commands/simple/passwd.c

   1 /* passwd - change a passwd                     Author: Adri Koppes */
   2
   3 /* chfn, chsh - change full name, shell         Added by: Kees J. Bot */
   4
   5 #include <sys/types.h>
   6 #include <fcntl.h>
   7 #include <string.h>
   8 #include <signal.h>
   9 #include <pwd.h>
  10 #include <errno.h>
  11 #include <stdlib.h>
  12 #include <unistd.h>
  13 #include <time.h>
  14 #include <sys/stat.h>
  15 #include <minix/minlib.h>
  16 #include <stdio.h>
  17
  18 _PROTOTYPE(void report, (char *label));
  19 _PROTOTYPE(void quit, (int ex_stat));
  20 _PROTOTYPE(void fatal, (char *label));
  21 _PROTOTYPE(void usage, (void));
  22 _PROTOTYPE(int goodchars, (char *s));
  23 _PROTOTYPE(int main, (int argc, char **argv));
  24
  25 char pw_file[] = "/etc/passwd";
  26 char sh_file[] = "/etc/shadow";
  27 char pw_tmp[] = "/etc/ptmp";
  28 char bad[] = "Permission denied\n";
  29 char buf[1024];
  30
  31 enum action {
  32   PASSWD, CHFN, CHSH
  33 } action = PASSWD;
  34
  35 char *arg0;
  36
  37 void report(label)
  38 char *label;
  39 {
  40   int e = errno;
  41   fprintf(stderr, "%s: ", arg0);
  42   fflush(stderr);
  43   errno = e;
  44   perror(label);
  45 }
  46
  47 void quit(ex_stat)
  48 int ex_stat;
  49 {
  50   if (unlink(pw_tmp) < 0 && errno != ENOENT) {
  51         report(pw_tmp);
  52         ex_stat = 1;
  53   }
  54   exit(ex_stat);
  55 }
  56
  57 void fatal(label)
  58 char *label;
  59 {
  60   report(label);
  61   quit(1);
  62 }
  63
  64 void usage()
  65 {
  66   static char *usages[] = {
  67         "passwd [user]\n",
  68         "chfn [user] fullname\n",
  69         "chsh [user] shell\n"
  70   };
  71   std_err(usages[(int) action]);
  72   exit(1);
  73 }
  74
  75 int goodchars(s)
  76 char *s;
  77 {
  78   int c;
  79
  80   while ((c = *s++) != 0) {
  81         if (c == ':' || c < ' ' || c >= 127) return(0);
  82   }
  83   return(1);
  84 }
  85
  86 int main(argc, argv)
  87 int argc;
  88 char *argv[];
  89 {
  90   int uid, cn, n;
  91   int fd_pwd, fd_tmp;
  92   FILE *fp_tmp;
  93   time_t salt;
  94   struct passwd *pwd;
  95   char *name, pwname[9], oldpwd[9], newpwd[9], newcrypted[14], sl[2];
  96   char *argn;
  97   int shadow = 0;
  98
  99   if ((arg0 = strrchr(argv[0], '/')) != 0)
 100         arg0++;
 101   else
 102         arg0 = argv[0];
 103
 104   if (strcmp(arg0, "chfn") == 0)
 105         action = CHFN;
 106   else if (strcmp(arg0, "chsh") == 0)
 107         action = CHSH;
 108
 109   uid = getuid();
 110
 111   n = action == PASSWD ? 1 : 2;
 112
 113   if (argc != n && argc != n + 1) usage();
 114
 115   if (argc == n) {
 116         pwd = getpwuid(uid);
 117         strcpy(pwname, pwd->pw_name);
 118         name = pwname;
 119   } else {
 120         name = argv[1];
 121         pwd = getpwnam(name);
 122   }
 123   if (pwd == NULL || ((uid != pwd->pw_uid) && uid != 0)) {
 124         std_err(bad);
 125         exit(1);
 126   }
 127
 128   switch (action) {
 129       case PASSWD:
 130         if (pwd->pw_passwd[0] == '#' && pwd->pw_passwd[1] == '#') {
 131                 /* The password is found in the shadow password file. */
 132                 shadow = 1;
 133                 strncpy(pwname, pwd->pw_passwd + 2, 8);
 134                 pwname[8] = 0;
 135                 name = pwname;
 136                 setpwfile(sh_file);
 137                 if ((pwd= getpwnam(name)) == NULL) {
 138                         std_err(bad);
 139                         exit(1);
 140                 }
 141                 printf("Changing the shadow password of %s\n", name);
 142         } else {
 143                 printf("Changing the password of %s\n", name);
 144         }
 145
 146         oldpwd[0] = 0;
 147         if (pwd->pw_passwd[0] != '\0' && uid != 0) {
