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1 | \versionid $Id: faq.but,v 1.18 2002/01/14 12:16:58 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 | |
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34 | Public key authentication (both RSA and DSA) in SSH v2 is new in |
35 | version 0.52. |
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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 | |
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51 | Yes. Version 0.52 has proper support for local echo. |
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52 | |
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53 | In version 0.51 and before, local echo could not be separated from |
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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 |
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57 | it). New in version 0.52, local echo and local line editing are |
58 | separate options, and by default PuTTY will try to determine |
59 | automatically whether to enable them or not, based on which protocol |
60 | you have selected and also based on hints from the server. If you |
61 | have a problem with PuTTY's default choice, you can force each |
62 | option to be enabled or disabled as you choose. The controls are in |
63 | the Terminal panel, in the section marked \q{Line discipline |
64 | options}. |
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65 | |
a1d2976b |
66 | \S{faq-disksettings}{Question} Does PuTTY support storing its |
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67 | settings in a disk file? |
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68 | |
69 | Not at present, although \k{config-file} in the documentation gives |
70 | a method of achieving the same effect. |
71 | |
a1d2976b |
72 | \S{faq-fullscreen}{Question} Does PuTTY support full-screen mode, |
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73 | like a DOS box? |
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74 | |
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75 | Yes; this is a new feature in version 0.52. |
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76 | |
babac7bd |
77 | \S{faq-password-remember}{Question} Does PuTTY have the ability to |
78 | remember my password so I don't have to type it every time? |
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79 | |
80 | No, it doesn't. |
81 | |
82 | Remembering your password is a bad plan for obvious security |
83 | reasons: anyone who gains access to your machine while you're away |
84 | from your desk can find out the remembered password, and use it, |
85 | abuse it or change it. |
86 | |
87 | In addition, it's not even \e{possible} for PuTTY to automatically |
88 | send your password in a Telnet session, because Telnet doesn't give |
89 | the client software any indication of which part of the login |
90 | process is the password prompt. PuTTY would have to guess, by |
91 | looking for words like \q{password} in the session data; and if your |
92 | login program is written in something other than English, this won't |
93 | work. |
94 | |
95 | In SSH, remembering your password would be possible in theory, but |
96 | there doesn't seem to be much point since SSH supports public key |
97 | authentication, which is more flexible and more secure. See |
98 | \k{pubkey} in the documentation for a full discussion of public key |
99 | authentication. |
100 | |
a1d2976b |
101 | \S{faq-hostkeys}{Question} Is there an option to turn off the |
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102 | annoying host key prompts? |
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103 | |
104 | No, there isn't. And there won't be. Even if you write it yourself |
105 | and send us the patch, we won't accept it. |
106 | |
107 | Those annoying host key prompts are the \e{whole point} of SSH. |
108 | Without them, all the cryptographic technology SSH uses to secure |
109 | your session is doing nothing more than making an attacker's job |
110 | slightly harder; instead of sitting between you and the server with |
111 | a packet sniffer, the attacker must actually subvert a router and |
112 | start modifying the packets going back and forth. But that's not all |
113 | that much harder than just sniffing; and without host key checking, |
114 | it will go completely undetected by client or server. |
115 | |
116 | Host key checking is your guarantee that the encryption you put on |
117 | your data at the client end is the \e{same} encryption taken off the |
118 | data at the server end; it's your guarantee that it hasn't been |
119 | removed and replaced somewhere on the way. Host key checking makes |
120 | the attacker's job \e{astronomically} hard, compared to packet |
121 | sniffing, and even compared to subverting a router. Instead of |
122 | applying a little intelligence and keeping an eye on Bugtraq, the |
123 | attacker must now perform a brute-force attack against at least one |
124 | military-strength cipher. That insignificant host key prompt really |
125 | does make \e{that} much difference. |
126 | |
127 | If you're having a specific problem with host key checking - perhaps |
128 | you want an automated batch job to make use of PSCP or Plink, and |
129 | the interactive host key prompt is hanging the batch process - then |
130 | the right way to fix it is to add the correct host key to the |
