[krbdev.mit.edu #2024] overwriting memory in krb5_aname_to_localname

[""Nebergall@MIT.EDU]

759:  cp  is first set to point at the strings null terminator of the string
761:  isspace space is run on it in a loop.  (The null terminator is not
considered white space, so this does nothing).
762:  cp is incremented to one past the null terminator
763:  Memory after the null terminator is set to an additional null
terminator  (ERROR!)

src/lib/krb5/os/an_to_ln.c

755                     for (nvalid=0; mapping_values[nvalid]; nvalid++);
756
757                     /* Just use the last one. */
758                     /* Trim the value. */
759                     cp = &mapping_values[nvalid-1]
760                         [strlen(mapping_values[nvalid-1])];
761                     while (isspace((int) (*cp))) cp--;
762                     cp++;
763                     *cp = '\0';

>From Man page provided in RH 7.3

isspace()
              checks for white-space characters.  In the "C"  and
              "POSIX"   locales,   these  are:  space,  form-feed
              ('\f'), newline  ('\n'),  carriage  return  ('\r'),
              horizontal tab ('\t'), and vertical tab ('\v').