[2019-08-04] - Found with American Fuzzy Lop - CVE-2019-14662

Stack-based buffer overflow in the fileio_openout() function, in src/fileio.c.

Issue can be reproduced by running:

```
brandy test02
```

```
=================================================================
==20881==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffdd1ea3f80 at pc 0x7ff66845bd82 bp 0x7ffdd1ea3e30 sp 0x7ffdd1ea35d8
WRITE of size 445 at 0x7ffdd1ea3f80 thread T0
    #0 0x7ff66845bd81 in __interceptor_memmove (/usr/lib/x86_64-linux-gnu/libasan.so.4+0x7ad81)
    #1 0x55b764d0a277 in fileio_openout src/fileio.c:502
    #2 0x55b764d05d99 in fn_openout src/functions.c:1063
    #3 0x55b764d09ba3 in exec_function src/functions.c:1777
    #4 0x55b764d24a8e in expression src/evaluate.c:3495
    #5 0x55b764cfdd20 in print_screen src/iostate.c:1428
    #6 0x55b764cfe8bb in exec_print src/iostate.c:1532
    #7 0x55b764cd0b35 in exec_statements src/statement.c:397
    #8 0x55b764cd0ead in run_program src/statement.c:436
    #9 0x55b764d32e9e in run_interpreter src/brandy.c:326
    #10 0x55b764d31f6c in main src/brandy.c:71
    #11 0x7ff667c73b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #12 0x55b764cbd799 in _start (/home/fcambus/brandy-openout/tbrandy+0x1d799)

Address 0x7ffdd1ea3f80 is located in stack of thread T0 at offset 288 in frame
    #0 0x55b764d0a132 in fileio_openout src/fileio.c:496

  This frame has 1 object(s):
    [32, 288) 'filename' <== Memory access at offset 288 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 (/usr/lib/x86_64-linux-gnu/libasan.so.4+0x7ad81) in __interceptor_memmove
Shadow bytes around the buggy address:
  0x10003a3cc7a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003a3cc7b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003a3cc7c0: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
  0x10003a3cc7d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003a3cc7e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x10003a3cc7f0:[f3]f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003a3cc800: f1 f1 f1 f1 00 00 f2 f2 f3 f3 f3 f3 00 00 00 00
  0x10003a3cc810: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003a3cc820: f1 f1 f1 f1 00 00 f2 f2 f3 f3 f3 f3 00 00 00 00
  0x10003a3cc830: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003a3cc840: 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
==20881==ABORTING
```