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1 | \versionid $Id: faq.but,v 1.14 2001/12/14 12:48:24 simon Exp $ |
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2 | |
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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 | |
a1d2976b |
27 | \S{faq-ssh2}{Question} Does PuTTY support SSH v2? |
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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 has been |
35 | added since version 0.51. |
36 | |
a1d2976b |
37 | \S{faq-ssh2-keyfmt}{Question} Does PuTTY support reading OpenSSH or |
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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 | |
a1d2976b |
45 | \S{faq-ssh1}{Question} Does PuTTY support SSH v1? |
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46 | |
47 | Yes. SSH 1 support has always been available in PuTTY. |
48 | |
a1d2976b |
49 | \S{faq-localecho}{Question} Does PuTTY support local echo? |
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50 | |
51 | Yes. |
52 | |
53 | In version 0.51 and before, local echo cannot 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). The two features can be enabled and disabled from the Terminal |
58 | panel, using the checkbox marked \q{Use local terminal line |
59 | discipline}. Note that due to a bug in those versions of PuTTY, |
60 | changing this feature in mid-session will have no effect; you have |
61 | to enable it \e{before} you open the connection. |
62 | |
63 | In later versions, local echo and local line editing are separate |
64 | options, and by default PuTTY will try to determine automatically |
65 | whether to enable them or not, based on which protocol you have |
66 | selected and also based on hints from the server. If you have a |
67 | problem with PuTTY's default choice, you can force each option to be |
68 | enabled or disabled as you choose. The controls are in the Terminal |
69 | panel, in the section marked \q{Line discipline options}. |
70 | |
a1d2976b |
71 | \S{faq-disksettings}{Question} Does PuTTY support storing its |
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72 | settings in a disk file? |
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73 | |
74 | Not at present, although \k{config-file} in the documentation gives |
75 | a method of achieving the same effect. |
76 | |
a1d2976b |
77 | \S{faq-fullscreen}{Question} Does PuTTY support full-screen mode, |
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78 | like a DOS box? |
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79 | |
80 | Not in the 0.51 release, but it has been added since then. |
81 | |
babac7bd |
82 | \S{faq-password-remember}{Question} Does PuTTY have the ability to |
83 | remember my password so I don't have to type it every time? |
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84 | |
85 | No, it doesn't. |
86 | |
87 | Remembering your password is a bad plan for obvious security |
88 | reasons: anyone who gains access to your machine while you're away |
89 | from your desk can find out the remembered password, and use it, |
90 | abuse it or change it. |
91 | |
92 | In addition, it's not even \e{possible} for PuTTY to automatically |
93 | send your password in a Telnet session, because Telnet doesn't give |
94 | the client software any indication of which part of the login |
95 | process is the password prompt. PuTTY would have to guess, by |
96 | looking for words like \q{password} in the session data; and if your |
97 | login program is written in something other than English, this won't |
98 | work. |
99 | |
100 | In SSH, remembering your password would be possible in theory, but |
101 | there doesn't seem to be much point since SSH supports public key |
102 | authentication, which is more flexible and more secure. See |
103 | \k{pubkey} in the documentation for a full discussion of public key |
104 | authentication. |
105 | |
a1d2976b |
106 | \S{faq-hostkeys}{Question} Is there an option to turn off the |
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107 | annoying host key prompts? |
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108 | |
109 | No, there isn't. And there won't be. Even if you write it yourself |
110 | and send us the patch, we won't accept it. |
111 | |
112 | Those annoying host key prompts are the \e{whole point} of SSH. |
113 | Without them, all the cryptographic technology SSH uses to secure |
114 | your session is doing nothing more than making an attacker's job |
115 | slightly harder; instead of sitting between you and the server with |
116 | a packet sniffer, the attacker must actually subvert a router and |
117 | start modifying the packets going back and forth. But that's not all |
