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mike@××××.org wrote: |
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| 1. Encrypted root filesystem. The 2.6 Linux kernel and util-linux 2.12 |
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| will provide this using an encrypted loopback interface. A speedier |
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| compromise is to use encrypted home directories only. I maintain a PAM |
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| module, pam_mount, that mounts encrypted home directories |
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transparently. [ If |
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| you don't mind a shameless plug, there is an article about pam_mount |
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in the |
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| August Linux Journal. ] |
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| |
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| 2. Encrypted swap partition (or no swap at all). This is necessary |
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because |
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| otherwise programs could swap secrets to a plaintext disk. The 2.6 Linux |
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| kernel's encrypted loopback interface can do this. |
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| |
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| 3. An inproved authentication system. Encryption algorithms are useless |
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| if a weak key is used. Therefore it may be desireable to authenticate |
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| when booting and mounting an encrypted root filesystem (or mounting an |
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| encrypted home directory) using a physical token or other strong means. |
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Mike: |
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Thanks for this post... yeah, we've thought about it. A lot :-) |
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Until five months ago, I had been running a Gentoo laptop with an |
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encrypted filesystem for about a year. |
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I had considered things quite carefully, and decided that the only way |
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to sort-of-trust the computer was to encrypt the whole shebang: |
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encrypted root and encrypted swap. This worked just fine, very stable |
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with a 2.4.19 kernel. |
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Then I wanted to move the setup to 2.5/2.6 kernels; the init command for |
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doing so has stumped me. pivot_root simply does not work; there are |
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other ways of doing something with mount -o bind... |
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I have been able to set up, at init time, a GPG-based authentication |
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which mounts the GPG keyring from a USB storage device, a memory stick. |
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(You could also use a boot-CD.) The encryption key for the hard disk is |
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actually a random string, which is signed and kept on the external |
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device; you decrypt this key with your GPG password (which might be a |
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"bas password", given user proclivities...). This extra step provides a |
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means for key escrow, or for multiply-signed keys, so that more than one |
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person can decrypt the key (and thus the hard disk data). This is a good |
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thing, I think, if managed carefully; I don't have more than one |
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signature on my keys so far... |
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Encrypted swap is very easy, relative to the difficulties I've |
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encountered at init time, trying to bring up an encrypted root disk on 2.6. |
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Very much enjoyed the pam_mount article. But I think that for laptops, |
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you need to assume the whole disk will be read by someone, at their |
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leisure, and I really think you need whole-disk encryption to be effective. |
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As soon as I get some manner of linux 2.6 with encrypted root, I will |
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have something to write up. There is a bug in -test3 that b0rks |
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encrypted loopback; I expect there will be more distractions before this |
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is done... |
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|
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- - boyd |
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|
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Boyd Waters |
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watersb on gentoo forums |
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http://www.aoc.nrao.edu/~bwaters |
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