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arpa/H27-Dec-2011-328227

libtelnet/H27-Dec-2011-5,6603,879

telnet/H03-May-2022-16,18613,665

telnetd/H03-May-2022-10,4787,292

Config.genericH A D10-Jun-199429.2 KiB831778

Makefile.inH A D08-Jul-200964 43

READMEH A D10-Jun-199422.9 KiB680532

depsH A D05-Jan-200924 21

kern.diffH A D09-Mar-19937.6 KiB309293

stty.diffH A D09-Mar-19931.5 KiB7369

telnet.stateH A D09-Mar-19932.4 KiB8171

README

1
2This is a distribution of both client and server telnet.  These programs
3have been compiled on:
4			telnet	telnetd
5	BSD 4.4		  x	  x
6	BSD 4.3 Reno	  X	  X
7	UNICOS 8.0	  X	  X
8	UNICOS 7.C	  X	  X
9	UNICOS 7.0	  X	  X
10	UNICOS 6.1	  X	  X
11	BSDI 1.0	  X	  X
12	Solaris 2.2       x       x (no linemode in server)
13	Solaris 2.3       x       x (no linemode in server)
14	SunOs 4.1.3	  X	  X (no linemode in server)
15	Ultrix 4.3	  X	  X (no linemode in server)
16	DYNIX V3.0.17.9	  X	  X (no linemode in server)
17	HP-UX 8.0	  x       x (no linemode in server)
18
19In addition, previous versions have been compiled on the following
20machines, but were not available for testing this version.
21			telnet	telnetd
22	Next1.0		  X	  X
23	UNICOS 6.0	  X	  X
24	UNICOS 5.1	  X	  X
25	UNICOS 5.0	  X	  X
26	SunOs 4.0.3c	  X	  X (no linemode in server)
27	BSD 4.3		  X  	  X (no linemode in server)
28	DYNIX V3.0.12	  X	  X (no linemode in server)
29	Ultrix 3.1	  X	  X (no linemode in server)
30	Ultrix 4.0	  X	  X (no linemode in server)
31	SunOs 3.5	  X	  X (no linemode in server)
32
33This code should work, but there are no guarantees.
34
35January 19, 1994
36
37This is a list of some of the changes since the last tar release
38of telnet/telnetd.  There are probably other changes that aren't
39listed here, but this should hit a lot of the main ones.
40
41   General:
42	Changed #define for AUTHENTICATE to AUTHENTICATION
43	Changed #define for ENCRYPT to ENCRYPTION
44	Changed #define for DES_ENCRYPT to DES_ENCRYPTION
45
46	Added support for SPX authentication: -DSPX
47
48	Added support for Kerberos Version 5 authentication: -DKRB5
49
50	Added support for ANSI C function prototypes
51
52	Added support for the NEW-ENVIRON option (RFC-1572)
53	including support for USERVAR.
54
55	Made support for the old Environment Option (RFC-1408)
56	conditional on -DOLD_ENVIRON
57
58	Added #define ENV_HACK - support for RFC 1571
59
60	The encryption code is removed from the public distributions.
61	Domestic 4.4 BSD distributions contain the encryption code.
62
63	ENV_HACK: Code to deal with systems that only implement
64		the old ENVIRON option, and have reversed definitions
65		of ENV_VAR and ENV_VAL.  Also fixes ENV processing in
66		client to handle things besides just the default set...
67
68	NO_BSD_SETJMP: UNICOS configuration for
69		UNICOS 6.1/6.0/5.1/5.0 systems.
70
71	STREAMSPTY: Use /dev/ptmx to get a clean pty.  This
72		is for SVr4 derivatives (Like Solaris)
73
74	UTMPX: For systems that have /etc/utmpx. This is for
75		SVr4 derivatives (Like Solaris)
76
77	Definitions for BSDI 1.0
78
79	Definitions for 4.3 Reno and 4.4 BSD.
80
81	Definitions for UNICOS 8.0 and UNICOS 7.C
82
83	Definitions for Solaris 2.0
84
85	Definitions for HP-UX 8.0
86
87	Latest Copyright notices from Berkeley.
88
89	FLOW-CONTROL: support for RFC-XXXx
90
91
92   Client Specific:
93
94	Fix the "send" command to not send garbage...
95
96	Fix status message for "skiprc"
97
98	Make sure to send NAWS after telnet has been suspended
99	or an external command has been run, if the window size
100	has changed.
101
102	sysV88 support.
103
104   Server Specific:
105
106	Support flowcontrol option in non-linemode servers.
107
108	-k Server supports Kludge Linemode, but will default to
109	   either single character mode or real Linemode support.
110	   The user will have to explicitly ask to switch into
111	   kludge linemode. ("stty extproc", or escape back to
112	   to telnet and say "mode line".)
113
114	-u Specify the length of the hostname field in the utmp
115	   file.  Hostname longer than this length will be put
116	   into the utmp file in dotted decimal notation, rather
117	   than putting in a truncated hostname.
118
119	-U Registered hosts only.  If a reverse hostname lookup
120	   fails, the connection will be refused.
