libarchive: heap-based buffer overflow in xml_data (archive_read_support_format_xar.c)

["Agostino Sarubbo" <ago () gentoo org>]

Description:
libarchive is a multi-format archive and compression library.

The complete ASan output of the issue:

# bsdtar -t -f $FILE
==13144==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x631000038800 at pc 0x7fb1c808f650 bp 0x7ffdd1b40990 
sp 0x7ffdd1b40988            
READ of size 1 at 0x631000038800 thread T0                                                                              
                             
    #0 0x7fb1c808f64f in xml_data 
/var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/libarchive/archive_read_support_format_xar.c      
    #1 0x7fb1c808f64f in expat_data_cb 
/var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/libarchive/archive_read_support_format_xar.c:3230      
                                                                                                                        
                   
    #2 0x7fb1c697c3b6 in _init /var/tmp/portage/dev-libs/expat-2.2.1/work/expat-2.2.1/lib/xmlparse.c:2960               
                             
    #3 0x7fb1c697cb9b in _init /var/tmp/portage/dev-libs/expat-2.2.1/work/expat-2.2.1/lib/xmlparse.c:2418               
                             
    #4 0x7fb1c697e988 in _init /var/tmp/portage/dev-libs/expat-2.2.1/work/expat-2.2.1/lib/xmlparse.c:4366               
                             
    #5 0x7fb1c697f137 in _init /var/tmp/portage/dev-libs/expat-2.2.1/work/expat-2.2.1/lib/xmlparse.c:4089               
                             
    #6 0x7fb1c6980fc7 in XML_ParseBuffer /var/tmp/portage/dev-libs/expat-2.2.1/work/expat-2.2.1/lib/xmlparse.c:1915     
                             
    #7 0x7fb1c807d62a in expat_read_toc 
/var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/libarchive/archive_read_support_format_xar.c:3273:8    
                                                                                                                        
                  
    #8 0x7fb1c807d62a in read_toc 
/var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/libarchive/archive_read_support_format_xar.c:584  
    #9 0x7fb1c807d62a in xar_read_header 
/var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/libarchive/archive_read_support_format_xar.c:677       
                                                                                                                        
                 
    #10 0x7fb1c7f728ed in _archive_read_next_header2 
/var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/libarchive/archive_read.c:648:7
    #11 0x7fb1c7f72590 in _archive_read_next_header 
/var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/libarchive/archive_read.c:686:8 
    #12 0x51483f in read_archive /var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/tar/read.c:260:7
    #13 0x513d89 in tar_mode_t /var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/tar/read.c:94:2
    #14 0x50eaae in main /var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/tar/bsdtar.c:858:3
    #15 0x7fb1c6ffe680 in __libc_start_main 
/var/tmp/portage/sys-libs/glibc-2.23-r4/work/glibc-2.23/csu/../csu/libc-start.c:289
    #16 0x41c628 in _init (/usr/bin/bsdtar+0x41c628)

0x631000038800 is located 0 bytes to the right of 65536-byte region [0x631000028800,0x631000038800)
allocated by thread T0 here:
    #0 0x4d1fd8 in malloc 
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-4.0.1/work/compiler-rt-4.0.1.src/lib/asan/asan_malloc_linux.cc:66
    #1 0x7fb1c69811f5 in XML_GetBuffer /var/tmp/portage/dev-libs/expat-2.2.1/work/expat-2.2.1/lib/xmlparse.c:2004

SUMMARY: AddressSanitizer: heap-buffer-overflow 
/var/tmp/portage/app-arch/libarchive-3.3.2/work/libarchive-3.3.2/libarchive/archive_read_support_format_xar.c in 
xml_data
Shadow bytes around the buggy address:
  0x0c627ffff0b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c627ffff0c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c627ffff0d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c627ffff0e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c627ffff0f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c627ffff100:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c627ffff110: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c627ffff120: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c627ffff130: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c627ffff140: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c627ffff150: 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
==13144==ABORTING

Affected version:
3.3.2

Fixed version:
N/A

Commit fix:
https://github.com/libarchive/libarchive/commit/fa7438a0ff4033e4741c807394a9af6207940d71

Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.

CVE:
CVE-2017-14166

Reproducer:
https://github.com/asarubbo/poc/blob/master/00316-libarchive-heapoverflow-archive_read_support_format_xar

Timeline:
2017-08-15: bug discovered and reported to upstream
2017-09-05: upstream released a patch
2017-09-06: blog post about the issue
2017-09-06: CVE assigned

Note:
This bug was found with American Fuzzy Lop.
This bug was identified with bare metal servers donated by Packet. This work is also supported by the Core 
Infrastructure Initiative.

Permalink:
https://blogs.gentoo.org/ago/2017/09/06/libarchive-heap-based-buffer-overflow-in-xml_data-archive_read_support_format_xar-c/

--
Agostino Sarubbo
Gentoo Linux Developer