login-utils/islocal.c

   1 /*
   2  * islocal.c - returns true if user is registered in the local
   3  * /etc/passwd file. Written by Alvaro Martinez Echevarria,
   4  * alvaro@enano.etsit.upm.es, to allow peaceful coexistence with yp. Nov 94.
   5  *
   6  * Hacked a bit by poe@daimi.aau.dk
   7  * See also ftp://ftp.daimi.aau.dk/pub/linux/poe/admutil*
   8  *
   9  * Hacked by Peter Breitenlohner, peb@mppmu.mpg.de,
  10  *   to distinguish user names where one is a prefix of the other,
  11  *   and to use "pathnames.h". Oct 5, 96.
  12  *
  13  * 1999-02-22 Arkadiusz Mi¶kiewicz <misiek@pld.ORG.PL>
  14  * - added Native Language Support
  15  *
  16  * 2008-04-06 James Youngman, jay@gnu.org
  17  * - Completely rewritten to remove assumption that /etc/passwd
  18  *   lines are < 1024 characters long.  Also added unit tests.
  19  */
  20
  21 #include <stddef.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24
  25 #include "islocal.h"
  26 #include "nls.h"
  27 #include "pathnames.h"
  28
  29 static int is_local_in_file(const char *user, const char *filename)
  30 {
  31         int local = 0;
  32         size_t match;
  33         int chin, skip;
  34         FILE *f;
  35
  36         if (NULL == (f = fopen(filename, "r")))
  37                 return -1;
  38
  39         match = 0u;
  40         skip = 0;
  41         while ((chin = getc(f)) != EOF) {
  42                 if (skip) {
  43                         /* Looking for the start of the next line. */
  44                         if ('\n' == chin) {
  45                                 /* Start matching username at the next char. */
  46                                 skip = 0;
  47                                 match = 0u;
  48                         }
  49                 } else {
  50                         if (':' == chin) {
  51                                 if (0 == user[match]) {
  52                                         /* Success. */
  53                                         local = 1;
  54                                         /* next line has no test coverage,
  55                                          * but it is just an optimisation
  56                                          * anyway.  */
  57                                         break;
  58                                 } else {
  59                                         /* we read a whole username, but it
  60                                          * is the wrong user.  Skip to the
  61                                          * next line.  */
  62                                         skip = 1;
  63                                 }
  64                         } else if ('\n' == chin) {
  65                                 /* This line contains no colon; it's
  66                                  * malformed.  No skip since we are already
  67                                  * at the start of the next line.  */
  68                                 match = 0u;
  69                         } else if (chin != user[match]) {
  70                                 /* username does not match. */
  71                                 skip = 1;
  72                         } else {
  73                                 ++match;
  74                         }
  75                 }
  76         }
  77         fclose(f);
  78         return local;
  79 }
  80
  81 int is_local(const char *user)
  82 {
  83         int rv;
  84         if ((rv = is_local_in_file(user, _PATH_PASSWD)) < 0) {
  85                 perror(_PATH_PASSWD);
  86                 fprintf(stderr, _("Failed to open %s for reading, exiting."),
  87                         _PATH_PASSWD);
  88                 exit(1);
  89         } else {
  90                 return rv;
  91         }
  92 }
  93
  94 #ifdef TEST_PROGRAM
  95 int main(int argc, char *argv[])
  96 {
  97         if (argc <= 2) {
  98                 fprintf(stderr, "usage: %s <passwdfile> <username> [...]\n",
  99                         argv[0]);
 100                 return 1;
 101         } else {
 102                 int i;
 103                 for (i = 2; i < argc; i++) {
 104                         const int rv = is_local_in_file(argv[i], argv[1]);
 105                         if (rv < 0) {
 106                                 perror(argv[1]);
 107                                 return 2;
 108                         }
 109                         printf("%d:%s\n", rv, argv[i]);
 110                 }
 111                 return 0;
 112         }
 113 }
 114 #endif