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Re: master 739593d 3/5: Make gnus-copy-file act like copy-file etc.

From: Paul Eggert
Subject: Re: master 739593d 3/5: Make gnus-copy-file act like copy-file etc.
Date: Thu, 14 Sep 2017 21:04:16 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0

Eli Zaretskii wrote:
no bot or person can reasonably
know in advance what file or directory the user will copy/rename.

Sure they can. Here's a scenario off the top of my head. A sysadmin uses Emacs to examine files, and has the bad (but all-too-common) habit of copying files to /tmp and examining the copies so that he doesn't mistakenly change the originals. A malicious user asks the sysadmin to take a look at "problems" in the user's ~/.ssh/known_hosts file. The sysadmin does this:

M-x copy-file RET ~malicious/.ssh/known_hosts RET /tmp/known_hosts RET

but it doesn't seem to work (there's no file in /tmp afterwards), so the tired sysadmin figures he mistyped the command, does the copy-file again and this time it works so he diagnoses the "problems". Because of the Emacs security bug with destination directories, the malicious user has now taken over the sysadmin's personal and private known_hosts file.

The scenario works partly because the attacker knows the habits of the victim. Such habits are often easy to discover.

One possible solution to all this is to tell ones' sysadmins "Do not use Emacs: it has too many security holes". But I'm fond of Emacs, and would rather that sysadmins could trust it to do their work.

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