151 key, normally 768 bits, generated when the server starts. This key is 152 normally regenerated every hour if it has been used, and is never stored 153 on disk. Whenever a client connects, the daemon responds with its public 154 host and server keys. The client compares the RSA host key against its 155 own database to verify that it has not changed. The client then 156 generates a 256-bit random number. It encrypts this random number using 157 both the host key and the server key, and sends the encrypted number to 158 the server. Both sides then use this random number as a session key 159 which is used to encrypt all further communications in the session. The 160 rest of the session is encrypted using a conventional cipher, currently 161 Blowfish or 3DES, with 3DES being used by default. The client selects 162 the encryption algorithm to use from those offered by the server. 163 164 For protocol 2, forward security is provided through a Diffie-Hellman key 165 agreement. This key agreement results in a shared session key. The rest 166 of the session is encrypted using a symmetric cipher, currently 128-bit 167 AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES. The 168 client selects the encryption algorithm to use from those offered by the 169 server. Additionally, session integrity is provided through a 170 cryptographic message authentication code (hmac-md5, hmac-sha1, umac-64, 171 hmac-ripemd160, hmac-sha2-256 or hmac-sha2-512). 172 173 Finally, the server and the client enter an authentication dialog. The 174 client tries to authenticate itself using host-based authentication, 175 public key authentication, challenge-response authentication, or password 176 authentication. 177 178 Regardless of the authentication type, the account is checked to ensure 179 that it is accessible. An account is not accessible if it is locked, 180 listed in DenyUsers or its group is listed in DenyGroups . The 181 definition of a locked account is system dependant. Some platforms have 182 their own account database (eg AIX) and some modify the passwd field ( 183 `*LK*' on Solaris and UnixWare, `*' on HP-UX, containing `Nologin' on 184 Tru64, a leading `*LOCKED*' on FreeBSD and a leading `!' on most 185 Linuxes). If there is a requirement to disable password authentication 186 for the account while allowing still public-key, then the passwd field 187 should be set to something other than these values (eg `NP' or `*NP*' ). 188 189 If the client successfully authenticates itself, a dialog for preparing 190 the session is entered. At this time the client may request things like 191 allocating a pseudo-tty, forwarding X11 connections, forwarding TCP 192 connections, or forwarding the authentication agent connection over the 193 secure channel. 194 195 After this, the client either requests a shell or execution of a command. 196 The sides then enter session mode. In this mode, either side may send 197 data at any time, and such data is forwarded to/from the shell or command 198 on the server side, and the user terminal in the client side. 199 200 When the user program terminates and all forwarded X11 and other 201 connections have been closed, the server sends command exit status to the 202 client, and both sides exit. 203 204LOGIN PROCESS 205 When a user successfully logs in, sshd does the following: 206 207 1. If the login is on a tty, and no command has been specified, 208 prints last login time and /etc/motd (unless prevented in the 209 configuration file or by ~/.hushlogin; see the FILES section). 210 211 2. If the login is on a tty, records login time. 212 213 3. Checks /etc/nologin; if it exists, prints contents and quits 214 (unless root). 215 216 4. Changes to run with normal user privileges. 217 218 5. Sets up basic environment. 219 220 6. Reads the file ~/.ssh/environment, if it exists, and users are 221 allowed to change their environment. See the 222 PermitUserEnvironment option in sshd_config(5). 223 224 7. Changes to user's home directory. 225 226 8. If ~/.ssh/rc exists, runs it; else if /etc/ssh/sshrc exists, 227 runs it; otherwise runs xauth. The ``rc'' files are given the 228 X11 authentication protocol and cookie in standard input. See 229 SSHRC, below. 230 231 9. Runs user's shell or command. 232 233SSHRC 234 If the file ~/.ssh/rc exists, sh(1) runs it after reading the environment 235 files but before starting the user's shell or command. It must not 236 produce any output on stdout; stderr must be used instead. If X11 237 forwarding is in use, it will receive the "proto cookie" pair in its 238 standard input (and DISPLAY in its environment). The script must call 239 xauth(1) because sshd will not run xauth automatically to add X11 240 cookies. 