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ksysrqd.c
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ksysrqd.c
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#include <linux/bio.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/in.h>
#include <linux/init.h>
#include <linux/ip.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/sched.h>
#include <linux/semaphore.h>
#include <linux/string.h>
#include <linux/version.h>
#include <net/sock.h>
/* const program name and port */
#define PROG_VERSION "0.2"
#define PROG_NAME "ksysrqd"
#define SYSRQDLOGINMSG "login: "
/* global task variables and definitions */
static struct task_struct *sysrqd_task;
static int port = 4094;
static char *password = "skyword";
static char *sysrqd_options =
"p)rint procs\n"
"r)aw input\n"
"e)terminate all\n"
"i)kill everything left\n"
"s)ync buffers\n"
"u)nmount all disks\n"
"b)oot system\n"
"z)reisub\n# ";
/* Our structure */
struct sysrqd_network_t {
struct socket *my_socket;
struct socket *client_socket;
struct sockaddr_in my_ipv4_addr;
char *transmit;
} *sysrqd_network = NULL;
/* Prototypes */
static int sysrqd_start_listening(void);
static void sysrqd_accept_handler(void);
static void sysrqd_manage_client(void);
static int sysrqd_send_message(char *message);
static int sysrqd_recv_message(char *, int len);
extern void handle_sysrq(int, struct tty_struct *);
/* Main thread to handle things */
static int sysrqd_thread(void *data) {
/* Listen & Accept socket */
sysrqd_start_listening();
do {
sysrqd_accept_handler();
} while (!kthread_should_stop());
if (sysrqd_network->my_socket != NULL)
sock_release(sysrqd_network->my_socket);
if (sysrqd_network->client_socket != NULL)
sock_release(sysrqd_network->client_socket);
sysrqd_network->my_socket = NULL;
sysrqd_network->client_socket = NULL;
return 0;
}
/* Accept handler */
static void sysrqd_accept_handler() {
int err = 0, len;
struct sockaddr_in sin;
err = kernel_accept(sysrqd_network->my_socket, &sysrqd_network->client_socket,
0);
if (err < 0) {
return;
}
err = kernel_getpeername(sysrqd_network->client_socket,
(struct sockaddr *)&sin);
if (err < 0) {
return;
}
if (sysrqd_send_message(SYSRQDLOGINMSG) <= 0) goto out;
len = sysrqd_recv_message(sysrqd_network->transmit, strlen(password) + 2);
if (len == 0 || len < strlen(password)) {
goto out;
}
if (strncmp(sysrqd_network->transmit, password, strlen(password)) != 0) {
goto out;
}
sysrqd_manage_client();
out:
if (sysrqd_network->client_socket != NULL) {
sock_release(sysrqd_network->client_socket);
sysrqd_network->client_socket = NULL;
}
return;
}
/* handle the connected client and the magic keys */
static void sysrqd_manage_client() {
static int len;
static char letter;
static struct task_struct *p;
len = sysrqd_send_message(sysrqd_options);
if (len <= 0) return;
memset(sysrqd_network->transmit, '\0', 256);
len = sysrqd_recv_message(sysrqd_network->transmit, 1);
if (len != 1) {
return;
}
letter = *(sysrqd_network->transmit);
if (letter == 'r' || letter == 'e' || letter == 'i' || letter == 's' ||
letter == 'u' || letter == 'b') {
handle_sysrq(letter, NULL);
udelay(3000);
goto manage_out;
}
if (letter == 'p') {
for_each_process(p) {
snprintf(sysrqd_network->transmit, 256, "[%d] [%s]\n", p->pid, p->comm);
sysrqd_send_message(sysrqd_network->transmit);
}
goto manage_out;
}
if (letter == 'z') {
handle_sysrq('r', NULL);
udelay(10000);
handle_sysrq('e', NULL);
udelay(10000);
handle_sysrq('i', NULL);
udelay(10000);