 148                 strcpy(oldpwd, getpass("Old password:"));
 149                 if (strcmp(pwd->pw_passwd, crypt(oldpwd, pwd->pw_passwd)) != 0)
 150                 {
 151                         std_err(bad);
 152                         exit(1);
 153                 }
 154         }
 155         for (;;) {
 156                 strcpy(newpwd, getpass("New password:"));
 157
 158                 if (newpwd[0] == '\0')
 159                         std_err("Password cannot be null");
 160                 else if (strcmp(newpwd, getpass("Retype password:")) != 0)
 161                         std_err("Passwords don't match");
 162                 else
 163                         break;
 164
 165                 std_err(", try again\n");
 166         }
 167         time(&salt);
 168         sl[0] = (salt & 077) + '.';
 169         sl[1] = ((salt >> 6) & 077) + '.';
 170         for (cn = 0; cn < 2; cn++) {
 171                 if (sl[cn] > '9') sl[cn] += 7;
 172                 if (sl[cn] > 'Z') sl[cn] += 6;
 173         }
 174         strcpy(newcrypted, crypt(newpwd, sl));
 175         break;
 176
 177       case CHFN:
 178       case CHSH:
 179         argn = argv[argc - 1];
 180
 181         if (strlen(argn) > (action == CHFN ? 80 : 60) || !goodchars(argn)) {
 182                 std_err(bad);
 183                 exit(1);
 184         }
 185   }
 186
 187   signal(SIGHUP, SIG_IGN);
 188   signal(SIGINT, SIG_IGN);
 189   signal(SIGQUIT, SIG_IGN);
 190   signal(SIGTERM, SIG_IGN);
 191
 192   umask(0);
 193   n = 10;
 194   while ((fd_tmp = open(pw_tmp, O_RDWR | O_CREAT | O_EXCL, 0400)) < 0) {
 195         if (errno != EEXIST) fatal("Can't create temporary file");
 196
 197         if (n-- > 0) {
 198                 sleep(2);
 199         } else {
 200                 fprintf(stderr, "Password file busy, try again later.\n");
 201                 exit(1);
 202         }
 203   }
 204
 205   if ((fp_tmp = fdopen(fd_tmp, "w+")) == NULL) fatal(pw_tmp);
 206
 207   setpwent();
 208   while ((pwd = getpwent()) != 0) {
 209         if (strcmp(name, pwd->pw_name) == 0) {
 210                 switch (action) {
 211                     case PASSWD:
 212                         pwd->pw_passwd = newcrypted;
 213                         break;
 214                     case CHFN:
 215                         pwd->pw_gecos = argn;
 216                         break;
 217                     case CHSH:
 218                         pwd->pw_shell = argn;
 219                         break;
 220                 }
 221         }
 222         if (strcmp(pwd->pw_shell, "/bin/sh") == 0
 223                 || strcmp(pwd->pw_shell, "/usr/bin/sh") == 0
 224         )
 225                 pwd->pw_shell = "";
 226
 227         fprintf(fp_tmp, "%s:%s:%s:",
 228                 pwd->pw_name,
 229                 pwd->pw_passwd,
 230                 itoa(pwd->pw_uid)
 231         );
 232         if (ferror(fp_tmp)) fatal(pw_tmp);
 233
 234         fprintf(fp_tmp, "%s:%s:%s:%s\n",
 235                 itoa(pwd->pw_gid),
 236                 pwd->pw_gecos,
 237                 pwd->pw_dir,
 238                 pwd->pw_shell
 239         );
 240         if (ferror(fp_tmp)) fatal(pw_tmp);
 241   }
 242   endpwent();
 243   if (fflush(fp_tmp) == EOF) fatal(pw_tmp);
 244
 245   if (lseek(fd_tmp, (off_t) 0, SEEK_SET) != 0)
 246         fatal("Can't reread temp file");
 247
 248   if ((fd_pwd = open(shadow ? sh_file : pw_file, O_WRONLY | O_TRUNC)) < 0)
 249         fatal("Can't recreate password file");
 250
 251   while ((n = read(fd_tmp, buf, sizeof(buf))) != 0) {
 252         if (n < 0 || write(fd_pwd, buf, n) != n) {
 253                 report("Error rewriting password file, tell root!");
 254                 exit(1);
 255         }
 256   }
 257   close(fd_tmp);
 258   close(fd_pwd);
 259   quit(0);
 260 }