X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/e5b0d077dd2623867702f2e76afb776856eb77b4..b7a189f38294c745ae4ea6efb55891c8196e275b:/doc/config.but diff --git a/doc/config.but b/doc/config.but index 6c5d64f6..909d60fb 100644 --- a/doc/config.but +++ b/doc/config.but @@ -1,4 +1,2161 @@ +\versionid $Id: config.but,v 1.47 2002/12/18 16:23:10 simon Exp $ + \C{config} Configuring PuTTY -\# Walk the user through the whole config box explaining all the -\# options. +This chapter describes all the configuration options in PuTTY. + +PuTTY is configured using the control panel that comes up before you +start a session. Some options can also be changed in the middle of a +session, by selecting \q{Change Settings} from the window menu. + +\H{config-session} The Session panel + +The Session configuration panel contains the basic options you need +to specify in order to open a session at all, and also allows you to +save your settings to be reloaded later. + +\S{config-hostname} The host name section + +\cfg{winhelp-topic}{session.hostname} + +The top box on the Session panel, labelled \q{Specify your +connection by host name}, contains the details that need to be +filled in before PuTTY can open a session at all. + +\b The \q{Host Name} box is where you type the name, or the IP +address, of the server you want to connect to. + +\b The \q{Protocol} radio buttons let you choose what type of +connection you want to make: a raw connection, a Telnet connection, an +rlogin connection or an SSH connection. (See \k{which-one} for a +summary of the differences between SSH, Telnet and rlogin.) + +\b The \q{Port} box lets you specify which port number on the server +to connect to. If you select Telnet, Rlogin, or SSH, this box will +be filled in automatically to the usual value, and you will only +need to change it if you have an unusual server. If you select Raw +mode (see \k{using-rawprot}), you will almost certainly need to fill +in the \q{Port} box. + +\S{config-saving} Loading and storing saved sessions + +\cfg{winhelp-topic}{session.saved} + +The next part of the Session configuration panel allows you to save +your preferred PuTTY options so they will appear automatically the +next time you start PuTTY. It also allows you to create \e{saved +sessions}, which contain a full set of configuration options plus a +host name and protocol. A saved session contains all the information +PuTTY needs to start exactly the session you want. + +\b To save your default settings: first set up the settings the way +you want them saved. Then come back to the Session panel. Select the +\q{Default Settings} entry in the saved sessions list, with a single +click. Then press the \q{Save} button. + +Note that PuTTY does not allow you to save a host name into the +Default Settings entry. This ensures that when PuTTY is started up, +the host name box is always empty, so a user can always just type in +a host name and connect. + +If there is a specific host you want to store the details of how to +connect to, you should create a saved session, which will be +separate from the Default Settings. + +\b To save a session: first go through the rest of the configuration +box setting up all the options you want. Then come back to the +Session panel. Enter a name for the saved session in the \q{Saved +Sessions} input box. (The server name is often a good choice for a +saved session name.) Then press the \q{Save} button. Your saved +session name should now appear in the list box. + +\b To reload a saved session: single-click to select the session +name in the list box, and then press the \q{Load} button. Your saved +settings should all appear in the configuration panel. + +\b To modify a saved session: first load it as described above. Then +make the changes you want. Come back to the Session panel, +single-click to select the session name in the list box, and press +the \q{Save} button. The new settings will be saved over the top of +the old ones. + +\b To start a saved session immediately: double-click on the session +name in the list box. + +\b To delete a saved session: single-click to select the session +name in the list box, and then press the \q{Delete} button. + +Each saved session is independent of the Default Settings +configuration. If you change your preferences and update Default +Settings, you must also update every saved session separately. + +\S{config-closeonexit} \q{Close Window on Exit} + +\cfg{winhelp-topic}{session.coe} + +Finally in the Session panel, there is an option labelled \q{Close +Window on Exit}. This controls whether the PuTTY session window +disappears as soon as the session inside it terminates. If you are +likely to want to copy and paste text out of the session after it +has terminated, you should arrange this option to be off. + +\q{Close Window On Exit} has three settings. \q{Always} means always +close the window on exit; \q{Never} means never close on exit +(always leave the window open). The third setting, and the default +one, is \q{Only on clean exit}. In this mode, a session which +terminates normally will cause its window to close, but one which is +aborted unexpectedly by network trouble or a confusing message from +the server will leave the window up. + +\H{config-logging} The Logging panel + +\cfg{winhelp-topic}{logging.main} + +The Logging configuration panel allows you to save log files of your +PuTTY sessions, for debugging, analysis or future reference. + +The main option is a radio-button set that specifies whether PuTTY +will log anything at all. The options are + +\b \q{Logging turned off completely}. This is the default option; in +this mode PuTTY will not create a log file at all. + +\b \q{Log printable output only}. In this mode, a log file will be +created and written to, but only printable text will be saved into +it. The various terminal control codes that are typically sent down +an interactive session alongside the printable text will be omitted. +This might be a useful mode if you want to read a log file in a text +editor and hope to be able to make sense of it. + +\b \q{Log all session output}. In this mode, \e{everything} sent by +the server into your terminal session is logged. If you view the log +file in a text editor, therefore, you may well find it full of +strange control characters. This is a particularly useful mode if +you are experiencing problems with PuTTY's terminal handling: you +can record everything that went to the terminal, so that someone +else can replay the session later in slow motion and watch to see +what went wrong. + +\b \q{Log SSH packet data}. In this mode (which is only used by SSH +connections), the SSH message packets sent over the encrypted +connection are written to the log file. You might need this to debug +a network-level problem, or more likely to send to the PuTTY authors +as part of a bug report. \e{BE WARNED} that if you log in using a +password, the password will appear in the log file, so be sure to +edit it out before sending the log file to anyone else! + +\S{config-logfilename} \q{Log file name} + +\cfg{winhelp-topic}{logging.filename} + +In this edit box you enter the name of the file you want to log the +session to. The \q{Browse} button will let you look around your file +system to find the right place to put the file; or if you already +know exactly where you want it to go, you can just type a pathname +into the edit box. + +There are a few special features in this box. If you use the \c{&} +character in the file name box, PuTTY will insert details of the +current session in the name of the file it actually opens. The +precise replacements it will do are: + +\b \c{&Y} will be replaced by the current year, as four digits. + +\b \c{&M} will be replaced by the current month, as two digits. + +\b \c{&D} will be replaced by the current day of the month, as two +digits. + +\b \c{&T} will be replaced by the current time, as six digits +(HHMMSS) with no punctuation. + +\b \c{&H} will be replaced by the host name you are connecting to. + +For example, if you enter the host name +\c{c:\\puttylogs\\log-&h-&y&m&d-&t.dat}, you will end up with files looking +like + +\c log-server1.example.com-20010528-110859.dat +\c log-unixbox.somewhere.org-20010611-221001.dat + +\S{config-logfileexists} \q{What to do if the log file already exists} + +\cfg{winhelp-topic}{logging.exists} + +This control allows you to specify what PuTTY should do if it tries +to start writing to a log file and it finds the file already exists. +You might want to automatically destroy the existing log file and +start a new one with the same name. Alternatively, you might want to +open the existing log file and add data to the \e{end} of it. +Finally (the default option), you might not want to have any +automatic behaviour, but to ask the user every time the problem +comes up. + +\H{config-terminal} The Terminal panel + +The Terminal configuration panel allows you to control the behaviour +of PuTTY's terminal emulation. + +\S{config-autowrap} \q{Auto wrap mode initially on} + +\cfg{winhelp-topic}{terminal.autowrap} + +Auto wrap mode controls what happens when text printed in a PuTTY +window reaches the right-hand edge of the window. + +With auto wrap mode on, if a long line of text reaches the +right-hand edge, it will wrap over on to the next line so you can +still see all the text. With auto wrap mode off, the cursor will +stay at the right-hand edge of the screen, and all the characters in +the line will be printed on top of each other. + +If you are running a full-screen application and you occasionally +find the screen scrolling up when it looks as if it shouldn't, you +could try turning this option off. + +Auto wrap mode can be turned on and off by control sequences sent by +the server. This configuration option only controls the \e{default} +state. If you modify this option in mid-session using \q{Change +Settings}, you will need to reset the terminal (see +\k{reset-terminal}) before the change takes effect. + +\S{config-decom} \q{DEC Origin Mode initially on} + +\cfg{winhelp-topic}{terminal.decom} + +DEC Origin Mode is a minor option which controls how PuTTY +interprets cursor-position control sequences sent by the server. + +The server can send a control sequence that restricts the scrolling +region of the display. For example, in an editor, the server might +reserve a line at the top of the screen and a line at the bottom, +and might send a control sequence that causes scrolling operations +to affect only the remaining lines. + +With DEC Origin Mode on, cursor coordinates are counted from the top +of the scrolling region. With it turned off, cursor coordinates are +counted from the top of the whole screen regardless of the scrolling +region. + +It is unlikely you would need to change this option, but if you find +a full-screen application is displaying pieces of text in what looks +like the wrong part of the screen, you could try turning DEC Origin +Mode on to see whether that helps. + +DEC Origin Mode can be turned on and off by control sequences sent +by the server. This configuration option only controls the +\e{default} state. If you modify this option in mid-session using +\q{Change Settings}, you will need to reset the terminal (see +\k{reset-terminal}) before the change takes effect. + +\S{config-crlf} \q{Implicit CR in every LF} + +\cfg{winhelp-topic}{terminal.lfhascr} + +Most servers send two control characters, CR and LF, to start a