TDE base libraries and programs
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/*
Copyright 2010 Adam Marchetti
Copyright 2011-2013 Timothy Pearson <kb9vqf@pearsoncomputing.net>
This file is part of tsak, the TDE Secure Attention Key daemon
tsak 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 3
of the License, or (at your option) any later version.
tsak 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.
You should have received a copy of the GNU General Public
License along with tsak. If not, see http://www.gnu.org/licenses/.
*/
#include <stdio.h>
#include <stdlib.h>
#include <exception>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <dirent.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/select.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <termios.h>
#include <signal.h>
extern "C" {
#include <libudev.h>
}
#include <libgen.h>
using namespace std;
#define FIFO_DIR "/tmp/tdesocket-global"
#define FIFO_FILE_OUT "/tmp/tdesocket-global/tsak"
#define FIFO_LOCKFILE_OUT "/tmp/tdesocket-global/tsak.lock"
// WARNING
// MAX_KEYBOARDS must be greater than or equal to MAX_INPUT_NODE
#define MAX_KEYBOARDS 128
#define MAX_INPUT_NODE 128
#define TestBit(bit, array) (array[(bit) / 8] & (1 << ((bit) % 8)))
typedef unsigned char byte;
bool mPipeOpen_out = false;
int mPipe_fd_out = -1;
int mPipe_lockfd_out = -1;
char filename[32];
char key_bitmask[(KEY_MAX + 7) / 8];
struct sigaction usr_action;
sigset_t block_mask;
int keyboard_fd_num;
int keyboard_fds[MAX_KEYBOARDS];
int child_pids[MAX_KEYBOARDS];
int child_led_pids[MAX_KEYBOARDS];
int current_keyboard = -1;
int devout[MAX_KEYBOARDS];
const char *keycode[256] =
{
"", "<esc>", "1", "2", "3", "4", "5", "6", "7", "8",
"9", "0", "", "=", "<backspace>", "<tab>", "q", "w", "e", "r",
"t", "y", "u", "i", "o", "p", "[", "]", "\n", "<control>",
"a", "s", "d", "f", "g", "h", "j", "k", "l", ";",
"'", "", "<shift>", "\\", "z", "x", "c", "v", "b", "n",
"m", ",", ".", "/", "<shift>", "", "<alt>", " ", "<capslock>",
"<f1>", "<f2>", "<f3>", "<f4>", "<f5>", "<f6>", "<f7>", "<f8>", "<f9>", "<f10>",
"<numlock>", "<scrolllock>", "", "", "", "", "", "", "", "",
"", "", "\\", "f11", "f12", "", "", "", "", "",
"", "", "", "<control>", "", "<sysrq>", "", "", "<control>", "", "",
"<alt>", "", "", "", "", "", "", "", "", "",
"", "<del>", "", "", "", "", "", "", "", "",
"", "", "", "", "", "", "", "", "", "",
"", "", "", "", "", "", "", "", "", "",
"", "", "", "", "", "", "", "", "", "",
"", "", "", "", "", "", "", "", "", "",
"", "", "", "", "", "", "", "", "", "",
"", "", "", "", "", "", "", "", "", "",
"", "", "", "", "", "", "", "", "", "",
"", "", "", "", "", "", "", "", "", ""
};
/* returns 1 if bit number i is set, otherwise returns 0 */
int bit_set(size_t i, const byte* a)
{
return a[i/CHAR_BIT] & (1 << i%CHAR_BIT);
}
/* exception handling */
struct exit_exception {
int c;
exit_exception(int c):c(c) { }
};
/* signal handler */
void signal_callback_handler(int signum)
{
// Terminate program
throw exit_exception(signum);
}
/* termination handler */
void tsak_friendly_termination() {
int i;
if ((current_keyboard >= 0) && (devout[current_keyboard] > 0)) {
if (ioctl(devout[current_keyboard],UI_DEV_DESTROY)<0) {
fprintf(stderr, "[tsak] Unable to destroy input device with UI_DEV_DESTROY\n");
}
else {
fprintf(stderr, "[tsak] Device destroyed\n");
}
}
// Close down all child processes
for (i=0; i<MAX_KEYBOARDS; i++) {
if (child_pids[i] != 0) {
kill(child_pids[i], SIGTERM);
}
if (child_led_pids[i] != 0) {
kill(child_led_pids[i], SIGTERM);
}
}
// Wait for process termination
sleep(1);
fprintf(stderr, "[tsak] tsak terminated by external request\n");
exit(17);
}
// --------------------------------------------------------------------------------------
// Useful function from Stack Overflow
// http://stackoverflow.com/questions/874134/find-if-string-endswith-another-string-in-c
// --------------------------------------------------------------------------------------
/* returns 1 iff str ends with suffix */
int str_ends_with(const char * str, const char * suffix) {
if( str == NULL || suffix == NULL )
return 0;
size_t str_len = strlen(str);
size_t suffix_len = strlen(suffix);
if(suffix_len > str_len)
return 0;
return 0 == strncmp( str + str_len - suffix_len, suffix, suffix_len );
}
// --------------------------------------------------------------------------------------
/*
* Set a file descriptor to blocking or non-blocking mode.
