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client.c
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client.c
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#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <termios.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <netdb.h>
#include <errno.h>
#include <time.h>
#include <assert.h>
#include <pty.h>
#include <utmp.h>
#include <stdbool.h>
#include "config.h"
#include "utils.h"
#include "rc4.h"
#include "sha1.h"
#if CLIENT_DBG
#define client_dbg(format, arg...) DBG_PRINT_FUNC(format, "CLIENT_DBG", ##arg)
#else
#define client_dbg(x...)
#endif
#define client_err(format, arg...) DBG_PRINT_FUNC(format, "CLIENT_ERR", ##arg)
/* signal handler */
static int got_sigchld = 0;
static void sighandler(int signum) {
if (signum == SIGCHLD) {
got_sigchld = 1;
}
}
static int setup_terminal(int tty, struct termios *tm) {
struct termios tbttr;
int ret = 0;
assert(tm != NULL);
ret = tcgetattr(0, tm);
if (ret) {
client_err("Failed to get terminal attributes: %d\n", errno);
return -1;
}
memcpy(&tbttr, tm, sizeof (tbttr));
tcsetattr(tty, TCSANOW, tm);
tbttr.c_iflag |= IGNPAR; /* Ignore framing errors and parity errors. */
tbttr.c_iflag &= ~(ISTRIP | INLCR | IGNCR | ICRNL | IXON | IXANY | IXOFF);
tbttr.c_lflag &= ~(ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHONL | IEXTEN);
tbttr.c_oflag &= ~OPOST;
tbttr.c_cc[VMIN] = 1;
tbttr.c_cc[VTIME] = 0;
tcsetattr(0, TCSANOW, &tbttr);
return 0;
}
static void reset_terminal(struct termios *tm) {
assert(tm != NULL);
tcsetattr(0, TCSANOW, tm);
}
static int create_server_connection(Connection_Data_t *cd) {
assert(cd != NULL);
if ((cd->server_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
client_err("Failed to open socket: %d\n", errno);
return -1;
}
cd->server_addr.sin_family = AF_INET;
cd->server_addr.sin_port = htons(SHELL_LOG_SERVER_PORT);
inet_aton(CONNECT_IP, &cd->server_addr.sin_addr);
cd->nb_pkt_sent = 0;
return 0;
}
static int create_real_shell_run_cmd(char *argv[],
char *cmd_str, int cmd_str_max_length) {
int cmd_str_index = 0;
char *last_slash = NULL;
int n = strlen(REAL_SHELL_DIR);
assert(cmd_str != NULL);
assert(argv != NULL);
if ((last_slash = strrchr(argv[0], '/')) == NULL) {
last_slash = argv[0];
} else {
last_slash++;
}
client_dbg("CMD: %s\n", last_slash);
if (n > cmd_str_max_length - cmd_str_index)
goto not_enough_buffer_length;
memcpy(&cmd_str[cmd_str_index], REAL_SHELL_DIR, n);
cmd_str_index += n;
if (cmd_str[cmd_str_index - 1] != '/') {
cmd_str[cmd_str_index++] = '/';
}
n = strlen(last_slash);
if (n > cmd_str_max_length - cmd_str_index)
goto not_enough_buffer_length;
memcpy(&cmd_str[cmd_str_index], last_slash, n);
cmd_str_index += n;
n = 1;
if (n > cmd_str_max_length - cmd_str_index)
goto not_enough_buffer_length;
cmd_str[cmd_str_index++] = '\0';
return 0;
not_enough_buffer_length:
client_err("Not enough buffer length for real shell command [need: %d, available: %d]\n",
n, cmd_str_max_length - cmd_str_index);
return -1;
}
static int encrypt_and_send(Connection_Data_t *cd, Session_Data_t * sd) {
int i = 0;
sha1_context sha1;
struct rc4_state rc4;
unsigned char pktkey[32];
unsigned char msg[MAX_TRANSFER_PKT_SZ];
int rc4_offset = 0;
int msg_index = 0;
assert(cd != NULL);
assert(sd != NULL);
srand(time(NULL));
/* setup a new RC4 IV */
for (rc4_offset = 0; rc4_offset < RC4_SZ; rc4_offset++)
msg[rc4_offset] = rand() & 0xFF;
/* append the packet header */
