busybox/libbb/login.c

/* vi: set sw=4 ts=4: */
/*
 * issue.c: issue printing code
 *
 * Copyright (C) 2003 Bastian Blank <waldi@tuxbox.org>
 *
 * Optimize and correcting OCRNL by Vladimir Oleynik <dzo@simtreas.ru>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
#include "libbb.h"
/* After libbb.h, since it needs sys/types.h on some systems */
#include <sys/utsname.h>

#define LOGIN " login: "

static const char fmtstr_d[] ALIGN1 = "%A, %d %B %Y";

void FAST_FUNC print_login_issue(const char *issue_file, const char *tty)
{
	FILE *fp;
	int c;
	char buf[256+1];
	const char *outbuf;
	time_t t;
	struct utsname uts;

	time(&t);
	uname(&uts);

	puts("\r");  /* start a new line */

	fp = fopen_for_read(issue_file);
	if (!fp)
		return;
	while ((c = fgetc(fp)) != EOF) {
		outbuf = buf;
		buf[0] = c;
		buf[1] = '\0';
		if (c == '\n') {
			buf[1] = '\r';
			buf[2] = '\0';
		}
		if (c == '\\' || c == '%') {
			c = fgetc(fp);
			switch (c) {
//From getty manpage (* - supported by us)
//========================================
//4 or 4{interface}
//  Insert the IPv4 address of the network interface (example: \4{eth0}).
//  If the interface argument is not specified, then select the first
//  fully configured (UP, non-LOOPBACK, RUNNING) interface.
//6 or 6{interface} -- The same as \4 but for IPv6.
//b -- Insert the baudrate of the current line.
//*d -- Insert the current date.
//*t -- Insert the current time.
//e or e{name}
//  Translate the human-readable name to an escape sequence and insert it
//  (for example: \e{red}Alert text.\e{reset}).  If the name argument
//  is not specified, then insert \033. The currently supported names are:
//  black, blink, blue, bold, brown, cyan, darkgray, gray, green, halfbright,
//  lightblue, lightcyan, lightgray, lightgreen, lightmagenta, lightred,
//  magenta, red, reset, reverse, and yellow. Unknown names are ignored.
//*s
//  Insert the system name (the name of the operating system - `uname -s`)
//*S or S{VARIABLE}
//  Insert the VARIABLE data from /etc/os-release.
//  If the VARIABLE argument is not specified, use PRETTY_NAME.
//  If PRETTY_NAME is not in /etc/os-release, \S is the same as \s.
//*l -- Insert the name of the current tty line.
//*m -- Insert the architecture identifier of the machine: `uname -m`.
//*n -- Insert the nodename of the machine: `uname -n`.
//*o -- Insert the NIS domainname of the machine.  Same as `hostname -d'.
//*O -- Insert the DNS domainname of the machine.
//*r -- Insert the release number of the OS: `uname -r`.
//u -- Insert the number of current users logged in.
//U -- Insert the string "1 user" or "N users" (current users logged in).
//*v -- Insert the version of the OS, e.g. the build-date etc: `uname -v`.
//We also implement:
//*D -- same as \O "DNS domainname"
//*h -- same as \n "nodename"

			case 'S':
				/* minimal implementation, not reading /etc/os-release */
				/*FALLTHROUGH*/
			case 's':
				outbuf = uts.sysname;
				break;
			case 'n':
			case 'h':
				outbuf = uts.nodename;
				break;
			case 'r':
				outbuf = uts.release;
				break;
			case 'v':
				outbuf = uts.version;
				break;
			case 'm':
				outbuf = uts.machine;
				break;
/* The field domainname of struct utsname is Linux specific. */
#if defined(__linux__)
			case 'D':
			case 'o':
			case 'O':
				outbuf = uts.domainname;
				break;
#endif
			case 'd':
				strftime(buf, sizeof(buf), fmtstr_d, localtime(&t));
				break;
			case 't':
				strftime_HHMMSS(buf, sizeof(buf), &t);
				break;
			case 'l':
				outbuf = tty;
				break;
			default:
				buf[0] = c;
			}
		}
		fputs_stdout(outbuf);
	}
	fclose(fp);
	fflush_all();
}

void FAST_FUNC print_login_prompt(void)
{
	char *hostname = safe_gethostname();

	fputs_stdout(hostname);
	fputs_stdout(LOGIN);
	fflush_all();
	free(hostname);
}

/* Clear dangerous stuff, set PATH */
static const char forbid[] ALIGN1 =
	"ENV" "\0"
	"BASH_ENV" "\0"
	"HOME" "\0"
	"IFS" "\0"
	"SHELL" "\0"
	"LD_LIBRARY_PATH" "\0"
	"LD_PRELOAD" "\0"
	"LD_TRACE_LOADED_OBJECTS" "\0"
	"LD_BIND_NOW" "\0"
	"LD_AOUT_LIBRARY_PATH" "\0"
	"LD_AOUT_PRELOAD" "\0"
	"LD_NOWARN" "\0"
	"LD_KEEPDIR" "\0";

int FAST_FUNC sanitize_env_if_suid(void)
{
	const char *p;

	if (getuid() == geteuid())
		return 0;

	p = forbid;
	do {
		unsetenv(p);
		p += strlen(p) + 1;
	} while (*p);
	putenv((char*)bb_PATH_root_path);

	return 1; /* we indeed were run by different user! */
}