berry-getty.c

// gcc -std=c99 -pipe -Os -fomit-frame-pointer -o getty getty.c
// https://github.com/StarchLinux/getty

#define _GNU_SOURCE
#include <sys/utsname.h>
#include <unistd.h>
#include <sys/param.h>
#include <utmp.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <errno.h>
#include <termios.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <time.h>

#define FMT_ULONG 40 /* enough space to hold 2^128 - 1 in decimal, plus \0 */
#define FMT_LEN ((char *) 0) /* convenient abbreviation */
unsigned int fmt_ulong(register char *s, register unsigned long u)
{
	register unsigned int len;
	register unsigned long q;
	len = 1;
	q = u;
	while (q > 9) {
		++len;
		q /= 10;
	}
	if (s) {
		s += len;
		do {
			*--s = '0' + (u % 10);
			u /= 10;
		} while (u); /* handles u == 0 */
	}
	return len;
}


static struct utsname uts;
static char hn[MAXHOSTNAMELEN + 6]="HOST=";
static int hn_len=5;
static time_t cur_time;
static char *tty;

static int noclear=0;

void whine(const char* message)
{
	write(2, message, strlen(message));
}

void error(char *message, int exitcode)
{
	whine(message);
	exit(exitcode);
}

static void echo_off()
{
	struct termios foo;
	if (!tcgetattr(0,&foo)) {
		foo.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL);
		tcsetattr(0, TCSANOW, &foo);
	}
}

void doutmp()
{
	off_t curpos;
	struct utmp ut;
	pid_t mypid=getpid();
	int fd = open(_PATH_UTMP, O_RDWR);
	if (fd) {
		for (;;) {
			int len;
			curpos = lseek(fd, 0, SEEK_CUR);
			len = read(fd, &ut, sizeof(ut));
			if (len!=sizeof(ut)) {
				break;
			}
			if (ut.ut_pid==mypid || !strcmp(ut.ut_line,tty+5)) {
				/*	write(1,"found my utmp record\n",21); */
				break;
			}
		}
		if (ut.ut_pid!=mypid) {
			memset(&ut, 0, sizeof(ut));
			ut.ut_pid = mypid;
			memcpy(ut.ut_id, tty+3, sizeof(ut.ut_id));
		}
		memcpy(ut.ut_user, "LOGIN", 6);
		memcpy(ut.ut_line, tty+5, sizeof(ut.ut_line));
		ut.ut_tv.tv_sec = cur_time;
		ut.ut_type = LOGIN_PROCESS;
		lseek(fd, curpos, SEEK_SET);
		write(fd, &ut, sizeof(ut));
		close(fd);
	}
	if ((fd = open(_PATH_WTMP, O_APPEND|O_WRONLY))>=0) {
		write(fd, &ut, sizeof(ut));
		close(fd);
	}
}

void sigquit_handler(int signum)
{
	error("SIGQUIT received\n", 23);
}

/*#include <linux/vt.h>
void chvt(int fd, int num)
{
	if (ioctl(fd, VT_ACTIVATE, num)) {
		perror("chvt: VT_ACTIVATE");
		exit(1);
	}
	if (ioctl(fd, VT_WAITACTIVE, num)) {
		perror("VT_WAITACTIVE");
		exit(1);
	}
}*/

