freebsd-dev/lib/libskey/skeyaccess.c
1995-06-11 19:33:05 +00:00

477 lines
12 KiB
C

/*
* Figure out if UNIX passwords are permitted for any combination of user
* name, group member, terminal port, host_name or network:
*
* Programmatic interface: skeyaccess(user, port, host, addr)
*
* All arguments are null-terminated strings. Specify a null character pointer
* where information is not available.
*
* When no address information is given this code performs the host (internet)
* address lookup itself. It rejects addresses that appear to belong to
* someone else.
*
* When compiled with -DPERMIT_CONSOLE always permits UNIX passwords with
* console logins, no matter what the configuration file says.
*
* To build a stand-alone test version, compile with -DTEST and run it off an
* skey.access file in the current directory:
*
* Command-line interface: ./skeyaccess user port [host_or_ip_addr]
*
* Errors are reported via syslogd.
*
* Author: Wietse Venema, Eindhoven University of Technology.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <grp.h>
#include <ctype.h>
#include <syslog.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/param.h>
#include "pathnames.h"
/*
* Token input with one-deep pushback.
*/
static char *prev_token = 0; /* push-back buffer */
static char *line_pointer = NULL;
static char *first_token();
static int line_number;
static void unget_token();
static char *get_token();
static char *need_token();
static char *need_internet_addr();
/*
* Various forms of token matching.
*/
#define match_host_name(l) match_token((l)->host_name)
#define match_port(l) match_token((l)->port)
#define match_user(l) match_token((l)->user)
static int match_internet_addr();
static int match_group();
static int match_token();
static int is_internet_addr();
static struct in_addr *convert_internet_addr();
static struct in_addr *lookup_internet_addr();
#define MAX_ADDR 32
#define PERMIT 1
#define DENY 0
#ifndef CONSOLE
#define CONSOLE "console"
#endif
struct login_info {
char *host_name; /* host name */
struct in_addr *internet_addr; /* null terminated list */
char *user; /* user name */
char *port; /* login port */
};
/* skeyaccess - find out if UNIX passwords are permitted */
int skeyaccess(user, port, host, addr)
char *user;
char *port;
char *host;
char *addr;
{
FILE *fp;
struct login_info login_info;
int result;
/*
* Assume no restriction on the use of UNIX passwords when the s/key
* acces table does not exist.
*/
if ((fp = fopen(_PATH_SKEYACCESS, "r")) == 0) {
#ifdef TEST
fprintf(stderr, "No file %s, thus no access control\n", _PATH_SKEYACCESS);
#endif
return (PERMIT);
}
/*
* Bundle up the arguments in a structure so we won't have to drag around
* boring long argument lists.
*
* Look up the host address when only the name is given. We try to reject
* addresses that belong to someone else.
*/
login_info.user = user;
login_info.port = port;
if (host != 0 && !is_internet_addr(host)) {
login_info.host_name = host;
} else {
login_info.host_name = 0;
}
if (addr != 0 && is_internet_addr(addr)) {
login_info.internet_addr = convert_internet_addr(addr);
} else if (host != 0) {
if (is_internet_addr(host)) {
login_info.internet_addr = convert_internet_addr(host);
} else {
login_info.internet_addr = lookup_internet_addr(host);
}
} else {
login_info.internet_addr = 0;
}
/*
* Print what we think the user wants us to do.
*/
#ifdef TEST
printf("port: %s\n", login_info.port);
printf("user: %s\n", login_info.user);
printf("host: %s\n", login_info.host_name ? login_info.host_name : "none");
printf("addr: ");
if (login_info.internet_addr == 0) {
printf("none\n");
} else {
int i;
for (i = 0; login_info.internet_addr[i].s_addr; i++)
printf("%s%s", login_info.internet_addr[i].s_addr == -1 ?
