su.c - ubase - suckless linux base utils
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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 }