241 242 The primary purpose of this file is to run any initialization routines 243 which may be needed before the user's home directory becomes accessible; 244 AFS is a particular example of such an environment. 245 246 This file will probably contain some initialization code followed by 247 something similar to: 248 249 if read proto cookie && [ -n "$DISPLAY" ]; then 250 if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then 251 # X11UseLocalhost=yes 252 echo add unix:`echo $DISPLAY | 253 cut -c11-` $proto $cookie 254 else 255 # X11UseLocalhost=no 256 echo add $DISPLAY $proto $cookie 257 fi | xauth -q - 258 fi 259 260 If this file does not exist, /etc/ssh/sshrc is run, and if that does not 261 exist either, xauth is used to add the cookie. 262 263AUTHORIZED_KEYS FILE FORMAT 264 AuthorizedKeysFile specifies the files containing public keys for public 265 key authentication; if none is specified, the default is 266 ~/.ssh/authorized_keys and ~/.ssh/authorized_keys2. Each line of the 267 file contains one key (empty lines and lines starting with a `#' are 268 ignored as comments). Protocol 1 public keys consist of the following 269 space-separated fields: options, bits, exponent, modulus, comment. 270 Protocol 2 public key consist of: options, keytype, base64-encoded key, 271 comment. The options field is optional; its presence is determined by 272 whether the line starts with a number or not (the options field never 273 starts with a number). The bits, exponent, modulus, and comment fields 274 give the RSA key for protocol version 1; the comment field is not used 275 for anything (but may be convenient for the user to identify the key). 276 For protocol version 2 the keytype is ``ecdsa-sha2-nistp256'', 277 ``ecdsa-sha2-nistp384'', ``ecdsa-sha2-nistp521'', ``ssh-dss'' or 278 ``ssh-rsa''. 279 280 Note that lines in this file are usually several hundred bytes long 281 (because of the size of the public key encoding) up to a limit of 8 282 kilobytes, which permits DSA keys up to 8 kilobits and RSA keys up to 16 283 kilobits. You don't want to type them in; instead, copy the 284 identity.pub, id_dsa.pub, id_ecdsa.pub, or the id_rsa.pub file and edit 285 it. 286 287 sshd enforces a minimum RSA key modulus size for protocol 1 and protocol 288 2 keys of 768 bits. 289 290 The options (if present) consist of comma-separated option 291 specifications. No spaces are permitted, except within double quotes. 292 The following option specifications are supported (note that option 293 keywords are case-insensitive): 294 295 cert-authority 296 Specifies that the listed key is a certification authority (CA) 297 that is trusted to validate signed certificates for user 298 authentication. 299 300 Certificates may encode access restrictions similar to these key 301 options. If both certificate restrictions and key options are 302 present, the most restrictive union of the two is applied. 303 304 command="command" 305 Specifies that the command is executed whenever this key is used 306 for authentication. The command supplied by the user (if any) is 307 ignored. The command is run on a pty if the client requests a 308 pty; otherwise it is run without a tty. If an 8-bit clean 309 channel is required, one must not request a pty or should specify 310 no-pty. A quote may be included in the command by quoting it 311 with a backslash. This option might be useful to restrict 312 certain public keys to perform just a specific operation. An 313 example might be a key that permits remote backups but nothing 314 else. Note that the client may specify TCP and/or X11 forwarding 315 unless they are explicitly prohibited. The command originally 316 supplied by the client is available in the SSH_ORIGINAL_COMMAND 317 environment variable. Note that this option applies to shell, 318 command or subsystem execution. Also note that this command may 319 be superseded by either a sshd_config(5) ForceCommand directive 320 or a command embedded in a certificate. 321 322 environment="NAME=value" 323 Specifies that the string is to be added to the environment when 324 logging in using this key. Environment variables set this way 325 override other default environment values. Multiple options of 326 this type are permitted. Environment processing is disabled by 327 default and is controlled via the PermitUserEnvironment option. 328 This option is automatically disabled if UseLogin is enabled. 