new +line of the screen. The CR character makes the cursor return to the +left-hand side of the screen. The LF character makes the cursor move +one line down (and might make the screen scroll). + +Some servers only send LF, and expect the terminal to move the +cursor over to the left automatically. If you come across a server +that does this, you will see a stepped effect on the screen, like +this: + +\c First line of text +\c Second line +\c Third line + +If this happens to you, try enabling the \q{Implicit CR in every LF} +option, and things might go back to normal: + +\c First line of text +\c Second line +\c Third line + +\S{config-erase} \q{Use background colour to erase screen} + +\cfg{winhelp-topic}{terminal.bce} + +Not all terminals agree on what colour to turn the screen when the +server sends a \q{clear screen} sequence. Some terminals believe the +screen should always be cleared to the \e{default} background +colour. Others believe the screen should be cleared to whatever the +server has selected as a background colour. + +There exist applications that expect both kinds of behaviour. +Therefore, PuTTY can be configured to do either. + +With this option disabled, screen clearing is always done in the +default background colour. With this option enabled, it is done in +the \e{current} background colour. + +Background-colour erase can be turned on and off by control +sequences sent by the server. This configuration option only +controls the \e{default} state. If you modify this option in +mid-session using \q{Change Settings}, you will need to reset the +terminal (see \k{reset-terminal}) before the change takes effect. + +\S{config-blink} \q{Enable blinking text} + +\cfg{winhelp-topic}{terminal.blink} + +The server can ask PuTTY to display text that blinks on and off. +This is very distracting, so PuTTY allows you to turn blinking text +off completely. + +When blinking text is disabled and the server attempts to make some +text blink, PuTTY will instead display the text with a bolded +background colour. + +Blinking text can be turned on and off by control sequences sent by +the server. This configuration option only controls the \e{default} +state. If you modify this option in mid-session using \q{Change +Settings}, you will need to reset the terminal (see +\k{reset-terminal}) before the change takes effect. + +\S{config-answerback} \q{Answerback to ^E} + +\cfg{winhelp-topic}{terminal.answerback} + +This option controls what PuTTY will send back to the server if the +server sends it the ^E enquiry character. Normally it just sends +the string \q{PuTTY}. + +If you accidentally write the contents of a binary file to your +terminal, you will probably find that it contains more than one ^E +character, and as a result your next command line will probably read +\q{PuTTYPuTTYPuTTY...} as if you had typed the answerback string +multiple times at the keyboard. If you set the answerback string to +be empty, this problem should go away, but doing so might cause +other problems. + +Note that this is \e{not} the feature of PuTTY which the server will +typically use to determine your terminal type. That feature is the +\q{Terminal-type string} in the Connection panel; see +\k{config-termtype} for details. + +You can include control characters in the answerback string using +\c{^C} notation. (Use \c{^~} to get a literal \c{^}.) + +\S{config-localecho} \q{Local echo} + +\cfg{winhelp-topic}{terminal.localecho} + +With local echo disabled, characters you type into the PuTTY window +are not echoed in the window \e{by PuTTY}. They are simply sent to +the server. (The \e{server} might choose to echo them back to you; +this can't be controlled from the PuTTY control panel.) + +Some types of session need local echo, and many do not. In its +default mode, PuTTY will automatically attempt to deduce whether or +not local echo is appropriate for the session you are working in. If +you find it has made the wrong decision, you can use this +configuration option to override its choice: you can force local +echo to be turned on, or force it to be turned off, instead of +relying on the automatic detection. + +\S{config-localedit} \q{Local line editing} + +\cfg{winhelp-topic}{terminal.localedit} + +Normally, every character you type into the PuTTY window is sent +immediately to the server the moment you type it. + +If you enable local line editing, this changes. PuTTY will let you +edit a whole line at a time locally, and the line will only be sent +to the server when you press Return. If you make a mistake, you can +use the Backspace key to correct it before you press Return, and the +server will never see the mistake. + +Since it is hard to edit a line locally without being able to see +it, local line editing is mostly used in conjunction with local echo +(\k{config-localecho}). This makes it ideal for use in raw mode +\#{FIXME} or when connecting to MUDs or talkers. (Although some more +advanced MUDs do occasionally turn local line editing on and turn +local echo off, in order to accept a password from the user.) + +Some types of session need local line editing, and many do not. In +its default mode, PuTTY will automatically attempt to deduce whether +or not local line editing is appropriate for the session you are +working in. If you find it has made the wrong decision, you can use +this configuration option to override its choice: you can force +local line editing to be turned on, or force it to be turned off, +instead of relying on the automatic detection. + +\S{config-printing} Remote-controlled printing + +\cfg{winhelp-topic}{terminal.printing} + +A lot of VT100-compatible terminals support printing under control +of the remote server. PuTTY supports this feature as well, but it is +turned off by default. + +To enable remote-controlled printing, choose a printer from the +\q{Printer to send ANSI printer output to} drop-down list box. This +should allow you to select from all the printers you have installed +drivers for on your computer. Alternatively, you can type the +network name of a networked printer (for example, +\c{\\\\printserver\\printer1}) even if you haven't already +installed a driver for it on your own machine. + +When the remote server attempts to print some data, PuTTY will send +that data to the printer \e{raw} - without translating it, +attempting to format it, or doing anything else to it. It is up to +you to ensure your remote server knows what type of printer it is +talking to. + +Since PuTTY sends data to the printer raw, it cannot offer options +such as portrait versus landscape, print quality, or paper tray +selection. All these things would be done by your PC printer driver +(which PuTTY bypasses); if you need them done, you will have to find +a way to configure your remote server to do them. + +To disable remote printing again, choose \q{None (printing +disabled)} from the printer selection list. This is the default +state. + +\H{config-keyboard} The Keyboard panel + +The Keyboard configuration panel allows you to control the behaviour +of the keyboard in PuTTY. + +\S{config-backspace} Changing the action of the Backspace key + +\cfg{winhelp-topic}{keyboard.backspace} + +Some terminals believe that the Backspace key should send the same +thing to the server as Control-H (ASCII code 8). Other terminals +believe that the Backspace key should send ASCII code 127 (usually +known as Control-?) so that it can be distinguished from Control-H. +This option allows you to choose which code PuTTY generates when you +press Backspace. + +If you are connecting to a Unix system, you will probably find that +the Unix \c{stty} command lets you configure which the server +expects to see, so you might not need to change which one PuTTY +generates. On other systems, the server's expectation might be fixed +and you might have no choice but to configure PuTTY. + +If you do have the choice, we recommend configuring PuTTY to +generate Control-? and configuring the server to expect it, because +that allows applications such as \c{emacs} to use Control-H for +help. + +\S{config-homeend} Changing the action of the Home and End keys + +\cfg{winhelp-topic}{keyboard.homeend} + +The Unix terminal emulator \c{rxvt} disagrees with the rest of the +world about what character sequences should be sent to the server by +the Home and End keys. + +\c{xterm}, and other terminals, send \c{ESC [1~} for the Home key, +and \c{ESC [4~} for the End key. \c{rxvt} sends \c{ESC [H} for the +Home key and \c{ESC [Ow} for the End key. + +If you find an application on which the Home and End keys aren't +working, you could try switching this option to see if it helps. + +\S{config-funkeys} Changing the action of the function keys and keypad + +\cfg{winhelp-topic}{keyboard.funkeys} + +This option affects the function keys (F1 to F12) and the top row of +the numeric keypad. + +\b In the default mode, labelled \c{ESC [n~}, the function keys +generate sequences like \c{ESC [11~}, \c{ESC [12~} and so on. This +matches the general behaviour of Digital's terminals. + +\b In Linux mode, F6 to F12 behave just like the default mode, but +F1 to F5 generate \c{ESC [[A} through to \c{ESC [[E}. This mimics the +Linux virtual console. + +\b In Xterm R6 mode, F5 to F12 behave like the default mode, but F1 +to F4 generate \c{ESC OP} through to \c{ESC OS}, which are the +sequences produced by the top row of the \e{keypad} on Digital's +terminals. + +\b In VT400 mode, all the function keys behave like the default +mode, but the actual top row of the numeric keypad generates \c{ESC +OP} through to \c{ESC OS}. + +\b In VT100+ mode, the function keys generate \c{ESC OP} through to +\c{ESC O[} + +\b In SCO mode, the function keys F1 to F12 generate \c{ESC [M} +through to \c{ESC [X}. Together with shift, they generate \c{ESC [Y} +through to \c{ESC [j}. With control they generate \c{ESC [k} through +to \c{ESC [v}, and with shift and control together they generate +\c{ESC [w} through to \c{ESC [\{}. + +If you don't know what any of this means, you probably don't need to +fiddle with it. + +\S{config-appcursor} Controlling Application Cursor Keys mode + +\cfg{winhelp-topic}{keyboard.appcursor} + +Application Cursor Keys mode is a way for the server to change the +control sequences sent by the arrow keys. In normal mode, the arrow +keys send \c{ESC [A} through to \c{ESC [D}. In application mode, +they send \c{ESC OA} through to \c{ESC OD}. + +Application Cursor Keys mode can be turned on and off by the server, +depending on the application. PuTTY allows you to configure the +initial state. + +You can also disable application cursor keys mode completely, using +the \q{Features} configuration panel; see +\k{config-features-application}. + +\S{config-appkeypad} Controlling Application Keypad mode + +\cfg{winhelp-topic}{keyboard.appkeypad} + +Application Keypad mode is a way for the server to change the +behaviour of the numeric keypad. + +In normal mode, the keypad behaves like a normal Windows keypad: +with NumLock on, the number keys generate numbers, and with NumLock +off they act like the arrow keys and Home, End etc. + +In application mode, all the keypad keys send special control +sequences, \e{including} Num Lock. Num Lock stops behaving like Num +Lock and becomes another function key. + +Depending on which version of Windows you run, you may find the Num +Lock light still flashes on and off every time you press Num Lock, +even when application mode is active and Num Lock is acting like a +function key. This is unavoidable. + +Application keypad mode can be turned on and off by the server, +depending on the application. PuTTY allows you to configure the +initial state. + +You can also disable application keypad mode completely, using the +\q{Features} configuration panel; see +\k{config-features-application}. + +\S{config-nethack} Using NetHack keypad mode + +\cfg{winhelp-topic}{keyboard.nethack} + +PuTTY has a special mode for playing NetHack. You can enable it by +selecting \q{NetHack} in the \q{Initial state of numeric keypad} +control. + +In this mode, the numeric keypad keys 1-9 generate the NetHack +movement commands (\cw{hjklyubn}). The 5 key generates the \c{.