usr.bin/login/login_access.c

   1  /*
   2   * This module implements a simple but effective form of login access
   3   * control based on login names and on host (or domain) names, internet
   4   * addresses (or network numbers), or on terminal line names in case of
   5   * non-networked logins. Diagnostics are reported through syslog(3).
   6   *
   7   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
   8   *
   9   * $DragonFly: src/usr.bin/login/login_access.c,v 1.3 2004/06/19 17:28:28 cpressey Exp $
  10   */
  11
  12 #ifdef LOGIN_ACCESS
  13 #ifndef lint
  14 static const char sccsid[] = "%Z% %M% %I% %E% %U%";
  15 #endif
  16
  17 #include <stdio.h>
  18 #include <syslog.h>
  19 #include <ctype.h>
  20 #include <sys/types.h>
  21 #include <grp.h>
  22 #include <errno.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <stdlib.h>
  26
  27 #include "pathnames.h"
  28
  29  /* Delimiters for fields and for lists of users, ttys or hosts. */
  30
  31 static char fs[] = ":";                 /* field separator */
  32 static char sep[] = ", \t";             /* list-element separator */
  33
  34  /* Constants to be used in assignments only, not in comparisons... */
  35
  36 #define YES             1
  37 #define NO              0
  38
  39 static int list_match();
  40 static int user_match();
  41 static int from_match();
  42 static int string_match();
  43
  44 /* login_access - match username/group and host/tty with access control file */
  45
  46 int
  47 login_access(char *user, char *from)
  48 {
  49     FILE   *fp;
  50     char    line[BUFSIZ];
  51     char   *perm;                       /* becomes permission field */
  52     char   *users;                      /* becomes list of login names */
  53     char   *froms;                      /* becomes list of terminals or hosts */
  54     int     match = NO;
  55     int     end;
  56     int     lineno = 0;                 /* for diagnostics */
  57
  58     /*
  59      * Process the table one line at a time and stop at the first match.
  60      * Blank lines and lines that begin with a '#' character are ignored.
  61      * Non-comment lines are broken at the ':' character. All fields are
  62      * mandatory. The first field should be a "+" or "-" character. A
  63      * non-existing table means no access control.
  64      */
  65
  66     if ((fp = fopen(_PATH_LOGACCESS, "r")) != NULL) {
  67         while (!match && fgets(line, sizeof(line), fp)) {
  68             lineno++;
  69             if (line[end = strlen(line) - 1] != '\n') {
  70                 syslog(LOG_ERR, "%s: line %d: missing newline or line too long",
  71                        _PATH_LOGACCESS, lineno);
  72                 continue;
  73             }
  74             if (line[0] == '#')
  75                 continue;                       /* comment line */
  76             while (end > 0 && isspace(line[end - 1]))
  77                 end--;
  78             line[end] = 0;                      /* strip trailing whitespace */
  79             if (line[0] == 0)                   /* skip blank lines */
  80                 continue;
  81             if (!(perm = strtok(line, fs))
  82                 || !(users = strtok((char *) 0, fs))
  83                 || !(froms = strtok((char *) 0, fs))
  84                 || strtok((char *) 0, fs)) {
  85                 syslog(LOG_ERR, "%s: line %d: bad field count", _PATH_LOGACCESS,
  86                        lineno);
  87                 continue;
  88             }
  89             if (perm[0] != '+' && perm[0] != '-') {
  90                 syslog(LOG_ERR, "%s: line %d: bad first field", _PATH_LOGACCESS,
  91                        lineno);
  92                 continue;
  93             }
  94             match = (list_match(froms, from, from_match)
  95                      && list_match(users, user, user_match));
  96         }
  97         (void) fclose(fp);
  98     } else if (errno != ENOENT) {
  99         syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS);
 100     }
 101     return (match == 0 || (line[0] == '+'));
 102 }
 103
 104 /* list_match - match an item against a list of tokens with exceptions */
 105
 106 static int list_match(char *list, char *item, int (*match_fn)())
 107 {
 108     char   *tok;
 109     int     match = NO;
 110
 111     /*
 112      * Process tokens one at a time. We have exhausted all possible matches
 113      * when we reach an "EXCEPT" token or the end of the list. If we do find
 114      * a match, look for an "EXCEPT" list and recurse to determine whether
 115      * the match is affected by any exceptions.
