Oliver Pinter
2012-Jun-10  22:37 UTC
blf uses only 2^4 round for passwd encoding?! [Re: Default password hash]
http://svnweb.freebsd.org/base/head/secure/lib/libcrypt/crypt-blowfish.c?revision=231986&view=markup
145          static const char     *magic = "$2a$04$";
  146
  147                  /* Defaults */
  148          minr = 'a';
  149          logr = 4;
  150          rounds = 1 << logr;
  151
  152          /* If it starts with the magic string, then skip that */
  153          if(!strncmp(salt, magic, strlen(magic))) {
  154                  salt += strlen(magic);
  155          }
grep 04 /etc/master.passwd:
root:$2a$04$XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:0:0::0:0:XXX:/root:/bin/csh
xxxx:$2a$04$XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:100X:100X::0:0:XXXXXXXXXXXXX:/home/xxxx:/bin/tcsh
16 rounds in 2012? It is not to weak?!
On 6/8/12, Dag-Erling Sm?rgrav <des@des.no> wrote:> We still have MD5 as our default password hash, even though known-hash
> attacks against MD5 are relatively easy these days.  We've supported
> SHA256 and SHA512 for many years now, so how about making SHA512 the
> default instead of MD5, like on most Linux distributions?
>
> Index: etc/login.conf
> ==================================================================> ---
etc/login.conf      (revision 236616)
> +++ etc/login.conf      (working copy)
> @@ -23,7 +23,7 @@
>  # AND SEMANTICS'' section of getcap(3) for more escape sequences).
>
>  default:\
> -       :passwd_format=md5:\
> +       :passwd_format=sha512:\
>         :copyright=/etc/COPYRIGHT:\
>         :welcome=/etc/motd:\
>         :setenv=MAIL=/var/mail/$,BLOCKSIZE=K,FTP_PASSIVE_MODE=YES:\
>
> DES
> --
> Dag-Erling Sm?rgrav - des@des.no
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RW
2012-Jun-10  23:24 UTC
blf uses only 2^4 round for passwd encoding?! [Re: Default password hash]
On Mon, 11 Jun 2012 00:37:30 +0200 Oliver Pinter wrote:> 16 rounds in 2012? It is not to weak?!It's hard to say. Remember that blowfish was designed as a cipher not a hash. It's designed to be fast, but to still resist known plaintext attacks at the beginning of the ciphertext. It was also designed to work directly with a passphrase because there was a history of programmers abusing DES by using simple ascii passwords as keys. For these reasons initialization is deliberately expensive, effectively it already contains an element of passphrase hashing.