131 | Registry in advance. That way, you retain the \e{important} feature |
132 | of host key checking: the right key will be accepted and the wrong |
133 | ones will not. Adding an option to turn host key checking off |
134 | completely is the wrong solution and we will not do it. |
135 | |
a1d2976b |
136 | \S{faq-server}{Question} Will you write an SSH server for the PuTTY |
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137 | suite, to go with the client? |
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138 | |
139 | No. The only reason we might want to would be if we could easily |
140 | re-use existing code and significantly cut down the effort. We don't |
141 | believe this is the case; there just isn't enough common ground |
142 | between an SSH client and server to make it worthwhile. |
143 | |
144 | If someone else wants to use bits of PuTTY in the process of writing |
145 | a Windows SSH server, they'd be perfectly welcome to of course, but |
146 | I really can't see it being a lot less effort for us to do that than |
147 | it would be for us to write a server from the ground up. We don't |
148 | have time, and we don't have motivation. The code is available if |
149 | anyone else wants to try it. |
150 | |
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151 | \H{faq-ports} Ports to other operating systems |
152 | |
153 | The eventual goal is for PuTTY to be a multi-platform program, able |
154 | to run on at least Windows, MacOS and Unix. Whether this will |
155 | actually ever happen I have no idea, but it is the plan. A Mac port |
156 | has been started, but is only half-finished and currently not moving |
157 | very fast. |
158 | |
159 | Porting will become easier once PuTTY has a generalised porting |
160 | layer, drawing a clear line between platform-dependent and |
161 | platform-independent code. The general intention is for this porting |
162 | layer to evolve naturally as part of the process of doing the first |
163 | port. One particularly nasty part of this will be separating the |
164 | many configuration options into platform-dependent and |
165 | platform-independent ones; for example, the options controlling when |
166 | the Windows System menu appears will be pretty much meaningless |
167 | under X11 or perhaps other windowing systems, whereas Telnet Passive |
168 | Mode is universal and shouldn't need to be specified once for each |
169 | platform. |
170 | |
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171 | \S{faq-wince}{Question} Will there be a port to Windows CE? |
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172 | |
173 | Probably not in the particularly near future. Despite sharing large |
174 | parts of the Windows API, in practice WinCE doesn't appear to be |
175 | significantly easier to port to than a totally different operating |
176 | system. |
177 | |
178 | However, PuTTY on portable devices would clearly be a useful thing, |
179 | so in the long term I hope there will be a WinCE port. |
180 | |
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181 | \S{faq-win31}{Question} Is there a port to Windows 3.1? |
182 | |
183 | PuTTY is a 32-bit application from the ground up, so it won't run on |
184 | Windows 3.1 as a native 16-bit program; and it would be \e{very} |
185 | hard to port it to do so, because of Windows 3.1's vile memory |
186 | allocation mechanisms. |
187 | |
188 | However, it is possible in theory to compile the existing PuTTY |
189 | source in such a way that it will run under Win32s (an extension to |
190 | Windows 3.1 to let you run 32-bit programs). In order to do this |
191 | you'll need the right kind of C compiler - modern versions of Visual |
192 | C at least have stopped being backwards compatible to Win32s. Also, |
193 | the last time we tried this it didn't work very well. |
194 | |
195 | If you're interested in running PuTTY under Windows 3.1, help and |
196 | testing in this area would be very welcome! |
197 | |
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198 | \S{faq-mac-port}{Question} Will there be a port to the Mac? |
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199 | |
200 | A Mac port was started once and is half-finished, but development |
201 | has been static for some time and the main PuTTY code has moved on, |
202 | so it's not clear how quickly development would resume even if |
203 | developer effort were available. |
204 | |
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205 | \S{faq-unix}{Question} Will there be a port to Unix? |
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206 | |
207 | I hope so, if only so that I can have an \cw{xterm}-like program |
208 | that supports exactly the same terminal emulation as PuTTY. If and |
209 | when we do do a Unix port, it will have a local-terminal back end so |
210 | it can be used like an \cw{xterm}, rather than only being usable as |
211 | a network utility. |
212 | |
a1d2976b |
213 | \S{faq-epoc}{Question} Will there be a port to EPOC? |
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214 | |
215 | I hope so, but given that ports aren't really progressing very fast |
216 | even on systems the developers \e{do} already know how to program |
217 | for, it might be a long time before any of us get round to learning |
218 | a new system and doing the port for that. |
219 | |
220 | \H{faq-embedding} Embedding PuTTY in other programs |
221 | |
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222 | \S{faq-dll}{Question} Is the SSH or Telnet code available as a DLL? |
