addprinc -randkey broken in 1.7?

Greg Hudson ghudson at MIT.EDU
Wed Sep 16 23:29:12 EDT 2009

On Wed, 2009-09-16 at 18:39 -0400, Mike Friedman wrote:
> OK, so maybe I'm misinterpreting the code.  But the fact is that I add 
> host principals with -randkey all the time with no problem.  I've been 
> doing this for several releases up to and including our current 1.6.3. 
> We may go to 1.7 soon, so possibly something's changed there, but in the 
> meantime, could someone clarify all this?

Here's the history of the temporary password used for addprinc -randkey:

  * Through krb5 1.1, it was "dummy", which would fail any password
policy requiring multiple character classes or more than five
characters.  This might explain Russ's experiences.

  * In r9210 (October 1996), it was changed to a 255 byte string
containing all possible nonzero byte values, which would pass any policy
with a reasonable minimum length.  I believe this change first hit the
field in krb5 1.2.

  * In r20650 (August 2008), it was changed to 255 weakly random
lowercase letters, which would fail any policy requiring multiple
character classes.  According to the commit log, this was to avoid a
problem where the RC4 string-to-key function requires the password to be
valid UTF-8.  This change first hit the field in krb5 1.7.

It would be trivial to fix this regression by picking a temporary
password which is valid UTF-8 but still contains all five character
classes.  I think that will be the best minimal fix for 1.7.1.  For the
trunk, time permitting, I will review and apply Marcus Watts's patch,
which is a more elegant solution.

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