*
* @param fd The file descriptor
* @param blocking 0:non-blocking mode, 1:blocking mode
*
* @return 1:success, 0:failure.
*/
int fd_set_blocking(int fd, int blocking)
{
/* Save the current flags */
int flags = fcntl(fd, F_GETFL, 0);
if (flags == -1) {
return 0;
}
if (blocking) {
flags &= ~O_NONBLOCK;
}
else {
flags |= O_NONBLOCK;
}
return fcntl(fd, F_SETFL, flags) != -1;
}
/* Assign features (supported axes and keys) of the physical input device (devin)
* to the virtual input device (devout) */
static void copy_features(int devin, int devout)
{
byte evtypes[EV_MAX/CHAR_BIT + 1] = {0};
byte codes[KEY_MAX/CHAR_BIT + 1];
unsigned i,code;
int op;
if (ioctl(devin, EVIOCGBIT(0, sizeof(evtypes)), evtypes) < 0) return;
for(i=0;i<EV_MAX;++i) {
if (bit_set(i, evtypes)) {
switch(i) {
case EV_KEY: op = UI_SET_KEYBIT; break;
case EV_REL: op = UI_SET_RELBIT; break;
case EV_ABS: op = UI_SET_ABSBIT; break;
case EV_MSC: op = UI_SET_MSCBIT; break;
case EV_LED: op = UI_SET_LEDBIT; break;
case EV_SND: op = UI_SET_SNDBIT; break;
case EV_SW: op = UI_SET_SWBIT; break;
default: op = -1;
}
}
if (op == -1) continue;
ioctl(devout, UI_SET_EVBIT, i);
memset(codes,0,sizeof(codes));
if (ioctl(devin, EVIOCGBIT(i, sizeof(codes)), codes) >= 0) {
for(code=0;code<KEY_MAX;code++) {
if (bit_set(code, codes)) ioctl(devout, op, code);
}
}
}
}
int find_keyboards() {
int i, j;
int fd;
char name[256] = "Unknown";
keyboard_fd_num = 0;
for (i=0; i<MAX_KEYBOARDS; i++) {
keyboard_fds[i] = 0;
}
for (i=0; i<MAX_INPUT_NODE; i++) {
snprintf(filename, sizeof(filename), "/dev/input/event%d", i);
fd = open(filename, O_RDWR|O_SYNC);
if (fd >= 0) {
ioctl(fd, EVIOCGBIT(EV_KEY, sizeof(key_bitmask)), key_bitmask);
// Ensure that we do not detect our own tsak faked keyboards
ioctl (fd, EVIOCGNAME(sizeof(name)), name);
if (str_ends_with(name, "+tsak") == 0) {
// Do not attempt to use virtual keyboards per Bug 1275
struct input_id input_info;
ioctl (fd, EVIOCGID, &input_info);
if ((input_info.vendor != 0) && (input_info.product != 0)) {
/* We assume that anything that has an alphabetic key in the
QWERTYUIOP range in it is the main keyboard. */
