@c This is part of the Emacs manual.
-@c Copyright (C) 1985-1987, 1993-1995, 1997, 2000-2014
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1985-1987, 1993-1995, 1997, 2000-2015 Free Software
+@c Foundation, Inc.
@c See file emacs.texi for copying conditions.
@iftex
@chapter Miscellaneous Commands
Exit the summary buffer and return to the group buffer.
@end table
+
+@node Network Security
+@section Network Security
+@cindex network security manager
+@cindex NSM
+@cindex encryption
+@cindex SSL
+@cindex TLS
+@cindex STARTTLS
+
+Whenever Emacs establishes any network connection, it passes the
+established connection to the @dfn{Network Security Manager}
+(@acronym{NSM}). @acronym{NSM} is responsible for enforcing the
+network security under your control.
+
+@vindex network-security-level
+The @code{network-security-level} variable determines the security
+level that @acronym{NSM} enforces. If its value is @code{low}, no
+security checks are performed.
+
+If this variable is @code{medium} (which is the default), a number of
+checks will be performed. If as result @acronym{NSM} determines that
+the network connection might not be trustworthy, it will make you
+aware of that, and will ask you what to do about the network
+connection.
+
+You can decide to register a permanent security exception for an
+unverified connection, a temporary exception, or refuse the connection
+entirely.
+
+Below is a list of the checks done on the @code{medium} level.
+
+@table @asis
+
+@item unable to verify a @acronym{TLS} certificate
+If the connection is a @acronym{TLS}, @acronym{SSL} or
+@acronym{STARTTLS} connection, @acronym{NSM} will check whether
+the certificate used to establish the identity of the server we're
+connecting to can be verified.
+
+While an invalid certificate is often the cause for concern (there
+could be a Man-in-the-Middle hijacking your network connection and
+stealing your password), there may be valid reasons for going ahead
+with the connection anyway. For instance, the server may be using a
+self-signed certificate, or the certificate may have expired. It's up
+to you to determine whether it's acceptable to continue with the
+connection.
+
+@item a self-signed certificate has changed
+If you've previously accepted a self-signed certificate, but it has
+now changed, that could mean that the server has just changed the
+certificate, but it might also mean that the network connection has
+been hijacked.
+
+@item previously encrypted connection now unencrypted
+If the connection is unencrypted, but it was encrypted in previous
+sessions, this might mean that there is a proxy between you and the
+server that strips away @acronym{STARTTLS} announcements, leaving the
+connection unencrypted. This is usually very suspicious.
+
+@item talking to an unencrypted service when sending a password
+When connecting to an @acronym{IMAP} or @acronym{POP3} server, these
+should usually be encrypted, because it's common to send passwords
+over these connections. Similarly, if you're sending email via
+@acronym{SMTP} that requires a password, you usually want that
+connection to be encrypted. If the connection isn't encrypted,
+@acronym{NSM} will warn you.
+
+@end table
+
+If @code{network-security-level} is @code{high}, the following checks
+will be made, in addition to the above:
+
+@table @asis
+@item a validated certificate changes the public key
+Servers change their keys occasionally, and that is normally nothing
+to be concerned about. However, if you are worried that your network
+connections are being hijacked by agencies who have access to pliable
+Certificate Authorities which issue new certificates for third-party
+services, you may want to keep track of these changes.
+
+@item Diffie-Hellman low prime bits
+When doing the public key exchange, the number of ``prime bits''
+should be high to ensure that the channel can't be eavesdropped on by
+third parties. If this number is too low, you will be warned.
+
+@item @acronym{RC4} stream cipher
+The @acronym{RC4} stream cipher is believed to be of low quality and
+may allow eavesdropping by third parties.
+
+@item @acronym{SSL1}, @acronym{SSL2} and @acronym{SSL3}
+The protocols older than @acronym{TLS1.0} are believed to be
+vulnerable to a variety of attacks, and you may want to avoid using
+these if what you're doing requires higher security.
+@end table
+
+Finally, if @code{network-security-level} is @code{paranoid}, you will
+also be notified the first time @acronym{NSM} sees any new
+certificate. This will allow you to inspect all the certificates from
+all the connections that Emacs makes.
+
+The following additional variables can be used to control details of
+@acronym{NSM} operation:
+
+@table @code
+@item nsm-settings-file
+@vindex nsm-settings-file
+This is the file where @acronym{NSM} stores details about connections.
+It defaults to @file{~/.emacs.d/network-security.data}.
+
+@item nsm-save-host-names
+@vindex nsm-save-host-names
+By default, host names will not be saved for non-@code{STARTTLS}
+connections. Instead a host/port hash is used to identify connections.
+This means that one can't casually read the settings file to see what
+servers the user has connected to. If this variable is @code{t},
+@acronym{NSM} will also save host names in the nsm-settings-file.
+@end table
+
+
@node Document View
@section Document Viewing
@cindex DVI file
OpenDocument, and Microsoft Office documents. It provides features
such as slicing, zooming, and searching inside documents. It works by
converting the document to a set of images using the @command{gs}
-(GhostScript) command and other external tools @footnote{@code{gs} is
-a hard requirement. For DVI files, @code{dvipdf} or @code{dvipdfm} is
-needed. For OpenDocument and Microsoft Office documents, the
+(GhostScript) or @command{mudraw}/@command{pdfdraw} (MuPDF) commands
+and other external tools @footnote{For PostScript files, GhostScript
+is a hard requirement. For DVI files, @code{dvipdf} or @code{dvipdfm}
+is needed. For OpenDocument and Microsoft Office documents, the
@code{unoconv} tool is needed.}, and displaying those images.
@findex doc-view-toggle-display
(@code{doc-view-toggle-display}) toggles between DocView and the
underlying file contents.
+@findex doc-view-open-text
+ When you visit a file which would normally be handled by DocView
+mode but some requirement is not met (e.g., you operate in a terminal
+frame or emacs has no PNG support), you are queried if you want to
+view the document's contents as plain text. If you confirm, the
+buffer is put in text mode and DocView minor mode is activated. Thus,
+by typing @kbd{C-c C-c} you switch to the fallback mode. With another
+@kbd{C-c C-c} you return to DocView mode. The plain text contents can
+also be displayed from within DocView mode by typing @kbd{C-c C-t}
+(@code{doc-view-open-text}).
+
You can explicitly enable DocView mode with the command @code{M-x
doc-view-mode}. You can toggle DocView minor mode with @code{M-x
doc-view-minor-mode}.
A more convenient graphical way to specify the slice is with @kbd{s
m} (@code{doc-view-set-slice-using-mouse}), where you use the mouse to
-select the slice.
-@c ??? How does this work?
+select the slice. Simply press and hold the left mouse button at the
+upper-left corner of the region you want to have in the slice, then
+move the mouse pointer to the lower-right corner and release the
+button.
The most convenient way is to set the optimal slice by using
BoundingBox information automatically determined from the document by
-typing @kbd{s b} (@code{doc-view-set-slice-using-mouse}).
+typing @kbd{s b} (@code{doc-view-set-slice-from-bounding-box}).
@findex doc-view-reset-slice
To cancel the selected slice, type @kbd{s r}
@table @kbd
@item C-c C-c
-Send a literal @key{C-c} to the sub-shell.
+Send a literal @kbd{C-c} to the sub-shell.
@item C-c @var{char}
This is equivalent to @kbd{C-x @var{char}} in normal Emacs. For