[2019-06-28] - Found with American Fuzzy Lop - CVE-2019-13207

Stack-based buffer overflow in the dname_concatenate() function, in dname.c.

Issue can be reproduced by running:

```
nsd-checkzone all.rr zone02
```

```
=================================================================
==7395==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffcd6a9763f at pc 0x0000004dadbc bp 0x7ffcd6a97510 sp 0x7ffcd6a96cc0
WRITE of size 8 at 0x7ffcd6a9763f thread T0
    #0 0x4dadbb in __asan_memcpy (/home/fcambus/nsd/nsd-checkzone+0x4dadbb)
    #1 0x534251 in dname_concatenate /home/fcambus/nsd/dname.c:464:2
    #2 0x69e61f in yyparse /home/fcambus/nsd/./zparser.y:1024:12
    #3 0x689fd1 in zonec_read /home/fcambus/nsd/zonec.c:1623:2
    #4 0x6aedd1 in check_zone /home/fcambus/nsd/nsd-checkzone.c:61:11
    #5 0x6aea07 in main /home/fcambus/nsd/nsd-checkzone.c:127:2
    #6 0x7fa60ece6b96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310
    #7 0x41c1d9 in _start (/home/fcambus/nsd/nsd-checkzone+0x41c1d9)

Address 0x7ffcd6a9763f is located in stack of thread T0 at offset 287 in frame
    #0 0x533f8f in dname_concatenate /home/fcambus/nsd/dname.c:458

  This frame has 1 object(s):
    [32, 287) 'temp' (line 459) <== Memory access at offset 287 overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow (/home/fcambus/nsd/nsd-checkzone+0x4dadbb) in __asan_memcpy
Shadow bytes around the buggy address:
  0x10001ad4ae70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10001ad4ae80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10001ad4ae90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10001ad4aea0: 00 00 00 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00
  0x10001ad4aeb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x10001ad4aec0: 00 00 00 00 00 00 00[07]f3 f3 f3 f3 f3 f3 f3 f3
  0x10001ad4aed0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10001ad4aee0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10001ad4aef0: 00 00 00 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00
  0x10001ad4af00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10001ad4af10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==7395==ABORTING
```