121
122	-f/-F
123	   Allows forwarding of credentials for KRB5.
124
125Februrary 22, 1991:
126
127    Features:
128
129	This version of telnet/telnetd has support for both
130	the AUTHENTICATION and ENCRYPTION options.  The
131	AUTHENTICATION option is fairly well defined, and
132	an option number has been assigned to it.  The
133	ENCRYPTION option is still in a state of flux; an
134	option number has been assigned to, but it is still
135	subject to change.  The code is provided in this release
136	for experimental and testing purposes.
137
138	The telnet "send" command can now be used to send
139	do/dont/will/wont commands, with any telnet option
140	name.  The rules for when do/dont/will/wont are sent
141	are still followed, so just because the user requests
142	that one of these be sent doesn't mean that it will
143	be sent...
144
145	The telnet "getstatus" command no longer requires
146	that option printing be enabled to see the response
147	to the "DO STATUS" command.
148
149	A -n flag has been added to telnetd to disable
150	keepalives.
151
152	A new telnet command, "auth" has been added (if
153	AUTHENTICATE is defined).  It has four sub-commands,
154	"status", "disable", "enable" and "help".
155
156	A new telnet command, "encrypt" has been added (if
157	ENCRYPT is defined).  It has many sub-commands:
158	"enable", "type", "start", "stop", "input",
159	"-input", "output", "-output", "status", and "help".
160
161	The LOGOUT option is now supported by both telnet
162	and telnetd, a new command, "logout", was added
163	to support this.
164
165	Several new toggle options were added:
166	    "autoencrypt", "autodecrypt", "autologin", "authdebug",
167	    "encdebug", "skiprc", "verbose_encrypt"
168
169	An "rlogin" interface has been added.  If the program
170	is named "rlogin", or the "-r" flag is given, then
171	an rlogin type of interface will be used.
172		~.	Terminates the session
173		~<susp> Suspend the session
174		~^]	Escape to telnet command mode
175		~~	Pass through the ~.
176	    BUG: If you type the rlogin escape character
177		 in the middle of a line while in rlogin
178		 mode, you cannot erase it or any characters
179		 before it.  Hopefully this can be fixed
180		 in a future release...
181
182    General changes:
183
184	A "libtelnet.a" has now been created.  This libraray
185	contains code that is common to both telnet and
186	telnetd.  This is also where library routines that
187	are needed, but are not in the standard C library,
188	are placed.
189
190	The makefiles have been re-done.  All of the site
191	specific configuration information has now been put
192	into a single "Config.generic" file, in the top level
193	directory.  Changing this one file will take care of
194	all three subdirectories.  Also, to add a new/local
195	definition, a "Config.local" file may be created
196	at the top level; if that file exists, the subdirectories
197	will use that file instead of "Config.generic".
198
199	Many 1-2 line functions in commands.c have been
200	removed, and just inserted in-line, or replaced
201	with a macro.
202
203    Bug Fixes:
204
205	The non-termio code in both telnet and telnetd was
206	setting/clearing CTLECH in the sg_flags word.  This
207	was incorrect, and has been changed to set/clear the
208	LCTLECH bit in the local mode word.
209
210	The SRCRT #define has been removed.  If IP_OPTIONS
211	and IPPROTO_IP are defined on the system, then the
212	source route code is automatically enabled.
213
214	The NO_GETTYTAB #define has been removed; there
215	is a compatability routine that can be built into
216	libtelnet to achive the same results.
217
218	The server, telnetd, has been switched to use getopt()
219	for parsing the argument list.
220
221	The code for getting the input/output speeds via
222	cfgetispeed()/cfgetospeed() was still not quite
223	right in telnet.  Posix says if the ispeed is 0,
224	then it is really equal to the ospeed.
225
226	The suboption processing code in telnet now has
227	explicit checks to make sure that we received
228	the entire suboption (telnetd was already doing this).
229
230	The telnet code for processing the terminal type
231	could cause a core dump if an existing connection
232	was closed, and a new connection opened without
233	exiting telnet.
234
