AntennaHouse DMC HTMLFilter GetIndexArray Code Execution Vulnerability(CVE-2017-2798)

2017-09-18T00:00:00
ID SSV:96514
Type seebug
Reporter Root
Modified 2017-09-18T00:00:00

Description

Summary

An exploitable heap corruption vulnerability exists in the GetIndexArray functionality of AntennaHouse DMC HTMLFilter as used by MarkLogioc 8.0-6. A specially crafted XLS file can cause a heap corruption resulting in arbitrary code execution. An attacker can send/provide a malicious XLS file to trigger this vulnerability.

Tested Versions

AntennaHouse DMC HTMLFilter shipped with MarkLogic 8.0-6 fb1a22fa08c986ec3614284f4e912b0a /opt/MarkLogic/Converters/cvtofc/libdhf_rdoc.so 15b0acc464fba28335239f722a62037f /opt/MarkLogic/Converters/cvtofc/libdmc_comm.so 1eabb31236c675f9856a7d001b339334 /opt/MarkLogic/Converters/cvtofc/libdhf_rxls.so 1415cbc784f05db0e9db424636df581a /opt/MarkLogic/Converters/cvtofc/libdhf_comm.so 4ae366fbd4540dd4c750e6679eb63dd4 /opt/MarkLogic/Converters/cvtofc/libdmc_conf.so 81db1b55e18a0cb70a78410147f50b9c /opt/MarkLogic/Converters/cvtofc/libdhf_htmlif.so d716dd77c8e9ee88df435e74fad687e6 /opt/MarkLogic/Converters/cvtofc/libdhf_whtml.so e01d37392e2b2cea757a52ddb7873515 /opt/MarkLogic/Converters/cvtofc/convert

Product URLs

https://www.antennahouse.com/antenna1/

CVSSv3 Score

8.3 - CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H

Details

This vulnerability is present in the AntennaHouse DMC HTMLFilter which is used, among others, to convert XLS files to (X)HTML form.

This product is mainly used by MarkLogic for office document conversions as part of their web based document search and rendering engine. A specially crafted XLS file can lead to heap corruption and can ultimately result in remote code execution. ``` Running the XLS to HTML converter under Valgrind we can see the following result:

icewall@ubuntu:~/bugs/cvtofc_86$ valgrind ./convert config_xls/ ==38273== Memcheck, a memory error detector ==38273== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al. ==38273== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info ==38273== Command: ./convert config_xls/ ==38273== input=/home/icewall/bugs/cvtofc_86/config_xls/toconv.xls output=/home/icewall/bugs/cvtofc_86/config_xls/conv.html type=2 info.options='0' Return from GetFileInfo=0 HtmlInfo.GroupName=UTF-8 HtmlInfo.DefLangName=English HtmlInfo.bBigEndian=0 HtmlInfo.options=0 HtmlInfo.SheetId=0 HtmlInfo.SlideId=0 HtmlInfo.lpFunc=(nil) HtmlInfo.szImageFolder= ==38273== Invalid write of size 4 ==38273== at 0x4053B38: GetIndexArray (in /home/icewall/bugs/cvtofc_86/libdhf_rxls.so) ==38273== by 0x405325C: DHF_RGetObject (in /home/icewall/bugs/cvtofc_86/libdhf_rxls.so) ==38273== by 0x403979E: FilterToHtml (in /home/icewall/bugs/cvtofc_86/libdhf_htmlif.so) ==38273== by 0x4038AFB: DHF_GetHtml_V11 (in /home/icewall/bugs/cvtofc_86/libdhf_htmlif.so) ==38273== by 0x8049AF7: main (in /home/icewall/bugs/cvtofc_86/convert) ==38273== Address 0x4c5b474 is 4,820 bytes inside an unallocated block of size 6,248 in arena "client" ```

The out-of-bounds write occurs in the GetIndexArray function. Let's check the pseudocode of the GetIndexArray function and try to spot the vulnerable code: Line 1 signed int __cdecl GetIndexArray(struct_a1_1 *a1) Line 2 { Line 3 struct_v1 *blankRec; // eax@1 Line 4 int word1_1; // edx@1 Line 5 int _size; // edx@1 Line 6 _DWORD *_buffer; // eax@1 Line 7 int index; // esi@3 Line 8 Line 9 blankRec = (struct_v1 *)(a1->dword7A4 + (a1->dword7B0 << 6) - 64); Line 10 rw_1 = blankRec->rw + 1; Line 11 a1->col_1 = blankRec->col + 1; Line 12 _size = a1->col_1 * rw_1; Line 13 a1->size = _size; Line 14 _buffer = (_DWORD *)DMC_malloc(4 * _size); Line 15 a1->buffer = _buffer; Line 16 if ( !_buffer ) Line 17 return 12; Line 18 memset(a1->buffer, 0xFF, 4 * a1->size); Line 19 for ( index = 0; index < a1->count; ++index ) Line 20 a1->buffer[a1->col_1 * a1->labelSstes[index].cell.rw + (unsigned __int16)a1->labelSstes[index].cell.col] = index; Line 21 return 0; Line 22 }

