SOCKD(8)

NAME
sockd - Internet firewall secure socket server (proxy server)

SYNOPSIS
sockd [ -ver | -i | -I ]

DESCRIPTION
sockd is an internet secure socket server, often referred to as a proxy server. It was designed primarily to provide hosts within a firewall access to resources outside of the firewall. Normally, hosts inside a firewall has no IP-accessibility to the network outside of the firewall. This reduces the risk of being intruded by unauthorized people from the Internet. Unfortunately, without IP-accessibility users on the inside hosts can no longer use many of the important tools such as telnet, ftp, xgopher, Mosaic, etc. to access the tremendous resources available in the Internet. With sockd installed on a server host, users on the other inside hosts can gain back the lost functionalities by using clients programs designed to work with sockd proxy server, e.g, rtelnet in place of telnet, rftp in place of ftp, rfinger in place of finger, etc. Since these client programs work like their normal counterparts without requiring direct IP-accessibility to the Internet, convenience to the users is accomplished without breaching the security. The server host that runs sockd does have to be open to the Internet, and it therefore requires special attention to make sure that it is secure. A configuration file /etc/sockd.conf is used to control access to sockd and its services. Permission and denial of a service request can be decided based on various combinations of the requesting host, the destination host, the type of service (destination port number), as well as the requesting user. (See sockd.conf(5).) If the server host is multi-homed, i.e., having more than one network interface and with its IP_FORWARDING turned off, it must run a multi-homed version of sockd, which requires another control file /etc/sockd.route to decide which interface to use for connection to any given destination host. See sockd.route(5). A multi-homed sockd can be run on a single-homed host as well if necessary; you just have to set up /etc/sockd.route to direct all traffic through the host's one and only network interface. sockd uses syslog with facility daemon and level notice to log its activities and errors. Typical lines look like
Apr 11 08:51:29 eon sockd[636]: connected -- Connect from don(don)@abc.edu to wxy.com (telnet)
Apr 11 09:24:59 eon sockd[636]: terminated -- Connect from don(don)@abc.edu to wxy.com (telnet)
Apr 11 09:24:59 eon sockd[636]: 1048 bytes from abc.edu, 285143 bytes from wxy.com
Jun 22 18:24:54 eon sockd[884]: refused -- Connect from sam(unknown)@big.com to small.com (ftp)
In these lines, the first user-id is the one reported by the client program, the second one (within the parentheses) is what is reported by identd on the client host. These log lines usually appear in file /var/adm/messages though that can be changed by modifying /etc/syslog.conf. (See syslogd(8) and syslog.conf(5).) If you allow access to infosystems such as Gopher or WWW, you should be aware that they by nature would tend to get connections to hosts all over the world and would use not only Gopher and WWW ports but possibly also ports for finger, telnet, ftp, nntp, etc. as well as non-privileged ports ( > 1023). For a stand-alone sockd, /etc/sockd.conf and /etc/sockd.route (if required) are only read and parsed once at the beginning of program execution. If you change the contents of either file and want to make the running sockd use the new contents, you must send a SIGHUP signal to the running sockd process. Sending a running stand-alone sockd a SIGUSR1 signal causes it to record the effective contents of sockd.conf and sockd.route that it is currently using on the system's log file. You can find the process id of the stand-alone sockd in /tmp/sockd.pid.

OPTIONS
The options are mutually exclusive and thus may only be used one at a time.

With this option, sockd prints its own version number,
    whether it is a single-homed or multi-homed version, whether it should be run stand-alone or under the control of inetd, and whether it supports clients that use Rrcmd(), and then quits.

Use identd (RFC 1413) to verify the requester's user-id. Deny access if
    connection to client's identd fails or if the result does not match the user-id reported by the client program. Client hosts without a properly installed identd daemon will not be served. User verification is done before and in addition to the normal access control. This can be overridden in the sockd.conf file on a line by line basis.

Similar to -I but more lenient. Access is denied only if client's
    identd reports a user-id that's different from what the client program claims. This can be overridden in the sockd.conf file on a line by line basis.

Log entries similar to the following are produced upon failure of user-id verification:
Apr 15 14:42:51 eon sockd[729]: cannot connect to identd on big.edu
Apr 15 14:42:51 eon sockd[729]: refused -- Connect from bob(unknown)@big.edu to xyz.com (ftp)
Jul 15 12:23:06 eon sockd[832]: *Alert*: real user is sam, not jim
Jul 15 12:23:06 eon sockd[832]: refused -- Connect from jim(sam)@abc.org to bad.place.com (WWW)

FILES
/etc/sockd.conf, /etc/inetd.conf, /etc/services, /var/adm/messages, /etc/syslog.conf

SEE ALSO
socks_clients(1), test_sockd_conf(8), sockd.conf(5), sockd.route(5), socks.conf(5)

AUTHOR
David Koblas, koblas@sgi.com
Ying-Da Lee, ylee@syl.dl.nec.com
David Mischel, dm@kansas.gene.com