pull up r24191 from trunk

pull up r24191 from trunk

 ------------------------------------------------------------------------
 r24191 | ghudson | 2010-07-19 01:01:45 -0400 (Mon, 19 Jul 2010) | 15 lines

 ticket: 6751
 subject: Allow Microsoft HMAC-MD5 checksum types to use non-RC4 keys
 target_version: 1.8.3
 tags: pullup

 In PAC signatures, the hmac-md5 checksum type can be used with AES
 keys.  Make this work by removing the enc field from the hmac-md5 and
 md5-hmac checksum types, and adding a check in
 krb5int_hmacmd5_checksum() for a null key or a key which is longer
 than the hash block size (64 bytes for MD5).  The checksum algorithm
 only uses the key bits; it does invoke the cipher.

 The checksum type names are kind of wrong, but we'll leave them alone
 for compatibility.  The descriptions are updated.

ticket: 6751
version_fixed: 1.8.3
status: resolved

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-8@24198 dc483132-0cff-0310-8789-dd5450dbe970