Add the missing psftp-pubkey section, shamelessly cribbed from the
[u/mdw/putty] / doc / faq.but
CommitLineData
a1d2976b 1\versionid $Id: faq.but,v 1.13 2001/12/04 19:12:04 simon Exp $
8f1529bc 2
ee46ef84 3\A{faq} PuTTY FAQ
4
5This FAQ is published on the PuTTY web site, and also provided as an
6appendix in the manual.
7
8\H{faq-support} Features supported in PuTTY
9
10In general, if you want to know if PuTTY supports a particular
11feature, you should look for it on the
12\W{http://www.chiark.greenend.org.uk/~sgtatham/putty/}{PuTTY web site}.
13In particular:
14
15\b try the
16\W{http://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html}{changes
17page}, and see if you can find the feature on there. If a feature is
18listed 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
20development 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
24page}, and see if you can find the feature there. If it's on there,
25it probably \e{hasn't} been implemented.
26
a1d2976b 27\S{faq-ssh2}{Question} Does PuTTY support SSH v2?
ee46ef84 28
29Yes. SSH v2 support has been available in PuTTY since version 0.50.
30However, currently the \e{default} SSH protocol is v1; to select SSH
31v2 if your server supports both, go to the SSH panel and change the
32\e{Preferred SSH protocol version} option.
33
34Public key authentication (both RSA and DSA) in SSH v2 has been
35added since version 0.51.
36
a1d2976b 37\S{faq-ssh2-keyfmt}{Question} Does PuTTY support reading OpenSSH or
ee46ef84 38\cw{ssh.com} SSHv2 private key files?
39
40Not at present. OpenSSH and \cw{ssh.com} have totally different
41formats for private key files, and neither one is particularly
42pleasant, so PuTTY has its own. We do plan to write a converter at
43some stage.
44
a1d2976b 45\S{faq-ssh1}{Question} Does PuTTY support SSH v1?
ee46ef84 46
47Yes. SSH 1 support has always been available in PuTTY.
48
a1d2976b 49\S{faq-localecho}{Question} Does PuTTY support local echo?
ee46ef84 50
51Yes.
52
53In version 0.51 and before, local echo cannot be separated from
54local line editing (where you type a line of text locally, and it is
55not sent to the server until you press Return, so you have the
56chance to edit it and correct mistakes \e{before} the server sees
57it). The two features can be enabled and disabled from the Terminal
58panel, using the checkbox marked \q{Use local terminal line
59discipline}. Note that due to a bug in those versions of PuTTY,
60changing this feature in mid-session will have no effect; you have
61to enable it \e{before} you open the connection.
62
63In later versions, local echo and local line editing are separate
64options, and by default PuTTY will try to determine automatically
65whether to enable them or not, based on which protocol you have
66selected and also based on hints from the server. If you have a
67problem with PuTTY's default choice, you can force each option to be
68enabled or disabled as you choose. The controls are in the Terminal
69panel, in the section marked \q{Line discipline options}.
70
a1d2976b 71\S{faq-disksettings}{Question} Does PuTTY support storing its
70706890 72settings in a disk file?
ee46ef84 73
74Not at present, although \k{config-file} in the documentation gives
75a method of achieving the same effect.
76
a1d2976b 77\S{faq-fullscreen}{Question} Does PuTTY support full-screen mode,
70706890 78like a DOS box?
ee46ef84 79
80Not in the 0.51 release, but it has been added since then.
81
a1d2976b 82\S{faq-password}{Question} Does PuTTY have the ability to remember
70706890 83my password so I don't have to type it every time?
ee46ef84 84
85No, it doesn't.
86
87Remembering your password is a bad plan for obvious security
88reasons: anyone who gains access to your machine while you're away
89from your desk can find out the remembered password, and use it,
90abuse it or change it.
91
92In addition, it's not even \e{possible} for PuTTY to automatically
93send your password in a Telnet session, because Telnet doesn't give
94the client software any indication of which part of the login
95process is the password prompt. PuTTY would have to guess, by
96looking for words like \q{password} in the session data; and if your
97login program is written in something other than English, this won't
98work.
