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