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223 | |
224 | No, it isn't. It would take a reasonable amount of rewriting for |
225 | this to be possible, and since the PuTTY project itself doesn't |
226 | believe in DLLs (they make installation more error-prone) none of us |
227 | has taken the time to do it. |
228 | |
229 | Most of the code cleanup work would be a good thing to happen in |
230 | general, so if anyone feels like helping, we wouldn't say no. |
231 | |
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232 | \S{faq-vb}{Question} Is the SSH or Telnet code available as a Visual |
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233 | Basic component? |
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234 | |
235 | No, it isn't. None of the PuTTY team uses Visual Basic, and none of |
236 | us has any particular need to make SSH connections from a Visual |
237 | Basic application. In addition, all the preliminary work to turn it |
238 | into a DLL would be necessary first; and furthermore, we don't even |
239 | know how to write VB components. |
240 | |
241 | If someone offers to do some of this work for us, we might consider |
242 | it, but unless that happens I can't see VB integration being |
243 | anywhere other than the very bottom of our priority list. |
244 | |
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245 | \S{faq-ipc}{Question} How can I use PuTTY to make an SSH connection |
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246 | from within another program? |
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247 | |
248 | Probably your best bet is to use Plink, the command-line connection |
249 | tool. If you can start Plink as a second Windows process, and |
250 | arrange for your primary process to be able to send data to the |
251 | Plink process, and receive data from it, through pipes, then you |
252 | should be able to make SSH connections from your program. |
253 | |
254 | This is what CVS for Windows does, for example. |
255 | |
256 | \H{faq-details} Details of PuTTY's operation |
257 | |
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258 | \S{faq-term}{Question} What terminal type does PuTTY use? |
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259 | |
260 | For most purposes, PuTTY can be considered to be an \cw{xterm} |
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261 | terminal. |
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262 | |
263 | PuTTY also supports some terminal control sequences not supported by |
264 | the real \cw{xterm}: notably the Linux console sequences that |
265 | reconfigure the colour palette, and the title bar control sequences |
266 | used by \cw{DECterm} (which are different from the \cw{xterm} ones; |
267 | PuTTY supports both). |
268 | |
269 | By default, PuTTY announces its terminal type to the server as |
270 | \c{xterm}. If you have a problem with this, you can reconfigure it |
271 | to say something else; \c{vt220} might help if you have trouble. |
272 | |
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273 | \S{faq-settings}{Question} Where does PuTTY store its data? |
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274 | |
275 | PuTTY stores most of its data (saved sessions, SSH host keys) in the |
276 | Registry. The precise location is |
277 | |
278 | \c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY |
279 | |
280 | and within that area, saved sessions are stored under \c{Sessions} |
281 | while host keys are stored under \c{SshHostKeys}. |
282 | |
283 | PuTTY also requires a random number seed file, to improve the |
284 | unpredictability of randomly chosen data needed as part of the SSH |
285 | cryptography. This is stored by default in your Windows home |
286 | directory (\c{%HOMEDRIVE%\\%HOMEPATH%}), or in the actual Windows |
287 | directory (such as \c{C:\\WINDOWS}) if the home directory doesn't |
288 | exist, for example if you're using Win95. If you want to change the |
289 | location of the random number seed file, you can put your chosen |
290 | pathname in the Registry, at |
291 | |
292 | \c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\RandSeedFile |
293 | |
294 | \H{faq-howto} HOWTO questions |
295 | |
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296 | \S{faq-startmax}{Question} How can I make PuTTY start up maximised? |
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297 | |
298 | Create a Windows shortcut to start PuTTY from, and set it as \q{Run |
299 | Maximized}. |
300 | |
a1d2976b |
301 | \S{faq-startsess}{Question} How can I create a Windows shortcut to |
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302 | start a particular saved session directly? |
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303 | |
304 | To run a PuTTY session saved under the name \q{\cw{mysession}}, |
305 | create a Windows shortcut that invokes PuTTY with a command line |
306 | like |
307 | |
308 | \c \path\name\to\putty.exe @mysession |
309 | |
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310 | \S{faq-startssh}{Question} How can I start an SSH session straight |
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311 | from the command line? |
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312 | |
313 | Use the command line \c{putty -ssh host.name}. Alternatively, create |
314 | a saved session that specifies the SSH protocol, and start the saved |