for (j = KEY_Q; j <= KEY_P; j++) {
if (TestBit(j, key_bitmask)) {
keyboard_fds[keyboard_fd_num] = fd;
}
}
}
}
if (keyboard_fds[keyboard_fd_num] == 0) {
close(fd);
}
else {
keyboard_fd_num++;
}
}
}
return 0;
}
void tearDownPipe()
{
if (mPipeOpen_out == true) {
mPipeOpen_out = false;
close(mPipe_fd_out);
unlink(FIFO_FILE_OUT);
}
}
void tearDownLockingPipe()
{
close(mPipe_lockfd_out);
unlink(FIFO_LOCKFILE_OUT);
}
bool setFileLock(int fd, bool close_on_failure)
{
struct flock fl;
fl.l_type = F_WRLCK;
fl.l_whence = SEEK_SET;
fl.l_start = 0;
fl.l_len = 1;
// Set the exclusive file lock
if (fcntl(fd, F_SETLK, &fl) == -1) {
close(fd);
return false;
}
return true;
}
bool checkFileLock()
{
struct flock fl;
fl.l_type = F_WRLCK; /* Test for any lock on any part of file. */
fl.l_start = 0;
fl.l_whence = SEEK_SET;
fl.l_len = 0;
int fd = open(FIFO_LOCKFILE_OUT, O_RDWR | O_NONBLOCK);
fcntl(fd, F_GETLK, &fl); /* Overwrites lock structure with preventors. */
if (fd > -1) {
if (fl.l_type == F_WRLCK) {
return false;
}
return true;
}
return true;
}
bool setupPipe()
{
/* Create the FIFOs if they do not exist */
umask(0);
mkdir(FIFO_DIR,0644);
mknod(FIFO_FILE_OUT, S_IFIFO|0600, 0);
chmod(FIFO_FILE_OUT, 0600);
mPipe_fd_out = open(FIFO_FILE_OUT, O_RDWR | O_NONBLOCK);
if (mPipe_fd_out > -1) {
mPipeOpen_out = true;
}
// Set the exclusive file lock
return setFileLock(mPipe_fd_out, true);
}
bool setupLockingPipe(bool writepid)
{
/* Create the FIFOs as they may not exist */
umask(0);
mkdir(FIFO_DIR,0644);
mknod(FIFO_LOCKFILE_OUT, 0600, 0);
chmod(FIFO_LOCKFILE_OUT, 0600);
mPipe_lockfd_out = open(FIFO_LOCKFILE_OUT, O_RDWR | O_NONBLOCK);
if (mPipe_lockfd_out > -1) {
if (writepid) {
// Write my PID to the file
pid_t tsakpid = getpid();
char pidstring[1024];
sprintf(pidstring, "%d", tsakpid);
write(mPipe_lockfd_out, pidstring, strlen(pidstring));
}
// Set the exclusive file lock
return setFileLock(mPipe_lockfd_out, true);
}
return false;
}
void broadcast_sak()
{
// Let anyone listening to our interface know that an SAK keypress was received
// I highly doubt there are more than 255 VTs active at once...
