crypto/dist/heimdal/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("$Heimdal: login_access.c 10020 2001-06-04 14:10:19Z assar $"
  29         "$NetBSD$");
  30
  31  /* Delimiters for fields and for lists of users, ttys or hosts. */
  32
  33 static char fs[] = ":";                 /* field separator */
  34 static char sep[] = ", \t";             /* list-element separator */
  35
  36  /* Constants to be used in assignments only, not in comparisons... */
  37
  38 #define YES             1
  39 #define NO              0
  40
  41  /*
  42   * A structure to bundle up all login-related information to keep the
  43   * functional interfaces as generic as possible.
  44   */
  45 struct login_info {
  46     struct passwd *user;
  47     char   *from;
  48 };
  49
  50 static int list_match(char *list, struct login_info *item,
  51                       int (*match_fn)(char *, struct login_info *));
  52 static int user_match(char *tok, struct login_info *item);
  53 static int from_match(char *tok, struct login_info *item);
  54 static int string_match(char *tok, char *string);
  55
  56 /* login_access - match username/group and host/tty with access control file */
  57
  58 int login_access(struct passwd *user, char *from)
  59 {
  60     struct login_info item;
  61     FILE   *fp;
  62     char    line[BUFSIZ];
  63     char   *perm;                       /* becomes permission field */
  64     char   *users;                      /* becomes list of login names */
  65     char   *froms;                      /* becomes list of terminals or hosts */
  66     int     match = NO;
  67     int     end;
  68     int     lineno = 0;                 /* for diagnostics */
  69     char   *foo;
  70
  71     /*
  72      * Bundle up the arguments to avoid unnecessary clumsiness lateron.
  73      */
  74     item.user = user;
  75     item.from = from;
  76
  77     /*
  78      * Process the table one line at a time and stop at the first match.
  79      * Blank lines and lines that begin with a '#' character are ignored.
  80      * Non-comment lines are broken at the ':' character. All fields are
  81      * mandatory. The first field should be a "+" or "-" character. A
  82      * non-existing table means no access control.
  83      */
  84
  85     if ((fp = fopen(_PATH_LOGACCESS, "r")) != 0) {
  86         while (!match && fgets(line, sizeof(line), fp)) {
  87             lineno++;
  88             if (line[end = strlen(line) - 1] != '\n') {
  89                 syslog(LOG_ERR, "%s: line %d: missing newline or line too long",
  90                        _PATH_LOGACCESS, lineno);
  91                 continue;
  92             }
  93             if (line[0] == '#')
  94                 continue;                       /* comment line */
  95             while (end > 0 && isspace((unsigned char)line[end - 1]))
  96                 end--;
  97             line[end] = 0;                      /* strip trailing whitespace */
  98             if (line[0] == 0)                   /* skip blank lines */
  99                 continue;
 100             foo = NULL;
 101             if (!(perm = strtok_r(line, fs, &foo))
 102                 || !(users = strtok_r(NULL, fs, &foo))
 103                 || !(froms = strtok_r(NULL, fs, &foo))
 104                 || strtok_r(NULL, fs, &foo)) {
 105                 syslog(LOG_ERR, "%s: line %d: bad field count",
 106                        _PATH_LOGACCESS,
 107                        lineno);
 108                 continue;
 109             }
 110             if (perm[0] != '+' && perm[0] != '-') {
 111                 syslog(LOG_ERR, "%s: line %d: bad first field",
 112                        _PATH_LOGACCESS,
 113                        lineno);
 114                 continue;
 115             }
 116             match = (list_match(froms, &item, from_match)
 117                      && list_match(users, &item, user_match));
 118         }
 119         fclose(fp);
 120     } else if (errno != ENOENT) {
 121         syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS);
 122     }
 123     return (match == 0 || (line[0] == '+'));
 124 }
 125
 126 /* list_match - match an item against a list of tokens with exceptions */
 127
 128 static int
 129 list_match(char *list,
 130            struct login_info *item,
 131            int (*match_fn)(char *, struct login_info *))
 132 {
 133     char   *tok;
 134     int     match = NO;
 135     char   *foo = NULL;
 136
 137     /*
 138      * Process tokens one at a time. We have exhausted all possible matches
 139      * when we reach an "EXCEPT" token or the end of the list. If we do find
 140      * a match, look for an "EXCEPT" list and recurse to determine whether
 141      * the match is affected by any exceptions.