118 | that much harder than just sniffing; and without host key checking, |
119 | it will go completely undetected by client or server. |
120 | |
121 | Host key checking is your guarantee that the encryption you put on |
122 | your data at the client end is the \e{same} encryption taken off the |
123 | data at the server end; it's your guarantee that it hasn't been |
124 | removed and replaced somewhere on the way. Host key checking makes |
125 | the attacker's job \e{astronomically} hard, compared to packet |
126 | sniffing, and even compared to subverting a router. Instead of |
127 | applying a little intelligence and keeping an eye on Bugtraq, the |
128 | attacker must now perform a brute-force attack against at least one |
129 | military-strength cipher. That insignificant host key prompt really |
130 | does make \e{that} much difference. |
131 | |
132 | If you're having a specific problem with host key checking - perhaps |
133 | you want an automated batch job to make use of PSCP or Plink, and |
134 | the interactive host key prompt is hanging the batch process - then |
135 | the right way to fix it is to add the correct host key to the |
136 | Registry in advance. That way, you retain the \e{important} feature |
137 | of host key checking: the right key will be accepted and the wrong |
138 | ones will not. Adding an option to turn host key checking off |
139 | completely 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 |
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142 | suite, to go with the client? |
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143 | |
144 | No. The only reason we might want to would be if we could easily |
145 | re-use existing code and significantly cut down the effort. We don't |
146 | believe this is the case; there just isn't enough common ground |
147 | between an SSH client and server to make it worthwhile. |
148 | |
149 | If someone else wants to use bits of PuTTY in the process of writing |
150 | a Windows SSH server, they'd be perfectly welcome to of course, but |
151 | I really can't see it being a lot less effort for us to do that than |
152 | it would be for us to write a server from the ground up. We don't |
153 | have time, and we don't have motivation. The code is available if |
154 | anyone else wants to try it. |
155 | |
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156 | \H{faq-ports} Ports to other operating systems |
157 | |
158 | The eventual goal is for PuTTY to be a multi-platform program, able |
159 | to run on at least Windows, MacOS and Unix. Whether this will |
160 | actually ever happen I have no idea, but it is the plan. A Mac port |
161 | has been started, but is only half-finished and currently not moving |
162 | very fast. |
163 | |
164 | Porting will become easier once PuTTY has a generalised porting |
165 | layer, drawing a clear line between platform-dependent and |
166 | platform-independent code. The general intention is for this porting |
167 | layer to evolve naturally as part of the process of doing the first |
168 | port. One particularly nasty part of this will be separating the |
169 | many configuration options into platform-dependent and |
170 | platform-independent ones; for example, the options controlling when |
171 | the Windows System menu appears will be pretty much meaningless |
172 | under X11 or perhaps other windowing systems, whereas Telnet Passive |
173 | Mode is universal and shouldn't need to be specified once for each |
174 | platform. |
175 | |
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176 | \S{faq-wince}{Question} Will there be a port to Windows CE? |
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177 | |
178 | Probably not in the particularly near future. Despite sharing large |
179 | parts of the Windows API, in practice WinCE doesn't appear to be |
180 | significantly easier to port to than a totally different operating |
181 | system. |
182 | |
183 | However, PuTTY on portable devices would clearly be a useful thing, |
184 | so in the long term I hope there will be a WinCE port. |
185 | |
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186 | \S{faq-mac-port}{Question} Will there be a port to the Mac? |
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187 | |
188 | A Mac port was started once and is half-finished, but development |
189 | has been static for some time and the main PuTTY code has moved on, |
190 | so it's not clear how quickly development would resume even if |
191 | developer effort were available. |
192 | |
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193 | \S{faq-unix}{Question} Will there be a port to Unix? |
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194 | |
195 | I hope so, if only so that I can have an \cw{xterm}-like program |
