Implement a Network Security Manager

* processes.texi (Network): Mention the new :warn-unless-encrypted
parameter to `open-network-stream'.
(Network): Mention the Network Security Manager.

* net/nsm.el: New file that implements a Network Security Manager.

* net/network-stream.el (open-network-stream): Add a new
:warn-unless-encrypted parameter.
(network-stream-open-plain): Allow warning unless encrypted.
(network-stream-open-starttls): Call the Network Security Manager.
(network-stream-open-tls): Ditto.

2 files changed, 33 insertions, 0 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 0c8792af81f..5cc85aa60dc 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,9 @@
+2014-11-23  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+        * processes.texi (Network): Mention the new :warn-unless-encrypted
+        parameter to `open-network-stream'.
+        (Network): Mention the Network Security Manager.
+
 2014-11-21  Ulf Jasper  <ulf.jasper@web.de>
 
         * text.texi (Parsing HTML/XML): Document new optional parameter
diff --git a/doc/lispref/processes.texi b/doc/lispref/processes.texi
index db80f0537e0..48429e6fd93 100644
--- a/doc/lispref/processes.texi
+++ b/doc/lispref/processes.texi
@@ -2041,6 +2041,12 @@ Regular expression matching a successful @acronym{STARTTLS} negotiation.
 If non-@code{nil}, do opportunistic @acronym{STARTTLS} upgrades even if Emacs
 doesn't have built-in @acronym{TLS} support.
 
+@item :warn-unless-encrypted @var{boolean}
+If non-@code{nil}, and @code{:return-value} is also non-@code{nil},
+Emacs will warn if the connection isn't encrypted.  This is useful for
+protocols like @acronym{IMAP} and the like, where most users would
+expect the network traffic to be encrypted.
+
 @item :client-certificate @var{list-or-t}
 Either a list of the form @code{(@var{key-file} @var{cert-file})},
 naming the certificate key file and certificate file itself, or
@@ -2066,6 +2072,27 @@ The connection type: @samp{plain} or @samp{tls}.
 
 @end defun
 
+@cindex Network Security Manager
+After establishing the connection, the connection is then passed on to
+the Network Security Manager (@acronym{NSM}).  If the connection is a
+@acronym{TLS} or @acronym{STARTTLS} connection, the @acronym{NSM} will
+check whether the certificate used to establish the identity of the
+server we're connecting to can be verified.  If this can't be done,
+the @acronym{NSM} will query the user whether to proceed with the
+connection.
+
+The user is given the choice of registering a permanent security
+exception, a temporary one, or whether to refuse the connection
+entirely.
+
+If the connection is unencrypted, but it was encrypted in previous
+sessions, the user will also be notified about this.
+
+@vindex nsm-security-level
+The @code{nsm-security-level} variable determines the security level.
+If this is @code{low}, no security checks are performed.
+
+
 @node Network Servers
 @section Network Servers
 @cindex network servers