315 | session as shown in \k{faq-startsess}. |
316 | |
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317 | \S{faq-cutpaste}{Question} How do I copy and paste between PuTTY and |
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318 | other Windows applications? |
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319 | |
320 | Copy and paste works similarly to the X Window System. You use the |
321 | left mouse button to select text in the PuTTY window. The act of |
322 | selection \e{automatically} copies the text to the clipboard: there |
323 | is no need to press Ctrl-Ins or Ctrl-C or anything else. In fact, |
324 | pressing Ctrl-C will send a Ctrl-C character to the other end of |
325 | your connection (just like it does the rest of the time), which may |
326 | have unpleasant effects. The \e{only} thing you need to do, to copy |
327 | text to the clipboard, is to select it. |
328 | |
329 | To paste the clipboard contents into a PuTTY window, by default you |
330 | click the right mouse button. If you have a three-button mouse and |
331 | are used to X applications, you can configure pasting to be done by |
332 | the middle button instead, but this is not the default because most |
333 | Windows users don't have a middle button at all. |
334 | |
335 | You can also paste by pressing Shift-Ins. |
336 | |
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337 | \S{faq-tunnels}{Question} How do I use X forwarding and port |
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338 | forwarding? I can't find the Tunnels panel. |
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339 | |
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340 | This is a new feature in version 0.52. You should upgrade. |
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341 | |
a1d2976b |
342 | \S{faq-options}{Question} How do I use all PuTTY's features (public |
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343 | keys, port forwarding, SSH v2, etc.) in PSCP, PSFTP and Plink? |
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344 | |
345 | The command-line tools are currently rather short of command line |
346 | options to enable this sort of thing. However, you can use most of |
347 | PuTTY's features if you create a PuTTY saved session, and then use |
348 | the name of the saved session on the command line in place of a |
349 | hostname. This works for PSCP, PSFTP and Plink (but don't expect |
350 | port forwarding in the file transfer applications!). |
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351 | |
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352 | \S{faq-pscp}{Question} How do I use PSCP.EXE? When I double-click it |
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353 | gives me a command prompt window which then closes instantly. |
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354 | |
355 | PSCP is a command-line application, not a GUI application. If you |
356 | run it without arguments, it will simply print a help message and |
357 | terminate. |
358 | |
359 | To use PSCP properly, run it from a Command Prompt window. See |
360 | \k{pscp} in the documentation for more details. |
361 | |
a1d2976b |
362 | \S{faq-pscp-spaces}{Question} How do I use PSCP to copy a file whose |
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363 | name has spaces in? |
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364 | |
365 | If PSCP is using the traditional SCP protocol, this is confusing. If |
366 | you're specifying a file at the local end, you just use one set of |
367 | quotes as you would normally do: |
368 | |
369 | \c pscp "local filename with spaces" user@host: |
370 | \c pscp user@host:myfile "local filename with spaces" |
371 | |
372 | But if the filename you're specifying is on the \e{remote} side, you |
373 | have to use backslashes and two sets of quotes: |
374 | |
375 | \c pscp user@host:"\"remote filename with spaces\"" local_filename |
376 | \c pscp local_filename user@host:"\"remote filename with spaces\"" |
377 | |
378 | Worse still, in a remote-to-local copy you have to specify the local |
379 | file name explicitly, otherwise PSCP will complain that they don't |
380 | match (unless you specified the \c{-unsafe} option). The following |
381 | command will give an error message: |
382 | |
383 | \c c:\>pscp user@host:"\"oo er\"" . |
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384 | \c warning: remote host tried to write to a file called 'oo er' |
385 | \c when we requested a file called '"oo er"'. |
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386 | |
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387 | Instead, you need to specify the local file name in full: |
388 | |
389 | \c c:\>pscp user@host:"\"oo er\"" "oo er" |
390 | |
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391 | If PSCP is using the newer SFTP protocol, none of this is a problem, |
392 | and all filenames with spaces in are specified using a single pair |
393 | of quotes in the obvious way: |
394 | |
395 | \c pscp "local file" user@host: |
396 | \c pscp user@host:"remote file" . |
397 | |
398 | \H{faq-trouble} Troubleshooting |
399 | |
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400 | \S{faq-incorrect-mac}{Question} Why do I see \q{Incorrect MAC |
401 | received on packet}? |
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402 | |
403 | This is due to a bug in old SSH 2 servers distributed by |
