second machine's SSH port (say, \cw{foovax} port 22), and then
started a second PuTTY connecting to the forwarded port.
-In normal usage, the second PuTTY will access the host key cache
+In normal usage, the second PuTTY will access the \i{host key cache}
under the host name and port it actually connected to (i.e.
\cw{localhost} port 10022 in this example). Using the logical host
name option, however, you can configure the second PuTTY to cache
same local port number for port forwardings to lots of different
servers, you probably didn't want any particular server's host key
cached under that local port number. (For this latter case, you
-could also explicitly configure host keys in the relevant sessions;
+could instead explicitly configure host keys in the relevant sessions;
see \k{config-ssh-kex-manual-hostkeys}.)
If you just enter a host name for this option, PuTTY will cache the
problems. The SSH-1 protocol, incidentally, has even weaker integrity
protection than SSH-2 without rekeys.
+\H{config-ssh-hostkey} The Host Keys panel
+
+The Host Keys panel allows you to configure options related to SSH-2
+\i{host key management}.
+
+Host keys are used to prove the server's identity, and assure you that
+the server is not being spoofed (either by a man-in-the-middle attack
+or by completely replacing it on the network). See \k{gs-hostkey} for
+a basic introduction to host keys.
+
+This entire panel is only relevant to SSH protocol version 2; none of
+these settings affect SSH-1 at all.
+
+\S{config-ssh-hostkey-order} \ii{Host key type} selection
+
+\cfg{winhelp-topic}{ssh.hostkey.order}
+
+PuTTY supports a variety of SSH-2 host key types, and allows you to
+choose which one you prefer to use to identify the server.
+Configuration is similar to cipher selection (see
+\k{config-ssh-encryption}).
+
+PuTTY currently supports the following host key types:
+
+\b \q{Ed25519}: \i{Edwards-curve} \i{DSA} using a twisted Edwards
+curve with modulus \cw{2^255-19}.
+
+\b \q{ECDSA}: \i{elliptic curve} \i{DSA} using one of the
+NIST-standardised elliptic curves.
+
+\b \q{DSA}: straightforward \i{DSA} using modular exponentiation.
+
+\b \q{RSA}: the ordinary \i{RSA} algorithm.
+
+If PuTTY already has one or more host keys stored for the server,
+it will prefer to use one of those, even if the server has a key
+type that is higher in the preference order. You can add such a
+key to PuTTY's cache from within an existing session using the
+\q{Special Commands} menu; see \k{using-specials}.
+
+Otherwise, PuTTY will choose a key type based purely on the
+preference order you specify in the configuration.
+
+If the first key type PuTTY finds is below the \q{warn below here}
+line, you will see a warning box when you make the connection, similar
+to that for cipher selection (see \k{config-ssh-encryption}).
+
\S{config-ssh-kex-manual-hostkeys} \ii{Manually configuring host keys}
\cfg{winhelp-topic}{ssh.kex.manualhostkeys}
makes an SSH connection, then PuTTY's automated host key management is
completely bypassed: the connection will be permitted if and only if
the host key presented by the server is one of the keys listed in this
-box, and the host key store in the Registry will be neither read
-\e{nor written}.
+box, and the \I{host key cache}host key store in the Registry will be
+neither read \e{nor written}, unless you explicitly do so.
If the box is empty (as it usually is), then PuTTY's automated host
key management will work as normal.
projects / PuTTY.git / blobdiff