 116      */
 117
 118     for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
 119         if (strcasecmp(tok, "EXCEPT") == 0)     /* EXCEPT: give up */
 120             break;
 121         if ((match = (*match_fn)(tok, item)) != NULL)   /* YES */
 122             break;
 123     }
 124     /* Process exceptions to matches. */
 125
 126     if (match != NO) {
 127         while ((tok = strtok((char *) 0, sep)) && strcasecmp(tok, "EXCEPT"))
 128              /* VOID */ ;
 129         if (tok == 0 || list_match((char *) 0, item, match_fn) == NO)
 130             return (match);
 131     }
 132     return (NO);
 133 }
 134
 135 /* netgroup_match - match group against machine or user */
 136
 137 static int netgroup_match(char *group, char *machine, char *user)
 138 {
 139 #ifdef NIS
 140     static char *mydomain = 0;
 141
 142     if (mydomain == 0)
 143         yp_get_default_domain(&mydomain);
 144     return (innetgr(group, machine, user, mydomain));
 145 #else
 146     syslog(LOG_ERR, "NIS netgroup support not configured");
 147     return 0;
 148 #endif
 149 }
 150
 151 /* user_match - match a username against one token */
 152
 153 static int user_match(char *tok, char *string)
 154 {
 155     struct group *group;
 156     int     i;
 157
 158     /*
 159      * If a token has the magic value "ALL" the match always succeeds.
 160      * Otherwise, return YES if the token fully matches the username, or if
 161      * the token is a group that contains the username.
 162      */
 163
 164     if (tok[0] == '@') {                        /* netgroup */
 165         return (netgroup_match(tok + 1, (char *) 0, string));
 166     } else if (string_match(tok, string)) {     /* ALL or exact match */
 167         return (YES);
 168     } else if ((group = getgrnam(tok)) != NULL) {/* try group membership */
 169         for (i = 0; group->gr_mem[i]; i++)
 170             if (strcasecmp(string, group->gr_mem[i]) == 0)
 171                 return (YES);
 172     }
 173     return (NO);
 174 }
 175
 176 /* from_match - match a host or tty against a list of tokens */
 177
 178 static int from_match(char *tok, char *string)
 179 {
 180     int     tok_len;
 181     int     str_len;
 182
 183     /*
 184      * If a token has the magic value "ALL" the match always succeeds. Return
 185      * YES if the token fully matches the string. If the token is a domain
 186      * name, return YES if it matches the last fields of the string. If the
 187      * token has the magic value "LOCAL", return YES if the string does not
 188      * contain a "." character. If the token is a network number, return YES
 189      * if it matches the head of the string.
 190      */
 191
 192     if (tok[0] == '@') {                        /* netgroup */
 193         return (netgroup_match(tok + 1, string, (char *) 0));
 194     } else if (string_match(tok, string)) {     /* ALL or exact match */
 195         return (YES);
 196     } else if (tok[0] == '.') {                 /* domain: match last fields */
 197         if ((str_len = strlen(string)) > (tok_len = strlen(tok))
 198             && strcasecmp(tok, string + str_len - tok_len) == 0)
 199             return (YES);
 200     } else if (strcasecmp(tok, "LOCAL") == 0) { /* local: no dots */
 201         if (strchr(string, '.') == 0)
 202             return (YES);
 203     } else if (tok[(tok_len = strlen(tok)) - 1] == '.'  /* network */
 204                && strncmp(tok, string, tok_len) == 0) {
 205         return (YES);
 206     }
 207     return (NO);
 208 }
 209
 210 /* string_match - match a string against one token */
 211
 212 static int string_match(char *tok, char *string)
 213 {
 214
 215     /*
 216      * If the token has the magic value "ALL" the match always succeeds.
 217      * Otherwise, return YES if the token fully matches the string.
 218      */
 219
 220     if (strcasecmp(tok, "ALL") == 0) {          /* all: always matches */
 221         return (YES);
 222     } else if (strcasecmp(tok, string) == 0) {  /* try exact match */
 223         return (YES);
 224     }
 225     return (NO);
 226 }
 227 #endif /* LOGIN_ACCES */