Date: Tue, 02 Feb 2010 10:34:01 -0800 From: Xin LI <delphij@delphij.net> To: freebsd-security@freebsd.org Subject: Re: kern.randompid sysctl value Message-ID: <4B687019.2040008@delphij.net> In-Reply-To: <4B6807FE.30106@minibofh.org> References: <4B6807FE.30106@minibofh.org>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, Jordi, On 2010/02/02 03:09, Jordi Espasa Clofent wrote: > HI, > > 1. ¿What's the real value (in terms of security) of the random PIDs > feature? > > According to this book > > http://books.google.es/books?id=gqKwaHmXp4YC&pg=PA50&lpg=PA50&dq=random+pids+security&source=bl&ots=jimAeOQK2Q&sig=WrsBiMAxU-lUCM3pdCjtIYfmiIo&hl=es&ei=OwVoS4nwGMeOjAek5ZCvCQ&sa=X&oi=book_result&ct=result&resnum=9&ved=0CCsQ6AEwCA#v=onepage&q=random%20pids%20security&f=false > > > I understand that the random PIDs wil be a good security measure against > some exploits (books says "race conditions"). OpenBSD folks (focused on > security) have the random PIDs by defaul, so > > ¿why Freebsd don't use it by default? Hmm... My personal impression is that random PID won't help much, and management scripts may expect the PID won't be recycled too early, say, on a busy server. If PIDs are allocated sequentially, we can expect long time before one given PID will be used; with randomized allocation, we can never tell since it is expensive to have kernel tell whether the PID is being used, say, 1000 processes before. > 2. ¿What will be a real secure value for sysctl parameter? I mean > 'kern.randompid' isn't a boolean, but a large number which determines > the numeric range to generate de random PIDs. ¿1000, 10000, 100000? It's a modules number. The kernel will adjust it for you if you specify a too large number, e.g. 100k. > Thanks in advance for aclarations. > > PD. I've real this old post > http://marc.info/?l=freebsd-security&m=99495048923300&w=2. Interesting. I think Peter's reply still apply... Cheers, - -- Xin LI <delphij@delphij.net> http://www.delphij.net/ FreeBSD - The Power to Serve! Live free or die -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (FreeBSD) iQEcBAEBAgAGBQJLaHAZAAoJEATO+BI/yjfB9c4H/An0Zpxh6ZNaKO1RvYfC9dBb zTKKND9TBvFIzgIrfI7bTjdoSoFeJumpDRJ9MBrHcc5bwEfFD7yC8FFmdJKVEAna u6uvu3ZR1wsaPRy4AVFPTGWrclFA7mTdB2nehJwMbXLAWclpoydG6gm1oxFKAOYi epw3bwnjMLzkKuax84LVKtawF/0jr4fn/w3YpqZudCOYdD1LCtiFm/o0h6yhP8SN dYAEUQ8h6WpcJOsqgbTB1SK+3eoK/7upwheEt0TLkbp2XX+0I35O0mJrBvn+Fbzy VEEpSj6qoqLv6Pa3zfjM4YTc4ldgmqheCzDH57dZ7juDrveF2lOwSXG5tXtjc4o= =IMZA -----END PGP SIGNATURE-----
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