404 | \cw{ssh.com}. Version 2.3.0 and below of their SSH 2 server |
405 | constructs Message Authentication Codes in the wrong way, and |
406 | expects the client to construct them in the same wrong way. PuTTY |
407 | constructs the MACs correctly by default, and hence these old |
408 | servers will fail to work with it. |
409 | |
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410 | If you are using PuTTY version 0.52 or better, this should work |
411 | automatically: PuTTY should detect the buggy servers from their |
412 | version number announcement, and automatically start to construct |
413 | its MACs in the same incorrect manner as they do, so it will be able |
414 | to work with them. |
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415 | |
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416 | If you are using PuTTY version 0.51 or below, you can enable the |
417 | workaround by going to the SSH panel and ticking the box labelled |
418 | \q{Imitate SSH 2 MAC bug}. It's possible that you might have to do |
419 | this with 0.52 as well, if a buggy server exists that PuTTY doesn't |
420 | know about. |
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421 | |
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422 | In this context MAC stands for Message Authentication Code. It's a |
423 | cryptographic term, and it has nothing at all to do with Ethernet |
424 | MAC (Media Access Control) addresses. |
425 | |
a1d2976b |
426 | \S{faq-colours}{Question} I clicked on a colour in the Colours |
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427 | panel, and the colour didn't change in my terminal. |
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428 | |
429 | That isn't how you're supposed to use the Colours panel. |
430 | |
431 | During the course of a session, PuTTY potentially uses \e{all} the |
432 | colours listed in the Colours panel. It's not a question of using |
433 | only one of them and you choosing which one; PuTTY will use them |
434 | \e{all}. The purpose of the Colours panel is to let you adjust the |
435 | appearance of all the colours. So to change the colour of the |
436 | cursor, for example, you would select \q{Cursor Colour}, press the |
437 | \q{Modify} button, and select a new colour from the dialog box that |
438 | appeared. Similarly, if you want your session to appear in green, |
439 | you should select \q{Default Foreground} and press \q{Modify}. |
440 | Clicking on \q{ANSI Green} won't turn your session green; it will |
441 | only allow you to adjust the \e{shade} of green used when PuTTY is |
442 | instructed by the server to display green text. |
443 | |
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444 | \S{faq-winsock2}{Question} Plink on Windows 95 says it can't find |
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445 | \cw{WS2_32.DLL}. |
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446 | |
447 | Plink requires the extended Windows network library, WinSock version |
448 | 2. This is installed as standard on Windows 98 and above, and on |
449 | Windows NT, and even on later versions of Windows 95; but early |
450 | Win95 installations don't have it. |
451 | |
452 | In order to use Plink on these systems, you will need to download |
453 | the |
454 | \W{http://www.microsoft.com/windows95/downloads/contents/wuadmintools/s_wunetworkingtools/w95sockets2/}{WinSock 2 upgrade}: |
455 | |
456 | \c http://www.microsoft.com/windows95/downloads/contents/wuadmintools/ |
457 | \c s_wunetworkingtools/w95sockets2/ |
458 | |
a1d2976b |
459 | \S{faq-rekey}{Question} My PuTTY sessions close after an hour and |
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460 | tell me \q{Server failed host key check}. |
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461 | |
462 | This is a bug in all versions of PuTTY up to and including 0.51. SSH |
463 | v2 servers from \cw{ssh.com} will require the key exchange to be |
464 | repeated one hour after the start of the connection, and PuTTY will |
465 | get this wrong. |
466 | |
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467 | Upgrade to version 0.52 and the problem should go away. |
ee46ef84 |
468 | |
a1d2976b |
469 | \S{faq-outofmem}{Question} After trying to establish an SSH 2 |
70706890 |
470 | connection, PuTTY says \q{Out of memory} and dies. |
ee46ef84 |
471 | |
472 | If this happens just while the connection is starting up, this often |
473 | indicates that for some reason the client and server have failed to |
474 | establish a session encryption key. Somehow, they have performed |
475 | calculations that should have given each of them the same key, but |
476 | have ended up with different keys; so data encrypted by one and |
477 | decrypted by the other looks like random garbage. |
478 | |
479 | This causes an \q{out of memory} error because the first encrypted |
480 | data PuTTY expects to see is the length of an SSH message. Normally |
481 | this will be something well under 100 bytes. If the decryption has |
482 | failed, PuTTY will see a completely random length in the region of |
483 | two \e{gigabytes}, and will try to allocate enough memory to store |
484 | this non-existent message. This will immediately lead to it thinking |
485 | it doesn't have enough memory, and panicking. |
486 | |
487 | If this happens to you, it is quite likely to still be a PuTTY bug |
488 | and you should report it (although it might be a bug in your SSH |
