replacing MIT's ASN.1 code

[Ezra Peisach]

While I do not really have a say in any of this I see the following 
concerns:

a) There are some issues of signed/unsigned that are present in the krb5 
specs and implementations... For instance the nonce is supposed to be 
unsigned - and we are encoding as a signed integer... If the high bit is 
set - this is encoded as a five byte integer - which heimdal cannot handle.
There is one other discrepancy in signed/unsigned  handling - but I 
cannot remember what it is.  I think it might be kvno.

This means we will need to be careful in how things are encoded in terms 
of interop.

b) We are generous is decoding "incorrect" implementations for backwards 
compatibility.  For instance, see
 KRB5_GENEROUS_LR_TYPE,  KRB5_MSGTYPE_STRICT, and 
KRB5_ENCKRB5KDCREPPART_COMPAT... The generous_lr_type is a 
signed/unsigned work around...

c) We do have a  test suite for asn1 encodings/decodings - so we will 
test some edge cases - like indefinite encodings, etc. If these work w/o 
memory leaks, etc - that would help validate the ASN.1 implementation.

d) Structure compatibility w/ ABI compat... As Ken indicated some 
wrappers would be necessary... It might be nice to have a real string 
type instead
of krb5_data...  It would probably clean up some internal warnings...

Just my two cents...


Ezra