240 lines
6.8 KiB
C
240 lines
6.8 KiB
C
/*
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* This module implements a simple but effective form of login access
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* control based on login names and on host (or domain) names, internet
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* addresses (or network numbers), or on terminal line names in case of
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* non-networked logins. Diagnostics are reported through syslog(3).
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*
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* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
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*/
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#ifdef LOGIN_ACCESS
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#ifndef lint
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static char sccsid[] = "%Z% %M% %I% %E% %U%";
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#endif
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#include <stdio.h>
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#include <syslog.h>
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#include <ctype.h>
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#include <sys/types.h>
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#include <grp.h>
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#include <errno.h>
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#include <string.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include "pathnames.h"
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/* Delimiters for fields and for lists of users, ttys or hosts. */
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static char fs[] = ":"; /* field separator */
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static char sep[] = ", \t"; /* list-element separator */
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/* Constants to be used in assignments only, not in comparisons... */
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#define YES 1
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#define NO 0
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static int list_match();
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static int user_match();
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static int from_match();
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static int string_match();
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/* login_access - match username/group and host/tty with access control file */
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int
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login_access(user, from)
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char *user;
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char *from;
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{
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FILE *fp;
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char line[BUFSIZ];
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char *perm; /* becomes permission field */
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char *users; /* becomes list of login names */
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char *froms; /* becomes list of terminals or hosts */
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int match = NO;
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int end;
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int lineno = 0; /* for diagnostics */
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/*
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* Process the table one line at a time and stop at the first match.
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* Blank lines and lines that begin with a '#' character are ignored.
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* Non-comment lines are broken at the ':' character. All fields are
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* mandatory. The first field should be a "+" or "-" character. A
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* non-existing table means no access control.
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*/
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if ((fp = fopen(_PATH_LOGACCESS, "r")) != NULL) {
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while (!match && fgets(line, sizeof(line), fp)) {
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lineno++;
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if (line[end = strlen(line) - 1] != '\n') {
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syslog(LOG_ERR, "%s: line %d: missing newline or line too long",
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_PATH_LOGACCESS, lineno);
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continue;
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}
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if (line[0] == '#')
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continue; /* comment line */
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while (end > 0 && isspace(line[end - 1]))
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end--;
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line[end] = 0; /* strip trailing whitespace */
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if (line[0] == 0) /* skip blank lines */
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continue;
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if (!(perm = strtok(line, fs))
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|| !(users = strtok((char *) 0, fs))
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|| !(froms = strtok((char *) 0, fs))
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|| strtok((char *) 0, fs)) {
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syslog(LOG_ERR, "%s: line %d: bad field count", _PATH_LOGACCESS,
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lineno);
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continue;
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}
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if (perm[0] != '+' && perm[0] != '-') {
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syslog(LOG_ERR, "%s: line %d: bad first field", _PATH_LOGACCESS,
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lineno);
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continue;
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}
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match = (list_match(froms, from, from_match)
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&& list_match(users, user, user_match));
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}
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(void) fclose(fp);
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} else if (errno != ENOENT) {
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syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS);
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}
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return (match == 0 || (line[0] == '+'));
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}
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/* list_match - match an item against a list of tokens with exceptions */
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static int list_match(list, item, match_fn)
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char *list;
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char *item;
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int (*match_fn) ();
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{
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char *tok;
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int match = NO;
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/*
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* Process tokens one at a time. We have exhausted all possible matches
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* when we reach an "EXCEPT" token or the end of the list. If we do find
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* a match, look for an "EXCEPT" list and recurse to determine whether
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* the match is affected by any exceptions.
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*/
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for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
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if (strcasecmp(tok, "EXCEPT") == 0) /* EXCEPT: give up */
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break;
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if ((match = (*match_fn)(tok, item)) != NULL) /* YES */
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break;
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}
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/* Process exceptions to matches. */
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if (match != NO) {
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while ((tok = strtok((char *) 0, sep)) && strcasecmp(tok, "EXCEPT"))
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/* VOID */ ;
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if (tok == 0 || list_match((char *) 0, item, match_fn) == NO)
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return (match);
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}
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return (NO);
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}
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/* netgroup_match - match group against machine or user */
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static int netgroup_match(group, machine, user)
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gid_t group;
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char *machine;
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char *user;
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{
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#ifdef NIS
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static char *mydomain = 0;
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if (mydomain == 0)
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yp_get_default_domain(&mydomain);
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return (innetgr(group, machine, user, mydomain));
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#else
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syslog(LOG_ERR, "NIS netgroup support not configured");
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return 0;
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#endif
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}
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/* user_match - match a username against one token */
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static int user_match(tok, string)
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char *tok;
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char *string;
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{
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struct group *group;
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int i;
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/*
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* If a token has the magic value "ALL" the match always succeeds.
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* Otherwise, return YES if the token fully matches the username, or if
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* the token is a group that contains the username.
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*/
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if (tok[0] == '@') { /* netgroup */
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return (netgroup_match(tok + 1, (char *) 0, string));
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} else if (string_match(tok, string)) { /* ALL or exact match */
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return (YES);
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} else if ((group = getgrnam(tok)) != NULL) {/* try group membership */
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for (i = 0; group->gr_mem[i]; i++)
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if (strcasecmp(string, group->gr_mem[i]) == 0)
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return (YES);
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}
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return (NO);
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}
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/* from_match - match a host or tty against a list of tokens */
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static int from_match(tok, string)
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char *tok;
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char *string;
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{
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int tok_len;
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int str_len;
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/*
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* If a token has the magic value "ALL" the match always succeeds. Return
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* YES if the token fully matches the string. If the token is a domain
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* name, return YES if it matches the last fields of the string. If the
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* token has the magic value "LOCAL", return YES if the string does not
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* contain a "." character. If the token is a network number, return YES
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* if it matches the head of the string.
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*/
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if (tok[0] == '@') { /* netgroup */
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return (netgroup_match(tok + 1, string, (char *) 0));
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} else if (string_match(tok, string)) { /* ALL or exact match */
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return (YES);
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} else if (tok[0] == '.') { /* domain: match last fields */
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if ((str_len = strlen(string)) > (tok_len = strlen(tok))
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&& strcasecmp(tok, string + str_len - tok_len) == 0)
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return (YES);
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} else if (strcasecmp(tok, "LOCAL") == 0) { /* local: no dots */
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if (strchr(string, '.') == 0)
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return (YES);
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} else if (tok[(tok_len = strlen(tok)) - 1] == '.' /* network */
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&& strncmp(tok, string, tok_len) == 0) {
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return (YES);
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}
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return (NO);
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}
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/* string_match - match a string against one token */
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static int string_match(tok, string)
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char *tok;
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char *string;
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{
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/*
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* If the token has the magic value "ALL" the match always succeeds.
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* Otherwise, return YES if the token fully matches the string.
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*/
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if (strcasecmp(tok, "ALL") == 0) { /* all: always matches */
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return (YES);
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} else if (strcasecmp(tok, string) == 0) { /* try exact match */
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return (YES);
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}
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return (NO);
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}
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#endif /* LOGIN_ACCES */
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