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Date: Sat, 23 Sep 2017 07:47:15 +0200
From: Salvatore Bonaccorso <carnil@...ian.org>
To: Hosein Askari <hosein.askari@....com>
Cc: luciano@...ian.org, team@...urity.debian.org,
	oss-security@...ts.openwall.com
Subject: Re: [CVE-2017-14266] tcprewrite Heap-Based Buffer Overflow

Hi

On Thu, Sep 21, 2017 at 03:05:30PM -0400, Hosein Askari wrote:
> I uploaded the file,please check out these links:
> https://files.fm/u/dkrrjjj2
> 
> http://www.filedropper.com/tcp_1
> 
> https://expirebox.com/download/bcef1a6e3cb2877cd26ef60add1ddaee.html

Thanks for providing the tcp.zip (it looks the mail did not make it to
the list, the attachment was 6.4M so maybe it was rejected).

I'm attaching for list archiving purposed the base64 encoded tcp.pcap
gzip compressed file.

Now looking at an ASAN build, on i386:

sid-i386:/tmp/source-tcpreplay/tcpreplay-3.4.4# ./src/tcprewrite --portmap=21:2121 --infile=/tmp/tcp.pcap --outfile=/tmp/output.pcap
=================================================================
==31017==ERROR: AddressSanitizer: heap-buffer-overflow on address 0xb46107ff at pc 0xb726e32a bp 0xbf82fee8 sp 0xbf82fac0
WRITE of size 65549 at 0xb46107ff thread T0
    #0 0xb726e329  (/usr/lib/i386-linux-gnu/libasan.so.4+0x74329)
    #1 0x804e3b4 in rewrite_packets src/tcprewrite.c:267
    #2 0x804da06 in main src/tcprewrite.c:140
    #3 0xb6ff2285 in __libc_start_main (/lib/i386-linux-gnu/libc.so.6+0x18285)
    #4 0x804a060  (/tmp/source-tcpreplay/tcpreplay-3.4.4/src/tcprewrite+0x804a060)

0xb46107ff is located 0 bytes to the right of 65535-byte region [0xb4600800,0xb46107ff)
allocated by thread T0 here:
    #0 0xb72d8cd4 in malloc (/usr/lib/i386-linux-gnu/libasan.so.4+0xdecd4)
    #1 0x80734ea in _our_safe_malloc src/common/utils.c:57
    #2 0x804e22c in rewrite_packets src/tcprewrite.c:248
    #3 0x804da06 in main src/tcprewrite.c:140
    #4 0xb6ff2285 in __libc_start_main (/lib/i386-linux-gnu/libc.so.6+0x18285)

SUMMARY: AddressSanitizer: heap-buffer-overflow (/usr/lib/i386-linux-gnu/libasan.so.4+0x74329)
Shadow bytes around the buggy address:
  0x368c20a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x368c20b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x368c20c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x368c20d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x368c20e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x368c20f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00[07]
  0x368c2100: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x368c2110: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x368c2120: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x368c2130: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x368c2140: 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
==31017==ABORTING

In src/tcprewrite.c:

230 /** 
231  * Main loop to rewrite packets
232  */
233 int
234 rewrite_packets(tcpedit_t *tcpedit, pcap_t *pin, pcap_dumper_t *pout)
235 {
236     tcpr_dir_t cache_result = TCPR_DIR_C2S;     /* default to primary */
237     struct pcap_pkthdr pkthdr, *pkthdr_ptr;     /* packet header */
238     const u_char *pktconst = NULL;              /* packet from libpcap */
239     u_char **pktdata = NULL;
240     static u_char *pktdata_buff;
241     static char *frag = NULL;
242     COUNTER packetnum = 0;
243     int rcode, frag_len, i;
244 
245     pkthdr_ptr = &pkthdr;
246 
247     if (pktdata_buff == NULL)
248         pktdata_buff = (u_char *)safe_malloc(MAXPACKET);
249
250     pktdata = &pktdata_buff;
251
252     if (frag == NULL)
253         frag = (char *)safe_malloc(MAXPACKET);
254 
255     /* MAIN LOOP 
256      * Keep sending while we have packets or until
257      * we've sent enough packets
258      */
259     while ((pktconst = pcap_next(pin, pkthdr_ptr)) != NULL) {
260         packetnum++;
261         dbgx(2, "packet " COUNTER_SPEC " caplen %d", packetnum, pkthdr.caplen);
262 
263         /* 
264          * copy over the packet so we can pad it out if necessary and
265          * because pcap_next() returns a const ptr
266          */
267         memcpy(*pktdata, pktconst, pkthdr.caplen);
[...]

So in line 248 MAXPACKET with originally 

#define MAXPACKET 65535         /* was 16436 linux loopback, but maybe something is bigger then   
                                   linux loopback */

and on line 267 there is a memcpy to a destination which is too small.

Earlier there was CVE-2016-6160 which was assigned for:

https://bugs.debian.org/829350

with patch enforce-maxpacket.patch, wich addresses this issue as well.

I asked MITRE if CVE-2017-14266 should be rejected, since
CVE-2016-6160 exists, or if the two should be kept, for different
types of issues. 

Regards,
Salvatore

View attachment "tcp.pcap.gz.base64" of type "text/plain" (63250 bytes)

View attachment "enforce-maxpacket.patch" of type "text/x-diff" (1419 bytes)

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