196 | that supports exactly the same terminal emulation as PuTTY. If and |
197 | when we do do a Unix port, it will have a local-terminal back end so |
198 | it can be used like an \cw{xterm}, rather than only being usable as |
199 | a network utility. |
200 | |
a1d2976b |
201 | \S{faq-epoc}{Question} Will there be a port to EPOC? |
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202 | |
203 | I hope so, but given that ports aren't really progressing very fast |
204 | even on systems the developers \e{do} already know how to program |
205 | for, it might be a long time before any of us get round to learning |
206 | a 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? |
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211 | |
212 | No, it isn't. It would take a reasonable amount of rewriting for |
213 | this to be possible, and since the PuTTY project itself doesn't |
214 | believe in DLLs (they make installation more error-prone) none of us |
215 | has taken the time to do it. |
216 | |
217 | Most of the code cleanup work would be a good thing to happen in |
218 | general, 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 |
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221 | Basic component? |
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222 | |
223 | No, it isn't. None of the PuTTY team uses Visual Basic, and none of |
224 | us has any particular need to make SSH connections from a Visual |
225 | Basic application. In addition, all the preliminary work to turn it |
226 | into a DLL would be necessary first; and furthermore, we don't even |
227 | know how to write VB components. |
228 | |
229 | If someone offers to do some of this work for us, we might consider |
230 | it, but unless that happens I can't see VB integration being |
231 | anywhere 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 |
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234 | from within another program? |
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235 | |
236 | Probably your best bet is to use Plink, the command-line connection |
237 | tool. If you can start Plink as a second Windows process, and |
238 | arrange for your primary process to be able to send data to the |
239 | Plink process, and receive data from it, through pipes, then you |
240 | should be able to make SSH connections from your program. |
241 | |
242 | This 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? |
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247 | |
248 | For most purposes, PuTTY can be considered to be an \cw{xterm} |
249 | terminal, although full support for some of \cw{xterm}'s features, |
250 | such as passing mouse actions to the server-side program, is not |
251 | present in the 0.51 release (but has been added since). |
252 | |
253 | PuTTY also supports some terminal control sequences not supported by |
254 | the real \cw{xterm}: notably the Linux console sequences that |
255 | reconfigure the colour palette, and the title bar control sequences |
256 | used by \cw{DECterm} (which are different from the \cw{xterm} ones; |
257 | PuTTY supports both). |
258 | |
259 | By default, PuTTY announces its terminal type to the server as |
260 | \c{xterm}. If you have a problem with this, you can reconfigure it |
261 | to say something else; \c{vt220} might help if you have trouble. |
262 | |
a1d2976b |
263 | \S{faq-settings}{Question} Where does PuTTY store its data? |
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264 | |
265 | PuTTY stores most of its data (saved sessions, SSH host keys) in the |
266 | Registry. The precise location is |
267 | |
268 | \c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY |
269 | |
270 | and within that area, saved sessions are stored under \c{Sessions} |
271 | while host keys are stored under \c{SshHostKeys}. |
272 | |
273 | PuTTY also requires a random number seed file, to improve the |
274 | unpredictability of randomly chosen data needed as part of the SSH |
275 | cryptography. This is stored by default in your Windows home |
276 | directory (\c{%HOMEDRIVE%\\%HOMEPATH%}), or in the actual Windows |
277 | directory (such as \c{C:\\WINDOWS}) if the home directory doesn't |
278 | exist, for example if you're using Win95. If you want to change the |
279 | location of the random number seed file, you can put your chosen |
280 | pathname in the Registry, at |
281 | |
282 | \c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\RandSeedFile |
283 | |
284 | \H{faq-howto} HOWTO questions |
285 | |
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286 | \S{faq-startmax}{Question} How can I make PuTTY start up maximised? |
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287 | |
