minix/commands/getty/getty.c

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/* getty - get tty speed Author: Fred van Kempen */
/*
* GETTY - Initialize and serve a login-terminal for INIT.
* Also, select the correct speed. The STTY() code
* was taken from stty(1).c; which was written by
* Andrew S. Tanenbaum.
*
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* Usage: getty [speed]
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*
* Version: 3.4 02/17/90
*
* Author: F. van Kempen, MicroWalt Corporation
*
* Modifications:
* All the good stuff removed to get a minimal getty, because
* many modems don't like all that fancy speed detection stuff.
* 03/03/91 Kees J. Bot (kjb@cs.vu.nl)
*
* Uname(), termios. More nonsense removed. (The result has
* only 10% of the original functionality, but a 10x chance of
* working.)
* 12/12/92 Kees J. Bot
*
* Customizable login banner.
* 11/13/95 Kees J. Bot
*
* Suspend/resume signals removed.
* 2001-04-04 Kees J. Bot
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*
* Removed unused custom banner and returned speed option
* functionality (by simply calling stty).
* 2012-09-24 T. Veerman
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*/
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/utsname.h>
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#include <stdio.h>
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char LOGIN[] = "/usr/bin/login";
char SHELL[] = "/bin/sh";
char *tty_name; /* name of the line */
/* Crude indication of a tty being physically secure: */
#define securetty(dev) ((unsigned) ((dev) - 0x0400) < (unsigned) 8)
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void std_out(const char *s)
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{
write(1, s, strlen(s));
}
/* Read one character from stdin.
*/
int readch(void)
{
int st;
char ch1;
/* read character from TTY */
st = read(0, &ch1, 1);
if (st == 0) {
std_out("\n");
exit(0);
}
if (st < 0) {
std_out("getty: ");
std_out(tty_name);
std_out(": read error\n");
exit(1);
}
return(ch1 & 0xFF);
}
/* Handle the process of a GETTY.
*/
void do_getty(char *name, size_t len, char **args, const char *ttyname)
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{
register char *np, *s, *s0;
int ch;
struct utsname utsname;
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char **banner, *t;
static char *def_banner[] = { "%s/%p (%t)\n\n%n login: ", 0 };
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/* Clean up tty name. */
if((t = strrchr(ttyname, '/'))) ttyname = t + 1;
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if (args[0] != NULL) {
char cmd[5+6+1]; /* "stty " + "115200" + '\0' */
int speed;
speed = atoi(args[0]);
snprintf(cmd, sizeof(cmd), "stty %d\n", speed);
system(cmd);
}
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/* Display prompt. */
ch = ' ';
*name = '\0';
while (ch != '\n') {
/* Get data about this machine. */
uname(&utsname);
/* Print the banner. */
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for (banner = def_banner; *banner != NULL; banner++) {
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std_out(banner == args ? "\n" : " ");
s0 = *banner;
for (s = *banner; *s != 0; s++) {
if (*s == '\\') {
write(1, s0, s-s0);
s0 = s+2;
switch (*++s) {
case 'n': std_out("\n"); break;
case 's': std_out(" "); break;
case 't': std_out("\t"); break;
case 0: goto leave;
default: s0 = s;
}
} else
if (*s == '%') {
write(1, s0, s-s0);
s0 = s+2;
switch (*++s) {
case 's': std_out(utsname.sysname); break;
case 'n': std_out(utsname.nodename); break;
case 'r': std_out(utsname.release); break;
case 'v': std_out(utsname.version); break;
case 'm': std_out(utsname.machine); break;
case 'p': std_out(utsname.arch); break;
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case 't': std_out(ttyname); break;
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#if __minix_vmd
case 'k': std_out(utsname.kernel); break;
case 'h': std_out(utsname.hostname); break;
case 'b': std_out(utsname.bus); break;
#endif
case 0: goto leave;
default: s0 = s-1;
}
}
}
leave:
write(1, s0, s-s0);
}
np = name;
while ((ch = readch()) != '\n') {
if (np < name + len) *np++ = ch;
}
*np = '\0';
if (*name == '\0') ch = ' '; /* blank line typed! */
}
}
/* Execute the login(1) command with the current
* username as its argument. It will reply to the
* calling user by typing "Password: "...
*/
void do_login(char *name)
{
struct stat st;
execl(LOGIN, LOGIN, name, (char *) NULL);
/* Failed to exec login. Impossible, but true. Try a shell, but only if
* the terminal is more or less secure, because it will be a root shell.
*/
std_out("getty: can't exec ");
std_out(LOGIN);
std_out("\n");
if (fstat(0, &st) == 0 && S_ISCHR(st.st_mode) && securetty(st.st_rdev)) {
execl(SHELL, SHELL, (char *) NULL);
}
}
int main(int argc, char **argv)
{
char name[30];
struct sigaction sa;
/* Don't let QUIT dump core. */
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_handler = exit;
sigaction(SIGQUIT, &sa, NULL);
tty_name = ttyname(0);
if (tty_name == NULL) {
std_out("getty: tty name unknown\n");
pause();
return(1);
}
chown(tty_name, 0, 0); /* set owner of TTY to root */
chmod(tty_name, 0600); /* mode to max secure */
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do_getty(name, sizeof(name), argv+1, tty_name); /* handle getty() */
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name[29] = '\0'; /* make sure the name fits! */
do_login(name); /* and call login(1) if OK */
return(1); /* never executed */
}