Date: Wed, 6 Feb 2002 19:51:45 -0800 (PST) From: Jason Stone <jason@shalott.net> To: =?iso-8859-1?B?U3TpcGhhbmUgRmlsbGlvbg==?= <cadavre01@hotmail.com> Cc: <freebsd-security@FreeBSD.ORG> Subject: Re: swap partition and security Message-ID: <20020206193226.L6370-100000@walter> In-Reply-To: <F198sxf4yp8ARf3sllN0000ff78@hotmail.com>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 > can the swap partition be used to 'spy' what happenned into a box? > > can someone with physical access to a box put the hard drive in > another computer and check into the swap to find password or email or > ...? For the most part, any part of main memory can get swapped out at any time. If a process that handles passwords or keys gets some or all of its pages swapped out, then yes, you'll probablly be able retrieve those passwords or keys from the swap disk. This is mostly only an issue with long-running processes like ssh-agent. You can easily verify this for yourself - write a four-line program that allocates a buffer, sticks a constant string in it, and then sleeps forever. Then write a program that forks a bunch of times and each copy allocates as much memory as it can. Wait until the machine starts thrashing, kill all the memory eaters, and then run strings(1) on your swap partition - the constant string from the first program will almost certainly be in there. > what can i do about it? There is a system call called mlock(2) which allows a program to lock its memory pages in core, ensuring that they won't get swapped out. Security or performance oriented programs sometimes use this. The downside is that this call can only be made by root, so your programs have to be setuid root. The gnupg port has some pretty generic code that provides secure_malloc, secure_free, etc, using mlock. Alternatively, you could arrange for your swap to be encrypted somehow (swap to a file on a cryptfs or cfs mount) or else just not use swap. -Jason ----------------------------------------------------------------------- I worry about my child and the Internet all the time, even though she's too young to have logged on yet. Here's what I worry about. I worry that 10 or 15 years from now, she will come to me and say "Daddy, where were you when they took freedom of the press away from the Internet?" -- Mike Godwin -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (FreeBSD) Comment: See https://private.idealab.com/public/jason/jason.gpg iD8DBQE8YfnVswXMWWtptckRAn/pAKCXa+jKyF0I7hsQNOaJ0PxV+9kRSgCfTE5R x9/TEI/h7f9PWVneVNT3fl0= =PiGg -----END PGP SIGNATURE----- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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