288 | Create a Windows shortcut to start PuTTY from, and set it as \q{Run |
289 | Maximized}. |
290 | |
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291 | \S{faq-startsess}{Question} How can I create a Windows shortcut to |
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292 | start a particular saved session directly? |
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293 | |
294 | To run a PuTTY session saved under the name \q{\cw{mysession}}, |
295 | create a Windows shortcut that invokes PuTTY with a command line |
296 | like |
297 | |
298 | \c \path\name\to\putty.exe @mysession |
299 | |
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300 | \S{faq-startssh}{Question} How can I start an SSH session straight |
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301 | from the command line? |
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302 | |
303 | Use the command line \c{putty -ssh host.name}. Alternatively, create |
304 | a saved session that specifies the SSH protocol, and start the saved |
305 | session as shown in \k{faq-startsess}. |
306 | |
a1d2976b |
307 | \S{faq-cutpaste}{Question} How do I copy and paste between PuTTY and |
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308 | other Windows applications? |
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309 | |
310 | Copy and paste works similarly to the X Window System. You use the |
311 | left mouse button to select text in the PuTTY window. The act of |
312 | selection \e{automatically} copies the text to the clipboard: there |
313 | is no need to press Ctrl-Ins or Ctrl-C or anything else. In fact, |
314 | pressing Ctrl-C will send a Ctrl-C character to the other end of |
315 | your connection (just like it does the rest of the time), which may |
316 | have unpleasant effects. The \e{only} thing you need to do, to copy |
317 | text to the clipboard, is to select it. |
318 | |
319 | To paste the clipboard contents into a PuTTY window, by default you |
320 | click the right mouse button. If you have a three-button mouse and |
321 | are used to X applications, you can configure pasting to be done by |
322 | the middle button instead, but this is not the default because most |
323 | Windows users don't have a middle button at all. |
324 | |
325 | You can also paste by pressing Shift-Ins. |
326 | |
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327 | \S{faq-tunnels}{Question} How do I use X forwarding and port |
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328 | forwarding? I can't find the Tunnels panel. |
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329 | |
330 | If you're looking in the 0.51 release or earlier, the Tunnels panel |
331 | isn't there. It was added in the development snapshots after 0.51, |
332 | and releases 0.52 and onwards will contain it. |
333 | |
a1d2976b |
334 | \S{faq-options}{Question} How do I use all PuTTY's features (public |
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335 | keys, port forwarding, SSH v2, etc.) in PSCP, PSFTP and Plink? |
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336 | |
337 | The command-line tools are currently rather short of command line |
338 | options to enable this sort of thing. However, you can use most of |
339 | PuTTY's features if you create a PuTTY saved session, and then use |
340 | the name of the saved session on the command line in place of a |
341 | hostname. This works for PSCP, PSFTP and Plink (but don't expect |
342 | port forwarding in the file transfer applications!). |
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343 | |
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344 | \S{faq-pscp}{Question} How do I use PSCP.EXE? When I double-click it |
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345 | gives me a command prompt window which then closes instantly. |
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346 | |
347 | PSCP is a command-line application, not a GUI application. If you |
348 | run it without arguments, it will simply print a help message and |
349 | terminate. |
350 | |
351 | To use PSCP properly, run it from a Command Prompt window. See |
352 | \k{pscp} in the documentation for more details. |
353 | |
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354 | \S{faq-pscp-spaces}{Question} How do I use PSCP to copy a file whose |
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355 | name has spaces in? |
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356 | |
357 | If PSCP is using the traditional SCP protocol, this is confusing. If |
358 | you're specifying a file at the local end, you just use one set of |
359 | quotes 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 | |
364 | But if the filename you're specifying is on the \e{remote} side, you |
