/*
* 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.
*/
#if 0
#ifndef lint
static char sccsid[] = "%Z% %M% %I% %E% %U%";
#endif
#endif
#include <sys/cdefs.h>
#include <sys/types.h>
#include <sys/param.h>
#include <ctype.h>
#include <errno.h>
#include <grp.h>
#include <netdb.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include "pam_login_access.h"
/* Constants to be used in assignments only, not in comparisons... */
#define YES 1
#define NO 0
static int from_match(const char *, const char *, struct pam_login_access_options *);
static int list_match(char *, const char *,
int (*)(const char *, const char *,
struct pam_login_access_options *),
struct pam_login_access_options *);
static int netgroup_match(const char *, const char *, const char *);
static int string_match(const char *, const char *);
static int user_match(const char *, const char *, struct pam_login_access_options *);
static int group_match(const char *, const char *);
/* login_access - match username/group and host/tty with access control file */
int
login_access(const char *user, const char *from,
struct pam_login_access_options *login_access_opts)
{
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 */
const char *fieldsep = login_access_opts->fieldsep;
/*
* 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(login_access_opts->accessfile, "r")) != NULL) {
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",
login_access_opts->accessfile, 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, fieldsep))
|| !(users = strtok((char *) 0, fieldsep))
|| !(froms = strtok((char *) 0, fieldsep))
|| strtok((char *) 0, fieldsep)) {
syslog(LOG_ERR, "%s: line %d: bad field count", login_access_opts->accessfile,
lineno);
continue;
}
if (perm[0] != '+' && perm[0] != '-') {
syslog(LOG_ERR, "%s: line %d: bad first field", login_access_opts->accessfile,
lineno);
continue;
}
match = (list_match(froms, from, from_match, login_access_opts)
&& list_match(users, user, user_match, login_access_opts));
}
(void) fclose(fp);
} else if (errno != ENOENT) {
syslog(LOG_ERR, "cannot open %s: %m", login_access_opts->accessfile);
}
return (match == 0 || (line[0] == '+'));
}
/* list_match - match an item against a list of tokens with exceptions */
static int
list_match(char *list, const char *item,
int (*match_fn)(const char *, const char *, struct pam_login_access_options *),
struct pam_login_access_options *login_access_opts)
{
char *tok;
int match = NO;
const char *listsep = login_access_opts->listsep;
/*
* 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, listsep); tok != NULL; tok = strtok((char *) 0, listsep)) {
if (strcmp(tok, "EXCEPT") == 0) /* EXCEPT: give up */
break;
if ((match = (*match_fn)(tok, item, login_access_opts)) != 0) /* YES */
break;
}
/* Process exceptions to matches. */
if (match != NO) {
while ((tok = strtok((char *) 0, listsep)) && strcmp(tok, "EXCEPT")) {
/* VOID */ ;
}
if (tok == NULL ||
list_match((char *) 0, item, match_fn, login_access_opts) == NO) {
return (match);
}
}
return (NO);
}
/* netgroup_match - match group against machine or user */
static int
netgroup_match(const char *group, const char *machine, const char *user)
{
char domain[1024];
unsigned int i;
if (getdomainname(domain, sizeof(domain)) != 0 || *domain == '\0') {
syslog(LOG_ERR, "NIS netgroup support disabled: no NIS domain");
return (NO);
}
/* getdomainname() does not reliably terminate the string */
for (i = 0; i < sizeof(domain); ++i)
if (domain[i] == '\0')
break;
if (i == sizeof(domain)) {
syslog(LOG_ERR, "NIS netgroup support disabled: invalid NIS domain");
return (NO);
}
if (innetgr(group, machine, user, domain) == 1)
return (YES);
return (NO);
}
/* group_match - match a group against one token */
int
group_match(const char *tok, const char *username)
{
struct group *group;
struct passwd *passwd;
gid_t *grouplist;
int i, ret, ngroups = NGROUPS;
if ((passwd = getpwnam(username)) == NULL)
return (NO);
errno = 0;
if ((group = getgrnam(tok)) == NULL) {
if (errno != 0)
syslog(LOG_ERR, "getgrnam() failed for %s: %s", username, strerror(errno));
else
syslog(LOG_NOTICE, "group not found: %s", username);
return (NO);
}
if ((grouplist = calloc(ngroups, sizeof(gid_t))) == NULL) {
syslog(LOG_ERR, "cannot allocate memory for grouplist: %s", username);
return (NO);
}
ret = NO;
if (getgrouplist(username, passwd->pw_gid, grouplist, &ngroups) != 0)
syslog(LOG_ERR, "getgrouplist() failed for %s", username);
for (i = 0; i < ngroups; i++)
if (grouplist[i] == group->gr_gid)
ret = YES;
free(grouplist);
return (ret);
}
/* user_match - match a username against one token */
static int
user_match(const char *tok, const char *string,
struct pam_login_access_options *login_access_opts)
{
size_t stringlen;
char *grpstr;
int rc;
/*
* 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 (tok[0] == '(' && tok[(stringlen = strlen(&tok[1]))] == ')') { /* group */
if ((grpstr = strndup(&tok[1], stringlen - 1)) == NULL) {
syslog(LOG_ERR, "cannot allocate memory for %s", string);
return (NO);
}
rc = group_match(grpstr, string);
free(grpstr);
return (rc);
} else if (string_match(tok, string)) { /* ALL or exact match */
return (YES);
} else if (login_access_opts->defgroup == true) {/* try group membership */
return (group_match(tok, string));
}
return (NO);
}
/* from_match - match a host or tty against a list of tokens */
static int
from_match(const char *tok, const char *string,
struct pam_login_access_options *login_access_opts __unused)
{
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 (strcmp(tok, "LOCAL") == 0) { /* local: no dots */
if (strchr(string, '.') == NULL)
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(const char *tok, const 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 (strcmp(tok, "ALL") == 0) { /* all: always matches */
return (YES);
} else if (strcasecmp(tok, string) == 0) { /* try exact match */
return (YES);
}
return (NO);
}
plain