void open_tty()
{
	struct sigaction sa;
	int fd;
	if (chown(tty, 0, 0) || chmod(tty, 0600)) {
		error("getty: could not chown/chmod tty device\n",1);
	}
	sa.sa_handler = SIG_IGN;
	sa.sa_flags = 0;
	sigemptyset(&sa.sa_mask);
	sigaction(SIGHUP, &sa, NULL);
	sa.sa_handler = sigquit_handler;
	sigaction(SIGQUIT, &sa, NULL);
	setsid();
	if ((fd = open(tty, O_RDWR, 0))<0) {
		error("getty: could not open tty device\n",3);
	}
	if (!isatty(fd)) {
		error("getty: not a typewriter\n",4);
	}
	if (ioctl(fd, TIOCSCTTY, (void *)1)==0) {
		if (vhangup()) {	/* linux specific */
			error("getty: vhangup failed\n",5);
		}
	} else {
		whine("getty: warning: could not set controlling tty!\n");
	}
//	chvt(fd, 8);
	close(2);
	close(1);
	close(0);
	close(fd);
	if (open(tty, O_RDWR, 0) != 0) {
		error("getty: could not open tty\n",6);
	}
	if (dup(0) != 1 || dup(0) != 2) {
		error("could not dup stdout and stderr\n",7);
	}
	if (!noclear) {
		write(0,"\033c",2);        /* linux specific */
	}
	sa.sa_handler = SIG_DFL;
	sa.sa_flags = 0;
	sigemptyset(&sa.sa_mask);
	sigaction(SIGHUP, &sa, NULL);
}

void output_special_char(char c)
{
	switch (c) {
	case 's':
		write(1,uts.sysname,strlen(uts.sysname));
		break;
	case 'n':
		write(1,uts.nodename,strlen(uts.nodename));
		break;
	case 'r':
		write(1,uts.release,strlen(uts.release));
		break;
	case 'v':
		write(1,uts.version,strlen(uts.version));
		break;
	case 'm':
		write(1,uts.machine,strlen(uts.machine));
		break;
	case 'o':
		write(1,uts.domainname,strlen(uts.domainname));
		break;
	case 't':
	case 'd': {
		time_t now;
		struct tm *tm;
		char buf[30];
		char *tmp;

		time (&now);
		tm = localtime (&now);
		if (c == 'd') {
			tmp=buf+fmt_ulong(buf,tm->tm_year+1900);
			*tmp++='-';
			tm->tm_mon++;
			*tmp++=tm->tm_mon/10+'0';
			*tmp++=tm->tm_mon%10+'0';
			*tmp++='-';
			*tmp++=tm->tm_mday/10+'0';
			*tmp++=tm->tm_mday%10+'0';
			*tmp++=0;
			write(1,buf,strlen(buf));
#if 0
			/* ISO 8601 */
			printf ("%d-%02d-%02d", tm->tm_year,
			        tm->tm_mon+1, tm->tm_mday);
#endif
		} else {
			buf[0]=tm->tm_hour/10+'0';
			buf[1]=tm->tm_hour%10+'0';
			buf[2]=':';
			buf[3]=tm->tm_min/10+'0';
			buf[4]=tm->tm_min%10+'0';
			buf[5]=':';
			buf[6]=tm->tm_sec/10+'0';
			buf[7]=tm->tm_sec%10+'0';
			write(1,buf,8);
		}
#if 0
		tmp=buf;
		printf ("%02d:%02d:%02d",
		        tm->tm_hour, tm->tm_min, tm->tm_sec);
#endif
		break;
	}
	case 'l':
		write(1,tty+5,strlen(tty)-5);
		break;
	case 'u':
	case 'U': {
		int users=0;
		struct utmp ut;
		int fd=open(_PATH_UTMP,O_RDWR);
		char buf[20];
		if (fd) {
			for (;;) {
				int len;
				len=read(fd,&ut,sizeof(ut));
				if (len!=sizeof(ut)) {
					break;
				}
				if (ut.ut_type == USER_PROCESS) {
					users++;
				}
			}
			close(fd);
		}
		write(1,buf,fmt_ulong(buf,users));
		if (c=='U') {
			if (users==1) {
				write(1," user",5);
			} else {
				write(1," users",6);
			}
		}
	}
	break;
	default:
		write(1,&c,1);
	}
}

void do_prompt()
{
	int fd = open("/etc/issue", O_RDONLY);
	char *buf;
	off_t length;
	write(1,"\n",1);
	if (fd) {
		char *c,*last;
		length=lseek(fd,0,SEEK_END);
		lseek(fd,0,SEEK_SET);
		buf=alloca(length+1);
		read(fd,buf,length);
		close(fd);
		last=buf+length;
		for (c=buf; c<last; c++) {
			if (*c=='\\') {
				output_special_char(*++c);
			} else {
				write(1,c,1);
			}
		}
	}

