An issue was discovered in gpac before 1.0.1. A NULL pointer dereference exists in the function dump_isom_sdp located in filedump.c. It allows an attacker to cause Denial of Service.
## System info

Ubuntu x86_64, gcc (Ubuntu 5.5.0-12ubuntu1), MP4Box (latest master [2aa266](https://github.com/gpac/gpac/commit/2aa266dfaab6aaad9f9f4f216ad7d1e62adc7fa0))

## Configure

CFLAGS="-g -fsanitize=address" LDFLAGS="-fsanitize=address" ./configure --static-mp4box

## Command line

./bin/gcc/MP4Box -sdp -ttxt -2 -dump-chap-ogg -dump-cover -drtp -bt -out /dev/null @@

## Output

```
Scene loaded - dumping root scene
Exporting MPEG-4 AAC Audio - SampleRate 44100 2 channels 16 bits per sample
Segmentation fault (core dumped)
```

## AddressSanitizer output

```
ASAN:SIGSEGV
=================================================================
==31981==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f1269c005a1 bp 0x000000000000 sp 0x7fffad3ba678 T0)
    #0 0x7f1269c005a0  (/lib/x86_64-linux-gnu/libc.so.6+0x18e5a0)
    #1 0x7f1269af1204 in fputs (/lib/x86_64-linux-gnu/libc.so.6+0x7f204)
    #2 0x55eb9834073a in dump_isom_sdp /home/seviezhou/gpac/applications/mp4box/filedump.c:1627
    #3 0x55eb98311eb3 in mp4boxMain /home/seviezhou/gpac/applications/mp4box/main.c:5533
    #4 0x7f1269a93b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #5 0x55eb982eff09 in _start (/home/seviezhou/gpac/bin/gcc/MP4Box+0x27ff09)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV ??:0 ??
==31981==ABORTING
```

## POC

[SEGV-dump_isom_sdp-filedump-1627.zip](https://github.com/gpac/gpac/files/5039113/SEGV-dump_isom_sdp-filedump-1627.zip)

A Segmentation fault in filedump.c:1627
This is a GitHub Issue
repo:gpac
owner:gpac
Title : A Segmentation fault in filedump.c:1627
Issue date:

--- start body ---
## System info

Ubuntu x86_64, gcc (Ubuntu 5.5.0-12ubuntu1), MP4Box (latest master [2aa266](https://github.com/gpac/gpac/commit/2aa266dfaab6aaad9f9f4f216ad7d1e62adc7fa0))

## Configure

CFLAGS="-g -fsanitize=address" LDFLAGS="-fsanitize=address" ./configure --static-mp4box

## Command line

./bin/gcc/MP4Box -sdp -ttxt -2 -dump-chap-ogg -dump-cover -drtp -bt -out /dev/null @@

## Output

```
Scene loaded - dumping root scene
Exporting MPEG-4 AAC Audio - SampleRate 44100 2 channels 16 bits per sample
Segmentation fault (core dumped)
```

## AddressSanitizer output

```
ASAN:SIGSEGV
=================================================================
==31981==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f1269c005a1 bp 0x000000000000 sp 0x7fffad3ba678 T0)
    #0 0x7f1269c005a0  (/lib/x86_64-linux-gnu/libc.so.6+0x18e5a0)
    #1 0x7f1269af1204 in fputs (/lib/x86_64-linux-gnu/libc.so.6+0x7f204)
    #2 0x55eb9834073a in dump_isom_sdp /home/seviezhou/gpac/applications/mp4box/filedump.c:1627
    #3 0x55eb98311eb3 in mp4boxMain /home/seviezhou/gpac/applications/mp4box/main.c:5533
    #4 0x7f1269a93b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #5 0x55eb982eff09 in _start (/home/seviezhou/gpac/bin/gcc/MP4Box+0x27ff09)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV ??:0 ??
==31981==ABORTING
```

## POC

[SEGV-dump_isom_sdp-filedump-1627.zip](https://github.com/gpac/gpac/files/5039113/SEGV-dump_isom_sdp-filedump-1627.zip)

--- end body ---