235	Telnetd was doing a TCSADRAIN when setting the new
236	terminal settings;  This is not good, because it means
237	that the tcsetattr() will hang waiting for output to
238	drain, and telnetd is the only one that will drain
239	the output...  The fix is to use TCSANOW which does
240	not wait.
241
242	Telnetd was improperly setting/clearing the ISTRIP
243	flag in the c_lflag field, it should be using the
244	c_iflag field.
245
246	When the child process of telnetd was opening the
247	slave side of the pty, it was re-setting the EXTPROC
248	bit too early, and some of the other initialization
249	code was wiping it out.  This would cause telnetd
250	to go out of linemode and into single character mode.
251
252	One instance of leaving linemode in telnetd forgot
253	to send a WILL ECHO to the client, the net result
254	would be that the user would see double character
255	echo.
256
257	If the MODE was being changed several times very
258	quickly, telnetd could get out of sync with the
259	state changes and the returning acks; and wind up
260	being left in the wrong state.
261
262September 14, 1990:
263
264	Switch the client to use getopt() for parsing the
265	argument list.  The 4.3Reno getopt.c is included for
266	systems that don't have getopt().
267
268	Use the posix _POSIX_VDISABLE value for what value
269	to use when disabling special characters.  If this
270	is undefined, it defaults to 0x3ff.
271
272	For non-termio systems, TIOCSETP was being used to
273	change the state of the terminal.  This causes the
274	input queue to be flushed, which we don't want.  This
275	is now changed to TIOCSETN.
276
277	Take out the "#ifdef notdef" around the code in the
278	server that generates a "sync" when the pty oputput
279	is flushed.  The potential problem is that some older
280	telnet clients may go into an infinate loop when they
281	receive a "sync", if so, the server can be compiled
282	with "NO_URGENT" defined.
283
284	Fix the client where it was setting/clearing the OPOST
285	bit in the c_lflag field, not the c_oflag field.
286
287	Fix the client where it was setting/clearing the ISTRIP
288	bit in the c_lflag field, not the c_iflag field.  (On
289	4.3Reno, this is the ECHOPRT bit in the c_lflag field.)
290	The client also had its interpretation of WILL BINARY
291	and DO BINARY reversed.
292
293	Fix a bug in client that would cause a core dump when
294	attempting to remove the last environment variable.
295
296	In the client, there were a few places were switch()
297	was being passed a character, and if it was a negative
298	value, it could get sign extended, and not match
299	the 8 bit case statements.  The fix is to and the
300	switch value with 0xff.
301
302	Add a couple more printoption() calls in the client, I
303	don't think there are any more places were a telnet
304	command can be received and not printed out when
305	"options" is on.
306
307	A new flag has been added to the client, "-a".  Currently,
308	this just causes the USER name to be sent across, in
309	the future this may be used to signify that automatic
310	authentication is requested.
311
312	The USER variable is now only sent by the client if
313	the "-a" or "-l user" options are explicity used, or
314	if the user explicitly asks for the "USER" environment
315	variable to be exported.  In the server, if it receives
316	the "USER" environment variable, it won't print out the
317	banner message, so that only "Password:" will be printed.
318	This makes the symantics more like rlogin, and should be
319	more familiar to the user.  (People are not used to
320	getting a banner message, and then getting just a
321	"Password:" prompt.)
322
323	Re-vamp the code for starting up the child login
324	process.  The code was getting ugly, and it was
325	hard to tell what was really going on.  What we
326	do now is after the fork(), in the child:
327		1) make sure we have no controlling tty
328		2) open and initialize the tty
329		3) do a setsid()/setpgrp()
330		4) makes the tty our controlling tty.
331	On some systems, #2 makes the tty our controlling
332	tty, and #4 is a no-op.  The parent process does
333	a gets rid of any controlling tty after the child
334	is fork()ed.
335
336	Use the strdup() library routine in telnet, instead
337	of the local savestr() routine.  If you don't have
