src/get_user_uuid.c

   1 /*
   2
   3 get_user_uuid.c -- get user UUID from passwd file
   4 Copyright (c) 2014 Kyle J. McKay.  All rights reserved.
   5
   6 This program is free software; you can redistribute it and/or
   7 modify it under the terms of the GNU General Public License
   8 as published by the Free Software Foundation; either version 2
   9 of the License, or (at your option) any later version.
  10
  11 This program is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with this program; if not, write to the Free Software
  18 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  19
  20 */
  21
  22 /*
  23   USAGE: get_user_uuid username
  24   Exit code 0 for yes, non-zero for no
  25   If username has a UUID returns yes and echos it to stdout
  26   Wrong number of or bad arguments exits with non-zero
  27   Directly reads compiled in PASSWD_FILE location
  28 */
  29
  30 #ifndef PASSWD_FILE
  31 #error PASSWD_FILE must be defined to a string which is the full pathname to\
  32  the /etc/passwd format file to read
  33 #endif
  34
  35 #include <stdlib.h>
  36 #include <string.h>
  37 #include <stdio.h>
  38
  39 #define BADCHARS ":,# \t\r\n"
  40 #define MAX_LINE_SIZE 16384 /* includes trailing \n and \0 */
  41 #define MAX_NAME_LEN 64
  42
  43 static char linebuffer[MAX_LINE_SIZE];
  44
  45 int is_valid_name(const char *name)
  46 {
  47   size_t len;
  48
  49   if (!name || !*name)
  50     return 0;
  51   len = strlen(name);
  52   if (len > MAX_NAME_LEN || strcspn(name, BADCHARS) != len)
  53     return 0;
  54   return 1;
  55 }
  56
  57 int main(int argc, char *argv[])
  58 {
  59   FILE *passwdfile;
  60   size_t len;
  61
  62   if (argc != 2)
  63     return EXIT_FAILURE;
  64   if (!is_valid_name(argv[1]))
  65     return EXIT_FAILURE;
  66
  67   len = strlen(argv[2]);
  68
  69   passwdfile = fopen(PASSWD_FILE, "r");
  70   if (!passwdfile)
  71     return EXIT_FAILURE;
  72   while (fgets(linebuffer, sizeof(linebuffer)-1, passwdfile)) {
  73     char *trimmed, *uuid;
  74     size_t len = strlen(linebuffer);
  75
  76     if (len >= sizeof(linebuffer) - 2)
  77       return EXIT_FAILURE;
  78     if (len && linebuffer[len-1] == '\n')
  79       linebuffer[--len] = '\0';
  80     trimmed = linebuffer + strspn(linebuffer, " \t");
  81     if (!*trimmed || *trimmed == '#')
  82       continue;
  83     if (trimmed != linebuffer)
  84       return EXIT_FAILURE;
  85     trimmed = strchr(linebuffer, ':');
  86     if (!trimmed)
  87       return EXIT_FAILURE;
  88     *trimmed = '\0';
  89     if (strcmp(linebuffer, argv[1]))
  90       continue; /* not the user we're looking for */
  91     trimmed = strchr(trimmed + 1, ':');
  92     if (!trimmed)
  93       return EXIT_FAILURE;
  94     trimmed = strchr(trimmed + 1, ':');
  95     if (!trimmed)
  96       return EXIT_FAILURE;
  97     trimmed = strchr(trimmed + 1, ':');
  98     if (!trimmed)
  99       return EXIT_FAILURE;
 100     uuid = trimmed;
 101     trimmed = strchr(trimmed + 1, ':');
 102     if (trimmed)
 103       *trimmed = '\0';
 104     uuid = strchr(uuid + 1, ',');
 105     if (!uuid)
 106       return EXIT_FAILURE;
 107     trimmed = strchr(++uuid, ',');
 108     if (trimmed)
 109       *trimmed = '\0';
 110     if (*uuid)
 111       printf("%s\n", uuid);
 112     return *uuid ? EXIT_SUCCESS : EXIT_FAILURE;
 113   }
 114   return EXIT_FAILURE;
 115 }