users.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include <ctype.h>
   5 #include <unistd.h>
   6 #include "users.h"
   7
   8 #define USERS_FILE "./users"
   9
  10
  11 static int check_user_name (const char *name)
  12 {
  13         int i;
  14
  15
  16         if (!isalpha(name[i])) return 0;
  17
  18         for (i = 1; name[i] != 0; i++)
  19         {
  20                 if (!isalnum(name[i])) return 0;
  21         }
  22
  23         // minimal length
  24         return i >= 3;
  25 }
  26
  27
  28
  29 /*
  30  * str must be 0-terminated
  31  * NB! content of str will be destroyed in the process
  32  */
  33 static int parse_user (user *usr, char *str)
  34 {
  35         char *s;
  36         if ((s = strstr(str, ":")) == NULL) return 0;
  37         *s = 0;
  38
  39         // id
  40         usr->id = atoi(str);
  41
  42         str = s + 1;
  43         if ((s = strstr(str, ":")) == NULL) return 0;
  44         *s = 0;
  45
  46         // name
  47         strncpy (usr->name, str, USER_NAME_LEN);
  48         usr->name[USER_NAME_LEN - 1] = 0;
  49
  50         str = s + 1;
  51         if ((s = strstr(str, ":")) == NULL) return 0;
  52         *s = 0;
  53
  54         // password
  55         strncpy (usr->pass, str, USER_PASS_LEN);
  56         usr->name[USER_PASS_LEN - 1] = 0;
  57
  58         str = s + 1;
  59         if ((s = strstr(str, "\n")) != NULL) *s = 0;    // remove optional \n at the end
  60
  61         // email
  62         strncpy (usr->email, str, USER_EMAIL_LEN);
  63         usr->name[USER_EMAIL_LEN - 1] = 0;
  64
  65         return 1;
  66 }
  67
  68
  69
  70 #define BUF_SZ  1024
  71
  72 /*
  73  * if user is not found usr will be filled with garbage
  74  *      and also if max_id is not NULL, it will contain max encountered user id
  75  */
  76 static int find_user (const char *name, user *usr, FILE *f, int *max_id)
  77 {
  78         int m = 0;
  79
  80         while (1)
  81         {
  82                 char buf[BUF_SZ];
  83
  84                 // end of file
  85                 if (fgets(buf, BUF_SZ, f) == NULL) break;
  86
  87                 // skip comments and empty lines
  88                 if (buf[0] == '#' || buf[0] == 0) continue;
  89
  90                 if (!parse_user(usr, buf))
  91                 {
  92                         continue;
  93                 }
  94
  95                 // logins are case-insensitive
  96                 if (strcasecmp(name, usr->name) == 0) return usr->id;
  97
  98                 // update max id
  99                 if (usr->id > m) m = usr->id;
 100         }
 101
 102         if (max_id != NULL) *max_id = m;
 103         return 0;
 104 }
 105
 106
 107
 108 int add_user (user *usr, const char *name, const char *pass, const char *email)
 109 {
 110         int id;
 111         FILE *f;
 112
 113         if (!check_user_name(name)) return -1;
 114
 115         f = fopen(USERS_FILE, "r+");
 116         if (f == NULL) return -2;
 117
 118         // lock file to block access from other threads
 119         if (lockf(fileno(f), F_LOCK, 0) != 0)
 120         {
 121                 fclose (f);
 122                 return -3;
 123         }
 124
 125         // user already exists
 126         if (find_user(name, usr, f, &id))
 127         {
 128                 fclose (f);
 129                 return -4;
 130         }
 131
 132         id++;
 133         usr->id = id;
 134
 135         strncpy (usr->name, name, USER_NAME_LEN);
 136         usr->name[USER_NAME_LEN - 1] = 0;
 137
 138         strncpy (usr->pass, pass, USER_PASS_LEN);
 139         usr->pass[USER_PASS_LEN - 1] = 0;
 140
 141         strncpy (usr->email, email, USER_EMAIL_LEN);
 142         usr->email[USER_EMAIL_LEN - 1] = 0;
 143
 144         // add user record to the file
 145         fseek (f, 0, SEEK_END);
 146         fprintf (f, "%d:%s:%s:%s\n", usr->id, usr->name, usr->pass, usr->email);
 147
 148         fclose (f);
 149
 150         return id;
 151 }
 152
 153
 154
 155 int user_login (user *usr, const char *name, const char *pass)
 156 {
 157         int id;
 158         FILE *f;
 159
 160
 161         f = fopen(USERS_FILE, "r+");    // r+ is needed for locking
 162         if (f == NULL) return -2;
 163
 164         // lock file to block access from other threads
 165         if (lockf(fileno(f), F_LOCK, 0) != 0)
 166         {
 167                 fclose (f);
 168                 return -3;
 169         }
 170
 171         id = find_user(name, usr, f, NULL);
 172         fclose (f);
 173
 174         if (id <= 0) return -4;
 175
 176         if (strcmp(pass, usr->pass) != 0) return -5;
 177
 178         return id;
 179 }
 180