login-utils/islocal.c

   1 /*
   2  * islocal.c - returns true if user is registered in the local
   3  * /etc/passwd file. Written by Álvaro Martínez 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 Miśkiewicz <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 "closestream.h"
  26 #include "islocal.h"
  27 #include "nls.h"
  28 #include "pathnames.h"
  29
  30 static int is_local_in_file(const char *user, const char *filename)
  31 {
  32         int local = 0;
  33         size_t match;
  34         int chin, skip;
  35         FILE *f;
  36
  37         if (NULL == (f = fopen(filename, "r")))
  38                 return -1;
  39
  40         match = 0u;
  41         skip = 0;
  42         while ((chin = getc(f)) != EOF) {
  43                 if (skip) {
  44                         /* Looking for the start of the next line. */
  45                         if ('\n' == chin) {
  46                                 /* Start matching username at the next char. */
  47                                 skip = 0;
  48                                 match = 0u;
  49                         }
  50                 } else {
  51                         if (':' == chin) {
  52                                 if (0 == user[match]) {
  53                                         /* Success. */
  54                                         local = 1;
  55                                         /* next line has no test coverage,
  56                                          * but it is just an optimisation
  57                                          * anyway.  */
  58                                         break;
  59                                 } else {
  60                                         /* we read a whole username, but it
  61                                          * is the wrong user.  Skip to the
  62                                          * next line.  */
  63                                         skip = 1;
  64                                 }
  65                         } else if ('\n' == chin) {
  66                                 /* This line contains no colon; it's
  67                                  * malformed.  No skip since we are already
  68                                  * at the start of the next line.  */
  69                                 match = 0u;
  70                         } else if (chin != user[match]) {
  71                                 /* username does not match. */
  72                                 skip = 1;
  73                         } else {
  74                                 ++match;
  75                         }
  76                 }
  77         }
  78         fclose(f);
  79         return local;
  80 }
  81
  82 int is_local(const char *user)
  83 {
  84         int rv;
  85
  86         if ((rv = is_local_in_file(user, _PATH_PASSWD)) < 0)
  87                 err(EXIT_FAILURE, _("cannot open %s"), _PATH_PASSWD);
  88         return rv;
  89 }
  90
  91 #ifdef TEST_PROGRAM
  92 int main(int argc, char *argv[])
  93 {
  94         close_stdout_atexit();
  95         if (argc <= 2) {
  96                 fprintf(stderr, _("Usage: %s <passwordfile> <username>...\n"),
  97                         argv[0]);
  98                 return 1;
  99         } else {
 100                 int i;
 101                 for (i = 2; i < argc; i++) {
 102                         const int rv = is_local_in_file(argv[i], argv[1]);
 103                         if (rv < 0) {
 104                                 perror(argv[1]);
 105                                 return 2;
 106                         }
 107                         printf("%d:%s\n", rv, argv[i]);
 108                 }
 109                 return 0;
 110         }
 111 }
 112 #endif