NAME¶
ftpd
—
Internet File Transfer Protocol server
SYNOPSIS¶
ftpd |
[ -a
authmode ]
[-dilvU ]
[-g
umask ]
[-p
port ]
[-T
maxtimeout ]
[-t
timeout ]
[- -gss-bindings ]
[-I |
- -no-insecure-oob ]
[-u
default umask ]
[-B |
- -builtin-ls ]
[- -good-chars= string ] |
DESCRIPTION¶
Ftpd
is the Internet File Transfer Protocol
server process. The server uses the TCP protocol and listens at the port
specified in the “ftp” service specification; see
services(5).
Available options:
-a
- Select the level of authentication required. Kerberised login can not be
turned off. The default is to only allow kerberised login. Other
possibilities can be turned on by giving a string of comma separated flags
as argument to
-a
. Recognised flags
are:
- plain
- Allow logging in with plaintext password. The password can be a(n) OTP
or an ordinary password.
- otp
- Same as plain, but only OTP is
allowed.
- ftp
- Allow anonymous login.
The following combination modes exists for backwards compatibility:
- none
- Same as plain,ftp.
- safe
- Same as ftp.
- user
- Ignored.
-d
- Debugging information is written to the syslog using LOG_FTP.
-g
- Anonymous users will get a umask of
umask.
-
-gss-bindings
- require the peer to use GSS-API bindings (ie make sure IP addresses
match).
-i
- Open a socket and wait for a connection. This is mainly used for debugging
when ftpd isn't started by inetd.
-l
- Each successful and failed ftp(1) session is
logged using syslog with a facility of LOG_FTP. If this option is
specified twice, the retrieve (get), store (put), append, delete, make
directory, remove directory and rename operations and their filename
arguments are also logged.
-p
- Use port (a service name or number)
instead of the default ftp/tcp.
-T
- A client may also request a different timeout period; the maximum period
allowed may be set to timeout seconds
with the
-T
option. The default limit
is 2 hours.
-t
- The inactivity timeout period is set to
timeout seconds (the default is 15
minutes).
-u
- Set the initial umask to something else than the default 027.
-U
- In previous versions of
ftpd
, when a
passive mode client requested a data connection to the server, the server
would use data ports in the range 1024..4999. Now, by default, if the
system supports the IP_PORTRANGE socket option, the server will use data
ports in the range 49152..65535. Specifying this option will revert to the
old behavior.
-v
- Verbose mode.
-B
,
-
-builtin-ls
- use built-in ls to list files
-
-good-chars=
string
- allowed anonymous upload filename chars
-I
-
-no-insecure-oob
- don't allow insecure out of band. Heimdal ftp clients before 0.6.3 doesn't
support secure oob, so turning on this option makes them no longer
work.
The file
/etc/nologin can be used to disable
ftp access. If the file exists,
ftpd
displays it and exits. If the file
/etc/ftpwelcome exists,
ftpd
prints it before issuing the
“ready” message. If the file
/etc/motd exists,
ftpd
prints it after a successful login.
The ftp server currently supports the following ftp requests. The case of the
requests is ignored.
Request |
Description |
ABOR |
abort previous command |
ACCT |
specify account (ignored) |
ALLO |
allocate storage (vacuously) |
APPE |
append to a file |
CDUP |
change to parent of current working directory |
CWD |
change working directory |
DELE |
delete a file |
HELP |
give help information |
LIST |
give list files in a directory (“ls
-lgA ”) |
MKD |
make a directory |
MDTM |
show last modification time of file |
MODE |
specify data transfer mode |
NLST |
give name list of files in directory |
NOOP |
do nothing |
PASS |
specify password |
PASV |
prepare for server-to-server transfer |
PORT |
specify data connection port |
PWD |
print the current working directory |
QUIT |
terminate session |
REST |
restart incomplete transfer |
RETR |
retrieve a file |
RMD |
remove a directory |
RNFR |
specify rename-from file name |
RNTO |
specify rename-to file name |
SITE |
non-standard commands (see next section) |
SIZE |
return size of file |
STAT |
return status of server |
STOR |
store a file |
STOU |
store a file with a unique name |
STRU |
specify data transfer structure |
SYST |
show operating system type of server system |
TYPE |
specify data transfer type |
USER |
specify user name |
XCUP |
change to parent of current working directory (deprecated) |
XCWD |
change working directory (deprecated) |
XMKD |
make a directory (deprecated) |
XPWD |
print the current working directory (deprecated) |
XRMD |
remove a directory (deprecated) |
The following commands are specified by RFC2228.
AUTH |
authentication/security mechanism |
ADAT |
authentication/security data |
PROT |
data channel protection level |
PBSZ |
protection buffer size |
MIC |
integrity protected command |
CONF |
confidentiality protected command |
ENC |
privacy protected command |
CCC |
clear command channel |
The following non-standard or UNIX specific commands are supported by the SITE
request.
UMASK |
change umask, (e.g. SITE UMASK
002 ) |
IDLE |
set idle-timer, (e.g. SITE IDLE
60 ) |
CHMOD |
change mode of a file (e.g. SITE CHMOD 755
filename ) |
FIND |
quickly find a specific file with GNU
locate(1). |
HELP |
give help information. |
The following Kerberos related site commands are understood.