365 | have 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 | |
370 | Worse still, in a remote-to-local copy you have to specify the local |
371 | file name explicitly, otherwise PSCP will complain that they don't |
372 | match (unless you specified the \c{-unsafe} option). The following |
373 | command will give an error message: |
374 | |
375 | \c c:\>pscp user@host:"\"oo er\"" . |
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376 | \c warning: remote host tried to write to a file called 'oo er' |
377 | \c when we requested a file called '"oo er"'. |
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378 | |
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379 | Instead, you need to specify the local file name in full: |
380 | |
381 | \c c:\>pscp user@host:"\"oo er\"" "oo er" |
382 | |
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383 | If PSCP is using the newer SFTP protocol, none of this is a problem, |
384 | and all filenames with spaces in are specified using a single pair |
385 | of 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 | |
babac7bd |
392 | \S{faq-incorrect-mac}{Question} Why do I see \q{Incorrect MAC |
393 | received on packet}? |
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394 | |
395 | This 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 |
397 | constructs Message Authentication Codes in the wrong way, and |
398 | expects the client to construct them in the same wrong way. PuTTY |
399 | constructs the MACs correctly by default, and hence these old |
400 | servers will fail to work with it. |
401 | |
402 | If you are using PuTTY version 0.51 or below, go to the SSH panel |
403 | and check the box labelled \q{Imitate SSH 2 MAC bug}. This will |
404 | cause PuTTY to construct its MACs in the same incorrect manner as |
405 | the buggy servers, so it will be able to work with them. |
406 | |
407 | Since version 0.51, PuTTY has been enhanced to detect buggy servers |
408 | automatically (when they announce their version) and enable the |
409 | workaround without the user needing to ask. Therefore you \e{should} |
410 | never have to use this option again after 0.52, but it is still |
411 | provided just in case another buggy server shows up. |
412 | |
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413 | In this context MAC stands for Message Authentication Code. It's a |
414 | cryptographic term, and it has nothing at all to do with Ethernet |
415 | MAC (Media Access Control) addresses. |
416 | |
a1d2976b |
417 | \S{faq-colours}{Question} I clicked on a colour in the Colours |
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418 | panel, and the colour didn't change in my terminal. |
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419 | |
420 | That isn't how you're supposed to use the Colours panel. |
421 | |
422 | During the course of a session, PuTTY potentially uses \e{all} the |
423 | colours listed in the Colours panel. It's not a question of using |
424 | only 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 |
426 | appearance of all the colours. So to change the colour of the |
427 | cursor, for example, you would select \q{Cursor Colour}, press the |
428 | \q{Modify} button, and select a new colour from the dialog box that |
429 | appeared. Similarly, if you want your session to appear in green, |
430 | you should select \q{Default Foreground} and press \q{Modify}. |
431 | Clicking on \q{ANSI Green} won't turn your session green; it will |
432 | only allow you to adjust the \e{shade} of green used when PuTTY is |
433 | instructed by the server to display green text. |
434 | |
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435 | \S{faq-winsock2}{Question} Plink on Windows 95 says it can't find |
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436 | \cw{WS2_32.DLL}. |
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437 | |
438 | Plink requires the extended Windows network library, WinSock version |
439 | 2. This is installed as standard on Windows 98 and above, and on |
440 | Windows NT, and even on later versions of Windows 95; but early |
441 | Win95 installations don't have it. |
442 | |
443 | In order to use Plink on these systems, you will need to download |
444 | the |
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 |
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451 | tell me \q{Server failed host key check}. |
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452 | |
453 | This is a bug in all versions of PuTTY up to and including 0.51. SSH |
454 | v2 servers from \cw{ssh.com} will require the key exchange to be |
455 | repeated one hour after the start of the connection, and PuTTY will |
456 | get this wrong. |