99
100In SSH, remembering your password would be possible in theory, but
101there doesn't seem to be much point since SSH supports public key
102authentication, which is more flexible and more secure. See
103\k{pubkey} in the documentation for a full discussion of public key
104authentication.
105
a1d2976b 106\S{faq-hostkeys}{Question} Is there an option to turn off the
70706890 107annoying host key prompts?
cad566a9 108
109No, there isn't. And there won't be. Even if you write it yourself
110and send us the patch, we won't accept it.
111
112Those annoying host key prompts are the \e{whole point} of SSH.
113Without them, all the cryptographic technology SSH uses to secure
114your session is doing nothing more than making an attacker's job
115slightly harder; instead of sitting between you and the server with
116a packet sniffer, the attacker must actually subvert a router and
117start modifying the packets going back and forth. But that's not all
118that much harder than just sniffing; and without host key checking,
119it will go completely undetected by client or server.
120
121Host key checking is your guarantee that the encryption you put on
122your data at the client end is the \e{same} encryption taken off the
123data at the server end; it's your guarantee that it hasn't been
124removed and replaced somewhere on the way. Host key checking makes
125the attacker's job \e{astronomically} hard, compared to packet
126sniffing, and even compared to subverting a router. Instead of
127applying a little intelligence and keeping an eye on Bugtraq, the
128attacker must now perform a brute-force attack against at least one
129military-strength cipher. That insignificant host key prompt really
130does make \e{that} much difference.
131
132If you're having a specific problem with host key checking - perhaps
133you want an automated batch job to make use of PSCP or Plink, and
134the interactive host key prompt is hanging the batch process - then
135the right way to fix it is to add the correct host key to the
136Registry in advance. That way, you retain the \e{important} feature
137of host key checking: the right key will be accepted and the wrong
138ones will not. Adding an option to turn host key checking off
139completely is the wrong solution and we will not do it.
140
a1d2976b 141\S{faq-server}{Question} Will you write an SSH server for the PuTTY
70706890 142suite, to go with the client?
ae915483 143
144No. The only reason we might want to would be if we could easily
145re-use existing code and significantly cut down the effort. We don't
146believe this is the case; there just isn't enough common ground
147between an SSH client and server to make it worthwhile.
148
149If someone else wants to use bits of PuTTY in the process of writing
150a Windows SSH server, they'd be perfectly welcome to of course, but
151I really can't see it being a lot less effort for us to do that than
152it would be for us to write a server from the ground up. We don't
153have time, and we don't have motivation. The code is available if
154anyone else wants to try it.
155
ee46ef84 156\H{faq-ports} Ports to other operating systems
157
158The eventual goal is for PuTTY to be a multi-platform program, able
159to run on at least Windows, MacOS and Unix. Whether this will
160actually ever happen I have no idea, but it is the plan. A Mac port
161has been started, but is only half-finished and currently not moving
162very fast.
163
164Porting will become easier once PuTTY has a generalised porting
165layer, drawing a clear line between platform-dependent and
166platform-independent code. The general intention is for this porting
167layer to evolve naturally as part of the process of doing the first
168port. One particularly nasty part of this will be separating the
169many configuration options into platform-dependent and
170platform-independent ones; for example, the options controlling when
171the Windows System menu appears will be pretty much meaningless
172under X11 or perhaps other windowing systems, whereas Telnet Passive
173Mode is universal and shouldn't need to be specified once for each
174platform.
175
a1d2976b 176\S{faq-wince}{Question} Will there be a port to Windows CE?
ee46ef84 177
178Probably not in the particularly near future. Despite sharing large
179parts of the Windows API, in practice WinCE doesn't appear to be
180significantly easier to port to than a totally different operating
181system.
182
183However, PuTTY on portable devices would clearly be a useful thing,
184so in the long term I hope there will be a WinCE port.
185
a1d2976b 186\S{faq-mac}{Question} Will there be a port to the Mac?
ee46ef84 187
188A Mac port was started once and is half-finished, but development
189has been static for some time and the main PuTTY code has moved on,
190so it's not clear how quickly development would resume even if
191developer effort were available.