329 330 from="pattern-list" 331 Specifies that in addition to public key authentication, either 332 the canonical name of the remote host or its IP address must be 333 present in the comma-separated list of patterns. See PATTERNS in 334 ssh_config(5) for more information on patterns. 335 336 In addition to the wildcard matching that may be applied to 337 hostnames or addresses, a from stanza may match IP addresses 338 using CIDR address/masklen notation. 339 340 The purpose of this option is to optionally increase security: 341 public key authentication by itself does not trust the network or 342 name servers or anything (but the key); however, if somebody 343 somehow steals the key, the key permits an intruder to log in 344 from anywhere in the world. This additional option makes using a 345 stolen key more difficult (name servers and/or routers would have 346 to be compromised in addition to just the key). 347 348 no-agent-forwarding 349 Forbids authentication agent forwarding when this key is used for 350 authentication. 351 352 no-port-forwarding 353 Forbids TCP forwarding when this key is used for authentication. 354 Any port forward requests by the client will return an error. 355 This might be used, e.g. in connection with the command option. 356 357 no-pty Prevents tty allocation (a request to allocate a pty will fail). 358 359 no-user-rc 360 Disables execution of ~/.ssh/rc. 361 362 no-X11-forwarding 363 Forbids X11 forwarding when this key is used for authentication. 364 Any X11 forward requests by the client will return an error. 365 366 permitopen="host:port" 367 Limit local ``ssh -L'' port forwarding such that it may only 368 connect to the specified host and port. IPv6 addresses can be 369 specified by enclosing the address in square brackets. Multiple 370 permitopen options may be applied separated by commas. No 371 pattern matching is performed on the specified hostnames, they 372 must be literal domains or addresses. A port specification of * 373 matches any port. 374 375 principals="principals" 376 On a cert-authority line, specifies allowed principals for 377 certificate authentication as a comma-separated list. At least 378 one name from the list must appear in the certificate's list of 379 principals for the certificate to be accepted. This option is 380 ignored for keys that are not marked as trusted certificate 381 signers using the cert-authority option. 382 383 tunnel="n" 384 Force a tun(4) device on the server. Without this option, the 385 next available device will be used if the client requests a 386 tunnel. 387 388 An example authorized_keys file: 389 390 # Comments allowed at start of line 391 ssh-rsa AAAAB3Nza...LiPk== user@example.net 392 from="*.sales.example.net,!pc.sales.example.net" ssh-rsa 393 AAAAB2...19Q== john@example.net 394 command="dump /home",no-pty,no-port-forwarding ssh-dss 395 AAAAC3...51R== example.net 396 permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-dss 397 AAAAB5...21S== 398 tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...== 399 jane@example.net 400 401SSH_KNOWN_HOSTS FILE FORMAT 402 The /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts files contain host 403 public keys for all known hosts. The global file should be prepared by 404 the administrator (optional), and the per-user file is maintained 405 automatically: whenever the user connects from an unknown host, its key 406 is added to the per-user file. 407 408 Each line in these files contains the following fields: markers 409 (optional), hostnames, bits, exponent, modulus, comment. The fields are 410 separated by spaces. 411 412 The marker is optional, but if it is present then it must be one of 413 ``@cert-authority'', to indicate that the line contains a certification 414 authority (CA) key, or ``@revoked'', to indicate that the key contained 415 on the line is revoked and must not ever be accepted. Only one marker 416 should be used on a key line. 417 418 Hostnames is a comma-separated list of patterns (`*' and `?' act as 419 wildcards); each pattern in turn is matched against the canonical host 420 name (when authenticating a client) or against the user-supplied name 421 (when authenticating a server). A pattern may also be preceded by `!' to 422 indicate negation: if the host name matches a negated pattern, it is not 423 accepted (by that line) even if it matched another pattern on the line. 424 A hostname or address may optionally be enclosed within `[' and `]' 425 brackets then followed by `:' and a non-standard port number. 426 427 Alternately, hostnames may be stored in a hashed form which hides host 428 names and addresses should the file's contents be disclosed. Hashed 429 hostnames start with a `|' character. Only one hashed hostname may 430 appear on a single line and none of the above negation or wildcard 431 operators may be applied. 