338	strdup(), you need to define NO_STRDUP.
339
340	Add support for ^T (SIGINFO/VSTATUS), found in the
341	4.3Reno distribution.  This maps to the AYT character.
342	You need a 4-line bugfix in the kernel to get this
343	to work properly:
344
345	> *** tty_pty.c.ORG	Tue Sep 11 09:41:53 1990
346	> --- tty_pty.c	Tue Sep 11 17:48:03 1990
347	> ***************
348	> *** 609,613 ****
349	> 			if ((tp->t_lflag&NOFLSH) == 0)
350	> 				ttyflush(tp, FREAD|FWRITE);
351	> ! 			pgsignal(tp->t_pgrp, *(unsigned int *)data);
352	> 			return(0);
353	> 		}
354	> --- 609,616 ----
355	> 			if ((tp->t_lflag&NOFLSH) == 0)
356	> 				ttyflush(tp, FREAD|FWRITE);
357	> ! 			pgsignal(tp->t_pgrp, *(unsigned int *)data, 1);
358	> ! 			if ((*(unsigned int *)data == SIGINFO) &&
359	> ! 			    ((tp->t_lflag&NOKERNINFO) == 0))
360	> ! 				ttyinfo(tp);
361	> 			return(0);
362	> 		}
363
364	The client is now smarter when setting the telnet escape
365	character; it only sets it to one of VEOL and VEOL2 if
366	one of them is undefined, and the other one is not already
367	defined to the telnet escape character.
368
369	Handle TERMIOS systems that have seperate input and output
370	line speed settings imbedded in the flags.
371
372	Many other minor bug fixes.
373
374June 20, 1990:
375	Re-organize makefiles and source tree.  The telnet/Source
376	directory is now gone, and all the source that was in
377	telnet/Source is now just in the telnet directory.
378
379	Seperate makefile for each system are now gone.  There
380	are two makefiles, Makefile and Makefile.generic.
381	The "Makefile" has the definitions for the various
382	system, and "Makefile.generic" does all the work.
383	There is a variable called "WHAT" that is used to
384	specify what to make.  For example, in the telnet
385	directory, you might say:
386		make 4.4bsd WHAT=clean
387	to clean out the directory.
388
389	Add support for the ENVIRON and XDISPLOC options.
390	In order for the server to work, login has to have
391	the "-p" option to preserve environment variables.
392
393	Add the SOFT_TAB and LIT_ECHO modes in the LINEMODE support.
394
395	Add the "-l user" option to command line and open command
396	(This is passed through the ENVIRON option).
397
398	Add the "-e" command line option, for setting the escape
399	character.
400
401	Add the "-D", diagnostic, option to the server.  This allows
402	the server to print out debug information, which is very
403	useful when trying to debug a telnet that doesn't have any
404	debugging ability.
405
406	Turn off the literal next character when not in LINEMODE.
407
408	Don't recognize ^Y locally, just pass it through.
409
410	Make minor modifications for Sun4.0 and Sun4.1
411
412	Add support for both FORW1 and FORW2 characters.  The
413	telnet escpape character is set to whichever of the
414	two is not being used.  If both are in use, the escape
415	character is not set, so when in linemode the user will
416	have to follow the escape character with a <CR> or <EOF)
417	to get it passed through.
418
419	Commands can now be put in single and double quotes, and
420	a backslash is now an escape character.  This is needed
421	for allowing arbitrary strings to be assigned to environment
422	variables.
423
424	Switch telnetd to use macros like telnet for keeping
425	track of the state of all the options.
426
427	Fix telnetd's processing of options so that we always do
428	the right processing of the LINEMODE option, regardless
429	of who initiates the request to turn it on.  Also, make
430	sure that if the other side went "WILL ECHO" in response
431	to our "DO ECHO", that we send a "DONT ECHO" to get the
432	option turned back off!
433
434	Fix the TERMIOS setting of the terminal speed to handle both
435	BSD's seperate fields, and the SYSV method of CBAUD bits.
436
437	Change how we deal with the other side refusing to enable
438	an option.  The sequence used to be: send DO option; receive
439	WONT option; send DONT option.  Now, the sequence is: send
440	DO option; receive WONT option.  Both should be valid
441	according to the spec, but there has been at least one
442	client implementation of telnet identified that can get
443	really confused by this.  (The exact sequence, from a trace
444	on the server side, is (numbers are number of responses that
