Discourage SSH-1 in documentation.

diff --git a/doc/config.but b/doc/config.but
index aab5ebca6dc7179e225a62d5efdade1b7733b543..360b502ba96c2a759ebcdba205fd86f349754db1 100644 (file)
--- a/doc/config.but
+++ b/doc/config.but
@@ -2268,16 +2268,27 @@ make the most of a low-\i{bandwidth} connection.
 
 \cfg{winhelp-topic}{ssh.protocol}
 
-This allows you to select whether you would like to use \i{SSH protocol
-version 1} or \I{SSH-2}version 2. \#{FIXME: say something about this elsewhere?}
+This allows you to select whether you would prefer to use \i{SSH protocol
+version 1} or \I{SSH-2}version 2, and whether to permit falling back
+to the other version.
 
-PuTTY will attempt to use protocol 1 if the server you connect to
-does not offer protocol 2, and vice versa.
+With the settings \q{1} and \q{2}, 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.
 
+You should normally leave this at the default, \q{2 only}. The older
+SSH-1 protocol is no longer developed, has many known cryptographic
+weaknesses, and is generally not considered to be secure. If you
+permit use of SSH-1 by selecting \q{2} instead of \q{2 only}, an
+active attacker can force downgrade to SSH-1 even if the server
+you're connecting to supports SSH-2.
+
+PuTTY's protocol 1 implementation is provided mainly for
+compatibility, and is no longer being enhanced.
+
 \S{config-ssh-sharing} Sharing an SSH connection between PuTTY tools
 
 \cfg{winhelp-topic}{ssh.sharing}

diff --git a/doc/faq.but b/doc/faq.but
index 8bf1f32d6654264574f6f2b39c8ba56754ef2126..06448cb81b8680e32606d2b117a9f14b7c13273a 100644 (file)
--- a/doc/faq.but
+++ b/doc/faq.but
@@ -63,6 +63,9 @@ files into PuTTY's format.
 
 Yes. SSH-1 support has always been available in PuTTY.
 
+However, the SSH-1 protocol has many weaknesses and is no longer
+considered secure; it should be avoided if at all possible.
+
 \S{faq-localecho}{Question} Does PuTTY support \i{local echo}?
 
 Yes. Version 0.52 has proper support for local echo.