262 lines
7.9 KiB
C
262 lines
7.9 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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#include "login_locl.h"
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RCSID("$Id: login_access.c,v 1.1 1999/05/17 22:40:05 assar Exp $");
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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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/*
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* A structure to bundle up all login-related information to keep the
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* functional interfaces as generic as possible.
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*/
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struct login_info {
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struct passwd *user;
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char *from;
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};
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static int list_match(char *list, struct login_info *item,
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int (*match_fn)(char *, struct login_info *));
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static int user_match(char *tok, struct login_info *item);
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static int from_match(char *tok, struct login_info *item);
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static int string_match(char *tok, char *string);
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/* login_access - match username/group and host/tty with access control file */
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int login_access(struct passwd *user, char *from)
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{
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struct login_info item;
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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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char *foo;
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/*
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* Bundle up the arguments to avoid unnecessary clumsiness lateron.
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*/
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item.user = user;
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item.from = from;
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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")) != 0) {
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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((unsigned char)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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foo = NULL;
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if (!(perm = strtok_r(line, fs, &foo))
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|| !(users = strtok_r(NULL, fs, &foo))
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|| !(froms = strtok_r(NULL, fs, &foo))
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|| strtok_r(NULL, fs, &foo)) {
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syslog(LOG_ERR, "%s: line %d: bad field count",
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_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",
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_PATH_LOGACCESS,
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lineno);
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continue;
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}
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match = (list_match(froms, &item, from_match)
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&& list_match(users, &item, user_match));
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}
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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
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list_match(char *list,
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struct login_info *item,
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int (*match_fn)(char *, struct login_info *))
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{
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char *tok;
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int match = NO;
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char *foo = NULL;
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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_r(list, sep, &foo);
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tok != NULL;
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tok = strtok_r(NULL, sep, &foo)) {
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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)) != 0) /* 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_r(NULL, sep, &foo)) && strcasecmp(tok, "EXCEPT"))
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/* VOID */ ;
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if (tok == 0 || list_match(NULL, 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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/* myhostname - figure out local machine name */
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static char *myhostname(void)
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{
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static char name[MAXHOSTNAMELEN + 1] = "";
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if (name[0] == 0) {
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gethostname(name, sizeof(name));
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name[MAXHOSTNAMELEN] = 0;
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}
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return (name);
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}
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/* netgroup_match - match group against machine or user */
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static int netgroup_match(char *group, char *machine, char *user)
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{
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#ifdef HAVE_YP_GET_DEFAULT_DOMAIN
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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(char *tok, struct login_info *item)
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{
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char *string = item->user->pw_name;
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struct login_info fake_item;
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struct group *group;
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int i;
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char *at;
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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, if the
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* token is a group that contains the username, or if the token is the
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* name of the user's primary group.
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*/
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if ((at = strchr(tok + 1, '@')) != 0) { /* split user@host pattern */
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*at = 0;
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fake_item.from = myhostname();
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return (user_match(tok, item) && from_match(at + 1, &fake_item));
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} else 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)) != 0) { /* try group membership */
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if (item->user->pw_gid == group->gr_gid)
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return (YES);
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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(char *tok, struct login_info *item)
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{
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char *string = item->from;
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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(char *tok, 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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