"(see error log)" : inet_ntoa(login_info.internet_addr[i]),
login_info.internet_addr[i + 1].s_addr ? " " : "\n");
}
#endif
result = _skeyaccess(fp, &login_info);
fclose(fp);
return (result);
}
/* _skeyaccess - find out if UNIX passwords are permitted */
int _skeyaccess(fp, login_info)
FILE *fp;
struct login_info *login_info;
{
char buf[BUFSIZ];
char *tok;
int match;
int permission;
#ifdef PERMIT_CONSOLE
if (login_info->port != 0 && strcasecmp(login_info->port, CONSOLE) == 0)
return (1);
#endif
/*
* Scan the s/key access table until we find an entry that matches. If no
* match is found, assume that UNIX passwords are disallowed.
*/
match = 0;
while (match == 0 && (tok = first_token(buf, sizeof(buf), fp))) {
if (strncasecmp(tok, "permit", 4) == 0) {
permission = PERMIT;
} else if (strncasecmp(tok, "deny", 4) == 0) {
permission = DENY;
} else {
syslog(LOG_ERR, "%s: line %d: bad permission: %s",
_PATH_SKEYACCESS, line_number, tok);
continue; /* error */
}
/*
* Process all conditions in this entry until we find one that fails.
*/
match = 1;
while (match != 0 && (tok = get_token())) {
if (strcasecmp(tok, "hostname") == 0) {
match = match_host_name(login_info);
} else if (strcasecmp(tok, "port") == 0) {
match = match_port(login_info);
} else if (strcasecmp(tok, "user") == 0) {
match = match_user(login_info);
} else if (strcasecmp(tok, "group") == 0) {
match = match_group(login_info);
} else if (strcasecmp(tok, "internet") == 0) {
match = match_internet_addr(login_info);
} else if (is_internet_addr(tok)) {
unget_token(tok);
match = match_internet_addr(login_info);
} else {
syslog(LOG_ERR, "%s: line %d: bad condition: %s",
_PATH_SKEYACCESS, line_number, tok);
match = 0;
}
}
}
return (match ? permission : DENY);
}
/* match_internet_addr - match internet network address */
static int match_internet_addr(login_info)
struct login_info *login_info;
{
char *tok;
long pattern;
long mask;
struct in_addr *addrp;
if (login_info->internet_addr == 0)
return (0);
if ((tok = need_internet_addr()) == 0)
return (0);
pattern = inet_addr(tok);
if ((tok = need_internet_addr()) == 0)
return (0);
mask = inet_addr(tok);
/*
* See if any of the addresses matches a pattern in the control file. We
* have already tried to drop addresses that belong to someone else.
*/
for (addrp = login_info->internet_addr; addrp->s_addr; addrp++)
if (addrp->s_addr != -1 && (addrp->s_addr & mask) == pattern)
return (1);
return (0);
}
/* match_group - match username against group */
static int match_group(login_info)
struct login_info *login_info;
{
struct group *group;
char *tok;
char **memp;
if ((tok = need_token()) && (group = getgrnam(tok))) {
for (memp = group->gr_mem; *memp; memp++)
if (strcmp(login_info->user, *memp) == 0)
return (1);
}
return (0); /* XXX endgrent() */
}
/* match_token - get and match token */
static int match_token(str)
char *str;
{
char *tok;
return (str && (tok = need_token()) && strcasecmp(str, tok) == 0);
}
/* first_token - read line and return first token */
static char *first_token(buf, len, fp)
char *buf;
int len;
FILE *fp;
{
char *cp;
prev_token = 0;
for (;;) {
if (fgets(buf, len, fp) == 0)
return (0);
line_number++;
buf[strcspn(buf, "\r\n#")] = 0;
#ifdef TEST
if (buf[0])
printf("rule: %s\n", buf);
#endif
line_pointer = buf;
while ((cp = strsep(&line_pointer, " \t")) != NULL && *cp == '\0')
;
if (cp != NULL)
return (cp);
}
}
/* unget_token - push back last token */
static void unget_token(cp)
char *cp;
{
prev_token = cp;
}
/* get_token - retrieve next token from buffer */
