Update the FAQ to reflect 0.52 as being a current release rather
[sgt/putty] / doc / faq.but
1 \versionid $Id: faq.but,v 1.18 2002/01/14 12:16:58 simon Exp $
2
3 \A{faq} PuTTY FAQ
4
5 This FAQ is published on the PuTTY web site, and also provided as an
6 appendix in the manual.
7
8 \H{faq-support} Features supported in PuTTY
9
10 In general, if you want to know if PuTTY supports a particular
11 feature, you should look for it on the
12 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/}{PuTTY web site}.
13 In particular:
14
15 \b try the
16 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html}{changes
17 page}, and see if you can find the feature on there. If a feature is
18 listed there, it's been implemented. If it's listed as a change made
19 \e{since} the latest version, it should be available in the
20 development snapshots, in which case testing will be very welcome.
21
22 \b try the
23 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist.html}{Wishlist
24 page}, and see if you can find the feature there. If it's on there,
25 it probably \e{hasn't} been implemented.
26
27 \S{faq-ssh2}{Question} Does PuTTY support SSH v2?
28
29 Yes. SSH v2 support has been available in PuTTY since version 0.50.
30 However, currently the \e{default} SSH protocol is v1; to select SSH
31 v2 if your server supports both, go to the SSH panel and change the
32 \e{Preferred SSH protocol version} option.
33
34 Public key authentication (both RSA and DSA) in SSH v2 is new in
35 version 0.52.
36
37 \S{faq-ssh2-keyfmt}{Question} Does PuTTY support reading OpenSSH or
38 \cw{ssh.com} SSHv2 private key files?
39
40 Not at present. OpenSSH and \cw{ssh.com} have totally different
41 formats for private key files, and neither one is particularly
42 pleasant, so PuTTY has its own. We do plan to write a converter at
43 some stage.
44
45 \S{faq-ssh1}{Question} Does PuTTY support SSH v1?
46
47 Yes. SSH 1 support has always been available in PuTTY.
48
49 \S{faq-localecho}{Question} Does PuTTY support local echo?
50
51 Yes. Version 0.52 has proper support for local echo.
52
53 In version 0.51 and before, local echo could not be separated from
54 local line editing (where you type a line of text locally, and it is
55 not sent to the server until you press Return, so you have the
56 chance to edit it and correct mistakes \e{before} the server sees
57 it). New in version 0.52, local echo and local line editing are
58 separate options, and by default PuTTY will try to determine
59 automatically whether to enable them or not, based on which protocol
60 you have selected and also based on hints from the server. If you
61 have a problem with PuTTY's default choice, you can force each
62 option to be enabled or disabled as you choose. The controls are in
63 the Terminal panel, in the section marked \q{Line discipline
64 options}.
65
66 \S{faq-disksettings}{Question} Does PuTTY support storing its
67 settings in a disk file?
68
69 Not at present, although \k{config-file} in the documentation gives
70 a method of achieving the same effect.
71
72 \S{faq-fullscreen}{Question} Does PuTTY support full-screen mode,
73 like a DOS box?
74
75 Yes; this is a new feature in version 0.52.
76
77 \S{faq-password-remember}{Question} Does PuTTY have the ability to
78 remember my password so I don't have to type it every time?
79
80 No, it doesn't.
81
82 Remembering your password is a bad plan for obvious security
83 reasons: anyone who gains access to your machine while you're away
84 from your desk can find out the remembered password, and use it,
85 abuse it or change it.
86
87 In addition, it's not even \e{possible} for PuTTY to automatically
88 send your password in a Telnet session, because Telnet doesn't give
89 the client software any indication of which part of the login
90 process is the password prompt. PuTTY would have to guess, by
91 looking for words like \q{password} in the session data; and if your
92 login program is written in something other than English, this won't
93 work.
94
95 In SSH, remembering your password would be possible in theory, but
96 there doesn't seem to be much point since SSH supports public key
97 authentication, which is more flexible and more secure. See
98 \k{pubkey} in the documentation for a full discussion of public key
99 authentication.
100
101 \S{faq-hostkeys}{Question} Is there an option to turn off the
102 annoying host key prompts?
103
104 No, there isn't. And there won't be. Even if you write it yourself
105 and send us the patch, we won't accept it.
