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Document 'trusted-content

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* doc/emacs/misc.texi (Host Security): Document 'trusted-content'.

* lisp/files.el (trusted-content): Doc fix.

* etc/NEWS: Mark its entry as "documented".
This commit is contained in:
Eli Zaretskii 2024-12-18 19:57:13 +02:00
parent c6ce11b2a4
commit 8a0c9c234f
3 changed files with 35 additions and 1 deletions
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33
doc/emacs/misc.texi
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@ -277,6 +277,39 @@ trusted and the default checking for these variables is irritating,
you can set @code{enable-local-variables} to @code{:all}. @xref{Safe
File Variables}.
@cindex trusted files and directories
Loading a file of Emacs Lisp code with @code{load-file} or
@code{load-library} (@pxref{Lisp Libraries}) can execute some of the
Lisp code in the file being loaded, so you should only load Lisp files
whose source you trust. However, some Emacs features can in certain
situations execute Lisp code even without your explicit command or
request. For example, Flymake, the on-the-fly syntax checker for Emacs
(@pxref{Top,,, flymake, GNU Flymake}), if it is enabled, can
automatically execute some of the code in a Lisp file you visit as part
of its syntax-checking job. Similarly, some completion commands
(@pxref{Completion}) in buffers visiting Lisp files sometimes need to
expand Lisp macros for best results. In these cases, just visiting a
Lisp file and performing some editing in it could trigger execution of
Lisp code. If the visited file came from an untrusted source, it could
include dangerous or even malicious code that Emacs would execute in
those situations.
To protect against this, Emacs disables execution of Lisp code by
Flymake, completion, and some other features, unless the visited file is
@dfn{trusted}. It is up to you to specify which files on your system
should be trusted, by customizing the user option
@code{trusted-content}.
@defopt trusted-content
The value of this option is @code{nil} by default, which means no file
is trusted. You can customize the variable to be a list of one or more
names of trusted files and directories. A file name that ends in a
slash @file{/} is interpreted as a directory, which means all its files
and subdirectories are also trusted. A special value @code{:all} means
@emph{all} the files and directories on your system should be trusted;
@strong{this is not recommended}, as it opens a gaping security hole.
@end defopt
@xref{Security Considerations,,, elisp, The Emacs Lisp Reference
Manual}, for more information about security considerations when using
Emacs as part of a larger application.

1
etc/NEWS
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@ -199,6 +199,7 @@ see the variable 'url-request-extra-headers'.
* Changes in Emacs 30.1
+++
** New user option 'trusted-content' to allow potentially dangerous features.
This variable lists those files and directories whose content Emacs should
consider as sufficiently trusted to run any part of the code contained

2
lisp/files.el
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@ -725,7 +725,7 @@ Each element of the list should be a string:
- If it ends in \"/\", it is considered as a directory name and means that
Emacs should trust all the files whose name has this directory as a prefix.
- else it is considered as a file name.
Use abbreviated file names. For example, an entry \"~/mycode\" means
Use abbreviated file names. For example, an entry \"~/mycode/\" means
that Emacs will trust all the files in your directory \"mycode\".
This variable can also be set to `:all', in which case Emacs will trust
all files, which opens a gaping security hole."