} +command (do nothing). + +Better still, pressing Shift with the keypad keys generates the +capital forms of the commands (\cw{HJKLYUBN}), which tells NetHack +to keep moving you in the same direction until you encounter +something interesting. + +For some reason, this feature only works properly when Num Lock is +on. We don't know why. + +\S{config-compose} Enabling a DEC-like Compose key + +\cfg{winhelp-topic}{keyboard.compose} + +DEC terminals have a Compose key, which provides an easy-to-remember +way of typing accented characters. You press Compose and then type +two more characters. The two characters are \q{combined} to produce +an accented character. The choices of character are designed to be +easy to remember; for example, composing \q{e} and \q{`} produces +the \q{\u00e8{e-grave}} character. + +If your keyboard has a Windows Application key, it acts as a Compose +key in PuTTY. Alternatively, if you enable the \q{AltGr acts as +Compose key} option, the AltGr key will become a Compose key. + +\S{config-ctrlalt} \q{Control-Alt is different from AltGr} + +\cfg{winhelp-topic}{keyboard.ctrlalt} + +Some old keyboards do not have an AltGr key, which can make it +difficult to type some characters. PuTTY can be configured to treat +the key combination Ctrl + Left Alt the same way as the AltGr key. + +By default, this checkbox is checked, and the key combination Ctrl + +Left Alt does something completely different. PuTTY's usual handling +of the left Alt key is to prefix the Escape (Control-\cw{[}) +character to whatever character sequence the rest of the keypress +would generate. For example, Alt-A generates Escape followed by +\c{a}. So Alt-Ctrl-A would generate Escape, followed by Control-A. + +If you uncheck this box, Ctrl-Alt will become a synonym for AltGr, +so you can use it to type extra graphic characters if your keyboard +has any. + +(However, Ctrl-Alt will never act as a Compose key, regardless of the +setting of \q{AltGr acts as Compose key} described in +\k{config-compose}.) + +\H{config-bell} The Bell panel + +The Bell panel controls the terminal bell feature: the server's +ability to cause PuTTY to beep at you. + +In the default configuration, when the server sends the character +with ASCII code 7 (Control-G), PuTTY will play the Windows Default +Beep sound. This is not always what you want the terminal bell +feature to do; the Bell panel allows you to configure alternative +actions. + +\S{config-bellstyle} \q{Set the style of bell} + +\cfg{winhelp-topic}{bell.style} + +This control allows you to select various different actions to occur +on a terminal bell: + +\b Selecting \q{None} disables the bell completely. In this mode, +the server can send as many Control-G characters as it likes and +nothing at all will happen. + +\b \q{Play Windows Default Sound} is the default setting. It causes +the Windows \q{Default Beep} sound to be played. To change what this +sound is, or to test it if nothing seems to be happening, use the +Sound configurer in the Windows Control Panel. + +\b \q{Play a custom sound file} allows you to specify a particular +sound file to be used by PuTTY alone, or even by a particular +individual PuTTY session. This allows you to distinguish your PuTTY +beeps from any other beeps on the system. If you select this option, +you will also need to enter the name of your sound file in the edit +control \q{Custom sound file to play as a bell}. + +\b \q{Visual bell} is a silent alternative to a beeping computer. In +this mode, when the server sends a Control-G, the whole PuTTY window +will flash white for a fraction of a second. + +\S{config-belltaskbar} \q{Taskbar/caption indication on bell} + +\cfg{winhelp-topic}{bell.taskbar} + +This feature controls what happens to the PuTTY window's entry in +the Windows Taskbar if a bell occurs while the window does not have +the input focus. + +In the default state (\q{Disabled}) nothing unusual happens. + +If you select \q{Steady}, then when a bell occurs and the window is +not in focus, the window's Taskbar entry and its title bar will +change colour to let you know that PuTTY session is asking for your +attention. The change of colour will persist until you select the +window, so you can leave several PuTTY windows minimised in your +terminal, go away from your keyboard, and be sure not to have missed +any important beeps when you get back. + +\q{Flashing} is even more eye-catching: the Taskbar entry will +continuously flash on and off until you select the window. + +\S{config-bellovl} \q{Control the bell overload behaviour} + +\cfg{winhelp-topic}{bell.overload} + +A common user error in a terminal session is to accidentally run the +Unix command \c{cat} (or equivalent) on an inappropriate file type, +such as an executable, image file, or ZIP file. This produces a huge +stream of non-text characters sent to the terminal, which typically +includes a lot of bell characters. As a result of this the terminal +often doesn't stop beeping for ten minutes, and everybody else in +the office gets annoyed. + +To try to avoid this behaviour, or any other cause of excessive +beeping, PuTTY includes a bell overload management feature. In the +default configuration, receiving more than five bell characters in a +two-second period will cause the overload feature to activate. Once +the overload feature is active, further bells will have no effect at +all, so the rest of your binary file will be sent to the screen in +silence. After a period of five seconds during which no further +bells are received, the overload feature will turn itself off again +and bells will be re-enabled. + +If you want this feature completely disabled, you can turn it off +using the checkbox \q{Bell is temporarily disabled when over-used}. + +Alternatively, if you like the bell overload feature but don't agree +with the settings, you can configure the details: how many bells +constitute an overload, how short a time period they have to arrive +in to do so, and how much silent time is required before the +overload feature will deactivate itself. + +Bell overload mode is always deactivated by any keypress in the +terminal. This means it can respond to large unexpected streams of +data, but does not interfere with ordinary command-line activities +that generate beeps (such as filename completion). + +\H{config-features} The Features panel + +PuTTY's terminal emulation is very highly featured, and can do a lot +of things under remote server control. Some of these features can +cause problems due to buggy or strangely configured server +applications. + +The Features configuration panel allows you to disable some of +PuTTY's more advanced terminal features, in case they cause trouble. + +\S{config-features-application} Disabling application keypad and cursor keys + +\cfg{winhelp-topic}{features.application} + +Application keypad mode (see \k{config-appkeypad}) and application +cursor keys mode (see \k{config-appcursor}) alter the behaviour of +the keypad and cursor keys. Some applications enable these modes but +then do not deal correctly with the modified keys. You can force +these modes to be permanently disabled no matter what the server +tries to do. + +\S{config-features-mouse} Disabling \cw{xterm}-style mouse reporting + +\cfg{winhelp-topic}{features.mouse} + +PuTTY allows the server to send control codes that let it take over +the mouse and use it for purposes other than copy and paste. +Applications which use this feature include the text-mode web +browser \c{links}, the Usenet newsreader \c{trn} version 4, and the +file manager \c{mc} (Midnight Commander). + +If you find this feature inconvenient, you can disable it using the +\q{Disable xterm-style mouse reporting} control. With this box +ticked, the mouse will \e{always} do copy and paste in the normal +way. + +Note that even if the application takes over the mouse, you can +still manage PuTTY's copy and paste by holding down the Shift key +while you select and paste, unless you have deliberately turned this +feature off (see \k{config-mouseshift}). + +\S{config-features-resize} Disabling remote terminal resizing + +\cfg{winhelp-topic}{features.resize} + +PuTTY has the ability to change the terminal's size and position in +response to commands from the server. If you find PuTTY is doing +this unexpectedly or inconveniently, you can tell PuTTY not to +respond to those server commands. + +\S{config-features-altscreen} Disabling switching to the alternate screen + +\cfg{winhelp-topic}{features.altscreen} + +Many terminals, including PuTTY, support an \q{alternate screen}. +This is the same size as the ordinary terminal screen, but separate. +Typically a screen-based program such as a text editor might switch +the terminal to the alternate screen before starting up. Then at the +end of the run, it switches back to the primary screen, and you see +the screen contents just as they were before starting the editor. + +Some people prefer this not to happen. If you want your editor to +run in the same screen as the rest of your terminal activity, you +can disable the alternate screen feature completely. + +\S{config-features-retitle} Disabling remote window title changing + +\cfg{winhelp-topic}{features.retitle} + +PuTTY has the ability to change the window title in response to +commands from the server. If you find PuTTY is doing this +unexpectedly or inconveniently, you can tell PuTTY not to respond to +those server commands. + +\S{config-features-dbackspace} Disabling destructive backspace + +\cfg{winhelp-topic}{features.dbackspace} + +Normally, when PuTTY receives character 127 (^?) from the server, it +will perform a \q{destructive backspace}: move the cursor one space +left and delete the character under it. This can apparently cause +problems in some applications, so PuTTY provides the ability to +configure character 127 to perform a normal backspace (without +deleting a character) instead. + +\S{config-features-charset} Disabling remote character set +configuration + +\cfg{winhelp-topic}{features.charset} + +PuTTY has the ability to change its character set configuration in +response to commands from the server. Some programs send these +commands unexpectedly or inconveniently. In particular, BitchX (an +IRC client) seems to have a habit of reconfiguring the character set +to something other than the user intended. + +If you find that accented characters are not showing up the way you +expect them to, particularly if you're running BitchX, you could try +disabling the remote character set configuration commands. + +\H{config-window} The Window panel + +The Window configuration panel allows you to control aspects of the +PuTTY window. + +\S{config-winsize} Setting