I'm trying to enter multi-characters in an ncurses-application (e.g. accents, special characters):
I enter before that in the terminal:
xmodmap -e "keycode 66 = Multi_key"
and then:
capslock e =
(these 3 keys) gives an euro sign: € <- there you should see an euro
sign, see https://en.wikipedia.org/wiki/Euro_sign
In the ncurses application I get garbage or the terminal seems to hang - I then need to press a couple of keys to-unhang it often that does not work.
#include <ncursesw/curses.h>
int main(int argc, char *argv[])
{
setlocale(LC_ALL,"");
initscr();
start_color();
use_default_colors();
keypad(stdscr, TRUE);
cbreak();
intrflush(stdscr, FALSE);
noecho();
refresh();
nodelay(stdscr, FALSE);
meta(stdscr, TRUE); /* enable 8-bit input */
raw(); /* to be able to catch ctrl+c */
leaveok(stdscr, TRUE);
for(;;) {
wint_t ch;
if (get_wch(&ch) != ERR) {
wchar_t temp[] = { ch, 0x00 };
addwstr(temp);
}
else {
addwstr(L" {ERR} ");
}
refresh();
}
return 0;
}
Any ideas?
Related
I'm trying to write a program that intercepts Ctrl^C using sigaction, and then terminates the child of a fork.
Code:
static void usrHandler(int sig, siginfo_t * si, void * ignore) {
printf("Interrupt Worked");
}
int main(int argc, char * argv[]) {
struct sigaction sa;
sa.sa_flags = SA_SIGINFO;
sigemptyset( & sa.sa_mask);
sa.sa_sigaction = usrHandler;
sigaction(SIGINT, & sa, NULL);
int currentFile = 1;
int fd;
int forkChild;
forkChild = fork();
if (forkChild == 0) {
sleep(100);
} else if (forkChild > 0) {
sa.sa_sigaction = SIG_IGN;
sigaction(SIGUSR1, & sa, NULL);
}
}
I tried to remove all non necessary code for my example. For some reason I can not get the interrupt to work when I press Ctrl^C. Eventually I would like to be able to close the child and continue in the parent. Am I doing something wrong here?
For some reason I can not get the interrupt to work when I press Ctrl^C.
Because your data in IO buffer, so change printf("Interrupt Worked"); to printf("Interrupt Worked\n"); (add \n), you will get data.
For IO buffer, see https://stackoverflow.com/a/53083985/7671328
I hook a syscall(open) on Linux, and want to print this opened filename.
then I call syscall(getcwd) to get the absolute path.
this is source code:
void *memndup_from_user(const void __user *src, long len)
{
void *kbuf = NULL;
if(src == NULL) {
return kbuf;
}
kbuf = kmalloc(len + 1, GFP_KERNEL);
if(kbuf != NULL) {
if (copy_from_user(kbuf, src, len)) {
printk(KERN_ALERT "%s\n", "copy_from_user failed.");
kfree(kbuf);
kbuf = NULL;
}
else {
((char *)kbuf)[len] = '\0';
}
} else {
printk(KERN_ALERT "%s\n", "kmalloc failed.");
}
return kbuf;
}
void *memdup_from_user(const void __user *src)
{
long len = 0;
if(src == NULL) {
return NULL;
}
len = strlen_user(src);
return memndup_from_user(src, len);
}
asmlinkage long fake_getcwd(char __user *buf, unsigned long size)
{
return real_getcwd(buf, size);
}
asmlinkage long
fake_open(const char __user *filename, int flags, umode_t mode)
{
if(flags & O_CREAT) {
char *k_filename = (char *)memdup_from_user(filename);
char *u_path = (char *)kmalloc(PAGE_SIZE, GFP_USER);
if(k_filename != NULL) {
printk(KERN_ALERT "ano_fake_open pid:%ld create : %s\n", ano_fake_getpid(), k_filename);
kfree(k_filename);
}
if(u_path != NULL) {
long retv;
retv = fake_getcwd(u_path, PAGE_SIZE);
if(retv > 0) {
printk(KERN_ALERT "getcwd ret val: %ld, path: %s\n", retv, u_path);
} else {
printk(KERN_ALERT "getcwd ret val: %ld, error...\n", retv);
}
kfree(u_path);
}
}
return real_open(filename, flags, mode);
}
the sys_getcwd requires an user space memory, and I call kmalloc with GFP_USER.
but sys_getcwd always return -EFAULT(Bad Address)...
this is dmesg logs:
[344897.726061] fake_open pid:70393 create : sssssssssssssssss
[344897.726065] getcwd ret val: -14, error...