106
107 Those annoying host key prompts are the \e{whole point} of SSH.
108 Without them, all the cryptographic technology SSH uses to secure
109 your session is doing nothing more than making an attacker's job
110 slightly harder; instead of sitting between you and the server with
111 a packet sniffer, the attacker must actually subvert a router and
112 start modifying the packets going back and forth. But that's not all
113 that much harder than just sniffing; and without host key checking,
114 it will go completely undetected by client or server.
115
116 Host key checking is your guarantee that the encryption you put on
117 your data at the client end is the \e{same} encryption taken off the
118 data at the server end; it's your guarantee that it hasn't been
119 removed and replaced somewhere on the way. Host key checking makes
120 the attacker's job \e{astronomically} hard, compared to packet
121 sniffing, and even compared to subverting a router. Instead of
122 applying a little intelligence and keeping an eye on Bugtraq, the
123 attacker must now perform a brute-force attack against at least one
124 military-strength cipher. That insignificant host key prompt really
125 does make \e{that} much difference.
126
127 If you're having a specific problem with host key checking - perhaps
128 you want an automated batch job to make use of PSCP or Plink, and
129 the interactive host key prompt is hanging the batch process - then
130 the right way to fix it is to add the correct host key to the
131 Registry in advance. That way, you retain the \e{important} feature
132 of host key checking: the right key will be accepted and the wrong
133 ones will not. Adding an option to turn host key checking off
134 completely is the wrong solution and we will not do it.
135
136 \S{faq-server}{Question} Will you write an SSH server for the PuTTY
137 suite, to go with the client?
138
139 No. The only reason we might want to would be if we could easily
140 re-use existing code and significantly cut down the effort. We don't
141 believe this is the case; there just isn't enough common ground
142 between an SSH client and server to make it worthwhile.
143
144 If someone else wants to use bits of PuTTY in the process of writing
145 a Windows SSH server, they'd be perfectly welcome to of course, but
146 I really can't see it being a lot less effort for us to do that than
147 it would be for us to write a server from the ground up. We don't
148 have time, and we don't have motivation. The code is available if
149 anyone else wants to try it.
150
151 \H{faq-ports} Ports to other operating systems
152
153 The eventual goal is for PuTTY to be a multi-platform program, able
154 to run on at least Windows, MacOS and Unix. Whether this will
155 actually ever happen I have no idea, but it is the plan. A Mac port
156 has been started, but is only half-finished and currently not moving
157 very fast.
158
159 Porting will become easier once PuTTY has a generalised porting
160 layer, drawing a clear line between platform-dependent and
161 platform-independent code. The general intention is for this porting
162 layer to evolve naturally as part of the process of doing the first
163 port. One particularly nasty part of this will be separating the
164 many configuration options into platform-dependent and
165 platform-independent ones; for example, the options controlling when
166 the Windows System menu appears will be pretty much meaningless
167 under X11 or perhaps other windowing systems, whereas Telnet Passive
168 Mode is universal and shouldn't need to be specified once for each
169 platform.
170
171 \S{faq-wince}{Question} Will there be a port to Windows CE?
172
173 Probably not in the particularly near future. Despite sharing large
174 parts of the Windows API, in practice WinCE doesn't appear to be
175 significantly easier to port to than a totally different operating
176 system.
177
178 However, PuTTY on portable devices would clearly be a useful thing,
179 so in the long term I hope there will be a WinCE port.
180
181 \S{faq-win31}{Question} Is there a port to Windows 3.1?
182
183 PuTTY is a 32-bit application from the ground up, so it won't run on
184 Windows 3.1 as a native 16-bit program; and it would be \e{very}
185 hard to port it to do so, because of Windows 3.1's vile memory
186 allocation mechanisms.
187
188 However, it is possible in theory to compile the existing PuTTY
189 source in such a way that it will run under Win32s (an extension to
190 Windows 3.1 to let you run 32-bit programs). In order to do this
191 you'll need the right kind of C compiler - modern versions of Visual
192 C at least have stopped being backwards compatible to Win32s. Also,
193 the last time we tried this it didn't work very well.
194
195 If you're interested in running PuTTY under Windows 3.1, help and
196 testing in this area would be very welcome!
197
198 \S{faq-mac-port}{Question} Will there be a port to the Mac?
