GNU bug report logs - #24489
efaq: security risks

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Message #3 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: submit <at> debbugs.gnu.org
Subject: efaq: security risks
Date: Tue, 20 Sep 2016 18:48:06 -0400

Package: emacs
Severity: minor
Tags: security
Version: 25.1

The (very crufty) Emacs FAQ contains a section:

   "Are there any security risks in Emacs?"

The stuff about movemail and synthetic X events is archaic.

There is no mention of the more current problems:

1) installing a package runs arbitrary code
Better make sure you trust whoever gave you that package (gpg signing)
and how you got it (https), etc.

2) using an Emacs mail client to view HTML mail is a security risk if remote
content is fetched (I think it isn't by default, but this might not
apply to every client)

3) viewing remote HTML content (eg with eww or xwidgets) is likewise a
potential security risk.

Message #6 received at 24489 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 24489 <at> debbugs.gnu.org
Subject: Re: bug#24489: efaq: security risks
Date: Wed, 21 Sep 2016 00:53:13 +0200

Glenn Morris <rgm <at> gnu.org> writes:

> 2) using an Emacs mail client to view HTML mail is a security risk if remote
> content is fetched (I think it isn't by default, but this might not
> apply to every client)
>
> 3) viewing remote HTML content (eg with eww or xwidgets) is likewise a
> potential security risk.

Do you mean privacy risk?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #9 received at 24489 <at> debbugs.gnu.org (full text, mbox):

From: Richard Stallman <rms <at> gnu.org>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 24489 <at> debbugs.gnu.org
Subject: Re: bug#24489: efaq: security risks
Date: Wed, 21 Sep 2016 17:26:20 -0400

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > 2) using an Emacs mail client to view HTML mail is a security risk if remote
  > content is fetched (I think it isn't by default, but this might not
  > apply to every client)

Could you explain why you think it is a security risk?

-- 
Dr Richard Stallman
President, Free Software Foundation (gnu.org, fsf.org)
Internet Hall-of-Famer (internethalloffame.org)
Skype: No way! See stallman.org/skype.html.

Message #12 received at 24489 <at> debbugs.gnu.org (full text, mbox):

From: Ted Zlatanov <tzz <at> lifelogs.com>
To: Richard Stallman <rms <at> gnu.org>
Cc: Glenn Morris <rgm <at> gnu.org>, Lars Ingebrigtsen <larsi <at> gnus.org>,
 24489 <at> debbugs.gnu.org
Subject: Re: bug#24489: efaq: security risks
Date: Thu, 22 Sep 2016 06:56:25 -0400

On Wed, 21 Sep 2016 17:26:20 -0400 Richard Stallman <rms <at> gnu.org> wrote: 

>> 2) using an Emacs mail client to view HTML mail is a security risk if remote
>> content is fetched (I think it isn't by default, but this might not
>> apply to every client)

RS> Could you explain why you think it is a security risk?

On Wed, 21 Sep 2016 00:53:13 +0200 Lars Ingebrigtsen <larsi <at> gnus.org> wrote: 

LI> Glenn Morris <rgm <at> gnu.org> writes:

>> 2) using an Emacs mail client to view HTML mail is a security risk if remote
>> content is fetched (I think it isn't by default, but this might not
>> apply to every client)
>> 
>> 3) viewing remote HTML content (eg with eww or xwidgets) is likewise a
>> potential security risk.

LI> Do you mean privacy risk?

Images and other resources can carry constructed data and be used as an
execution backdoor through browser or library bugs. The following don't
necessarily apply to Emacs, they are just examples of the variety and
severity of these attacks, which have risen in popularity as direct code
injection has become harder:

http://arstechnica.com/security/2016/05/easily-exploited-bug-exposes-huge-number-of-sites-to-code-execution-attacks/

http://www.pcworld.com/article/2950578/security/microsoft-rushes-out-emergency-security-update-to-fix-critical-windows-flaw.html

http://fortune.com/2016/07/20/apple-security-bug-password-steal-text/

That being said, privacy risks can also become security risks and I think
the FAQ could be extended to include both.

Ted

Message #15 received at 24489 <at> debbugs.gnu.org (full text, mbox):

From: Richard Stallman <rms <at> gnu.org>
To: Ted Zlatanov <tzz <at> lifelogs.com>
Cc: rgm <at> gnu.org, larsi <at> gnus.org, 24489 <at> debbugs.gnu.org
Subject: Re: bug#24489: efaq: security risks
Date: Fri, 23 Sep 2016 16:38:56 -0400

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > Images and other resources can carry constructed data and be used as an
  > execution backdoor through browser or library bugs. The following don't
  > necessarily apply to Emacs, they are just examples of the variety and
  > severity of these attacks, which have risen in popularity as direct code
  > injection has become harder:

It is no use telling people, "Be afraid of browsing."
If we can't give any advice more specific than that, it would
be a useless annoyance.

-- 
Dr Richard Stallman
President, Free Software Foundation (gnu.org, fsf.org)
Internet Hall-of-Famer (internethalloffame.org)
Skype: No way! See stallman.org/skype.html.