the size of the PuTTY window + +\cfg{winhelp-topic}{window.size} + +The \q{Rows} and \q{Columns} boxes let you set the PuTTY window to a +precise size. Of course you can also drag the window to a new size +while a session is running. + +\S{config-winsizelock} What to do when the window is resized + +\cfg{winhelp-topic}{window.resize} + +These options allow you to control what happens when the user tries +to resize the PuTTY window. + +When you resize the PuTTY window, one of four things can happen: + +\b Nothing (if you have completely disabled resizes). + +\b The font size can stay the same and the number of rows and +columns in the terminal can change. + +\b The number of rows and columns in the terminal can stay the same, +and the font size can change. + +\b You can allow PuTTY to change \e{either} the terminal size or the +font size. In this mode it will change the terminal size most of the +time, but enlarge the font when you maximise the window. + +You can control which of these happens using the \q{Lock terminal +size against resizing} and \q{Lock font size against resizing} +options. If you lock both, the window will refuse to be resized at +all. If you lock just the terminal size, the font size will change +when you resize the window. If you lock just the font size, the +terminal size will change when you resize the window. + +\S{config-scrollback} Controlling scrollback + +\cfg{winhelp-topic}{window.scrollback} + +These options let you configure the way PuTTY keeps text after it +scrolls off the top of the screen (see \k{using-scrollback}). + +The \q{Lines of scrollback} box lets you configure how many lines of +text PuTTY keeps. The \q{Display scrollbar} options allow you to +hide the scrollbar (although you can still view the scrollback using +Shift-PgUp and Shift-PgDn). You can separately configure whether the +scrollbar is shown in full-screen mode and in normal modes. + +If you are viewing part of the scrollback when the server sends more +text to PuTTY, the screen will revert to showing the current +terminal contents. You can disable this behaviour by turning off +\q{Reset scrollback on display activity}. You can also make the +screen revert when you press a key, by turning on \q{Reset +scrollback on keypress}. + +\H{config-appearance} The Appearance panel + +The Appearance configuration panel allows you to control aspects of +the appearance of PuTTY's window. + +\S{config-cursor} Controlling the appearance of the cursor + +\cfg{winhelp-topic}{appearance.cursor} + +The \q{Cursor appearance} option lets you configure the cursor to be +a block, an underline, or a vertical line. A block cursor becomes an +empty box when the window loses focus; an underline or a vertical +line becomes dotted. + +The \q{Cursor blinks} option makes the cursor blink on and off. This +works in any of the cursor modes. + +\S{config-font} Controlling the font used in the terminal window + +\cfg{winhelp-topic}{appearance.font} + +This option allows you to choose what font, in what size, the PuTTY +terminal window uses to display the text in the session. You will be +offered a choice from all the fixed-width fonts installed on the +system. (VT100-style terminal handling can only deal with fixed- +width fonts.) + +\S{config-title} Controlling the window title + +\cfg{winhelp-topic}{appearance.title} + +The \q{Window title} edit box allows you to set the title of the +PuTTY window. By default the window title will contain the host name +followed by \q{PuTTY}, for example \c{server1.example.com - PuTTY}. +If you want a different window title, this is where to set it. + +PuTTY allows the server to send \c{xterm} control sequences which +modify the title of the window in mid-session. There is also an +\c{xterm} sequence to modify the title of the window's \e{icon}. +This makes sense in a windowing system where the window becomes an +icon when minimised, such as Windows 3.1 or most X Window System +setups; but in the Windows 95-like user interface it isn't as +applicable. By default PuTTY's window title and Taskbar caption will +change into the server-supplied icon title if you minimise the PuTTY +window, and change back to the server-supplied window title if you +restore it. (If the server has not bothered to supply a window or +icon title, none of this will happen.) By checking the box marked +\q{Avoid ever using icon title}, you can arrange that PuTTY will +always display the window title, and completely ignore any icon +titles the server sends it. + +\S{config-mouseptr} \q{Hide mouse pointer when typing in window} + +\cfg{winhelp-topic}{appearance.hidemouse} + +If you enable this option, the mouse pointer will disappear if the +PuTTY window is selected and you press a key. This way, it will not +obscure any of the text in the window while you work in your +session. As soon as you move the mouse, the pointer will reappear. + +This option is disabled by default, so the mouse pointer remains +visible at all times. + +\S{config-winborder} Controlling the window border + +\cfg{winhelp-topic}{appearance.border} + +PuTTY allows you to configure the appearance of the window border to +some extent. + +The checkbox marked \q{Sunken-edge border} changes the appearance of +the window border to something more like a DOS box: the inside edge +of the border is highlighted as if it sank down to meet the surface +inside the window. This makes the border a little bit thicker as +well. It's hard to describe well. Try it and see if you like it. + +You can also configure a completely blank gap between the text in +the window and the border, using the \q{Gap between text and window +edge} control. By default this is set at one pixel. You can reduce +it to zero, or increase it further. + +\H{config-behaviour} The Behaviour panel + +The Behaviour configuration panel allows you to control aspects of +the behaviour of PuTTY's window. + +\S{config-warnonclose} \q{Warn before closing window} + +\cfg{winhelp-topic}{behaviour.closewarn} + +If you press the Close button in a PuTTY window that contains a +running session, PuTTY will put up a warning window asking if you +really meant to close the window. A window whose session has already +terminated can always be closed without a warning. + +If you want to be able to close a window quickly, you can disable +the \q{Warn before closing window} option. + +\S{config-altf4} \q{Window closes on ALT-F4} + +\cfg{winhelp-topic}{behaviour.altf4} + +By default, pressing ALT-F4 causes the window to close (or a warning +box to appear; see \k{config-warnonclose}). If you disable the +\q{Window closes on ALT-F4} option, then pressing ALT-F4 will simply +send a key sequence to the server. + +\S{config-altspace} \q{System menu appears on ALT-Space} + +\cfg{winhelp-topic}{behaviour.altspace} + +If this option is enabled, then pressing ALT-Space will bring up the +PuTTY window's menu, like clicking on the top left corner. If it is +disabled, then pressing ALT-Space will just send \c{ESC SPACE} to +the server. + +Some accessibility programs for Windows may need this option +enabling to be able to control PuTTY's window successfully. For +instance, Dragon NaturallySpeaking requires it both to open the +system menu via voice, and to close, minimise, maximise and restore +the window. + +\S{config-altonly} \q{System menu appears on Alt alone} + +\cfg{winhelp-topic}{behaviour.altonly} + +If this option is enabled, then pressing and releasing ALT will +bring up the PuTTY window's menu, like clicking on the top left +corner. If it is disabled, then pressing and releasing ALT will have +no effect. + +\S{config-alwaysontop} \q{Ensure window is always on top} + +\cfg{winhelp-topic}{behaviour.alwaysontop} + +If this option is enabled, the PuTTY window will stay on top of all +other windows. + +\S{config-fullscreen} \q{Full screen on Alt-Enter} + +\cfg{winhelp-topic}{behaviour.altenter} + +If this option is enabled, then pressing Alt-Enter will cause the +PuTTY window to become full-screen. Pressing Alt-Enter again will +restore the previous window size. + +The full-screen feature is also available from the System menu, even +when it is configured not to be available on the Alt-Enter key. See +\k{using-fullscreen}. + +\H{config-translation} The Translation panel + +The Translation configuration panel allows you to control the +translation between the character set understood by the server and +the character set understood by PuTTY. + +\S{config-charset} Controlling character set translation + +\cfg{winhelp-topic}{translation.codepage} + +During an interactive session, PuTTY receives a stream of 8-bit +bytes from the server, and in order to display them on the screen it +needs to know what character set to interpret them in. + +There are a lot of character sets to choose from. The \q{Received +data assumed to be in which character set} option lets you select +one. By default PuTTY will attempt to choose a character set that is +right for your locale as reported by Windows; if it gets it wrong, +you can select a different one using this control. + +A few notable character sets are: + +\b The ISO-8859 series are all standard character sets that include +various accented characters appropriate for different sets of +languages. + +\b The Win125x series are defined by Microsoft, for similar +purposes. In particular Win1252 is almost equivalent to ISO-8859-1, +but contains a few extra characters such as matched quotes and the +Euro symbol. + +\b If you want the old IBM PC character set with block graphics and +line-drawing characters, you can select \q{CP437}. + +\b PuTTY also supports Unicode mode, in which the data coming from +the server is interpreted as being in the UTF-8 encoding of Unicode. +If you select \q{UTF-8} as a character set you can use this mode. +Not all server-side applications will support it. + +If you need support for a numeric code page which is not listed in +the drop-down list, such as code page 866, then you should be able +to enter its name manually (\c{CP866} for example) in the list box +and get the right result. + +\S{config-cyr} \q{Caps Lock acts as Cyrillic switch} + +\cfg{winhelp-topic}{translation.cyrillic} + +This feature allows you to switch between a US/UK keyboard layout +and a Cyrillic keyboard layout by using the Caps Lock key, if you +need to type (for example) Russian and English side by side in the +same document. + +Currently this feature is not expected to work properly if your +native keyboard layout is not US or UK. + +\S{config-linedraw} Controlling display of line drawing characters + +\cfg{winhelp-topic}{translation.linedraw} + +VT100-series terminals allow the server to send control sequences +that shift temporarily into a separate character set for drawing +lines and boxes. PuTTY has a variety of ways to support this +capability. In general you should probably try lots of options until +you find one that your particular font supports. + +\b \q{Font has XWindows encoding} is for use with fonts that have a +special encoding, where the lowest 32 character positions (below the +ASCII printable range) contain the line-drawing characters. This is +unlikely to be the case with any standard Windows font; it will +probably only apply to custom-built fonts or fonts that have been +automatically converted from the X Window System. + +\b \q{Use font in both ANSI and OEM modes} tries to use the same +font in two different character sets, to obtain a wider range of +characters. This doesn't always work; some fonts claim to be a +different size depending on which character set you try to use. + +\b \q{Use font in OEM mode only} is more reliable than that, but can +miss out other characters from the main character set. + +\b \q{Poor man's line drawing} assumes that the font \e{cannot} +generate the line and box characters at all, so it will use the +\c{+}, \c{-} and \c{|} characters to draw approximations to boxes. +You should use this option if none of the other options works. + +\b \q{Unicode mode} tries to use the box characters that are present +in Unicode. For good Unicode-supporting fonts this is probably the +most reliable and functional option. + +\H{config-selection} The Selection panel + +The Selection panel allows you to control the way copy and paste +work in the PuTTY window. + +\S{config-linedrawpaste} Controlling the pasting of line drawing +characters + +\cfg{winhelp-topic}{selection.linedraw} + +By default, when you copy and paste a piece of the PuTTY screen that +contains VT100 line and box drawing characters, PuTTY will translate +them into the \q{poor man's} line-drawing characters \c{+}, \c{-} +and \c{|}. The checkbox \q{Don't translate line drawing chars} +disables this feature, so line-drawing characters will be pasted as +if they were in the normal character set. This will typically mean +they come out mostly as \c{q} and \c{x}, with a scattering of +\c{jklmntuvw} at the corners. This might be useful if you were +trying to recreate the same box layout in another program, for +example. + +\S{config-rtfpaste} Pasting in Rich Text Format + +\cfg{winhelp-topic}{selection.rtf} + +If you enable \q{Paste to clipboard in RTF as well as plain text}, +PuTTY will write formatting information to the clipboard as well as +the actual text you copy. Currently the only effect of this will be +that if you paste into (say) a word processor, the text will appear +in the word processor in the same font PuTTY was using to display +it. In future it is likely that other formatting information (bold, +underline, colours) will be copied as well. + +This option can easily be inconvenient, so by default it is +disabled. + +\S{config-mouse} Changing the actions of the mouse buttons + +\cfg{winhelp-topic}{selection.buttons} + +PuTTY's copy and paste mechanism is modelled on the Unix \c{xterm} +application. The X Window System uses a three-button mouse, and the +convention is that the left button selects, the right button extends +an existing selection, and the middle button pastes. + +Windows typically only has two mouse buttons, so in PuTTY's default +configuration, the \e{right} button pastes, and the \e{middle} +button (if you have one) extends a selection. + +If you have a three-button mouse and you are already used to the +\c{xterm} arrangement, you can select it using the \q{Action of +mouse buttons} control. + +\S{config-mouseshift} \q{Shift overrides application's use of mouse} + +\cfg{winhelp-topic}{selection.shiftdrag} + +PuTTY allows the server to send control codes that let it take over +the mouse and use it for purposes other than copy and paste. +Applications which use this feature include the text-mode web +browser \c{links}, the Usenet newsreader \c{trn} version 4, and the +file manager \c{mc} (Midnight Commander). + +When running one of these applications, pressing the mouse buttons +no longer performs copy and paste. If you do need to copy and paste, +you can still do so if you hold down Shift while you do your mouse +clicks. + +However, it is possible in theory for applications to even detect +and make use of Shift + mouse clicks. We don't know of any +applications that do this, but in case someone ever writes one, +unchecking the \q{Shift overrides application's use of mouse} +checkbox will cause Shift + mouse clicks to go to the server as well +(so that mouse-driven copy and paste will be completely disabled). + +If you want to prevent the application from taking over the mouse at +all, you can do this using the Features control panel; see +\k{config-features-mouse}. + +\S{config-rectselect} Default selection mode + +\cfg{winhelp-topic}{selection.rect} + +As described in \k{using-selection}, PuTTY has two modes of +selecting text to be copied to the clipboard. In the default mode +(\q{Normal}), dragging the mouse from point A to point B selects to +the end of the line containing A, all the lines in between, and from +the very beginning of the line containing B. In the other mode +(\q{Rectangular block}), dragging the mouse between two points +defines a rectangle, and everything within that rectangle is copied. + +Normally, you have to hold down Alt while dragging the mouse to +select a rectangular block. Using the \q{Default selection mode} +control, you can set rectangular selection as the default, and then +you have to hold down Alt to get the \e{normal} behaviour. + +\S{config-charclasses} Configuring word-by-word selection + +\cfg{winhelp-topic}{selection.charclasses} + +PuTTY will select a word at a time in the terminal window if you +double-click to begin the drag. This panel allows you to control +precisely what is considered to be a word. + +Each character is given a \e{class}, which is a small number +(typically 0, 1 or 2). PuTTY considers a single word to be any +number of adjacent characters in the same class. So by modifying the +assignment of characters to classes, you can modify the word-by-word +selection behaviour. + +In the default configuration, the character classes are: + +\b Class 0 contains white space and control characters. + +\b Class 1 contains most punctuation. + +\b Class 2 contains letters, numbers and a few pieces of punctuation +(the double quote, minus sign, period, forward slash and +underscore). + +So, for example, if you assign the \c{@} symbol into character class +2, you will be able to select an e-mail address with just a double +click. + +In order to adjust these assignments, you start by selecting a group +of characters in the list box. Then enter a class number in the edit +box below, and press the \q{Set} button. + +This mechanism currently only covers ASCII characters, because it +isn't feasible to expand the list to cover the whole of Unicode. + +Character class definitions can be modified by control sequences +sent by the server. This configuration option only controls the +\e{default} state. If you modify this option in mid-session using +\q{Change Settings}, you will need to reset the terminal (see +\k{reset-terminal}) before the change takes effect. + +\H{config-colours} The Colours panel + +The Colours panel allows you to control PuTTY's use of colour. + +\S{config-boldcolour} \q{Bolded text is a different colour} + +\cfg{winhelp-topic}{colours.bold} + +When the server sends a control sequence indicating that some text +should be displayed in bold, PuTTY can handle this two ways. It can +either change the font for a bold version, or use the same font in a +brighter colour. This control lets you choose which. + +By default the box is checked, so non-bold text is displayed in +light grey and bold text is displayed in bright white (and similarly +in other colours). If you uncheck the box, bold and non-bold text +will be displayed in the same colour, and instead the font will +change to indicate the difference. + +\S{config-logpalette} \q{Attempt to use logical palettes} + +\cfg{winhelp-topic}{colours.logpal} + +Logical palettes are a mechanism by which a Windows application +running on an 8-bit colour display can select precisely the colours +it wants instead of going with the Windows standard defaults. + +If you are not getting the colours you ask for on an 8-bit display, +you can try enabling this option. However, be warned that it's never +worked very well. + +\S{config-colourcfg} Adjusting the colours in the terminal window + +\cfg{winhelp-topic}{colours.config} + +The main colour control allows you to specify exactly what colours +things should be displayed in. To modify one of the PuTTY colours, +use the list box to select which colour you want to modify. The RGB +values for that colour will appear on the right-hand side of the +list box. Now, if you press the \q{Modify} button, you will be +presented with a colour selector, in which you can choose a new +colour to go in place of the old one. + +PuTTY allows you to set the cursor colour, the default foreground +and background, and the precise shades of all the ANSI configurable +colours (black, red, green, yellow, blue, magenta, cyan, and white). +In addition, if you have selected \q{Bolded text is a different +colour}, you can also modify the precise shades used for the bold +versions of these colours. + +\H{config-connection} The Connection panel + +The Connection panel allows you to configure options that apply to +more than one type of connection. + +\S{config-termtype} \q{Terminal-type string} + +\cfg{winhelp-topic}{connection.termtype} + +Most servers you might connect to with PuTTY are designed to be +connected to from lots of different types of terminal. In order to +send the right control sequences to each one, the server will need +to know what type of terminal it is dealing with. Therefore, each of +the SSH, Telnet and Rlogin protocols allow a text string to be sent +down the connection describing the terminal. + +PuTTY attempts to emulate the Unix \c{xterm} program, and by default +it reflects this by sending \c{xterm} as a terminal-type string. If +you find this is not doing what you want - perhaps the remote +terminal reports \q{Unknown terminal type} - you could try setting +this to something different, such as \c{vt220}. + +If you're not sure whether a problem is due to the terminal type +setting or not, you probably need to consult the manual for your +application or your server. + +\S{config-username} \q{Auto-login username} + +\cfg{winhelp-topic}{connection.username} + +All three of the SSH, Telnet and Rlogin protocols allow you to +specify what user name you want to log in as, without having to type +it explicitly every time. (Some Telnet servers don't support this.) + +In this box you can type that user name. + +\S{config-keepalive} Using keepalives to prevent disconnection + +\cfg{winhelp-topic}{connection.keepalive} + +If you find your sessions are closing unexpectedly (\q{Connection +reset by peer}) after they have been idle for a while, you might +want to try using this option. + +Some network routers and firewalls need to keep track of all +connections through them. Usually, these firewalls will assume a +connection is dead if no data is transferred in either direction +after a certain time interval. This can cause PuTTY sessions to be +unexpectedly closed by the firewall if no traffic is seen in the +session for some time. + +The keepalive option (\q{Seconds between keepalives}) allows you to +configure PuTTY to send data through the session at regular +intervals, in a way that does not disrupt the actual terminal +session. If you find your firewall is cutting idle connections off, +you can try entering a non-zero value in this field. The value is +measured in seconds; so, for example, if your firewall cuts +connections off after ten minutes then you might want to enter 300 +seconds (5 minutes) in the box. + +Note that keepalives are not always helpful. They help if you have a +firewall which drops your connection after an idle period; but if +the network between you and the server suffers from