appl/login/login_access.c

   1 /************************************************************************
   2 * Copyright 1995 by Wietse Venema.  All rights reserved.  Some individual
   3 * files may be covered by other copyrights.
   4 *
   5 * This material was originally written and compiled by Wietse Venema at
   6 * Eindhoven University of Technology, The Netherlands, in 1990, 1991,
   7 * 1992, 1993, 1994 and 1995.
   8 *
   9 * Redistribution and use in source and binary forms, with or without
  10 * modification, are permitted provided that this entire copyright notice
  11 * is duplicated in all such copies.
  12 *
  13 * This software is provided "as is" and without any expressed or implied
  14 * warranties, including, without limitation, the implied warranties of
  15 * merchantibility and fitness for any particular purpose.
  16 ************************************************************************/
  17  /*
  18   * This module implements a simple but effective form of login access
  19   * control based on login names and on host (or domain) names, internet
  20   * addresses (or network numbers), or on terminal line names in case of
  21   * non-networked logins. Diagnostics are reported through syslog(3).
  22   *
  23   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  24   */
  25
  26 #include "login_locl.h"
  27
  28 RCSID("$Id$");
  29
  30  /* Delimiters for fields and for lists of users, ttys or hosts. */
  31
  32 static char fs[] = ":";                 /* field separator */
  33 static char sep[] = ", \t";             /* list-element separator */
  34
  35  /* Constants to be used in assignments only, not in comparisons... */
  36
  37 #define YES             1
  38 #define NO              0
  39
  40  /*
  41   * A structure to bundle up all login-related information to keep the
  42   * functional interfaces as generic as possible.
  43   */
  44 struct login_info {
  45     struct passwd *user;
  46     char   *from;
  47 };
  48
  49 static int list_match(char *list, struct login_info *item,
  50                       int (*match_fn)(char *, struct login_info *));
  51 static int user_match(char *tok, struct login_info *item);
  52 static int from_match(char *tok, struct login_info *item);
  53 static int string_match(char *tok, char *string);
  54
  55 /* login_access - match username/group and host/tty with access control file */
  56
  57 int login_access(struct passwd *user, char *from)
  58 {
  59     struct login_info item;
  60     FILE   *fp;
  61     char    line[BUFSIZ];
  62     char   *perm;                       /* becomes permission field */
  63     char   *users;                      /* becomes list of login names */
  64     char   *froms;                      /* becomes list of terminals or hosts */
  65     int     match = NO;
  66     int     end;
  67     int     lineno = 0;                 /* for diagnostics */
  68     char   *foo;
  69
  70     /*
  71      * Bundle up the arguments to avoid unnecessary clumsiness lateron.
  72      */
  73     item.user = user;
  74     item.from = from;
  75
  76     /*
  77      * Process the table one line at a time and stop at the first match.
  78      * Blank lines and lines that begin with a '#' character are ignored.
  79      * Non-comment lines are broken at the ':' character. All fields are
  80      * mandatory. The first field should be a "+" or "-" character. A
  81      * non-existing table means no access control.
  82      */
  83
  84     if ((fp = fopen(_PATH_LOGACCESS, "r")) != 0) {
  85         while (!match && fgets(line, sizeof(line), fp)) {
  86             lineno++;
  87             if (line[end = strlen(line) - 1] != '\n') {
  88                 syslog(LOG_ERR, "%s: line %d: missing newline or line too long",
  89                        _PATH_LOGACCESS, lineno);
  90                 continue;
  91             }
  92             if (line[0] == '#')
  93                 continue;                       /* comment line */
  94             while (end > 0 && isspace((unsigned char)line[end - 1]))
  95                 end--;
  96             line[end] = 0;                      /* strip trailing whitespace */
  97             if (line[0] == 0)                   /* skip blank lines */
  98                 continue;
  99             foo = NULL;
 100             if (!(perm = strtok_r(line, fs, &foo))
 101                 || !(users = strtok_r(NULL, fs, &foo))
 102                 || !(froms = strtok_r(NULL, fs, &foo))
 103                 || strtok_r(NULL, fs, &foo)) {
 104                 syslog(LOG_ERR, "%s: line %d: bad field count",
 105                        _PATH_LOGACCESS,
 106                        lineno);
 107                 continue;
 108             }
 109             if (perm[0] != '+' && perm[0] != '-') {
 110                 syslog(LOG_ERR, "%s: line %d: bad first field",
 111                        _PATH_LOGACCESS,
 112                        lineno);
 113                 continue;
 114             }
 115             match = (list_match(froms, &item, from_match)
 116                      && list_match(users, &item, user_match));
 117         }
 118         fclose(fp);
 119     } else if (errno != ENOENT) {
 120         syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS);
 121     }
 122     return (match == 0 || (line[0] == '+'));
 123 }
 124
 125 /* list_match - match an item against a list of tokens with exceptions */
 126
 127 static int
 128 list_match(char *list,
 129            struct login_info *item,
 130            int (*match_fn)(char *, struct login_info *))
 131 {
 132     char   *tok;
 133     int     match = NO;
 134     char   *foo = NULL;
 135
 136     /*
 137      * Process tokens one at a time. We have exhausted all possible matches
 138      * when we reach an "EXCEPT" token or the end of the list. If we do find
 139      * a match, look for an "EXCEPT" list and recurse to determine whether
 140      * the match is affected by any exceptions.
