SunOS man pages : in.ftpd (1)
Maintenance Commands in.ftpd(1M)
NAME
in.ftpd, ftpd - file transfer protocol server
SYNOPSIS
in.ftpd [ -dl ] [ -t timeout ]
DESCRIPTION
in.ftpd is the Internet File Transfer Protocol ( FTP )
server process. The server is invoked by the Internet daemon
inetd(1M) each time a connection to the FTP service (see
services(4)) is made.
OPTIONS
-d Debugging information is logged to the system log dae-
mon syslogd(1M).
-l Each FTP session is logged to the system log daemon
syslogd(1M).
-t timeout
Set the inactivity timeout period to timeout seconds.
The FTP server will timeout an inactive session after
15 minutes.
Requests
The FTP server currently supports the following FTP
requests; case is not distinguished.
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 -lg)
MKD make a directory
MODE specify data transfer mode
NLST give name list of files in directory (ls)
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NOOP do nothing
PASS specify password
PASV prepare for server-to-server transfer
EPSV extended passive command request
LPSV long passive command request
PORT specify data connection port
EPRT specify extended address for the transport connection
LPRT specify "long" address for the transport connection
PWD print the current working directory
QUIT terminate session
RETR retrieve a file
RMD remove a directory
RNFR specify rename-from file name
RNTO specify rename-to file name
STOR store a file
STOU store a file with a unique name
STRU specify data transfer structure
TYPE specify data transfer type
USER specify user name
XCUP change to parent of current working directory
XCWD change working directory
XMKD make a directory
XPWD print the current working directory
XRMD remove a directory
The remaining FTP requests specified in RFC 959 are recog-
nized, but not implemented.
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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 Tel-
net stream, as described in RFC 959.in.ftpd interprets file
names according to the "globbing" conventions used by sh(1).
This allows users to utilize the metacharacters: * ? [ ] {
} ~ in.ftpd's umask (which it uses to create files during
PUT operations) may be adjusted by adding the line
UMASK=nnn
to /etc/default/ftpd.
The banner returned by in.ftpd in the parenthetical portion
of its greeting is configurable. The default is equivalent
to "`uname -sr`" and will be used if no banner is set in
/etc/default/ftpd. To set the banner, add a line of the form
BANNER="..."
to /etc/default/ftpd. Nonempty banner strings are fed to
shells for evaluation.
The default banner may also be obtained by
BANNER="`uname -s` `uname -r`"
and no banner will be printed if /etc/default/ftpd contains
BANNER="
in.ftpd authenticates users according to four rules.
First, the user name must be in the password data base,
/etc/passwd, and have a password that is not NULL. A pass-
word must always be provided by the client before any file
operations may be performed. The PAM framework (see SECU-
RITY below) is used to verify that the correct password was
entered.
Second, if the user name appears in the file /etc/ftpusers,
ftp access is denied. The default list of users in
/etc/ftpusers includes all of the accounts in passwd(4). See
ftpusers(4).
Third, ftp access is denied if the user's shell is not a
shell listed in getusershell(3C).
Fourth, if the user name is "anonymous" or "ftp", an entry
for the user name ftp must be present in the password and
shadow files. The user is then allowed to log in by
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specifying any password - by convention this is given as the
user's e-mail address (such as user@host.Sun.COM). Do not
specify a valid shell in the password entry of the ftp user,
and do not give it a valid password (use NP in the encrypted
password field of the shadow file).
For anonymous ftp users, in.ftpd takes special measures to
restrict the client's access privileges. The server performs
a chroot(2) command to the home directory of the "ftp" user.
In order that system security is not breached, it is recom-
mended that the "ftp" subtree be constructed with care; the
following rules are suggested.
~ftp Make the home directory owned by root and unwritable
by anyone.
~ftp/bin
Make this directory owned by the superuser and unwrit-
able by anyone. Make this a symbolic link to
~ftp/usr/bin The program ls(1) must be present to sup-
port the list commands. This program should have mode
111.
~ftp/usr/lib
Make this directory owned by the superuser and unwrit-
able by anyone. Copy the following shared libraries
from /usr/lib into this directory:
ld.so.1*
libc.so.1*
libdl.so.1*
libmp.so.2*
libnsl.so.1*
libsocket.so.1*
nss_compat.so.1*
nss_dns.so.1*
nss_files.so.1*
nss_nis.so.1*
nss_nisplus.so.1*
nss_xfn.so.1*
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straddr.so*
straddr.so.2*
~ftp/etc
Make this directory owned by the superuser and unwrit-
able by anyone. Copies of the files passwd(4),
group(4), and netconfig(4) must be present for the
ls(1) command to work properly. These files should be
mode 444.
~ftp/pub
Make this directory mode 755 and owned by root. Users
should then place files which are to be accessible via
the anonymous account in this directory.
~ftp/dev
Make this directory owned by the superuser and unwrit-
able by anyone. First perform ls -lL on the device
files listed below to determine their major and minor
numbers, then use mknod to create them in this direc-
tory.
/dev/zero
/dev/tcp
/dev/udp
/dev/ticotsord
Set the read and write mode on these nodes to 666 so
that passive
ftp will not fail with "permission denied" errors.