[344897.727431] fake_open pid:695 create : /var/lib/rsyslog/imjournal.state.tmp
[344897.727440] getcwd ret val: -14, error...
so I find the implement in sys_getcwd, he does
# define __user __attribute__((noderef, address_space(1)))
# define __kernel __attribute__((address_space(0)))
#define __getname() kmem_cache_alloc(names_cachep, GFP_KERNEL)
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
{
char *page = __getname();
get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
...
// char *cwd = page + xxx; (xxx < PAGE_SIZE)
// len = PAGE_SIZE + page - cwd;
...
if (len <= size) {
error = len;
if (copy_to_user(buf, cwd, len))
error = -EFAULT;
}
}
obviously, getcwd alloc memory with flag GFP_KERNEL, then copy to my buffer( __user *buf ) from (GFP_KERNEL) !!!
isn't __user MACRO be GFP_USER ?
the flag GFP_USER brief is https://elixir.bootlin.com/linux/v4.4/source/include/linux/gfp.h#L208:
/* GFP_USER is for userspace allocations that also need to be directly
* accessibly by the kernel or hardware. It is typically used by hardware
* for buffers that are mapped to userspace (e.g. graphics) that hardware
* still must DMA to. cpuset limits are enforced for these allocations.
*/
what's wrong ?
This is wrong on at least two accounts:
syscall hijacking (let alone for something like open) is just a bad idea. the only sensible method to catch all possible open path is through using LSM hooks. it also happens to deal with the actual file being opened avoiding the race: you read the path in your routine, wrapped opens reads it again. but by that time malicious userspace could have changed it and you ended up looking at the wrong file.
it should be clear getcwd has to have a method of resolving a name in order to put it into the userspace buffer. you should dig in into the call and see what can be changed to put it in a kernel buffer.
Why are you doing this to begin with?
i have this code to Comparison two char
char pass[]="1";
char passin[100]="";
and code to put characters in variable
void loop() {
char key= keypad.waitForKey(); // read char from keypad
strcat(passin,key);
if(strcmp(pass,passin)==0)
{ lcd.clear();
lcd.print("login success");
}else
{ lcd.clear();
lcd.print("login failed");
lcd.setCursor(0,1);
}
}
delay (1000);
}
what the way to return the value of passin as define like first time
If you just want to compare one character with another you can use the "==" operator. Note that to declare a character you use single quotes e.g. 'a'.
The code can be like this:
char pass = '1';
char key;
void loop(){
key = keypad.waitForKey(); // read char from keypad
if(pass == key){
lcd.clear();
lcd.print("login success");
}else {
lcd.clear();
lcd.print("login failed");
lcd.setCursor(0,1);
}
delay(1000);
}
The character key will be set to the new value every iteration of the loop.
I am trying to use native messaging to send some data to my native windows application. It works well with the runtime.sendNativeMessage() method. When I am trying to use long lived connections which uses a port, it also can pass data from chrome to my app. However, chrome extension can only receive the first response from my app. I am sure that the port is still open because my app can still receive data from chrome. Following are my code:
Chrome Extension Script:
var port = chrome.runtime.connectNative('com.mydomain.app1');
port.onMessage.addListener(function(msg) {
console.log("Received from port:", msg);
});
port.onDisconnect.addListener(function() {
console.log("Disconnected");
});
chrome.tabs.onUpdated.addListener(
function(tabId, changeInfo, tab) {
var param = {};
param['url'] = tab.url;
port.postMessage( param);
}
}
My windows app in c++:
int _tmain(int argc, _TCHAR* argv[])
{
while( true )
{
//read the first four bytes (=> Length)
unsigned int length = 0;
for (int i = 0; i < 4; i++)
{
char c;
if( ( c=getchar()) != EOF)
length += c<<i*8;
else return 0;
}
//read the json-message
std::string msg = "";
for (int i = 0; i < length; i++)
{
msg += getchar();
}
//.... do something
//send a response message
std::string message = "{\"text\": \"This is a response message\"}";
unsigned int len = message.length();
// We need to send the 4 bytes of length information
std::cout << char(((len>>0) & 0xFF))
<< char(((len>>8) & 0xFF))
<< char(((len>>16) & 0xFF))
<< char(((len>>24) & 0xFF));
// Now we can output our message
std::cout << message.c_str();
std::cout.flush();
}
}
Notice that the last line "std::cout.flush();", if I comment it out, even the first response won't be shown in chrome. I just couldn't figure out how chrome reads from the app's stdout.