 142      */
 143
 144     for (tok = strtok_r(list, sep, &foo);
 145          tok != NULL;
 146          tok = strtok_r(NULL, sep, &foo)) {
 147         if (strcasecmp(tok, "EXCEPT") == 0)     /* EXCEPT: give up */
 148             break;
 149         if ((match = (*match_fn) (tok, item)) != 0)     /* YES */
 150             break;
 151     }
 152     /* Process exceptions to matches. */
 153
 154     if (match != NO) {
 155         while ((tok = strtok_r(NULL, sep, &foo)) && strcasecmp(tok, "EXCEPT"))
 156              /* VOID */ ;
 157         if (tok == 0 || list_match(NULL, item, match_fn) == NO)
 158             return (match);
 159     }
 160     return (NO);
 161 }
 162
 163 /* myhostname - figure out local machine name */
 164
 165 static char *myhostname(void)
 166 {
 167     static char name[MAXHOSTNAMELEN + 1] = "";
 168
 169     if (name[0] == 0) {
 170         gethostname(name, sizeof(name));
 171         name[MAXHOSTNAMELEN] = 0;
 172     }
 173     return (name);
 174 }
 175
 176 /* netgroup_match - match group against machine or user */
 177
 178 static int netgroup_match(char *group, char *machine, char *user)
 179 {
 180 #ifdef HAVE_YP_GET_DEFAULT_DOMAIN
 181     static char *mydomain = 0;
 182
 183     if (mydomain == 0)
 184         yp_get_default_domain(&mydomain);
 185     return (innetgr(group, machine, user, mydomain));
 186 #else
 187     syslog(LOG_ERR, "NIS netgroup support not configured");
 188     return 0;
 189 #endif
 190 }
 191
 192 /* user_match - match a username against one token */
 193
 194 static int user_match(char *tok, struct login_info *item)
 195 {
 196     char   *string = item->user->pw_name;
 197     struct login_info fake_item;
 198     struct group *group;
 199     int     i;
 200     char   *at;
 201
 202     /*
 203      * If a token has the magic value "ALL" the match always succeeds.
 204      * Otherwise, return YES if the token fully matches the username, if the
 205      * token is a group that contains the username, or if the token is the
 206      * name of the user's primary group.
 207      */
 208
 209     if ((at = strchr(tok + 1, '@')) != 0) {     /* split user@host pattern */
 210         *at = 0;
 211         fake_item.from = myhostname();
 212         return (user_match(tok, item) && from_match(at + 1, &fake_item));
 213     } else if (tok[0] == '@') {                 /* netgroup */
 214         return (netgroup_match(tok + 1, (char *) 0, string));
 215     } else if (string_match(tok, string)) {     /* ALL or exact match */
 216         return (YES);
 217     } else if ((group = getgrnam(tok)) != 0) { /* try group membership */
 218         if (item->user->pw_gid == group->gr_gid)
 219             return (YES);
 220         for (i = 0; group->gr_mem[i]; i++)
 221             if (strcasecmp(string, group->gr_mem[i]) == 0)
 222                 return (YES);
 223     }
 224     return (NO);
 225 }
 226
 227 /* from_match - match a host or tty against a list of tokens */
 228
 229 static int from_match(char *tok, struct login_info *item)
 230 {
 231     char   *string = item->from;
 232     int     tok_len;
 233     int     str_len;
 234
 235     /*
 236      * If a token has the magic value "ALL" the match always succeeds. Return
 237      * YES if the token fully matches the string. If the token is a domain
 238      * name, return YES if it matches the last fields of the string. If the
 239      * token has the magic value "LOCAL", return YES if the string does not
 240      * contain a "." character. If the token is a network number, return YES
 241      * if it matches the head of the string.
 242      */
 243
 244     if (tok[0] == '@') {                        /* netgroup */
 245         return (netgroup_match(tok + 1, string, (char *) 0));
 246     } else if (string_match(tok, string)) {     /* ALL or exact match */
 247         return (YES);
 248     } else if (tok[0] == '.') {                 /* domain: match last fields */
 249         if ((str_len = strlen(string)) > (tok_len = strlen(tok))
 250             && strcasecmp(tok, string + str_len - tok_len) == 0)
 251             return (YES);
 252     } else if (strcasecmp(tok, "LOCAL") == 0) { /* local: no dots */
 253         if (strchr(string, '.') == 0)
 254             return (YES);
 255     } else if (tok[(tok_len = strlen(tok)) - 1] == '.'  /* network */
 256                && strncmp(tok, string, tok_len) == 0) {
 257         return (YES);
 258     }
 259     return (NO);
 260 }
 261
 262 /* string_match - match a string against one token */
 263
 264 static int string_match(char *tok, char *string)
 265 {
 266
 267     /*
 268      * If the token has the magic value "ALL" the match always succeeds.
 269      * Otherwise, return YES if the token fully matches the string.
 270      */
 271
 272     if (strcasecmp(tok, "ALL") == 0) {          /* all: always matches */
 273         return (YES);
 274     } else if (strcasecmp(tok, string) == 0) {  /* try exact match */
 275         return (YES);
 276     }
 277     return (NO);
 278 }