 141      */
 142
 143     for (tok = strtok_r(list, sep, &foo);
 144          tok != NULL;
 145          tok = strtok_r(NULL, sep, &foo)) {
 146         if (strcasecmp(tok, "EXCEPT") == 0)     /* EXCEPT: give up */
 147             break;
 148         if ((match = (*match_fn) (tok, item)) != 0)     /* YES */
 149             break;
 150     }
 151     /* Process exceptions to matches. */
 152
 153     if (match != NO) {
 154         while ((tok = strtok_r(NULL, sep, &foo)) && strcasecmp(tok, "EXCEPT"))
 155              /* VOID */ ;
 156         if (tok == 0 || list_match(NULL, item, match_fn) == NO)
 157             return (match);
 158     }
 159     return (NO);
 160 }
 161
 162 /* myhostname - figure out local machine name */
 163
 164 static char *myhostname(void)
 165 {
 166     static char name[MAXHOSTNAMELEN + 1] = "";
 167
 168     if (name[0] == 0) {
 169         gethostname(name, sizeof(name));
 170         name[MAXHOSTNAMELEN] = 0;
 171     }
 172     return (name);
 173 }
 174
 175 /* netgroup_match - match group against machine or user */
 176
 177 static int netgroup_match(char *group, char *machine, char *user)
 178 {
 179 #ifdef HAVE_YP_GET_DEFAULT_DOMAIN
 180     static char *mydomain = 0;
 181
 182     if (mydomain == 0)
 183         yp_get_default_domain(&mydomain);
 184     return (innetgr(group, machine, user, mydomain));
 185 #else
 186     syslog(LOG_ERR, "NIS netgroup support not configured");
 187     return 0;
 188 #endif
 189 }
 190
 191 /* user_match - match a username against one token */
 192
 193 static int user_match(char *tok, struct login_info *item)
 194 {
 195     char   *string = item->user->pw_name;
 196     struct login_info fake_item;
 197     struct group *group;
 198     int     i;
 199     char   *at;
 200
 201     /*
 202      * If a token has the magic value "ALL" the match always succeeds.
 203      * Otherwise, return YES if the token fully matches the username, if the
 204      * token is a group that contains the username, or if the token is the
 205      * name of the user's primary group.
 206      */
 207
 208     if ((at = strchr(tok + 1, '@')) != 0) {     /* split user@host pattern */
 209         *at = 0;
 210         fake_item.from = myhostname();
 211         return (user_match(tok, item) && from_match(at + 1, &fake_item));
 212     } else if (tok[0] == '@') {                 /* netgroup */
 213         return (netgroup_match(tok + 1, (char *) 0, string));
 214     } else if (string_match(tok, string)) {     /* ALL or exact match */
 215         return (YES);
 216     } else if ((group = getgrnam(tok)) != 0) { /* try group membership */
 217         if (item->user->pw_gid == group->gr_gid)
 218             return (YES);
 219         for (i = 0; group->gr_mem[i]; i++)
 220             if (strcasecmp(string, group->gr_mem[i]) == 0)
 221                 return (YES);
 222     }
 223     return (NO);
 224 }
 225
 226 /* from_match - match a host or tty against a list of tokens */
 227
 228 static int from_match(char *tok, struct login_info *item)
 229 {
 230     char   *string = item->from;
 231     int     tok_len;
 232     int     str_len;
 233
 234     /*
 235      * If a token has the magic value "ALL" the match always succeeds. Return
 236      * YES if the token fully matches the string. If the token is a domain
 237      * name, return YES if it matches the last fields of the string. If the
 238      * token has the magic value "LOCAL", return YES if the string does not
 239      * contain a "." character. If the token is a network number, return YES
 240      * if it matches the head of the string.
 241      */
 242
 243     if (tok[0] == '@') {                        /* netgroup */
 244         return (netgroup_match(tok + 1, string, (char *) 0));
 245     } else if (string_match(tok, string)) {     /* ALL or exact match */
 246         return (YES);
 247     } else if (tok[0] == '.') {                 /* domain: match last fields */
 248         if ((str_len = strlen(string)) > (tok_len = strlen(tok))
 249             && strcasecmp(tok, string + str_len - tok_len) == 0)
 250             return (YES);
 251     } else if (strcasecmp(tok, "LOCAL") == 0) { /* local: no dots */
 252         if (strchr(string, '.') == 0)
 253             return (YES);
 254     } else if (tok[(tok_len = strlen(tok)) - 1] == '.'  /* network */
 255                && strncmp(tok, string, tok_len) == 0) {
 256         return (YES);
 257     }
 258     return (NO);
 259 }
 260
 261 /* string_match - match a string against one token */
 262
 263 static int string_match(char *tok, char *string)
 264 {
 265
 266     /*
 267      * If the token has the magic value "ALL" the match always succeeds.
 268      * Otherwise, return YES if the token fully matches the string.
 269      */
 270
 271     if (strcasecmp(tok, "ALL") == 0) {          /* all: always matches */
 272         return (YES);
 273     } else if (strcasecmp(tok, string) == 0) {  /* try exact match */
 274         return (YES);
 275     }
 276     return (NO);
 277 }