Try with automatic flushing - std::cout.setf( std::ios_base::unitbuf )
Also, the way you read/write the input/output messages length is incorrect and will fail on long messages.
This code works well for me:
int main(int argc, char* argv[])
{
std::cout.setf( std::ios_base::unitbuf );
while (true)
{
unsigned int ch, inMsgLen = 0, outMsgLen = 0;
std::string input = "", response = "";
// Read 4 bytes for data length
std::cin.read((char*)&inMsgLen, 4);
if (inMsgLen == 0)
{
break;
}
else
{
// Loop getchar to pull in the message until we reach the total length provided.
for (int i=0; i < inMsgLen; i++)
{
ch = getchar();
input += ch;
}
}
response.append("{\"echo\":").append(input).append("}");
outMsgLen = response.length();
// Send 4 bytes of data length
std::cout.write((char*)&outMsgLen, 4);
// Send the data
std::cout << response;
}
return 0;
}
While working in client-server programming, I have passed 3 strings in client, which will be received by server and it should be printed in there 3 times. (i.e I have used a 'for' loop which will do the read & write operations in client & server side respectively.), but in server only the 1st string is getting printed.
Please explain,
Here is my code
server.c
#include "head.h"
void readstr(int connfd ,char [][20]);
//void writestr(char * ,int);
int main(int c ,char *v[])
{
// socket declarations,etc
sd =socket( AF_INET ,SOCK_STREAM ,0);
// Binding socket
retbind =bind(sd ,(struct sockaddr*)&serveraddress ,sizeof(serveraddress
));
listen(sd ,4);
for(;;)
{
printf("i am waiting for client\n");
len =sizeof(cliaddr);
connfd = accept(sd ,(struct sockaddr*)&cliaddr ,&len);
readstr(connfd ,databuf);
close(connfd);
}
return 0;
}
void readstr(int connfd ,char str[3] [20])
{
int pointer=0 ,i=0, n,pos=0;
memset(str ,'\0',sizeof(str));
for(i=0;i<3;i++)
{
while((n=read(connfd ,str[i] ,20)) >>0)
{
printf("Looping while\n");
pos =pos +n;
}
str[i][pos] ='\0';
}
for(i=0;i<3;i++)
{
printf("\n%s",str[i]);
}
}
client.c
#include "head.h"
void send1(int ,char*);
int main(int c,char*v[])
{
//Socket declarations, etc..
sd = socket(AF_INET ,SOCK_STREAM ,0);
//Connect
if(connect(sd,(struct sockaddr*)&serveraddress ,sizeof(serveraddress)) <
0)
{
printf("cannot connect to server");
exit(1);
}
for(i=0;i<3;i++)
{
memset(buf ,'\0',sizeof(buf));
printf("\n Enter the string : ");
fgets(buf[i],20,stdin);
len =strlen(buf[i]);
if(buf[i][len] =='\n')
buf[i][len]='\0';
send1(sd ,(char *)buf);
}
shutdown(sd ,SHUT_WR);
}
void send1(int sd ,char *str)
{
int n ,byteswritten =0, wr;
char buf[1024];
strcpy(buf ,str);
n =strlen(buf);
while(byteswritten < n)
{
printf("\nStarting to write in client side\n");
wr = write(sd , buf+byteswritten ,(n-byteswritten));
byteswritten+=wr;
}
printf("\n string sent %s" ,buf);
}
In server.c in readstr() you are not setting pos to zero before the next for iteration.
Also, there is strange line:
while((n=read(connfd ,str[i] ,20)) >>0)
Note ">>".