tools.c

/*
 * Copyright Tian Hao <thxdaemon@gmail.com>
 * License: GPLv3
 * It is an opensource (free) software
 */

#define _POSIX_C_SOURCE 200809L
#define _XOPEN_SOURCE 700

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>
#include <errno.h>

#include "su.h"
#include "tools.h"

extern int killxsvr();

void err_quit(char* msg)
{
	perror(msg);
	killxsvr();
}

ssize_t mydm_print(char* fmt, ...)
{
	int fd;
	va_list ap;
	char buff[1024];
	ssize_t retval;

	fd = STDERR_FILENO;
	retval = 0;

	va_start(ap, fmt);
	vsnprintf(buff, sizeof(buff), fmt, ap);

	if (write(fd, "[mydm] ", 7) != 7) return -1;
	retval = write(fd, buff, strlen(buff));

	va_end(ap);

	return retval;
}

void* my_signal(int signum, void* handler, int restartsyscall)
{
	struct sigaction sa, osa;

	sa.sa_handler = handler;
	sigemptyset(&sa.sa_mask);
	if (restartsyscall) {
		sa.sa_flags = SA_RESTART;
	} else {
#ifdef SA_INTERRUPT
		sa.sa_flags = SA_INTERRUPT;
#endif
	}
	if(sigaction(signum, &sa, &osa) < 0)
		return (void*) -1;
	return osa.sa_handler;
}

int unblock_signal(int signum)
{
	sigset_t set, oset;
	sigemptyset(&set);
	sigaddset(&set, signum);
	return sigprocmask(SIG_UNBLOCK, &set, &oset);
}

int block_signal(int signum)
{
	sigset_t set, oset;
	sigemptyset(&set);
	sigaddset(&set, signum);
	return sigprocmask(SIG_BLOCK, &set, &oset);
}

int lock(int fd)
{
	struct flock lock;
	lock.l_type = F_WRLCK;
	lock.l_whence = SEEK_SET;
	lock.l_start = 0;
	lock.l_len = 0;
	return fcntl(fd,F_SETLK,&lock);
}

int unlock(int fd)
{
	struct flock lock;
	lock.l_type = F_UNLCK;
	lock.l_whence = SEEK_SET;
	lock.l_start = 0;
	lock.l_len = 0;
	return fcntl(fd,F_SETLK,&lock);
}

int exec_try_login_user(char* username, char* file, int no_system_su)
{
	if (username) {
		if (no_system_su) {
			if (switch_user(username) < 0) {
				mydm_print("Can not login user '%s'\n", username);
				return -1;
			}
			return execlp(file, file, NULL);
		} else {
			return execlp("su", "su", "-", username, "-c", file, NULL);
		}
	} else {
		return execlp(file, file, NULL);
	}
}

int pipefd[2];

void INIT_PIPE()
{
	int flags;

	if (pipe(pipefd) < 0)
		err_quit("pipe");

	flags = fcntl(pipefd[0], F_GETFD);
	flags |= FD_CLOEXEC;
	fcntl(pipefd[0], F_SETFD, flags);

	flags = fcntl(pipefd[1], F_GETFD);
	flags |= FD_CLOEXEC;
	fcntl(pipefd[1], F_SETFD, flags);
}

void TELL_PARENT()
{
	close(pipefd[0]);
	errno = 0;
	while ((write(pipefd[1], "e", 1) != 1) && (errno == EINTR));
	close(pipefd[1]);
}

int WAIT_CHILD()
{
	char c = 0;

	close(pipefd[1]);
	errno = 0;
	while ((read(pipefd[0], &c, 1) < 0) && (errno == EINTR));
	close(pipefd[0]);

	if (c == 'e')
		return -1;

	return 0;
}