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. Will follow a feedback from upstream:
Nice find. The issue is with notes that have a zero sized name (and also no descriptor data at the end of a note section).
“The system reserves note information with no name (namesz==0) and with a zero-length name (name[0]==’\0′) but currently defines no types. All other names must have at least one non-null character.”
So we must explicitly check for namesz == 0 before using the name data in the note.
The complete ASan output:
# eu-readelf -a $FILE
==29866==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000ef9c at pc 0x7f910ac17150 bp 0x7fff92f7ed90 sp 0x7fff92f7e540
READ of size 1 at 0x60200000ef9c thread T0
#0 0x7f910ac1714f (/usr/lib/gcc/x86_64-pc-linux-gnu/6.3.0/libasan.so.3+0x4514f)
#1 0x4f63a7 in ebl_object_note_type_name /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libebl/eblobjnotetypename.c:48
#2 0x461251 in handle_notes_data /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:9372
#3 0x47209d in handle_notes /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:9455
#4 0x47209d in process_elf_file /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:916
#5 0x47ae65 in process_dwflmod /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:690
#6 0x7f910a730094 in dwfl_getmodules /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libdwfl/dwfl_getmodules.c:82
#7 0x4365f2 in process_file /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:789
#8 0x405e50 in main /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:305
#9 0x7f9108d4e78f in __libc_start_main (/lib64/libc.so.6+0x2078f)
#10 0x406cd8 in _start (/usr/bin/eu-readelf+0x406cd8)
0x60200000ef9c is located 0 bytes to the right of 12-byte region [0x60200000ef90,0x60200000ef9c)
allocated by thread T0 here:
#0 0x7f910ac94288 in malloc (/usr/lib/gcc/x86_64-pc-linux-gnu/6.3.0/libasan.so.3+0xc2288)
#1 0x7f910a10af48 in convert_data /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libelf/elf_getdata.c:166
#2 0x7f910a10af48 in __libelf_set_data_list_rdlock /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libelf/elf_getdata.c:434
#3 0x7f910a10c9ba in __elf_getdata_rdlock /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libelf/elf_getdata.c:541
#4 0x7f910a10ccae in elf_getdata /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libelf/elf_getdata.c:559
#5 0x471fe7 in handle_notes /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:9455
#6 0x471fe7 in process_elf_file /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:916
#7 0x47ae65 in process_dwflmod /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:690
#8 0x7f910a730094 in dwfl_getmodules /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/libdwfl/dwfl_getmodules.c:82
#9 0x4365f2 in process_file /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:789
#10 0x405e50 in main /tmp/portage/dev-libs/elfutils-0.168/work/elfutils-0.168/src/readelf.c:305
#11 0x7f9108d4e78f in __libc_start_main (/lib64/libc.so.6+0x2078f)
SUMMARY: AddressSanitizer: heap-buffer-overflow (/usr/lib/gcc/x86_64-pc-linux-gnu/6.3.0/libasan.so.3+0x4514f)
Shadow bytes around the buggy address:
0x0c047fff9da0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9db0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9dc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9dd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9de0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c047fff9df0: fa fa 00[04]fa fa 00 02 fa fa 00 02 fa fa 00 01
0x0c047fff9e00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e40: 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
==29866==ABORTING
Affected version:
0.168
Fixed version:
0.169 (not released atm)
Commit fix:
https://sourceware.org/ml/elfutils-devel/2017-q1/msg00111.html
Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.
CVE:
CVE-2017-7608
Reproducer:
https://github.com/asarubbo/poc/blob/master/00226-elfutils-heapoverflow-ebl_object_note_type_name
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:
elfutils: heap-based buffer overflow in ebl_object_note_type_name (eblobjnotetypename.c)