489 | server instead); but it doesn't necessarily mean you've actually run |
490 | out of memory. |
491 | |
a1d2976b |
492 | \S{faq-bce}{Question} When I run full-colour applications, I see |
70706890 |
493 | areas of black space where colour ought to be. |
f1453e5c |
494 | |
495 | You almost certainly need to enable the \q{Use background colour to |
496 | erase screen} setting in the Terminal panel. Note that if you do |
497 | this in mid-session, it won't take effect until you reset the |
498 | terminal (see \k{faq-resetterm}). |
499 | |
a1d2976b |
500 | \S{faq-resetterm}{Question} When I change some terminal settings, |
70706890 |
501 | nothing happens. |
f1453e5c |
502 | |
503 | Some of the terminal options (notably Auto Wrap and |
504 | background-colour screen erase) actually represent the \e{default} |
505 | setting, rather than the currently active setting. The server can |
506 | send sequences that modify these options in mid-session, but when |
507 | the terminal is reset (by server action, or by you choosing \q{Reset |
508 | Terminal} from the System menu) the defaults are restored. |
509 | |
510 | If you want to change one of these options in the middle of a |
511 | session, you will find that the change does not immediately take |
512 | effect. It will only take effect once you reset the terminal. |
513 | |
a1d2976b |
514 | \S{faq-altgr}{Question} I can't type characters that require the |
70706890 |
515 | AltGr key. |
ee46ef84 |
516 | |
32c37ecd |
517 | In PuTTY version 0.51, the AltGr key was broken. Upgrade to version |
518 | 0.52. |
ee46ef84 |
519 | |
a1d2976b |
520 | \S{faq-idleout}{Question} My PuTTY sessions unexpectedly close after |
70706890 |
521 | they are idle for a while. |
ee46ef84 |
522 | |
523 | Some types of firewall, and almost any router doing Network Address |
524 | Translation (NAT, also known as IP masquerading), will forget about |
525 | a connection through them if the connection does nothing for too |
526 | long. This will cause the connection to be rudely cut off when |
527 | contact is resumed. |
528 | |
529 | You can try to combat this by telling PuTTY to send \e{keepalives}: |
530 | packets of data which have no effect on the actual session, but |
531 | which reassure the router or firewall that the network connection is |
532 | still active and worth remembering about. |
533 | |
534 | Keepalives don't solve everything, unfortunately; although they |
535 | cause greater robustness against this sort of router, they can also |
536 | cause a \e{loss} of robustness against network dropouts. See |
537 | \k{config-keepalive} in the documentation for more discussion of |
538 | this. |
539 | |
a1d2976b |
540 | \S{faq-timeout}{Question} PuTTY's network connections time out too |
70706890 |
541 | quickly when network connectivity is temporarily lost. |
ee46ef84 |
542 | |
543 | This is a Windows problem, not a PuTTY problem. The timeout value |
544 | can't be set on per application or per session basis. To increase |
545 | the TCP timeout globally, you need to tinker with the Registry. |
546 | |
547 | On Windows 95, 98 or ME, the registry key you need to change is |
548 | |
549 | \c HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\ |
550 | \c MSTCP\MaxDataRetries |
551 | |
552 | (it must be of type DWORD in Win95, or String in Win98/ME). |
553 | |
554 | On Windows NT or 2000, the registry key is |
555 | |
556 | \c HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\ |
557 | \c Parameters\TcpMaxDataRetransmissions |
558 | |
559 | and it must be of type DWORD. |
560 | |
561 | Set the key's value to something like 10. This will cause Windows to |
562 | try harder to keep connections alive instead of abandoning them. |
563 | |
a1d2976b |
564 | \S{faq-puttyputty}{Question} When I \cw{cat} a binary file, I get |
ee46ef84 |
565 | `PuTTYPuTTYPuTTY' on my command line. |
566 | |
a5a6cb30 |
567 | Don't do that, then. |
ee46ef84 |
568 | |
569 | This is designed behaviour; when PuTTY receives the character |
570 | Control-E from the remote server, it interprets it as a request to |
571 | identify itself, and so it sends back the string \q{\cw{PuTTY}} as |
572 | if that string had been entered at the keyboard. Control-E should |
573 | only be sent by programs that are prepared to deal with the |
574 | response. Writing a binary file to your terminal is likely to output |
575 | many Control-E characters, and cause this behaviour. Don't do it. |
576 | It's a bad plan. |
577 | |
a5a6cb30 |
578 | To mitigate the effects, you could configure the answerback string |
579 | to be empty (see \k{config-answerback}); but writing binary files to |
580 | your terminal is likely to cause various other unpleasant behaviour, |
581 | so this is only a small remedy. |
582 | |
babac7bd |
583 | \S{faq-wintitle}{Question} When I \cw{cat} a binary file, my window |
584 | title changes to a nonsense string. |
ee46ef84 |
585 | |
a5a6cb30 |
586 | Don't do that, then. |
ee46ef84 |
587 | |
588 | It is designed behaviour that PuTTY should have the ability to |
589 | adjust the window title on instructions from the server. Normally |
590 | the control sequence that does this should only be sent |
591 | deliberately, by programs that know what they are doing and intend |
592 | to put meaningful text in the window title. Writing a binary file to |
593 | your terminal runs the risk of sending the same control sequence by |
594 | accident, and cause unexpected changes in the window title. Don't do |