~ftp/usr/share/lib/zoneinfo
Make this directory mode 555 and owned by the
superuser. Copy its contents from
/usr/share/lib/zoneinfo. This enables ls -l to
display time and date stamps correctly.
SECURITY
in.ftpd uses pam(3PAM) for authentication, account manage-
ment, and session management. The PAM configuration policy,
listed through /etc/pam.conf, specifies the module to be
used for in.ftpd. Here is a partial pam.conf file with
entries for the in.ftpd command using the UNIX authentica-
tion, account management, and session management module.
ftp auth required /usr/lib/security/pam_unix.so.1
ftp account required /usr/lib/security/pam_unix.so.1
ftp session required /usr/lib/security/pam_unix.so.1
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If there are no entries for the ftp service, then the
entries for the "other" service will be used. Unlike login,
passwd, and other commands, the ftp protocol will only sup-
port a single password. Using multiple modules will prevent
in.ftpd from working properly.
USAGE
The in.ftpd command is IPv6-enabled. See ip6(7P).
EXAMPLES
Example 1: Setting Up An Anonymous Ftp
To set up anonymous ftp, add the following entry to the
/etc/passwd file. In this example, /export/ftp was chosen to
be the anonymous ftp area, and the shell is the non-existent
file /nosuchshell. This prevents users from logging in as
the ftp user.
ftp:x:30000:30000:Anonymous FTP:/export/ftp:/nosuchshell
Add the following entry to the /etc/shadow file:
ftp:NP:6445::::::
The following shell script sets up the anonymous ftp area.
It presumes that names are resolved using NIS.
#!/bin/sh
# script to setup anonymous ftp area
#
# verify you are root
/usr/bin/id | grep -w 'uid=0' >/dev/null 2>&1
if [ "$?" != "0" ]; then
echo
exit 1
fi
# handle the optional command line argument
case $# in
# the default location for the anon ftp comes from the passwd file
0) ftphome="`getent passwd ftp | cut -d: -f6`"
;;
1) if [ "$1" = "start" ]; then
ftphome="`getent passwd ftp | cut -d: -f6`"
else
ftphome=$1
fi
;;
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*) echo "Usage: $0 [anon-ftp-root]"
exit 1
;;
esac
if [ -z "${ftphome}" ]; then
echo "$0: ftphome must be non-null"
exit 2
fi
case ${ftphome} in
/*) # ok
;;
*) echo "$0: ftphome must be an absolute pathname"
exit 1
;;
esac
# This script assumes that ftphome is neither / nor /usr so ...
if [ -z "${ftphome}" -o "${ftphome}" = "/" -o "${ftphome}" = "/usr" ]; then
echo "$0: ftphome must be non-null and neither / or /usr"
exit 2
fi
# If ftphome does not exist but parent does, create ftphome
if [ ! -d ${ftphome} ]; then
# lack of -p below is intentional
mkdir ${ftphome}
fi
chown root ${ftphome}
chmod 555 ${ftphome}
echo Setting up anonymous ftp area ${ftphome}
# Ensure that the /usr directory exists
if [ ! -d ${ftphome}/usr ]; then
mkdir -p ${ftphome}/usr
fi
# Now set the ownership and modes to match the man page
chown root ${ftphome}/usr
chmod 555 ${ftphome}/usr
# Ensure that the /usr/bin directory exists
if [ ! -d ${ftphome}/usr/bin ]; then
mkdir -p ${ftphome}/usr/bin
fi
# Now set the ownership and modes to match the man page
chown root ${ftphome}/usr/bin
chmod 555 ${ftphome}/usr/bin
# this may not be the right thing to do
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# but we need the bin -> usr/bin link
rm -f ${ftphome}/bin
ln -s usr/bin ${ftphome}/bin
# Ensure that the /usr/lib and /etc directories exist
if [ ! -d ${ftphome}/usr/lib ]; then
mkdir -p ${ftphome}/usr/lib
fi
chown root ${ftphome}/usr/lib
chmod 555 ${ftphome}/usr/lib
if [ ! -d ${ftphome}/usr/lib/security ]; then
mkdir -p ${ftphome}/usr/lib/security
fi
chown root ${ftphome}/usr/lib/security
chmod 555 ${ftphome}/usr/lib/security
if [ ! -d ${ftphome}/etc ]; then
mkdir -p ${ftphome}/etc
fi
chown root ${ftphome}/etc
chmod 555 ${ftphome}/etc
# a list of all the commands that should be copied to ${ftphome}/usr/bin
# /usr/bin/ls is needed at a minimum.
ftpcmd="
/usr/bin/ls
"