199
200 A Mac port was started once and is half-finished, but development
201 has been static for some time and the main PuTTY code has moved on,
202 so it's not clear how quickly development would resume even if
203 developer effort were available.
204
205 \S{faq-unix}{Question} Will there be a port to Unix?
206
207 I hope so, if only so that I can have an \cw{xterm}-like program
208 that supports exactly the same terminal emulation as PuTTY. If and
209 when we do do a Unix port, it will have a local-terminal back end so
210 it can be used like an \cw{xterm}, rather than only being usable as
211 a network utility.
212
213 \S{faq-epoc}{Question} Will there be a port to EPOC?
214
215 I hope so, but given that ports aren't really progressing very fast
216 even on systems the developers \e{do} already know how to program
217 for, it might be a long time before any of us get round to learning
218 a new system and doing the port for that.
219
220 \H{faq-embedding} Embedding PuTTY in other programs
221
222 \S{faq-dll}{Question} Is the SSH or Telnet code available as a DLL?
223
224 No, it isn't. It would take a reasonable amount of rewriting for
225 this to be possible, and since the PuTTY project itself doesn't
226 believe in DLLs (they make installation more error-prone) none of us
227 has taken the time to do it.
228
229 Most of the code cleanup work would be a good thing to happen in
230 general, so if anyone feels like helping, we wouldn't say no.
231
232 \S{faq-vb}{Question} Is the SSH or Telnet code available as a Visual
233 Basic component?
234
235 No, it isn't. None of the PuTTY team uses Visual Basic, and none of
236 us has any particular need to make SSH connections from a Visual
237 Basic application. In addition, all the preliminary work to turn it
238 into a DLL would be necessary first; and furthermore, we don't even
239 know how to write VB components.
240
241 If someone offers to do some of this work for us, we might consider
242 it, but unless that happens I can't see VB integration being
243 anywhere other than the very bottom of our priority list.
244
245 \S{faq-ipc}{Question} How can I use PuTTY to make an SSH connection
246 from within another program?
247
248 Probably your best bet is to use Plink, the command-line connection
249 tool. If you can start Plink as a second Windows process, and
250 arrange for your primary process to be able to send data to the
251 Plink process, and receive data from it, through pipes, then you
252 should be able to make SSH connections from your program.
253
254 This is what CVS for Windows does, for example.
255
256 \H{faq-details} Details of PuTTY's operation
257
258 \S{faq-term}{Question} What terminal type does PuTTY use?
259
260 For most purposes, PuTTY can be considered to be an \cw{xterm}
261 terminal.
262
263 PuTTY also supports some terminal control sequences not supported by
264 the real \cw{xterm}: notably the Linux console sequences that
265 reconfigure the colour palette, and the title bar control sequences
266 used by \cw{DECterm} (which are different from the \cw{xterm} ones;
267 PuTTY supports both).
268
269 By default, PuTTY announces its terminal type to the server as
270 \c{xterm}. If you have a problem with this, you can reconfigure it
271 to say something else; \c{vt220} might help if you have trouble.
272
273 \S{faq-settings}{Question} Where does PuTTY store its data?
274
275 PuTTY stores most of its data (saved sessions, SSH host keys) in the
276 Registry. The precise location is
277
278 \c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY
279
280 and within that area, saved sessions are stored under \c{Sessions}
281 while host keys are stored under \c{SshHostKeys}.
282
283 PuTTY also requires a random number seed file, to improve the
284 unpredictability of randomly chosen data needed as part of the SSH
285 cryptography. This is stored by default in your Windows home
286 directory (\c{%HOMEDRIVE%\\%HOMEPATH%}), or in the actual Windows
287 directory (such as \c{C:\\WINDOWS}) if the home directory doesn't
288 exist, for example if you're using Win95. If you want to change the
289 location of the random number seed file, you can put your chosen
290 pathname in the Registry, at
291
292 \c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\RandSeedFile
293
294 \H{faq-howto} HOWTO questions
295
296 \S{faq-startmax}{Question} How can I make PuTTY start up maximised?
297
298 Create a Windows shortcut to start PuTTY from, and set it as \q{Run
299 Maximized}.
300
301 \S{faq-startsess}{Question} How can I create a Windows shortcut to
302 start a particular saved session directly?
