Re: [B.A.T.M.A.N.] [PATCHv5] batctl: tcpdump - parse TVLV containers

[Sven Eckelmann <sven@narfation.org>]

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On Tuesday 11 November 2014 23:56:03 Sven Eckelmann wrote:
[...]
> I've already explained this to Antonio but here again in public:
> 
>  * neither type nor version are validated
>  * the type can point in tvlv_parsers  to an invalid (non-existing) entry
>  * the version of this entry can also point to an invalid parser
>  * this is a big problem because I can crash batctl td with data packets
>    send from other people (even valid data packets with mcast tvlv)
>  * I've already experienced this problem when using nodes from a company
>    which ships this patch since a while (> 4 months)
> 
> Maybe it can be redone with some switch statements or
> (more space consuming) full tables which can handle all input data. Of
> course a check of the returned parser is still necessary inside the loops.
> 
> Kind regards,
> 	Sven

For people who require a direct experience of the crash with normal traffic
send by batman-adv:

1. compile batctl:
    CFLAGS="-g3 -fsanitize=address -fsanitize=undefined -fsanitize=leak" make
2. Start it on some interfaceL
   sudo ./batctl td  eth0
3. run on another console tcpreplay on the same interface:
   sudo tcpreplay -i eth0 v15_iv_ogm.pcapng
4. experience the crash:

10:17:28.724487 BAT 00:21:cc:b4:82:33: OGM IV via neigh 00:21:cc:b4:82:33, seq 3093200194, tq 255, ttl 50, v 15, flags [..F], length 68, tvlv_len 44
        TVLV TTv1: OGM DIFF [.] ttvn=4 vlan_num=1 entry_num=0
                VLAN ID -1, crc 0xb8d4beb4
        TVLV GWv1: down 10.0Mbps, up 2.0Mbps
=================================================================
==4213==ERROR: AddressSanitizer: global-buffer-overflow on address 0x000000639410 at pc 0x415f75 bp 0x7ffff4a02c70 sp 0x7ffff4a02c68
READ of size 8 at 0x000000639410 thread T0
    #0 0x415f74 in dump_batman_iv_ogm batctl/tcpdump.c:654
    #1 0x41710e in parse_eth_hdr batctl/tcpdump.c:825
    #2 0x4195c8 in tcpdump batctl/tcpdump.c:1118
    #3 0x403b7a in main batctl/main.c:146
    #4 0x7fd0f52dbb44 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b44)
    #5 0x4029d8 (batctl+0x4029d8)

0x000000639410 is located 0 bytes to the right of global variable 'tvlv_parsers' from 'tcpdump.c' (0x6393e0) of size 48
0x000000639410 is located 48 bytes to the left of global variable '*.Lubsan_type7' from 'tcpdump.c' (0x639440) of size 4
SUMMARY: AddressSanitizer: global-buffer-overflow batctl/tcpdump.c:654 dump_batman_iv_ogm
Shadow bytes around the buggy address:
  0x0000800bf230: 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 00 f9 f9 f9
  0x0000800bf240: f9 f9 f9 f9 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9
  0x0000800bf250: 00 00 00 f9 f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9
  0x0000800bf260: 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9
  0x0000800bf270: 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
=>0x0000800bf280: 00 00[f9]f9 f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9
  0x0000800bf290: 00 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9
  0x0000800bf2a0: f9 f9 f9 f9 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9
  0x0000800bf2b0: 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
  0x0000800bf2c0: 00 f9 f9 f9 f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9
  0x0000800bf2d0: 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9
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
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Contiguous container OOB:fc
  ASan internal:           fe
==4213==ABORTING

Kind regards,
	Sven

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