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Date: Mon, 10 Apr 2017 07:25:59 +0000
From: "Agostino Sarubbo" <ago@...too.org>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
Subject: elfutils: heap-based buffer overflow in handle_gnu_hash (readelf.c)

Description:
elfutils is a set of libraries/utilities to handle ELF objects (drop in replacement for libelf).

A fuzz on eu-readelf showed an heap overflow.

The complete ASan output:

# eu-readelf -a $FILE
==1855==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x611000009ffc at pc 0x000000421a8c bp 0x7ffef67082e0 sp 0x7ffef67082d8
READ of size 4 at 0x611000009ffc thread T0
    #0 0x421a8b in handle_gnu_hash /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:3268
    #1 0x421a8b in handle_hash /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:3346
    #2 0x4680f7 in process_elf_file /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:898
    #3 0x47ae65 in process_dwflmod /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:690
    #4 0x7f4bae746094 in dwfl_getmodules /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libdwfl/dwfl_getmodules.c:82
    #5 0x4365f2 in process_file /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:789
    #6 0x405e50 in main /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:305
    #7 0x7f4bacd6478f in __libc_start_main (/lib64/libc.so.6+0x2078f)
    #8 0x406cd8 in _start (/usr/bin/eu-readelf+0x406cd8)

0x611000009ffc is located 0 bytes to the right of 252-byte region [0x611000009f00,0x611000009ffc)
allocated by thread T0 here:
    #0 0x7f4baecaa288 in malloc (/usr/lib/gcc/x86_64-pc-linux-gnu/6.3.0/libasan.so.3+0xc2288)
    #1 0x7f4bae120f48 in convert_data /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libelf/elf_getdata.c:166
    #2 0x7f4bae120f48 in __libelf_set_data_list_rdlock /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libelf/elf_getdata.c:434
    #3 0x7f4bae1229ba in __elf_getdata_rdlock /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libelf/elf_getdata.c:541
    #4 0x7f4bae122cae in elf_getdata /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libelf/elf_getdata.c:559
    #5 0x41f100 in handle_gnu_hash /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:3206
    #6 0x41f100 in handle_hash /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:3346
    #7 0x4680f7 in process_elf_file /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:898
    #8 0x47ae65 in process_dwflmod /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:690
    #9 0x7f4bae746094 in dwfl_getmodules /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libdwfl/dwfl_getmodules.c:82
    #10 0x4365f2 in process_file /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:789
    #11 0x405e50 in main /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:305
    #12 0x7f4bacd6478f in __libc_start_main (/lib64/libc.so.6+0x2078f)

SUMMARY: AddressSanitizer: heap-buffer-overflow /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:3268 in handle_gnu_hash
Shadow bytes around the buggy address:
  0x0c227fff93a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff93b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff93c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff93d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff93e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c227fff93f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00[04]
  0x0c227fff9400: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff9410: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff9420: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff9430: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff9440: 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
  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
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==1855==ABORTING

Affected version:
0.168

Fixed version:
0.169 (not released atm)

Commit fix:
https://sourceware.org/ml/elfutils-devel/2017-q1/msg00109.html

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

CVE:
CVE-2017-7607

Reproducer:
https://github.com/asarubbo/poc/blob/master/00225-elfutils-heapoverflow-handle_gnu_hash

Timeline:
2017-03-24: bug discovered and reported to upstream
2017-04-04: blog post about the issue
2017-04-09: CVE assigned

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/04/03/elfutils-heap-based-buffer-overflow-in-handle_gnu_hash-readelf-c/

--
Agostino Sarubbo
Gentoo Linux Developer


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