303
304 To run a PuTTY session saved under the name \q{\cw{mysession}},
305 create a Windows shortcut that invokes PuTTY with a command line
306 like
307
308 \c \path\name\to\putty.exe @mysession
309
310 \S{faq-startssh}{Question} How can I start an SSH session straight
311 from the command line?
312
313 Use the command line \c{putty -ssh host.name}. Alternatively, create
314 a saved session that specifies the SSH protocol, and start the saved
315 session as shown in \k{faq-startsess}.
316
317 \S{faq-cutpaste}{Question} How do I copy and paste between PuTTY and
318 other Windows applications?
319
320 Copy and paste works similarly to the X Window System. You use the
321 left mouse button to select text in the PuTTY window. The act of
322 selection \e{automatically} copies the text to the clipboard: there
323 is no need to press Ctrl-Ins or Ctrl-C or anything else. In fact,
324 pressing Ctrl-C will send a Ctrl-C character to the other end of
325 your connection (just like it does the rest of the time), which may
326 have unpleasant effects. The \e{only} thing you need to do, to copy
327 text to the clipboard, is to select it.
328
329 To paste the clipboard contents into a PuTTY window, by default you
330 click the right mouse button. If you have a three-button mouse and
331 are used to X applications, you can configure pasting to be done by
332 the middle button instead, but this is not the default because most
333 Windows users don't have a middle button at all.
334
335 You can also paste by pressing Shift-Ins.
336
337 \S{faq-tunnels}{Question} How do I use X forwarding and port
338 forwarding? I can't find the Tunnels panel.
339
340 This is a new feature in version 0.52. You should upgrade.
341
342 \S{faq-options}{Question} How do I use all PuTTY's features (public
343 keys, port forwarding, SSH v2, etc.) in PSCP, PSFTP and Plink?
344
345 The command-line tools are currently rather short of command line
346 options to enable this sort of thing. However, you can use most of
347 PuTTY's features if you create a PuTTY saved session, and then use
348 the name of the saved session on the command line in place of a
349 hostname. This works for PSCP, PSFTP and Plink (but don't expect
350 port forwarding in the file transfer applications!).
351
352 \S{faq-pscp}{Question} How do I use PSCP.EXE? When I double-click it
353 gives me a command prompt window which then closes instantly.
354
355 PSCP is a command-line application, not a GUI application. If you
356 run it without arguments, it will simply print a help message and
357 terminate.
358
359 To use PSCP properly, run it from a Command Prompt window. See
360 \k{pscp} in the documentation for more details.
361
362 \S{faq-pscp-spaces}{Question} How do I use PSCP to copy a file whose
363 name has spaces in?
364
365 If PSCP is using the traditional SCP protocol, this is confusing. If
366 you're specifying a file at the local end, you just use one set of
367 quotes as you would normally do:
368
369 \c pscp "local filename with spaces" user@host:
370 \c pscp user@host:myfile "local filename with spaces"
371
372 But if the filename you're specifying is on the \e{remote} side, you
373 have to use backslashes and two sets of quotes:
374
375 \c pscp user@host:"\"remote filename with spaces\"" local_filename
376 \c pscp local_filename user@host:"\"remote filename with spaces\""
377
378 Worse still, in a remote-to-local copy you have to specify the local
379 file name explicitly, otherwise PSCP will complain that they don't
380 match (unless you specified the \c{-unsafe} option). The following
381 command will give an error message:
382
383 \c c:\>pscp user@host:"\"oo er\"" .
384 \c warning: remote host tried to write to a file called 'oo er'
385 \c when we requested a file called '"oo er"'.
386
387 Instead, you need to specify the local file name in full:
388
389 \c c:\>pscp user@host:"\"oo er\"" "oo er"
390
391 If PSCP is using the newer SFTP protocol, none of this is a problem,
392 and all filenames with spaces in are specified using a single pair
393 of quotes in the obvious way:
394
395 \c pscp "local file" user@host:
396 \c pscp user@host:"remote file" .
397
398 \H{faq-trouble} Troubleshooting
399
400 \S{faq-incorrect-mac}{Question} Why do I see \q{Incorrect MAC
401 received on packet}?
