Add JSON support based loosely on Heimdal's heimbase code.

Add base64 support based on Heimdal's libroken base64 code.

Add new APIs:
* krb5_get_init_creds_opt_set_responder
* krb5_responder_get_challenge
* krb5_responder_list_questions
* krb5_responder_set_answer

If a caller sets a responder, it will be invoked after preauth modules
have had a chance to review their incoming padata but before they produce
outgoing padata.  The responder will be presented a set of questions with
optional challenges.  The responder should then answer all questions it knows
how to handle.  Both the answers and the challenges are printable UTF-8 and
may contain encoded, structured data specific to the question asked.

Add two new callbacks and one optional method to the clpreauth
interface.  The new method (prep_questions) allows modules to ask questions
by setting them in the responder context using one of the new callbacks
(ask_responder_question).  The other new callback (get_responder_answer) is
used by the process method to read the answers to the questions asked.

ticket: 7355 (new)

Since zapfree(str, strlen(str)) won't work for possibly-null values of
str, add a helper zapfreestr() which only calls strlen() if the string
value is non-null.

Remove KRB5_PADATA_OTP_CONFIRM pre-authentication data (padata) type
as it is marked as OBSOLETE in RFC 6560.

Implements the client side of RFC 6560. Not all features are
implemented, but it should work for the most common cases.

ticket: 7242 (new)

Add encoders and decoders for the OTP-TOKENINFO, PA-OTP-CHALLENGE,
PA-OTP-REQUEST, and PA-OTP-ENC-REQUEST types from RFC 6560.  For more
thorough testing, add support for generating test encodings using
asn1c for sample objects (currently only for the OTP types).

Don't translate '0' (no error).
Handle WSAEAFNOSUPPORT and WSAEINVAL.
Add Posix->WSA translation.
Add default translation for unrecognized errors.

[ghudson@mit.edu: Merged with master and adjusted comments.]

Signed-off-by: Kevin Wasserman <kevin.wasserman@painless-security.com>

ticket: 7228 (new)
tags: pullup