ftpd.tproj/ftpd.8

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  32 .\"     @(#)ftpd.8      8.2 (Berkeley) 4/19/94
  33 .\" $FreeBSD: src/libexec/ftpd/ftpd.8,v 1.36 2000/12/18 08:33:25 ru Exp $
  34 .\"
  35 .Dd January 27, 2000
  36 .Dt FTPD 8
  37 .Os BSD 4.2
  38 .Sh NAME
  39 .Nm ftpd
  40 .Nd
  41 Internet File Transfer Protocol server
  42 .Sh SYNOPSIS
  43 .Nm
  44 .Op Fl 4
  45 .Op Fl 6
  46 .Op Fl d
  47 .Op Fl l Op Fl l
  48 .Op Fl A
  49 .Op Fl D
  50 .Op Fl R
  51 .Op Fl S
  52 .Op Fl U
  53 .Op Fl r
  54 .Op Fl E
  55 .Op Fl T Ar maxtimeout
  56 .Op Fl t Ar timeout
  57 .Op Fl a Ar address
  58 .Op Fl p Ar file
  59 .Sh DESCRIPTION
  60 .Nm Ftpd
  61 is the
  62 Internet File Transfer Protocol
  63 server process.  The server uses the
  64 .Tn TCP
  65 protocol
  66 and listens at the port specified in the
  67 .Dq ftp
  68 service specification; see
  69 .Xr services 5 .
  70 .Pp
  71 Available options:
  72 .Bl -tag -width indent
  73 .It Fl d
  74 Debugging information is written to the syslog using LOG_FTP.
  75 .It Fl l
  76 Each successful and failed
  77 .Xr ftp 1
  78 session is logged using syslog with a facility of LOG_FTP.
  79 If this option is specified twice, the retrieve (get), store (put), append,
  80 delete, make directory, remove directory and rename operations and
  81 their filename arguments are also logged.  Note: LOG_FTP messages
  82 are not displayed by
  83 .Xr syslogd 8
  84 by default, and may have to be enabled in
  85 .Xr syslogd 8 Ns 's
  86 configuration file.
  87 .It Fl D
  88 With this option set,
  89 .Nm
  90 will detach and become a daemon, accepting connections on the FTP port and
  91 forking children processes to handle them.
  92 This is lower overhead than starting
  93 .Nm
  94 from
  95 .Xr inetd 8
  96 and is thus useful on busy servers to reduce load.
  97 .It Fl R
  98 With this option set,
  99 .Nm
 100 will revert to historical behavior with regard to security checks on
 101 user operations and restrictions on PORT requests.
 102 Currently,
 103 .Nm
 104 will only honor PORT commands directed to unprivileged ports on the
 105 remote user's host (which violates the FTP protocol specification but
 106 closes some security holes).
 107 .It Fl S
 108 With this option set,
 109 .Nm
 110 logs all anonymous file downloads to the file
 111 .Pa /var/log/ftpd
 112 when this file exists.
 113 .It Fl U
 114 In previous versions of
 115 .Nm ,
 116 when a passive mode client requested a data connection to the server,
 117 the server would use data ports in the range 1024..4999.  Now, by default,
 118 the server will use data ports in the range 49152..65535.  Specifying this
 119 option will revert to the old behavior.
 120 .It Fl T
 121 A client may also request a different timeout period;
 122 the maximum period allowed may be set to
 123 .Ar timeout
 124 seconds with the
 125 .Fl T
 126 option.
 127 The default limit is 2 hours.
 128 .It Fl t
 129 The inactivity timeout period is set to
 130 .Ar timeout
 131 seconds (the default is 15 minutes).
 132 .It Fl a
 133 When
 134 .Fl D
 135 is specified, accept connections only on the specified
 136 .Ar address .
 137 .It Fl p
 138 When
 139 .Fl D
 140 is specified, write the daemon's process ID to
 141 .Ar file .
 142 .It Fl 6
 143 When
 144 .Fl D
 145 is specified, accept connections via AF_INET6 socket.
 146 .It Fl 4
 147 When
 148 .Fl D
 149 is specified, accept IPv4 connections.
 150 When
 151 .Fl 6
 152 is also specified, accept IPv4 connection via AF_INET6 socket.
