By the way here is a nice article about why general purpose hash functions are bad for hashing passwords:
http://codahale.com/how-to-safely-store-a-password/ Ilya. On Wed, Dec 29, 2010 at 9:25 AM, Bruce Dubbs <bruce.du...@gmail.com> wrote: > William Immendorf wrote: >> Let's face it: MD5, while it might be more than plain old DES, it is a >> weak algorithm to encrypt your passwords with. To give you proof, in >> 2008, researchers demonstrated that MD5 is very weak to collision >> attacks, and can create false data that appears to be trustworthy. For >> proof: >> >> http://www.kb.cert.org/vuls/id/836068 >> >> And the recommendation: Do not use MD5 for anything. This includes >> certificates, passwords, and even for verifying files. So, this means >> that it's time to switch to different algorithms. >> >> The only two choices we have right now are Blowfish, and SHA-2 (256 >> and 512). Since using Blowfish requires modifications to Glibc and >> Shadow, this means the easiest route to take would be to use SHA-2. >> >> What this means for both LFS and BLFS is: >> >> * The Shadow instructions need to have the password encryption >> changed from MD5 to SHA-512 >> * The PAM configuration files also need MD5 converted to SHA-512 >> * And all of the MD5 hashes for the packages need to be converted to >> SHA-256 hashes. >> >> The last one would require changes to all of the books in order to >> work. But belive me, with the flaws that MD5 has, you probably want to >> ditch it sooner or later. >> >> As for which list this belongs on, I belive it belongs on all of the >> -dev lists, but I'll first send it to the lfs-dev list. > > You are probably right about shadow, but the main reason for the > checksums for package downloads is to provide data integrity, not > security. The better way for ensuring a package has not been > intentionally modified is to use digital signatures. > > The chances that a package at one of the sites where we get packages is > quite small. Since we are downloading source code. The changes would > be detected fairly quickly and the fact that it happened would be all > over the net. > > For shadow, I believe the only change needed is the third sed: > > sed -i -e 's...@#encrypt_method d...@encrypt_method SHA512@' \ > -e 's@/var/spool/mail@/var/mail@' etc/login.defs > > Although PAM is in BLFS, I'm not aware of any changes to that package > that would be needed to utilize a different login encryption method. > For changing a password, I think that PAM uses whatever method currently > is in use. Let me add a caveat though. I haven't used PAM in several > years. I think it just gets in the way. > > I think this is the right list for the discussion. > > -- Bruce > -- > http://linuxfromscratch.org/mailman/listinfo/lfs-dev > FAQ: http://www.linuxfromscratch.org/faq/ > Unsubscribe: See the above information page > -- http://linuxfromscratch.org/mailman/listinfo/lfs-dev FAQ: http://www.linuxfromscratch.org/faq/ Unsubscribe: See the above information page