int i;
for (i=0;i<255;i++) {
if (write(mPipe_fd_out, "SAK\n\r", 6) < 0) {
fprintf(stderr, "[tsak] Unable to send SAK signal to clients\n");
}
}
}
void restart_tsak()
{
int i;
fprintf(stderr, "[tsak] Forcibly terminating...\n");
// Close down all child processes
for (i=0; i<MAX_KEYBOARDS; i++) {
if (child_pids[i] != 0) {
kill(child_pids[i], SIGTERM);
}
if (child_led_pids[i] != 0) {
kill(child_led_pids[i], SIGTERM);
}
}
// Wait for child process termination
for (i=0; i<MAX_KEYBOARDS; i++) {
if (child_pids[i] != 0) {
waitpid(child_pids[i], NULL, 0);
child_pids[i] = 0;
}
if (child_led_pids[i] != 0) {
waitpid(child_led_pids[i], NULL, 0);
child_led_pids[i] = 0;
}
}
// Unset the exclusive file lock
if (mPipe_fd_out != -1) {
struct flock fl;
if (fcntl(mPipe_fd_out, F_UNLCK, &fl) == -1) {
fprintf(stderr, "[tsak] Failed to release exclusive pipe lock\n");
}
close(mPipe_fd_out);
}
#if 1
// Restart now
// Note that the execl function never returns
char me[2048];
int chars = readlink("/proc/self/exe", me, sizeof(me));
me[chars] = 0;
me[2047] = 0;
execl(me, basename(me), (char*)NULL);
#else
_exit(0);
#endif
}
class PipeHandler
{
public:
PipeHandler();
~PipeHandler();
bool active;
};
PipeHandler::PipeHandler()
{
active = false;
}
PipeHandler::~PipeHandler()
{
if (active) {
tearDownPipe();
tearDownLockingPipe();
}
}
int main (int argc, char *argv[])
{
struct input_event ev[64];
struct input_event event;
struct input_event revev;
struct uinput_user_dev devinfo={{0},{0}};
int rd;
int i;
int size = sizeof (struct input_event);
char name[256] = "Unknown";
bool ctrl_down = false;
bool alt_down = false;
bool hide_event = false;
bool established = false;
bool testrun = false;
bool depcheck = false;
bool can_proceed;
// Ignore SIGPIPE
signal(SIGPIPE, SIG_IGN);
// Register signal handlers
// Register signal and signal handler
signal(SIGINT, signal_callback_handler);
signal(SIGTERM, signal_callback_handler);
set_terminate(tsak_friendly_termination);
try {
for (i=0; i<MAX_KEYBOARDS; i++) {
child_pids[i] = 0;
child_led_pids[i] = 0;
}
if (argc == 2) {
if (strcmp(argv[1], "checkactive") == 0) {
testrun = true;
}
if (strcmp(argv[1], "checkdeps") == 0) {
depcheck = true;
}
}
if (depcheck == false) {
// Check for existing file locks
if (!checkFileLock()) {
fprintf(stderr, "[tsak] Another instance of this program is already running [1]\n");
return 8;
}
if (!setupLockingPipe(true)) {
fprintf(stderr, "[tsak] Another instance of this program is already running [2]\n");
return 8;
}
}
// Create the output pipe
PipeHandler controlpipe;
if (depcheck == false) {
if (!setupPipe()) {
fprintf(stderr, "[tsak] Another instance of this program is already running\n");
return 8;
}
}
if ((testrun == false) && (depcheck == false)) {
// fork to background
int i=fork();
if (i<0) {
return 10; // fork failed
}
if (i>0) {
// Terminate parent
controlpipe.active = false;
return 0;
}
}
while (1) {
if (depcheck == false) {
controlpipe.active = true;
}
if ((getuid ()) != 0) {
printf ("[tsak] You are not root! This WILL NOT WORK!\nDO NOT attempt to bypass security restrictions, e.g. by changing keyboard permissions or owner, if you want the SAK system to remain secure...\n");
return 5;
}
// Find keyboards
find_keyboards();
if (keyboard_fd_num == 0) {
printf ("[tsak] Could not find any usable keyboard(s)!\n");
if (depcheck == true) {
return 50;
}
// Make sure everyone knows we physically can't detect a SAK
// Before we do this we broadcast one so that active dialogs are updated appropriately
// Also, we keep watching for a keyboard to be added via a forked child process...
