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	su.c - ubase - suckless linux base utils
	git clone git://git.suckless.org/ubase
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	---
	su.c (2052B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include <sys/types.h>
	3
	4 #include <errno.h>
	5 #include <grp.h>
	6 #include <pwd.h>
	7 #include <stdio.h>
	8 #include <stdlib.h>
	9 #include <string.h>
	10 #include <unistd.h>
	11
	12 #include "passwd.h"
	13 #include "util.h"
	14
	15 extern char **environ;
	16
	17 static int lflag = 0;
	18 static int pflag = 0;
	19
	20 static void
	21 usage(void)
	22 {
	23 eprintf("usage: %s [-lp] [username]\n", argv0);
	24 }
	25
	26 int
	27 main(int argc, char *argv[])
	28 {
	29 char usr, pass;
	30 char shell, envshell, *term;
	31 struct passwd *pw;
	32 char *newargv[3];
	33 uid_t uid;
	34
	35 ARGBEGIN {
	36 case 'l':
	37 lflag = 1;
	38 break;
	39 case 'p':
	40 pflag = 1;
	41 break;
	42 default:
	43 usage();
	44 } ARGEND;
	45
	46 if (argc > 1)
	47 usage();
	48 usr = argc > 0 ? argv[0] : "root";
	49
	50 errno = 0;
	51 pw = getpwnam(usr);
	52 if (!pw) {
	53 if (errno)
	54 eprintf("getpwnam: %s:", usr);
	55 else
	56 eprintf("who are you?\n");
	57 }
	58
	59 uid = getuid();
	60 if (uid) {
	61 pass = getpass("Password: ");
	62 if (!pass)
	63 eprintf("getpass:");
	64 if (pw_check(pw, pass) <= 0)
	65 exit(1);
	66 }
	67
	68 if (initgroups(usr, pw->pw_gid) < 0)
	69 eprintf("initgroups:");
	70 if (setgid(pw->pw_gid) < 0)
	71 eprintf("setgid:");
	72 if (setuid(pw->pw_uid) < 0)
	73 eprintf("setuid:");
	74
	75 shell = pw->pw_shell[0] == '\0' ? "/bin/sh" : pw->pw_shell;
	76 if (lflag) {
	77 term = getenv("TERM");
	78 clearenv();
	79 setenv("HOME", pw->pw_dir, 1);
	80 setenv("SHELL", shell, 1);
	81 setenv("USER", pw->pw_name, 1);
	82 setenv("LOGNAME", pw->pw_name, 1);
	83 setenv("TERM", term ? term : "linux", 1);
	84 if (chdir(pw->pw_dir) < 0)
	85 eprintf("chdir %s:", pw->pw_dir);
	86 newargv[0] = shell;
	87 newargv[1] = "-l";
	88 newargv[2] = NULL;
	89 } else {
	90 if (pflag) {
	91 envshell = getenv("SHELL");
	92 if (envshell && envshell[0] != '\0')
	93 shell = envshell;
	94 } else {
	95 setenv("HOME", pw->pw_dir, 1);
	96 setenv("SHELL", shell, 1);
	97 if (strcmp(pw->pw_name, "root") != 0) {
	98 setenv("USER", pw->pw_name, 1);
	99 setenv("LOGNAME", pw->pw_name, 1);
	100 }
	101 }
	102 newargv[0] = shell;
	103 newargv[1] = NULL;
	104 }
	105 execve(shell, newargv, environ);
	106 weprintf("execve %s:", shell);
	107 return (errno == ENOENT) ? 127 : 126;
	108 }