KAUTH |
obtain remote tickets. |
KLIST |
show remote tickets |
The remaining ftp requests specified in Internet RFC 959 are recognized, but not
implemented. MDTM and SIZE are not specified in RFC 959, but will appear in
the next updated FTP RFC.
The ftp server will abort an active file transfer only when the ABOR command is
preceded by a Telnet "Interrupt Process" (IP) signal and a Telnet
"Synch" signal in the command Telnet stream, as described in
Internet RFC 959. If a STAT command is received during a data transfer,
preceded by a Telnet IP and Synch, transfer status will be returned.
Ftpd
interprets file names according to the
“globbing” conventions used by
csh(1). This allows users to use the
metacharacters “
*?[]{}~
”.
Ftpd
authenticates users according to these
rules.
- If Kerberos authentication is used, the user must pass valid tickets and
the principal must be allowed to login as the remote user.
- The login name must be in the password data base, and not have a null
password (if Kerberos is used the password field is not checked). In this
case a password must be provided by the client before any file operations
may be performed. If the user has an OTP key, the response from a
successful USER command will include an OTP challenge. The client may
choose to respond with a PASS command giving either a standard password or
an OTP one-time password. The server will automatically determine which
type of password it has been given and attempt to authenticate
accordingly. See otp(1) for more information
on OTP authentication.
- The login name must not appear in the file
/etc/ftpusers.
- The user must have a standard shell returned by
getusershell(3).
- If the user name appears in the file
/etc/ftpchroot the session's root will
be changed to the user's login directory by
chroot(2) as for an “anonymous”
or “ftp” account (see next item). However, the user must
still supply a password. This feature is intended as a compromise between
a fully anonymous account and a fully privileged account. The account
should also be set up as for an anonymous account.
- If the user name is “anonymous” or “ftp”, an
anonymous ftp account must be present in the password file (user
“ftp”). In this case the user is allowed to log in by
specifying any password (by convention an email address for the user
should be used as the password).
In the last case,
ftpd
takes special measures
to restrict the client's access privileges. The server performs a
chroot(2) to the home directory of the
“ftp” user. In order that system security is not breached, it is
recommended that the “ftp” subtree be constructed with care,
consider following these guidelines for anonymous ftp.
In general all files should be owned by “root”, and have non-write
permissions (644 or 755 depending on the kind of file). No files should be
owned or writable by “ftp” (possibly with exception for the
~ftp/incoming, as specified below).
- ~ftp
- The “ftp” homedirectory should be owned by root.
- ~ftp/bin
- The directory for external programs (such as
ls(1)). These programs must either be
statically linked, or you must setup an environment for dynamic linking
when running chrooted. These programs will be used if present:
- ls
- Used when listing files.
- compress
- When retrieving a filename that ends in
.Z, and that file isn't present,
ftpd
will try to find the filename
without .Z and compress it on the
fly.
- gzip
- Same as compress, just with files ending in
.gz.
- gtar
- Enables retrieval of whole directories as files ending in
.tar. Can also be combined with
compression. You must use GNU Tar (or some other that supports the
-z
and
-Z
flags).
- locate
- Will enable ``fast find'' with the
SITE
FIND
command. You must also create a
locatedb file in
~ftp/etc.
- ~ftp/etc
- If you put copies of the passwd(5) and
group(5) files here, ls will be able to
produce owner names rather than numbers. Remember to remove any passwords
from these files.
The file motd, if present, will be
printed after a successful login.
- ~ftp/dev
- Put a copy of /dev/null(7) here.
- ~ftp/pub
- Traditional place to put whatever you want to make public.
If you want guests to be able to upload files, create a
~ftp/incoming directory owned by
“root”, and group “ftp” with mode 730 (make sure
“ftp” is member of group “ftp”). The following
restrictions apply to anonymous users:
- Directories created will have mode 700.
- Uploaded files will be created with an umask of 777, if not changed with
the
-g
option.
- These command are not accessible:
DELE
,
RMD
,
RNTO
,
RNFR
, SITE
UMASK
, and SITE CHMOD
.
- Filenames must start with an alpha-numeric character, and consist of
alpha-numeric characters or any of the following:
+
(plus), -
(minus),
=
(equal), _
(underscore),
.
(period), and ,
(comma).
FILES¶
- /etc/ftpusers
- Access list for users.
- /etc/ftpchroot
- List of normal users who should be chroot'd.
- /etc/ftpwelcome
- Welcome notice.
- /etc/motd
- Welcome notice after login.
- /etc/nologin
- Displayed and access refused.
- ~/.klogin
- Login access for Kerberos.
SEE ALSO¶
ftp(1),
otp(1),
getusershell(3),
ftpusers(5),
syslogd(8)
STANDARDS¶
RFC
959
- FTP PROTOCOL SPECIFICATION
RFC
1938
- OTP Specification
RFC
2228
- FTP Security Extensions.
BUGS¶
The server must run as the super-user to create sockets with privileged port
numbers. It maintains an effective user id of the logged in user, reverting to
the super-user only when binding addresses to sockets. The possible security
holes have been extensively scrutinized, but are possibly incomplete.
HISTORY¶
The
ftpd
command appeared in
4.2BSD.