breaks in +connectivity then keepalives can actually make things worse. If a +session is idle, and connectivity is temporarily lost between the +endpoints, but the connectivity is restored before either side tries +to send anything, then there will be no problem - neither endpoint +will notice that anything was wrong. However, if one side does send +something during the break, it will repeatedly try to re-send, and +eventually give up and abandon the connection. Then when +connectivity is restored, the other side will find that the first +side doesn't believe there is an open connection any more. +Keepalives can make this sort of problem worse, because they +increase the probability that PuTTY will attempt to send data during +a break in connectivity. Therefore, you might find they help +connection loss, or you might find they make it worse, depending on +what \e{kind} of network problems you have between you and the +server. + +Keepalives are only supported in Telnet and SSH; the Rlogin and Raw +protocols offer no way of implementing them. + +Note that if you are using SSH1 and the server has a bug that makes +it unable to deal with SSH1 ignore messages (see +\k{config-ssh-bug-ignore1}), enabling keepalives will have no effect. + +\S{config-nodelay} \q{Disable Nagle's algorithm} + +\cfg{winhelp-topic}{connection.nodelay} + +Nagle's algorithm is a detail of TCP/IP implementations that tries +to minimise the number of small data packets sent down a network +connection. With Nagle's algorithm enabled, PuTTY's bandwidth usage +will be slightly more efficient; with it disabled, you may find you +get a faster response to your keystrokes when connecting to some +types of server. + +The Nagle algorithm is disabled by default. + +\H{config-proxy} The Proxy panel + +\cfg{winhelp-topic}{proxy.main} + +The Proxy panel allows you to configure PuTTY to use various types +of proxy in order to make its network connections. The settings in +this panel affect the primary network connection forming your PuTTY +session, but also any extra connections made as a result of SSH port +forwarding (see \k{using-port-forwarding}). + +\S{config-proxy-type} Setting the proxy type + +\cfg{winhelp-topic}{proxy.type} + +The \q{Proxy type} radio buttons allow you to configure what type of +proxy you want PuTTY to use for its network connections. The default +setting is \q{None}; in this mode no proxy is used for any +connection. + +\b Selecting \q{HTTP} allows you to proxy your connections through a +web server supporting the HTTP \cw{CONNECT} command, as documented +in \W{http://www.ietf.org/rfc/rfc2817.txt}{RFC 2817}. + +\b Selecting \q{SOCKS} allows you to proxy your connections through +a SOCKS server. + +\b Many firewalls implement a less formal type of proxy in which a +user can make a Telnet connection directly to the firewall machine +and enter a command such as \c{connect myhost.com 22} to connect +through to an external host. Selecting \q{Telnet} allows you to tell +PuTTY to use this type of proxy. + +\S{config-proxy-exclude} Excluding parts of the network from proxying + +\cfg{winhelp-topic}{proxy.exclude} + +Typically you will only need to use a proxy to connect to non-local +parts of your network; for example, your proxy might be required for +connections outside your company's internal network. In the +\q{Exclude Hosts/IPs} box you can enter ranges of IP addresses, or +ranges of DNS names, for which PuTTY will avoid using the proxy and +make a direct connection instead. + +The \q{Exclude Hosts/IPs} box may contain more than one exclusion +range, separated by commas. Each range can be an IP address or a DNS +name, with a \c{*} character allowing wildcards. For example: + +\c *.example.com + +This excludes any host with a name ending in \c{.example.com} from +proxying. + +\c 192.168.88.* + +This excludes any host with an IP address starting with 192.168.88 +from proxying. + +\c 192.168.88.*,*.example.com + +This excludes both of the above ranges at once. + +Connections to the local host (the host name \c{localhost}, and any +loopback IP address) are never proxied, even if the proxy exclude +list does not explicitly contain them. It is very unlikely that this +behaviour would ever cause problems, but if it does you can change +it by enabling \q{Consider proxying local host connections}. + +Note that if you are doing DNS at the proxy (see +\k{config-proxy-dns}), you should make sure that your proxy +exclusion settings do not depend on knowing the IP address of a +host. If the name is passed on to the proxy without PuTTY looking it +up, it will never know the IP address and cannot check it against +your list. + +\S{config-proxy-dns} Name resolution when using a proxy + +\cfg{winhelp-topic}{proxy.dns} + +If you are using a proxy to access a private network, it can make a +difference whether DNS name resolution is performed by PuTTY itself +(on the client machine) or performed by the proxy. + +The \q{Do DNS name lookup at proxy end} configuration option allows +you to control this. If you set it to \q{No}, PuTTY will always do +its own DNS, and will always pass an IP address to the proxy. If you +set it to \q{Yes}, PuTTY will always pass host names straight to the +proxy without trying to look them up first. + +If you set this option to \q{Auto} (the default), PuTTY will do +something it considers appropriate for each type of proxy. Telnet +and HTTP proxies will have host names passed straight to them; SOCKS +proxies will not. + +Note that if you are doing DNS at the proxy, you should make sure +that your proxy exclusion settings (see \k{config-proxy-exclude}) do +not depend on knowing the IP address of a host. If the name is +passed on to the proxy without PuTTY looking it up, it will never +know the IP address and cannot check it against your list. + +The original SOCKS 4 protocol does not support proxy-side DNS. There +is a protocol extension (SOCKS 4A) which does support it, but not +all SOCKS 4 servers provide this extension. If you enable proxy DNS +and your SOCKS 4 server cannot deal with it, this might be why. + +\S{config-proxy-auth} Username and password + +\cfg{winhelp-topic}{proxy.auth} + +If your proxy requires authentication, you can enter a username and +a password in the \q{Username} and \q{Password} boxes. + +Authentication is not supported for all forms of proxy: + +\b Username and password authentication is supported for HTTP +proxies and SOCKS 5 proxies. + +\b SOCKS 4 can use the \q{Username} field, but does not support +passwords. + +\b You can specify a way to include a username and password in the +Telnet proxy command (see \k{config-proxy-command}). + +\S{config-proxy-command} Specifying the Telnet proxy command + +\cfg{winhelp-topic}{proxy.command} + +If you are using the Telnet proxy type, the usual command required +by the firewall's Telnet server is \c{connect}, followed by a host +name and a port number. If your proxy needs a different command, +you can enter an alternative here. + +In this string, you can use \c{\\n} to represent a new-line, \c{\\r} +to represent a carriage return, \c{\\t} to represent a tab +character, and \c{\\x} followed by two hex digits to represent any +other character. \c{\\\\} is used to encode the \c{\\} character +itself. + +Also, the special strings \c{%host} and \c{%port} will be replaced +by the host name and port number you want to connect to. The strings +\c{%user} and \c{%pass} will be replaced by the proxy username and +password you specify. To get a literal \c{%} sign, enter \c{%%}. + +If the Telnet proxy server prompts for a username and password +before commands can be sent, you can use a command such as: + +\c %user\\n%pass\\nconnect %host %port\\n + +This will send your username and password as the first two lines to +the proxy, followed by a command to connect to the desired host and +port. Note that if you do not include the \c{%user} or \c{%pass} +tokens in the Telnet command, then the \q{Username} and \q{Password} +configuration fields will be ignored. + +\S{config-proxy-socksver} Selecting the version of the SOCKS protocol + +\cfg{winhelp-topic}{proxy.socksver} + +SOCKS servers exist in two versions: version 5 +(\W{http://www.ietf.org/rfc/rfc1928.txt}{RFC 1928}) and the earlier +version 4. The \q{SOCKS Version} radio buttons allow you to select +which one to use, if you have selected the SOCKS proxy type. + +\H{config-telnet} The Telnet panel + +The Telnet panel allows you to configure options that only apply to +Telnet sessions. + +\S{config-termspeed} \q{Terminal-speed string} + +\cfg{winhelp-topic}{telnet.termspeed} + +Telnet allows the client to send a text string that describes the +terminal speed. PuTTY lets you configure this, in case you find the +server is reacting badly to the default value. (I'm not aware of any +servers that do have a problem with it.) + +\S{config-environ} Setting environment variables on the server + +\cfg{winhelp-topic}{telnet.environ} + +The Telnet protocol also provides a means for the client to pass +environment variables to the server. Many Telnet servers have +stopped supporting this feature due to security flaws, but PuTTY +still supports it for the benefit of any servers which have found +other ways around the security problems than just disabling the +whole mechanism. + +To add an environment variable to the list transmitted down the +connection, you enter the variable name in the \q{Variable} box, +enter its value in the \q{Value} box, and press the \q{Add} button. +To remove one from the list, select it in the list box and press +\q{Remove}. + +\S{config-oldenviron} \q{Handling of OLD_ENVIRON ambiguity} + +\cfg{winhelp-topic}{telnet.oldenviron} + +The original Telnet mechanism for passing environment variables was +badly specified. At the time the standard (RFC 1408) was written, +BSD telnet implementations were already supporting the feature, and +the intention of the standard was to describe the behaviour the BSD +implementations were already using. + +Sadly there was a typing error in the standard when it was issued, +and two vital function codes were specified the wrong way round. BSD +implementations did not change, and the standard was not corrected. +Therefore, it's possible you might find either BSD or RFC-compliant +implementations out there. This switch allows you to choose which +one PuTTY claims to be. + +The problem was solved by issuing a second standard, defining a new +Telnet mechanism called \cw{NEW_ENVIRON}, which behaved exactly like +the original \cw{OLD_ENVIRON} but was not encumbered by existing +implementations. Most Telnet servers now support this, and it's +unambiguous. This feature should only be needed if you have trouble +passing environment variables to quite an old server. + +\S{config-ptelnet} Passive and active Telnet negotiation modes + +\cfg{winhelp-topic}{telnet.passive} + +In a Telnet connection, there are two types of data passed between +the client and the server: actual text, and \e{negotiations} about +which Telnet extra features to use. + +PuTTY can use two different strategies for negotiation: + +\b In \e{active} mode, PuTTY starts to send negotiations as soon as +the connection is opened. + +\b In \e{passive} mode, PuTTY will wait to negotiate until it sees a +negotiation from the server. + +The obvious disadvantage of passive mode is that if the server is +also operating in a passive mode, then negotiation will never begin +at all. For