CINXE.COM

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>LKML: Wiktor: Re: crypting filesystems</title><link href="/css/message.css" rel="stylesheet" type="text/css" /><link href="/css/wrap.css" rel="alternate stylesheet" type="text/css" title="wrap" /><link href="/css/nowrap.css" rel="stylesheet" type="text/css" title="nowrap" /><link href="/favicon.ico" rel="shortcut icon" /><script src="/js/simple-calendar.js" type="text/javascript"></script><script src="/js/styleswitcher.js" type="text/javascript"></script><link rel="alternate" type="application/rss+xml" title="lkml.org : last 100 messages" href="/rss.php" /><link rel="alternate" type="application/rss+xml" title="lkml.org : last messages by Wiktor" href="/groupie.php?aid=28017" /><script> var _paq = window._paq = window._paq || []; /* tracker methods like "setCustomDimension" should be called before "trackPageView" */ _paq.push(["setDoNotTrack", true]); _paq.push(["disableCookies"]); _paq.push(['trackPageView']); _paq.push(['enableLinkTracking']); (function() { var u="//m.lkml.org/"; _paq.push(['setTrackerUrl', u+'matomo.php']); _paq.push(['setSiteId', '1']); var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0]; g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s); })(); </script></head><body onload="es.jasper.simpleCalendar.init();" itemscope="itemscope" itemtype="http://schema.org/BlogPosting"><table border="0" cellpadding="0" cellspacing="0"><tr><td width="180" align="center"><a href="/"><img style="border:0;width:135px;height:32px" src="/images/toprowlk.gif" alt="lkml.org" /></a></td><td width="32">聽</td><td class="nb"><div><a class="nb" href="/lkml"> [lkml]</a> 聽 <a class="nb" href="/lkml/2005"> [2005]</a> 聽 <a class="nb" href="/lkml/2005/4"> [Apr]</a> 聽 <a class="nb" href="/lkml/2005/4/4"> [4]</a> 聽 <a class="nb" href="/lkml/last100"> [last100]</a> 聽 <a href="/rss.php"><img src="/images/rss-or.gif" border="0" alt="RSS Feed" /></a></div><div>Views: <a href="#" class="nowrap" onclick="setActiveStyleSheet('wrap');return false;">[wrap]</a><a href="#" class="wrap" onclick="setActiveStyleSheet('nowrap');return false;">[no wrap]</a> 聽 <a class="nb" href="/lkml/mheaders/2005/4/4/216" onclick="this.href='/lkml/headers'+'/2005/4/4/216';">[headers]</a>聽 <a href="/lkml/bounce/2005/4/4/216">[forward]</a>聽 </div></td><td width="32">聽</td></tr><tr><td valign="top"><div class="es-jasper-simpleCalendar" baseurl="/lkml/"></div><div class="threadlist">Messages in this thread</div><ul class="threadlist"><li class="root"><a href="/lkml/2005/4/4/80">First message in thread</a></li><li><a href="/lkml/2005/4/4/80">Andreas Hartmann</a><ul><li class="origin"><a href="/lkml/2005/4/5/150">Wiktor</a><ul><li><a href="/lkml/2005/4/5/150">Felipe Alfaro Solana</a></li></ul></li></ul></li></ul></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerl.gif" width="32" height="32" alt="/" /></td><td class="c" rowspan="2" valign="top" style="padding-top: 1em"><table><tr><td><table><tr><td class="lp">Date</td><td class="rp" itemprop="datePublished">Mon, 04 Apr 2005 22:51:16 +0200</td></tr><tr><td class="lp">From</td><td class="rp" itemprop="author">Wiktor <></td></tr><tr><td class="lp">Subject</td><td class="rp" itemprop="name">Re: crypting filesystems</td></tr></table></td><td></td></tr></table><pre itemprop="articleBody">Hi,<br /><br />I'm using the following method and it seems to be working fine <br />(involving crypto-loop):<br /><br />i have normal ext3 /boot partition, where i store kernel image & initrd. <br />after lilo boots the kernel, initrd sets up /dev/loop0 to be <br />crypto-loop/blowfish for /dev/hda1 (losetup /dev/loop0 /dev/hda1 -e <br />blowfish). losetup asks for passphrase, and (if entered correctly), <br />/dev/loop0 is mounted as root filesystem (it can be done also by simple <br />mount call: mount /dev/hda1 /some-place -o rw,encryption=blowfish). for <br />encrypting more filesystems with one passphrase, you can read it in <br />shell script in non-echo-mode (if such exists, i'm not sure), and pass <br />it to mount or losetup. crypto-loop makes possible to switch encryption <br />type without modifying whole initrd.<br /><br />Regarding your questions:<br /><br /> > 1. In order to put in the passphrase just once a time at booting, I <br />put the passphrase in a gpg-crypted file (cipher AES256 and 256Bit key <br />size), which is decrypted at boot-time to /tmp (-> tmpfs) and <br />immediately removed with shred, after activating the three partitions. <br />Is it possible to see the cleartext password after this action in tmpfs?<br /><br />Disk encryption usually protects from hardware-attacks (when hacker has <br />physical access to the hardware). if you keep passphrase <br />reversible-encrypted, attacker can read it and run brute-force attack <br />using some huge-computing-capacity. is this what you want?<br /><br /> > 2. Is it possible to gain the passphrase from the active encrypted <br />partitions (because the passphrase is somewhere held in the RAM)?<br /><br />Only when attacker has root privileges. But i'm not sure if it is <br />possible to extract passphrase knowing both encrypted and not encrypted <br />data. What i mean is that usually each filesystem begins with <br />filesystem-specyfic-header, which is constant or similar to each other. <br />so, if attacker has encrypted form of this header and can estimate <br />unencryptes form, it can possibly gain the passphrase. (but therse are <br />only my ideas, i don't know how the encryptino-algorithm works).<br /><br /> > 4. Are there any master keys existing, which could be used to open <br />every encrypted filesystem?<br /><br />We all wish they are no such 'features'.<br /><br />--<br />wixor<br />May the Source be with you.<br />-<br />To unsubscribe from this list: send the line "unsubscribe linux-kernel" in<br />the body of a message to majordomo@vger.kernel.org<br />More majordomo info at <a href="http://vger.kernel.org/majordomo-info.html">http://vger.kernel.org/majordomo-info.html</a><br />Please read the FAQ at <a href="http://www.tux.org/lkml/">http://www.tux.org/lkml/</a><br /><br /></pre></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerr.gif" width="32" height="32" alt="\" /></td></tr><tr><td align="right" valign="bottom"> 聽 </td></tr><tr><td align="right" valign="bottom">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerl.gif" width="32" height="32" alt="\" /></td><td class="c">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerr.gif" width="32" height="32" alt="/" /></td></tr><tr><td align="right" valign="top" colspan="2"> 聽 </td><td class="lm">Last update: 2005-04-06 13:31 聽聽 [from the cache]<br />漏2003-2020 <a href="http://blog.jasper.es/"><span itemprop="editor">Jasper Spaans</span></a>|hosted at <a href="https://www.digitalocean.com/?refcode=9a8e99d24cf9">Digital Ocean</a> and my Meterkast|<a href="http://blog.jasper.es/categories.html#lkml-ref">Read the blog</a></td><td>聽</td></tr></table><script language="javascript" src="/js/styleswitcher.js" type="text/javascript"></script></body></html>