 153 When
 154 .Fl 6
 155 is not specified, accept IPv4 connection via AF_INET socket.
 156 .It Fl A
 157 Allow only anonymous ftp access.
 158 .It Fl r
 159 Put server in read-only mode.
 160 All commands which may modify the local filesystem are disabled.
 161 .It Fl E
 162 Disable the EPSV command.
 163 This is useful for servers behind older firewalls.
 164 .El
 165 .Pp
 166 The file
 167 .Pa /var/run/nologin
 168 can be used to disable ftp access.
 169 If the file exists,
 170 .Nm
 171 displays it and exits.
 172 If the file
 173 .Pa /etc/ftpwelcome
 174 exists,
 175 .Nm
 176 prints it before issuing the
 177 .Dq ready
 178 message.
 179 If the file
 180 .Pa /etc/ftpmotd
 181 exists,
 182 .Nm
 183 prints it after a successful login.  Note the motd file used is the one
 184 relative to the login environment.  This means the one in
 185 .Pa ~ftp/etc
 186 in the anonymous user's case.
 187 .Pp
 188 The ftp server currently supports the following ftp requests.
 189 The case of the requests is ignored.  Requests marked [RW] are
 190 disabled if
 191 .Fl r
 192 is specified.
 193 .Bl -column "Request" -offset indent
 194 .It Sy Request Ta Sy "Description"
 195 .It ABOR Ta "abort previous command"
 196 .It ACCT Ta "specify account (ignored)"
 197 .It ALLO Ta "allocate storage (vacuously)"
 198 .It APPE Ta "append to a file [RW]"
 199 .It CDUP Ta "change to parent of current working directory"
 200 .It CWD Ta "change working directory"
 201 .It DELE Ta "delete a file [RW]"
 202 .It EPRT Ta "specify data connection port, multiprotocol"
 203 .It EPSV Ta "prepare for server-to-server transfer, multiprotocol"
 204 .It HELP Ta "give help information"
 205 .It LIST Ta "give list files in a directory" Pq Dq Li "ls -lgA"
 206 .It LPRT Ta "specify data connection port, multiprotocol"
 207 .It LPSV Ta "prepare for server-to-server transfer, multiprotocol"
 208 .It MDTM Ta "show last modification time of file"
 209 .It MKD Ta "make a directory [RW]"
 210 .It MODE Ta "specify data transfer" Em mode
 211 .It NLST Ta "give name list of files in directory"
 212 .It NOOP Ta "do nothing"
 213 .It PASS Ta "specify password"
 214 .It PASV Ta "prepare for server-to-server transfer"
 215 .It PORT Ta "specify data connection port"
 216 .It PWD Ta "print the current working directory"
 217 .It QUIT Ta "terminate session"
 218 .It REST Ta "restart incomplete transfer"
 219 .It RETR Ta "retrieve a file"
 220 .It RMD Ta "remove a directory [RW]"
 221 .It RNFR Ta "specify rename-from file name [RW]"
 222 .It RNTO Ta "specify rename-to file name [RW]"
 223 .It SITE Ta "non-standard commands (see next section)"
 224 .It SIZE Ta "return size of file"
 225 .It STAT Ta "return status of server"
 226 .It STOR Ta "store a file [RW]"
 227 .It STOU Ta "store a file with a unique name [RW]"
 228 .It STRU Ta "specify data transfer" Em structure
 229 .It SYST Ta "show operating system type of server system"
 230 .It TYPE Ta "specify data transfer" Em type
 231 .It USER Ta "specify user name"
 232 .It XCUP Ta "change to parent of current working directory (deprecated)"
 233 .It XCWD Ta "change working directory (deprecated)"
 234 .It XMKD Ta "make a directory (deprecated) [RW]"
 235 .It XPWD Ta "print the current working directory (deprecated)"
 236 .It XRMD Ta "remove a directory (deprecated) [RW]"
 237 .El
 238 .Pp
 239 The following non-standard or
 240 .Tn UNIX
 241 specific commands are supported
 242 by the
 243 SITE request.
 244 .Pp
 245 .Bl -column Request -offset indent
 246 .It Sy Request Ta Sy Description
 247 .It UMASK Ta change umask, e.g. ``SITE UMASK 002''
 248 .It IDLE Ta set idle-timer, e.g. ``SITE IDLE 60''
 249 .It CHMOD Ta "change mode of a file [RW], e.g. ``SITE CHMOD 755 filename''"
 250 .It HELP Ta give help information
 251 .El
 252 .Pp
 253 The remaining ftp requests specified in Internet RFC 959
 254 are
 255 recognized, but not implemented.
