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   1 \versionid $Id: gs.but,v 1.8 2004/09/17 14:26:39 jacob Exp $
   2
   3 \C{gs} Getting started with PuTTY
   4
   5 This chapter gives a quick guide to the simplest types of
   6 interactive login session using PuTTY.
   7
   8 \H{gs-insecure} \ii{Starting a session}
   9
  10 When you start PuTTY, you will see a dialog box. This dialog box
  11 allows you to control everything PuTTY can do. See \k{config} for
  12 details of all the things you can control.
  13
  14 You don't usually need to change most of the configuration options.
  15 To start the simplest kind of session, all you need to do is to
  16 enter a few basic parameters.
  17
  18 In the \q{Host Name} box, enter the Internet host name of the server
  19 you want to connect to. You should have been told this by the
  20 provider of your login account.
  21
  22 Now select a login \i{protocol} to use, from the \q{Protocol}
  23 buttons. For a login session, you should select \i{Telnet},
  24 \i{Rlogin} or \i{SSH}. See \k{which-one} for a description of the
  25 differences between the three protocols, and advice on which one to
  26 use. The fourth protocol, \I{raw protocol}\e{Raw}, is not used for
  27 interactive login sessions; you would usually use this for debugging
  28 other Internet services (see \k{using-rawprot}).
  29
  30 When you change the selected protocol, the number in the \q{Port}
  31 box will change. This is normal: it happens because the various
  32 login services are usually provided on different network ports by
  33 the server machine. Most servers will use the standard port numbers,
  34 so you will not need to change the port setting. If your server
  35 provides login services on a non-standard port, your system
  36 administrator should have told you which one. (For example, many
  37 \i{MUDs} run Telnet service on a port other than 23.)
  38
  39 Once you have filled in the \q{Host Name}, \q{Protocol}, and
  40 possibly \q{Port} settings, you are ready to connect. Press the
  41 \q{Open} button at the bottom of the dialog box, and PuTTY will
  42 begin trying to connect you to the server.
  43
  44 \H{gs-hostkey} \i{Verifying the host key} (SSH only)
  45
  46 If you are not using the \i{SSH} protocol, you can skip this
  47 section.
  48
  49 If you are using SSH to connect to a server for the first time, you
  50 will probably see a message looking something like this:
  51
  52 \c The server's host key is not cached in the registry. You
  53 \c have no guarantee that the server is the computer you
  54 \c think it is.
  55 \c The server's key fingerprint is:
  56 \c ssh-rsa 1024 7b:e5:6f:a7:f4:f9:81:62:5c:e3:1f:bf:8b:57:6c:5a
  57 \c If you trust this host, hit Yes to add the key to
  58 \c PuTTY's cache and carry on connecting.
  59 \c If you want to carry on connecting just once, without
  60 \c adding the key to the cache, hit No.
  61 \c If you do not trust this host, hit Cancel to abandon the
  62 \c connection.
  63
  64 This is a feature of the SSH protocol. It is designed to protect you
  65 against a network attack known as \i\e{spoofing}: secretly
  66 redirecting your connection to a different computer, so that you
  67 send your password to the wrong machine. Using this technique, an
  68 attacker would be able to learn the password that guards your login
  69 account, and could then log in as if they were you and use the
  70 account for their own purposes.
  71
  72 To prevent this attack, each server has a unique identifying code,
  73 called a \e{host key}. These keys are created in a way that prevents
  74 one server from forging another server's key. So if you connect to a
  75 server and it sends you a different host key from the one you were
  76 expecting, PuTTY can warn you that the server may have been switched
  77 and that a spoofing attack might be in progress.
  78
  79 PuTTY records the host key for each server you connect to, in the
  80 Windows \i{Registry}. Every time you connect to a server, it checks
  81 that the host key presented by the server is the same host key as it
  82 was the last time you connected. If it is not, you will see a
  83 warning, and you will have the chance to abandon your connection
  84 before you type any private information (such as a password) into
  85 it.
  86
  87 However, when you connect to a server you have not connected to
  88 before, PuTTY has no way of telling whether the host key is the
  89 right one or not. So it gives the warning shown above, and asks you
  90 whether you want to \I{trusting host keys}trust this host key or
  91 not.
  92
  93 Whether or not to trust the host key is your choice. If you are
  94 connecting within a company network, you might feel that all the
  95 network users are on the same side and spoofing attacks are
  96 unlikely, so you might choose to trust the key without checking it.
  97 If you are connecting across a hostile network (such as the
  98 Internet), you should check with your system administrator, perhaps
  99 by telephone or in person. (Some modern servers have more than one
 100 host key. If the system administrator sends you more than one
 101 fingerprint, you should make sure the one PuTTY shows you is on the
 102 list, but it doesn't matter which one it is.)
 103
 104 \# FIXME: this is all very fine but of course in practice the world
 105 doesn't work that way. Ask the team if they have any good ideas for
 106 changes to this section!
 107
 108 \H{gs-login} \ii{Logging in}
 109
 110 After you have connected, and perhaps verified the server's host
 111 key, you will be asked to log in, probably using a \i{username} and
 112 a \i{password}. Your system administrator should have provided you
 113 with these. Enter the username and the password, and the server
 114 should grant you access and begin your session. If you have
 115 \I{mistyping a password}mistyped your password, most servers will
 116 give you several chances to get it right.
 117
 118 If you are using SSH, be careful not to type your username wrongly,
 119 because you will not have a chance to correct it after you press
 120 Return. This is an unfortunate feature of the SSH protocol: it does
 121 not allow you to make two login attempts using \i{different
 122 usernames}. If you type your username wrongly, you must close PuTTY
 123 and start again.
 124
 125 If your password is refused but you are sure you have typed it
 126 correctly, check that Caps Lock is not enabled. Many login servers,
 127 particularly Unix computers, treat upper case and lower case as
 128 different when checking your password; so if Caps Lock is on, your
 129 password will probably be refused.
 130
 131 \H{gs-session} After logging in
 132
 133 After you log in to the server, what happens next is up to the
 134 server! Most servers will print some sort of login message and then
 135 present a \i{prompt}, at which you can type commands which the
 136 server will carry out. Some servers will offer you on-line help;
 137 others might not. If you are in doubt about what to do next, consult
 138 your system administrator.
 139
 140 \H{gs-logout} \ii{Logging out}
 141
 142 When you have finished your session, you should log out by typing
 143 the server's own logout command. This might vary between servers; if
 144 in doubt, try \c{logout} or \c{exit}, or consult a manual or your
 145 system administrator. When the server processes your logout command,
 146 the PuTTY window should close itself automatically.
 147
 148 You \e{can} close a PuTTY session using the \i{Close button} in the
 149 window border, but this might confuse the server - a bit like
 150 hanging up a telephone unexpectedly in the middle of a conversation.
 151 We recommend you do not do this unless the server has stopped
 152 responding to you and you cannot close the window any other way.