192
a1d2976b 193\S{faq-unix}{Question} Will there be a port to Unix?
ee46ef84 194
195I hope so, if only so that I can have an \cw{xterm}-like program
196that supports exactly the same terminal emulation as PuTTY. If and
197when we do do a Unix port, it will have a local-terminal back end so
198it can be used like an \cw{xterm}, rather than only being usable as
199a network utility.
200
a1d2976b 201\S{faq-epoc}{Question} Will there be a port to EPOC?
ee46ef84 202
203I hope so, but given that ports aren't really progressing very fast
204even on systems the developers \e{do} already know how to program
205for, it might be a long time before any of us get round to learning
206a new system and doing the port for that.
207
208\H{faq-embedding} Embedding PuTTY in other programs
209
a1d2976b 210\S{faq-dll}{Question} Is the SSH or Telnet code available as a DLL?
ee46ef84 211
212No, it isn't. It would take a reasonable amount of rewriting for
213this to be possible, and since the PuTTY project itself doesn't
214believe in DLLs (they make installation more error-prone) none of us
215has taken the time to do it.
216
217Most of the code cleanup work would be a good thing to happen in
218general, so if anyone feels like helping, we wouldn't say no.
219
a1d2976b 220\S{faq-vb}{Question} Is the SSH or Telnet code available as a Visual
70706890 221Basic component?
ee46ef84 222
223No, it isn't. None of the PuTTY team uses Visual Basic, and none of
224us has any particular need to make SSH connections from a Visual
225Basic application. In addition, all the preliminary work to turn it
226into a DLL would be necessary first; and furthermore, we don't even
227know how to write VB components.
228
229If someone offers to do some of this work for us, we might consider
230it, but unless that happens I can't see VB integration being
231anywhere other than the very bottom of our priority list.
232
a1d2976b 233\S{faq-ipc}{Question} How can I use PuTTY to make an SSH connection
70706890 234from within another program?
ee46ef84 235
236Probably your best bet is to use Plink, the command-line connection
237tool. If you can start Plink as a second Windows process, and
238arrange for your primary process to be able to send data to the
239Plink process, and receive data from it, through pipes, then you
240should be able to make SSH connections from your program.
241
242This is what CVS for Windows does, for example.
243
244\H{faq-details} Details of PuTTY's operation
245
a1d2976b 246\S{faq-term}{Question} What terminal type does PuTTY use?
ee46ef84 247
248For most purposes, PuTTY can be considered to be an \cw{xterm}
249terminal, although full support for some of \cw{xterm}'s features,
250such as passing mouse actions to the server-side program, is not
251present in the 0.51 release (but has been added since).
252
253PuTTY also supports some terminal control sequences not supported by
254the real \cw{xterm}: notably the Linux console sequences that
255reconfigure the colour palette, and the title bar control sequences
256used by \cw{DECterm} (which are different from the \cw{xterm} ones;
257PuTTY supports both).
258
259By default, PuTTY announces its terminal type to the server as
260\c{xterm}. If you have a problem with this, you can reconfigure it
261to say something else; \c{vt220} might help if you have trouble.
262
a1d2976b 263\S{faq-settings}{Question} Where does PuTTY store its data?
ee46ef84 264
265PuTTY stores most of its data (saved sessions, SSH host keys) in the
266Registry. The precise location is
267
268\c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY
269
270and within that area, saved sessions are stored under \c{Sessions}
271while host keys are stored under \c{SshHostKeys}.
272
273PuTTY also requires a random number seed file, to improve the
274unpredictability of randomly chosen data needed as part of the SSH
275cryptography. This is stored by default in your Windows home
276directory (\c{%HOMEDRIVE%\\%HOMEPATH%}), or in the actual Windows
277directory (such as \c{C:\\WINDOWS}) if the home directory doesn't
278exist, for example if you're using Win95. If you want to change the
279location of the random number seed file, you can put your chosen
280pathname in the Registry, at
281
282\c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\RandSeedFile
283
284\H{faq-howto} HOWTO questions
285
a1d2976b 286\S{faq-startmax}{Question} How can I make PuTTY start up maximised?
ee46ef84 287
288Create a Windows shortcut to start PuTTY from, and set it as \q{Run
289Maximized}.