memcpy(&msg[RC4_SZ + msg_index], sd, SESSION_SZ);
msg_index += SESSION_SZ;
memcpy(&msg[RC4_SZ + msg_index], &sd->buffer[i], sd->len);
msg_index += sd->len;
msg[RC4_SZ + msg_index++] = '\0';
/* setup the per-packet RC4 key */
memcpy(pktkey, secret, RC4_SZ);
memcpy(pktkey + RC4_SZ, msg, RC4_SZ);
sha1_starts(&sha1);
sha1_update(&sha1, pktkey, SZARR(pktkey));
sha1_finish(&sha1, pktkey);
/* encrypt and send the buffer */
rc4_setup(&rc4, pktkey, SHA1_SZ);
rc4_crypt(&rc4, msg + RC4_SZ, msg_index + SHA1_SZ);
sha1_starts(&sha1);
sha1_update(&sha1, &msg[RC4_SZ], msg_index);
sha1_finish(&sha1, &msg[RC4_SZ + msg_index]);
sendto(cd->server_fd, msg, RC4_SZ + msg_index + SHA1_SZ, 0,
(struct sockaddr *) &cd->server_addr,
sizeof ( cd->server_addr));
#ifdef DEBUG
unsigned char sha1sum[SHA1_SZ];
Session_Data_t tsd;
int test_len = RC4_SZ + msg_index + SHA1_SZ;
printf("Sended message: \r\n");
printf(" seconds: %d\r\n", (int) sd->time);
printf(" uid: %d\r\n", (int) sd->uid);
printf(" pid: %d\r\n", (int) sd->pid);
printf(" dir: %d\r\n", (int) sd->dir);
printf(" len: %d\r\n", (int) sd->len);
printf(" data: \r\n");
__print_output(&sd->buffer[i], sd->len);
printf("\r\n\r\n");
sha1_starts(&sha1);
sha1_update(&sha1, msg + RC4_SZ, test_len - RC4_SZ - SHA1_SZ);
sha1_finish(&sha1, sha1sum);
if (memcmp(sha1sum, msg + test_len - SHA1_SZ, SHA1_SZ) != 0) {
shellog_err("SHA-1 checksum verification failed\n");
}
memcpy(pktkey, secret, RC4_SZ);
memcpy(pktkey + RC4_SZ, msg, RC4_SZ);
sha1_starts(&sha1);
sha1_update(&sha1, pktkey, 32);
sha1_finish(&sha1, pktkey);
rc4_setup(&rc4, pktkey, SHA1_SZ);
rc4_crypt(&rc4, msg + RC4_SZ, test_len - RC4_SZ - SHA1_SZ);
memcpy(&tsd, &msg[rc4_offset], sizeof (Session_Data_t));
printf("Decoded message: \r\n");
printf(" seconds: %d\r\n", (int) tsd.time);
printf(" uid: %d\r\n", (int) tsd.uid);
printf(" pid: %d\r\n", (int) tsd.pid);
printf(" dir: %d\r\n", (int) tsd.dir);
printf(" len: %d\r\n", (int) tsd.len);
printf(" data: \r\n");
__print_output(tsd.buffer, tsd.len);
printf("\r\n\r\n");
#endif
cd->nb_pkt_sent++;
return 0;
}
int main(int argc, char *argv[]) {
char real_shell[256];
int pty = 0, tty = 0;
Session_Data_t sd;
Connection_Data_t cd;
fd_set rd;
struct termios tty_tm; /* stored initial terminal settings */
struct termios pty_tm; /* current PTY terminal settings */
struct timeval tv;
cd.server_fd = pty = tty = -1;
/* reconstruct the original shell location */
if (create_real_shell_run_cmd(argv, real_shell, SZARR(real_shell))) {
client_err("Create real shell command failed\r\n");
goto exec_real_shell;
}
client_dbg("Start as : %s\r\n", real_shell);
if (isatty(0) == 0 ||
isatty(1) == 0 ||
isatty(2) == 0 ||
getlogin() == NULL) {
client_err("Skipping non interactive shell session\r\n");
goto exec_real_shell;
}
if (create_server_connection(&cd)) {
client_err("Create server connection failed\r\n");
goto exec_real_shell;
}
/* create a pseudo-terminal */
if (openpty(&pty, &tty, NULL, NULL, NULL) < 0) {
client_err("Open pseudo terminal failed: %d\r\n", errno);
goto exec_real_shell;
}
if (ttyname(tty) == NULL) {
client_err("Get TTY name failed: %d\r\n", errno);
goto exec_real_shell;
}
if (setup_terminal(tty, &tty_tm)) {
client_err("Setup terminal failed\r\n");
goto exec_real_shell;
}
/* handle child exit */
signal(SIGCHLD, sighandler);
/* fork to exec the original shell */
switch ((sd.pid = fork())) {
case(-1):
reset_terminal(&tty_tm);
client_err("Fork process failed: %d\r\n", errno);