432 433 Bits, exponent, and modulus are taken directly from the RSA host key; 434 they can be obtained, for example, from /etc/ssh/ssh_host_key.pub. The 435 optional comment field continues to the end of the line, and is not used. 436 437 Lines starting with `#' and empty lines are ignored as comments. 438 439 When performing host authentication, authentication is accepted if any 440 matching line has the proper key; either one that matches exactly or, if 441 the server has presented a certificate for authentication, the key of the 442 certification authority that signed the certificate. For a key to be 443 trusted as a certification authority, it must use the ``@cert-authority'' 444 marker described above. 445 446 The known hosts file also provides a facility to mark keys as revoked, 447 for example when it is known that the associated private key has been 448 stolen. Revoked keys are specified by including the ``@revoked'' marker 449 at the beginning of the key line, and are never accepted for 450 authentication or as certification authorities, but instead will produce 451 a warning from ssh(1) when they are encountered. 452 453 It is permissible (but not recommended) to have several lines or 454 different host keys for the same names. This will inevitably happen when 455 short forms of host names from different domains are put in the file. It 456 is possible that the files contain conflicting information; 457 authentication is accepted if valid information can be found from either 458 file. 459 460 Note that the lines in these files are typically hundreds of characters 461 long, and you definitely don't want to type in the host keys by hand. 462 Rather, generate them by a script, ssh-keyscan(1) or by taking 463 /etc/ssh/ssh_host_key.pub and adding the host names at the front. 464 ssh-keygen(1) also offers some basic automated editing for 465 ~/.ssh/known_hosts including removing hosts matching a host name and 466 converting all host names to their hashed representations. 467 468 An example ssh_known_hosts file: 469 470 # Comments allowed at start of line 471 closenet,...,192.0.2.53 1024 37 159...93 closenet.example.net 472 cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....= 473 # A hashed hostname 474 |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa 475 AAAA1234.....= 476 # A revoked key 477 @revoked * ssh-rsa AAAAB5W... 478 # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org 479 @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W... 480 481FILES 482 ~/.hushlogin 483 This file is used to suppress printing the last login time and 484 /etc/motd, if PrintLastLog and PrintMotd, respectively, are 485 enabled. It does not suppress printing of the banner specified 486 by Banner. 487 488 ~/.rhosts 489 This file is used for host-based authentication (see ssh(1) for 490 more information). On some machines this file may need to be 491 world-readable if the user's home directory is on an NFS 492 partition, because sshd reads it as root. Additionally, this 493 file must be owned by the user, and must not have write 494 permissions for anyone else. The recommended permission for most 495 machines is read/write for the user, and not accessible by 496 others. 497 498 ~/.shosts 499 This file is used in exactly the same way as .rhosts, but allows 500 host-based authentication without permitting login with 501 rlogin/rsh. 502 503 ~/.ssh/ 504 This directory is the default location for all user-specific 505 configuration and authentication information. There is no 506 general requirement to keep the entire contents of this directory 507 secret, but the recommended permissions are read/write/execute 508 for the user, and not accessible by others. 509 510 ~/.ssh/authorized_keys 511 Lists the public keys (DSA/ECDSA/RSA) that can be used for 512 logging in as this user. The format of this file is described 513 above. The content of the file is not highly sensitive, but the 514 recommended permissions are read/write for the user, and not 515 accessible by others. 516 517 If this file, the ~/.ssh directory, or the user's home directory 518 are writable by other users, then the file could be modified or 519 replaced by unauthorized users. In this case, sshd will not 520 allow it to be used unless the StrictModes option has been set to 521 ``no''. 522 523 ~/.ssh/environment 524 This file is read into the environment at login (if it exists). 