457 | |
458 | The bug has been fixed since version 0.51, so upgrading to a later |
459 | version or snapshot should solve the problem. |
460 | |
a1d2976b |
461 | \S{faq-outofmem}{Question} After trying to establish an SSH 2 |
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462 | connection, PuTTY says \q{Out of memory} and dies. |
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463 | |
464 | If this happens just while the connection is starting up, this often |
465 | indicates that for some reason the client and server have failed to |
466 | establish a session encryption key. Somehow, they have performed |
467 | calculations that should have given each of them the same key, but |
468 | have ended up with different keys; so data encrypted by one and |
469 | decrypted by the other looks like random garbage. |
470 | |
471 | This causes an \q{out of memory} error because the first encrypted |
472 | data PuTTY expects to see is the length of an SSH message. Normally |
473 | this will be something well under 100 bytes. If the decryption has |
474 | failed, PuTTY will see a completely random length in the region of |
475 | two \e{gigabytes}, and will try to allocate enough memory to store |
476 | this non-existent message. This will immediately lead to it thinking |
477 | it doesn't have enough memory, and panicking. |
478 | |
479 | If this happens to you, it is quite likely to still be a PuTTY bug |
480 | and you should report it (although it might be a bug in your SSH |
481 | server instead); but it doesn't necessarily mean you've actually run |
482 | out of memory. |
483 | |
a1d2976b |
484 | \S{faq-bce}{Question} When I run full-colour applications, I see |
70706890 |
485 | areas of black space where colour ought to be. |
f1453e5c |
486 | |
487 | You almost certainly need to enable the \q{Use background colour to |
488 | erase screen} setting in the Terminal panel. Note that if you do |
489 | this in mid-session, it won't take effect until you reset the |
490 | terminal (see \k{faq-resetterm}). |
491 | |
a1d2976b |
492 | \S{faq-resetterm}{Question} When I change some terminal settings, |
70706890 |
493 | nothing happens. |
f1453e5c |
494 | |
495 | Some of the terminal options (notably Auto Wrap and |
496 | background-colour screen erase) actually represent the \e{default} |
497 | setting, rather than the currently active setting. The server can |
498 | send sequences that modify these options in mid-session, but when |
499 | the terminal is reset (by server action, or by you choosing \q{Reset |
500 | Terminal} from the System menu) the defaults are restored. |
501 | |
502 | If you want to change one of these options in the middle of a |
503 | session, you will find that the change does not immediately take |
504 | effect. 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 |
507 | AltGr key. |
ee46ef84 |
508 | |
509 | In PuTTY version 0.51, the AltGr key was broken. The bug has been |
510 | fixed since then. |
511 | |
a1d2976b |
512 | \S{faq-idleout}{Question} My PuTTY sessions unexpectedly close after |
70706890 |
513 | they are idle for a while. |
ee46ef84 |
514 | |
515 | Some types of firewall, and almost any router doing Network Address |
516 | Translation (NAT, also known as IP masquerading), will forget about |
517 | a connection through them if the connection does nothing for too |
518 | long. This will cause the connection to be rudely cut off when |
519 | contact is resumed. |
520 | |
521 | You can try to combat this by telling PuTTY to send \e{keepalives}: |
522 | packets of data which have no effect on the actual session, but |
523 | which reassure the router or firewall that the network connection is |
524 | still active and worth remembering about. |
525 | |
526 | Keepalives don't solve everything, unfortunately; although they |
527 | cause greater robustness against this sort of router, they can also |
528 | cause a \e{loss} of robustness against network dropouts. See |
529 | \k{config-keepalive} in the documentation for more discussion of |
530 | this. |
531 | |
a1d2976b |
532 | \S{faq-timeout}{Question} PuTTY's network connections time out too |
70706890 |
533 | quickly when network connectivity is temporarily lost. |
ee46ef84 |
534 | |
535 | This is a Windows problem, not a PuTTY problem. The timeout value |
536 | can't be set on per application or per session basis. To increase |
537 | the TCP timeout globally, you need to tinker with the Registry. |
538 | |
539 | On 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 | |
546 | On Windows NT or 2000, the registry key is |
547 | |
548 | \c HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\ |
549 | \c Parameters\TcpMaxDataRetransmissions |
550 | |
551 | and it must be of type DWORD. |
552 | |