290
a1d2976b 291\S{faq-startsess}{Question} How can I create a Windows shortcut to
70706890 292start a particular saved session directly?
ee46ef84 293
294To run a PuTTY session saved under the name \q{\cw{mysession}},
295create a Windows shortcut that invokes PuTTY with a command line
296like
297
298\c \path\name\to\putty.exe @mysession
299
a1d2976b 300\S{faq-startssh}{Question} How can I start an SSH session straight
70706890 301from the command line?
ee46ef84 302
303Use the command line \c{putty -ssh host.name}. Alternatively, create
304a saved session that specifies the SSH protocol, and start the saved
305session as shown in \k{faq-startsess}.
306
a1d2976b 307\S{faq-cutpaste}{Question} How do I copy and paste between PuTTY and
70706890 308other Windows applications?
ee46ef84 309
310Copy and paste works similarly to the X Window System. You use the
311left mouse button to select text in the PuTTY window. The act of
312selection \e{automatically} copies the text to the clipboard: there
313is no need to press Ctrl-Ins or Ctrl-C or anything else. In fact,
314pressing Ctrl-C will send a Ctrl-C character to the other end of
315your connection (just like it does the rest of the time), which may
316have unpleasant effects. The \e{only} thing you need to do, to copy
317text to the clipboard, is to select it.
318
319To paste the clipboard contents into a PuTTY window, by default you
320click the right mouse button. If you have a three-button mouse and
321are used to X applications, you can configure pasting to be done by
322the middle button instead, but this is not the default because most
323Windows users don't have a middle button at all.
324
325You can also paste by pressing Shift-Ins.
326
a1d2976b 327\S{faq-tunnels}{Question} How do I use X forwarding and port
70706890 328forwarding? I can't find the Tunnels panel.
f2003e32 329
330If you're looking in the 0.51 release or earlier, the Tunnels panel
331isn't there. It was added in the development snapshots after 0.51,
332and releases 0.52 and onwards will contain it.
333
a1d2976b 334\S{faq-options}{Question} How do I use all PuTTY's features (public
70706890 335keys, port forwarding, SSH v2, etc.) in PSCP, PSFTP and Plink?
72be5b5e 336
337The command-line tools are currently rather short of command line
338options to enable this sort of thing. However, you can use most of
339PuTTY's features if you create a PuTTY saved session, and then use
340the name of the saved session on the command line in place of a
341hostname. This works for PSCP, PSFTP and Plink (but don't expect
342port forwarding in the file transfer applications!).
f2003e32 343
a1d2976b 344\S{faq-pscp}{Question} How do I use PSCP.EXE? When I double-click it
70706890 345gives me a command prompt window which then closes instantly.
ee46ef84 346
347PSCP is a command-line application, not a GUI application. If you
348run it without arguments, it will simply print a help message and
349terminate.
350
351To use PSCP properly, run it from a Command Prompt window. See
352\k{pscp} in the documentation for more details.
353
a1d2976b 354\S{faq-pscp-spaces}{Question} How do I use PSCP to copy a file whose
70706890 355name has spaces in?
ee46ef84 356
357If PSCP is using the traditional SCP protocol, this is confusing. If
358you're specifying a file at the local end, you just use one set of
359quotes as you would normally do:
360
361\c pscp "local filename with spaces" user@host:
362\c pscp user@host:myfile "local filename with spaces"
363
364But if the filename you're specifying is on the \e{remote} side, you
365have to use backslashes and two sets of quotes:
366
367\c pscp user@host:"\"remote filename with spaces\"" local_filename
368\c pscp local_filename user@host:"\"remote filename with spaces\""
369
370Worse still, in a remote-to-local copy you have to specify the local
371file name explicitly, otherwise PSCP will complain that they don't
372match (unless you specified the \c{-unsafe} option). The following
373command will give an error message:
374
375\c c:\>pscp user@host:"\"oo er\"" .
e9cee352 376\c warning: remote host tried to write to a file called 'oo er'
377\c when we requested a file called '"oo er"'.
ee46ef84 378
e9cee352 379Instead, you need to specify the local file name in full:
380
381\c c:\>pscp user@host:"\"oo er\"" "oo er"
382
ee46ef84 383If PSCP is using the newer SFTP protocol, none of this is a problem,
384and all filenames with spaces in are specified using a single pair
385of quotes in the obvious way:
386
387\c pscp "local file" user@host:
388\c pscp user@host:"remote file" .
