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SunOS man pages : 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) SunOS 5.8 Last change: 8 Dec 1999 1 Maintenance Commands in.ftpd(1M) 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. SunOS 5.8 Last change: 8 Dec 1999 2 Maintenance Commands in.ftpd(1M) 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 SunOS 5.8 Last change: 8 Dec 1999 3 Maintenance Commands in.ftpd(1M) 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* SunOS 5.8 Last change: 8 Dec 1999 4 Maintenance Commands in.ftpd(1M) 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 SunOS 5.8 Last change: 8 Dec 1999 5 Maintenance Commands in.ftpd(1M) 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 ;; SunOS 5.8 Last change: 8 Dec 1999 6 Maintenance Commands in.ftpd(1M) *) 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 SunOS 5.8 Last change: 8 Dec 1999 7 Maintenance Commands in.ftpd(1M) # 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/* SunOS 5.8 Last change: 8 Dec 1999 8 Maintenance Commands in.ftpd(1M) # 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. SunOS 5.8 Last change: 8 Dec 1999 9 Maintenance Commands in.ftpd(1M)

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. SunOS 5.8 Last change: 8 Dec 1999 10 Maintenance Commands in.ftpd(1M) 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). SunOS 5.8 Last change: 8 Dec 1999 11