	write(1, hn+5, hn_len-5);
	write(1, " login: ", 8);
}

static inline int _isprint(char c)
{
	return ((c>='A' && c<='Z') ||
	        (c>='a' && c<='z') ||
	        (c>='0' && c<='9') ||
	        (c=='_' || c=='.' || c==',' || c=='-'));
}

char *get_logname()
{
	static char logname[40];
	char *c;
	ioctl(0, TCFLSH, 0); /* flush pending input */
	for (*logname=0; *logname==0; ) {
		do_prompt();
		for (c=logname;;) {
			if (read(0, c, 1)<1) {
				if (errno==EINTR || errno==EIO || errno==ENOENT) {
					exit(0);
				}
				error("received strange error\n", 9);
			}
			if (*c == '\n' || *c == '\r') {
				*c=0;
				break;
			} else if (!_isprint(*c)) {
				error("unprintable character in login name\n", 10);
			} else if (c-logname >= sizeof(logname)-1) {
				error("login name too long\n", 11);
			} else {
				c++;
			}
		}
	}
#if 0
	write(1,"\n\ngot name ",11);
	write(1,logname,strlen(logname));
	write(1,"\n\n",2);
#endif
	return logname;
}

extern char ** environ;

char ttybuf[20]="/dev/";
char ttybuf2[25]="TTY=";

int main(int argc,char *argv[])
{
	char *loginargv[]= {"/bin/login", "--", 0, 0};
	char *logname;
	char hostname_end='.';
	int  ii;

	for (ii = 1; ii < argc; ii++) {
		if (argv[ii][0] != '-' || argv[ii][1] == 0) {
			break;
		}
		if (argv[ii][1] == '-' && argv[ii][2] == 0) {
			ii++;
			break;
		}
		for (int jj = 1; argv[ii][jj]; jj++) switch (argv[ii][jj]) {
			case 'H':
				hostname_end = 0;
				break;
			case 'c':
				noclear      = 1;
				break;
			}
nextArgument:
		;
	}

	argv[--ii] = argv[0];
	argc -= ii;
	argv += ii;

	tty = argv[1];
	if (!tty)
		error("usage: getty 1\n"
		      "       getty vc/1\n"
		      "       getty /dev/tty1\n",111);
	if (tty[0]=='/') {
		strncpy(ttybuf, tty, 15);
	} else if (isdigit(tty[0])) {
		struct stat ss;
		/* try prepending /dev/vc/1 and /dev/tty1 */
		strcpy(ttybuf,"/dev/vc/");
		strncpy(ttybuf+8,tty,3);
		if (stat(ttybuf,&ss) && errno==ENOENT) {
			ttybuf[5]=ttybuf[6]='t';
			ttybuf[7]='y';
		}
	} else {
		strncpy(ttybuf+5, tty, 10);
	}
	tty = ttybuf;
	strcpy(ttybuf2+4, ttybuf);

	uname(&uts);
	if (gethostname(hn+5, MAXHOSTNAMELEN)!=0) {
		hn[5]=0;
	}
	hn[5+MAXHOSTNAMELEN]=0;
	putenv("TERM=linux");
	putenv(ttybuf2);
	putenv(hn);
	time(&cur_time);
	while (hn[hn_len]!=0 && hn[hn_len]!=hostname_end) {
		++hn_len;
	}
#ifndef DEBUG
	doutmp();
	open_tty();
#endif
	ioctl(0, TCFLSH, 2);	/* mingetty says this is important for modem users */
	/*while ((logname=get_logname()) == 0);
	if (logname[0]=='-') {
		error("username may not start with a dash\n",13);
	}
	loginargv[2] = logname;*/
	loginargv[2] = "berry";
	echo_off();
	execve("/usr/sbin/berry-dm", loginargv, environ);
//	execve("/bin/login", loginargv, environ);
	exit(8);
}