402
403 This is due to a bug in old SSH 2 servers distributed by
404 \cw{ssh.com}. Version 2.3.0 and below of their SSH 2 server
405 constructs Message Authentication Codes in the wrong way, and
406 expects the client to construct them in the same wrong way. PuTTY
407 constructs the MACs correctly by default, and hence these old
408 servers will fail to work with it.
409
410 If you are using PuTTY version 0.52 or better, this should work
411 automatically: PuTTY should detect the buggy servers from their
412 version number announcement, and automatically start to construct
413 its MACs in the same incorrect manner as they do, so it will be able
414 to work with them.
415
416 If you are using PuTTY version 0.51 or below, you can enable the
417 workaround by going to the SSH panel and ticking the box labelled
418 \q{Imitate SSH 2 MAC bug}. It's possible that you might have to do
419 this with 0.52 as well, if a buggy server exists that PuTTY doesn't
420 know about.
421
422 In this context MAC stands for Message Authentication Code. It's a
423 cryptographic term, and it has nothing at all to do with Ethernet
424 MAC (Media Access Control) addresses.
425
426 \S{faq-colours}{Question} I clicked on a colour in the Colours
427 panel, and the colour didn't change in my terminal.
428
429 That isn't how you're supposed to use the Colours panel.
430
431 During the course of a session, PuTTY potentially uses \e{all} the
432 colours listed in the Colours panel. It's not a question of using
433 only one of them and you choosing which one; PuTTY will use them
434 \e{all}. The purpose of the Colours panel is to let you adjust the
435 appearance of all the colours. So to change the colour of the
436 cursor, for example, you would select \q{Cursor Colour}, press the
437 \q{Modify} button, and select a new colour from the dialog box that
438 appeared. Similarly, if you want your session to appear in green,
439 you should select \q{Default Foreground} and press \q{Modify}.
440 Clicking on \q{ANSI Green} won't turn your session green; it will
441 only allow you to adjust the \e{shade} of green used when PuTTY is
442 instructed by the server to display green text.
443
444 \S{faq-winsock2}{Question} Plink on Windows 95 says it can't find
445 \cw{WS2_32.DLL}.
446
447 Plink requires the extended Windows network library, WinSock version
448 2. This is installed as standard on Windows 98 and above, and on
449 Windows NT, and even on later versions of Windows 95; but early
450 Win95 installations don't have it.
451
452 In order to use Plink on these systems, you will need to download
453 the
454 \W{http://www.microsoft.com/windows95/downloads/contents/wuadmintools/s_wunetworkingtools/w95sockets2/}{WinSock 2 upgrade}:
455
456 \c http://www.microsoft.com/windows95/downloads/contents/wuadmintools/
457 \c s_wunetworkingtools/w95sockets2/
458
459 \S{faq-rekey}{Question} My PuTTY sessions close after an hour and
460 tell me \q{Server failed host key check}.
461
462 This is a bug in all versions of PuTTY up to and including 0.51. SSH
463 v2 servers from \cw{ssh.com} will require the key exchange to be
464 repeated one hour after the start of the connection, and PuTTY will
465 get this wrong.
466
467 Upgrade to version 0.52 and the problem should go away.
468
469 \S{faq-outofmem}{Question} After trying to establish an SSH 2
470 connection, PuTTY says \q{Out of memory} and dies.
471
472 If this happens just while the connection is starting up, this often
473 indicates that for some reason the client and server have failed to
474 establish a session encryption key. Somehow, they have performed
475 calculations that should have given each of them the same key, but
476 have ended up with different keys; so data encrypted by one and
477 decrypted by the other looks like random garbage.
478
479 This causes an \q{out of memory} error because the first encrypted
480 data PuTTY expects to see is the length of an SSH message. Normally
481 this will be something well under 100 bytes. If the decryption has
482 failed, PuTTY will see a completely random length in the region of
483 two \e{gigabytes}, and will try to allocate enough memory to store
484 this non-existent message. This will immediately lead to it thinking
485 it doesn't have enough memory, and panicking.
486
487 If this happens to you, it is quite likely to still be a PuTTY bug
488 and you should report it (although it might be a bug in your SSH
489 server instead); but it doesn't necessarily mean you've actually run
490 out of memory.
491
492 \S{faq-bce}{Question} When I run full-colour applications, I see
493 areas of black space where colour ought to be.