 256 MDTM and SIZE are not specified in RFC 959, but will appear in the
 257 next updated FTP RFC.
 258 .Pp
 259 The ftp server will abort an active file transfer only when the
 260 ABOR
 261 command is preceded by a Telnet "Interrupt Process" (IP)
 262 signal and a Telnet "Synch" signal in the command Telnet stream,
 263 as described in Internet RFC 959.
 264 If a
 265 STAT
 266 command is received during a data transfer, preceded by a Telnet IP
 267 and Synch, transfer status will be returned.
 268 .Pp
 269 .Nm Ftpd
 270 interprets file names according to the
 271 .Dq globbing
 272 conventions used by
 273 .Xr csh 1 .
 274 This allows users to utilize the metacharacters
 275 .Dq Li \&*?[]{}~ .
 276 .Pp
 277 .Nm Ftpd
 278 authenticates users according to six rules.
 279 .Pp
 280 .Bl -enum -offset indent
 281 .It
 282 The login name must be in the password data base
 283 and not have a null password.
 284 In this case a password must be provided by the client before any
 285 file operations may be performed.
 286 If the user has an S/Key key, the response from a successful USER
 287 command will include an S/Key challenge.
 288 The client may choose to respond with a PASS command giving either
 289 a standard password or an S/Key one-time password.
 290 The server will automatically determine which type of
 291 password it has been given and attempt to authenticate accordingly.
 292 See
 293 .Xr key 1
 294 for more information on S/Key authentication.
 295 S/Key is a Trademark of Bellcore.
 296 .It
 297 The login name must not appear in the file
 298 .Pa /etc/ftpusers .
 299 .It
 300 The login name must not be a member of a group specified in the file
 301 .Pa /etc/ftpusers .
 302 Entries in this file interpreted as group names are prefixed by an "at"
 303 .Ql \&@
 304 sign.
 305 .It
 306 The user must have a standard shell returned by
 307 .Xr getusershell 3 .
 308 .It
 309 If the user name appears in the file
 310 .Pa /etc/ftpchroot ,
 311 or the user is a member of a group with a group entry in this file,
 312 i.e. one prefixed with
 313 .Ql \&@ ,
 314 the session's root will be changed to the user's login directory by
 315 .Xr chroot 2
 316 as for an
 317 .Dq anonymous
 318 or
 319 .Dq ftp
 320 account (see next item).
 321 This facility may also be triggered by enabling the boolean "ftp-chroot"
 322 capability in
 323 .Xr login.conf 5 .
 324 However, the user must still supply a password.
 325 This feature is intended as a compromise between a fully anonymous
 326 account and a fully privileged account.
 327 The account should also be set up as for an anonymous account.
 328 .It
 329 If the user name is
 330 .Dq anonymous
 331 or
 332 .Dq ftp ,
 333 an
 334 anonymous ftp account must be present in the password
 335 file (user
 336 .Dq ftp ) .
 337 In this case the user is allowed
 338 to log in by specifying any password (by convention an email address for
 339 the user should be used as the password).
 340 When the
 341 .Fl S
 342 option is set, all transfers are logged as well.
 343 .El
 344 .Pp
 345 In the last case,
 346 .Nm
 347 takes special measures to restrict the client's access privileges.
 348 The server performs a
 349 .Xr chroot 2
 350 to the home directory of the
 351 .Dq ftp
 352 user.
 353 In order that system security is not breached, it is recommended
 354 that the
 355 .Dq ftp
 356 subtree be constructed with care, following these rules:
 357 .Bl -tag -width "~ftp/pub" -offset indent
 358 .It Pa ~ftp
 359 Make the home directory owned by
 360 .Dq root
 361 and unwritable by anyone.
 362 .It Pa ~ftp/etc
 363 Make this directory owned by
 364 .Dq root
 365 and unwritable by anyone (mode 555).
 366 The files pwd.db (see
 367 .Xr passwd 5 )
 368 and
 369 .Xr group 5
 370 must be present for the
 371 .Xr ls
 372 command to be able to produce owner names rather than numbers.