389
390\H{faq-trouble} Troubleshooting
391
a1d2976b 392\S{faq-mac}{Question} Why do I see \q{Incorrect MAC received on
70706890 393packet}?
ee46ef84 394
395This is due to a bug in old SSH 2 servers distributed by
396\cw{ssh.com}. Version 2.3.0 and below of their SSH 2 server
397constructs Message Authentication Codes in the wrong way, and
398expects the client to construct them in the same wrong way. PuTTY
399constructs the MACs correctly by default, and hence these old
400servers will fail to work with it.
401
402If you are using PuTTY version 0.51 or below, go to the SSH panel
403and check the box labelled \q{Imitate SSH 2 MAC bug}. This will
404cause PuTTY to construct its MACs in the same incorrect manner as
405the buggy servers, so it will be able to work with them.
406
407Since version 0.51, PuTTY has been enhanced to detect buggy servers
408automatically (when they announce their version) and enable the
409workaround without the user needing to ask. Therefore you \e{should}
410never have to use this option again after 0.52, but it is still
411provided just in case another buggy server shows up.
412
b7e2c163 413In this context MAC stands for Message Authentication Code. It's a
414cryptographic term, and it has nothing at all to do with Ethernet
415MAC (Media Access Control) addresses.
416
a1d2976b 417\S{faq-colours}{Question} I clicked on a colour in the Colours
70706890 418panel, and the colour didn't change in my terminal.
ee46ef84 419
420That isn't how you're supposed to use the Colours panel.
421
422During the course of a session, PuTTY potentially uses \e{all} the
423colours listed in the Colours panel. It's not a question of using
424only one of them and you choosing which one; PuTTY will use them
425\e{all}. The purpose of the Colours panel is to let you adjust the
426appearance of all the colours. So to change the colour of the
427cursor, for example, you would select \q{Cursor Colour}, press the
428\q{Modify} button, and select a new colour from the dialog box that
429appeared. Similarly, if you want your session to appear in green,
430you should select \q{Default Foreground} and press \q{Modify}.
431Clicking on \q{ANSI Green} won't turn your session green; it will
432only allow you to adjust the \e{shade} of green used when PuTTY is
433instructed by the server to display green text.
434
a1d2976b 435\S{faq-winsock2}{Question} Plink on Windows 95 says it can't find
70706890 436\cw{WS2_32.DLL}.
ee46ef84 437
438Plink requires the extended Windows network library, WinSock version
4392. This is installed as standard on Windows 98 and above, and on
440Windows NT, and even on later versions of Windows 95; but early
441Win95 installations don't have it.
442
443In order to use Plink on these systems, you will need to download
444the
445\W{http://www.microsoft.com/windows95/downloads/contents/wuadmintools/s_wunetworkingtools/w95sockets2/}{WinSock 2 upgrade}:
446
447\c http://www.microsoft.com/windows95/downloads/contents/wuadmintools/
448\c s_wunetworkingtools/w95sockets2/
449
a1d2976b 450\S{faq-rekey}{Question} My PuTTY sessions close after an hour and
70706890 451tell me \q{Server failed host key check}.
ee46ef84 452
453This is a bug in all versions of PuTTY up to and including 0.51. SSH
454v2 servers from \cw{ssh.com} will require the key exchange to be
455repeated one hour after the start of the connection, and PuTTY will
456get this wrong.
457
458The bug has been fixed since version 0.51, so upgrading to a later
459version or snapshot should solve the problem.
