in.ftpd(1MTSOL) (Man Pages (1MTSOL): Maintenance and Administration Commands)

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NAME

in.ftpd, ftpd - File-transfer protocol server

SYNOPSIS

in.ftpd [ -dl ] [ -t timeout ]

AVAILABILITY

SUNWcsu

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 daemon 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 these 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: List files in a directory. (ls -lg)

MKD: Make a directory.

MODE: Specify data transfer mode.

NLST: List names of files in directory (ls).

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.

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 recognized but not implemented.

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 RFC 959.

in.ftpd interprets file names according to the "globbing" conventions used by sh(1). This interpretation allows users to utilize these metacharacters: * ? [ ] { } ~

in.ftpd authenticates users according to five rules.

1): The user name must be in the password data base, /etc/passwd, and have a password that is not null. A password must always be provided by the client before any file operations may be performed.

2): If the user name appears in the file /etc/ftpusers, ftp access is denied.

3): ftp access is denied if the user's shell (from /etc/passwd) is not listed in the file /etc/shells. If the file /etc/shells does not exist, then the user's shell must be one of the following:

    /usr/bin/sh /usr/bin/csh /usr/bin/ksh
    /usr/bin/jsh /bin/sh      /bin/csh
    /bin/ksh    /bin/jsh      /sbin/sh
    /sbin/jsh

4): 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 specifying any password--by convention this password 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 that entry a valid password (use NP in the encrypted password field of the shadow file).

5): Access is denied unless a user has the remote login authorization. If the /etc/nologin file exists, access is denied.

For anonymous FTP users, in.ftpd takes special measures to restrict the client's access privileges. The server performs a chroot(2TSOL) command 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; the following rules are suggested.

~ftp: Make the home directory owned by root and unwritable by anyone. This directory should not be on a file system mounted with the nosuid option.

~ftp/bin: Make this directory owned by the super-user and unwritable by anyone. Make this a symbolic link to ~ftp/usr/bin. The program ls(1) must be present to support the list commands. This program should have mode 111.

~ftp/usr/lib: Make this directory owned by the super-user and unwritable by anyone. Copy these shared libraries from /usr/lib into this directory:

ld.so*

libc.so*

libdl.so*

                libintl.so*
                libw.so*
                libnsl.so*
                libsocket.so*
                nss_nis.so*
                nss_nisplus.so*
                nss_dns.so*
                nss_files.so*
                straddr.so*

~ftp/etc: Make this directory owned by the super-user and unwritable 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 777 and owned by ftp. Users should then place in this directory files that are to be accessible via the anonymous account.

~ftp/dev: Make this directory owned by the super-user and unwritable by anyone. First perform ls -lL on the device files listed to determine their major and minor numbers; then use mknod to create them in this directory:

/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 super-user. Copy its

contents from /usr/share/lib/zoneinfo. This setup enables ls -l to display time and date stamps correctly.

EXAMPLES

To set up anonymous ftp, add the following entry to the /etc/passwd file. In this case, /export/ftp was chosen to be the anonymous FTP area, and the shell is the nonexistent file /nosuchshell. This setup prevents users from logging in as the ftp user.

ftp:x:30000:30000:Anonymous FTP:/export/ftp:/nosuchshell

Add the following entry to /etc/shadow:

ftp:NP:6445::::::

The following shell script will set up the anonymous FTP area. The shell script assumes that names are resolved using NIS.

#!/bin/sh
# script to setup anonymous ftp area
#
# handle the optional command line argument
case $# in

# the default location for the anon ftp comes from the passwd file

 0) ftphome="`grep '^ftp:' /etc/passwd | cut -d: -f6`"
   ;;

1) if [ "$1" = "start" ]; then

     ftphome="`grep '^ftp:' /etc/passwd | cut -d: -f6`"
   else
     ftphome=$1
   fi
   ;;

* )echo "Usage: $0 [anon-ftp-root]"

   exit 1
   ;;
esac

if [ -z "${ftphome}" ]; then

 echo "$0: ftphome must be non-null"
 exit 2
fi

# This script assumes that ftphome is neither / nor /usr so ...

if [ "${ftphome}" = "/" -o "${ftphome}" = "/usr" ]; then
 echo "$0: ftphome must not be / 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}

echo Setting up anonymous ftp area ${ftphome}

# Ensure that the /usr/bin directory exists

if [ ! -d ${ftphome}/usr/bin ]; then
  mkdir -p ${ftphome}/usr/bin
fi

cp /usr/bin/ls ${ftphome}/usr/bin

chmod 111 ${ftphome}/usr/bin/ls

# 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

# but we need the bin -> usr/bin link
if [ -r ${ftphome}/bin ]; then
  mv -f ${ftphome}/bin ${ftphome}/Obin
fi
ln -s usr/bin ${ftphome}

# Ensure that the /usr/lib and /etc directories exist

if [ ! -d ${ftphome}/usr/lib ]; then
  mkdir -p ${ftphome}/usr/lib
fi
if [ ! -d ${ftphome}/etc ]; then
  mkdir -p ${ftphome}/etc
fi

#Most of the following are needed for basic operation, except

#for libnsl.so, nss_nis.so, libsocket.so, and straddr.so which are
#needed to resolve NIS names.

cp /usr/lib/ld.so /usr/lib/ld.so.1 ${ftphome}/usr/lib

for lib in libc libdl libintl libw libnsl libsocket \

 nss_nis nss_nisplus nss_dns nss_files
do
 cp /usr/lib/${lib}.so.1 ${ftphome}/usr/lib
 rm -f ${ftphome}/usr/lib/${lib}.so
 ln -s ./${lib}.so.1 ${ftphome}/usr/lib/${lib}.so
done

cp /usr/lib/straddr.so.2 ${ftphome}/usr/lib

rm -f ${ftphome}/usr/lib/straddr.so
ln -s ./straddr.so.2 ${ftphome}/usr/lib/straddr.so

cp /etc/passwd /etc/group /etc/netconfig ${ftphome}/etc

# 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) | cpio -imdu
 find . -print | xargs chmod 555
 find . -print | xargs chown root
)

chmod 555 ${ftphome}/usr/lib/*

chmod 444 ${ftphome}/etc/*

# Now set the ownership and modes

chown root ${ftphome}/usr/lib ${ftphome}/etc
chmod 555 ${ftphome}/usr/lib ${ftphome}/etc

# 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

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

if [ ! -d ${ftphome}/pub ]; then

 mkdir -p ${ftphome}/pub
fi
chown ftp ${ftphome}/pub
chmod 777 ${ftphome}/pub

SUMMARY OF TRUSTED

Login is not allowed unless the user has the remote login authorization. If the /etc/nologin file exists, the user is not allowed to login.

SOLARIS CHANGES

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: The user user was logged out because the user had not

entered any commands after timeout seconds; the logout

occurred at the date and time time.

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 account is inherently dangerous and should be avoided when possible.

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.

/etc/ftpusers contains a list of users who cannot access the system; the format of the file is one user name per line.

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