goto exec_real_shell;
break;
case(0):
/* Child : real shell */
if (login_tty(tty)) {
client_err("Make tty be the controlling terminal failed: %d\r\n", errno);
goto exec_real_shell;
}
close(cd.server_fd);
usleep(50000);
execv(real_shell, argv);
tcsetattr(0, TCSANOW, &tty_tm);
exit(1);
break;
default:
/* Parent : shell logger */
sd.uid = getuid();
while (1) {
FD_ZERO(&rd);
FD_SET(pty, &rd);
FD_SET(0, &rd);
int n = (pty > 0) ? pty : 0;
if ((n = select(n + 1, &rd, NULL, NULL, NULL)) < 0) {
if (n < 0 && (errno == EINTR || errno == EAGAIN))
goto check_sigs;
break;
}
if (FD_ISSET(0, &rd)) {
gettimeofday(&tv, NULL);
sd.time = tv.tv_sec;
/* transfer the data from stdin to pty */
if ((n = read(0, sd.buffer, BUF_SZ)) <= 0) {
if (n < 0 && (errno == EINTR || errno == EAGAIN))
goto check_sigs;
break;
}
/* Check target terminal ECHO flag to skip password typing */
if (tcgetattr(pty, &pty_tm)) {
client_err("Failed to get terminal attributes: %d\r\n", errno);
goto check_sigs;
}
#ifdef DEBUG
struct termios prev_pty_tm; /* current PTY terminal settings */
if (memcmp(&pty_tm, &prev_pty_tm, sizeof (struct termios))) {
// printf("\r\n");
// __print_output(&prev_pty_tm.c_iflag, sizeof (prev_pty_tm.c_iflag));
// __print_output(&prev_pty_tm.c_lflag, sizeof (prev_pty_tm.c_lflag));
// printf("%X %X\r\n", prev_pty_tm.c_iflag, prev_pty_tm.c_lflag);
// printf("\r\n");
// __print_output(&pty_tm.c_iflag, sizeof (pty_tm.c_iflag));
// __print_output(&pty_tm.c_lflag, sizeof (pty_tm.c_lflag));
// printf("%X %X\r\n", pty_tm.c_iflag, pty_tm.c_lflag);
//
// printf("%X %X\r\n", pty_tm.c_iflag & INLCR, pty_tm.c_lflag & ICANON);
printf("IGNBRK %d\r\n", pty_tm.c_iflag & IGNBRK);
printf("BRKINT %d\r\n", pty_tm.c_iflag & BRKINT);
printf("IGNPAR %d\r\n", pty_tm.c_iflag & IGNPAR);
printf("PARMRK %d\r\n", pty_tm.c_iflag & PARMRK);
printf("INPCK %d\r\n", pty_tm.c_iflag & INPCK);
printf("ISTRIP %d\r\n", pty_tm.c_iflag & ISTRIP);
printf("INLCR %d\r\n", pty_tm.c_iflag & INLCR);
printf("IGNCR %d\r\n", pty_tm.c_iflag & IGNCR);
printf("ICRNL %d\r\n", pty_tm.c_iflag & ICRNL);
printf("IUCLC %d\r\n", pty_tm.c_iflag & IUCLC);
printf("IXON %d\r\n", pty_tm.c_iflag & IXON);
printf("IXANY %d\r\n", pty_tm.c_iflag & IXANY);
printf("IXOFF %d\r\n", pty_tm.c_iflag & IXOFF);
printf("IMAXBEL %d\r\n", pty_tm.c_iflag & IMAXBEL);
printf("IUTF8 %d\r\n", pty_tm.c_iflag & IUTF8);
memcpy(&prev_pty_tm, &pty_tm, sizeof (struct termios));
}
#endif
if ((pty_tm.c_iflag & ICRNL) && (pty_tm.c_lflag & ICANON)) {
/* password mode */
client_dbg("Password mode\r\n");
} else {
/* normal mode */
sd.dir = INPUT_DIR;
sd.len = n;
encrypt_and_send(&cd, &sd);
}
if ((n = write(pty, sd.buffer, n)) != n) {
if (n < 0 && (errno == EINTR || errno == EAGAIN))
goto check_sigs;
break;
}
}
if (FD_ISSET(pty, &rd)) {
gettimeofday(&tv, NULL);
sd.time = tv.tv_sec;
/* transfer the data from pty to stdout */
if ((n = read(pty, sd.buffer, BUF_SZ)) <= 0) {
if (n < 0 && (errno == EINTR || errno == EAGAIN))
goto check_sigs;
break;
}
#if LOG_OUTPUT
sd.dir = OUTPUT_DIR;
sd.len = n;
encrypt_and_send(&cd, &sd);
#endif
if ((n = write(1, sd.buffer, n)) != n) {
if (n < 0 && (errno == EINTR || errno == EAGAIN))
goto check_sigs;
break;
}
}
check_sigs:
if (got_sigchld == 1) {
got_sigchld = 0;
break;
}
}
break;
}
exec_real_shell:
if (tty >= 0)
close(tty);
if (pty >= 0)
close(pty);
if (cd.server_fd >= 0)
close(cd.server_fd);
execv(real_shell, argv);
exit(1);
}