this reason PuTTY defaults to active mode. + +However, sometimes passive mode is required in order to successfully +get through certain types of firewall and Telnet proxy server. If +you have confusing trouble with a firewall, you could try enabling +passive mode to see if it helps. + +\S{config-telnetkey} \q{Keyboard sends telnet Backspace and Interrupt} + +\cfg{winhelp-topic}{telnet.specialkeys} + +If this box is checked, the Backspace key on the keyboard will send +the Telnet special backspace code, and Control-C will send the +Telnet special interrupt code. You probably shouldn't enable this +unless you know what you're doing. + +\S{config-telnetnl} \q{Return key sends telnet New Line instead of ^M} + +\cfg{winhelp-topic}{telnet.newline} + +Unlike most other remote login protocols, the Telnet protocol has a +special \q{new line} code that is not the same as the usual line +endings of Control-M or Control-J. By default, PuTTY sends the +Telnet New Line code when you press Return, instead of sending +Control-M as it does in most other protocols. + +Most Unix-style Telnet servers don't mind whether they receive +Telnet New Line or Control-M; some servers do expect New Line, and +some servers prefer to see ^M. If you are seeing surprising +behaviour when you press Return in a Telnet session, you might try +turning this option off to see if it helps. + +\H{config-rlogin} The Rlogin panel + +The Rlogin panel allows you to configure options that only apply to +Rlogin sessions. + +\S{config-rlogin-termspeed} \q{Terminal-speed string} + +\cfg{winhelp-topic}{rlogin.termspeed} + +Like Telnet, Rlogin allows the client to send a text string that +describes the terminal speed. PuTTY lets you configure this, in case +you find the server is reacting badly to the default value. (I'm not +aware of any servers that do have a problem with it.) + +\S{config-rlogin-localuser} \q{Local username} + +\cfg{winhelp-topic}{rlogin.localuser} + +Rlogin allows an automated (password-free) form of login by means of +a file called \c{.rhosts} on the server. You put a line in your +\c{.rhosts} file saying something like \c{jbloggs@pc1.example.com}, +and then when you make an Rlogin connection the client transmits the +username of the user running the Rlogin client. The server checks +the username and hostname against \c{.rhosts}, and if they match it +does not ask for a password. + +This only works because Unix systems contain a safeguard to stop a +user from pretending to be another user in an Rlogin connection. +Rlogin connections have to come from port numbers below 1024, and +Unix systems prohibit this to unprivileged processes; so when the +server sees a connection from a low-numbered port, it assumes the +client end of the connection is held by a privileged (and therefore +trusted) process, so it believes the claim of who the user is. + +Windows does not have this restriction: \e{any} user can initiate an +outgoing connection from a low-numbered port. Hence, the Rlogin +\c{.rhosts} mechanism is completely useless for securely +distinguishing several different users on a Windows machine. If you +have a \c{.rhosts} entry pointing at a Windows PC, you should assume +that \e{anyone} using that PC can spoof your username in an Rlogin +connection and access your account on the server. + +The \q{Local username} control allows you to specify what user name +PuTTY should claim you have, in case it doesn't match your Windows +user name (or in case you didn't bother to set up a Windows user +name). + +\H{config-ssh} The SSH panel + +The SSH panel allows you to configure options that only apply to +SSH sessions. + +\S{config-command} Executing a specific command on the server + +\cfg{winhelp-topic}{ssh.command} + +In SSH, you don't have to run a general shell session on the server. +Instead, you can choose to run a single specific command (such as a +mail user agent, for example). If you want to do this, enter the +command in the \q{Remote command} box. + +\S{config-ssh-pty} \q{Don't allocate a pseudo-terminal} + +\cfg{winhelp-topic}{ssh.nopty} + +When connecting to a Unix system, most interactive shell sessions +are run in a \e{pseudo-terminal}, which allows the Unix system to +pretend it's talking to a real physical terminal device but allows +the SSH server to catch all the data coming from that fake device +and send it back to the client. + +Occasionally you might find you have a need to run a session \e{not} +in a pseudo-terminal. In PuTTY, this is generally only useful for +very specialist purposes; although in Plink (see \k{plink}) it is +the usual way of working. + +\S{config-ssh-comp} \q{Enable compression} + +\cfg{winhelp-topic}{ssh.compress} + +This enables data compression in the SSH connection: data sent by +the server is compressed before sending, and decompressed at the +client end. Likewise, data sent by PuTTY to the server is compressed +first and the server decompresses it at the other end. This can help +make the most of a low-bandwidth connection. + +\S{config-ssh-prot} \q{Preferred SSH protocol version} + +\cfg{winhelp-topic}{ssh.protocol} + +This allows you to select whether you would like to use SSH protocol +version 1 or version 2. \#{FIXME: say something about this elsewhere?} + +PuTTY will attempt to use protocol 1 if the server you connect to +does not offer protocol 2, and vice versa. + +If you select \q{1 only} or \q{2 only} here, PuTTY will only connect +if the server you connect to offers the SSH protocol version you +have specified. + +\S{config-ssh-encryption} Encryption algorithm selection + +\cfg{winhelp-topic}{ssh.ciphers} + +PuTTY supports a variety of different encryption algorithms, and +allows you to choose which one you prefer to use. You can do this by +dragging the algorithms up and down in the list box (or moving them +using the Up and Down buttons) to specify a preference order. When +you make an SSH connection, PuTTY will search down the list from the +top until it finds an algorithm supported by the server, and then +use that. + +If the algorithm PuTTY finds is below the \q{warn below here} line, +you will see a warning box when you make the connection: + +\c The first cipher supported by the server +\c is single-DES, which is below the configured +\c warning threshold. +\c Do you want to continue with this connection? + +This warns you that the first available encryption is not a very +secure one. Typically you would put the \q{warn below here} line +between the encryptions you consider secure and the ones you +consider substandard. By default, PuTTY supplies a preference order +intended to reflect a reasonable preference in terms of security and +speed. + +In SSH-2, the encryption algorithm is negotiated independently for +each direction of the connection, although PuTTY does not support +separate configuration of the preference orders. As a result you may +get two warnings similar to the one above, possibly with different +encryptions. + +Single-DES is not supported natively in the SSH 2 draft protocol +standards. One or two server implementations do support it, by a +non-standard name. PuTTY can use single-DES to interoperate with +these servers if you enable the \q{Enable non-standard single-DES in +SSH 2} option; by default this is disabled and PuTTY will stick to +the standard. + +\H{config-ssh-auth} The Auth panel + +The Auth panel allows you to configure authentication options for +SSH sessions. + +\S{config-ssh-tis} \q{Attempt TIS or CryptoCard authentication} + +\cfg{winhelp-topic}{ssh.auth.tis} + +TIS and CryptoCard authentication are simple challenge/response +forms of authentication available in SSH protocol version 1 only. +You might use them if you were using S/Key one-time passwords, for +example, or if you had a physical security token that generated +responses to authentication challenges. + +With this switch enabled, PuTTY will attempt these forms of +authentication if the server is willing to try them. You will be +presented with a challenge string (which will be different every +time) and must supply the correct response in order to log in. If +your server supports this, you should talk to your system +administrator about precisely what form these challenges and +responses take. + +\S{config-ssh-ki} \q{Attempt keyboard-interactive authentication} + +\cfg{winhelp-topic}{ssh.auth.ki} + +The SSH 2 equivalent of TIS authentication is called +\q{keyboard-interactive}. It is a flexible authentication method +using an arbitrary sequence of requests and responses; so it is not +only useful for challenge/response mechanisms such as S/Key, but it +can also be used for (for example) asking the user for a new +password when the old one has expired. + +PuTTY leaves this option enabled by default, but supplies a switch +to turn it off in case you should have trouble with it. + +\S{config-ssh-agentfwd} \q{Allow agent forwarding} + +\cfg{winhelp-topic}{ssh.auth.agentfwd} + +This option allows the SSH server to open forwarded connections back +to your local copy of Pageant. If you are not running Pageant, this +option will do nothing. + +See \k{pageant} for general information on Pageant, and +\k{pageant-forward} for information on agent forwarding. Note that +there is a security risk involved with enabling this option; see +\k{pageant-security} for details. + +\S{config-ssh-changeuser} \q{Allow attempted changes of username in SSH2} + +\cfg{winhelp-topic}{ssh.auth.changeuser} + +In the SSH 1 protocol, it is impossible to change username after +failing to authenticate. So if you mis-type your username at the +PuTTY \q{login as:} prompt, you will not be able to change it except +by restarting PuTTY. + +The SSH 2 protocol \e{does} allow changes of username, in principle, +but does not make it mandatory for SSH 2 servers to accept them. In +particular, OpenSSH does not accept a change of username; once you +have sent one username, it will reject attempts to try to +authenticate as another user. (Depending on the version of OpenSSH, +it may quietly return failure for all login attempts, or it may send +an error message.) + +For this reason, PuTTY will by default not prompt you for your +username more than once, in case the server complains. If you know +your server can cope with it, you can enable the \q{Allow attempted +changes of username} option to modify PuTTY's behaviour. + +\S{config-ssh-privkey} \q{Private key file for authentication} + +\cfg{winhelp-topic}{ssh.auth.privkey} + +This box is where you enter the name of your private key file if you +are using public key authentication. See \k{pubkey} for information +about public key authentication in SSH. + +\H{config-ssh-tunnels} The Tunnels panel + +The Tunnels panel allows you to configure tunnelling of other +connection types through an SSH connection. + +\S{config-ssh-x11} X11 forwarding + +\cfg{winhelp-topic}{ssh.tunnels.x11} + +If your server lets you run X Window System applications, X11 +forwarding allows you to securely give those applications access to +a local X display on your PC. + +To enable X11 forwarding, check the \q{Enable X11 forwarding} box. +If your X display is not the primary display on your local machine +(which it almost certainly will be unless you have deliberately +arranged otherwise), you need to enter its location in the \q{X +display location} box. + +See \k{using-x-forwarding} for more information about X11 +forwarding. + +\S{config-ssh-portfwd} Port forwarding + +\cfg{winhelp-topic}{ssh.tunnels.portfwd} + +Port forwarding allows you to tunnel other types of network +connection down an SSH session. See \k{using-port-forwarding} for a +general discussion of port forwarding and how it works. + +The port forwarding section in the Tunnels panel shows a list of all +the port forwardings that PuTTY will try to set up when it connects +to the server. By default no port forwardings are set up, so this +list is empty. + +To add a port forwarding: + +\b Set one of the \q{Local} or \q{Remote} radio buttons, depending +on whether you want to forward a local port to a remote destination +(\q{Local}) or forward a remote port to a local destination +(\q{Remote}). + +\b Enter a source port number into the \q{Source port} box. For +local forwardings, PuTTY will listen on this port of your PC. For +remote forwardings, your SSH server will listen on this port of the +remote machine. Note that most servers will not allow you to listen +on port numbers less than 1024. + +\b Enter a hostname and port number separated by a colon, in the +\q{Destination} box. Connections received on the source port will be +directed to this destination. For example, to connect to a POP-3 +server, you might enter \c{popserver.example.com:110}. + +\b Click the \q{Add} button. Your forwarding details should appear +in the list box. + +To remove a port forwarding, simply select its details in the list +box, and click the \q{Remove} button. + +In the \q{Source port} box, you can also optionally enter an IP +address to listen on. Typically a Windows machine can be asked to +listen on any single IP address in the \cw{127.