users.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include <ctype.h>
   5 #include <sys/stat.h>
   6 #include <unistd.h>
   7 #include "log.h"
   8 #include "users.h"
   9
  10 #define USERS_FILE "./users"
  11
  12
  13 static int check_user_name (const char *name)
  14 {
  15         int i;
  16
  17
  18         if (!isalpha(name[0])) return 0;
  19
  20         for (i = 1; name[i] != 0; i++)
  21         {
  22                 if (!isalnum(name[i])) return 0;
  23         }
  24
  25         // minimal length
  26         return i >= 3;
  27 }
  28
  29
  30
  31 /*
  32  * str must be 0-terminated
  33  * NB! content of str will be destroyed in the process
  34  */
  35 static int parse_user (user *usr, char *str)
  36 {
  37         char *s;
  38         if ((s = strstr(str, ":")) == NULL) return 0;
  39         *s = 0;
  40
  41         // id
  42         usr->id = atoi(str);
  43
  44         str = s + 1;
  45         if ((s = strstr(str, ":")) == NULL) return 0;
  46         *s = 0;
  47
  48         // name
  49         strncpy (usr->name, str, USER_NAME_LEN);
  50         usr->name[USER_NAME_LEN - 1] = 0;
  51
  52         str = s + 1;
  53         if ((s = strstr(str, ":")) == NULL) return 0;
  54         *s = 0;
  55
  56         // password
  57         strncpy (usr->pass, str, USER_PASS_LEN);
  58         usr->name[USER_PASS_LEN - 1] = 0;
  59
  60         str = s + 1;
  61         if ((s = strstr(str, "\n")) != NULL) *s = 0;    // remove optional \n at the end
  62
  63         // email
  64         strncpy (usr->email, str, USER_EMAIL_LEN);
  65         usr->name[USER_EMAIL_LEN - 1] = 0;
  66
  67         return 1;
  68 }
  69
  70
  71
  72 #define BUF_SZ  1024
  73
  74 /*
  75  * if user is not found usr will be filled with garbage
  76  *      and also if max_id is not NULL, it will contain max encountered user id
  77  */
  78 static int find_user (const char *name, user *usr, FILE *f, int *max_id)
  79 {
  80         int m = 0;
  81
  82         while (1)
  83         {
  84                 char buf[BUF_SZ];
  85
  86                 // end of file
  87                 if (fgets(buf, BUF_SZ, f) == NULL) break;
  88
  89                 // skip comments and empty lines
  90                 if (buf[0] == '#' || buf[0] == 0) continue;
  91
  92                 if (!parse_user(usr, buf))
  93                 {
  94                         continue;
  95                 }
  96
  97                 // logins are case-insensitive
  98                 if (strcasecmp(name, usr->name) == 0) return usr->id;
  99
 100                 // update max id
 101                 if (usr->id > m) m = usr->id;
 102         }
 103
 104         if (max_id != NULL) *max_id = m;
 105         return 0;
 106 }
 107
 108
 109
 110 static void write_user (FILE *f, const user *usr)
 111 {
 112         fprintf (f, "%d:%s:%s:%s\n", usr->id, usr->name, usr->pass, usr->email);
 113 }
 114
 115
 116
 117 int add_user (user *usr, const char *name, const char *pass, const char *email)
 118 {
 119         int id;
 120         FILE *f;
 121
 122         if (!check_user_name(name)) return -1;
 123
 124         f = fopen(USERS_FILE, "r+");
 125         if (f == NULL)
 126         {
 127                 write_log (LOG_ERROR, "error opening " USERS_FILE);
 128                 return -2;
 129         }
 130
 131         // lock file to block access from other threads
 132         if (lockf(fileno(f), F_LOCK, 0) != 0)
 133         {
 134                 write_log (LOG_ERROR, "error locking " USERS_FILE);
 135                 fclose (f);
 136                 return -3;
 137         }
 138
 139         // user already exists
 140         if (find_user(name, usr, f, &id))
 141         {
 142                 fclose (f);
 143                 return -4;
 144         }
 145
 146         id++;
 147         usr->id = id;
 148
 149         strncpy (usr->name, name, USER_NAME_LEN);
 150         usr->name[USER_NAME_LEN - 1] = 0;