525 It can only contain empty lines, comment lines (that start with 526 `#'), and assignment lines of the form name=value. The file 527 should be writable only by the user; it need not be readable by 528 anyone else. Environment processing is disabled by default and 529 is controlled via the PermitUserEnvironment option. 530 531 ~/.ssh/known_hosts 532 Contains a list of host keys for all hosts the user has logged 533 into that are not already in the systemwide list of known host 534 keys. The format of this file is described above. This file 535 should be writable only by root/the owner and can, but need not 536 be, world-readable. 537 538 ~/.ssh/rc 539 Contains initialization routines to be run before the user's home 540 directory becomes accessible. This file should be writable only 541 by the user, and need not be readable by anyone else. 542 543 /etc/hosts.allow 544 /etc/hosts.deny 545 Access controls that should be enforced by tcp-wrappers are 546 defined here. Further details are described in hosts_access(5). 547 548 /etc/hosts.equiv 549 This file is for host-based authentication (see ssh(1)). It 550 should only be writable by root. 551 552 /etc/moduli 553 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group 554 Exchange". The file format is described in moduli(5). 555 556 /etc/motd 557 See motd(5). 558 559 /etc/nologin 560 If this file exists, sshd refuses to let anyone except root log 561 in. The contents of the file are displayed to anyone trying to 562 log in, and non-root connections are refused. The file should be 563 world-readable. 564 565 /etc/shosts.equiv 566 This file is used in exactly the same way as hosts.equiv, but 567 allows host-based authentication without permitting login with 568 rlogin/rsh. 569 570 /etc/ssh/ssh_host_key 571 /etc/ssh/ssh_host_dsa_key 572 /etc/ssh/ssh_host_ecdsa_key 573 /etc/ssh/ssh_host_rsa_key 574 These three files contain the private parts of the host keys. 575 These files should only be owned by root, readable only by root, 576 and not accessible to others. Note that sshd does not start if 577 these files are group/world-accessible. 578 579 /etc/ssh/ssh_host_key.pub 580 /etc/ssh/ssh_host_dsa_key.pub 581 /etc/ssh/ssh_host_ecdsa_key.pub 582 /etc/ssh/ssh_host_rsa_key.pub 583 These three files contain the public parts of the host keys. 584 These files should be world-readable but writable only by root. 585 Their contents should match the respective private parts. These 586 files are not really used for anything; they are provided for the 587 convenience of the user so their contents can be copied to known 588 hosts files. These files are created using ssh-keygen(1). 589 590 /etc/ssh/ssh_known_hosts 591 Systemwide list of known host keys. This file should be prepared 592 by the system administrator to contain the public host keys of 593 all machines in the organization. The format of this file is 594 described above. This file should be writable only by root/the 595 owner and should be world-readable. 596 597 /etc/ssh/sshd_config 598 Contains configuration data for sshd. The file format and 599 configuration options are described in sshd_config(5). 600 601 /etc/ssh/sshrc 602 Similar to ~/.ssh/rc, it can be used to specify machine-specific 603 login-time initializations globally. This file should be 604 writable only by root, and should be world-readable. 605 606 /var/empty 607 chroot(2) directory used by sshd during privilege separation in 608 the pre-authentication phase. The directory should not contain 609 any files and must be owned by root and not group or world- 610 writable. 611 612 /var/run/sshd.pid 613 Contains the process ID of the sshd listening for connections (if 614 there are several daemons running concurrently for different 615 ports, this contains the process ID of the one started last). 616 The content of this file is not sensitive; it can be world- 617 readable. 618 619SEE ALSO 620 scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), 621 ssh-keyscan(1), chroot(2), hosts_access(5), login.conf(5), moduli(5), 622 sshd_config(5), inetd(8), sftp-server(8) 623 624AUTHORS 625 OpenSSH is a derivative of the original and free ssh 1.2.12 release by 626 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo 627 de Raadt and Dug Song removed many bugs, re-added newer features and 628 created OpenSSH. Markus Friedl contributed the support for SSH protocol 629 versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support 630 for privilege separation. 631 632CAVEATS 633 System security is not improved unless rshd, rlogind, and rexecd are 634 disabled (thus completely disabling rlogin and rsh into the machine). 635 636OpenBSD 5.0 September 23, 2011 OpenBSD 5.0 637