Bugtraq mailing list archives
Re: /dev/random is probably not
From: Stefan Bethke <s.bethke () tallence com>
Date: Fri, 8 Jul 2005 22:27:25 +0200
Am 07.07.2005 um 02:53 schrieb Kai Howells:[ Mac OS X entropy pool being periodically saved to a file and used on boot to prime the PRNG ]
Now this raises some interesting issues - such as where is the entropy written to, and how much does this pool of entropy set the state of the RNG after bootup - ie, if an attacker had control of this file, could they influence the RNG in a deterministic fashion after forcing a reboot?
$ ls -l /private/var/db/SystemEntropyCache-rw------- 1 root wheel 20 Jul 8 21:59 /private/var/db/ SystemEntropyCache
If an attacker can manipulate this file, he probably has much more effective tools to control the system...
FreeBSD 5 uses a similiar mechanism:http://www.freebsd.org/cgi/man.cgi? query=random&apropos=0&sektion=4&manpath=FreeBSD+5.4-stable&format=html
$ sudo ls -la /var/db/entropy total 20 drwx------ 2 operator operator 512 Jul 8 22:22 . drwxr-xr-x 8 root wheel 512 Jul 8 22:21 .. -r-------- 1 operator operator 2048 Jul 8 22:22 saved-entropy.1 -r-------- 1 operator operator 2048 Jul 8 22:11 saved-entropy.2 -r-------- 1 operator operator 2048 Jul 8 22:00 saved-entropy.3 -r-------- 1 operator operator 2048 Jul 8 21:55 saved-entropy.4 -r-------- 1 operator operator 2048 Jul 8 21:44 saved-entropy.5 -r-------- 1 operator operator 2048 Jul 8 21:33 saved-entropy.6 -r-------- 1 operator operator 2048 Jul 8 21:22 saved-entropy.7 -r-------- 1 operator operator 2048 Jul 8 21:11 saved-entropy.8 -- Stefan Bethke <s.bethke () tallence com> Tallence GmbH, Baumwall 3, D-20459 Hamburg, Germany Mobile +49 170 3460140, Office +49 40 360935-0, Fax +49 40 360935-10
Current thread:
- Re: /dev/random is probably not, (continued)
- Re: /dev/random is probably not Thomas Wana (Jul 02)
- Re: /dev/random is probably not McLain Causey (Jul 04)
- Re: /dev/random is probably not Chiaki (Jul 02)
- Re: /dev/random is probably not exon (Jul 04)
- Re: /dev/random is probably not Darren Reed (Jul 05)
- Re: /dev/random is probably not devnull (Jul 06)
- Re: /dev/random is probably not Thomas (Jul 06)
- Re: /dev/random is probably not Darren Reed (Jul 06)
- Re: /dev/random is probably not Thomas (Jul 06)
- Re: /dev/random is probably not Kai Howells (Jul 08)
- Re: /dev/random is probably not Stefan Bethke (Jul 08)
- Re: /dev/random is probably not exon (Jul 04)
- Re: /dev/random is probably not Francesco Messineo (Jul 12)
- Re: /dev/random is probably not Thomas Wana (Jul 02)
- Re: /dev/random is probably not Anton Ivanov (Jul 05)
- Re: /dev/random is probably not devnull (Jul 06)