553 | Set the key's value to something like 10. This will cause Windows to |
554 | try 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 |
559 | Don't do that, then. |
ee46ef84 |
560 | |
561 | This is designed behaviour; when PuTTY receives the character |
562 | Control-E from the remote server, it interprets it as a request to |
563 | identify itself, and so it sends back the string \q{\cw{PuTTY}} as |
564 | if that string had been entered at the keyboard. Control-E should |
565 | only be sent by programs that are prepared to deal with the |
566 | response. Writing a binary file to your terminal is likely to output |
567 | many Control-E characters, and cause this behaviour. Don't do it. |
568 | It's a bad plan. |
569 | |
a5a6cb30 |
570 | To mitigate the effects, you could configure the answerback string |
571 | to be empty (see \k{config-answerback}); but writing binary files to |
572 | your terminal is likely to cause various other unpleasant behaviour, |
573 | so this is only a small remedy. |
574 | |
babac7bd |
575 | \S{faq-wintitle}{Question} When I \cw{cat} a binary file, my window |
576 | title changes to a nonsense string. |
ee46ef84 |
577 | |
a5a6cb30 |
578 | Don't do that, then. |
ee46ef84 |
579 | |
580 | It is designed behaviour that PuTTY should have the ability to |
581 | adjust the window title on instructions from the server. Normally |
582 | the control sequence that does this should only be sent |
583 | deliberately, by programs that know what they are doing and intend |
584 | to put meaningful text in the window title. Writing a binary file to |
585 | your terminal runs the risk of sending the same control sequence by |
586 | accident, and cause unexpected changes in the window title. Don't do |
587 | it. |
588 | |
babac7bd |
589 | \S{faq-password-fails}{Question} My keyboard stops working once |
590 | PuTTY displays the password prompt. |
59c1f1f6 |
591 | |
592 | No, it doesn't. PuTTY just doesn't display the password you type, so |
593 | that someone looking at your screen can't see what it is. |
594 | |
595 | Unlike the Windows login prompts, PuTTY doesn't display the password |
596 | as a row of asterisks either. This is so that someone looking at |
597 | your screen can't even tell how \e{long} your password is, which |
598 | might 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 |
603 | use it on a public PC? |
ee46ef84 |
604 | |
605 | It depends on whether you trust that PC. If you don't trust the |
606 | public PC, don't use PuTTY on it, and don't use any other software |
607 | you plan to type passwords into either. It might be watching your |
608 | keystrokes, or it might tamper with the PuTTY binary you download. |
609 | There is \e{no} program safe enough that you can run it on an |
610 | actively malicious PC and get away with typing passwords into it. |
611 | |
612 | If 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 |
614 | be tampered with, so it would be better to carry PuTTY with you on a |
615 | floppy). |
616 | |
a1d2976b |
617 | \S{faq-cleanup}{Question} What does PuTTY leave on a system? How can |
70706890 |
618 | I clean up after it? |
ee46ef84 |
619 | |
620 | PuTTY will leave some Registry entries, and a random seed file, on |
621 | the PC (see \k{faq-settings}). If you are using PuTTY on a public |
622 | PC, or somebody else's PC, you might want to clean these up when you |
623 | leave. 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 |
627 | website used to say how insecure it was? |
ee46ef84 |
628 | |
629 | DSA has a major weakness \e{if badly implemented}: it relies on a |
630 | random number generator to far too great an extent. If the random |
631 | number generator produces a number an attacker can predict, the DSA |
632 | private key is exposed - meaning that the attacker can log in as you |
633 | on all systems that accept that key. |
634 | |
635 | The PuTTY policy changed because the developers were informed of |
636 | ways to implement DSA which do not suffer nearly as badly from this |
637 | weakness, and indeed which don't need to rely on random numbers at |
638 | all. For this reason we now believe PuTTY's DSA implementation is |
639 | probably OK. However, if you have the choice, we still recommend you |
640 | use 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 |
645 | domain name? |
ee46ef84 |
646 | |
647 | No, thank you. Even if you can find one (most of them seem to have |
648 | been registered already, by people who didn't ask whether we |
649 | actually wanted it before they applied), we're happy with the PuTTY |
650 | web 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 |
652 | first link returned), and we don't believe the administrative hassle |
653 | of moving the site would be worth the benefit. |
