From a different point of view, part of the problem is the undefined state of the code at the "fail" label.

Execution will arrive there somehow, but the 'how' is unclear. The word "fail" implies you should reach that point only if there was an error, but that is a bad assumption in this case.

If the real answer to 'how did we get here?' was checked, then the bug could not hide in the undefined behavior. This would not allow a dangling goto to result in a false positive. A false negative will get someone's attention when their web page doesn't load.

Something like this could remove the undefined state:

      goto pass;
  fail:
    if ( err == 0 ) {
    	assert( err != 0 ); // BUG! variable must contain an error number
    	err = kSomeAppropriateErrorNumber;
    }
  pass:
    SSLFreeBuffer(&signedHashes);
    SSLFreeBuffer(&hashCtx);
    return err;