pull up r23676 from trunk

pull up r23676 from trunk

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 r23676 | ghudson | 2010-01-28 13:39:31 -0800 (Thu, 28 Jan 2010) | 17 lines

 ticket: 6650
 subject: Handle migration from pre-1.7 databases with master key kvno != 1
 target_version: 1.7.1
 tags: pullup

 krb5_dbe_lookup_mkvno assumes an mkvno of 1 for entries with no
 explicit tl_data.  We've seen at least one pre-1.7 KDB with a master
 kvno of 0, violating this assumption.  Fix this as follows:

 * krb5_dbe_lookup_mkvno outputs 0 instead of 1 if no tl_data exists.
 * A new function krb5_dbe_get_mkvno translates this 0 value to the
   minimum version number in the mkey_list.  (krb5_dbe_lookup_mkvno
   cannot do this as it doesn't take the mkey_list as a parameter.)
 * Call sites to krb5_dbe_lookup_mkvno are converted to
   krb5_dbe_get_mkvno, except for an LDAP case where it is acceptable
   to store 0 if the mkvno is unknown.

ticket: 6650

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-7@23822 dc483132-0cff-0310-8789-dd5450dbe970