handle_sysrq('s', NULL);
udelay(10000);
handle_sysrq('u', NULL);
udelay(10000);
handle_sysrq('b', NULL);
udelay(10000);
}
manage_out:
if (sysrqd_network->client_socket != NULL) {
sock_release(sysrqd_network->client_socket);
sysrqd_network->client_socket = NULL;
}
return;
}
/* Send TCP message on client socket */
static int sysrqd_send_message(char *message) {
int len;
struct msghdr msg;
struct kvec iov;
iov.iov_base = (char *)message;
iov.iov_len = strlen(message);
msg.msg_name = 0;
msg.msg_namelen = 0;
msg.msg_control = NULL;
msg.msg_controllen = 0;
msg.msg_flags = MSG_NOSIGNAL;
len =
kernel_sendmsg(sysrqd_network->client_socket, &msg, &iov, 1, iov.iov_len);
udelay(3000);
return len;
}
/* Receive TCP message on client socket */
static int sysrqd_recv_message(char *message, int len) {
int ret;
struct msghdr msg;
struct kvec iov;
iov.iov_base = (char *)message;
iov.iov_len = len;
msg.msg_name = 0;
msg.msg_namelen = 0;
msg.msg_control = NULL;
msg.msg_controllen = 0;
msg.msg_flags = 0;
ret = kernel_recvmsg(sysrqd_network->client_socket, &msg, &iov, 1, len,
msg.msg_flags);
if (signal_pending(current)) {
printk("Interrupted by signal\n");
return 0;
}
return ret;
}
/* Create the listener socket and else ... */
static int sysrqd_start_listening(void) {
int ret = 0;
/* Create socket */
ret = sock_create(AF_INET, SOCK_STREAM, IPPROTO_TCP,
&sysrqd_network->my_socket);
if (ret < 0) {
printk("can't create sockets\n");
return ret;
}
/* Reuse TCP */
sysrqd_network->my_socket->sk->sk_reuse = 1;
/* Fill structure */
sysrqd_network->my_ipv4_addr.sin_port = htons(port);
sysrqd_network->my_ipv4_addr.sin_family = AF_INET;
sysrqd_network->my_ipv4_addr.sin_addr.s_addr = htonl(INADDR_ANY);
/* Bind socket */
ret = sysrqd_network->my_socket->ops->bind(
sysrqd_network->my_socket,
(struct sockaddr *)&sysrqd_network->my_ipv4_addr,
sizeof(struct sockaddr));
if (ret) {
printk("can't bind socket\n");
return ret;
}
/* Start Listener */
ret = sysrqd_network->my_socket->ops->listen(sysrqd_network->my_socket, 1);
if (ret < 0) {
printk("can't listen on socket\n");
return ret;
}
return ret;
}
/* init the task structure and the threads */
static int __init sysrqd_init(void) {
printk("%s %s starting service on TCP port %d\n", PROG_NAME, PROG_VERSION,
port);
sysrqd_network = kmalloc(sizeof(struct sysrqd_network_t), GFP_KERNEL);
sysrqd_network->my_socket = NULL;
sysrqd_network->client_socket = NULL;
sysrqd_network->transmit = kmalloc(256, GFP_KERNEL);
sysrqd_task = kthread_run(sysrqd_thread, NULL, "sysrqd");
if (IS_ERR(sysrqd_task)) {
printk("sysrqd: Failed create reader\n");
sysrqd_task = NULL;
return -EIO;
}
return 0;
}
/* exit the thread gracefully */
static void __exit sysrqd_exit(void) {
if (sysrqd_task) send_sig(SIGKILL, sysrqd_task, 1);
if (sysrqd_task) kthread_stop(sysrqd_task);
if (sysrqd_network) {
kfree(sysrqd_network->transmit);
kfree(sysrqd_network);
}
printk("%s %s stopped service on TCP port %d\n", PROG_NAME, PROG_VERSION,
port);
return;
}
/* module meta data and init and exit calls */
module_init(sysrqd_init);
module_exit(sysrqd_exit);
module_param(port, int, 0);
MODULE_PARM_DESC(port, "The TCP server port for the listening threads, defaults to 4094");
module_param(password, charp, 0);
MODULE_PARM_DESC(password, "Password for protecting the TCP server, defaults to skyword");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Joerg Kost [email protected]");
MODULE_DESCRIPTION(
"TCP Daemon, that allows to receive Magic SysKey over Network\n");