Date: Sun, 5 Nov 2017 19:03:07 -0700 From: Kurt Seifried <kseifried@...hat.com> To: oss-security <oss-security@...ts.openwall.com> Subject: Re: Fw: Security risk of vim swap files Also you're all still ignoring umask =(. Please, when you create a new file, check the umask and subtract it to make sure you're abiding by the user's wishes. On Sun, Nov 5, 2017 at 11:19 AM, Scott Court <z5t1@...1.com> wrote: > Just want to point out that even if we do set 0600 permissions on all > .swp files, it still may allow for a form of the attack Hanno originally > pointed out if vim is ever run as the httpd user. In reality, this is > far less likely to occur but it's still worth pointing out. > > Storing the .swp files in a separate directory prevents this from > potentially being a problem as well. However, universally setting the > .swp files to 0600 is probably a better solution than that patch > (https://github.com/vim/vim/releases/tag/v8.0.1263). > > > On 11/05/2017 12:59 PM, Solar Designer wrote: > > On Sun, Nov 05, 2017 at 06:17:04PM +0100, Christian Brabandt wrote: > >> On Fr, 03 Nov 2017, Jakub Wilk wrote: > >> > >>> In general, what vim does (copying mode bits) in not enough to ensure > that > >>> the swapfile is readable only by the users who had access to the > original > >>> file. It would have to copy also group ownership and ACLs. > >> I think patch https://github.com/vim/vim/releases/tag/v8.0.1263 fixes > >> the group ownership problem. > > That's some effort and code complexity for a fix that is not even trying > > to address the problem Hanno pointed out. :-( What we really need is > > simply forcing the permissions to 0600 no matter what. I do notice that, > > non-surprisingly, Bram said: > > > > | Why would a web server expose and serve such a file? That clearly is > > | the problem, not that Vim happens to create swap files (and undo and > > | backup files, depending on your configuration). > > | > > | You probably also create new files and copies of files that should not > > | be served. If you care about security, the web server must always use > > | whitelisting, only serve files that were intentionally made public. > > > > This makes sense, yet Vim can and should also do its part to make things > > safer when that does not conflict with its other goals nor introduce > > complexity. Simply using mode 0600 is a win-win: addresses the problem > > Hanno reported for the common special case of web server running as a > > different user than the file owner, does not break any functionality, > > and makes Vim's code simpler. > > > > Yes, let's also force 0600 for "undo and backup files", please. > > > > Even without a web server or whatever other external interaction > > aspects, copying the original file's permissions and/or obeying umask is > > just wrong in this case because those files are created implicitly, > > often without the user's intent and knowledge, and because they might > > stay around for longer than the original file does. > > > > Alexander > > > -- Kurt Seifried -- Red Hat -- Product Security -- Cloud PGP A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993 Red Hat Product Security contact: secalert@...hat.com
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