Message #18 received at 24489 <at> debbugs.gnu.org (full text, mbox):

From: Ted Zlatanov <tzz <at> lifelogs.com>
To: Richard Stallman <rms <at> gnu.org>
Cc: larsi <at> gnus.org, 24489 <at> debbugs.gnu.org
Subject: Re: bug#24489: efaq: security risks
Date: Fri, 23 Sep 2016 22:45:59 -0400

On Fri, 23 Sep 2016 16:38:56 -0400 Richard Stallman <rms <at> gnu.org> wrote: 

RS> [[[ To any NSA and FBI agents reading my email: please consider    ]]]
RS> [[[ whether defending the US Constitution against all enemies,     ]]]
RS> [[[ foreign or domestic, requires you to follow Snowden's example. ]]]

>> Images and other resources can carry constructed data and be used as an
>> execution backdoor through browser or library bugs. The following don't
>> necessarily apply to Emacs, they are just examples of the variety and
>> severity of these attacks, which have risen in popularity as direct code
>> injection has become harder:

RS> It is no use telling people, "Be afraid of browsing."

The original suggestion by Glenn was to say that remote HTML content is
a potential security risk. That's a statement of fact and I gave
supporting evidence. Those risks apply to Emacs users, but I don't think
anyone proposed "be afraid" to be the message we should give.

RS> If we can't give any advice more specific than that, it would
RS> be a useless annoyance.

Certainly. The FAQ can link to external resources, for instance. I think
in the FAQ we should at least list the libraries that Emacs uses to
render remote content (SVG, XML, PNG, etc.) so the user is aware of
those dependencies and will keep them up to date.

But the method for that depends on the platform, so... do we explain in
the FAQ? Does Emacs itself warn when libraries are out of date? I don't
know.

Ted

Message #21 received at 24489 <at> debbugs.gnu.org (full text, mbox):

From: Richard Stallman <rms <at> gnu.org>
To: Ted Zlatanov <tzz <at> lifelogs.com>
Cc: larsi <at> gnus.org, 24489 <at> debbugs.gnu.org
Subject: Re: bug#24489: efaq: security risks
Date: Sun, 25 Sep 2016 13:15:16 -0400

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > RS> It is no use telling people, "Be afraid of browsing."

  > The original suggestion by Glenn was to say that remote HTML content is
  > a potential security risk.

Is there a significant difference?  I don't see it.
"Browsing" means "looking at remote HTML from web sites".


(Please don't refer to publications or works as "content".
See http://gnu.org/philosophy/words-to-avoid.html.)

    Certainly. The FAQ can link to external resources, for instance. I think
    in the FAQ we should at least list the libraries that Emacs uses to
    render remote content (SVG, XML, PNG, etc.) so the user is aware of
    those dependencies and will keep them up to date.

This will require updating, and I don't see that it will benefit
anyone.  Thus, I think it is better if we don't put this in.

-- 
Dr Richard Stallman
President, Free Software Foundation (gnu.org, fsf.org)
Internet Hall-of-Famer (internethalloffame.org)
Skype: No way! See stallman.org/skype.html.

Message #24 received at 24489 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefan <at> marxist.se>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 24489 <at> debbugs.gnu.org
Subject: Re: bug#24489: efaq: security risks
Date: Tue, 11 Aug 2020 18:38:12 -0700

Glenn Morris <rgm <at> gnu.org> writes:

> The (very crufty) Emacs FAQ contains a section:
>
>    "Are there any security risks in Emacs?"
>
> The stuff about movemail and synthetic X events is archaic.

The movemail stuff was removed in 61223a046c (Bug#37818).

What do you think we should do about synthetic X events?

> There is no mention of the more current problems:
>
> 1) installing a package runs arbitrary code
> Better make sure you trust whoever gave you that package (gpg signing)
> and how you got it (https), etc.

This was added in the same commit 61223a046c.

> 2) using an Emacs mail client to view HTML mail is a security risk if remote
> content is fetched (I think it isn't by default, but this might not
> apply to every client)

Is it important to warn about this privacy issue here?  I would expect
that any sensible Emacs MUA would disable remote fetching by default,
and document the issues with enabling it.

> 3) viewing remote HTML content (eg with eww or xwidgets) is likewise a
> potential security risk.

True, but isn't this a bit too general to be useful in the context of
the FAQ?

Best regards,
Stefan Kangas

Message #27 received at 24489 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Stefan Kangas <stefan <at> marxist.se>
Cc: Glenn Morris <rgm <at> gnu.org>, 24489 <at> debbugs.gnu.org
Subject: Re: bug#24489: efaq: security risks
Date: Sat, 29 Jan 2022 17:51:05 +0100

Stefan Kangas <stefan <at> marxist.se> writes:

>> 3) viewing remote HTML content (eg with eww or xwidgets) is likewise a
>> potential security risk.

I've now added a couple of sentences about this.

And I've removed the bit about X -- I doubt it's been relevant the last
few decades (as all X installations comes locked down).

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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