 151
 152         strncpy (usr->pass, pass, USER_PASS_LEN);
 153         usr->pass[USER_PASS_LEN - 1] = 0;
 154
 155         strncpy (usr->email, email, USER_EMAIL_LEN);
 156         usr->email[USER_EMAIL_LEN - 1] = 0;
 157
 158         // add user record to the file
 159         fseek (f, 0, SEEK_END);
 160
 161         write_user (f, usr);
 162
 163         fclose (f);
 164
 165         return id;
 166 }
 167
 168
 169
 170 int check_user_login (user *usr, const char *name, const char *pass)
 171 {
 172         int id;
 173         FILE *f;
 174
 175
 176         f = fopen(USERS_FILE, "r+");    // r+ is needed for locking
 177         if (f == NULL)
 178         {
 179                 write_log (LOG_ERROR, "error opening " USERS_FILE);
 180                 return -2;
 181         }
 182
 183         // lock file to block access from other threads
 184         if (lockf(fileno(f), F_LOCK, 0) != 0)
 185         {
 186                 write_log (LOG_ERROR, "error locking " USERS_FILE);
 187                 fclose (f);
 188                 return -3;
 189         }
 190
 191         id = find_user(name, usr, f, NULL);
 192         fclose (f);
 193
 194         if (id <= 0) return -4;
 195
 196         if (strcmp(pass, usr->pass) != 0) return -5;
 197
 198         return id;
 199 }
 200
 201
 202
 203 static void change_password_save (FILE *f, char *buf, int size, int user_id, const char *pass)
 204 {
 205         char str[BUF_SZ];
 206         char *end = buf + size;
 207
 208
 209         while (buf <= end)
 210         {
 211                 user usr;
 212                 char *s = strstr(buf, "\n");
 213
 214                 if (s == NULL) s = end;
 215                 else *s = 0;
 216
 217                 // copy string (parse_user is destructive)
 218                 snprintf (str, BUF_SZ, buf);
 219
 220                 // not user or not this user
 221                 // just copy the string
 222                 if (!parse_user(&usr, str) || usr.id != user_id)
 223                 {
 224                         fprintf (f, "%s\n", buf);
 225                 }
 226                 // replace password and save user
 227                 else
 228                 {
 229                         strncpy (usr.pass, pass, USER_PASS_LEN);
 230                         usr.pass[USER_PASS_LEN - 1] = 0;
 231                         write_user (f, &usr);
 232                 }
 233
 234                 buf = s + 1;
 235         }
 236 }
 237
 238
 239
 240 int change_password (int user_id, const char *pass)
 241 {
 242         struct stat st;
 243         char *buf;
 244         FILE *f;
 245
 246
 247         f = fopen(USERS_FILE, "r+");
 248         if (f == NULL)
 249         {
 250                 write_log (LOG_ERROR, "error opening " USERS_FILE);
 251                 return -2;
 252         }
 253
 254         // lock file to block access from other threads
 255         if (lockf(fileno(f), F_LOCK, 0) != 0)
 256         {
 257                 write_log (LOG_ERROR, "error locking " USERS_FILE);
 258                 fclose (f);
 259                 return -3;
 260         }
 261
 262         // allocate buffer to store all users
 263
 264         if (fstat(fileno(f), &st) == -1)
 265         {
 266                 write_log (LOG_ERROR, "can't stat " USERS_FILE);
 267                 fclose (f);
 268                 return -4;
 269         }
 270
 271         buf = (char*)malloc(st.st_size);
 272         if (buf == NULL)
 273         {
 274                 write_log (LOG_ERROR, "unable to allocate memory to load " USERS_FILE);
 275                 fclose (f);
 276                 return -5;
 277         }
 278
 279         // read the whole user file into memory
 280         fread (buf, st.st_size, 1, f);
 281
 282         fseek (f, 0, SEEK_SET);
 283         change_password_save (f, buf, st.st_size, user_id, pass);
 284
 285         fclose (f);
 286         free (buf);
 287
 288         return 0;
 289 }
 290