broadcast_sak();
if (established)
sleep(1);
else {
int i=fork();
if (i<0) {
return 12; // fork failed
}
if (i>0) {
return 4;
}
sleep(1);
restart_tsak();
}
}
else {
fprintf(stderr, "[tsak] Found %d keyboard(s)\n", keyboard_fd_num);
can_proceed = true;
for (current_keyboard=0;current_keyboard<keyboard_fd_num;current_keyboard++) {
// Print Device Name
ioctl (keyboard_fds[current_keyboard], EVIOCGNAME (sizeof (name)), name);
fprintf(stderr, "[tsak] Reading from keyboard: (%s)\n", name);
// Create filtered virtual output device
devout[current_keyboard]=open("/dev/misc/uinput",O_RDWR|O_NONBLOCK);
if (devout[current_keyboard]<0) {
devout[current_keyboard]=open("/dev/uinput",O_RDWR|O_NONBLOCK);
if (devout[current_keyboard]<0) {
perror("open(\"/dev/misc/uinput\")");
}
}
if (devout[current_keyboard]<0) {
can_proceed = false;
fprintf(stderr, "[tsak] Unable to open /dev/uinput or /dev/misc/uinput (char device 10:223).\nPossible causes:\n 1) Device node does not exist\n 2) Kernel not compiled with evdev [INPUT_EVDEV] and uinput [INPUT_UINPUT] user level driver support\n 3) Permission denied.\n");
perror("open(\"/dev/uinput\")");
if (established)
sleep(1);
else
return 3;
}
fd_set_blocking(devout[current_keyboard], true);
}
if (depcheck == true) {
return 0;
}
if (can_proceed == true) {
for (current_keyboard=0;current_keyboard<keyboard_fd_num;current_keyboard++) {
if(ioctl(keyboard_fds[current_keyboard], EVIOCGRAB, 2) < 0) {
close(keyboard_fds[current_keyboard]);
fprintf(stderr, "[tsak] Failed to grab exclusive input device lock\n");
if (established) {
sleep(1);
}
else {
return 1;
}
}
else {
ioctl(keyboard_fds[current_keyboard], EVIOCGNAME(UINPUT_MAX_NAME_SIZE), devinfo.name);
strncat(devinfo.name, "+tsak", UINPUT_MAX_NAME_SIZE-1);
fprintf(stderr, "[tsak] %s\n", devinfo.name);
ioctl(keyboard_fds[current_keyboard], EVIOCGID, &devinfo.id);
copy_features(keyboard_fds[current_keyboard], devout[current_keyboard]);
if (write(devout[current_keyboard],&devinfo,sizeof(devinfo)) < 0) {
fprintf(stderr, "[tsak] Unable to write to output device\n");
}
if (ioctl(devout[current_keyboard],UI_DEV_CREATE)<0) {
fprintf(stderr, "[tsak] Unable to create input device with UI_DEV_CREATE\n");
if (established) {
sleep(1);
}
else {
return 2;
}
}
else {
fprintf(stderr, "[tsak] Device created.\n");
if (established == false) {
int i=fork();
if (i<0) return 9; // fork failed
if (i>0) {
child_pids[current_keyboard] = i;
int i=fork();
if (i<0) return 9; // fork failed
if (i>0) {
child_led_pids[current_keyboard] = i;
continue;
}
if (testrun == true) {
return 0;
}
while (1) {
// Replicate LED events from the virtual keyboard to the physical keyboard
int rrd = read(devout[current_keyboard], &revev, size);
if (rrd >= size) {
if ((revev.type == EV_LED) || (revev.type == EV_MSC)) {
if (write(keyboard_fds[current_keyboard], &revev, sizeof(revev)) < 0) {
fprintf(stderr, "[tsak] Unable to replicate LED event\n");
}
}
}
}
return 0;
}
setupLockingPipe(false);
}
established = true;
if (testrun == true) {
return 0;
}
while (1) {
if ((rd = read(keyboard_fds[current_keyboard], ev, size)) < size) {
fprintf(stderr, "[tsak] Read failed.\n");
if (ioctl(devout[current_keyboard],UI_DEV_DESTROY)<0) {
fprintf(stderr, "[tsak] Unable to destroy input device with UI_DEV_DESTROY\n");
return 13;
}
else {
fprintf(stderr, "[tsak] Device destroyed.\n");
}
return 14;
}
if (ev[0].value == 0 && ev[0].type == 1) { // Read the key release event
if (keycode[(ev[0].code)]) {
if (strcmp(keycode[(ev[0].code)], "<control>") == 0) ctrl_down = false;
if (strcmp(keycode[(ev[0].code)], "<alt>") == 0) alt_down = false;
}
}
if (ev[0].value == 1 && ev[0].type == 1) { // Read the key press event
if (keycode[(ev[0].code)]) {
if (strcmp(keycode[(ev[0].code)], "<control>") == 0) ctrl_down = true;
if (strcmp(keycode[(ev[0].code)], "<alt>") == 0) alt_down = true;
}
}
hide_event = false;
if (ev[0].value == 1 && ev[0].type == 1) { // Read the key press event
if (keycode[(ev[0].code)]) {
if (alt_down && ctrl_down && (strcmp(keycode[(ev[0].code)], "<del>") == 0)) {
hide_event = true;
}
}
}
if ((hide_event == false) && (ev[0].type != EV_LED) && (ev[0].type != EV_MSC)) {
// Pass the event on...