595 | it. |
596 | |
babac7bd |
597 | \S{faq-password-fails}{Question} My keyboard stops working once |
598 | PuTTY displays the password prompt. |
59c1f1f6 |
599 | |
600 | No, it doesn't. PuTTY just doesn't display the password you type, so |
601 | that someone looking at your screen can't see what it is. |
602 | |
603 | Unlike the Windows login prompts, PuTTY doesn't display the password |
604 | as a row of asterisks either. This is so that someone looking at |
605 | your screen can't even tell how \e{long} your password is, which |
606 | might be valuable information. |
607 | |
b5bee048 |
608 | \S{faq-keyboard}{Question} One or more function keys don't do what I |
609 | expected in a server-side application. |
610 | |
611 | If you've already tried all the relevant options in the PuTTY |
612 | Keyboard panel, you may need to mail the PuTTY maintainers and ask. |
613 | |
614 | It is \e{not} usually helpful just to tell us which application, |
615 | which server operating system, and which key isn't working; in order |
616 | to replicate the problem we would need to have a copy of every |
617 | operating system, and every application, that anyone has ever |
618 | complained about. |
619 | |
620 | PuTTY responds to function key presses by sending a sequence of |
621 | control characters to the server. If a function key isn't doing what |
622 | you expect, it's likely that the character sequence your application |
623 | is expecting to receive is not the same as the one PuTTY is sending. |
624 | Therefore what we really need to know is \e{what} sequence the |
625 | application is expecting. |
626 | |
627 | The simplest way to investigate this is to find some other terminal |
628 | environment, in which that function key \e{does} work; and then |
629 | investigate what sequence the function key is sending in that |
630 | situation. One reasonably easy way to do this on a Unix system is to |
631 | type the command \c{cat}, and then press the function key. This is |
632 | likely to produce output of the form \c{^[[11~}. You can also do |
633 | this in PuTTY, to find out what sequence the function key is |
634 | producing in that. Then you can mail the PuTTY maintainers and tell |
635 | us \q{I wanted the F1 key to send \c{^[[11~}, but instead it's |
636 | sending \c{^[OP}, can this be done?}, or something similar. |
637 | |
638 | You should still read the |
639 | \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/feedback.html}{Feedback |
640 | page} on the PuTTY website (also provided as \k{feedback} in the |
641 | manual), and follow the guidelines contained in that. |
642 | |
ee46ef84 |
643 | \H{faq-secure} Security questions |
644 | |
a1d2976b |
645 | \S{faq-publicpc}{Question} Is it safe for me to download PuTTY and |
70706890 |
646 | use it on a public PC? |
ee46ef84 |
647 | |
648 | It depends on whether you trust that PC. If you don't trust the |
649 | public PC, don't use PuTTY on it, and don't use any other software |
650 | you plan to type passwords into either. It might be watching your |
651 | keystrokes, or it might tamper with the PuTTY binary you download. |
652 | There is \e{no} program safe enough that you can run it on an |
653 | actively malicious PC and get away with typing passwords into it. |
654 | |
655 | If you do trust the PC, then it's probably OK to use PuTTY on it |
656 | (but if you don't trust the network, then the PuTTY download might |
657 | be tampered with, so it would be better to carry PuTTY with you on a |
658 | floppy). |
659 | |
a1d2976b |
660 | \S{faq-cleanup}{Question} What does PuTTY leave on a system? How can |
70706890 |
661 | I clean up after it? |
ee46ef84 |
662 | |
663 | PuTTY will leave some Registry entries, and a random seed file, on |
664 | the PC (see \k{faq-settings}). If you are using PuTTY on a public |
665 | PC, or somebody else's PC, you might want to clean these up when you |
666 | leave. You can do that automatically, by running the command |
667 | \c{putty -cleanup}. |
668 | |
a1d2976b |
669 | \S{faq-dsa}{Question} How come PuTTY now supports DSA, when the |
70706890 |
670 | website used to say how insecure it was? |
ee46ef84 |
671 | |
672 | DSA has a major weakness \e{if badly implemented}: it relies on a |
673 | random number generator to far too great an extent. If the random |
674 | number generator produces a number an attacker can predict, the DSA |
675 | private key is exposed - meaning that the attacker can log in as you |
676 | on all systems that accept that key. |
677 | |
678 | The PuTTY policy changed because the developers were informed of |
679 | ways to implement DSA which do not suffer nearly as badly from this |
680 | weakness, and indeed which don't need to rely on random numbers at |
681 | all. For this reason we now believe PuTTY's DSA implementation is |
682 | probably OK. However, if you have the choice, we still recommend you |
683 | use RSA instead. |
684 | |
685 | \H{faq-admin} Administrative questions |
686 | |
a1d2976b |
687 | \S{faq-domain}{Question} Would you like me to register you a nicer |
70706890 |
688 | domain name? |
ee46ef84 |
689 | |
690 | No, thank you. Even if you can find one (most of them seem to have |
691 | been registered already, by people who didn't ask whether we |
692 | actually wanted it before they applied), we're happy with the PuTTY |
693 | web site being exactly where it is. It's not hard to find (just type |
694 | \q{putty} into \W{http://www.google.com/}{google.com} and we're the |