654 | |
655 | In addition, if we \e{did} want a custom domain name, we would want |
656 | to run it ourselves, so we knew for certain that it would continue |
657 | to point where we wanted it, and wouldn't suddenly change or do |
658 | strange things. Having it registered for us by a third party who we |
659 | don'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 |
662 | PuTTY web site? |
ee46ef84 |
663 | |
664 | We already have some, thanks. |
665 | |
a1d2976b |
666 | \S{faq-sourceforge}{Question} Why don't you move PuTTY to |
70706890 |
667 | SourceForge? |
ee46ef84 |
668 | |
669 | Partly, because we don't want to move the web site location (see |
670 | \k{faq-domain}). |
671 | |
672 | Also, security reasons. PuTTY is a security product, and as such it |
673 | is particularly important to guard the code and the web site against |
674 | unauthorised modifications which might introduce subtle security |
675 | flaws. Therefore, we prefer that the CVS repository, web site and |
676 | FTP site remain where they are, under the direct control of system |
677 | administrators we know and trust personally, rather than being run |
678 | by a large organisation full of people we've never met and which is |
679 | known to have had breakins in the past. |
680 | |
681 | No offence to SourceForge; I think they do a wonderful job. But |
682 | they're not ideal for everyone, and in particular they're not ideal |
683 | for us. |
684 | |
a1d2976b |
685 | \S{faq-mailinglist1}{Question} Why can't I subscribe to the |
70706890 |
686 | putty-bugs mailing list? |
ee46ef84 |
687 | |
688 | Because you're not a member of the PuTTY core development team. The |
689 | putty-bugs mailing list is not a general newsgroup-like discussion |
690 | forum; it's a contact address for the core developers, and an |
691 | \e{internal} mailing list for us to discuss things among ourselves. |
692 | If we opened it up for everybody to subscribe to, it would turn into |
693 | something more like a newsgroup and we would be completely |
694 | overwhelmed by the volume of traffic. It's hard enough to keep up |
695 | with the list as it is. |
696 | |
a1d2976b |
697 | \S{faq-mailinglist2}{Question} If putty-bugs isn't a |
70706890 |
698 | general-subscription mailing list, what is? |
ee46ef84 |
699 | |
700 | There isn't one, that we know of. |
701 | |
702 | If someone else wants to set up a mailing list for PuTTY users to |
703 | help each other with common problems, that would be fine with us; |
704 | but the PuTTY team would almost certainly not have the time to read |
705 | it, so any questions the list couldn't answer would have to be |
706 | forwarded on to us by the questioner. In any case, it's probably |
707 | better to use the established newsgroup \cw{comp.security.ssh} for |
708 | this purpose. |
709 | |
a1d2976b |
710 | \S{faq-donations}{Question} How can I donate to PuTTY development? |
ee46ef84 |
711 | |
712 | Please, \e{please} don't feel you have to. PuTTY is completely free |
713 | software, and not shareware. We think it's very important that |
714 | \e{everybody} who wants to use PuTTY should be able to, whether they |
715 | have any money or not; so the last thing we would want is for a |
716 | PuTTY user to feel guilty because they haven't paid us any money. If |
717 | you want to keep your money, please do keep it. We wouldn't dream of |
718 | asking for any. |
719 | |
720 | Having said all that, if you still really \e{want} to give us money, |
721 | we won't argue :-) The easiest way for us to accept donations is if |
722 | you go to \W{http://www.e-gold.com}\cw{www.e-gold.com}, and deposit |
723 | your donation in account number 174769. Then send us e-mail to let |
724 | us know you've done so (otherwise we might not notice for months!). |
725 | |
726 | Small donations (tens of dollars or tens of euros) will probably be |
727 | spent on beer or curry, which helps motivate our volunteer team to |
728 | continue doing this for the world. Larger donations will be spent on |
729 | something that actually helps development, if we can find anything |
730 | (perhaps new hardware, or a copy of Windows 2000), but if we can't |
731 | find anything then we'll just distribute the money among the |
732 | developers. If you want to be sure your donation is going towards |
733 | something worthwhile, ask us first. If you don't like these terms, |
734 | feel perfectly free not to donate. We don't mind. |
735 | |
a1d2976b |
736 | \S{faq-pronounce}{Question} How do I pronounce PuTTY? |
ee46ef84 |
737 | |
738 | Exactly like the normal word \q{putty}. Just like the stuff you put |
739 | on window frames. (One of the reasons it's called PuTTY is because |
740 | it makes Windows usable. :-) |