There are plenty of places where integer overflows can occur, however, looking for write operations, we see the line 20 has the potential to result in an out-of-bounds write. The space for a1->buffer is allocated at line 14, based on the mulitplication of blankRec->col and blankRec->rw. The BlankRec in MS-XLS is: 2.4.20 Blank The Blank record specifies an empty cell with no formula (section 2.2.2) or value. And its location in our PoC is 0x13D1: ``` Offset 0 1 2 3 4 5 6 7 8 9 A B C D E F

000013C0 0E 00 06 00 .... 000013D0 1B 00 .. ```

Where the a1->labelSstes structure is : 2.4.149 LabelSst The LabelSst record specifies a cell that contains a string. and the location of this structure in the PoC is 0x13BE: ``` Offset 0 1 2 3 4 5 6 7 8 9 A B C D E F

000013B0 0E 00 .. 000013C0 FF FF 80 00 10 00 00 00 ˇˇÄ..... ```

In our case the result of the multiplication of a1->col_1 (0x08) and a1->labelSstes[index].cell.rw (0x0E) and adding a1->labelSstes[index].cell.col (0xFF) to it (0x1006fF) is much bigger than allocated space of a1->buffer which leads to an arbitrary out-of-bounds write.

Crash Information

``` Program received signal SIGSEGV, Segmentation fault. [----------------------------------registers-----------------------------------] EAX: 0x810bbb8 --> 0x0 EBX: 0xf7fd1c24 --> 0x1fb2c ECX: 0x810afb0 --> 0x0 EDX: 0x1006f ESI: 0x3c ('<') EDI: 0x8097d10 --> 0x0 EBP: 0xfffec8b8 --> 0xfffec8e8 --> 0xfffec918 --> 0xfffeccf8 --> 0xffffd068 --> 0x0 ESP: 0xfffec8a0 --> 0x6 EIP: 0xf7fcab38 (mov DWORD PTR [eax+edx4],esi) EFLAGS: 0x10206 (carry PARITY adjust zero sign trap INTERRUPT direction overflow) [-------------------------------------code-------------------------------------] 0xf7fcab29: imul eax,DWORD PTR [edi+0x9ec] 0xf7fcab30: add edx,eax 0xf7fcab32: mov eax,DWORD PTR [edi+0x9f4] => 0xf7fcab38: mov DWORD PTR [eax+edx4],esi 0xf7fcab3b: inc esi 0xf7fcab3c: cmp esi,DWORD PTR [edi+0x9a4] 0xf7fcab42: jl 0xf7fcab14 0xf7fcab44: mov eax,0x0 [------------------------------------stack-------------------------------------] 0000| 0xfffec8a0 --> 0x6 0004| 0xfffec8a4 --> 0xe 0008| 0xfffec8a8 --> 0x4 0012| 0xfffec8ac --> 0xf7fd1c24 --> 0x1fb2c 0016| 0xfffec8b0 --> 0x0 0020| 0xfffec8b4 --> 0x8097d10 --> 0x0 0024| 0xfffec8b8 --> 0xfffec8e8 --> 0xfffec918 --> 0xfffeccf8 --> 0xffffd068 --> 0x0 0028| 0xfffec8bc --> 0xf7fca25d (mov esi,eax) [------------------------------------------------------------------------------] Legend: code, data, rodata, value Stopped reason: SIGSEGV 0xf7fcab38 in GetIndexArray () from ./libdhf_rxls.so gdb-peda$ bt

0 0xf7fcab38 in GetIndexArray () from ./libdhf_rxls.so

1 0xf7fca25d in DHF_RGetObject () from ./libdhf_rxls.so

2 0xf7fd479f in FilterToHtml () from ./libdhf_htmlif.so

3 0xf7fd3afc in DHF_GetHtml_V11 () from ./libdhf_htmlif.so

4 0x08049af8 in main ()

5 0xf7d74af3 in libc_start_main (main=0x8049730 <main>, argc=0x2, argv=0xffffd104, init=0x8049f70 <libc_csu_init>, fini=0x8049f60 <__libc_csu_fini>, rtld_fini=0xf7feb160 <_dl_fini>,

stack_end=0xffffd0fc) at libc-start.c:287

6 0x08048ad1 in _start ()

gdb-peda$ exploitable Description: Access violation on destination operand Short description: DestAv (9/29) Hash: 6f45d697880ae583ed9077b284dc1049.6f45d697880ae583ed9077b284dc1049 Exploitability Classification: EXPLOITABLE Explanation: The target crashed on an access violation at an address matching the destination operand of the instruction. This likely indicates a write access violation, which means the attacker may control the write address and/or value. Other tags: AccessViolation (28/29) ```

Timeline

  • 2017-02-28 - Vendor Disclosure
  • 2017-05-04 - Public Release

CREDIT

  • Discovered by Marcin 'Icewall' Noga of Cisco Talos.