494
495 You almost certainly need to enable the \q{Use background colour to
496 erase screen} setting in the Terminal panel. Note that if you do
497 this in mid-session, it won't take effect until you reset the
498 terminal (see \k{faq-resetterm}).
499
500 \S{faq-resetterm}{Question} When I change some terminal settings,
501 nothing happens.
502
503 Some of the terminal options (notably Auto Wrap and
504 background-colour screen erase) actually represent the \e{default}
505 setting, rather than the currently active setting. The server can
506 send sequences that modify these options in mid-session, but when
507 the terminal is reset (by server action, or by you choosing \q{Reset
508 Terminal} from the System menu) the defaults are restored.
509
510 If you want to change one of these options in the middle of a
511 session, you will find that the change does not immediately take
512 effect. It will only take effect once you reset the terminal.
513
514 \S{faq-altgr}{Question} I can't type characters that require the
515 AltGr key.
516
517 In PuTTY version 0.51, the AltGr key was broken. Upgrade to version
518 0.52.
519
520 \S{faq-idleout}{Question} My PuTTY sessions unexpectedly close after
521 they are idle for a while.
522
523 Some types of firewall, and almost any router doing Network Address
524 Translation (NAT, also known as IP masquerading), will forget about
525 a connection through them if the connection does nothing for too
526 long. This will cause the connection to be rudely cut off when
527 contact is resumed.
528
529 You can try to combat this by telling PuTTY to send \e{keepalives}:
530 packets of data which have no effect on the actual session, but
531 which reassure the router or firewall that the network connection is
532 still active and worth remembering about.
533
534 Keepalives don't solve everything, unfortunately; although they
535 cause greater robustness against this sort of router, they can also
536 cause a \e{loss} of robustness against network dropouts. See
537 \k{config-keepalive} in the documentation for more discussion of
538 this.
539
540 \S{faq-timeout}{Question} PuTTY's network connections time out too
541 quickly when network connectivity is temporarily lost.
542
543 This is a Windows problem, not a PuTTY problem. The timeout value
544 can't be set on per application or per session basis. To increase
545 the TCP timeout globally, you need to tinker with the Registry.
546
547 On Windows 95, 98 or ME, the registry key you need to change is
548
549 \c HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\
550 \c MSTCP\MaxDataRetries
551
552 (it must be of type DWORD in Win95, or String in Win98/ME).
553
554 On Windows NT or 2000, the registry key is
555
556 \c HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\
557 \c Parameters\TcpMaxDataRetransmissions
558
559 and it must be of type DWORD.
560
561 Set the key's value to something like 10. This will cause Windows to
562 try harder to keep connections alive instead of abandoning them.
563
564 \S{faq-puttyputty}{Question} When I \cw{cat} a binary file, I get
565 `PuTTYPuTTYPuTTY' on my command line.
566
567 Don't do that, then.
568
569 This is designed behaviour; when PuTTY receives the character
570 Control-E from the remote server, it interprets it as a request to
571 identify itself, and so it sends back the string \q{\cw{PuTTY}} as
572 if that string had been entered at the keyboard. Control-E should
573 only be sent by programs that are prepared to deal with the
574 response. Writing a binary file to your terminal is likely to output
575 many Control-E characters, and cause this behaviour. Don't do it.
576 It's a bad plan.
577
578 To mitigate the effects, you could configure the answerback string
579 to be empty (see \k{config-answerback}); but writing binary files to
580 your terminal is likely to cause various other unpleasant behaviour,
581 so this is only a small remedy.
582
583 \S{faq-wintitle}{Question} When I \cw{cat} a binary file, my window
584 title changes to a nonsense string.
585
586 Don't do that, then.
587
588 It is designed behaviour that PuTTY should have the ability to
589 adjust the window title on instructions from the server. Normally
590 the control sequence that does this should only be sent
591 deliberately, by programs that know what they are doing and intend
592 to put meaningful text in the window title. Writing a binary file to
593 your terminal runs the risk of sending the same control sequence by
594 accident, and cause unexpected changes in the window title. Don't do
595 it.
596
597 \S{faq-password-fails}{Question} My keyboard stops working once
598 PuTTY displays the password prompt.
599
600 No, it doesn't. PuTTY just doesn't display the password you type, so
601 that someone looking at your screen can't see what it is.