*.*.*} range, and all +of these are loopback addresses available only to the local machine. +So if you forward (for example) \c{127.0.0.5:79} to a remote +machine's \cw{finger} port, then you should be able to run commands +such as \c{finger fred@127.0.0.5}. This can be useful if the program +connecting to the forwarded port doesn't allow you to change the +port number it uses. This feature is available for local-to-remote +forwarded ports; SSH1 is unable to support it for remote-to-local +ports, while SSH2 can support it in theory but servers will not +necessarily cooperate. + +\S{config-ssh-portfwd-localhost} Controlling the visibility of +forwarded ports + +\cfg{winhelp-topic}{ssh.tunnels.portfwd.localhost} + +The source port for a forwarded connection usually does not accept +connections from any machine except the SSH client or server machine +itself (for local and remote forwardings respectively). There are +controls in the Tunnels panel to change this: + +\b The \q{Local ports accept connections from other hosts} option +allows you to set up local-to-remote port forwardings in such a way +that machines other than your client PC can connect to the forwarded +port. + +\b The \q{Remote ports do the same} option does the same thing for +remote-to-local port forwardings (so that machines other than the +SSH server machine can connect to the forwarded port.) Note that +this feature is only available in the SSH 2 protocol, and not all +SSH 2 servers support it (OpenSSH 3.0 does not, for example). + +\H{config-ssh-bugs} The Bugs panel + +Not all SSH servers work properly. Various existing servers have +bugs in them, which can make it impossible for a client to talk to +them unless it knows about the bug and works around it. + +Since most servers announce their software version number at the +beginning of the SSH connection, PuTTY will attempt to detect which +bugs it can expect to see in the server and automatically enable +workarounds. However, sometimes it will make mistakes; if the server +has been deliberately configured to conceal its version number, or +if the server is a version which PuTTY's bug database does not know +about, then PuTTY will not know what bugs to expect. + +The Bugs panel allows you to manually configure the bugs PuTTY +expects to see in the server. Each bug can be configured in three +states: + +\b \q{Off}: PuTTY will assume the server does not have the bug. + +\b \q{On}: PuTTY will assume the server \e{does} have the bug. + +\b \q{Auto}: PuTTY will use the server's version number announcement +to try to guess whether or not the server has the bug. + +\S{config-ssh-bug-ignore1} \q{Chokes on SSH1 ignore messages} + +\cfg{winhelp-topic}{ssh.bugs.ignore1} + +An ignore message (SSH_MSG_IGNORE) is a message in the SSH protocol +which can be sent from the client to the server, or from the server +to the client, at any time. Either side is required to ignore the +message whenever it receives it. PuTTY uses ignore messages to hide +the password packet in SSH1, so that a listener cannot tell the +length of the user's password; it also uses ignore messages for +connection keepalives (see \k{config-keepalive}). + +If this bug is detected, PuTTY will stop using ignore messages. This +means that keepalives will stop working, and PuTTY will have to fall +back to a secondary defence against SSH1 password-length +eavesdropping. See \k{config-ssh-bug-plainpw1}. If this bug is +enabled when talking to a correct server, the session will succeed, +but keepalives will not work and the session might be more +vulnerable to eavesdroppers than it could be. + +This is an SSH1-specific bug. No known SSH2 server fails to deal +with SSH2 ignore messages. + +\S{config-ssh-bug-plainpw1} \q{Refuses all SSH1 password camouflage} + +\cfg{winhelp-topic}{ssh.bugs.plainpw1} + +When talking to an SSH1 server which cannot deal with ignore +messages (see \k{config-ssh-bug-ignore1}), PuTTY will attempt to +disguise the length of the user's password by sending additional +padding \e{within} the password packet. This is technically a +violation of the SSH1 specification, and so PuTTY will only do it +when it cannot use standards-compliant ignore messages as +camouflage. In this sense, for a server to refuse to accept a padded +password packet is not really a bug, but it does make life +inconvenient if the server can also not handle ignore messages. + +If this \q{bug} is detected, PuTTY will have no choice but to send +the user's password with no form of camouflage, so that an +eavesdropping user will be easily able to find out the exact length +of the password. If this bug is enabled when talking to a correct +server, the session will succeed, but will be more vulnerable to +eavesdroppers than it could be. + +This is an SSH1-specific bug. SSH2 is secure against this type of +attack. + +\S{config-ssh-bug-rsa1} \q{Chokes on SSH1 RSA authentication} + +\cfg{winhelp-topic}{ssh.bugs.rsa1} + +Some SSH1 servers cannot deal with RSA authentication messages at +all. If Pageant is running and contains any SSH1 keys, PuTTY will +normally automatically try RSA authentication before falling back to +passwords, so these servers will crash when they see the RSA attempt. + +If this bug is detected, PuTTY will go straight to password +authentication. If this bug is enabled when talking to a correct +server, the session will succeed, but of course RSA authentication +will be impossible. + +This is an SSH1-specific bug. + +\S{config-ssh-bug-hmac2} \q{Miscomputes SSH2 HMAC keys} + +\cfg{winhelp-topic}{ssh.bugs.hmac2} + +Versions 2.3.0 and below of the SSH server software from +\cw{ssh.com} compute the keys for their HMAC message authentication +codes incorrectly. A typical symptom of this problem is that PuTTY +dies unexpectedly at the beginning of the session, saying +\q{Incorrect MAC received on packet}. + +If this bug is detected, PuTTY will compute its HMAC keys in the +same way as the buggy server, so that communication will still be +possible. If this bug is enabled when talking to a correct server, +communication will fail. + +This is an SSH2-specific bug. + +\S{config-ssh-bug-derivekey2} \q{Miscomputes SSH2 encryption keys} + +\cfg{winhelp-topic}{ssh.bugs.derivekey2} + +Versions below 2.1.0 of the SSH server software from \cw{ssh.com} +compute the keys for the session encryption incorrectly. This +problem can cause various error messages, such as \q{Incoming packet +was garbled on decryption}, or possibly even \q{Out of memory}. + +If this bug is detected, PuTTY will compute its encryption keys in +the same way as the buggy server, so that communication will still +be possible. If this bug is enabled when talking to a correct +server, communication will fail. + +This is an SSH2-specific bug. + +\S{config-ssh-bug-sig} \q{Requires padding on SSH2 RSA signatures} + +\cfg{winhelp-topic}{ssh.bugs.rsapad2} + +Versions below 3.3 of OpenSSH require SSH2 RSA signatures to be +padded with zero bytes to the same length as the RSA key modulus. +The SSH2 draft specification says that an unpadded signature MUST be +accepted, so this is a bug. A typical symptom of this problem is +that PuTTY mysteriously fails RSA authentication once in every few +hundred attempts, and falls back to passwords. + +If this bug is detected, PuTTY will pad its signatures in the way +OpenSSH expects. If this bug is enabled when talking to a correct +server, it is likely that no damage will be done, since correct +servers usually still accept padded signatures because they're used +to talking to OpenSSH. + +This is an SSH2-specific bug. + +\S{config-ssh-bug-dhgex} \q{Chokes on Diffie-Hellman group exchange} + +\cfg{winhelp-topic}{ssh.bugs.dhgex2} + +We have anecdotal evidence that some SSH servers claim to be able to +perform Diffie-Hellman group exchange, but fail to actually do so +when PuTTY tries to. If your SSH2 sessions spontaneously close +immediately after opening the PuTTY window, it might be worth +enabling the workaround for this bug to see if it helps. + +We have no hard evidence that any specific version of specific +server software reliably demonstrates this bug. Therefore, PuTTY +will never \e{assume} a server has this bug; if you want the +workaround, you need to enable it manually. + +This is an SSH2-specific bug. + +\H{config-file} Storing configuration in a file + +PuTTY does not currently support storing its configuration in a file +instead of the Registry. However, you can work around this with a +couple of batch files. + +You will need a file called (say) \c{PUTTY.BAT} which imports the +contents of a file into the Registry, then runs PuTTY, exports the +contents of the Registry back into the file, and deletes the +Registry entries. This can all be done using the Regedit command +line options, so it's all automatic. Here is what you need in +\c{PUTTY.BAT}: + +\c @ECHO OFF +\c regedit /s putty.reg +\c regedit /s puttyrnd.reg +\c start /w putty.exe +\c regedit /e puttynew.reg HKEY_CURRENT_USER\Software\SimonTatham\PuTTY +\c copy puttynew.reg putty.reg +\c del puttynew.reg +\c regedit /s puttydel.reg + +This batch file needs two auxiliary files: \c{PUTTYRND.REG} which +sets up an initial safe location for the \c{PUTTY.RND} random seed +file, and \c{PUTTYDEL.REG} which destroys everything in the Registry +once it's been successfully saved back to the file. + +Here is \c{PUTTYDEL.REG}: + +\c REGEDIT4 +\c +\c [-HKEY_CURRENT_USER\Software\SimonTatham\PuTTY] + +Here is an example \c{PUTTYRND.REG} file: + +\c REGEDIT4 +\c +\c [HKEY_CURRENT_USER\Software\SimonTatham\PuTTY] +\c "RandSeedFile"="a:\putty.rnd" + +You should replace \c{a:\\putty.rnd} with the location where you +want to store your random number data. If the aim is to carry around +PuTTY and its settings on one floppy, you probably want to store it +on the floppy.