445	we expect to get after that line...):
446
447		send WILL ECHO	1 (initial request)
448		send WONT ECHO	2 (server is changing state)
449		recv DO ECHO	1 (first reply, ok.  expect DONT ECHO next)
450		send WILL ECHO	2 (server changes state again)
451		recv DONT ECHO	1 (second reply, ok.  expect DO ECHO next)
452		recv DONT ECHO	0 (third reply, wrong answer. got DONT!!!)
453	***	send WONT ECHO	  (send WONT to acknowledge the DONT)
454		send WILL ECHO	1 (ask again to enable option)
455		recv DO ECHO	0
456
457		recv DONT ECHO	0
458		send WONT ECHO	1
459		recv DONT ECHO	0
460		recv DO ECHO	1
461		send WILL ECHO	0
462		(and the last 5 lines loop forever)
463
464	The line with the "***" is last of the WILL/DONT/WONT sequence.
465	The change to the server to not generate that makes this same
466	example become:
467
468		send will ECHO	1
469		send wont ECHO	2
470		recv do ECHO	1
471		send will ECHO	2
472		recv dont ECHO	1
473		recv dont ECHO	0
474		recv do ECHO	1
475		send will ECHO	0
476
477	There is other option negotiation going on, and not sending
478	the third part changes some of the timings, but this specific
479	example no longer gets stuck in a loop.  The "telnet.state"
480	file has been modified to reflect this change to the algorithm.
481
482	A bunch of miscellaneous bug fixes and changes to make
483	lint happier.
484
485	This version of telnet also has some KERBEROS stuff in
486	it. This has not been tested, it uses an un-authorized
487	telnet option number, and uses an out-of-date version
488	of the (still being defined) AUTHENTICATION option.
489	There is no support for this code, do not enable it.
490
491
492March 1, 1990:
493CHANGES/BUGFIXES SINCE LAST RELEASE:
494	Some support for IP TOS has been added.  Requires that the
495	kernel support the IP_TOS socket option (currently this
496	is only in UNICOS 6.0).
497
498	Both telnet and telnetd now use the cc_t typedef.  typedefs are
499	included for systems that don't have it (in termios.h).
500
501	SLC_SUSP was not supported properly before.  It is now.
502
503	IAC EOF was not translated  properly in telnetd for SYSV_TERMIO
504	when not in linemode.  It now saves a copy of the VEOF character,
505	so that when ICANON is turned off and we can't trust it anymore
506	(because it is now the VMIN character) we use the saved value.
507
508	There were two missing "break" commands in the linemode
509	processing code in telnetd.
510
511	Telnetd wasn't setting the kernel window size information
512	properly.  It was using the rows for both rows and columns...
513
514Questions/comments go to
515		David Borman
516		Cray Research, Inc.
517		655F Lone Oak Drive
518		Eagan, MN 55123
519		dab@cray.com.
520
521README:	You are reading it.
522
523Config.generic:
524	This file contains all the OS specific definitions.  It
525	has pre-definitions for many common system types, and is
526	in standard makefile fromat.  See the comments at the top
527	of the file for more information.
528
529Config.local:
530	This is not part of the distribution, but if this file exists,
531	it is used instead of "Config.generic".  This allows site
532	specific configuration without having to modify the distributed
533	"Config.generic" file.
534
535kern.diff:
536	This file contains the diffs for the changes needed for the
537	kernel to support LINEMODE is the server.  These changes are
538	for a 4.3BSD system.  You may need to make some changes for
539	your particular system.
540
541	There is a new bit in the terminal state word, TS_EXTPROC.
542	When this bit is set, several aspects of the terminal driver
543	are disabled.  Input line editing, character echo, and
544	mapping of signals are all disabled.  This allows the telnetd
545	to turn of these functions when in linemode, but still keep
546	track of what state the user wants the terminal to be in.
547
548	New ioctl()s:
549
550		TIOCEXT		Turn on/off the TS_EXTPROC bit
551		TIOCGSTATE	Get t_state of tty to look at TS_EXTPROC bit
552		TIOCSIG		Generate a signal to processes in the
553				current process group of the pty.
554
555	There is a new mode for packet driver, the TIOCPKT_IOCTL bit.
556	When packet mode is turned on in the pty, and the TS_EXTPROC
557	bit is set, then whenever the state of the pty is changed, the
558	next read on the master side of the pty will have the TIOCPKT_IOCTL
