From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.saout.de ([127.0.0.1]) by localhost (mail.saout.de [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id e5a4J4DKS0O8 for ; Thu, 16 Aug 2012 00:38:10 +0200 (CEST) Received: from v4.tansi.org (ns.km33513-03.keymachine.de [87.118.94.3]) by mail.saout.de (Postfix) with ESMTP for ; Thu, 16 Aug 2012 00:38:10 +0200 (CEST) Received: from gatewagner.dyndns.org (84-72-142-78.dclient.hispeed.ch [84.72.142.78]) by v4.tansi.org (Postfix) with ESMTPA id C17AA2065DC for ; Thu, 16 Aug 2012 00:38:10 +0200 (CEST) Date: Thu, 16 Aug 2012 00:38:10 +0200 From: Arno Wagner Message-ID: <20120815223810.GB32081@tansi.org> References: <20120814225021.GA18290@tansi.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [dm-crypt] Secret data from stdin List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: dm-crypt@saout.de On Wed, Aug 15, 2012 at 10:12:27AM -0500, Kent Yoder wrote: > Hi Arno, > > >> > >> This appears to work (no message printed, exit status 0). > >> > >> What might not be obvious is that if binary_secret contains a '\n' > >> character, input gets truncated at this point. > > > > This is documented in the man-page of the current release under > > "NOTES ON PASSPHRASE PROCESSING FOR LUKS". > > You were right - I was looking at an old git version. The new > version is clearer IMO. Ok. > >> This should probably be clearer in the man page at a > >> minimum (see patch), but I think a warning is appropriate too. > >> Secret processing that stops at \n isn't appropriate for binary > >> data. > > > > And that is the thing here. A passphrase is _not_ binary data! > > Doing > > > > "cat binary_secret | cryptsetup luksFormat /dev/loop0" > > > > is inherently wrong. What you need to do is > > > > "cat file_with_passphrase_that_could_also_be_entered_interactively > > | cryptsetup luksFormat /dev/loop0" > > I agree - just seeing a script that did the first one made me wonder > if it even worked. Well, people have to read the documentation if they want it to work right. It is really not that much for cryptsetup, just the man-page plus the FAQ. It is not like it has a 500 page documentation. If people ignore the documentation, they basically get what they deserve. This problem is worse with crypto, as lots of problems are non-visible (it works but is insecure), but anybody working with crypto needs to understand that. Those that do not _will_ make fatal mistalkes, no matter how much warning is given. Crypto is not a beginners game. > > As to your patch, I am unable to match your patch to the > > current version of the man-page. Did you do a "git pull" > > before? May also be a problem on my side, please verify: > > > >> md5sum cryptsetup.8 > > 4fd70bbd1018f95818902144499c2234 cryptsetup.8 > > Yep, I am out of date here. What do you think about a code change > that woudl print a big fat warning if non-ascii bytes are detected on > stdin? Not changing the behavior (we don't want to break people who > might be already doing this), but just a warning. See my reply to Milan. Arno -- Arno Wagner, Dr. sc. techn., Dipl. Inform., Email: arno@wagner.name GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F ---- One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision. -- Bertrand Russell