460
a1d2976b 461\S{faq-outofmem}{Question} After trying to establish an SSH 2
70706890 462connection, PuTTY says \q{Out of memory} and dies.
ee46ef84 463
464If this happens just while the connection is starting up, this often
465indicates that for some reason the client and server have failed to
466establish a session encryption key. Somehow, they have performed
467calculations that should have given each of them the same key, but
468have ended up with different keys; so data encrypted by one and
469decrypted by the other looks like random garbage.
470
471This causes an \q{out of memory} error because the first encrypted
472data PuTTY expects to see is the length of an SSH message. Normally
473this will be something well under 100 bytes. If the decryption has
474failed, PuTTY will see a completely random length in the region of
475two \e{gigabytes}, and will try to allocate enough memory to store
476this non-existent message. This will immediately lead to it thinking
477it doesn't have enough memory, and panicking.
478
479If this happens to you, it is quite likely to still be a PuTTY bug
480and you should report it (although it might be a bug in your SSH
481server instead); but it doesn't necessarily mean you've actually run
482out of memory.
483
a1d2976b 484\S{faq-bce}{Question} When I run full-colour applications, I see
70706890 485areas of black space where colour ought to be.
f1453e5c 486
487You almost certainly need to enable the \q{Use background colour to
488erase screen} setting in the Terminal panel. Note that if you do
489this in mid-session, it won't take effect until you reset the
490terminal (see \k{faq-resetterm}).
491
a1d2976b 492\S{faq-resetterm}{Question} When I change some terminal settings,
70706890 493nothing happens.
f1453e5c 494
495Some of the terminal options (notably Auto Wrap and
496background-colour screen erase) actually represent the \e{default}
497setting, rather than the currently active setting. The server can
498send sequences that modify these options in mid-session, but when
499the terminal is reset (by server action, or by you choosing \q{Reset
500Terminal} from the System menu) the defaults are restored.
501
502If you want to change one of these options in the middle of a
503session, you will find that the change does not immediately take
504effect. It will only take effect once you reset the terminal.
505
a1d2976b 506\S{faq-altgr}{Question} I can't type characters that require the
70706890 507AltGr key.
ee46ef84 508
509In PuTTY version 0.51, the AltGr key was broken. The bug has been
510fixed since then.
511
a1d2976b 512\S{faq-idleout}{Question} My PuTTY sessions unexpectedly close after
70706890 513they are idle for a while.
ee46ef84 514
515Some types of firewall, and almost any router doing Network Address
516Translation (NAT, also known as IP masquerading), will forget about
517a connection through them if the connection does nothing for too
518long. This will cause the connection to be rudely cut off when
519contact is resumed.
520
521You can try to combat this by telling PuTTY to send \e{keepalives}:
522packets of data which have no effect on the actual session, but
523which reassure the router or firewall that the network connection is
524still active and worth remembering about.
525
526Keepalives don't solve everything, unfortunately; although they
527cause greater robustness against this sort of router, they can also
528cause a \e{loss} of robustness against network dropouts. See
529\k{config-keepalive} in the documentation for more discussion of
530this.
531
a1d2976b 532\S{faq-timeout}{Question} PuTTY's network connections time out too
70706890 533quickly when network connectivity is temporarily lost.
ee46ef84 534
535This is a Windows problem, not a PuTTY problem. The timeout value
536can't be set on per application or per session basis. To increase
537the TCP timeout globally, you need to tinker with the Registry.
538
539On Windows 95, 98 or ME, the registry key you need to change is
540
541\c HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\
542\c MSTCP\MaxDataRetries
543
544(it must be of type DWORD in Win95, or String in Win98/ME).
545
546On Windows NT or 2000, the registry key is
547
548\c HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\
549\c Parameters\TcpMaxDataRetransmissions
550
551and it must be of type DWORD.
552
553Set the key's value to something like 10. This will cause Windows to
554try harder to keep connections alive instead of abandoning them.
555
a1d2976b 556\S{faq-puttyputty}{Question} When I \cw{cat} a binary file, I get
ee46ef84 557`PuTTYPuTTYPuTTY' on my command line.
