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