[Bug] heap-overflow in get_ipv6_next

[kdsjZh]

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Describe the bug There is a heap-overflow bug found in get_ipv6_next, can be triggered via tcprewrite + ASan

To Reproduce Steps to reproduce the behavior:

1. export CC=clang && export CFLAGS="-fsanitize=address -g"
2. ./autogen.sh && ./configure --disable-shared --disable-local-libopts && make clean && make -j8

3. ./src/tcprewrite -o /dev/null -i POC output:

   
   Warning: tcprewrite/crash.1 was captured using a snaplen of 64 bytes.  This may mean you have truncated packets.
   =================================================================
   ==7944==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7fc3f2e48820 at pc 0x000000535bca bp 0x7ffe1d7fcb70 sp 0x7ffe1d7fcb68
   READ of size 4 at 0x7fc3f2e48820 thread T0
   #0 0x535bc9 in get_ipv6_next /benchmark/vulnerable/tcpreplay/src/common/get.c:679:14
   #1 0x53598e in get_layer4_v6 /benchmark/vulnerable/tcpreplay/src/common/get.c:626:22
   #2 0x4f9bc4 in tcpedit_packet /benchmark/vulnerable/tcpreplay/src/tcpedit/tcpedit.c:198:13
   #3 0x4f80fc in rewrite_packets /benchmark/vulnerable/tcpreplay/src/tcprewrite.c:304:22
   #4 0x4f7418 in main /benchmark/vulnerable/tcpreplay/src/tcprewrite.c:145:9
   
   #5 0x7fc3f175dbf6 in __libc_start_main /build/glibc-S9d2JN/glibc-2.27/csu/../csu/libc-start.c:310
   #6 0x41c2c9 in _start (/benchmark/vulnerable/tcpreplay/src/tcprewrite+0x41c2c9)

0x7fc3f2e48820 is located 10 bytes to the right of 262166-byte region [0x7fc3f2e08800,0x7fc3f2e48816) allocated by thread T0 here:

0 0x4aec90 in malloc /home/nipc/workspace/install/llvm-project/llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:145

#1 0x536c1f in _our_safe_malloc /benchmark/vulnerable/tcpreplay/src/common/utils.c:50:16
#2 0x4f7e02 in rewrite_packets /benchmark/vulnerable/tcpreplay/src/tcprewrite.c:267:34
#3 0x4f7418 in main /benchmark/vulnerable/tcpreplay/src/tcprewrite.c:145:9
#4 0x7fc3f175dbf6 in __libc_start_main /build/glibc-S9d2JN/glibc-2.27/csu/../csu/libc-start.c:310

SUMMARY: AddressSanitizer: heap-buffer-overflow /benchmark/vulnerable/tcpreplay/src/common/get.c:679:14 in get_ipv6_next Shadow bytes around the buggy address: 0x0ff8fe5c10b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0ff8fe5c10c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0ff8fe5c10d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0ff8fe5c10e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0ff8fe5c10f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 =>0x0ff8fe5c1100: 00 00 06 fa[fa]fa fa fa fa fa fa fa fa fa fa fa 0x0ff8fe5c1110: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0ff8fe5c1120: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0ff8fe5c1130: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0ff8fe5c1140: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0ff8fe5c1150: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 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 Shadow gap: cc ==7944==ABORTING

**Screenshots**
![image](https://user-images.githubusercontent.com/35988108/156727541-af143fc6-1e64-49fc-8cc3-8865111df744.png)

**System (please complete the following information):**
 - OS: Ubuntu
 - OS version : can be reproduced in 18.04/20.04
 - clang version: 12.0.1 (release/12.x)
 - Tcpreplay Version : latest commit 09f07748dcabe3d58961f123f31dd0f75198a389

**Credit**
Han Zheng
[NCNIPC of China](http://www.nipc.org.cn)
[Hexhive](http://hexhive.epfl.ch/)

**POC**
[POC2.zip](https://github.com/appneta/tcpreplay/files/8184264/POC2.zip)

[fklassen]

Improved overflow protection added in PR #740