602
603 Unlike the Windows login prompts, PuTTY doesn't display the password
604 as a row of asterisks either. This is so that someone looking at
605 your screen can't even tell how \e{long} your password is, which
606 might be valuable information.
607
608 \S{faq-keyboard}{Question} One or more function keys don't do what I
609 expected in a server-side application.
610
611 If you've already tried all the relevant options in the PuTTY
612 Keyboard panel, you may need to mail the PuTTY maintainers and ask.
613
614 It is \e{not} usually helpful just to tell us which application,
615 which server operating system, and which key isn't working; in order
616 to replicate the problem we would need to have a copy of every
617 operating system, and every application, that anyone has ever
618 complained about.
619
620 PuTTY responds to function key presses by sending a sequence of
621 control characters to the server. If a function key isn't doing what
622 you expect, it's likely that the character sequence your application
623 is expecting to receive is not the same as the one PuTTY is sending.
624 Therefore what we really need to know is \e{what} sequence the
625 application is expecting.
626
627 The simplest way to investigate this is to find some other terminal
628 environment, in which that function key \e{does} work; and then
629 investigate what sequence the function key is sending in that
630 situation. One reasonably easy way to do this on a Unix system is to
631 type the command \c{cat}, and then press the function key. This is
632 likely to produce output of the form \c{^[[11~}. You can also do
633 this in PuTTY, to find out what sequence the function key is
634 producing in that. Then you can mail the PuTTY maintainers and tell
635 us \q{I wanted the F1 key to send \c{^[[11~}, but instead it's
636 sending \c{^[OP}, can this be done?}, or something similar.
637
638 You should still read the
639 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/feedback.html}{Feedback
640 page} on the PuTTY website (also provided as \k{feedback} in the
641 manual), and follow the guidelines contained in that.
642
643 \H{faq-secure} Security questions
644
645 \S{faq-publicpc}{Question} Is it safe for me to download PuTTY and
646 use it on a public PC?
647
648 It depends on whether you trust that PC. If you don't trust the
649 public PC, don't use PuTTY on it, and don't use any other software
650 you plan to type passwords into either. It might be watching your
651 keystrokes, or it might tamper with the PuTTY binary you download.
652 There is \e{no} program safe enough that you can run it on an
653 actively malicious PC and get away with typing passwords into it.
654
655 If you do trust the PC, then it's probably OK to use PuTTY on it
656 (but if you don't trust the network, then the PuTTY download might
657 be tampered with, so it would be better to carry PuTTY with you on a
658 floppy).
659
660 \S{faq-cleanup}{Question} What does PuTTY leave on a system? How can
661 I clean up after it?
662
663 PuTTY will leave some Registry entries, and a random seed file, on
664 the PC (see \k{faq-settings}). If you are using PuTTY on a public
665 PC, or somebody else's PC, you might want to clean these up when you
666 leave. You can do that automatically, by running the command
667 \c{putty -cleanup}.
668
669 \S{faq-dsa}{Question} How come PuTTY now supports DSA, when the
670 website used to say how insecure it was?
671
672 DSA has a major weakness \e{if badly implemented}: it relies on a
673 random number generator to far too great an extent. If the random
674 number generator produces a number an attacker can predict, the DSA
675 private key is exposed - meaning that the attacker can log in as you
676 on all systems that accept that key.
677
678 The PuTTY policy changed because the developers were informed of
679 ways to implement DSA which do not suffer nearly as badly from this
680 weakness, and indeed which don't need to rely on random numbers at
681 all. For this reason we now believe PuTTY's DSA implementation is
682 probably OK. However, if you have the choice, we still recommend you
683 use RSA instead.
684
685 \H{faq-admin} Administrative questions
686
687 \S{faq-domain}{Question} Would you like me to register you a nicer
688 domain name?
689
690 No, thank you. Even if you can find one (most of them seem to have
691 been registered already, by people who didn't ask whether we
692 actually wanted it before they applied), we're happy with the PuTTY
693 web site being exactly where it is. It's not hard to find (just type
694 \q{putty} into \W{http://www.google.com/}{google.com} and we're the
695 first link returned), and we don't believe the administrative hassle
696 of moving the site would be worth the benefit.