 373 The password field in
 374 .Xr passwd
 375 is not used, and should not contain real passwords.
 376 The file
 377 .Pa ftpmotd ,
 378 if present, will be printed after a successful login.
 379 These files should be mode 444.
 380 .It Pa ~ftp/pub
 381 Make this directory mode 777 and owned by
 382 .Dq ftp .
 383 Guests
 384 can then place files which are to be accessible via the anonymous
 385 account in this directory.
 386 .El
 387 .Pp
 388 If the system has multiple IP addresses,
 389 .Nm
 390 supports the idea of virtual hosts, which provides the ability to
 391 define multiple anonymous ftp areas, each one allocated to a different
 392 internet address.
 393 The file
 394 .Pa /etc/ftphosts
 395 contains information pertaining to each of the virtual hosts.
 396 Each host is defined on its own line which contains a number of
 397 fields separated by whitespace:
 398 .Bl -tag -offset indent -width hostname
 399 .It hostname
 400 Contains the hostname or IP address of the virtual host.
 401 .It user
 402 Contains a user record in the system password file.
 403 As with normal anonymous ftp, this user's access uid, gid and group
 404 memberships determine file access to the anonymous ftp area.
 405 The anonymous ftp area (to which any user is chrooted on login)
 406 is determined by the home directory defined for the account.
 407 User id and group for any ftp account may be the same as for the
 408 standard ftp user.
 409 .It statfile
 410 File to which all file transfers are logged, which
 411 defaults to
 412 .Pa /var/log/ftpd .
 413 .It welcome
 414 This file is the welcome message displayed before the server ready
 415 prompt.
 416 It defaults to
 417 .Pa /etc/ftpwelcome .
 418 .It motd
 419 This file is displayed after the user logs in.
 420 It defaults to
 421 .Pa /etc/ftpmotd .
 422 .El
 423 .Pp
 424 Lines beginning with a '#' are ignored and can be used to include
 425 comments.
 426 .Pp
 427 Defining a virtual host for the primary IP address or hostname
 428 changes the default for ftp logins to that address.
 429 The 'user', 'statfile', 'welcome' and 'motd' fields may be left
 430 blank, or a single hypen '-' used to indicate that the default
 431 value is to be used.
 432 .Pp
 433 As with any anonymous login configuration, due care must be given
 434 to setup and maintenance to guard against security related problems.
 435 .Pp
 436 .Nm
 437 has internal support for handling remote requests to list
 438 files, and will not execute
 439 .Pa /bin/ls
 440 in either a chrooted or non-chrooted environment.  The
 441 .Pa ~/bin/ls
 442 executable need not be placed into the chrooted tree, nor need the
 443 .Pa ~/bin
 444 directory exist.
 445 .Sh FILES
 446 .Bl -tag -width /etc/ftpwelcome -compact
 447 .It Pa /etc/ftpusers
 448 List of unwelcome/restricted users.
 449 .It Pa /etc/ftpchroot
 450 List of normal users who should be chroot'd.
 451 .It Pa /etc/ftphosts
 452 Virtual hosting configuration file.
 453 .It Pa /etc/ftpwelcome
 454 Welcome notice.
 455 .It Pa /etc/ftpmotd
 456 Welcome notice after login.
 457 .It Pa /var/run/nologin
 458 Displayed and access refused.
 459 .It Pa /var/log/ftpd
 460 Log file for anonymous transfers.
 461 .El
 462 .Sh SEE ALSO
 463 .Xr ftp 1 ,
 464 .Xr key 1 ,
 465 .Xr getusershell 3 ,
 466 .Xr login.conf 5 ,
 467 .Xr inetd 8 ,
 468 .Xr syslogd 8
 469 .Sh BUGS
 470 The server must run as the super-user
 471 to create sockets with privileged port numbers.  It maintains
 472 an effective user id of the logged in user, reverting to
 473 the super-user only when binding addresses to sockets.  The
 474 possible security holes have been extensively
 475 scrutinized, but are possibly incomplete.
 476 .Sh HISTORY
 477 The
 478 .Nm
 479 command appeared in
 480 .Bx 4.2 .
 481 IPv6 support was added in WIDE Hydrangea IPv6 stack kit.