559	bit set, and the data will contain the following:
560		struct xx {
561			struct sgttyb a;
562			struct tchars b;
563			struct ltchars c;
564			int t_state;
565			int t_flags;
566		}
567	This allows the process on the server side of the pty to know
568	when the state of the terminal has changed, and what the new
569	state is.
570
571	However, if you define USE_TERMIO or SYSV_TERMIO, the code will
572	expect that the structure returned in the TIOCPKT_IOCTL is
573	the termio/termios structure.
574
575stty.diff:
576	This file contains the changes needed for the stty(1) program
577	to report on the current status of the TS_EXTPROC bit.  It also
578	allows the user to turn on/off the TS_EXTPROC bit.  This is useful
579	because it allows the user to say "stty -extproc", and the
580	LINEMODE option will be automatically disabled, and saying "stty
581	extproc" will re-enable the LINEMODE option.
582
583telnet.state:
584	Both the client and server have code in them to deal
585	with option negotiation loops.  The algorithm that is
586	used is described in this file.
587
588telnet:
589	This directory contains the client code.  No kernel changes are
590	needed to use this code.
591
592telnetd:
593	This directory contains the server code.  If LINEMODE or KLUDGELINEMODE
594	are defined, then the kernel modifications listed above are needed.
595
596libtelnet:
597	This directory contains code that is common to both the client
598	and the server.
599
600arpa:
601	This directory has a new <arpa/telnet.h>
602
603libtelnet/Makefile.4.4:
604telnet/Makefile.4.4:
605telnetd/Makefile.4.4:
606	These are the makefiles that can be used on a 4.3Reno
607	system when this software is installed in /usr/src/lib/libtelnet,
608	/usr/src/libexec/telnetd, and /usr/src/usr.bin/telnet.
609
610
611The following TELNET options are supported:
612
613	LINEMODE:
614		The LINEMODE option is supported as per RFC1116.  The
615		FORWARDMASK option is not currently supported.
616
617	BINARY: The client has the ability to turn on/off the BINARY
618		option in each direction.  Turning on BINARY from
619		server to client causes the LITOUT bit to get set in
620		the terminal driver on both ends,  turning on BINARY
621		from the client to the server causes the PASS8 bit
622		to get set in the terminal driver on both ends.
623
624	TERMINAL-TYPE:
625		This is supported as per RFC1091.  On the server side,
626		when a terminal type is received, termcap/terminfo
627		is consulted to determine if it is a known terminal
628		type.  It keeps requesting terminal types until it
629		gets one that it recongnizes, or hits the end of the
630		list.  The server side looks up the entry in the
631		termcap/terminfo data base, and generates a list of
632		names which it then passes one at a time to each
633		request for a terminal type, duplicating the last
634		entry in the list before cycling back to the beginning.
635
636	NAWS:	The Negotiate about Window Size, as per RFC 1073.
637
638	TERMINAL-SPEED:
639		Implemented as per RFC 1079
640
641	TOGGLE-FLOW-CONTROL:
642		Implemented as per RFC 1080
643
644	TIMING-MARK:
645		As per RFC 860
646
647	SGA:	As per RFC 858
648
649	ECHO:	As per RFC 857
650
651	LOGOUT: As per RFC 727
652
653	STATUS:
654		The server will send its current status upon
655		request.  It does not ask for the clients status.
656		The client will request the servers current status
657		from the "send getstatus" command.
658
659	ENVIRON:
660		This option is currently being defined by the IETF
661		Telnet Working Group, and an RFC has not yet been
662		issued, but should be in the near future...
663
664	X-DISPLAY-LOCATION:
665		This functionality can be done through the ENVIRON
666		option, it is added here for completeness.
667
668	AUTHENTICATION:
669		This option is currently being defined by the IETF
670		Telnet Working Group, and an RFC has not yet been
671		issued.  The basic framework is pretty much decided,
672		but the definitions for the specific authentication
673		schemes is still in a state of flux.
674
675	ENCRYPTION:
676		This option is currently being defined by the IETF
677		Telnet Working Group, and an RFC has not yet been
678		issued.  The draft RFC is still in a state of flux,
679		so this code may change in the future.
680