695 | first link returned), and we don't believe the administrative hassle |
696 | of moving the site would be worth the benefit. |
697 | |
698 | In addition, if we \e{did} want a custom domain name, we would want |
699 | to run it ourselves, so we knew for certain that it would continue |
700 | to point where we wanted it, and wouldn't suddenly change or do |
701 | strange things. Having it registered for us by a third party who we |
702 | don't even know is not the best way to achieve this. |
703 | |
a1d2976b |
704 | \S{faq-webhosting}{Question} Would you like free web hosting for the |
70706890 |
705 | PuTTY web site? |
ee46ef84 |
706 | |
707 | We already have some, thanks. |
708 | |
a1d2976b |
709 | \S{faq-sourceforge}{Question} Why don't you move PuTTY to |
70706890 |
710 | SourceForge? |
ee46ef84 |
711 | |
712 | Partly, because we don't want to move the web site location (see |
713 | \k{faq-domain}). |
714 | |
715 | Also, security reasons. PuTTY is a security product, and as such it |
716 | is particularly important to guard the code and the web site against |
717 | unauthorised modifications which might introduce subtle security |
718 | flaws. Therefore, we prefer that the CVS repository, web site and |
719 | FTP site remain where they are, under the direct control of system |
720 | administrators we know and trust personally, rather than being run |
721 | by a large organisation full of people we've never met and which is |
722 | known to have had breakins in the past. |
723 | |
724 | No offence to SourceForge; I think they do a wonderful job. But |
725 | they're not ideal for everyone, and in particular they're not ideal |
726 | for us. |
727 | |
a1d2976b |
728 | \S{faq-mailinglist1}{Question} Why can't I subscribe to the |
70706890 |
729 | putty-bugs mailing list? |
ee46ef84 |
730 | |
731 | Because you're not a member of the PuTTY core development team. The |
732 | putty-bugs mailing list is not a general newsgroup-like discussion |
733 | forum; it's a contact address for the core developers, and an |
734 | \e{internal} mailing list for us to discuss things among ourselves. |
735 | If we opened it up for everybody to subscribe to, it would turn into |
736 | something more like a newsgroup and we would be completely |
737 | overwhelmed by the volume of traffic. It's hard enough to keep up |
738 | with the list as it is. |
739 | |
a1d2976b |
740 | \S{faq-mailinglist2}{Question} If putty-bugs isn't a |
70706890 |
741 | general-subscription mailing list, what is? |
ee46ef84 |
742 | |
743 | There isn't one, that we know of. |
744 | |
745 | If someone else wants to set up a mailing list for PuTTY users to |
746 | help each other with common problems, that would be fine with us; |
747 | but the PuTTY team would almost certainly not have the time to read |
748 | it, so any questions the list couldn't answer would have to be |
749 | forwarded on to us by the questioner. In any case, it's probably |
750 | better to use the established newsgroup \cw{comp.security.ssh} for |
751 | this purpose. |
752 | |
a1d2976b |
753 | \S{faq-donations}{Question} How can I donate to PuTTY development? |
ee46ef84 |
754 | |
755 | Please, \e{please} don't feel you have to. PuTTY is completely free |
756 | software, and not shareware. We think it's very important that |
757 | \e{everybody} who wants to use PuTTY should be able to, whether they |
758 | have any money or not; so the last thing we would want is for a |
759 | PuTTY user to feel guilty because they haven't paid us any money. If |
760 | you want to keep your money, please do keep it. We wouldn't dream of |
761 | asking for any. |
762 | |
763 | Having said all that, if you still really \e{want} to give us money, |
764 | we won't argue :-) The easiest way for us to accept donations is if |
765 | you go to \W{http://www.e-gold.com}\cw{www.e-gold.com}, and deposit |
766 | your donation in account number 174769. Then send us e-mail to let |
767 | us know you've done so (otherwise we might not notice for months!). |
768 | |
769 | Small donations (tens of dollars or tens of euros) will probably be |
770 | spent on beer or curry, which helps motivate our volunteer team to |
771 | continue doing this for the world. Larger donations will be spent on |
772 | something that actually helps development, if we can find anything |
773 | (perhaps new hardware, or a copy of Windows 2000), but if we can't |
774 | find anything then we'll just distribute the money among the |
775 | developers. If you want to be sure your donation is going towards |
776 | something worthwhile, ask us first. If you don't like these terms, |
777 | feel perfectly free not to donate. We don't mind. |
778 | |
606398fb |
779 | \S{faq-sillyputty}{Question} Where can I buy silly putty? |
780 | |
781 | You're looking at the wrong web site; the only PuTTY we know about |
782 | here is the name of a computer program. |
783 | |
784 | If you want the kind of putty you can buy as an executive toy, the |
785 | PuTTY team can personally recommend Thinking Putty, which you can |
786 | buy from Crazy Aaron's Putty World, at |
787 | \W{http://www.puttyworld.com}\cw{www.puttyworld.com}. |
788 | |
a1d2976b |
789 | \S{faq-pronounce}{Question} How do I pronounce PuTTY? |
ee46ef84 |
790 | |
791 | Exactly like the normal word \q{putty}. Just like the stuff you put |
792 | on window frames. (One of the reasons it's called PuTTY is because |
793 | it makes Windows usable. :-) |