558
a5a6cb30 559Don't do that, then.
ee46ef84 560
561This is designed behaviour; when PuTTY receives the character
562Control-E from the remote server, it interprets it as a request to
563identify itself, and so it sends back the string \q{\cw{PuTTY}} as
564if that string had been entered at the keyboard. Control-E should
565only be sent by programs that are prepared to deal with the
566response. Writing a binary file to your terminal is likely to output
567many Control-E characters, and cause this behaviour. Don't do it.
568It's a bad plan.
569
a5a6cb30 570To mitigate the effects, you could configure the answerback string
571to be empty (see \k{config-answerback}); but writing binary files to
572your terminal is likely to cause various other unpleasant behaviour,
573so this is only a small remedy.
574
a1d2976b 575\S{faq-puttyputty}{Question} When I \cw{cat} a binary file, my
70706890 576window title changes to a nonsense string.
ee46ef84 577
a5a6cb30 578Don't do that, then.
ee46ef84 579
580It is designed behaviour that PuTTY should have the ability to
581adjust the window title on instructions from the server. Normally
582the control sequence that does this should only be sent
583deliberately, by programs that know what they are doing and intend
584to put meaningful text in the window title. Writing a binary file to
585your terminal runs the risk of sending the same control sequence by
586accident, and cause unexpected changes in the window title. Don't do
587it.
588
a1d2976b 589\S{faq-password}{Question} My keyboard stops working once PuTTY
70706890 590displays the password prompt.
59c1f1f6 591
592No, it doesn't. PuTTY just doesn't display the password you type, so
593that someone looking at your screen can't see what it is.
594
595Unlike the Windows login prompts, PuTTY doesn't display the password
596as a row of asterisks either. This is so that someone looking at
597your screen can't even tell how \e{long} your password is, which
598might be valuable information.
599
ee46ef84 600\H{faq-secure} Security questions
601
a1d2976b 602\S{faq-publicpc}{Question} Is it safe for me to download PuTTY and
70706890 603use it on a public PC?
ee46ef84 604
605It depends on whether you trust that PC. If you don't trust the
606public PC, don't use PuTTY on it, and don't use any other software
607you plan to type passwords into either. It might be watching your
608keystrokes, or it might tamper with the PuTTY binary you download.
609There is \e{no} program safe enough that you can run it on an
610actively malicious PC and get away with typing passwords into it.
611
612If you do trust the PC, then it's probably OK to use PuTTY on it
613(but if you don't trust the network, then the PuTTY download might
614be tampered with, so it would be better to carry PuTTY with you on a
615floppy).
616
a1d2976b 617\S{faq-cleanup}{Question} What does PuTTY leave on a system? How can
70706890 618I clean up after it?
ee46ef84 619
620PuTTY will leave some Registry entries, and a random seed file, on
621the PC (see \k{faq-settings}). If you are using PuTTY on a public
622PC, or somebody else's PC, you might want to clean these up when you
623leave. You can do that automatically, by running the command
624\c{putty -cleanup}.
625
a1d2976b 626\S{faq-dsa}{Question} How come PuTTY now supports DSA, when the
70706890 627website used to say how insecure it was?
ee46ef84 628
629DSA has a major weakness \e{if badly implemented}: it relies on a
630random number generator to far too great an extent. If the random
631number generator produces a number an attacker can predict, the DSA
632private key is exposed - meaning that the attacker can log in as you
633on all systems that accept that key.
634
635The PuTTY policy changed because the developers were informed of
636ways to implement DSA which do not suffer nearly as badly from this
637weakness, and indeed which don't need to rely on random numbers at
638all. For this reason we now believe PuTTY's DSA implementation is
639probably OK. However, if you have the choice, we still recommend you
640use RSA instead.
641
642\H{faq-admin} Administrative questions
643
a1d2976b 644\S{faq-domain}{Question} Would you like me to register you a nicer
70706890 645domain name?
ee46ef84 646
647No, thank you. Even if you can find one (most of them seem to have
648been registered already, by people who didn't ask whether we
649actually wanted it before they applied), we're happy with the PuTTY
650web site being exactly where it is. It's not hard to find (just type
651\q{putty} into \W{http://www.google.com/}{google.com} and we're the
652first link returned), and we don't believe the administrative hassle
653of moving the site would be worth the benefit.