static char *get_token()
{
char *cp;
if (cp = prev_token) {
prev_token = 0;
} else {
while ((cp = strsep(&line_pointer, " \t")) != NULL && *cp == '\0')
;
}
return (cp);
}
/* need_token - complain if next token is not available */
static char *need_token()
{
char *cp;
if ((cp = get_token()) == 0)
syslog(LOG_ERR, "%s: line %d: premature end of rule",
_PATH_SKEYACCESS, line_number);
return (cp);
}
/* need_internet_addr - complain if next token is not an internet address */
static char *need_internet_addr()
{
char *cp;
if ((cp = get_token()) == 0) {
syslog(LOG_ERR, "%s: line %d: internet address expected",
_PATH_SKEYACCESS, line_number);
return (0);
} else if (!is_internet_addr(cp)) {
syslog(LOG_ERR, "%s: line %d: bad internet address: %s",
_PATH_SKEYACCESS, line_number, cp);
return (0);
} else {
return (cp);
}
}
/* is_internet_addr - determine if string is a dotted quad decimal address */
static int is_internet_addr(str)
char *str;
{
int in_run = 0;
int runs = 0;
/* Count the number of runs of characters between the dots. */
while (*str) {
if (*str == '.') {
in_run = 0;
} else {
if (!isdigit(*str))
return (0);
if (in_run == 0) {
in_run = 1;
runs++;
}
}
str++;
}
return (runs == 4);
}
/* lookup_internet_addr - look up internet addresses with extreme prejudice */
static struct in_addr *lookup_internet_addr(host)
char *host;
{
struct hostent *hp;
static struct in_addr list[MAX_ADDR + 1];
char buf[MAXHOSTNAMELEN + 1];
int length;
int i;
if ((hp = gethostbyname(host)) == 0 || hp->h_addrtype != AF_INET)
return (0);
/*
* Save a copy of the results before gethostbyaddr() clobbers them.
*/
for (i = 0; i < MAX_ADDR && hp->h_addr_list[i]; i++)
memcpy((char *) &list[i],
hp->h_addr_list[i], hp->h_length);
list[i].s_addr = 0;
strncpy(buf, hp->h_name, MAXHOSTNAMELEN);
buf[MAXHOSTNAMELEN] = 0;
length = hp->h_length;
/*
* Wipe addresses that appear to belong to someone else. We will get
* false alarms when when the hostname comes from DNS, while its
* addresses are listed under different names in local databases.
*/
#define NEQ(x,y) (strcasecmp((x),(y)) != 0)
#define NEQ3(x,y,n) (strncasecmp((x),(y), (n)) != 0)
while (--i >= 0) {
if ((hp = gethostbyaddr((char *) &list[i], length, AF_INET)) == 0) {
syslog(LOG_ERR, "address %s not registered for host %s",
inet_ntoa(list[i]), buf);
list[i].s_addr = -1;
}
if (NEQ(buf, hp->h_name) && NEQ3(buf, "localhost.", 10)) {
syslog(LOG_ERR, "address %s registered for host %s and %s",
inet_ntoa(list[i]), hp->h_name, buf);
list[i].s_addr = -1;
}
}
return (list);
}
/* convert_internet_addr - convert string to internet address */
static struct in_addr *convert_internet_addr(string)
char *string;
{
static struct in_addr list[2];
list[0].s_addr = inet_addr(string);
list[1].s_addr = 0;
return (list);
}
#ifdef TEST
main(argc, argv)
int argc;
char **argv;
{
struct hostent *hp;
char host[MAXHOSTNAMELEN + 1];
int verdict;
char *user;
char *port;
if (argc != 3 && argc != 4) {
fprintf(stderr, "usage: %s user port [host_or_ip_address]\n", argv[0]);
exit(0);
}
if (_PATH_SKEYACCESS[0] != '/')
printf("Warning: this program uses control file: %s\n", KEYACCESS);
openlog("login", LOG_PID, LOG_AUTH);
user = argv[1];
port = argv[2];
if (argv[3]) {
strncpy(host, (hp = gethostbyname(argv[3])) ?
hp->h_name : argv[3], MAXHOSTNAMELEN);
host[MAXHOSTNAMELEN] = 0;
}
verdict = skeyaccess(user, port, argv[3] ? host : (char *) 0, (char *) 0);
printf("UNIX passwords %spermitted\n", verdict ? "" : "NOT ");
return (0);
}
#endif