# ${ftphome}/usr/lib needs to have all the libraries needed by the above
# commands, plus the runtime linker, and some name service libraries
# to resolve names. We just take all of them here.
ftplib="`ldd $ftpcmd | nawk '$3 ~ /lib/ { print $3 }' | sort | uniq`"
ftplib="$ftplib /usr/lib/nss_* /usr/lib/straddr* /usr/lib/libmp.so*"
ftplib="$ftplib /usr/lib/libnsl.so.1 /usr/lib/libsocket.so.1 /usr/lib/ld.so.1"
ftplib="`echo $ftplib | tr ' ' '\n' | sort | uniq`"
cp ${ftplib} ${ftphome}/usr/lib
chmod 555 ${ftphome}/usr/lib/*
cp /usr/lib/security/* ${ftphome}/usr/lib/security
chmod 555 ${ftphome}/usr/lib/security/*
cp ${ftpcmd} ${ftphome}/usr/bin
chmod 111 ${ftphome}/usr/bin/*
# you also might want to have separate minimal versions of passwd and group
cp /etc/passwd /etc/group /etc/netconfig /etc/pam.conf ${ftphome}/etc
chmod 444 ${ftphome}/etc/*
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# need /etc/default/init for timezone to be correct
if [ ! -d ${ftphome}/etc/default ]; then
mkdir ${ftphome}/etc/default
fi
chown root ${ftphome}/etc/default
chmod 555 ${ftphome}/etc/default
cp /etc/default/init ${ftphome}/etc/default
chmod 444 ${ftphome}/etc/default/init
# Copy timezone database
mkdir -p ${ftphome}/usr/share/lib/zoneinfo
(cd ${ftphome}/usr/share/lib/zoneinfo
(cd /usr/share/lib/zoneinfo; find . -print |
cpio -o) 2>/dev/null | cpio -imdu 2>/dev/null
find . -print | xargs chmod 555
find . -print | xargs chown root
)
# Ensure that the /dev directory exists
if [ ! -d ${ftphome}/dev ]; then
mkdir -p ${ftphome}/dev
fi
# make device nodes. ticotsord and udp are necessary for
# 'ls' to resolve NIS names.
for device in zero tcp udp ticotsord ticlts
do
line=`ls -lL /dev/${device} | sed -e 's/,//'`
major=`echo $line | awk '{print $5}'`
minor=`echo $line | awk '{print $6}'`
rm -f ${ftphome}/dev/${device}
mknod ${ftphome}/dev/${device} c ${major} ${minor}
done
chmod 666 ${ftphome}/dev/*
## Now set the ownership and modes
chown root ${ftphome}/dev
chmod 555 ${ftphome}/dev
# uncomment the below if you want a place for people to store things,
# but beware the security implications
#if [ ! -d ${ftphome}/pub ]; then
# mkdir -p ${ftphome}/pub
#fi
#chown root ${ftphome}/pub
#chmod 1755 ${ftphome}/pub
After running this script, edit the files in ~ftp/etc to
make sure all non-public information is removed.
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ATTRIBUTES
See attributes (5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
FILES
/etc/default/ftpd
/etc/ftpusers
file listing users for whom ftp login privileges are
disallowed.
SEE ALSO
ftp(1), ld.so.1(1), ls(1), sh(1), aset(1M), inetd( 1M),
mknod(1M), syslogd(1M), chroot(2), getsockopt(3SOCKET),
pam(3PAM), ftpusers(4), group(4), inetd.conf(4), netconfig(4)
, netrc(4), pam.conf(4), passwd(4), services(4),
attributes(5), pam_unix(5)
Allman, M., Ostermann, S., and Metz, C., RFC 2428, FTP
Extensions for IPv6 and NATs, The Internet Society, 1998.
Postel, Jon, and Joyce Reynolds, RFC 959, File Transfer
Protocol (FTP ), Network Information Center, SRI Interna-
tional, Menlo Park, Calif., October 1985.
Piscitello, D., RFC 1639, FTP Operation Over Big Address
Records (FOOBAR), Network Working Group, June 1994.
DIAGNOSTICS
in.ftpd logs various errors to syslogd, with a facility code
of daemon.
Info Severity
These messages are logged only if the -l flag is specified.
FTPD: connection from host at time
A connection was made to ftpd from the host host at
the date and time time.
FTPD: User user timed out after timeout seconds
at time" 6 The user user was logged out because they
had not entered any commands after timeout seconds;
the logout occurred at the date and time time.
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Debug Severity
These messages are logged only if the -d flag is specified.
FTPD: command: command
A command line containing command was read from the
FTP client.
lost connection
The FTP client dropped the connection.
<--- replycode
<--- replycode-
A reply was sent to the FTP client with the reply code
replycode. The next message logged will include the
message associated with the reply. If a - follows the
reply code, the reply is continued on later lines.
NOTES
The anonymous ftp account is inherently dangerous and should
be avoided when possible.
The name service caching daemon /usr/sbin/nscd may interfere
with some of the functionality of anonymous ftp. The sublo-
gin feature does not work unless caching for passwd is dis-
abled in /etc/nscd.conf.
The server must run as the superuser to create sockets with
privileged port numbers. It maintains an effective user id
of the logged in user, reverting to the superuser only when
binding addresses to sockets. The possible security holes
have been extensively scrutinized, but are possibly incom-
plete.
The file /etc/ftpusers, which is now included as part of
Solaris, contains a list of users who cannot access the
system; the default list of users in /etc/ftpusers includes
all of the accounts in passwd(4). See ftpusers(4).
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