654
655In addition, if we \e{did} want a custom domain name, we would want
656to run it ourselves, so we knew for certain that it would continue
657to point where we wanted it, and wouldn't suddenly change or do
658strange things. Having it registered for us by a third party who we
659don't even know is not the best way to achieve this.
660
a1d2976b 661\S{faq-webhosting}{Question} Would you like free web hosting for the
70706890 662PuTTY web site?
ee46ef84 663
664We already have some, thanks.
665
a1d2976b 666\S{faq-sourceforge}{Question} Why don't you move PuTTY to
70706890 667SourceForge?
ee46ef84 668
669Partly, because we don't want to move the web site location (see
670\k{faq-domain}).
671
672Also, security reasons. PuTTY is a security product, and as such it
673is particularly important to guard the code and the web site against
674unauthorised modifications which might introduce subtle security
675flaws. Therefore, we prefer that the CVS repository, web site and
676FTP site remain where they are, under the direct control of system
677administrators we know and trust personally, rather than being run
678by a large organisation full of people we've never met and which is
679known to have had breakins in the past.
680
681No offence to SourceForge; I think they do a wonderful job. But
682they're not ideal for everyone, and in particular they're not ideal
683for us.
684
a1d2976b 685\S{faq-mailinglist1}{Question} Why can't I subscribe to the
70706890 686putty-bugs mailing list?
ee46ef84 687
688Because you're not a member of the PuTTY core development team. The
689putty-bugs mailing list is not a general newsgroup-like discussion
690forum; it's a contact address for the core developers, and an
691\e{internal} mailing list for us to discuss things among ourselves.
692If we opened it up for everybody to subscribe to, it would turn into
693something more like a newsgroup and we would be completely
694overwhelmed by the volume of traffic. It's hard enough to keep up
695with the list as it is.
696
a1d2976b 697\S{faq-mailinglist2}{Question} If putty-bugs isn't a
70706890 698general-subscription mailing list, what is?
ee46ef84 699
700There isn't one, that we know of.
701
702If someone else wants to set up a mailing list for PuTTY users to
703help each other with common problems, that would be fine with us;
704but the PuTTY team would almost certainly not have the time to read
705it, so any questions the list couldn't answer would have to be
706forwarded on to us by the questioner. In any case, it's probably
707better to use the established newsgroup \cw{comp.security.ssh} for
708this purpose.
709
a1d2976b 710\S{faq-donations}{Question} How can I donate to PuTTY development?
ee46ef84 711
712Please, \e{please} don't feel you have to. PuTTY is completely free
713software, and not shareware. We think it's very important that
714\e{everybody} who wants to use PuTTY should be able to, whether they
715have any money or not; so the last thing we would want is for a
716PuTTY user to feel guilty because they haven't paid us any money. If
717you want to keep your money, please do keep it. We wouldn't dream of
718asking for any.
719
720Having said all that, if you still really \e{want} to give us money,
721we won't argue :-) The easiest way for us to accept donations is if
722you go to \W{http://www.e-gold.com}\cw{www.e-gold.com}, and deposit
723your donation in account number 174769. Then send us e-mail to let
724us know you've done so (otherwise we might not notice for months!).
725
726Small donations (tens of dollars or tens of euros) will probably be
727spent on beer or curry, which helps motivate our volunteer team to
728continue doing this for the world. Larger donations will be spent on
729something that actually helps development, if we can find anything
730(perhaps new hardware, or a copy of Windows 2000), but if we can't
731find anything then we'll just distribute the money among the
732developers. If you want to be sure your donation is going towards
733something worthwhile, ask us first. If you don't like these terms,
734feel perfectly free not to donate. We don't mind.
735
a1d2976b 736\S{faq-pronounce}{Question} How do I pronounce PuTTY?
ee46ef84 737
738Exactly like the normal word \q{putty}. Just like the stuff you put
739on window frames. (One of the reasons it's called PuTTY is because
740it makes Windows usable. :-)