Update HMAC to fail when null value is passed to out parameter

[kexgaber]

Issues:

CryptoAlg-2522

Description of changes:

Currently, NULL passed as the value of out can result in a segmentation fault. This change adds checks to the HMAC one-shot API and HMAC_final function to handle scenarios where NULL is passed as a value to the out parameter to return from the functions and prevent further computation.

Testing:

Added additional test case in crypto/hmac_extra/hmac_test.cc to verify the behavior when NULL is passed as a value to out in both functions.

Call-outs:

• OpenSSL supports this differently by allowing the computation to occur but allocating a throw-away array OpenSSL implementation

• We should also evaluate if this change should be back-ported to the FIPS branches

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.21%. Comparing base (4368aaa) to head (6d821dd).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1662      +/-   ##
==========================================
- Coverage   78.22%   78.21%   -0.01%     
==========================================
  Files         566      566              
  Lines       95165    95176      +11     
  Branches    13661    13663       +2     
==========================================
+ Hits        74442    74444       +2     
- Misses      20127    20137      +10     
+ Partials      596      595       -1     

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