697
698 In addition, if we \e{did} want a custom domain name, we would want
699 to run it ourselves, so we knew for certain that it would continue
700 to point where we wanted it, and wouldn't suddenly change or do
701 strange things. Having it registered for us by a third party who we
702 don't even know is not the best way to achieve this.
703
704 \S{faq-webhosting}{Question} Would you like free web hosting for the
705 PuTTY web site?
706
707 We already have some, thanks.
708
709 \S{faq-sourceforge}{Question} Why don't you move PuTTY to
710 SourceForge?
711
712 Partly, because we don't want to move the web site location (see
713 \k{faq-domain}).
714
715 Also, security reasons. PuTTY is a security product, and as such it
716 is particularly important to guard the code and the web site against
717 unauthorised modifications which might introduce subtle security
718 flaws. Therefore, we prefer that the CVS repository, web site and
719 FTP site remain where they are, under the direct control of system
720 administrators we know and trust personally, rather than being run
721 by a large organisation full of people we've never met and which is
722 known to have had breakins in the past.
723
724 No offence to SourceForge; I think they do a wonderful job. But
725 they're not ideal for everyone, and in particular they're not ideal
726 for us.
727
728 \S{faq-mailinglist1}{Question} Why can't I subscribe to the
729 putty-bugs mailing list?
730
731 Because you're not a member of the PuTTY core development team. The
732 putty-bugs mailing list is not a general newsgroup-like discussion
733 forum; it's a contact address for the core developers, and an
734 \e{internal} mailing list for us to discuss things among ourselves.
735 If we opened it up for everybody to subscribe to, it would turn into
736 something more like a newsgroup and we would be completely
737 overwhelmed by the volume of traffic. It's hard enough to keep up
738 with the list as it is.
739
740 \S{faq-mailinglist2}{Question} If putty-bugs isn't a
741 general-subscription mailing list, what is?
742
743 There isn't one, that we know of.
744
745 If someone else wants to set up a mailing list for PuTTY users to
746 help each other with common problems, that would be fine with us;
747 but the PuTTY team would almost certainly not have the time to read
748 it, so any questions the list couldn't answer would have to be
749 forwarded on to us by the questioner. In any case, it's probably
750 better to use the established newsgroup \cw{comp.security.ssh} for
751 this purpose.
752
753 \S{faq-donations}{Question} How can I donate to PuTTY development?
754
755 Please, \e{please} don't feel you have to. PuTTY is completely free
756 software, and not shareware. We think it's very important that
757 \e{everybody} who wants to use PuTTY should be able to, whether they
758 have any money or not; so the last thing we would want is for a
759 PuTTY user to feel guilty because they haven't paid us any money. If
760 you want to keep your money, please do keep it. We wouldn't dream of
761 asking for any.
762
763 Having said all that, if you still really \e{want} to give us money,
764 we won't argue :-) The easiest way for us to accept donations is if
765 you go to \W{http://www.e-gold.com}\cw{www.e-gold.com}, and deposit
766 your donation in account number 174769. Then send us e-mail to let
767 us know you've done so (otherwise we might not notice for months!).
768
769 Small donations (tens of dollars or tens of euros) will probably be
770 spent on beer or curry, which helps motivate our volunteer team to
771 continue doing this for the world. Larger donations will be spent on
772 something that actually helps development, if we can find anything
773 (perhaps new hardware, or a copy of Windows 2000), but if we can't
774 find anything then we'll just distribute the money among the
775 developers. If you want to be sure your donation is going towards
776 something worthwhile, ask us first. If you don't like these terms,
777 feel perfectly free not to donate. We don't mind.
778
779 \S{faq-sillyputty}{Question} Where can I buy silly putty?
780
781 You're looking at the wrong web site; the only PuTTY we know about
782 here is the name of a computer program.
783
784 If you want the kind of putty you can buy as an executive toy, the
785 PuTTY team can personally recommend Thinking Putty, which you can
786 buy from Crazy Aaron's Putty World, at
787 \W{http://www.puttyworld.com}\cw{www.puttyworld.com}.
788
789 \S{faq-pronounce}{Question} How do I pronounce PuTTY?
790
791 Exactly like the normal word \q{putty}. Just like the stuff you put
792 on window frames. (One of the reasons it's called PuTTY is because
793 it makes Windows usable. :-)