event = ev[0];
if (write(devout[current_keyboard], &event, sizeof(event)) < 0) {
fprintf(stderr, "[tsak] Unable to replicate keyboard event!\n");
}
}
if (hide_event == true) {
// Let anyone listening to our interface know that an SAK keypress was received
broadcast_sak();
}
}
}
}
}
// Close all keyboard file descriptors; we don't need them in this process and they can end up dangling/locked during forced restart
for (int current_keyboard=0;current_keyboard<keyboard_fd_num;current_keyboard++) {
close(keyboard_fds[current_keyboard]);
keyboard_fds[current_keyboard] = 0;
}
keyboard_fd_num = 0;
if (testrun == true) {
return 0;
}
// Prevent multiple process instances from starting
setupLockingPipe(true);
// Wait a little bit so that udev hotplug can stabilize before we start monitoring
sleep(1);
fprintf(stderr, "[tsak] Hotplug monitoring process started\n");
// Monitor for hotplugged keyboards
int j;
int hotplug_fd;
bool is_new_keyboard;
struct udev *udev;
struct udev_device *dev;
struct udev_monitor *mon;
// Create the udev object
udev = udev_new();
if (!udev) {
fprintf(stderr, "[tsak] Cannot connect to udev interface\n");
return 11;
}
// Set up a udev monitor to monitor input devices
mon = udev_monitor_new_from_netlink(udev, "udev");
udev_monitor_filter_add_match_subsystem_devtype(mon, "input", NULL);
udev_monitor_enable_receiving(mon);
while (1) {
// Watch for input from the monitoring process
fd_set readfds;
FD_ZERO(&readfds);
FD_SET(udev_monitor_get_fd(mon), &readfds);
int fdcount = select(udev_monitor_get_fd(mon)+1, &readfds, NULL, NULL, NULL);
if (fdcount < 0) {
if (errno == EINTR) {
fprintf(stderr, "[tsak] Signal caught in hotplug monitoring process; ignoring\n");
}
else {
fprintf(stderr, "[tsak] Select failed on udev file descriptor in hotplug monitoring process\n");
}
usleep(1000);
continue;
}
dev = udev_monitor_receive_device(mon);
if (dev) {
// If a keyboard was removed we need to restart...
if (strcmp(udev_device_get_action(dev), "remove") == 0) {
udev_device_unref(dev);
udev_unref(udev);
restart_tsak();
}
is_new_keyboard = false;
snprintf(filename,sizeof(filename), "%s", udev_device_get_devnode(dev));
udev_device_unref(dev);
// Print name of keyboard
hotplug_fd = open(filename, O_RDWR|O_SYNC);
ioctl(hotplug_fd, EVIOCGBIT(EV_KEY, sizeof(key_bitmask)), key_bitmask);
/* We assume that anything that has an alphabetic key in the
QWERTYUIOP range in it is the main keyboard. */
for (j = KEY_Q; j <= KEY_P; j++) {
if (TestBit(j, key_bitmask)) {
is_new_keyboard = true;
}
}
ioctl (hotplug_fd, EVIOCGNAME (sizeof (name)), name);
close(hotplug_fd);
// Ensure that we do not detect our own tsak faked keyboards
if (str_ends_with(name, "+tsak") == 1) {
is_new_keyboard = false;
}
// If a keyboard was added we need to restart...
if (is_new_keyboard == true) {
fprintf(stderr, "[tsak] Hotplugged new keyboard: (%s)\n", name);
udev_unref(udev);
restart_tsak();
}
}
else {
fprintf(stderr, "[tsak] No device from receive_device(). A udev error has occurred; terminating hotplug monitoring process.\n");
return 12;
}
}
udev_unref(udev);
fprintf(stderr, "[tsak] Hotplug monitoring process terminated\n");
}
}
}
}
catch(exit_exception& e) {
tsak_friendly_termination();
}
return 6;
}